WorldWideScience

Sample records for transient outburst mechanisms

  1. MAXI J1659-152: The shortest orbital period black-hole transient in outburst

    DEFF Research Database (Denmark)

    Kuulkers, E.; Kouveliotou, C.; Belloni, T.

    2013-01-01

    MAXI J1659−152 is a bright X-ray transient black-hole candidate binary system discovered in September 2010. We report here on MAXI, RXTE, Swift, and XMM-Newton observations during its 2010/2011 outburst. We find that during the first one and a half week of the outburst the X-ray light curves disp...

  2. Black hole and neutron star soft X-ray transients: a hard X-ray view of their outbursts

    International Nuclear Information System (INIS)

    Yu, W.

    2004-01-01

    The RXTE public observations of the outbursts of black hole soft X-ray transients XTE J1550-564, XTE J1859+226, 4U 1630-47, XTE J1118+480, XTE J1650-500, and the neutron star soft X-ray transients 4U 1608-52, Aquila X-1, including a variable 'persistent' neutron star low mass X-ray binary 4U 1705-44, are summarized in this paper. The hard X-ray view of those outbursts, which is quite different from that of the soft X-ray band, suggests that there are several types of outbursts which result in different hard X-ray outburst profile - the outburst profiles are energy dependent. One type is the low/hard state outbursts, the other type is the outburst showing transitions from the low/hard state to the high/soft state, or to the intermediate or to the very high state. The later has an initial low/hard state, introducing the phenomena that the hard X-ray precedes the soft X-ray in the outburst rise. Such outbursts in XTE J1550-564, Aql X-1 and 4U 1705-44 support a two-accretion-flow model which involves one Keplerian disk flow and one sub-Keplerian flow for the initial outburst rise

  3. A new outburst of the recurrent neutron star transient SAX J1747.0-2853

    NARCIS (Netherlands)

    Brandt, S.; Chenevez, J.; Kuulkers, E.; Natalucci, L.; Fiocchi, M.T.; Tarana, A.; Shaw, S.; Beckmann, V.; Courvoisier, T.J.L.; Domingo, A.; Ebisawa, K.; Kretschmar, P.J.P.; Markwardt, C.; Oosterbroek, T.; Paizis, A.; Risquez, D.; Sanchez-Fernandez, C.; Wijnands, R.

    2007-01-01

    The recurrent transient neutron star system SAX J1747.0-2853 has in the past shown various outbursts with about 60 days duration. Recent observations with INTEGRAL reveal that SAX J1747.0-2853 shows increased activity which may mark the beginning of a new outburst. During the INTEGRAL Galactic Bulge

  4. Detection of X-ray spectral state transitions in mini-outbursts of black hole transient GRS 1739-278

    Science.gov (United States)

    Yan, Zhen; Yu, Wenfei

    2017-10-01

    We report the detection of the state transitions and hysteresis effect in the two mini-outbursts of the black hole (BH) transient GRS 1739-278 following its 2014 major outburst. The X-ray spectral evolutions in these two mini-outbursts are similar to the major outburst in spite of their peak luminosities and the outburst durations are one order of magnitude lower. We found L_hard{-to-soft} and Lpeak,soft of the mini-outbursts also follow the correlation previously found in other X-ray binaries. L_hard{-to-soft} of the mini-outbursts is still higher than that of the persistent BH binary Cyg X-1, which supports that there is a link between the maximum luminosity a source can reach in the hard state and the corresponding non-stationary accretion represented by substantial rate of change in the mass accretion rate during flares/outbursts. The detected luminosity range of these two mini-outbursts is roughly in 3.5 × 10-5 to 0.015 (D/7.5 kpc)2(M/8M⊙) LEdd. The X-ray spectra of other BH transients at such low luminosities are usually dominated by a power-law component, and an anti-correlation is observed between the photon index and the X-ray luminosity below 1 per cent LEdd. So, the detection of X-ray spectral state transitions indicates that the accretion flow evolution in these two mini-outbursts of GRS 1739-278 are different from other BH systems at such low-luminosity regime.

  5. Archival Investigation of Outburst Sites and Progenitors of Extragalactic Intermediate-Luminosity Mid-IR Transients

    Science.gov (United States)

    Bond, Howard

    2017-08-01

    Our team is using Spitzer in a long-term search for extragalactic mid-infrared (MIR) variable stars and transients-the SPIRITS project (SPitzer InfraRed Intensive Transients Survey). In this first exploration of luminous astrophysical transients in the infrared, we have discovered a puzzling new class. We call them SPRITEs: eSPecially Red Intermediate-luminosity Transient Events. They have maximum MIR luminosities between supernovae and classical novae, but are not detected in the optical to deep limits. To date, we have discovered more than 50 SPRITEs in galaxies out to 17 Mpc. In this Archival Research proposal, we request support in order to investigate the pre-eruption sites in HST images of some 3 dozen SPRITEs discovered to date, and an additional 2 dozen that we are likely to find until the end of Spitzer observing in late 2018. Our aims are (1) characterize the pre-outburst environments at HST resolution in the visible and near-IR, to understand the stellar populations, stellar ages and masses, and interstellar medium at the outburst sites; (2) search for progenitors; (3) help prepare the way for a better understanding of the nature of extragalactic IR transients that will be investigated by JWST.

  6. 1980 outburst of 4U 0115+63 (V635 Cassiopeiae)

    International Nuclear Information System (INIS)

    Kriss, G.A.; Cominsky, L.R.; Remillard, R.A.; Williams, G.; Thorstensen, J.R.

    1983-01-01

    Optical observations of the proposed Be companion star (V635 Cas) to the hard transient X-ray pulsar 4U 0115+63 have been used to predict the 1980 December X-ray outburst, thus confirming the identification. V635 Cas increased in brightness by 1.7 magnitudes over the three months preceding the X-ray outburst, and strong, variable Hα emission was always present. These results demonstrate for the first time that increased optical activity in the Be companion star can lead directly to a ''hard'' transient X-ray outburst. There is a delay of approx.60 days between the onset of optical activity and the X-ray outburst. This delay and the absence of orbital modulation of the 1980 X-ray outburst (or any of the previous X-ray outburst) rule out direct accretion from a stellar wind. We suggest that the delay represents the time for material near the X-ray source to form an accretion disk and move inward toward the neutron star surface, and we discuss the observational implications of this interpretation. Future observations of similar transient events may provide a firm basis for the study of accretion disk dynamics

  7. Physical Mechanism of Comet (and Asteroid) Outbursts: The Movie

    Science.gov (United States)

    Hartmann, W. K.

    2015-07-01

    A film made during impact experiments at NASA Ames illustrates a mechanism in which regolith can become gas charged and then erupt to create outbursts as observed on comets (and "asteroids" such as 2060 Chiron).

  8. Recurrent Outbursts Revealed in 3XMM J031820.8-663034

    Science.gov (United States)

    Zhao, Hai-Hui; Weng, Shan-Shan; Wang, Jun-Xian

    2018-06-01

    3XMM J031820.8-663034, first detected by ROSAT in NGC 1313, is one of a few known transient ultraluminous X-ray sources (ULXs). In this paper, we present decades of X-ray data of this source from ROSAT, XMM-Newton, Chandra, and the Neil Gehrels Swift Observatory. We find that its X-ray emission experienced four outbursts since 1992, with a typical recurrent time ∼1800 days, an outburst duration ∼240–300 days, and a nearly constant peak X-ray luminosity ∼1.5 × 1039 erg s‑1. The upper limit of X-ray luminosity at the quiescent state is ∼5.6 × 1036 erg s‑1, and the total energy radiated during one outburst is ∼1046 erg. The spectra at the high luminosity states can be described with an absorbed disk blackbody, and the disk temperature increases with the X-ray luminosity. We compare its outburst properties with other known transient ULXs including ESO 243-49 HLX-1. As its peak luminosity only marginally puts it in the category of ULXs, we also compare it with normal transient black hole binaries. Our results suggest that the source is powered by an accreting massive stellar-mass black hole, and the outbursts are triggered by the thermal-viscous instability.

  9. Cometary outbursts, a brief survey

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, D W [Sheffield Univ. (UK). Dept. of Physics

    1975-12-01

    Cometary outbursts, sudden increases in brightness which last for about a month, are still something of a mystery. The subject is treated under the following headings: the characteristics of outbursts (form, duration, mass loss and energy; probability of occurrence; distribution in the solar system; temporal periodicities in outbursts); possible production mechanisms for outbursts (pressure release from gas pockets; explosive radicals; amorphous ice; impact cratering by boulders; break-up of nucleus; nuclear crushing).

  10. Swift/BAT confirms the giant outburst of H 1417-624

    Science.gov (United States)

    Krimm, H. A.; Barthelmy, S. D.; Cummings, J. R.; Lien, A. Y.; Markwardt, C. B.; Palmer, D. M.; Sakamoto, T.; Stamatikos, M.; Ukwatta, T. N.

    2018-04-01

    The Swift/BAT transient monitor confirms the current outburst from the Be/X-ray binary pulsar, H 1417-624 ( = 2S 1417-624) (Nakajima et al., ATel #11479). In the BAT 15-50 keV energy band, the outburst began approximately on 20 March 2018 (MJD 57467) and the count rate has been steadily rising since that time.

  11. An X-ray view of the very faint black hole X-ray transient Swift J1357.2-0933 during its 2011 outburst

    NARCIS (Netherlands)

    Armas Padilla, M.; Wijnands, R.; Altamirano, D.; Méndez, M.; Miller, J. M.; Degenaar, N.

    We report on the X-ray spectral (using XMM-Newton data) and timing behaviour [using XMM-Newton and Rossi X-ray Timing Explorer (RXTE) data] of the very faint X-ray transient and black hole system Swift J1357.2-0933 during its 2011 outburst. The XMM-Newton X-ray spectrum of this source can be

  12. X-ray Observation of XTE J2012+381 during the 1998 Outburst

    Indian Academy of Sciences (India)

    The outburst of X-ray transient source XTE J2012+381 was detected by the RXTE All-Sky Monitor on 1998 May 24th. Following the outburst, X-ray observations of the source were made in the 2-18keV energy band with the Pointed Proportional Counters of the Indian X-ray Astronomy Experiment (IXAE) on-board the Indian ...

  13. THE EFFECT OF TRANSIENT ACCRETION ON THE SPIN-UP OF MILLISECOND PULSARS

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharyya, Sudip; Chakrabarty, Deepto, E-mail: sudip@tifr.res.in [Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Colaba, Mumbai 400005 (India)

    2017-01-20

    A millisecond pulsar is a neutron star that has been substantially spun up by accretion from a binary companion. A previously unrecognized factor governing the spin evolution of such pulsars is the crucial effect of nonsteady or transient accretion. We numerically compute the evolution of accreting neutron stars through a series of outburst and quiescent phases, considering the drastic variation of the accretion rate and the standard disk–magnetosphere interaction. We find that, for the same long-term average accretion rate, X-ray transients can spin up pulsars to rates several times higher than can persistent accretors, even when the spin-down due to electromagnetic radiation during quiescence is included. We also compute an analytical expression for the equilibrium spin frequency in transients, by taking spin equilibrium to mean that no net angular momentum is transferred to the neutron star in each outburst cycle. We find that the equilibrium spin rate for transients, which depends on the peak accretion rate during outbursts, can be much higher than that for persistent sources. This explains our numerical finding. This finding implies that any meaningful study of neutron star spin and magnetic field distributions requires the inclusion of the transient accretion effect, since most accreting neutron star sources are transients. Our finding also implies the existence of a submillisecond pulsar population, which is not observed. This may point to the need for a competing spin-down mechanism for the fastest-rotating accreting pulsars, such as gravitational radiation.

  14. Long-term photometric behaviour of outbursting AM CVn systems

    OpenAIRE

    Levitan, David; Groot, Paul J.; Prince, Thomas A.; Kulkarni, Shrinivas R.; Laher, Russ; Ofek, Eran O.; Sesar, Branimir; Surace, Jason

    2015-01-01

    The AM CVn systems are a class of He-rich, post-period minimum, semidetached, ultracompact binaries. Their long-term light curves have been poorly understood due to the few systems known and the long (hundreds of days) recurrence times between outbursts. We present combined photometric light curves from the Lincoln Near Earth Asteroid Research, Catalina Real-Time Transient Survey, and Palomar Transient Factory synoptic surveys to study the photometric variability of these systems over an almo...

  15. The Swift Supergiant Fast X-ray Transient Project

    Science.gov (United States)

    Romano, P.; Barthelmy, S.; Bozzo, E.; Burrows, D.; Ducci, L.; Esposito, P.; Evans, P.; Kennea, J.; Krimm, H.; Vercellone, S.

    2017-10-01

    We present the Swift Supergiant Fast X-ray Transients project, a systematic study of SFXTs and classical supergiant X-ray binaries (SGXBs) through efficient long-term monitoring of 17 sources including SFXTs and classical SGXBs across more than 4 orders of magnitude in X-ray luminosity on timescales from hundred seconds to years. We derived dynamic ranges, duty cycles, and luminosity distributions to highlight systematic differences that help discriminate between different theoretical models proposed to explain the differences between the wind accretion processes in SFXTs and classical SGXBs. Our follow-ups of the SFXT outbursts provide a steady advancement in the comprehension of the mechanisms triggering the high X-ray level emission of these sources. In particular, the observations of the outburst of the SFXT prototype IGR J17544-2619, when the source reached a peak X-ray luminosity of 3×10^{38} erg s^{-1}, challenged for the first time the maximum theoretical luminosity achievable by a wind-fed neutron star high mass X-ray binary. We propose that this giant outburst was due to the formation of a transient accretion disc around the compact object. We also created a catalogue of over 1000 BAT flares which we use to predict the observability and perspectives with future missions.

  16. Investigation of peeling-ballooning stability prior to transient outbursts accompanying transitions out of H-mode in DIII-D

    Energy Technology Data Exchange (ETDEWEB)

    Eldon, D., E-mail: deldon@princeton.edu [University of California San Diego, 9500 Gilman Dr., La Jolla, California 92093-0964 (United States); Princeton University, Princeton, New Jersey 08543 (United States); Boivin, R. L.; Groebner, R. J.; Osborne, T. H.; Snyder, P. B.; Turnbull, A. D.; Burrell, K. H. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Tynan, G. R.; Boedo, J. A. [University of California San Diego, 9500 Gilman Dr., La Jolla, California 92093-0964 (United States); Kolemen, E. [Princeton University, Princeton, New Jersey 08543 (United States); Schmitz, L. [University of California Los Angeles, Los Angeles, California 90095-7099 (United States); Wilson, H. R. [University of York, Heslington, York YO10 5DD (United Kingdom)

    2015-05-15

    The H-mode transport barrier allows confinement of roughly twice as much energy as in an L-mode plasma. Termination of H-mode necessarily requires release of this energy, and the timescale of that release is of critical importance for the lifetimes of plasma facing components in next step tokamaks such as ITER. H-L transition sequences in modern tokamaks often begin with a transient outburst which appears to be superficially similar to and has sometimes been referred to as a type-I edge localized mode (ELM). Type-I ELMs have been shown to be consistent with ideal peeling ballooning instability and are characterized by significant (up to ∼50%) reduction of pedestal height on short (∼1 ms) timescales. Knowing whether or not this type of instability is present during H-L back transitions will be important of planning for plasma ramp-down in ITER. This paper presents tests of pre-transition experimental data against ideal peeling-ballooning stability calculations with the ELITE code and supports those results with secondary experiments that together show that the transient associated with the H-L transition is not triggered by the same physics as are type-I ELMs.

  17. Properties of the Second Outburst of the Bursting Pulsar (GRO J1744-28) as Observed with BATSE

    Science.gov (United States)

    Woods, P.; Kouveliotou, C.; vanParadijs, J.; Briggs, M. S.; Wilson, C. A.; Deal, K. J.; Harmon, B. A.; Fishman, G. J.; Lewin, W. H.; Kommers, J.

    1998-01-01

    One year after its discovery, the Bursting Pulsar (GRO J1744-28) went into outburst again, displaying the hard X-ray bursts and pulsations that make this source unique. We report on Burst and Transient Source Experiment (BATSE) observations of both the persistent and burst emission for this second outburst and draw comparisons to the first. The second outburst was smaller than the first in both duration and peak luminosity. The persistent flux, burst peak flux and burst fluence were all reduced in amplitude by a factor approximately 1.7. Despite these differences, the average burst occurrence rate and average burst durations were roughly the same through each outburst. Similar to the first outburst, no spectral evolution was found within bursts and the parameter alpha was very small at the start of the outburst (alpha = 2.1 +/- 1.7 on 1996 December 2). Although no spectral evolution was found within individual bursts, we find evidence for a small (20%) variation of the spectral temperature during the course of the second outburst.

  18. Orbital Light Curves of UU Aquarii in Stunted Outburst

    Science.gov (United States)

    Robertson, J. W.; Honeycutt, R. K.; Henden, A. A.; Campbell, R. T.

    2018-02-01

    Stunted outbursts are ∼0.ͫ6 eruptions, typically lasting 5–10 days, which are found in some novalike cataclysmic variables, including UU Aqr. The mechanism responsible for stunted outbursts is uncertain but is likely related to an accretion disk instability or to variations in the mass transfer rate. A campaign to monitor the eclipse light curves in UU Aqr has been conducted in order to detect any light curve distortions due to the appearance of a hot spot on the disk at the location of the impact point of the accretion stream. If stunted outbursts are due to a temporary mass transfer enhancement, then predictable deformations of the orbital light curve are expected to occur during such outbursts. This study used 156 eclipses on 135 nights during the years 2000–2012. During this interval, random samples found the system to be in stunted outbursts 4%–5% of the time, yielding ∼7 eclipses obtained during some stage of stunted outburst. About half of the eclipses obtained during stunted outbursts showed clear evidence for hot spot enhancement, providing strong evidence that the stunted outbursts in UU Aqr are associated with mass transfer variations. The other half of the eclipses during stunted outburst showed little or no evidence for hot spot enhancement. Furthermore, there were no systematic changes in the hot spot signature as stunted outbursts progressed. Therefore, we have tentatively attributed the changes in hot spot visibility during stunted outburst to random blobby accretion, which likely further modulates the strength of the accretion stream on orbital timescales.

  19. X-ray Outburst in Mira A

    OpenAIRE

    Karovska, M.; Schlegel, E.; Hack, W.; Wood, B.

    2005-01-01

    We report here the Chandra ACIS-S detection of a bright soft X-ray transient in the Mira AB interacting symbiotic-like binary. We resolved the system for the first time in the X-rays. Using Chandra and HST images we determined that the unprecedented outburst is likely associated with the cool AGB star (Mira A), the prototype of Mira-type variables. X-rays have never before been detected from an AGB star, and the recent activity signals that the system is undergoing dramatic changes. The total...

  20. Multidimensional Simulations of Colliding Outbursts from very Massive Stars

    Science.gov (United States)

    Chen, Ke-Jung; Woosley, Stan

    2015-08-01

    Massive stars that end their lives with helium cores in the range of 35 to 65 solar masses are known to produce repeated thermonuclear outbursts due to a recurring pair-instability. In some of these events, solar masses of material are ejected in repeated outbursts of several times 1050 erg each. Such models can be used to explain the strong mass loss rates at the last moment before the massive stars die. Collisions between these shells can sometimes produce very luminous transients. Previous 1D studies of these events produce thin,high-density shells as one ejection plows into another. We present the first multidimensional simulations of these collisions, we show that the development of a Rayleigh-Taylor instability truncates the growth of the high density spike and drives mixing between the shells.

  1. Different Accretion Heating of the Neutron Star Crust during Multiple Outbursts in MAXI J0556–332

    Science.gov (United States)

    Parikh, Aastha S.; Homan, Jeroen; Wijnands, Rudy; Ootes, Laura; Page, Dany; Altamirano, Diego; Degenaar, Nathalie; Brown, Edward F.; Cackett, Edward; Cumming, Andrew; Deibel, Alex; Fridriksson, Joel K.; Lin, Dacheng; Linares, Manuel; Miller, Jon M.

    2017-12-01

    The transient neutron star (NS) low-mass X-ray binary MAXI J0556‑332 provides a rare opportunity to study NS crust heating and subsequent cooling for multiple outbursts of the same source. We examine MAXI, Swift, Chandra, and XMM-Newton data of MAXI J0556‑332 obtained during and after three accretion outbursts of different durations and brightnesses. We report on new data obtained after outburst III. The source has been tracked up to ∼1800 days after the end of outburst I. Outburst I heated the crust strongly, but no significant reheating was observed during outburst II. Cooling from ∼333 eV to ∼146 eV was observed during the first ∼1200 days. Outburst III reheated the crust up to ∼167 eV, after which the crust cooled again to ∼131 eV in ∼350 days. We model the thermal evolution of the crust and find that this source required a different strength and depth of shallow heating during each of the three outbursts. The shallow heating released during outburst I was ∼17 MeV nucleon‑1 and outburst III required ∼0.3 MeV nucleon‑1. These cooling observations could not be explained without shallow heating. The shallow heating for outburst II was not well constrained and could vary from ∼0 to 2.2 MeV nucleon‑1, i.e., this outburst could in principle be explained without invoking shallow heating. We discuss the nature of the shallow heating and why it may occur at different strengths and depths during different outbursts.

  2. Properties of the Second Outburst of the Bursting Pulsar (GRO J1744-28) as Observed with BASTE

    Science.gov (United States)

    Woods, Peter M.; Kouveliotou, Chryssa; VanParadus, Jan; Briggs, Michael S.; Wilson, C. A.; Deal, Kim; Harmon, B. A.; Fishman, G. J.; Lewin, W. H. G.; Kommers, J.

    1999-01-01

    One year after its discovery, the Bursting Pulsar (GRO J1744-28) went into outburst again, displaying the hard X-ray bursts and pulsations that make this source unique. We report on BATSE (Burst and Transient Source Experiment) observations of both the persistent and burst emission for this second outburst and draw comparisons with the first. The second outburst was smaller than the first in both duration and peak luminosity. The persistent flux, burst peak flux, and burst fluence were all reduced in amplitude by a factor of approximately 1.7. Despite these differences, the two outbursts were very similar with respect to the burst occurrence rate, the durations and spectra of bursts, the absence of spectral evolution during bursts, and the evolution of the ratio alpha of average persistent to burst luminosity. Although no spectral evolution was found within individual bursts, we find evidence for a small (20%) variation of the spectral temperature during the course of the second outburst.

  3. GBM Observations of Be X-Ray Binary Outbursts

    Science.gov (United States)

    Wilson-Hodge, Colleen A.; Finger, M. H.; Jenke, P. A.

    2014-01-01

    Since 2008 we have been monitoring accreting pulsars using the Gamma ray Burst Monitor (GBM) on Fermi. This monitoring program includes daily blind full sky searches for previously unknown or previously quiescent pulsars and source specific analysis to track the frequency evolution of all detected pulsars. To date we have detected outbursts from 23 transient accreting pulsars, including 21 confirmed or likely Be/X-ray binaries. I will describe our techniques and highlight results for selected pulsars.

  4. Evolution of the 1984 outburst of the transient X-ray source 4U 1630 - 47

    International Nuclear Information System (INIS)

    Parmar, A.N.; Stella, L.; White, N.E.

    1986-01-01

    The results of a series of EXOSAT observations of the X-ray transient 4U 1630 - 47 during an outburst in 1984 are presented. The source decayed over an interval of about 100 days from a maximum 1-50 keV luminosity of about 2.8 x 10 to the 38th to about 4 x 10 to the 36th erg/s (for an assumed distance of 10 kpc). The 1-50 keV spectrum was best represented by a soft Wien-like spectrum with a temperature about 1 keV and a high-energy power-law tail. The relative contribution of the soft component to that of the high-energy power law decreased by atleast a factor of about 2 as the overall luminosity decreased. When the source was at its maximum observed luminosity, short time scale 7 percent intensity variations (1-7 keV) were seen with a characteristic time scale of about 20 s. The shortest time scale variability detected was about 50 ms. A 10-arcsec position obtained using an imaging telescope excludes a previously suggested optical counterpart. The spectral properties of 4U 1630 - 47 are reminiscent of those of the black hole candidate Cyg X-1 when it evolves from a high to a low state. 28 references

  5. 2014–2015 MULTIPLE OUTBURSTS OF 15P/FINLAY

    International Nuclear Information System (INIS)

    Ishiguro, Masateru; Kwon, Yuna Grace; Kim, Yoonyoung; Lee, Myung Gyoon; Kuroda, Daisuke; Yanagisawa, Kenshi; Hanayama, Hidekazu; Miyaji, Takeshi; Watanabe, Makoto; Akitaya, Hiroshi; Kawabata, Koji; Itoh, Ryosuke; Nakaoka, Tatsuya; Yoshida, Michitoshi; Imai, Masataka; Sarugaku, Yuki; Ohta, Kouji; Kawai, Nobuyuki; Fukushima, Hideo; Honda, Satoshi

    2016-01-01

    Multiple outbursts of a Jupiter-family comet (JFC), 15P/Finlay, occurred from late 2014 to early 2015. We conducted an observation of the comet after the first outburst and subsequently witnessed another outburst on 2015 January 15.6–15.7. The gas, consisting mostly of C 2 and CN, and dust particles expanded at speeds of 1110 ± 180 m s −1 and 570 ± 40 m s −1 at a heliocentric distance of 1.0 au. We estimated the maximum ratio of solar radiation pressure with respect to the solar gravity β max  = 1.6 ± 0.2, which is consistent with porous dust particles composed of silicates and organics. We found that 10 8 –10 9 kg of dust particles (assumed to be 0.3 μ m–1 mm) were ejected through each outburst. Although the total mass is three orders of magnitude smaller than that of the 17P/Holmes event observed in 2007, the kinetic energy per unit mass (10 4 J kg −1 ) is equivalent to the estimated values of 17P/Holmes and 332P/2010 V1 (Ikeya–Murakami), suggesting that the outbursts were caused by a similar physical mechanism. From a survey of cometary outbursts on the basis of voluntary reports, we conjecture that 15P/Finlay-class outbursts occur >1.5 times annually and inject dust particles from JFCs and Encke-type comets into interplanetary space at a rate of ∼10 kg s −1 or more.

  6. The inter-outburst behavior of cataclysmic variables

    International Nuclear Information System (INIS)

    Szkody, P.; Mattei, J.A.; Waagen, E.O.; Stablein, C.

    1990-01-01

    Existing International Ultraviolet Explorer (IUE) and American Association of Variable Star Observers (AAVSO) archive data was used to accomplish a large scale study of what happens to the ultraviolet flux of accretion disk systems during the quiescent intervals between outbursts and how it relates to the preceding outburst characteristics of amplitude and width. The data sample involved multiple IUE observations for 16 dwarf novae and 8 novae along with existing optical coverage. Results indicate that most systems show correlated ultraviolet (UV) flux behavior with interoutburst phase, with 60 percent of the dwarf novae and 50 percent of the novae having decreasing flux trends while 33 percent of the dwarf novae and 38 percent of the novae show rising UV flux during the quiescent interval. All of the dwarf novae with decreasing UV fluxes at 1475A have orbital periods longer than 4.4 hours, while all (except BV Cen) with flat or rising fluxes at 1475A have orbital periods less than two hours. There are not widespread correlations of the UV fluxes with the amplitude of the preceding outburst and no correlations with the width of the outburst. From a small sample (7) that have relatively large quiescent V magnitude changes between the IUE observations, most show a strong correlation between the UV and optical continuum. Interpretation of the results is complicated by not being able to determine how much the white dwarf contributes to the ultraviolet flux. However, it is now evident that noticeable changes are occurring in the hot zones in accreting systems long after the outburst, and not only for systems that are dominated by the white dwarf. Whether these differences are due to different outburst mechanisms or to changes on white dwarfs which provide varying contributions to the UV flux remains to be determined

  7. Transient Exciplex Formation Electron Transfer Mechanism

    Directory of Open Access Journals (Sweden)

    Michael G. Kuzmin

    2011-01-01

    Full Text Available Transient exciplex formation mechanism of excited-state electron transfer reactions is analyzed in terms of experimental data on thermodynamics and kinetics of exciplex formation and decay. Experimental profiles of free energy, enthalpy, and entropy for transient exciplex formation and decay are considered for several electron transfer reactions in various solvents. Strong electronic coupling in contact pairs of reactants causes substantial decrease of activation energy relative to that for conventional long-range ET mechanism, especially for endergonic reactions, and provides the possibility for medium reorganization concatenated to gradual charge shift in contrast to conventional preliminary medium and reactants reorganization. Experimental criteria for transient exciplex formation (concatenated mechanism of excited-state electron transfer are considered. Available experimental data show that this mechanism dominates for endergonic ET reactions and provides a natural explanation for a lot of known paradoxes of ET reactions.

  8. Radio outbursts in extragalactic sources

    International Nuclear Information System (INIS)

    Kinzel, W.M.

    1989-01-01

    Three aspects of the flux density variability of extragalactic radio sources were examined: millimeter wavelength short timescale variability, the spectral evolution of outbursts, and whether the outbursts are periodically spaced. Observations of extragalactic radio sources were conducted using the Five College Radio Astronomy Observatory between January and June 1985 at 88.2 GHz and during June and July 1985 at 40.0 GHz. Many of the sources exhibited significant flux density variations during the observing span. In addition, the most rapid variations observed were comparable with those reported in previous works. Two sources, 0355+50 and OJ287, both exhibited outbursts whose rise and fall timescales were less than a month. An anomalous flux density dropout was observed in 3C446 and was interpreted as an occultation event. Data at five frequencies between 2.7 and 89.6 GHz from the Dent-Balonek monitoring program were used to investigate the spectral evolution of eight outbursts. Outburst profile fitting was used to deconvolve the individual outbursts from one another at each frequency. The fit profiles were used to generate multiple epoch spectra to investigate the evolution of the outbursts. A phase residual minimization method was used to examine four sources for periodic behavior

  9. A self-regulating braking mechanism in black-hole X-ray binaries

    International Nuclear Information System (INIS)

    Meyer, F.; Meyer-Hofmeister, E.

    2001-01-01

    The outbursts of black hole X-ray transients can be understood as caused by a limit cycle instability in the accretion disk, similar to dwarf nova outbursts. For adequately low mass overflow rates from the companion star long outburst recurrence times are expected. Buth the fact that we find predominantly long recurrence times or that only one X-ray nova outburst was detected at all poses a problem. The question arises whether any braking mechanism could act in a way that long recurrence times are favoured. We suggest that a circumbinary disk exists and brakes the orbital motion of the binary stars by tidal interaction. The irradiation during an outburst leads to mass loss by winds from the circumbinary disk, relieving the braking force until the removed matter is refilled by diffusion from outer parts. We show that this reduction of braking will self-adjust the mass transfer to the marginal rate that gives long recurrence times. (orig.)

  10. 2014–2015 MULTIPLE OUTBURSTS OF 15P/FINLAY

    Energy Technology Data Exchange (ETDEWEB)

    Ishiguro, Masateru; Kwon, Yuna Grace; Kim, Yoonyoung; Lee, Myung Gyoon [Department of Physics and Astronomy, Seoul National University, Gwanak, Seoul 151-742 (Korea, Republic of); Kuroda, Daisuke; Yanagisawa, Kenshi [Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, Asakuchi, Okayama 719-0232 (Japan); Hanayama, Hidekazu; Miyaji, Takeshi [Ishigakijima Astronomical Observatory, National Astronomical Observatory of Japan, 1024-1 Arakawa, Ishigaki, Okinawa 907-0024 (Japan); Watanabe, Makoto [Department of Applied Physics, Faculty of Science, Okayama University of Science, 1-1 Ridai-cho, Okayama-si, Okayama 700-0005 (Japan); Akitaya, Hiroshi; Kawabata, Koji; Itoh, Ryosuke; Nakaoka, Tatsuya; Yoshida, Michitoshi [Hiroshima Astrophysical Science Center, Hiroshima University, Higashihiroshima, Hiroshima 739-8526 (Japan); Imai, Masataka [Department of Cosmosciences, Graduate School of Science, Hokkaido University, Kita-ku, Sapporo 060-0810 (Japan); Sarugaku, Yuki [Kiso Observatory, Institute of Astronomy, Graduate School of Science, The University of Tokyo, Mitake, Kiso-machi, Kiso, Nagano, 397-0101 (Japan); Ohta, Kouji [Department of Astronomy, Kyoto University, Kyoto 606-8502 (Japan); Kawai, Nobuyuki [Department of Physics, Tokyo Institute of Technology 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan); Fukushima, Hideo [National Astronomical Observatory of Japan, Mitaka, Tokyo, 181-8588 (Japan); Honda, Satoshi, E-mail: ishiguro@astro.snu.ac.kr [Nishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyogo, Sayo, Hyogo 679-5313 (Japan); and others

    2016-12-01

    Multiple outbursts of a Jupiter-family comet (JFC), 15P/Finlay, occurred from late 2014 to early 2015. We conducted an observation of the comet after the first outburst and subsequently witnessed another outburst on 2015 January 15.6–15.7. The gas, consisting mostly of C{sub 2} and CN, and dust particles expanded at speeds of 1110 ± 180 m s{sup −1} and 570 ± 40 m s{sup −1} at a heliocentric distance of 1.0 au. We estimated the maximum ratio of solar radiation pressure with respect to the solar gravity β {sub max} = 1.6 ± 0.2, which is consistent with porous dust particles composed of silicates and organics. We found that 10{sup 8}–10{sup 9} kg of dust particles (assumed to be 0.3 μ m–1 mm) were ejected through each outburst. Although the total mass is three orders of magnitude smaller than that of the 17P/Holmes event observed in 2007, the kinetic energy per unit mass (10{sup 4} J kg{sup −1}) is equivalent to the estimated values of 17P/Holmes and 332P/2010 V1 (Ikeya–Murakami), suggesting that the outbursts were caused by a similar physical mechanism. From a survey of cometary outbursts on the basis of voluntary reports, we conjecture that 15P/Finlay-class outbursts occur >1.5 times annually and inject dust particles from JFCs and Encke-type comets into interplanetary space at a rate of ∼10 kg s{sup −1} or more.

  11. X-ray outbursts and high-state episodes of HETE J1900.1-2455

    Science.gov (United States)

    Šimon, Vojtěch

    2018-06-01

    HETE J1900.1-2455 is an ultra-compact low-mass X-ray binary that underwent a long-lasting (about 10 yr) active state. The analysis presented here of its activity uses the observations of RXTE/ASM, Swift/BAT, and ISS/MAXI for investigating this active state and the relation of time evolution of fluxes in the hard and medium X-ray bands. We show that the variations of the flux of HETE J1900.1-2455 on the time-scales of days and weeks have the form both of the outbursts and occasional high-state episodes. These outbursts are accompanied by the large changes of the hardness of the spectrum in the surroundings of the peaks of their soft X-ray flux. The very strong peaks of these outbursts occur in the soft X-ray band (2-4 keV) and are accompanied by a large depression in the 15-50 keV band flux. We interpret these events as an occasional occurrence of a thermal-viscous instability of the accretion disc that gives rise to the outbursts similar to those in the soft X-ray transients. On the other hand, the 2-4 and the 15-50 keV band fluxes are mutually correlated in the high-state episodes, much longer than the outbursts. In the interpretation, the episodes of the X-ray high states of HETE J1900.1-2455 during the active state bear some analogy with the standstills in the Z Cam type of cataclysmic variables.

  12. Discovery of the third transient X-ray binary in the galactic globular cluster Terzan 5

    Energy Technology Data Exchange (ETDEWEB)

    Bahramian, Arash; Heinke, Craig O.; Sivakoff, Gregory R.; Gladstone, Jeanette C. [Department of Physics, University of Alberta, CCIS 4-183, Edmonton, AB T6G 2E1 (Canada); Altamirano, Diego; Wijnands, Rudy [Astronomical Institute " Anton Pannekoek," University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Homan, Jeroen [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 70 Vassar Street, Cambridge, MA 02139 (United States); Linares, Manuel [Instituto de Astrofísica de Canarias, c/Vía Láctea s/n, E-38205 La Laguna, Tenerife (Spain); Pooley, David [Department of Physics, Sam Houston State University, Huntsville, TX 77341 (United States); Degenaar, Nathalie, E-mail: bahramia@ualberta.ca [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States)

    2014-01-10

    We report and study the outburst of a new transient X-ray binary (XRB) in Terzan 5, the third detected in this globular cluster, Swift J174805.3-244637 or Terzan 5 X-3. We find clear spectral hardening in Swift/XRT data during the outburst rise to the hard state, thanks to our early coverage (starting at L{sub X} ∼ 4 × 10{sup 34} erg s{sup –1}) of the outburst. This hardening appears to be due to the decline in relative strength of a soft thermal component from the surface of the neutron star (NS) during the rise. We identify a Type I X-ray burst in Swift/XRT data with a long (16 s) decay time, indicative of hydrogen burning on the surface of the NS. We use Swift/BAT, MAXI/GSC, Chandra/ACIS, and Swift/XRT data to study the spectral changes during the outburst, identifying a clear hard-to-soft state transition. We use a Chandra/ACIS observation during outburst to identify the transient's position. Seven archival Chandra/ACIS observations show evidence for variations in Terzan 5 X-3's nonthermal component but not the thermal component during quiescence. The inferred long-term time-averaged mass accretion rate, from the quiescent thermal luminosity, suggests that if this outburst is typical and only slow cooling processes are active in the NS core, such outbursts should recur every ∼10 yr.

  13. Outbursts of symbiotic novae

    International Nuclear Information System (INIS)

    Kenyon, S.J.; Truran, J.W.

    1983-01-01

    We discuss possible conditions under which thermonuclear burning episodes in the hydrogen-rich envelopes of accreting white dwarfs give rise to outbursts similar in nature to those observed in the symbiotic stars AG Peg, RT Ser, RR Tel, AS 239, V1016 Cyg, V1329 Cyg, and HM Sge. In principle, thermonuclear runaways involving low-luminosity white dwarfs accreting matter at low rates produce configurations that evolve into A--F supergiants at maximum visual light and which resemble the outbursts of RR Tel, RT Ser, and AG peg. Very weak, nondegenerage hydrogen shell flashes on white dwarfs accreting matter at high rates (M> or approx. =10 -8 M/sub sun/ yr -1 ) do not produce cool supergiants at maximum, and may explain the outbursts in V1016 Cyg, V1329 Cyg, and HM Sge. The low accretion rates demanded for systems developing strong hydrogen shell flashes on low-luminsoity white dwarfs are not compatible with observations of ''normal'' quiescent symbiotic stars. The extremely slow outbursts of symbiotic novae appear to be typical of accreting white dwarfs in wide binaries, which suggests that the outbursts of classical novae may be accelerated by the interaction of the expanding white dwarf envelope with its close binary companion

  14. Fuel cladding mechanical properties for transient analysis

    International Nuclear Information System (INIS)

    Johnson, G.D.; Hunter, C.W.; Hanson, J.E.

    1976-01-01

    Out-of-pile simulated transient tests have been conducted on irradiated fast-reactor fuel pin cladding specimens at heating rates of 10 0 F/s (5.6 0 K/s) and 200 0 F/s (111 0 K/s) to generate mechanical property information for use in describing cladding behavior during off-normal events. Mechanical property data were then analyzed, applying the Larson-Miller Parameter to the effects of heating rate and neutron fluence. Data from simulated transient tests on TREAT-tested fuel pins demonstrate that Plant Protective System termination of 3$/s transients prevents significant damage to cladding. The breach opening produced during simulated transient testing is shown to decrease in size with increasing neutron fluence

  15. 100y DASCH Search for historical outbursts of Black Hole Low Mass X-ray Binaries

    Science.gov (United States)

    Grindlay, Jonathan E.; Miller, George; Gomez, Sebastian

    2018-01-01

    Black Hole Low mass X-ray binaries (BH-LMXBs) are all transients, although several (e.g. GRS1915+109 and GX339-4) are quasi-persistent. All of the now 22 dynamically confirmed BH-LMXBs were discovered by their luminous outbursts, reaching Lx ~10^37 ergs/s, with outburst durations of typically ~1-3 months. These systems then (with few exceptions) return to a deep quiescent state, with Lx reduced by factors ~10^5-6 and hard X-ray spectra. The X-ray outbursts are accompanied by optical outbursts (if not absorbed by Galactic extinction) with ~6-9 magnitude increases and similar lightcurve shapes and durations as the X-ray (discovery) outburst. Prior to this work, only 3 BH-LMXBs have had historical (before the X-ray discovery) outbursts found in the archival data: A0620-00, the first BH-LMXB to be so identified, V404 Cyg (discoverd as "Nova Cyg" in 1938 and regarded as a classical nova), and V4641-Sgr which was given its variable star name when first noted in 1975. We report on the historical outbursts now discovered from the DASCH (Digital Access to a Sky Century @ Harvard) data from scanning and digitizing the now ~210,000 glass plates in the northern Galactic Hemisphere. This was one of the primary motivations for the DASCH project: to use the detection (or lack threof) of historic outbursts to measure or constrain the Duty Cycle of the accreting black holes in these systems. This, in turn, allows the total population of BH-LMXBs to be estimated and compared with that for the very similar systems containing neutron stars as the accretor (NS-LMXBs). Whereas the ratio of BHs/NSs from stellar evolution and IMFs is expected to be <<1, the DASCH results on half the sky point to an excess of BH-LMXBs. This must constrain the formation process for these systems, of importance for understanding both BH formation and compact binary evolution.

  16. Outbursts in Symbiotic Binaries

    Science.gov (United States)

    Sonneborn, George (Technical Monitor); Kenyon, Scott J.

    2004-01-01

    Two models have been proposed for the outbursts of symbiotic stars. In the thermonuclear model, outbursts begin when the hydrogen burning shell of a hot white dwarf reaches a critical mass. After a rapid increase in the luminosity and effective temperature, the white dwarf evolves at constant luminosity to lower effective temperatures, remains at optical maximum for several years, and then returns to quiescence along a white dwarf cooling curve. In disk instability models, the brightness rises when the accretion rate from the disk onto the central white dwarf abruptly increases by factors of 5-20. After a few month to several year period at maximum, both the luminosity and the effective temperature of the disk decline as the system returns to quiescence. If most symbiotic stars undergo thermonuclear eruptions, then symbiotics are probably poor candidates for type I supernovae. However, they can then provide approx. 10% of the material which stars recycle back into the interstellar medium. If disk instabilities are the dominant eruption mechanism, symbiotics are promising type Ia candidates but recycle less material into the interstellar medium.

  17. Analysis of transient fuel failure mechanisms: selected ANL programs

    International Nuclear Information System (INIS)

    Deitrich, L.W.

    1975-01-01

    Analytical programs at Argonne National Laboratory related to fuel pin failure mechanisms in fast-reactor accident transients are described. The studies include transient fuel pin mechanics, mechanics of unclad fuel, and mechanical effects concerning potential fuel failure propagation. (U.S.).

  18. Comet 29P/SW1 outburst

    Science.gov (United States)

    Trigo-Rodriguez, Josep M.

    2008-10-01

    The present outburst experienced by this Centaur (#IAUC 8978) is the brightest detected since September 2004 [for more details see Trigo-Rodriguez et al. (2008) A&A485, pp. 599-606]. In the previously reported work the outburst frequency was established in 7.3 outbursts/year, typically reaching a +13 maximum magnitude or less.

  19. The Correlation between Hard X-Ray Peak Flux and Soft X-Ray Peak Flux in the Outburst Rise of Low-Mass X-Ray Binaries

    NARCIS (Netherlands)

    Yu, W.; van der Klis, M.; Fender, R.P.

    2004-01-01

    We have analyzed Rossi X-Ray Timing Explorer pointed observations of the outbursts of black hole and neutron star soft X-ray transients in which an initial low/hard state, or ``island'' state, followed by a transition to a softer state was observed. In three sources-the black hole transient XTE

  20. THE SWIFT/BAT HARD X-RAY TRANSIENT MONITOR

    Energy Technology Data Exchange (ETDEWEB)

    Krimm, H. A.; Holland, S. T.; Corbet, R. H. D.; Pearlman, A. B.; Baumgartner, W. H.; Cummings, J. R. [Center for Research and Exploration in Space Science and Technology (CRESST) and NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Romano, P. [INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Via U. La Malfa 153, I-90146 Palermo (Italy); Kennea, J. A. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Bloom, J. S. [Department of Astronomy, University of California, Berkeley, Berkeley, CA 94720-3411 (United States); Barthelmy, S. D.; Gehrels, N.; Lien, A. Y.; Markwardt, C. B.; Ukwatta, T. N. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Palmer, D. M. [Los Alamos National Laboratory, B244, Los Alamos, NM 87545 (United States); Sakamoto, T. [Department of Physics and Mathematics, College of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara-shi, Kanagawa 252-5258 (Japan); Stamatikos, M. [Department of Physics and Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH 43210 (United States)

    2013-11-01

    The Swift/Burst Alert Telescope (BAT) hard X-ray transient monitor provides near real-time coverage of the X-ray sky in the energy range 15-50 keV. The BAT observes 88% of the sky each day with a detection sensitivity of 5.3 mCrab for a full-day observation and a time resolution as fine as 64 s. The three main purposes of the monitor are (1) the discovery of new transient X-ray sources, (2) the detection of outbursts or other changes in the flux of known X-ray sources, and (3) the generation of light curves of more than 900 sources spanning over eight years. The primary interface for the BAT transient monitor is a public Web site. Between 2005 February 12 and 2013 April 30, 245 sources have been detected in the monitor, 146 of them persistent and 99 detected only in outburst. Among these sources, 17 were previously unknown and were discovered in the transient monitor. In this paper, we discuss the methodology and the data processing and filtering for the BAT transient monitor and review its sensitivity and exposure. We provide a summary of the source detections and classify them according to the variability of their light curves. Finally, we review all new BAT monitor discoveries. For the new sources that are previously unpublished, we present basic data analysis and interpretations.

  1. The Swift/BAT Hard X-ray Transient Monitor

    Science.gov (United States)

    Krimm, H. A.; Holland, S. T.; Corbet, R.H.D.; Pearlman, A. B.; Romano, P.; Kennea, J. A.; Bloom, J. S.; Barthelmy, S. D.; Baumgartner, W. H.; Cummings, J. R.; hide

    2013-01-01

    The Swift/Burst Alert Telescope (BAT) hard X-ray transient monitor provides near real-time coverage of the X-ray sky in the energy range 15-50 keV. The BAT observes 88% of the sky each day with a detection sensitivity of 5.3 mCrab for a full-day observation and a time resolution as ne as 64 seconds. The three main purposes of the monitor are (1) the discovery of new transient X-ray sources, (2) the detection of outbursts or other changes in the ux of known X-ray sources, and (3) the generation of light curves of more than 900 sources spanning over eight years. The primary interface for the BAT transient monitor is a public web page. Since 2005 February, 242 sources have been detected in the monitor, 149 of them persistent and 93 detected only in outburst. Among these sources, 16 were previously unknown and discovered in the transient monitor. In this paper, we discuss the methodology and the data processing and ltering for the BAT transient monitor and review its sensitivity and exposure. We provide a summary of the source detections and classify them according to the variability of their light curves. Finally, we review all new BAT monitor discoveries and present basic data analysis and interpretations for those sources with previously unpublished results.

  2. The Swift-BAT Hard X-Ray Transient Monitor

    Science.gov (United States)

    Krimm, H. A.; Holland, S. T.; Corbet, R. H. D.; Pearlman, A. B.; Romano, P.; Kennea, J. A.; Bloom, J. S.; Barthelmy, S. D.; Baumgartner, W. H.; Cummings, J. R.; hide

    2013-01-01

    The Swift/Burst Alert Telescope (BAT) hard X-ray transient monitor provides near real-time coverage of the X-ray sky in the energy range 15-50 keV. The BAT observes 88% of the sky each day with a detection sensitivity of 5.3 mCrab for a full-day observation and a time resolution as fine as 64 s. The three main purposes of the monitor are (1) the discovery of new transient X-ray sources, (2) the detection of outbursts or other changes in the flux of known X-ray sources, and (3) the generation of light curves of more than 900 sources spanning over eight years. The primary interface for the BAT transient monitor is a public Web site. Between 2005 February 12 and 2013 April 30, 245 sources have been detected in the monitor, 146 of them persistent and 99 detected only in outburst. Among these sources, 17 were previously unknown and were discovered in the transient monitor. In this paper, we discuss the methodology and the data processing and filtering for the BAT transient monitor and review its sensitivity and exposure.We provide a summary of the source detections and classify them according to the variability of their light curves. Finally, we review all new BAT monitor discoveries. For the new sources that are previously unpublished, we present basic data analysis and interpretations.

  3. THE SWIFT/BAT HARD X-RAY TRANSIENT MONITOR

    International Nuclear Information System (INIS)

    Krimm, H. A.; Holland, S. T.; Corbet, R. H. D.; Pearlman, A. B.; Baumgartner, W. H.; Cummings, J. R.; Romano, P.; Kennea, J. A.; Bloom, J. S.; Barthelmy, S. D.; Gehrels, N.; Lien, A. Y.; Markwardt, C. B.; Ukwatta, T. N.; Palmer, D. M.; Sakamoto, T.; Stamatikos, M.

    2013-01-01

    The Swift/Burst Alert Telescope (BAT) hard X-ray transient monitor provides near real-time coverage of the X-ray sky in the energy range 15-50 keV. The BAT observes 88% of the sky each day with a detection sensitivity of 5.3 mCrab for a full-day observation and a time resolution as fine as 64 s. The three main purposes of the monitor are (1) the discovery of new transient X-ray sources, (2) the detection of outbursts or other changes in the flux of known X-ray sources, and (3) the generation of light curves of more than 900 sources spanning over eight years. The primary interface for the BAT transient monitor is a public Web site. Between 2005 February 12 and 2013 April 30, 245 sources have been detected in the monitor, 146 of them persistent and 99 detected only in outburst. Among these sources, 17 were previously unknown and were discovered in the transient monitor. In this paper, we discuss the methodology and the data processing and filtering for the BAT transient monitor and review its sensitivity and exposure. We provide a summary of the source detections and classify them according to the variability of their light curves. Finally, we review all new BAT monitor discoveries. For the new sources that are previously unpublished, we present basic data analysis and interpretations

  4. Radio and X-Ray Observations of the 1998 Outburst of the Recurrent X-Ray Transient 4U 1630-47

    Science.gov (United States)

    Hjellming, R. M.; Rupen, M. P.; Mioduszewski, A. J.; Kuulkers, E.; McCollough, M.; Harmon, B. A.; Buxton, M.; Sood, R.; Tzioumis, A.; Rayner, D.; Dieters, S.; Durouchoux, P.

    1999-03-01

    We report radio (NRAO VLA and Australia Telescope Compact Array), soft X-ray (Rossi X-Ray Timing Explorer ASM), and hard X-ray (Compton Gamma Ray Observatory BATSE) observations of a 1998 outburst in the recurring X-ray transient 4U 1630-47, where radio emission was detected for the first time. The radio observations identify the position of 4U 1630-47 to within 1". Because the radio emission is optically thin with a spectral index of ~-0.8 during the rise, peak, and decay of the initial radio event, the emission is probably coming from an optically thin radio jet ejected over a period of time. The 20-100 keV emission first appeared 1998 January 28 (MJD 50841), the 2-12 keV emission first appeared 1998 February 3 (MJD 50847), and the first radio emission was detected 1998 February 12.6 (MJD 50856.6). The rise of the radio emission probably began about 1998 February 7 (MJD 50851) when the X-rays were in a very hard fluctuating-hardness state, just before changing to a softer, more stable hardness state.

  5. Puzzling thermonuclear burst behaviour from the transient low-mass X-ray binary IGR J17473-2721

    DEFF Research Database (Denmark)

    Chenevez, Jérôme

    2010-01-01

    We investigate the thermonuclear bursting behaviour of IGR J17473-2721, an X-ray transient that in 2008 underwent a six month long outburst, starting (unusually) with an X-ray burst. We detected a total of 57 thermonuclear bursts throughout the outburst with AGILE, Swift, RXTE, and INTEGRAL...... it dropped (at a persistent flux corresponding to 15%of m˙ Edd) a few days before the outburst peak, after which bursts were not detected for a month. As the persistent emission subsequently decreased, the bursting activity resumed at a much lower rate than during the outburst rise. This hysteresis may arise...... produced a similar quenching of burst activity....

  6. RXTE Observation of 4U 1630-47 During its 1998 Outburst

    Science.gov (United States)

    Dieters, Stefan W.

    1999-01-01

    During the 1998 outburst of 4U 1630-47 it was extensively observed with the Rossi X-ray Timing Explorer (RXTE). In order to cover the outburst more thoroughly our data (Obs. ID: 30178-0[1-2]- ) were combined with those of Cui et al. (Obs. ID: 30188-02-). These observations were later compared with the complementary observations. Power density and energy spectra have been made for each observation. The data was used to place radio and hard X-ray observations within context. Analysis of SAX (Satellite per Astronomia a raggi X) and BATSE (Burst and Transient Source Experiment) data was also included within the study. The count rate and position in hardness-intensity, color-color diagrams and simple spectral fits are used to track the concurrent spectral changes. The source showed seven distinct types of timing behavior, most of which show differences with the canonical black hole spectral/timing states. In marked contrast to previous outbursts, we find quasi-periodic oscillation (QPO) signals during nearly all stages of the outburst with frequencies between 0.06 Hz and 14 Hz and a remarkable variety of other characteristics. In particular we find large (up to 23% rms) amplitude QPO on the early rise. Later, slow 0.1 Hz semi- regular short (- 5 sec), 9 to 16% deep dips dominate the light curve. At this time there are two QPOS, one stable near 13.5 Hz and the other whose frequency drops from 6-8 Hz to - 4.5 Hz during the dips. BeppoSAX observations during the very late declining phase show 4U 1630-47 in a low state. These results will shortly be published. We are completing a detailed analysis of the energy spectra (in preparation). The QPO/noise properties are being correlated with the concurrent spectral changes. Detailed studies of the QPO are being undertaken using sophisticated timing analysis methods. Finally a comparison with the other outbursts of 1630-47 is being made.

  7. The spectral energy distribution and nature of the symbiotic system AS 296 in outburst

    International Nuclear Information System (INIS)

    Munari, U.; Whitelock, P.A.

    1989-01-01

    Photometry covering the spectral range 0.36 to 5 μm is reported for the symbiotic star As 296 about two months after the onset of the first recorded nova-like outburst. Analysis of published pre-outburst photometry provides evidence for the presence of an accreting white dwarf of high luminosity. This information together with the new observations is used to eliminate, for the 1988 event, various mechanisms which have been suggested for the outbursts in symbiotic objects. It is shown that hydrogen burning of accreted material can produce the white dwarf luminosity during quiescence. The outburst is then the result of a thermonuclear runaway in the unburnt material. The evidence is somewhat conflicting on the question of degeneracy conditions prior to the thermonuclear runaway. (author)

  8. Discovery of a cosmological, relativistic outburst via its rapidly fading optical emission

    International Nuclear Information System (INIS)

    Cenko, S. Bradley; Nugent, Peter E.; Miller, Adam A.; Bloom, Joshua S.; Filippenko, Alexei V.; Kulkarni, S. R.; Horesh, Assaf; Carpenter, John; Perley, Daniel A.; Groot, Paul J.; Hallinan, G.; Corsi, Alessandra; Fox, Derek B.; Frail, Dale A.; Gruber, D.; Rau, Arne; Gal-Yam, Avishay; Ofek, Eran O.; MacLeod, Chelsea L.; Kasliwal, Mansi M.

    2013-01-01

    We report the discovery by the Palomar Transient Factory (PTF) of the transient source PTF11agg, which is distinguished by three primary characteristics: (1) bright (R peak = 18.3 mag), rapidly fading (ΔR = 4 mag in Δt = 2 days) optical transient emission; (2) a faint (R = 26.2 ± 0.2 mag), blue (g' – R = 0.17 ± 0.29 mag) quiescent optical counterpart; and (3) an associated year-long, scintillating radio transient. We argue that these observed properties are inconsistent with any known class of Galactic transients (flare stars, X-ray binaries, dwarf novae), and instead suggest a cosmological origin. The detection of incoherent radio emission at such distances implies a large emitting region, from which we infer the presence of relativistic ejecta. The observed properties are all consistent with the population of long-duration gamma-ray bursts (GRBs), marking the first time such an outburst has been discovered in the distant universe independent of a high-energy trigger. We searched for possible high-energy counterparts to PTF11agg, but found no evidence for associated prompt emission. We therefore consider three possible scenarios to account for a GRB-like afterglow without a high-energy counterpart: an 'untriggered' GRB (lack of satellite coverage), an 'orphan' afterglow (viewing-angle effects), and a 'dirty fireball' (suppressed high-energy emission). The observed optical and radio light curves appear inconsistent with even the most basic predictions for off-axis afterglow models. The simplest explanation, then, is that PTF11agg is a normal, on-axis long-duration GRB for which the associated high-energy emission was simply missed. However, we have calculated the likelihood of such a serendipitous discovery by PTF and find that it is quite small (≈2.6%). While not definitive, we nonetheless speculate that PTF11agg may represent a new, more common (>4 times the on-axis GRB rate at 90% confidence) class of relativistic

  9. Discovery of a cosmological, relativistic outburst via its rapidly fading optical emission

    Energy Technology Data Exchange (ETDEWEB)

    Cenko, S. Bradley; Nugent, Peter E.; Miller, Adam A.; Bloom, Joshua S.; Filippenko, Alexei V. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Kulkarni, S. R.; Horesh, Assaf; Carpenter, John; Perley, Daniel A.; Groot, Paul J.; Hallinan, G. [Cahill Center for Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Corsi, Alessandra [LIGO Laboratory, California Institute of Technology, MS 100-36, Pasadena, CA 91125 (United States); Fox, Derek B. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Frail, Dale A. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); Gruber, D.; Rau, Arne [Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse, Postfach 1312, D-85748 Garching (Germany); Gal-Yam, Avishay; Ofek, Eran O. [Benoziyo Center for Astrophysics, Weizmann Institute of Science, 76100 Rehovot (Israel); MacLeod, Chelsea L. [Physics Department, United States Naval Academy, 572c Holloway Road, Annapolis, MD 21402 (United States); Kasliwal, Mansi M., E-mail: cenko@astro.berkeley.edu [Observatories of the Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101 (United States); and others

    2013-06-01

    We report the discovery by the Palomar Transient Factory (PTF) of the transient source PTF11agg, which is distinguished by three primary characteristics: (1) bright (R {sub peak} = 18.3 mag), rapidly fading (ΔR = 4 mag in Δt = 2 days) optical transient emission; (2) a faint (R = 26.2 ± 0.2 mag), blue (g' – R = 0.17 ± 0.29 mag) quiescent optical counterpart; and (3) an associated year-long, scintillating radio transient. We argue that these observed properties are inconsistent with any known class of Galactic transients (flare stars, X-ray binaries, dwarf novae), and instead suggest a cosmological origin. The detection of incoherent radio emission at such distances implies a large emitting region, from which we infer the presence of relativistic ejecta. The observed properties are all consistent with the population of long-duration gamma-ray bursts (GRBs), marking the first time such an outburst has been discovered in the distant universe independent of a high-energy trigger. We searched for possible high-energy counterparts to PTF11agg, but found no evidence for associated prompt emission. We therefore consider three possible scenarios to account for a GRB-like afterglow without a high-energy counterpart: an 'untriggered' GRB (lack of satellite coverage), an 'orphan' afterglow (viewing-angle effects), and a 'dirty fireball' (suppressed high-energy emission). The observed optical and radio light curves appear inconsistent with even the most basic predictions for off-axis afterglow models. The simplest explanation, then, is that PTF11agg is a normal, on-axis long-duration GRB for which the associated high-energy emission was simply missed. However, we have calculated the likelihood of such a serendipitous discovery by PTF and find that it is quite small (≈2.6%). While not definitive, we nonetheless speculate that PTF11agg may represent a new, more common (>4 times the on-axis GRB rate at 90% confidence) class of relativistic

  10. Transient Exciplex Formation Electron Transfer Mechanism

    OpenAIRE

    Michael G. Kuzmin; Irina V. Soboleva; Elena V. Dolotova

    2011-01-01

    Transient exciplex formation mechanism of excited-state electron transfer reactions is analyzed in terms of experimental data on thermodynamics and kinetics of exciplex formation and decay. Experimental profiles of free energy, enthalpy, and entropy for transient exciplex formation and decay are considered for several electron transfer reactions in various solvents. Strong electronic coupling in contact pairs of reactants causes substantial decrease of activation energy relative to that for c...

  11. Supernovae 2016bdu and 2005gl, and their link with SN 2009ip-like transients: another piece of the puzzle

    DEFF Research Database (Denmark)

    Pastorello, A.; Kochanek, C. S.; Fraser, M.

    2018-01-01

    Supernova (SN) 2016bdu is an unusual transient resembling SN 2009ip. SN 2009ip-like events are characterized by a long-lasting phase of erratic variability which ends with two luminous outbursts a few weeks apart. The second outburst is significantly more luminous (about 3 mag) than the first. In...

  12. Physical Mechanism of Comet Outbursts: The Movie

    Science.gov (United States)

    Hartmann, William K.

    2014-11-01

    predicted for the Deep Impact experiment in Comet Tempel 1.The film is posted on the Planetary Science Institute website, www.psi.edu/hartmann. [1] Hartmann, W. K. 1993 Physical Mechanism of Comet Outbursts: An Experimental Result. Icarus 104, 226-233.

  13. Observations of classical novae in outburst

    Science.gov (United States)

    Starrfield, S.; Stryker, L. L.; Sonneborn, G.; Sparks, Warren M.; Ferland, Gary; Wagner, R. M.; Williams, R. E.; Gehrz, Robert D.; Ney, Edward P.; Kenyon, Scott

    1988-01-01

    The IUE obtained ultraviolet data on novae in outburst. The characteristics of every one of the outbursts are different. Optical and infrared data on many of the same novae were also obtained. Three members of the carbon-oxygen class of novae are presented.

  14. DAVs: Red Edge and Outbursts

    Science.gov (United States)

    Luan, Jing

    2018-04-01

    As established by ground based surveys, white dwarfs with hydrogen atmospheres pulsate as they cool across the temperature range, 12500Kred edge is a two-decade old puzzle. Recently, Kepler discovered a number of cool DAVs exhibiting sporadic outbursts separated by days, each lasting several hours, and releasing \\sim 10^{33}-10^{34} {erg}. We provide quantitative explanations for both the red edge and the outbursts. The minimal frequency for overstable modes rises abruptly near the red edge. Although high frequency overstable modes exist below the red edge, their photometric amplitudes are generally too small to be detected by ground based observations. Nevertheless, these overstable parent modes can manifest themselves through nonlinear mode couplings to damped daughter modes which generate limit cycles giving rise to photometric outbursts.

  15. Discovery and Orbital Determination of the Transient X-Ray Pulsar GRO J1750-27

    Science.gov (United States)

    Scott, D. M.; Finger, M. H.; Wilson, R. B.; Koh, D. T.; Prince, T. A.; Vaughan, B. A.; Chakrabarty, D.

    1997-01-01

    We report on the discovery and hard X-ray (20 - 70 keV) observations of the 4.45 s period transient X-ray pulsar GRO J1750-27 with the BATSE all-sky monitor on board CGRO. A relatively faint out- burst (less than 30 mcrab peak) lasting at least 60 days was observed during which the spin-up rate peaked at 38 pHz/s and was correlated with the pulsed intensity. An orbit with a period of 29.8 days was found. The large spin-up rate, spin period, and orbital period together suggest that accretion is occurring from a disk and that the outburst is a "giant" outburst typical of a Be/X-ray transient system. No optical counterpart has yet been reported.

  16. Accretion outbursts in self-gravitating protoplanetary disks

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Jaehan; Hartmann, Lee [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48105 (United States); Zhu, Zhaohuan [Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Peyton Hall, Princeton, NJ 08544 (United States); Nelson, Richard P., E-mail: jaehbae@umich.edu, E-mail: lhartm@umich.edu, E-mail: zhuzh@astro.princeton.edu, E-mail: r.p.nelson@qmul.ac.uk [Astronomy Unit, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom)

    2014-11-01

    We improve on our previous treatments of the long-term evolution of protostellar disks by explicitly solving disk self-gravity in two dimensions. The current model is an extension of the one-dimensional layered accretion disk model of Bae et al. We find that gravitational instability (GI)-induced spiral density waves heat disks via compressional heating (i.e., PdV work), and can trigger accretion outbursts by activating the magnetorotational instability (MRI) in the magnetically inert disk dead zone. The GI-induced spiral waves propagate well inside of the gravitationally unstable region before they trigger outbursts at R ≲ 1 AU where GI cannot be sustained. This long-range propagation of waves cannot be reproduced with the previously used local α treatments for GI. In our standard model where zero dead-zone residual viscosity (α{sub rd}) is assumed, the GI-induced stress measured at the onset of outbursts is locally as large as 0.01 in terms of the generic α parameter. However, as suggested in our previous one-dimensional calculations, we confirm that the presence of a small but finite α{sub rd} triggers thermally driven bursts of accretion instead of the GI + MRI-driven outbursts that are observed when α{sub rd} = 0. The inclusion of non-zero residual viscosity in the dead zone decreases the importance of GI soon after mass feeding from the envelope cloud ceases. During the infall phase while the central protostar is still embedded, our models stay in a 'quiescent' accretion phase with M-dot {sub acc}∼10{sup −8}--10{sup −7} M{sub ⊙} yr{sup −1} over 60% of the time and spend less than 15% of the infall phase in accretion outbursts. While our models indicate that episodic mass accretion during protostellar evolution can qualitatively help explain the low accretion luminosities seen in most low-mass protostars, detailed tests of the mechanism will require model calculations for a range of protostellar masses with some constraint on the

  17. Accretion outbursts in self-gravitating protoplanetary disks

    International Nuclear Information System (INIS)

    Bae, Jaehan; Hartmann, Lee; Zhu, Zhaohuan; Nelson, Richard P.

    2014-01-01

    We improve on our previous treatments of the long-term evolution of protostellar disks by explicitly solving disk self-gravity in two dimensions. The current model is an extension of the one-dimensional layered accretion disk model of Bae et al. We find that gravitational instability (GI)-induced spiral density waves heat disks via compressional heating (i.e., PdV work), and can trigger accretion outbursts by activating the magnetorotational instability (MRI) in the magnetically inert disk dead zone. The GI-induced spiral waves propagate well inside of the gravitationally unstable region before they trigger outbursts at R ≲ 1 AU where GI cannot be sustained. This long-range propagation of waves cannot be reproduced with the previously used local α treatments for GI. In our standard model where zero dead-zone residual viscosity (α rd ) is assumed, the GI-induced stress measured at the onset of outbursts is locally as large as 0.01 in terms of the generic α parameter. However, as suggested in our previous one-dimensional calculations, we confirm that the presence of a small but finite α rd triggers thermally driven bursts of accretion instead of the GI + MRI-driven outbursts that are observed when α rd = 0. The inclusion of non-zero residual viscosity in the dead zone decreases the importance of GI soon after mass feeding from the envelope cloud ceases. During the infall phase while the central protostar is still embedded, our models stay in a 'quiescent' accretion phase with M-dot acc ∼10 −8 --10 −7 M ⊙ yr −1 over 60% of the time and spend less than 15% of the infall phase in accretion outbursts. While our models indicate that episodic mass accretion during protostellar evolution can qualitatively help explain the low accretion luminosities seen in most low-mass protostars, detailed tests of the mechanism will require model calculations for a range of protostellar masses with some constraint on the initial core angular momentum, which

  18. Radon monitoring for the prediction of mine outbursts

    International Nuclear Information System (INIS)

    Lebecka, J.; Wysocka, M.; Chalupnik, S.

    1993-01-01

    Observations of changes of concentrations of radon in gases occurring in coal seams prone to instantaneous outbursts of coal and gas have been performed. Gas samples have been taken from specially drilled boreholes. In coal seams prone to outbursts strong variations of radon concentration have been found, while in seams where no outbursts occurred radon concentration was much more stable. In all cases outbursts were always preceded by very low concentrations of radon, which raised again afterwards. Similar observations are performed in coal mines where a strong hazard of shocks accompanied by rock bursts occur which is caused by mining activity. Obtained results indicate the possibility of using radon as supporting indicator for prediction of instantaneous outbursts and rock bursts and may be worth-while for prevention of these catastrophes. (author). 9 refs, 2 figs

  19. State transitions in the 2001/2002 outburst of XTE J1650-500

    International Nuclear Information System (INIS)

    Rossi, S.; Homan, J.; Miller, J.M.; Belloni, T.

    2004-01-01

    We present a study of the X-ray transient and black hole candidate XTE J1650-500 during its 2001/2002 outburst. The source made two state transitions between the hard and soft states, at luminosity levels that differ by a factor of ∼5-10. The first transition, between hard and soft, lasted for ∼30 days and showed two parts; one part in which the spectral properties evolve smoothly away from the hard state and another that we identify as the 'steep power law state'. The two parts showed different behavior of the Fe K emission line and QPO frequencies. The second transition, from soft to hard, lasted only ∼15 days and showed no evidence of the presence of the 'steep power law state'. Comparing observations from the early rise and the decay of the outburst, we conclude that the source can be in the hard state in a range of more than 10 4 in luminosity. We briefly discuss the state transitions in the framework of a two-flow model

  20. INTEGRAL detects the recurrent transients XTE J1709-267 and XTE J1739-285 in outburst

    DEFF Research Database (Denmark)

    Sanchez-Fernandez, C.; Chenevez, Jérôme; Pavan, L.

    2012-01-01

    in the 20-40 keV band. We estimate a rough flux of ~8 mCrab (5 sigma) for an effective ISGRI exposure time of 21 ks. A preliminary spectral fit to the JEM-X data is consistent with an absorbed disk blackbody model of temperature ~2.2 keV. The onset of this outburst was also detected by MAXI http://maxi.riken.jp/top/index.php...

  1. The classical nova outburst

    International Nuclear Information System (INIS)

    Starrfield, S.G.

    1988-01-01

    The classical nova outburst occurs on the white dwarf component in a close binary system. Nova systems are members of the general class of cataclysmic variables and other members of the class are the Dwarf Novae, AM Her variables, Intermediate Polars, Recurrent Novae, and some of the Symbiotic variables. Although multiwavelength observations have already provided important information about all of these systems, in this review I will concentrate on the outbursts of the classical and recurrent novae and refer to other members of the class only when necessary. 140 refs., 1 tab

  2. Time-scale for turn-off of a nova after the outburst

    International Nuclear Information System (INIS)

    Starrfield, S.

    1979-01-01

    Theoretical and observational evidence is reviewed for the remnant from a nova outburst. Its evolution to burnout is described. Finally, the various physical mechanisms which can lead to an extended period of mass loss are discussed. 19 references

  3. Geological structure of strata and the occurence of gas outbursts

    Energy Technology Data Exchange (ETDEWEB)

    Koewing, K

    1977-10-20

    Geological conditions which may have an influence on gas outbursts are depth, rank, type of formation, tectonic stresses, and the petrological form of the neighboring rock. The risk of outbursts is greater if there are dirt bands in the seam, since the coal can slide on these. Tectonically disturbed zones in seams containing more than 9 cu m of gas per ton are especially dangerous. Tectonic stress is not necessarily an indication of the severity of outbursts. Gas and sandstone outbursts do not depend on tectonic disturbance; outburst-prone sandstones have a greater pore volume and lower strength than normal. Almost all outbursts from the floor occur where the strata immediately below are impervious to gas and sandstone is present lower down. (In German)

  4. Dwarf novae in outburst: modelling the observations

    International Nuclear Information System (INIS)

    Pringle, J.E.; Verbunt, F.

    1986-01-01

    Time-dependent accretion-disc models are constructed and used to calculate theoretical spectra in order to try to fit the ultraviolet and optical observations of outbursts of the two dwarf novae VW Hydri and CN Orionis. It is found that the behaviour on the rise to outburst is the strongest discriminator between theoretical models. The mass-transfer burst model is able to fit the spectral behaviour for both objects. The disc-instability model is unable to fit the rise to outburst in VW Hydri, and gives a poor fit to the observations of CN Orionis. (author)

  5. The orbital period in the supergiant fast X-ray transient IGR J16465--4507

    OpenAIRE

    Clark, D. J.; Sguera, V.; Bird, A. J; McBride, V. A.; Hill, A. B.; Scaringi, S.; Drave, S.; Bazzano, A.; Dean, A. J

    2010-01-01

    Timing analysis of the INTEGRAL-IBIS and Swift-BAT light curves of the Supergiant Fast X-ray Transient (SFXT) IGR J16465-4507 has identified a period of 30.32+/-0.02 days which we interpret as the orbital period of the binary system. In addition 11 outbursts (9 of which are previously unpublished) have been found between MJD 52652 to MJD 54764, all of which occur close to the region of the orbit we regard as periastron. From the reported flux outbursts, we found a dynamical range in the inter...

  6. Soft x-ray emission from classical novae in outburst

    International Nuclear Information System (INIS)

    Starrfield, S.; Krautter, J.; MacDonald, J.

    1989-01-01

    Theoretical modeling of novae in outburst predicts that they should be active emitters of radiation at soft x-ray wavelengths twice during their outburst. The first time occurs very early in the outburst when only a very sensitive all sky survey will be able to detect them. This period lasts only a few hours for the very fastest novae. They again become bright in x-rays late in the outburst when the remnant object becomes very hot and is still luminous. Both simulations and observations show that novae can remain very hot for months to years. It is important to observe them at these late times because a measurement both of the flux and temperature can provide information about the mass of the white dwarf, the turn-off time scale, and the energy budget of the outburst. 8 refs., 2 figs

  7. The effect of a tectonic stress field on coal and gas outbursts.

    Science.gov (United States)

    An, Fenghua; Cheng, Yuanping

    2014-01-01

    Coal and gas outbursts have always been a serious threat to the safe and efficient mining of coal resources. Ground stress (especially the tectonic stress) has a notable effect on the occurrence and distribution of outbursts in the field practice. A numerical model considering the effect of coal gas was established to analyze the outburst danger from the perspective of stress conditions. To evaluate the outburst tendency, the potential energy of yielded coal mass accumulated during an outburst initiation was studied. The results showed that the gas pressure and the strength reduction from the adsorbed gas aggravated the coal mass failure and the ground stress altered by tectonics would affect the plastic zone distribution. To demonstrate the outburst tendency, the ratio of potential energy for the outburst initiation and the energy consumption was used. Increase of coal gas and tectonic stress could enhance the potential energy accumulation ratio, meaning larger outburst tendency. The component of potential energy for outburst initiation indicated that the proportion of elastic energy was increased due to tectonic stress. The elastic energy increase is deduced as the cause for a greater outburst danger in a tectonic area from the perspective of stress conditions.

  8. Spectral evolution of dwarf nova outbursts

    International Nuclear Information System (INIS)

    Cannizzo, J.K.; Kenyon, S.J.

    1987-01-01

    The disk instability model for dwarf nova eruptions is investigated by computing the spectral development of the accretion disk through a complete limit cycle. Observed stellar spectra are used to model the radiation emitted by optically thick annuli within the disc. The general findings agree with those of Smak (1984) and Pringle et al. (1986). It is suggested that the dwarf nova oscillations might be a source of information concerning the evolution of the inner disk and that detailed observations of this phenomenon can be used to test various outburst mechanisms. 74 references

  9. Propagation characteristics of pulverized coal and gas two-phase flow during an outburst.

    Science.gov (United States)

    Zhou, Aitao; Wang, Kai; Fan, Lingpeng; Tao, Bo

    2017-01-01

    Coal and gas outbursts are dynamic failures that can involve the ejection of thousands tons of pulverized coal, as well as considerable volumes of gas, into a limited working space within a short period. The two-phase flow of gas and pulverized coal that occurs during an outburst can lead to fatalities and destroy underground equipment. This article examines the interaction mechanism between pulverized coal and gas flow. Based on the role of gas expansion energy in the development stage of outbursts, a numerical simulation method is proposed for investigating the propagation characteristics of the two-phase flow. This simulation method was verified by a shock tube experiment involving pulverized coal and gas flow. The experimental and simulated results both demonstrate that the instantaneous ejection of pulverized coal and gas flow can form outburst shock waves. These are attenuated along the propagation direction, and the volume fraction of pulverized coal in the two-phase flow has significant influence on attenuation of the outburst shock wave. As a whole, pulverized coal flow has a negative impact on gas flow, which makes a great loss of large amounts of initial energy, blocking the propagation of gas flow. According to comparison of numerical results for different roadway types, the attenuation effect of T-type roadways is best. In the propagation of shock wave, reflection and diffraction of shock wave interact through the complex roadway types.

  10. The Shape of Long Outbursts in U Gem Type Dwarf Novae from AAVSO Data

    Science.gov (United States)

    Cannizzo, John K.

    2012-01-01

    We search the American Association of Variable Star Observers (AAVSO) archives of the two best studied dwarf novae in an attempt to find light curves for long out bursts that are extremely well-characterized. The systems are U Gem and S8 Cyg. Our goal is to search for embedded precursors such as those that have been found recently in the high fidelity Kepler data for superoutbursts of some members of the 8U UMa subclass of dwarf novae. For the vast majority of AAV80 data, the combination of low data cadence and large errors associated with individual measurements precludes one from making any strong statement about the shape of the long outbursts. However, for a small number of outbursts, extensive long term monitoring with digital photometry yields high fidelity light curves. We report the finding of embedded precursors in two of three candidate long outbursts. This reinforces van Paradijs' finding that long outbursts in dwarf novae above the period gap and superoutbursts in systems below the period gap constitute a unified class. The thermal-tidal instability to account for superoutbursts in the SU UMa stars predicts embedded precursors only for short orbital period dwarf novae, therefore the presence of embedded precursors in long orbital period systems - U Gem and SS Cyg - argues for a more general mechanism to explain long outbursts.

  11. Mechanical modelling of transient- to- failure SFR fuel cladding

    Energy Technology Data Exchange (ETDEWEB)

    Feria, F.; Herranz, L. E.

    2014-07-01

    The response of Sodium Fast Reactor (SFR) fuel rods to transient accident conditions is an important safety concern. During transients the cladding strain caused by the stress due to pellet cladding mechanical interaction (PCMI) can lead to failure. Due to the fact that SFR fuel rods are commonly clad with strengthened material made of stainless steel (SS), cladding is usually treated as an elastic-perfectly-plastic material. However, viscoplastic behaviour can contribute to mechanical strain at high temperature (> 1000 K). (Author)

  12. Supergiant fast X-ray transients with Swift: Spectroscopic and temporal properties

    Science.gov (United States)

    Romano, P.; Mangano, V.; Ducci, L.; Esposito, P.; Farinelli, R.; Ceccobello, C.; Vercellone, S.; Burrows, D. N.; Kennea, J. A.; Krimm, H. A.; Gehrels, N.

    2012-12-01

    Supergiant fast X-ray transients (SFXTs) are a class of high-mass X-ray binaries with possible counterparts in the high energy gamma rays. The Swift SFXT Project1 has conducted a systematic investigation of the properties of SFTXs on timescales ranging from minutes to years and in several intensity states (from bright flares, to intermediate intensity states, and down to almost quiescence). We also performed broad-band spectroscopy of outbursts, and intensity-selected spectroscopy outside of outbursts. We demonstrated that while the brightest phase of the outburst only lasts a few hours, further activity is observed at lower fluxes for a remarkably longer time, up to weeks. Furthermore, we assessed the fraction of the time these sources spend in each phase, and their duty cycle of inactivity. We present the most recent results from our investigation. The spectroscopic and, most importantly, timing properties of SFXTs we have uncovered with Swift will serve as a guide in search for the high energy emission from these enigmatic objects.

  13. Convection causes enhanced magnetic turbulence in accretion disks in outburst

    Energy Technology Data Exchange (ETDEWEB)

    Hirose, Shigenobu [Department of Mathematical Science and Advanced Technology, JAMSTEC, Yokohama, Kanagawa 236-0001 (Japan); Blaes, Omer; Coleman, Matthew S. B. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Krolik, Julian H. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Sano, Takayoshi, E-mail: shirose@jamstec.go.jp [Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871 (Japan)

    2014-05-20

    We present the results of local, vertically stratified, radiation magnetohydrodynamic (MHD) shearing box simulations of magneto-rotational instability (MRI) turbulence appropriate for the hydrogen ionizing regime of dwarf nova and soft X-ray transient outbursts. We incorporate the frequency-integrated opacities and equation of state for this regime, but neglect non-ideal MHD effects and surface irradiation, and do not impose net vertical magnetic flux. We find two stable thermal equilibrium tracks in the effective temperature versus surface mass density plane, in qualitative agreement with the S-curve picture of the standard disk instability model. We find that the large opacity at temperatures near 10{sup 4} K, a corollary of the hydrogen ionization transition, triggers strong, intermittent thermal convection on the upper stable branch. This convection strengthens the magnetic turbulent dynamo and greatly enhances the time-averaged value of the stress to thermal pressure ratio α, possibly by generating vertical magnetic field that may seed the axisymmetric MRI, and by increasing cooling so that the pressure does not rise in proportion to the turbulent dissipation. These enhanced stress to pressure ratios may alleviate the order of magnitude discrepancy between the α-values observationally inferred in the outburst state and those that have been measured from previous local numerical simulations of magnetorotational turbulence that lack net vertical magnetic flux.

  14. AN EXTRAORDINARY OUTBURST OF THE MAGNETAR SWIFT J1822.3–1606

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, Manoneeta; Göğüş, Ersin [Sabancı University, Faculty of Engineering and Natural Sciences, Orhanlı Tuzla 34956, İstanbul (Turkey)

    2015-08-20

    The 2011 outburst of Swift J1822.3–1606 was extraordinary; periodic modulations at the spin period of the underlying neutron star were clearly visible, remarkably similar to what is observed during the decaying tail of magnetar giant flares. We investigated the temporal characteristics of X-ray emission during the early phases of the outburst. We performed a periodicity search with the spectral hardness ratio (HR) and found a coherent signal near the spin period of the neutron star, but with a lag of about 3 radians. Therefore, the HR is strongly anti-correlated with the X-ray intensity, which is also seen in the giant flares. We studied the time evolution of the pulse profile and found that it evolves from a complex morphology to a much simpler shape within about a month. Pulse profile simplification also takes place during the giant flares, but on a much shorter timescale of about a few minutes. We found that the amount of energy emitted during the first 25 days of the outburst is comparable to what was detected in minutes during the decaying tail of giant flares. Based on these similarities, we suggest that the triggering mechanisms of the giant flares and the magnetar outbursts are likely the same. We propose that the trapped fireball that develops in the magnetosphere at the onset of the outburst radiates away efficiently in minutes in magnetars exhibiting giant flares, while in other magnetars, such as Swift J1822.3–1606, the efficiency of radiation of the fireball is not as high and, therefore, lasts much longer.

  15. Three-dimensional hydrodynamical models of wind and outburst-related accretion in symbiotic systems

    Science.gov (United States)

    de Val-Borro, M.; Karovska, M.; Sasselov, D. D.; Stone, J. M.

    2017-07-01

    Gravitationally focused wind accretion in binary systems consisting of an evolved star with a gaseous envelope and a compact accreting companion is a possible mechanism to explain mass transfer in symbiotic binaries. We study the mass accretion around the secondary caused by the strong wind from the primary late-type component using global three-dimensional hydrodynamic numerical simulations during quiescence and outburst stages. In particular, the dependence of the mass accretion rate on the mass-loss rate, wind parameters and phases of wind outburst development is considered. For a typical wind from an asymptotic giant branch star with a mass-loss rate of 10-6 M⊙ yr-1 and wind speeds of 20-50 km s-1, the mass transfer through a focused wind results in efficient infall on to the secondary. Accretion rates on to the secondary of 5-20 per cent of the mass-loss from the primary are obtained during quiescence and outburst periods where the wind velocity and mass-loss rates are varied, about 20-50 per cent larger than in the standard Bondi-Hoyle-Lyttleton approximation. This mechanism could be an important method for explaining observed accretion luminosities and periodic modulations in the accretion rates for a broad range of interacting binary systems.

  16. Outburst flood evolution at Russell Glacier, western Greenland

    DEFF Research Database (Denmark)

    Carrivick, Jonathan L.; Turner, Andy G.D.; Russell, Andrew J.

    2013-01-01

    Glacial lake outburst floods have produced a distinctive and widespread Quaternary record both onshore and offshore via widespread and intense geomorphological impacts, yet these impacts remain poorly understood due to a lack of modern analogues. This study therefore makes a systematic quantifica...... of including intermediary lakes. Modern hazard mitigation studies could usefully note the potential use of reservoirs as an outburst flood alleviation resource.......Glacial lake outburst floods have produced a distinctive and widespread Quaternary record both onshore and offshore via widespread and intense geomorphological impacts, yet these impacts remain poorly understood due to a lack of modern analogues. This study therefore makes a systematic...... quantification of the evolution of a bedrock-channelled outburst flood. Channel topography was obtained from digitised aerial photographs, a 5 m grid resolution DEM and bathymetric surveys. Flood inundation was measured in the field from dGPS measurements. Flood evolution was analysed with application...

  17. Modeling the classical nova outburst. I. Exploring the physics of a new mechanism

    International Nuclear Information System (INIS)

    Kutter, G.S.; Sparks, W.M.

    1989-01-01

    Model calculations were performed to describe a mechanism that produces classical nova outbursts on white dwarfs of 1 solar mass or less and for accretion rates of 4 x 10 to the -10th solar mass/yr or greater, i.e., the parameters corresponding to observed data of nova systems. Calculations point to four factors that can induce nuclear runaways of sufficient strength to eject about 0.0001 solar mass at speeds of several hundred to a few thousand km per second, as is observed in classical novae. These are (1) the effects of storage of angular momentum in the star's envelope during the accretion phase; (2) the reduction of centrifugal forces in the star's outer layers during the early nuclear runaway phase, through the inward transport of angular momentum; (3) the inward movement of the zone of peak nuclear burning through the convectively induced shear instability during the runaway phase; and (4) the mixing of original CO stellar matter and H-rich matter, also through the convectively induced shear instability. 58 refs

  18. Dwarf novae in outburst: simultaneous ultraviolet and optical observations of VW Hydri

    International Nuclear Information System (INIS)

    Schwarzenberg-Czerny, A.; Jones, D.H.P.; Ward, M.; Pringle, J.E.; Verbunt, F.

    1985-01-01

    Simultaneous spectrophotometry of the dwarf nova VW Hydri in the range 1200-7000 A is presented. The main set of observations cover one complete outburst, including the rise and the decline. Comparing these data with data from other outbursts of VW Hyi it is found that all the data can be interleaved. This underlines the similarity in the behaviour of the continuum flux distribution from outburst to outburst. In particular the discovery by previous authors that the outburst starts at optical wavelengths and spreads later to the ultraviolet is confirmed. (author)

  19. Review of the classical nova outburst

    International Nuclear Information System (INIS)

    Starrfield, S.; Sparks, W.M.

    1986-06-01

    Observational studies have not only identified a new class of novae but theoretical simulations of this class have been found to be in excellent agreement with the observations. This new class consists of outbursts occurring on ONeMg white dwarfs in close binar systems in contrast to the other outbursts which are occurring on CO white dwarfs. We also review the effects of the β + -unstable nuclei and show how their presence has a major effect on the evolution. 77 refs

  20. Outbursts from the secondary component in OJ 287 and the secondary spin-up

    Directory of Open Access Journals (Sweden)

    Pihajoki P.

    2012-12-01

    Full Text Available At the end of March 2012 a prominent optical outburst was observed in the binary black hole system OJ 287. It does not fit the expected sequence of outbursts from the primary component and the bremsstrahlung outbursts from the accretion disk impacts of the secondary component. These occur in a well established pattern repeated with an approximately 12 year interval. In this work we discuss the possibility that the outburst originates from the secondary black hole. The timing of the 2012 outburst relative to the expected sequence would make it a counterpart of the precursor outbursts in 1993 and 2004, which occured before the main pattern of outbursts. If so, it appears that a precursor occurs when the secondary reaches a constant level above the mean accretion disk level of the primary component. It may be that this encounter induces an outburst in the secondary which is nearly as prominent as the outbursts in the expected sequence. The strength of these outbursts depends strongly on the spin of the secondary. In this work we investigate the limits on the secondary spin-up and spin alignment from interaction with the accretion disk of the primary component and its magnetic field.

  1. PTF13efv—AN OUTBURST 500 DAYS PRIOR TO THE SNHUNT 275 EXPLOSION AND ITS RADIATIVE EFFICIENCY

    Energy Technology Data Exchange (ETDEWEB)

    Ofek, E. O.; Strotjohann, N.-L.; Rubin, A.; Gal-Yam, A.; Yaron, O. [Benoziyo Center for Astrophysics and the Helen Kimmel Center for Planetary Science, Weizmann Institute of Science, 76100 Rehovot (Israel); Cenko, S. B. [Astrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MD, 20771 (United States); Shaviv, N. J. [Racah Institute of Physics, The Hebrew University, 91904 Jerusalem (Israel); Duggan, G.; Kulkarni, S. R.; Cao, Y. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Sullivan, M. [School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom); Nugent, P. E. [Computational Cosmology Center, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Kasliwal, M. M. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena CA 91101 (United States); Sollerman, J.; Fransson, C. [Department of Astronomy, The Oskar Klein Centre, Stockholm University, AlbaNova University Centre, SE-106 91 Stockholm (Sweden); Filippenko, A. V. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Perley, D. A. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Laher, R. [Spitzer Science Center, MS 314-6, California Institute of Technology, Pasadena, CA 91125 (United States)

    2016-06-10

    The progenitors of some supernovae (SNe) exhibit outbursts with super-Eddington luminosities prior to their final explosions. This behavior is common among SNe IIn, but the driving mechanisms of these precursors are not yet well-understood. SNHunt 275 was announced as a possible new SN during 2015 May. Here we report on pre-explosion observations of the location of this event by the Palomar Transient Factory (PTF) and report the detection of a precursor about 500 days prior to the 2015 May activity (PTF 13efv). The observed velocities in the 2015 transient and its 2013 precursor absorption spectra are low (1000–2000 km s{sup −1}), so it is not clear yet if the recent activity indeed marks the final disruption of the progenitor. Regardless of the nature of this event, we use the PTF photometric and spectral observations, as well as Swift -UVOT observations, to constrain the efficiency of the radiated energy relative to the total kinetic energy of the precursor. We find that, using an order-of-magnitude estimate and under the assumption of spherical symmetry, the ratio of the radiated energy to the kinetic energy is in the range of 4 × 10{sup −2} to 3.4 × 10{sup 3}.

  2. What Powers the 2006 Outburst of the Symbiotic Star BF Cygni?

    Directory of Open Access Journals (Sweden)

    A. Skopal

    2015-02-01

    Full Text Available BF Cygni is a classical symbiotic binary. Its optical light curve occasionally shows outbursts of the Z And-type, whose nature is not well understood. During the 2006 August, BF Cyg underwent the recent outburst, and continues its active phase to the present. The aim of this contribution is to determine the fundamental parameters of the hot component in the binary during the active phase. For this purpose we used a high- and low-resolution optical spectroscopy and the multicolour UBV RCIC photometry. Our photometric monitoring revealed that a high level of the star’s brightness lasts for unusually long time of > 7 years. A sharp violet-shifted absorption component and broad emission wings in the Hα profile developed during the whole active phase. From 2009, our spectra revealed a bipolar ejection from the white dwarf (WD. Modelling the spectral energy distribution (SED of the low-resolution spectra showed simultaneous presence of a warm (< 10 000 K disk-like pseudophotosphere and a strong nebular component of radiation (emission measure of ~1061 cm−3. The luminosity of the hot active object was estimated to > 5−8×103 Lʘ. Such high luminosity, sustained for the time of years, can be understood as a result of an enhanced transient accretion rate throughout a large disk, leading also to formation of collimated ejection from the WD.

  3. Mechanisms of transient radiation-induced creep

    International Nuclear Information System (INIS)

    Pyatiletov, Yu.S.

    1981-01-01

    Radiation-induced creep at the transient stage is investigated for metals. The situation, when several possible creep mechanisms operate simultaneously is studied. Among them revealed are those which give the main contribution and determine thereby the creep behaviour. The time dependence of creep rate and its relation to the smelling rate is obtained. The results satisfactorily agree with the available experimental data [ru

  4. HOPS 383: AN OUTBURSTING CLASS 0 PROTOSTAR IN ORION

    Energy Technology Data Exchange (ETDEWEB)

    Safron, Emily J.; Megeath, S. Thomas; Booker, Joseph [Ritter Astrophysical Observatory, Department of Physics and Astronomy, University of Toledo, Toledo, OH (United States); Fischer, William J. [NASA Goddard Space Flight Center, Greenbelt, MD (United States); Furlan, Elise; Rebull, Luisa M. [Infrared Processing and Analysis Center, Caltech, Pasadena, CA (United States); Stutz, Amelia M. [Max-Planck-Institut für Astronomie, Heidelberg (Germany); Stanke, Thomas [European Southern Observatory, Garching bei München (Germany); Billot, Nicolas [Instituto de Radio Astronomía Milimétrica, Granada (Spain); Tobin, John J. [Leiden Observatory, Leiden (Netherlands); Ali, Babar [Space Science Institute, Boulder, CO (United States); Allen, Lori E. [National Optical Astronomy Observatory, Tucson, AZ (United States); Watson, Dan M. [Department of Physics and Astronomy, University of Rochester, Rochester, NY (United States); Wilson, T. L., E-mail: wjfischer@gmail.com [Naval Research Laboratory, Washington, DC (United States)

    2015-02-10

    We report the dramatic mid-infrared brightening between 2004 and 2006 of Herschel Orion Protostar Survey (HOPS) 383, a deeply embedded protostar adjacent to NGC 1977 in Orion. By 2008, the source became a factor of 35 brighter at 24 μm with a brightness increase also apparent at 4.5 μm. The outburst is also detected in the submillimeter by comparing APEX/SABOCA to SCUBA data, and a scattered-light nebula appeared in NEWFIRM K{sub s} imaging. The post-outburst spectral energy distribution indicates a Class 0 source with a dense envelope and a luminosity between 6 and 14 L{sub ⊙}. Post-outburst time-series mid- and far-infrared photometry show no long-term fading and variability at the 18% level between 2009 and 2012. HOPS 383 is the first outbursting Class 0 object discovered, pointing to the importance of episodic accretion at early stages in the star formation process. Its dramatic rise and lack of fading over a 6 year period hint that it may be similar to FU Ori outbursts, although the luminosity appears to be significantly smaller than the canonical luminosities of such objects.

  5. Monitoring the Galactic - Search for Hard X-Ray Transients

    Science.gov (United States)

    Marshall, Francis

    Hard X-ray transients with fluxs from ~1 to ~30 mCrab are a common feature of the galactic plane with apparent concentrations in specific regions of the plane. Concentrations in the Scutum and Carina fields probably indicate an enhancement of Be X-ray binaries along the tangent direction of two spiral arms. The frequency of outbursts suggest that at any one time 1 or 2 transients are active in the Scutum field alone. We propose weekly scans of the galactic plane to understand this population of sources. The scans will also monitor about 50 already known sources with better spectral information than available with the ASM.

  6. Outburst of the 2 s Anomalous X-ray Pulsar 1E 1547.0-5408

    Science.gov (United States)

    Halpern, J. P.; Gotthelf, E. V.; Camilo, F.; Reynolds, J.; Ransom, S. M.

    2008-01-01

    Following our discovery of radio pulsations from the newly recognized anomalous X-ray pulsar (AXP) 1E 1547.0-5408, we initiated X-ray monitoring with the Swift X-ray telescope and obtained a single target-of-opportunity observation with the Newton X-ray Multi-Mirror Mission (XMM-Newton). In comparison with its historic minimum flux of 3 x 10(exp -l3)ergs/sq cm/s, the source was found to be in a record high state, f(sub x)(1-8 keV) = 5 x 10(exp -12)ergs/sq cm/s, or L(sub x) = 1.7 x 10(exp 35)(d/9 kpc )(sup 2)ergs/s, and declining by 25% in 1 month. Extrapolating the decay, we bound the total energy in this outburst to 1042 ergs pulsar, which may indicate a nearly aligned rotator. As also inferred from the transient behavior of XTE J18 10-197, the only other AXP known to emit in the radio, the magnetic field rearrangement responsible for this X-ray outburst of 1E 1547.0-5408 is probably the cause of its radio turn-on.

  7. Dwarf novae in outburst: monitoring WX Hydri with IUE

    International Nuclear Information System (INIS)

    Hassall, B.J.M.; Pringle, J.E.; Verbunt, F.

    1985-01-01

    WX Hydri has been monitored with the IUE satellite. The data obtained during the beginning of an outburst show that the rise of the optical precedes that of the ultraviolet flux. The observations during quiescence, together with archival data, indicate that the ultraviolet continuum and line fluxes decrease steadily between outbursts. The implications of the observations for the theoretical models of dwarf nova outbursts are discussed. It is concluded that the variable mass transfer model can accommodate the observations, but that difficulties arise for the disc instability model. (author)

  8. Repeated Transient Jets from a Warped Disk in the Symbiotic Prototype Z And: A Link to the Long-lasting Active Phase

    Science.gov (United States)

    Skopal, Augustin; Tarasova, Taya. N.; Wolf, Marek; Dubovský, Pavol A.; Kudzej, Igor

    2018-05-01

    Active phases of some symbiotic binaries survive for a long time, from years to decades. The accretion process onto a white dwarf (WD) sustaining long-lasting activity, and sometimes leading to collimated ejection, is not well understood. We present the repeated emergence of highly collimated outflows (jets) from the symbiotic prototype Z And during its 2008 and 2009–10 outbursts and suggest their link to the current long-lasting (from 2000) active phase. We monitored Z And with high-resolution spectroscopy, multicolor UBVR C—and high time resolution—photometry. The well-pronounced bipolar jets were ejected again during the 2009–10 outburst together with the simultaneous emergence of the rapid photometric variability (Δm ≈ 0.06 mag) on the timescale of hours, showing similar properties as those during the 2006 outburst. These phenomena and the measured disk–jets connection could be caused by the radiation-induced warping of the inner disk due to a significant increase of the burning WD luminosity. Ejection of transient jets by Z And around outburst maxima signals a transient accretion at rates above the upper limit of the stable hydrogen burning on the WD surface, and thus proves the nature of Z And-type outbursts. The enhanced accretion through the disk warping, supplemented by the accretion from the giant’s wind, can keep a high luminosity of the WD for a long time, until depletion of the disk. In this way, the jets provide a link to long-lasting active phases of Z And.

  9. Study of a sample of faint Be stars in the exofield of CoRoT. II. Pulsation and outburst events: Time series analysis of photometric variations

    Science.gov (United States)

    Semaan, T.; Hubert, A. M.; Zorec, J.; Gutiérrez-Soto, J.; Frémat, Y.; Martayan, C.; Fabregat, J.; Eggenberger, P.

    2018-06-01

    Context. The class of Be stars are the epitome of rapid rotators in the main sequence. These stars are privileged candidates for studying the incidence of rotation on the stellar internal structure and on non-radial pulsations. Pulsations are considered possible mechanisms to trigger mass-ejection phenomena required to build up the circumstellar disks of Be stars. Aims: Time series analyses of the light curves of 15 faint Be stars observed with the CoRoT satellite were performed to obtain the distribution of non-radial pulsation (NRP) frequencies in their power spectra at epochs with and without light outbursts and to discriminate pulsations from rotation-related photometric variations. Methods: Standard Fourier techniques were employed to analyze the CoRoT light curves. Fundamental parameters corrected for rapid-rotation effects were used to study the power spectrum as a function of the stellar location in the instability domains of the Hertzsprung-Russell (H-R) diagram. Results: Frequencies are concentrated in separate groups as predicted for g-modes in rapid B-type rotators, except for the two stars that are outside the H-R instability domain. In five objects the variations in the power spectrum are correlated with the time-dependent outbursts characteristics. Time-frequency analysis showed that during the outbursts the amplitudes of stable main frequencies within 0.03 c d-1 intervals strongly change, while transients and/or frequencies of low amplitude appear separated or not separated from the stellar frequencies. The frequency patterns and activities depend on evolution phases: (i) the average separations between groups of frequencies are larger in the zero-age main sequence (ZAMS) than in the terminal age main sequence (TAMS) and are the largest in the middle of the MS phase; (ii) a poor frequency spectrum with f ≲ 1 cd-1 of low amplitude characterizes the stars beyond the TAMS; and (iii) outbursts are seen in stars hotter than B4 spectral type and in the

  10. Developments in outburst prediction by microseismic monitoring from the surface

    Energy Technology Data Exchange (ETDEWEB)

    Davies, A W; Styles, P; Jones, V K

    1987-01-01

    Violent outbursts of coal and firedamp affect production operations in most of the coal producing countries of the world, often leading to heavy loss of life. Significant changes in the pattern of Welsh outbursts from 1978 onwards are described with a far larger proportion occurring on longwall faces than was previously the case and with a much higher incidence of spontaneous outbursts, which carry a greater risk than those which are deliberately induced. The elaborate defences in use appeared inadequate to deal with the changing circumstances as methane based alarms only operated after the outburst phenomenon had initiated. An earlier warning of an incipient outburst was required and evidence suggested that seismic monitoring might provide this early warning. A surface located seismometer was installed giving radio transmitted signals to a tape recorder in the colliery control room. This provided promising historical records and led to five surface seismometer stations being commissioned feeding signals, suitably treated, to a micro-processor located in the mine control room. The programming of the micro-processor was arranged to give a real time alarm at pre-set levels of seismic activity in defined areas of the mine. Experience with the new predictive tool is described, as well as the use made of the new facility by management, including changed methods of outburst stress relief.

  11. Intense soft x-rays from RS Ophiuchi during the 1985 outburst

    International Nuclear Information System (INIS)

    Mason, K.O.; Cordova, F.A.; Bode, M.F.; Barr, P.

    1985-01-01

    Intense soft x-ray emission with a characteristic temperature of a few million degrees has been detected from the recurrent nova RS Oph approximately two months after its January 1985 optical outburst. This is the first detection of x-rays from such a system at outburst. The x-radiation is interpreted as emission from circumstellar gas that is shock heated by the passage of the blast wave from the nova explosion. The rapid decline of the x-ray flux between about 60 and 90 days after the outburst probably occurs because the blast wave has reached the edge of the volume filled, between outbursts, by the stellar wind of the red giant component of the binary system. Residual x-ray emission detected from RS Oph 250 days after the outburst is interpreted as coming from the surface of a white dwarf, at a temperature of approx.300,000K, where thermonuclear burning is persisting. 7 refs., 3 figs

  12. Study on the propagation law of shock wave resulting from coal and gas outburst

    Institute of Scientific and Technical Information of China (English)

    WANG Kai; ZHOU Ai-tao; ZHANG Pin; LI Chuan; GUO Yan-wei

    2011-01-01

    According to the formation of shock wave resulting from coal and gas outburst, the gas flow of coal and gas outburst was transformed from an unsteady flow to a steady one based on selected appropriate reference coordinates, and the mathematical expressions were then established by applying mass conservation, momentum conservation equation, and energy conservation equation. On this basis, analyzed gas flow mitigation of variable cross-section area and the outburst intensity, and the relations between cross-section area, velocity, and density; the relations between overpressures and outburst intensity were deduced. Furthermore, shock waves resulting from coal and gas outburst and outburst intensity were measured by experimental setup, the overpressure and outburst intensity of different gas pressures were obtained, and the similar conditions of the experiment were numerically simulated. The averaged overpressure and gas flow velocity of variable cross-section under different gas pressures were numerically derived. The results show that the averaged overpressure and outburst intensity obtained from simulation are in good agreement with the experimental results. Moreover, the gas flow velocity of variable cross-sections approximates to the theoretical analysis.

  13. Stedy emission from recurrent transient pulsar 0535+26

    International Nuclear Information System (INIS)

    Manchanda, R.K.; Bazzano, A.; Polcaro, V.F.; Padula, C.D.L.; Obertini, P.

    1984-01-01

    A steady hard X-ray emission between 20-100 keV was observed from the 104 sec pulsar 0535+26 during the quiescent phase of transient activity. The present observations corespond to the binary phase of 0.7 taking 110d as the binary period. The observed flux was comparable to approx.20 milli-crab and a power law spectrum with spectral index αapprox.1.2 fits the data, and significantly differs from the observed spectrum during the outburst

  14. Two giant outbursts of V0332+53 observed with INTEGRAL

    Science.gov (United States)

    Ferrigno, Carlo; Ducci, Lorenzo; Bozzo, Enrico; Kretschmar, Peter; Kühnel, Matthias; Malacaria, Christian; Pottschmidt, Katja; Santangelo, Andrea; Savchenko, Volodymyr; Wilms, Jörn

    2016-10-01

    Context. In July 2015, the high-mass X-ray binary V0332+53 underwent a giant outburst, a decade after the previous one. V0332+53 hosts a strongly magnetized neutron star. During the 2004-2005 outburst, an anti-correlation between the centroid energy of its fundamental cyclotron resonance scattering features (CRSFs) and the X-ray luminosity was observed. Aims: The long (≈100 d) and bright (Lx ≈ 1038 erg s-1) 2015 outburst provided the opportunity to study the unique properties of the fundamental CRSF during another outburst and to study its dependence on the X-ray luminosity. Methods: The source was observed by the INTEGRAL satellite for ~330 ks. We exploit the spectral resolution at high energies of the SPectrometer on INTEGRAL (SPI) and the Joint European X-ray Monitors to characterize its spectral properties, focusing in particular on the CRSF-luminosity dependence. We complement the data of the 2015 outburst with those collected by SPI in 2004-2005, which have so far been left unpublished. Results: We find a highly significant anti-correlation of the centroid energy of the fundamental CRSF and the 3-100 keV luminosity of E1 ∝ -0.095(8)L37 keV. This trend is observed for both outbursts. We confirm the correlation between the width of the fundamental CRSF and the X-ray luminosity previously found in the JEM-X and IBIS dataset of the 2004-2005 outburst. By exploiting the RXTE/ASM and Swift/BAT monitoring data, we also report on the detection of a ~34 d modulation superimposed on the mean profiles and roughly consistent with the orbital period of the pulsar. We discuss possible interpretations of such variability.

  15. The outburst duration and duty cycle of GRS1915+105

    Science.gov (United States)

    Deegan, Patrick; Combet, Céline; Wynn, Graham A.

    2009-12-01

    The extraordinarily long outburst of GRS1915+105 makes it one of the most remarkable low-mass X-ray binaries (LMXBs). It has been in a state of constant outburst since its discovery in 1992, an eruption which has persisted ~100 times longer than those of more typical LXMBs. The long orbital period of GRS1915+105 implies that it contains large and massive accretion disc which is able to fuel its extreme outburst. In this paper, we address the longevity of the outburst and quiescence phases of GRS1915+105 using smooth particle hydrodynamics (SPH) simulations of its accretion disc through many outburst cycles. Our model is set in the two-α framework and includes the effects of the thermoviscous instability, tidal torques, irradiation by central X-rays and wind mass loss. We explore the model parameter space and examine the impact of the various ingredients. We predict that the outburst of GRS1915+105 should last a minimum of 20yr and possibly up to ~100yr if X-ray irradiation is very significant. The predicted recurrence times are of the order of 104yr, making the X-ray duty cycle a few 0.1 per cent. Such a low duty cycle may mean that GRS1915+105 is not an anomaly among the more standard LMXBs and that many similar, but quiescent, systems could be present in the Galaxy.

  16. Transient Dynamic Mechanical Analysis of Resilin-based Elastomeric Hydrogels

    Science.gov (United States)

    Li, Linqing; Kiick, Kristi

    2014-04-01

    The outstanding high-frequency properties of emerging resilin-like polypeptides (RLPs) have motivated their development for vocal fold tissue regeneration and other applications. Recombinant RLP hydrogels show efficient gelation, tunable mechanical properties, and display excellent extensibility, but little has been reported about their transient mechanical properties. In this manuscript, we describe the transient mechanical behavior of new RLP hydrogels investigated via both sinusoidal oscillatory shear deformation and uniaxial tensile testing. Oscillatory stress relaxation and creep experiments confirm that RLP-based hydrogels display significantly reduced stress relaxation and improved strain recovery compared to PEG-based control hydrogels. Uniaxial tensile testing confirms the negligible hysteresis, reversible elasticity and superior resilience (up to 98%) of hydrated RLP hydrogels, with Young’s modulus values that compare favorably with those previously reported for resilin and that mimic the tensile properties of the vocal fold ligament at low strain (engineering applications, of a range of RLP hydrogels.

  17. A transient, flat spectrum radio pulsar near the Galactic Centre

    Science.gov (United States)

    Dexter, J.; Degenaar, N.; Kerr, M.; Deller, A.; Deneva, J.; Lazarus, P.; Kramer, M.; Champion, D.; Karuppusamy, R.

    2017-06-01

    Recent studies have shown possible connections between highly magnetized neutron stars ('magnetars'), whose X-ray emission is too bright to be powered by rotational energy, and ordinary radio pulsars. In addition to the magnetar SGR J1745-2900, one of the radio pulsars in the Galactic Centre (GC) region, PSR J1746-2850, had timing properties implying a large magnetic field strength and young age, as well as a flat spectrum. All characteristics are similar to those of rare, transient, radio-loud magnetars. Using several deep non-detections from the literature and two new detections, we show that this pulsar is also transient in the radio. Both the flat spectrum and large amplitude variability are inconsistent with the light curves and spectral indices of three radio pulsars with high magnetic field strengths. We further use frequent, deep archival imaging observations of the GC in the past 15 yr to rule out a possible X-ray outburst with a luminosity exceeding the rotational spin-down rate. This source, either a transient magnetar without any detected X-ray counterpart or a young, strongly magnetized radio pulsar producing magnetar-like radio emission, further blurs the line between the two categories. We discuss the implications of this object for the radio emission mechanism in magnetars and for star and compact object formation in the GC.

  18. Giant planet migration during FU Orionis outbursts: 1D disc models

    Science.gov (United States)

    Dunhill, A. C.

    2018-05-01

    I present the results of semi-analytic calculations of migrating planets in young, outbursting circumstellar discs. Formed far out in the disc via gravitational fragmentation early on in its lifetime, these planets typically migrate at very slow rates and are therefore mostly expected to remain at large radii (such as is the case in HR 8799). I show that changes in the disc structure during FUor outbursts affect the planet's ability to maintain a gap and can allow a massive giant planet's semimajor axis to reduce by almost 5 per cent in a single outburst under the most optimistic conditions. Given that a single disc will likely undergo ˜10 such outbursts this process can significantly alter the expected radial distribution for GI-formed planets.

  19. Giant Metrewave Radio Telescope Monitoring of the Black Hole X-Ray Binary, V404 Cygni during Its 2015 June Outburst

    Energy Technology Data Exchange (ETDEWEB)

    Chandra, Poonam; Kanekar, Nissim [National Centre for Radio Astrophysics, TIFR, Pune University Campus, Pune 411007 (India)

    2017-09-10

    We report results from a Giant Metrewave Radio Telescope (GMRT) monitoring campaign of the black hole X-ray binary V404 Cygni during its 2015 June outburst. The GMRT observations were carried out at observing frequencies of 1280, 610, 325, and 235 MHz, and extended from June 26.89 UT (a day after the strongest radio/X-ray outburst) to July 12.93 UT. We find the low-frequency radio emission of V404 Cygni to be extremely bright and fast-decaying in the outburst phase, with an inverted spectrum below 1.5 GHz and an intermediate X-ray state. The radio emission settles to a weak, quiescent state ≈11 days after the outburst, with a flat radio spectrum and a soft X-ray state. Combining the GMRT measurements with flux density estimates from the literature, we identify a spectral turnover in the radio spectrum at ≈1.5 GHz on ≈ June 26.9 UT, indicating the presence of a synchrotron self-absorbed emitting region. We use the measured flux density at the turnover frequency with the assumption of equipartition of energy between the particles and the magnetic field to infer the jet radius (≈4.0 × 10{sup 13} cm), magnetic field (≈0.5 G), minimum total energy (≈7 × 10{sup 39} erg), and transient jet power (≈8 × 10{sup 34} erg s{sup −1}). The relatively low value of the jet power, despite V404 Cygni’s high black hole spin parameter, suggests that the radio jet power does not correlate with the spin parameter.

  20. Seven years with the Swift Supergiant Fast X-ray Transients project

    Science.gov (United States)

    Romano, P.

    2015-09-01

    Supergiant Fast X-ray Transients (SFXTs) are HMXBs with OB supergiant companions. I review the results of the Swift SFXT project, which since 2007 has been exploiting Swift's capabilities in a systematic study of SFXTs and supergiant X-ray binaries (SGXBs) by combining follow-ups of outbursts, when detailed broad-band spectroscopy is possible, with long-term monitoring campaigns, when the out-of-outburst fainter states can be observed. This strategy has led us to measure their duty cycles as a function of luminosity, to extract their differential luminosity distributions in the soft X-ray domain, and to compare, with unprecedented detail, the X-ray variability in these different classes of sources. I also discuss the ;seventh year crisis;, the challenges that the recent Swift observations are making to the prevailing models attempting to explain the SFXT behavior.

  1. Comet 17P/Holmes: contrast in activity between before and after the 2007 outburst

    Energy Technology Data Exchange (ETDEWEB)

    Ishiguro, Masateru; Kim, Yoonyoung; Warjurkar, Dhanraj S.; Ham, Ji-Beom [Department of Physics and Astronomy, Seoul National University, Gwanak, Seoul 151-742 (Korea, Republic of); Kim, Junhan [Department of Astronomy and Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Usui, Fumihiko [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Vaubaillon, Jeremie J. [Observatoire de Paris, I.M.C.C.E., Denfert Rochereau, Bat. A., F-75014 Paris (France); Ishihara, Daisuke [Department of Physics, School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 (Japan); Hanayama, Hidekazu [Ishigakijima Astronomical Observatory, National Astronomical Observatory of Japan, Ishigaki, Okinawa 907-0024 (Japan); Sarugaku, Yuki; Hasegawa, Sunao [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Kasuga, Toshihiro; Watanabe, Jun-ichi [National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Pyo, Jeonghyun [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Kuroda, Daisuke [National Institutes of Natural Sciences, Okayama Astrophysical Observatory, Kamogata-cho, Okayama 719-0232 (Japan); Ootsubo, Takafumi [Astronomical Institute, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578 (Japan); Sakamoto, Makoto; Narusawa, Shin-ya; Takahashi, Jun [Nishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyogo, Sayo, Hyogo 679-5313 (Japan); Akisawa, Hiroki, E-mail: ishiguro@astro.snu.ac.kr [Himeji City Science Museum, Himeji, Hyogo 671-2222 (Japan)

    2013-11-20

    A Jupiter-family comet, 17P/Holmes, underwent outbursts in 1892 and 2007. In particular, the 2007 outburst is known as the greatest outburst over the past century. However, little is known about the activity before the outburst because it was unpredicted. In addition, the time evolution of the nuclear physical status has not been systematically studied. Here, we study the activity of 17P/Holmes before and after the 2007 outburst through optical and mid-infrared observations. We found that the nucleus was highly depleted in its near-surface icy component before the outburst but that it became activated after the 2007 outburst. Assuming a conventional 1 μm sized grain model, we derived a surface fractional active area of 0.58% ± 0.14% before the outburst whereas the area was enlarged by a factor of ∼50 after the 2007 outburst. We also found that large (≥1 mm) particles could be dominant in the dust tail observed around aphelion. Based on the size of the particles, the dust production rate was ≳170 kg s{sup –1} at a heliocentric distance of r{sub h} = 4.1 AU, suggesting that the nucleus was still active around the aphelion passage. The nucleus color was similar to that of the dust particles and average for a Jupiter-family comet but different from that of most Kuiper Belt objects, implying that color may be inherent to icy bodies in the solar system. On the basis of these results, we concluded that more than 76 m of surface material was blown off by the 2007 outburst.

  2. Comet 17P/Holmes: contrast in activity between before and after the 2007 outburst

    International Nuclear Information System (INIS)

    Ishiguro, Masateru; Kim, Yoonyoung; Warjurkar, Dhanraj S.; Ham, Ji-Beom; Kim, Junhan; Usui, Fumihiko; Vaubaillon, Jeremie J.; Ishihara, Daisuke; Hanayama, Hidekazu; Sarugaku, Yuki; Hasegawa, Sunao; Kasuga, Toshihiro; Watanabe, Jun-ichi; Pyo, Jeonghyun; Kuroda, Daisuke; Ootsubo, Takafumi; Sakamoto, Makoto; Narusawa, Shin-ya; Takahashi, Jun; Akisawa, Hiroki

    2013-01-01

    A Jupiter-family comet, 17P/Holmes, underwent outbursts in 1892 and 2007. In particular, the 2007 outburst is known as the greatest outburst over the past century. However, little is known about the activity before the outburst because it was unpredicted. In addition, the time evolution of the nuclear physical status has not been systematically studied. Here, we study the activity of 17P/Holmes before and after the 2007 outburst through optical and mid-infrared observations. We found that the nucleus was highly depleted in its near-surface icy component before the outburst but that it became activated after the 2007 outburst. Assuming a conventional 1 μm sized grain model, we derived a surface fractional active area of 0.58% ± 0.14% before the outburst whereas the area was enlarged by a factor of ∼50 after the 2007 outburst. We also found that large (≥1 mm) particles could be dominant in the dust tail observed around aphelion. Based on the size of the particles, the dust production rate was ≳170 kg s –1 at a heliocentric distance of r h = 4.1 AU, suggesting that the nucleus was still active around the aphelion passage. The nucleus color was similar to that of the dust particles and average for a Jupiter-family comet but different from that of most Kuiper Belt objects, implying that color may be inherent to icy bodies in the solar system. On the basis of these results, we concluded that more than 76 m of surface material was blown off by the 2007 outburst.

  3. On the morphology of outbursts of accreting millisecond X-ray pulsar Aquila X-1

    Science.gov (United States)

    Güngör, C.; Ekşi, K. Y.; Göğüş, E.

    2017-10-01

    We present the X-ray light curves of the last two outbursts - 2014 & 2016 - of the well known accreting millisecond X-ray pulsar (AMXP) Aquila X-1 using the monitor of all sky X-ray image (MAXI) observations in the 2-20 keV band. After calibrating the MAXI count rates to the all-sky monitor (ASM) level, we report that the 2016 outburst is the most energetic event of Aql X-1, ever observed from this source. We show that 2016 outburst is a member of the long-high class according to the classification presented by Güngör et al. with ˜ 68 cnt/s maximum flux and ˜ 60 days duration time and the previous outburst, 2014, belongs to the short-low class with ˜ 25 cnt/s maximum flux and ˜ 30 days duration time. In order to understand differences between outbursts, we investigate the possible dependence of the peak intensity to the quiescent duration leading to the outburst and find that the outbursts following longer quiescent episodes tend to reach higher peak energetic.

  4. Constraints from the UV delay in dwarf nova outbursts

    International Nuclear Information System (INIS)

    Meyer, F.; Meyer-Hofmeister, E.

    1989-01-01

    Observations of outbursts of the dwarf nova system VW Hydri show a delay of the rise of the UV flux with respect to that of the optical flux. We discuss the difficulties in modeling this feature in the context of the accretion disk instability and propose a modified limit cycle based on the same value of the frictional parameter α for the cool disk before transition and the hot disk afterwards. This is in contrast with the idea that α must be lower on the cool than on the hot branch. For the modeling of the disk evolution we further assume a continuing depletion of the disk after outburst, which results in a delay of the change over to the hot state during the following outburst

  5. VARIABLE ACCRETION OUTBURSTS IN PROTOSTELLAR EVOLUTION

    International Nuclear Information System (INIS)

    Bae, Jaehan; Hartmann, Lee; Zhu, Zhaohuan; Gammie, Charles

    2013-01-01

    We extend the one-dimensional, two-zone models of long-term protostellar disk evolution with infall of Zhu et al. to consider the potential effects of a finite viscosity in regions where the ionization is too low for the magnetorotational instability (MRI) to operate (the d ead zone ) . We find that the presence of a small but finite dead zone viscosity, as suggested by simulations of stratified disks with MRI-active outer layers, can trigger inside-out bursts of accretion, starting at or near the inner edge of the disk, instead of the previously found outside-in bursts with zero dead zone viscosity, which originate at a few AU in radius. These inside-out bursts of accretion bear a qualitative resemblance to the outburst behavior of one FU Ori object, V1515 Cyg, in contrast to the outside-in burst models, which more closely resemble the accretion events in FU Ori and V1057 Cyg. Our results suggest that the type and frequency of outbursts are potentially a probe of transport efficiency in the dead zone. Simulations must treat the inner disk regions, R ∼< 0.5 AU, to show the detailed time evolution of accretion outbursts in general and to observe the inside-out bursts in particular.

  6. VARIABLE ACCRETION OUTBURSTS IN PROTOSTELLAR EVOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Jaehan; Hartmann, Lee [Department of Astronomy, University of Michigan, 500 Church St., Ann Arbor, MI 48105 (United States); Zhu, Zhaohuan [Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Peyton Hall, Princeton, NJ 08544 (United States); Gammie, Charles, E-mail: jaehbae@umich.edu, E-mail: lhartm@umich.edu, E-mail: zhuzh@astro.princeton.edu, E-mail: gammie@illinois.edu [Department of Astronomy, University of Illinois Urbana-Champaign, 1002 W. Green St., Urbana, IL 61801 (United States)

    2013-02-20

    We extend the one-dimensional, two-zone models of long-term protostellar disk evolution with infall of Zhu et al. to consider the potential effects of a finite viscosity in regions where the ionization is too low for the magnetorotational instability (MRI) to operate (the {sup d}ead zone{sup )}. We find that the presence of a small but finite dead zone viscosity, as suggested by simulations of stratified disks with MRI-active outer layers, can trigger inside-out bursts of accretion, starting at or near the inner edge of the disk, instead of the previously found outside-in bursts with zero dead zone viscosity, which originate at a few AU in radius. These inside-out bursts of accretion bear a qualitative resemblance to the outburst behavior of one FU Ori object, V1515 Cyg, in contrast to the outside-in burst models, which more closely resemble the accretion events in FU Ori and V1057 Cyg. Our results suggest that the type and frequency of outbursts are potentially a probe of transport efficiency in the dead zone. Simulations must treat the inner disk regions, R {approx}< 0.5 AU, to show the detailed time evolution of accretion outbursts in general and to observe the inside-out bursts in particular.

  7. Evaluating transient performance of servo mechanisms by analysing stator current of PMSM

    Science.gov (United States)

    Zhang, Qing; Tan, Luyao; Xu, Guanghua

    2018-02-01

    Smooth running and rapid response are the desired performance goals for the transient motions of servo mechanisms. Because of the uncertain and unobservable transient behaviour of servo mechanisms, it is difficult to evaluate their transient performance. Under the effects of electromechanical coupling, the stator current signals of a permanent-magnet synchronous motor (PMSM) potentially contain the performance information regarding servo mechanisms in use. In this paper, a novel method based on analysing the stator current of the PMSM is proposed for quantifying the transient performance. First, a vector control model is constructed to simulate the stator current behaviour in the transient processes of consecutive speed changes, consecutive load changes, and intermittent start-stops. It is discovered that the amplitude and frequency of the stator current are modulated by the transient load torque and motor speed, respectively. The stator currents under different performance conditions are also simulated and compared. Then, the stator current is processed using a local means decomposition (LMD) algorithm to extract the instantaneous amplitude and instantaneous frequency. The sample entropy of the instantaneous amplitude, which reflects the complexity of the load torque variation, is calculated as a performance indicator of smooth running. The peak-to-peak value of the instantaneous frequency, which defines the range of the motor speed variation, is set as a performance indicator of rapid response. The proposed method is applied to both simulated data in an intermittent start-stops process and experimental data measured for a batch of servo turrets for turning lathes. The results show that the performance evaluations agree with the actual performance.

  8. Strong disk winds traced throughout outbursts in black-hole X-ray binaries.

    Science.gov (United States)

    Tetarenko, B E; Lasota, J-P; Heinke, C O; Dubus, G; Sivakoff, G R

    2018-02-01

    Recurring outbursts associated with matter flowing onto compact stellar remnants (such as black holes, neutron stars and white dwarfs) in close binary systems provide a way of constraining the poorly understood accretion process. The light curves of these outbursts are shaped by the efficiency of angular-momentum (and thus mass) transport in the accretion disks, which has traditionally been encoded in a viscosity parameter, α. Numerical simulations of the magneto-rotational instability that is believed to be the physical mechanism behind this transport yield values of α of roughly 0.1-0.2, consistent with values determined from observations of accreting white dwarfs. Equivalent viscosity parameters have hitherto not been estimated for disks around neutron stars or black holes. Here we report the results of an analysis of archival X-ray light curves of 21 outbursts in black-hole X-ray binaries. By applying a Bayesian approach to a model of accretion, we determine corresponding values of α of around 0.2-1.0. These high values may be interpreted as an indication either of a very high intrinsic rate of angular-momentum transport in the disk, which could be sustained by the magneto-rotational instability only if a large-scale magnetic field threads the disk, or that mass is being lost from the disk through substantial outflows, which strongly shape the outburst in the black-hole X-ray binary. The lack of correlation between our estimates of α and the accretion state of the binaries implies that such outflows can remove a substantial fraction of the disk mass in all accretion states and therefore suggests that the outflows correspond to magnetically driven disk winds rather than thermally driven ones, which require specific radiative conditions.

  9. Strong disk winds traced throughout outbursts in black-hole X-ray binaries

    Science.gov (United States)

    Tetarenko, B. E.; Lasota, J.-P.; Heinke, C. O.; Dubus, G.; Sivakoff, G. R.

    2018-02-01

    Recurring outbursts associated with matter flowing onto compact stellar remnants (such as black holes, neutron stars and white dwarfs) in close binary systems provide a way of constraining the poorly understood accretion process. The light curves of these outbursts are shaped by the efficiency of angular-momentum (and thus mass) transport in the accretion disks, which has traditionally been encoded in a viscosity parameter, α. Numerical simulations of the magneto-rotational instability that is believed to be the physical mechanism behind this transport yield values of α of roughly 0.1–0.2, consistent with values determined from observations of accreting white dwarfs. Equivalent viscosity parameters have hitherto not been estimated for disks around neutron stars or black holes. Here we report the results of an analysis of archival X-ray light curves of 21 outbursts in black-hole X-ray binaries. By applying a Bayesian approach to a model of accretion, we determine corresponding values of α of around 0.2–1.0. These high values may be interpreted as an indication either of a very high intrinsic rate of angular-momentum transport in the disk, which could be sustained by the magneto-rotational instability only if a large-scale magnetic field threads the disk, or that mass is being lost from the disk through substantial outflows, which strongly shape the outburst in the black-hole X-ray binary. The lack of correlation between our estimates of α and the accretion state of the binaries implies that such outflows can remove a substantial fraction of the disk mass in all accretion states and therefore suggests that the outflows correspond to magnetically driven disk winds rather than thermally driven ones, which require specific radiative conditions.

  10. Glacial lake inventory and lake outburst potential in Uzbekistan.

    Science.gov (United States)

    Petrov, Maxim A; Sabitov, Timur Y; Tomashevskaya, Irina G; Glazirin, Gleb E; Chernomorets, Sergey S; Savernyuk, Elena A; Tutubalina, Olga V; Petrakov, Dmitriy A; Sokolov, Leonid S; Dokukin, Mikhail D; Mountrakis, Giorgos; Ruiz-Villanueva, Virginia; Stoffel, Markus

    2017-08-15

    Climate change has been shown to increase the number of mountain lakes across various mountain ranges in the World. In Central Asia, and in particular on the territory of Uzbekistan, a detailed assessment of glacier lakes and their evolution over time is, however lacking. For this reason we created the first detailed inventory of mountain lakes of Uzbekistan based on recent (2002-2014) satellite observations using WorldView-2, SPOT5, and IKONOS imagery with a spatial resolution from 2 to 10m. This record was complemented with data from field studies of the last 50years. The previous data were mostly in the form of inventories of lakes, available in Soviet archives, and primarily included localized in-situ data. The inventory of mountain lakes presented here, by contrast, includes an overview of all lakes of the territory of Uzbekistan. Lakes were considered if they were located at altitudes above 1500m and if lakes had an area exceeding 100m 2 . As in other mountain regions of the World, the ongoing increase of air temperatures has led to an increase in lake number and area. Moreover, the frequency and overall number of lake outburst events have been on the rise as well. Therefore, we also present the first outburst assessment with an updated version of well-known approaches considering local climate features and event histories. As a result, out of the 242 lakes identified on the territory of Uzbekistan, 15% are considered prone to outburst, 10% of these lakes have been assigned low outburst potential and the remainder of the lakes have an average level of outburst potential. We conclude that the distribution of lakes by elevation shows a significant influence on lake area and hazard potential. No significant differences, by contrast, exist between the distribution of lake area, outburst potential, and lake location with respect to glaciers by regions. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Statistical analysis of dwarf nova outbursts

    International Nuclear Information System (INIS)

    Gicger, A.

    1987-01-01

    Correlation between maximum brightness, outburst width, lengths of preceding and following intervals has been studied for 14 dwarf novae (mostly from southern sky). Significant correlations (ρ ≥ 0.4) occur only in 16 per cent of cases, what confirms earlier results of Szkody and Mattei (1984). Global correlations have also been studied between mean photometric parameters and binary system parameters using a sample including over 30 objects. The most interesting result is the strong correlation (ρ = +0.94) between the orbital period and the outburst duration. It implies that the quantity α(z 0 /r) 2 is approximately constant for all dwarf novae. Using typical estimates for z 0 /r we get α = 0.2. 30 refs., 1 figs., 2 tabs. (author)

  12. Signs of η Carinae Outburst in Artifacts of Ancient Bolivia

    Science.gov (United States)

    Teames, Sallie

    Recent HST and X-ray photos of η Carinae reveal the bipolar gaseous lobes--the Homunculus Nebula--created by the star's "Great Eruption of 1843." From debris gases on the outskirts beyond the two gaseous lobes, astrophysicists surmise an earlier outburst. The 1999 Chandra X-ray photo of the horseshoe-shaped outer nebula surrounding the bipolar lobes indicates an earlier outburst occurring over a thousand years ago. Because η Carinae is so far south, it is entirely possible that the outburst would not have been seen by the Chinese and other observers in the northern hemisphere. Researchers are looking for possible recordings by early southern hemisphere observers. Pre-Incan artifacts excavated in Bolivia may provide an answer. In the script and artwork carvings on a monolith stone statue, an artifact of the Tiahuanacan culture, are signs possibly depicting the earlier outburst of η Carinae--the recordings of a star that suddenly brightened in their night sky. Two small stones from the same era and also found on the south shore of Lake Titicaca may also show depictions related to this brightening.

  13. Fuel element thermo-mechanical analysis during transient events using the FMS and FETMA codes

    International Nuclear Information System (INIS)

    Hernandez Lopez Hector; Hernandez Martinez Jose Luis; Ortiz Villafuerte Javier

    2005-01-01

    In the Instituto Nacional de Investigaciones Nucleares of Mexico, the Fuel Management System (FMS) software package has been used for long time to simulate the operation of a BWR nuclear power plant in steady state, as well as in transient events. To evaluate the fuel element thermo-mechanical performance during transient events, an interface between the FMS codes and our own Fuel Element Thermo Mechanical Analysis (FETMA) code is currently being developed and implemented. In this work, the results of the thermo-mechanical behavior of fuel rods in the hot channel during the simulation of transient events of a BWR nuclear power plant are shown. The transient events considered for this work are a load rejection and a feedwater control failure, which among the most important events that can occur in a BWR. The results showed that conditions leading to fuel rod failure at no time appeared for both events. Also, it is shown that a transient due load rejection is more demanding on terms of safety that the failure of a controller of the feedwater. (authors)

  14. Grazing Eclipsing Dwarf Nova CW Monocerotis: Dwarf Nova-Type Outburst in a Possible Intermediate Polar?

    Science.gov (United States)

    Kato, Taichi; Uemura, Makoto; Kiyota, Seiichiro; Tanabe, Kenji; Koizumi, Mitsuo; Kida, Mayumi; Nishi, Yuichi; Tanaka, Sawa; Ueoka, Rie; Yasui, Hideki; Vanmunster, Tonny; Nogami, Daisaku; Yamaoka, Hitoshi

    2003-04-01

    We observed the 2002 October-November outburst of the dwarf nova CW Mon.The outburst showed a clear signature of a premaximum halt, and a more rapid decline after reaching the outburst maximum.On two separate occasions, during the premaximum stage and near the outburst maximum, shallow eclipses were recorded. This finding confirms the previously suggested possibility of the grazing eclipsing nature of this system.The separate occurrence of the eclipses and the premaximum halt can be understood as being the result of a combination of a two-step ignition of an outburst and the inside-out propagation of the heating wave.We detected a coherent short-period (0.02549d) signal on two subsequent nights around the optical maximum.This signal was likely present during the maximum phase of the 2000 January outburst.We interpret this signal as being a signature of the intermediate polar (IP) type pulses.The rather strange outburst properties, strong and hard X-ray emission, and the low luminosity of the outburst maximum might be understood as a consequence of the supposed IP nature.The ratio between the suggested spin period and the orbital period, however, is rather unusual for a system having an orbital period of ˜ 0.176 d.

  15. The fourth outburst during the present active stage of symbiotic binary AG Dra

    Science.gov (United States)

    Galis, R.; Merc, J.; Vrastak, M.; Teyssier, F.; Lester, T.; Boyd, D.; Sims, W.; Leedjarv, L.

    2018-04-01

    The symbiotic system AG Dra regularly undergoes quiescent and active stages which consist of several outbursts repeating at about 360d interval (Galis et al. 2017, OEJV 180, 24). After seven years of flat quiescence following the 2006-08 major outbursts, in the late spring of 2015, AG Dra began rising again in brightness toward what appeared to be a new minor outburst (ATel #7582).

  16. Response of the human tympanic membrane to transient acoustic and mechanical stimuli: Preliminary results

    Science.gov (United States)

    Razavi, Payam; Ravicz, Michael E.; Dobrev, Ivo; Cheng, Jeffrey Tao; Furlong, Cosme; Rosowski, John J.

    2016-01-01

    The response of the tympanic membrane (TM) to transient environmental sounds and the contributions of different parts of the TM to middle-ear sound transmission were investigated by measuring the TM response to global transients (acoustic clicks) and to local transients (mechanical impulses) applied to the umbo and various locations on the TM. A lightly-fixed human temporal bone was prepared by removing the ear canal, inner ear, and stapes, leaving the incus, malleus, and TM intact. Motion of nearly the entire TM was measured by a digital holography system with a high speed camera at a rate of 42 000 frames per second, giving a temporal resolution of <24 μs for the duration of the TM response. The entire TM responded nearly instantaneously to acoustic transient stimuli, though the peak displacement and decay time constant varied with location. With local mechanical transients, the TM responded first locally at the site of stimulation, and the response spread approximately symmetrically and circumferentially around the umbo and manubrium. Acoustic and mechanical transients provide distinct and complementary stimuli for the study of TM response. Spatial variations in decay and rate of spread of response imply local variations in TM stiffness, mass, and damping. PMID:26880098

  17. Supergiant Fast X-ray Transients with Swift: spectroscopic and temporal properties

    OpenAIRE

    Romano, P.; Mangano, V.; Ducci, L.; Esposito, P.; Farinelli, R.; Ceccobello, C.; Vercellone, S.; Burrows, D. N.; Kennea, J. A.; Krimm, H. A.; Gehrels, N.

    2012-01-01

    Supergiant fast X-ray transients (SFXTs) are a class of high-mass X-ray binaries with possible counterparts in the high energy gamma rays. The Swift SFXT Project has conducted a systematic investigation of the properties of SFTXs on timescales ranging from minutes to years and in several intensity states (from bright flares, to intermediate intensity states, and down to almost quiescence). We also performed broad-band spectroscopy of outbursts, and intensity-selected spectroscopy outside of o...

  18. Transient resetting: a novel mechanism for synchrony and its biological examples.

    Directory of Open Access Journals (Sweden)

    Chunguang Li

    2006-08-01

    Full Text Available The study of synchronization in biological systems is essential for the understanding of the rhythmic phenomena of living organisms at both molecular and cellular levels. In this paper, by using simple dynamical systems theory, we present a novel mechanism, named transient resetting, for the synchronization of uncoupled biological oscillators with stimuli. This mechanism not only can unify and extend many existing results on (deterministic and stochastic stimulus-induced synchrony, but also may actually play an important role in biological rhythms. We argue that transient resetting is a possible mechanism for the synchronization in many biological organisms, which might also be further used in the medical therapy of rhythmic disorders. Examples of the synchronization of neural and circadian oscillators as well as a chaotic neuron model are presented to verify our hypothesis.

  19. Mechanical behavior of fast reactor fuel pin cladding subjected to simulated overpower transients

    International Nuclear Information System (INIS)

    Johnson, G.D.; Hunter, C.W.

    1978-06-01

    Cladding mechanical property data for analysis and prediction of fuel pin transient behavior were obtained under experimental conditions in which the temperature ramps of reactor transients were simulated. All cladding specimens were 20% CW Type 316 stainless steel and were cut from EBR-II irradiated fuel pins. It was determined that irradiation degraded the cladding ductility and failure strength. Specimens that had been adjacent to the fuel exhibited the poorest properties. Correlations were developed to describe the effect of neutron fluence on the mechanical behavior of the cladding. Metallographic examinations were conducted to characterize the failure mode and to establish the nature of internal and external surface corrosion. Various mechanisms for the fuel adjacency effect were examined and results for helium concentration profiles were presented. Results from the simulated transient tests were compared with TREAT test results

  20. GW LIBRAE: STILL HOT EIGHT YEARS POST-OUTBURST

    Energy Technology Data Exchange (ETDEWEB)

    Szkody, Paula; Mukadam, Anjum S. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Gänsicke, Boris T.; Chote, Paul; Toloza, Odette [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Nelson, Peter; Myers, Gordon; Waagen, Elizabeth O. [AAVSO, 48 Bay State Road, Cambridge, MA 02138 (United States); Sion, Edward M. [Department of Astrophysics and Planetary Science, Villanova University, Villanova, PA 19085 (United States); Sullivan, Denis J. [School of Chemical and Physical Sciences, Victoria University of Wellington, P.O. Box 600, Wellington (New Zealand); Townsley, Dean M., E-mail: szkody@astro.washington.edu [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL 35487 (United States)

    2016-08-01

    We report continued Hubble Space Telescope ( HST ) ultraviolet spectra and ground-based optical photometry and spectroscopy of GW Librae eight years after its largest known dwarf nova outburst in 2007. This represents the longest cooling timescale measured for any dwarf nova. The spectra reveal that the white dwarf still remains about 3000 K hotter than its quiescent value. Both ultraviolet and optical light curves show a short period of 364–373 s, similar to one of the non-radial pulsation periods present for years prior to the outburst, and with a similar large UV/optical amplitude ratio. A large modulation at a period of 2 hr (also similar to that observed prior to outburst) is present in the optical data preceding and during the HST observations, but the satellite observation intervals did not cover the peaks of the optical modulation, and so it is not possible to determine its corresponding UV amplitude. The similarity of the short and long periods to quiescent values implies that the pulsating, fast spinning white dwarf in GW Lib may finally be nearing its quiescent configuration.

  1. ABSENCE OF SIGNIFICANT COOL DISKS IN YOUNG STELLAR OBJECTS EXHIBITING REPETITIVE OPTICAL OUTBURSTS

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hauyu Baobab; Hirano, Naomi; Takami, Michihiro; Dong, Ruobing [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 106, Taiwan (China); Galván-Madrid, Roberto; Rodríguez, Luis F.; Carrasco-González, Carlos [Instituto de Radioastronomía y Astrofísica, UNAM, A.P. 3-72, Xangari, Morelia, 58089 (Mexico); Vorobyov, Eduard I. [Department of Astrophysics, University of Vienna, Tuerkenschanzstrasse 17, A-1180, Vienna (Austria); Kóspál, Ágnes [Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, P.O. Box 67, 1525 Budapest (Hungary); Dunham, Michael M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 78, Cambridge, MA 02138 (United States); Henning, Thomas [Max-Planck-Institut für Astronomie Königstuhl, 17 D-69117 Heidelberg (Germany); Hashimoto, Jun [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 Japan (Japan); Hasegawa, Yasuhiro, E-mail: baobabyoo@gmail.com [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2016-01-10

    We report Submillimeter Array 1.3 mm high angular resolution observations toward the four EXor-type outbursting young stellar objects VY Tau, V1118 Ori, V1143 Ori, and NY Ori. The data mostly show low dust masses M{sub dust} in the associated circumstellar disks. Among the sources, NY Ori possesses a relatively massive disk with M{sub dust} ∼ 9 × 10{sup −4}M{sub ⊙}. V1118 Ori has a marginal detection equivalent to M{sub dust} ∼ 6 × 10{sup −5}M{sub ⊙}. V1143 Ori has a non-detection also equivalent to M{sub dust} < 6 × 10{sup −5}M{sub ⊙}. For the nearest source, VY Tau, we get a surprising non-detection that provides a stringent upper limit M{sub dust} < 6 × 10{sup −6}M{sub ⊙}. We interpret our findings as suggesting that the gas and dust reservoirs that feed the short-duration, repetitive optical outbursts seen in some EXors may be limited to the small-scale, innermost region of their circumstellar disks. This hot dust may have escaped our detection limits. Follow-up, more sensitive millimeter observations are needed to improve our understanding of the triggering mechanisms of EXor-type outbursts.

  2. New outburst of the symbiotic nova AG Pegasi after 165 yr

    Science.gov (United States)

    Skopal, A.; Shugarov, S. Yu.; Sekeráš, M.; Wolf, M.; Tarasova, T. N.; Teyssier, F.; Fujii, M.; Guarro, J.; Garde, O.; Graham, K.; Lester, T.; Bouttard, V.; Lemoult, T.; Sollecchia, U.; Montier, J.; Boyd, D.

    2017-08-01

    Context. AG Peg is known as the slowest symbiotic nova, which experienced its nova-like outburst around 1850. After 165 yr, during June of 2015, it erupted again showing characteristics of the Z And-type outburst. Aims: The primary objective is to determine basic characteristics, the nature and type of the 2015 outburst of AG Peg. Methods: We achieved this aim by modelling the spectral energy distribution using low-resolution spectroscopy (330-750 nm; R = 500-1000), medium-resolution spectroscopy (420-720 nm; R 11 000), and UBVRCIC photometry covering the 2015 outburst with a high cadence. Optical observations were complemented with the archival HST and FUSE spectra from the preceding quiescence. Results: During the outburst, the luminosity of the hot component was in the range of 2-11 × 1037 (d/ 0.8 kpc)2 erg s-1, being in correlation with the light curve (LC) profile. To generate the maximum luminosity by the hydrogen burning, the white dwarf (WD) had to accrete at 3 × 10-7 M⊙ yr-1, which exceeds the stable-burning limit and thus led to blowing optically thick wind from the WD. We determined its mass-loss rate to a few × 10-6 M⊙ yr-1. At the high temperature of the ionising source, 1.5-2.3 × 105 K, the wind converted a fraction of the WD's photospheric radiation into the nebular emission that dominated the optical. A one order of magnitude increase of the emission measure, from a few × 1059 (d/ 0.8 kpc)2 cm-3 during quiescence, to a few × 1060 (d/ 0.8 kpc)2 cm-3 during the outburst, caused a 2 mag brightening in the LC, which is classified as the Z And-type of the outburst. Conclusions: The very high nebular emission and the presence of a disk-like H I region encompassing the WD, as indicated by a significant broadening and high flux of the Raman-scattered O vi 6825 Å line during the outburst, is consistent with the ionisation structure of hot components in symbiotic stars during active phases. Full Table 1 and Table 6 are only available at the CDS are

  3. Experimental Research on the Impactive Dynamic Effect of Gas-Pulverized Coal of Coal and Gas Outburst

    Directory of Open Access Journals (Sweden)

    Haitao Sun

    2018-03-01

    Full Text Available Coal and gas outburst is one of the major serious natural disasters during underground coal, and the shock air flow produced by outburst has a huge threat on the mine safety. In order to study the two-phase flow of a mixture of pulverized coal and gas of a mixture of pulverized coal and gas migration properties and its shock effect during the process of coal and gas outburst, the coal samples of the outburst coal seam in Yuyang Coal Mine, Chongqing, China were selected as the experimental subjects. By using the self-developed coal and gas outburst simulation test device, we simulated the law of two-phase flow of a mixture of pulverized coal and gas in the roadway network where outburst happened. The results showed that the air in the roadway around the outburst port is disturbed by the shock wave, where the pressure and temperature are abruptly changed. For the initial gas pressure of 0.35 MPa, the air pressure in different locations of the roadway fluctuated and eventually remain stable, and the overpressure of the outburst shock wave was about 20~35 kPa. The overpressure in the main roadway and the distance from the outburst port showed a decreasing trend. The highest value of temperature in the roadway increased by 0.25 °C and the highest value of gas concentration reached 38.12% during the experiment. With the action of shock air flow, the pulverized coal transportation in the roadway could be roughly divided into three stages, which are the accelerated movement stage, decelerated movement stage and the particle settling stage respectively. Total of 180.7 kg pulverized coal of outburst in this experiment were erupted, and most of them were accumulated in the main roadway. Through the analysis of the law of outburst shock wave propagation, a shock wave propagation model considering gas desorption efficiency was established. The relationships of shock wave overpressure and outburst intensity, gas desorption rate, initial gas pressure, cross

  4. Development of a web-based, underground coalmine gas outburst information management system

    Energy Technology Data Exchange (ETDEWEB)

    Naj Aziz; Richard Caladine; Lucia Tome; Ken Cram; Devendra Vyas [University of Wollongong, NSW (Australia)

    2007-04-15

    The primary objective of this project was to develop an online coal mine outburst information management system to provide the coal mining industry with the necessary information and knowledge on outbursts via the World Wide Web. The Website has been constructed using the standard web format. Access to the site is by standard web browsers. The address of the site is http://www.uow.edu.au/eng/outburst. The website has 85 conference papers which were held in Australia, dating as far back as the 1980's, various seminar presentations, more than 250 references, a limited but important collection of international papers, direct links to ACARP and NERRDC publication lists, links to several leading organisations of particular interest in mine gas and outburst control. These links include both private and government organisations, and a forum for discussion.

  5. HUBBLE SPACE TELESCOPE AND GROUND-BASED OBSERVATIONS OF V455 ANDROMEDAE POST-OUTBURST

    Energy Technology Data Exchange (ETDEWEB)

    Szkody, Paula; Mukadam, Anjum S.; Brown, Justin; Funkhouser, Kelsey [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Gänsicke, Boris T. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Henden, Arne [AAVSO, 49 Bay State Road, Cambridge, MA 02138 (United States); Sion, Edward M. [Department of Astronomy and Astrophysics, Villanova University, Villanova, PA 19085 (United States); Townsley, Dean M. [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL 35487 (United States); Christian, Damian [Department of Physics and Astronomy, California State University, Northridge, CA 91330 (United States); Falcon, Ross E. [Department of Astronomy, University of Texas, Austin, TX 78712 (United States); Pyrzas, Stylianos, E-mail: szkody@astro.washington.edu, E-mail: anjum@astro.washington.edu, E-mail: boris.gaensicke@warwick.ac.uk, E-mail: arne@aavso.org, E-mail: edward.sion@villanova.edu, E-mail: Dean.M.Townsley@ua.edu, E-mail: damian.christian@csun.edu, E-mail: cylver@astro.as.utexas.edu, E-mail: stylianos.pyrzas@gmail.com [Instituto de Astronomia, Universidad Catolica del Norte, Avenida Angamos 0619, Antofagasta (Chile)

    2013-09-20

    Hubble Space Telescope spectra obtained in 2010 and 2011, 3 and 4 yr after the large amplitude dwarf nova outburst of V455 And, were combined with optical photometry and spectra to study the cooling of the white dwarf, its spin, and possible pulsation periods after the outburst. The modeling of the ultraviolet (UV) spectra shows that the white dwarf temperature remains ∼600 K hotter than its quiescent value at 3 yr post-outburst, and still a few hundred degrees hotter at 4 yr post-outburst. The white dwarf spin at 67.6 s and its second harmonic at 33.8 s are visible in the optical within a month of outburst and are obvious in the later UV observations in the shortest wavelength continuum and the UV emission lines, indicating an origin in high-temperature regions near the accretion curtains. The UV light curves folded on the spin period show a double-humped modulation consistent with two-pole accretion. The optical photometry 2 yr after outburst shows a group of frequencies present at shorter periods (250-263 s) than the periods ascribed to pulsation at quiescence, and these gradually shift toward the quiescent frequencies (300-360 s) as time progresses past outburst. The most surprising result is that the frequencies near this period in the UV data are only prominent in the emission lines, not the UV continuum, implying an origin away from the white dwarf photosphere. Thus, the connection of this group of periods with non-radial pulsations of the white dwarf remains elusive.

  6. Modeling AGN outbursts from supermassive black hole binaries

    Directory of Open Access Journals (Sweden)

    Tanaka T.

    2012-12-01

    Full Text Available When galaxies merge to assemble more massive galaxies, their nuclear supermassive black holes (SMBHs should form bound binaries. As these interact with their stellar and gaseous environments, they will become increasingly compact, culminating in inspiral and coalescence through the emission of gravitational radiation. Because galaxy mergers and interactions are also thought to fuel star formation and nuclear black hole activity, it is plausible that such binaries would lie in gas-rich environments and power active galactic nuclei (AGN. The primary difference is that these binaries have gravitational potentials that vary – through their orbital motion as well as their orbital evolution – on humanly tractable timescales, and are thus excellent candidates to give rise to coherent AGN variability in the form of outbursts and recurrent transients. Although such electromagnetic signatures would be ideally observed concomitantly with the binary’s gravitational-wave signatures, they are also likely to be discovered serendipitously in wide-field, high-cadence surveys; some may even be confused for stellar tidal disruption events. I discuss several types of possible “smoking gun” AGN signatures caused by the peculiar geometry predicted for accretion disks around SMBH binaries.

  7. INTEGRAL finds renewed X-ray activity of the Neutron star X-ray transient SAX J1750.8-2900

    DEFF Research Database (Denmark)

    Sanchez-Fernandez, Celia; Chenevez, Jérôme; Kuulkers, Erik

    2015-01-01

    INTEGRAL Galactic bulge monitoring observations (ATel #438) on UT 13 September 2015 18:50-22:32 reveal renewed X-ray activity from the low-mass X-ray binary transient and Type I X-ray burster SAX J1750.8-2900 (IAU Circ. #6597). The last outburst from this source was reported in 2011 (ATels #3170,...

  8. An inventory of historical glacial lake outburst floods in the Himalayas based on remote sensing observations and geomorphological analysis

    Science.gov (United States)

    Nie, Yong; Liu, Qiao; Wang, Jida; Zhang, Yili; Sheng, Yongwei; Liu, Shiyin

    2018-05-01

    Glacial lake outburst floods (GLOFs) are a unique type of natural hazard in the cryosphere that may result in catastrophic fatalities and damages. The Himalayas are known as one of the world's most GLOF-vulnerable zones. Effective hazard assessments and risk management require a thorough inventory of historical GLOF events across the Himalayas, which is hitherto absent. Existing studies imply that numerous historical GLOF events are contentious because of discrepant geographic coordinates, names, or outburst time, requiring further verifications. This study reviews and verifies over 60 historical GLOF events across the Himalayas using a comprehensive method that combines literature documentations, archival remote sensing observations, geomorphological analysis, and field investigations. As a result, three unreported GLOF events were discovered from remote sensing images and geomorphological analysis. Eleven suspicious events were identified and suggested to be excluded. The properties of five outburst lakes, i.e., Degaco, Chongbaxia Tsho, Geiqu, Lemthang Tsho, and a lake on Tshojo Glacier, were corrected or updated. A total of 51 GLOF events were verified to be convincing, and these outburst lakes were classified into three categories according to their statuses in the past decades, namely disappeared (12), stable (30), and expanding (9). Statistics of the verified GLOF events show that GLOF tended to occur between April and October in the Himalayas. We suggest that more attention should be paid to rapidly expanding glacial lakes with high possibility of repetitive outbursts. This study also demonstrates the effectiveness of integrating remote sensing and geomorphic interpretations in identifying and verifying GLOF events in remote alpine environments. This inventory of GLOFs with a range of critical attributes (e.g., locations, time, and mechanisms) will benefit the continuous monitoring and prediction of potentially dangerous glacial lakes and contribute to

  9. The accretion-heated crust of the transiently accreting 11-Hz X-ray pulsar in the globular cluster Terzan 5

    NARCIS (Netherlands)

    Degenaar, N.; Wijnands, R.

    2011-01-01

    We report on a Chandra Director’s Discretionary Time observation of the globular cluster Terzan 5, carried out ∼7 weeks after the cessation of the 2010 outburst of the newly discovered transiently accreting 11-Hz X-ray pulsar. We detect a thermal spectrum that can be fitted with a neutron star

  10. XMM-Newton and Swift spectroscopy of the newly discovered very faint X-ray transient IGR J17494-3030

    NARCIS (Netherlands)

    Armas Padilla, M.; Wijnands, R.; Degenaar, N.

    2013-01-01

    A growing group of low-mass X-ray binaries are found to be accreting at very faint X-ray luminosities of <1036 erg s−1 (2-10 keV). One such system is the new X-ray transient IGR J17494-3030. We present Swift and XMM-Newton observations obtained during its 2012 discovery outburst. The Swift

  11. Electronically controlled mechanical seal for aerospace applications--Part 2: Transient tests

    Science.gov (United States)

    Wolff, Paul J.; Salant, Richard F.

    1995-01-01

    An electronically controlled mechanical seal for use as the purge gas seal in a liquid oxygen turbopump has been fabricated and tested under transient operating conditions. The thickness of the lubricating film is controlled by adjusting the coning of the carbon face. This is accomplished by applying a voltage to a piezoelectric actuator to which the carbon face is bonded. The seal has been operated with a closed-loop control system that utilizes either the leakage rate or seal face temperature as the feedback. Both speed and pressure transients have been imposed on the seal. The transient tests have demonstrated that the seal is capable of maintaing low leakage rates while limiting face temperatures.

  12. Transient thermal-mechanical coupling behavior analysis of mechanical seals during start-up operation

    Science.gov (United States)

    Gao, B. C.; Meng, X. K.; Shen, M. X.; Peng, X. D.

    2016-05-01

    A transient thermal-mechanical coupling model for a contacting mechanical seal during start-up has been developed. It takes into consideration the coupling relationship among thermal-mechanical deformation, film thickness, temperature and heat generation. The finite element method and multi-iteration technology are applied to solve the temperature distribution and thermal-mechanical deformation as well as their evolution behavior. Results show that the seal gap transforms from negative coning to positive coning and the contact area of the mechanical seal gradually decreases during start-up. The location of the maximum temperature and maximum contact pressure move from the outer diameter to inside diameter. The heat generation and the friction torque increase sharply at first and then decrease. Meanwhile, the contact force decreases and the fluid film force and leakage rate increase.

  13. Infrared variability of the BL lacertae object OJ287 since its outburst in 1983

    International Nuclear Information System (INIS)

    Gear, W.K.; Robson, E.I.; Brown, L.M.J.

    1986-01-01

    In early 1983, OJ287 was seen to undergo an outburst in its optical and infrared emission. The authors have monitored the near-infrared emission since the outburst. The fluxes have fluctuated considerably, with the lowest recordings being an order of magnitude less than those measured during the outburst. An excellent correlation between infrared flux and spectral index has been found; as the source gets fainter the spectrum gets steeper, and vice versa. (author)

  14. Magnetic field interpretation for the outburst of CH Cygni

    International Nuclear Information System (INIS)

    Wdowiak, T.J.

    1977-01-01

    The possible appearance of kilogauss magnetic structure in and above the photosphere of a red giant during helium-shell flash is examined as a mechanism for the outburst of the apparently single star, CH Cyg. Strong magnetic fields created by dynamo action in a temporary connection zone of a red giant core, by virtue of their intrinsic buoyancy, would rise quickly to the stellar surface. It is suggested that if the field is coupled with the large-scale convective structure of the envelope, the energy contained and rate of release would be sufficient to produce the emission features of the spectrum of CH Cyg

  15. X-Ray Timing and Spectral Observations of Galactic Black Hole Candidate XTE J1550--564 During Outburst

    Energy Technology Data Exchange (ETDEWEB)

    Reilly, Kaice T

    2002-12-11

    Soft X-ray transients (SXTs), a sub-class of low-mass X-ray binaries (LMXBs), provide a unique opportunity to test General Relativity and to probe fundamental physics under conditions terrestrially unattainable. SXT outbursts are of great interest because they allow the study of LMXBs under a wide range of accretion rates. The majority of known SXTs contain black holes, therefore SXT outbursts are key to understanding accretion physics around black holes and in active galactic nuclei, which are thought to contain supermassive, M {approx} 10{sup 6} - 10{sup 10} M{circle_dot}, where M{circle_dot} is one solar mass, central compact objects. These compact objects are most likely black holes, which exhibit, on a much larger scale, accretion physics similar to that around black holes in SXTs. In this work, the timing and spectral properties of the SXT and microquasar XTE J1550-564 during outburst are studied. Observations made by the Unconventional Stellar Aspect (USA) Experiment on board the Advanced Research and Global Observation Satellite (ARGOS) are emphasized. USA data show a low-frequency quasi-periodic oscillation (LFQPO) with a centroid frequency that tends to increase with increasing USA flux and a fractional rms amplitude which is correlated with the USA hardness ratio (4-16 keV/1-4 keV). Several high-frequency quasi-periodic oscillations (HFQPOs) were detected by the Rossi X-ray Timing Explorer (RXTE), during periods where the LFQPO is seen to be weakening or not detectable at all. The evolution of the USA hardness ratio with time and source flux is examined. The hardness-intensity diagram shows counterclockwise cyclical evolution and possibly indicates the presence of two independent accretion flows: a geometrically thin, optically thick accretion disk and a hot sub-Keplerian flow.

  16. Multicolor Photometry of 1SWASP J162117.36+441254.2 during the 2016 Outburst

    Science.gov (United States)

    Pit, N. V.; Pavlenko, E. P.; Antonyuk, K. A.; Belan, S. P.

    2017-06-01

    We present preliminary results of BVRcIc photometric observations of 1SWASP J162117.36+441254.2 during the 2016 outburst. Observations were carried out at 1.25-m telescope located in Crimean Astrophysical Observatory. Previously this star was thought as eclipsing variable of the W UMa-type until the outburst, but with the help of numerous worldwide observations this object was classified as the long-term dwarf nova. Our findings demonstrate the dramatic changes of the light curves profile in all color bands during the outburst. This can be interpreted as the presence of erupted accretion disk at the early stages of outburst and the emergence of ellipsoid effect of the secondary component of the system at a later stage.

  17. Disc-jet Coupling in the 2009 Outburst of the Black Hole Candidate H1743-322

    Science.gov (United States)

    Miller-Jones, J. C. A.; Sivakoff, G. R.; Altamirano, D.; Coriat, M.; Corbel, S.; Dhawan, V.; Krimm, H. A.; Remillard, R. A.; Rupen, M. P.; Russell, D. M.; hide

    2012-01-01

    We present an intensive radio and X-ray monitoring campaign on the 2009 outburst of the Galactic black hole candidate X-ray binary H1743-322. With the high angular resolution of the Very Long Baseline Array, we resolve the jet ejection event and measure the proper motions of the jet ejecta relative to the position of the compact core jets detected at the beginning of the outburst. This allows us to accurately couple the moment when the jet ejection event occurred with X-ray spectral and timing signatures. We find that X-ray timing signatures are the best diagnostic of the jet ejection event in this outburst, which occurred as the X-ray variability began to decrease and the Type C quasi-periodic oscillations disappeared from the X-ray power density spectrum. However, this sequence of events does not appear to be replicated in all black hole X-ray binary outbursts, even within an individual source. In our observations of H1743-322, the ejection was contemporaneous with a quenching of the radio emission, prior to the start of the major radio flare. This contradicts previous assumptions that the onset of the radio flare marks the moment of ejection. The jet speed appears to vary between outbursts with a positive correlation outburst luminosity. The compact core radio jet reactivated on transition to the hard intermediate state at the end of the outburst and not when the source reached the low hard spectral state. Comparison with the known near-infrared behaviour of the compact jets suggests a gradual evolution of the compact jet power over a few days near beginning the and end of an outburst

  18. Underlying mechanisms of transient luminous events: a review

    OpenAIRE

    V. V. Surkov; M. Hayakawa

    2012-01-01

    Transient luminous events (TLEs) occasionally observed above a strong thunderstorm system have been the subject of a great deal of research during recent years. The main goal of this review is to introduce readers to recent theories of electrodynamics processes associated with TLEs. We examine the simplest versions of these theories in order to make their physics as transparent as possible. The study is begun with the conventional mechanism for air breakdown at stratospheric...

  19. FORMATION AND RECONDENSATION OF COMPLEX ORGANIC MOLECULES DURING PROTOSTELLAR LUMINOSITY OUTBURSTS

    International Nuclear Information System (INIS)

    Taquet, Vianney; Wirström, Eva S.; Charnley, Steven B.

    2016-01-01

    During the formation of stars, the accretion of surrounding material toward the central object is thought to undergo strong luminosity outbursts followed by long periods of relative quiescence, even at the early stages of star formation when the protostar is still embedded in a large envelope. We investigated the gas-phase formation and recondensation of the complex organic molecules (COMs) di-methyl ether and methyl formate, induced by sudden ice evaporation processes occurring during luminosity outbursts of different amplitudes in protostellar envelopes. For this purpose, we updated a gas-phase chemical network forming COMs in which ammonia plays a key role. The model calculations presented here demonstrate that ion–molecule reactions alone could account for the observed presence of di-methyl ether and methyl formate in a large fraction of protostellar cores without recourse to grain-surface chemistry, although they depend on uncertain ice abundances and gas-phase reaction branching ratios. In spite of the short outburst timescales of about 100 years, abundance ratios of the considered species higher than 10% with respect to methanol are predicted during outbursts due to their low binding energies relative to water and methanol which delay their recondensation during cooling. Although the current luminosity of most embedded protostars would be too low to produce complex organics in the hot-core regions that are observable with current sub-millimetric interferometers, previous luminosity outburst events would induce the formation of COMs in extended regions of protostellar envelopes with sizes increasing by up to one order of magnitude

  20. Formation and Recondensation of Complex Organic Molecules during Protostellar Luminosity Outbursts

    Science.gov (United States)

    Taquet, Vianney; Wirström, Eva S.; Charnley, Steven B.

    2016-04-01

    During the formation of stars, the accretion of surrounding material toward the central object is thought to undergo strong luminosity outbursts followed by long periods of relative quiescence, even at the early stages of star formation when the protostar is still embedded in a large envelope. We investigated the gas-phase formation and recondensation of the complex organic molecules (COMs) di-methyl ether and methyl formate, induced by sudden ice evaporation processes occurring during luminosity outbursts of different amplitudes in protostellar envelopes. For this purpose, we updated a gas-phase chemical network forming COMs in which ammonia plays a key role. The model calculations presented here demonstrate that ion-molecule reactions alone could account for the observed presence of di-methyl ether and methyl formate in a large fraction of protostellar cores without recourse to grain-surface chemistry, although they depend on uncertain ice abundances and gas-phase reaction branching ratios. In spite of the short outburst timescales of about 100 years, abundance ratios of the considered species higher than 10% with respect to methanol are predicted during outbursts due to their low binding energies relative to water and methanol which delay their recondensation during cooling. Although the current luminosity of most embedded protostars would be too low to produce complex organics in the hot-core regions that are observable with current sub-millimetric interferometers, previous luminosity outburst events would induce the formation of COMs in extended regions of protostellar envelopes with sizes increasing by up to one order of magnitude.

  1. FORMATION AND RECONDENSATION OF COMPLEX ORGANIC MOLECULES DURING PROTOSTELLAR LUMINOSITY OUTBURSTS

    Energy Technology Data Exchange (ETDEWEB)

    Taquet, Vianney [Leiden Observatory, Leiden University, P.O. Box 9513, 2300-RA Leiden (Netherlands); Wirström, Eva S. [Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-439 92 Onsala (Sweden); Charnley, Steven B. [Astrochemistry Laboratory and The Goddard Center for Astrobiology, Mailstop 691, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20770 (United States)

    2016-04-10

    During the formation of stars, the accretion of surrounding material toward the central object is thought to undergo strong luminosity outbursts followed by long periods of relative quiescence, even at the early stages of star formation when the protostar is still embedded in a large envelope. We investigated the gas-phase formation and recondensation of the complex organic molecules (COMs) di-methyl ether and methyl formate, induced by sudden ice evaporation processes occurring during luminosity outbursts of different amplitudes in protostellar envelopes. For this purpose, we updated a gas-phase chemical network forming COMs in which ammonia plays a key role. The model calculations presented here demonstrate that ion–molecule reactions alone could account for the observed presence of di-methyl ether and methyl formate in a large fraction of protostellar cores without recourse to grain-surface chemistry, although they depend on uncertain ice abundances and gas-phase reaction branching ratios. In spite of the short outburst timescales of about 100 years, abundance ratios of the considered species higher than 10% with respect to methanol are predicted during outbursts due to their low binding energies relative to water and methanol which delay their recondensation during cooling. Although the current luminosity of most embedded protostars would be too low to produce complex organics in the hot-core regions that are observable with current sub-millimetric interferometers, previous luminosity outburst events would induce the formation of COMs in extended regions of protostellar envelopes with sizes increasing by up to one order of magnitude.

  2. EXor OUTBURSTS FROM DISK AMPLIFICATION OF STELLAR MAGNETIC CYCLES

    Energy Technology Data Exchange (ETDEWEB)

    Armitage, Philip J., E-mail: pja@jilau1.colorado.edu [JILA, University of Colorado and NIST, 440 UCB, Boulder, CO 80309-0440 (United States)

    2016-12-20

    EXor outbursts—moderate-amplitude disk accretion events observed in Class I and Class II protostellar sources—have timescales and amplitudes that are consistent with the viscous accumulation and release of gas in the inner disk near the dead zone boundary. We suggest that outbursts are indirectly triggered by stellar dynamo cycles, via poloidal magnetic flux that diffuses radially outward through the disk. Interior to the dead zone the strength of the net field modulates the efficiency of angular momentum transport by the magnetorotational instability. In the dead zone changes in the polarity of the net field may lead to stronger outbursts because of the dominant role of the Hall effect in this region of the disk. At the level of simple estimates we show that changes to kG-strength stellar fields could stimulate disk outbursts on 0.1 au scales, though this optimistic conclusion depends upon the uncertain efficiency of net flux transport through the inner disk. The model predicts a close association between observational tracers of stellar magnetic activity and EXor events.

  3. X-ray Transient Sources (Multifrequency Laboratories The Case of the Prototype A0535+26/HDE 245770

    Directory of Open Access Journals (Sweden)

    F. Giovannelli

    2011-01-01

    Full Text Available The goal of this paper is to discuss the behaviour of the X-ray transient source A0535+26 which is considered for historical reasons and for the huge amount of multifrequency data, spread over a period of 35 years, as the prototype of this class of objects. Transient sources are formed by a Be star — the primary — and a neutron star X-ray pulsar — the secondary — and constitute a sub-class of X-ray binary systems. We will emphasize the discovery of low-energy indicators of high-energy processes. They are UBVRI magnitudes and Balmer lines of the optical companion. Particular unusual activity of the primary star — usually at the periastron passage of the neutron star – indicates that an X-ray flare is drawing near. The shape and intensity of X-ray outbursts are dependent on the strength of the activity of the primary. We derive the optical orbital period of the system as 110.856 ± 0.02 days. By using the optical flare of December 5, 1981 (here after 811205-E that triggered the subsequent X-ray outburst of December 13, 1981, we derive the ephemeris of the system as JD Popt−outb = JD0 (2, 444, 944 ± n(110.856 ± 0.02. Thus the passage of the neutron star at the periastron occurs with a periodicity of 110.856 ± 0.02 days and the different kinds of X-ray outbursts of A0535+26 — following the definitions reported in the review by Giovannelli & Sabau-Graziati (1992 — occur just after ∼ 8 days. The delay between optical and X-ray outbursts is just the transit time of the material coming out from the optical companion to reach the neutron star X-ray pulsar. The occurrence of X-ray “normal outbursts”, “anomalous outbursts” or “casual outbursts” is dependent on the activity of the Be star: “quiet state: steady stellar wind”, “excited state: stellar wind plus puffs of material”, and “expulsion of a shell”, respectively. In the latter case, the primary manifests a strong optical activity and the consequent strong

  4. The Chandra Dust-scattering Halo of Galactic Center Transient Swift J174540.7–290015

    Energy Technology Data Exchange (ETDEWEB)

    Corrales, L. R. [Einstein Fellow, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI, 53706 (United States); Mon, B.; Haggard, D. [McGill Space Institute, McGill University, 3550 University Street, Montreal, QC, H3A 2A7 (Canada); Baganoff, F. K. [MIT Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue, Cambridge, MA, 02139 (United States); Garmire, G. [Huntingdon Institute for X-ray Astronomy, 10677 Franks Road Huntingdon, PA, 16652 (United States); Degenaar, N. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 OHA (United Kingdom); Reynolds, M. [University of Michigan, 1085 S. University, 311 West Hall, Ann Arbor, MI 48109 (United States)

    2017-04-20

    We report the detection of a dust-scattering halo around a recently discovered X-ray transient, Swift J174540.7–290015, which in early 2016 February underwent one of the brightest outbursts ( F {sub X} ≈ 5 × 10{sup −10} erg cm{sup −2} s{sup −1}) observed from a compact object in the Galactic Center field. We analyze four Chandra images that were taken as follow-up observations to Swift discoveries of new Galactic Center transients. After adjusting our spectral extraction for the effects of detector pile-up, we construct a point-spread function for each observation and compare it to the GC field before the outburst. We find residual surface brightness around Swift J174540.7–290015, which has a shape and temporal evolution consistent with the behavior expected from X-rays scattered by foreground dust. We examine the spectral properties of the source, which shows evidence that the object transitioned from a soft to hard spectral state as it faded below L {sub X} ∼ 10{sup 36} erg s{sup −1}. This behavior is consistent with the hypothesis that the object is a low-mass X-ray binary in the Galactic Center.

  5. Transient thermal-mechanical behavior of cracked glass-cloth-reinforced epoxy laminates at low temperatures

    International Nuclear Information System (INIS)

    Shindo, Y.; Ueda, S.

    1997-01-01

    We consider the transient thermal-mechanical response of cracked G-10CR glass-cloth-reinforced epoxy laminates with temperature-dependent properties. The glass-cloth-reinforced epoxy laminates are suddenly cooled on the surfaces. A generalized plane strain finite element model is used to study the influence of warp angle and crack formation on the thermal shock behavior of two-layer woven laminates at low temperatures. Numerical calculations are carried out, and the transient temperature distribution and the thermal-mechanical stresses are shown graphically

  6. V899 MON: AN OUTBURSTING PROTOSTAR WITH A PECULIAR LIGHT CURVE, AND ITS TRANSITION PHASES

    Energy Technology Data Exchange (ETDEWEB)

    Ninan, J. P.; Ojha, D. K.; Baug, T. [Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005 (India); Bhatt, B. C.; Anupama, G. C. [Indian Institute of Astrophysics, Korama ngala, Bangalore 560 034 (India); Mohan, V. [Inter-University Centre for Astronomy and Astrophysics, Pune 411 007 (India); Ghosh, S. K. [National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune 411 007 (India); Men’shchikov, A. [Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot, IRFU/SAp, CEA Saclay, Orme des Merisiers, F-91191 Gif-sur-Yvette (France); Tamura, M. [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Henning, Th., E-mail: ninan@tifr.res.in [Max-Planck-Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany)

    2015-12-10

    We present a detailed study of V899 Mon (a new member in the FUors/EXors family of young low-mass stars undergoing outburst), based on our long-term monitoring of the source starting from 2009 November to 2015 April. Our optical and near-infrared photometric and spectroscopic monitoring recorded the source transitioning from its first outburst to a short-duration quiescence phase (<1 yr), and then returning to a second outburst. We report here the evolution of the outflows from the inner region of the disk as the accretion rate evolved in various epochs. Our high-resolution (R ∼ 37,000) optical spectrum could resolve interesting clumpy structures in the outflow traced by various lines. Change in far-infrared flux was also detected between two outburst epochs. Based on our observations, we constrained various stellar and envelope parameters of V899 Mon, as well as the kinematics of its accretion and outflow. The photometric and spectroscopic properties of this source fall between classical FUors and EXors. Our investigation of V899 Mon hints at instability associated with magnetospheric accretion being the physical cause of the sudden short-duration pause of the outburst in 2011. It is also a good candidate to explain similar short-duration pauses in outbursts of some other FUors/EXors sources.

  7. Deterioration of mechanical properties of high strength structural steel S460N under transient state fire condition

    International Nuclear Information System (INIS)

    Qiang, Xuhong; Bijlaard, Frans S.K.; Kolstein, Henk

    2012-01-01

    Highlights: ► Mechanical properties of S460N under transient state fire condition are obtained. ► Elevated-temperature mechanical properties of steels are dependent on steel grades. ► No design standard is applicable to HSS S460N under transient state fire condition. ► Specific statements on various HSS in fire should be proposed in design standards. ► Research results offer accurate material property for structural design engineers. -- Abstract: 911 World Trade Centre Tragedy put fire safety of constructional steel structures into question. Since then, more and more research attention has been paid to the elevated-temperature mechanical properties of structural steels, which is a critical basis of evaluating the fire performance of steel structures. In the literature the available mechanical properties of structural steels under fire conditions were mainly obtained from steady state test method, as steady state test method is easier to perform than transient state test method and offers stress–strain curves directly. However, the transient state fire condition is considered to be more realistic to represent the real condition when constructions are exposed to fire. In order to reveal the deterioration of mechanical properties of the commonly used high strength structural steel S460N under transient state fire condition, tensile tests were conducted under various constant stress levels up to 800 MPa. The reduction factors of elastic modulus, yield and ultimate strengths of S460N under transient state fire condition were obtained and compared with current leading design standards and available literature. The application of such accurate elevated-temperature mechanical properties reduction factors of S460N can ensure a safe fire-resistance design and evaluation of steel structures with high strength steel S460N under transient state fire condition. This experimental study also supports other relative research on fire performance of steel structures with

  8. Hot spot in eclipsing dwarf nova IY Ursae Majoris during quiescence and normal outburst

    OpenAIRE

    Bakowska, K.; Olech, A.

    2016-01-01

    We present the analysis of hot spot brightness in light curves of the eclipsing dwarf nova IY Ursae Majoris during its normal outburst in March 2013 and in quiescence in April 2012 and in October 2015. Examination of four reconstructed light curves of the hot spot eclipses showed directly that the brightness of the hot spot changed significantly only during the outburst. The brightness of the hot spot, before and after the outburst, was on the same level. Hereby, based on the behaviour of the...

  9. FERMI GBM OBSERVATIONS OF V404 CYG DURING ITS 2015 OUTBURST

    Energy Technology Data Exchange (ETDEWEB)

    Jenke, P. A.; Veres, P.; Briggs, M. S.; Burns, E. [University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Wilson-Hodge, C. A.; Hui, M. [Marshall Space Flight Center, Huntsville, AL 35812 (United States); Homan, Jeroen [MIT Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue 37-582D, Cambridge, MA 02139 (United States); Connaughton, V.; Finger, M. H., E-mail: peter.a.jenke@nasa.gov [Universities Space Research Association, Huntsville, AL 35805 (United States)

    2016-07-20

    V404 Cygni was discovered in 1989 by the Ginga X-ray satellite during its only previously observed X-ray outburst and soon after confirmed as a black hole binary. On 2015 June 15, the Gamma-ray Burst Monitor (GBM) triggered on a new outburst of V404 Cygni. We present 13 days of GBM observations of this outburst, including Earth occultation flux measurements and spectral and temporal analysis. The Earth occultation fluxes reached 30 Crab with detected emission to 100 keV and determined, via hardness ratios, that the source was in a hard state. At high luminosity, spectral analysis between 8 and 300 keV showed that the electron temperature decreased with increasing luminosity. This is expected if the protons and electrons are in thermal equilibrium during an outburst with the electrons cooled by the Compton scattering of softer seed photons from the disk. However, the implied seed photon temperatures are unusually high, suggesting a contribution from another source, such as the jet. No evidence of state transitions is seen during this time period. The temporal analysis reveals power spectra that can be modeled with two or three strong, broad Lorentzians, similar to the power spectra of black hole binaries in their hard state.

  10. Kilohertz QPOs, spectral state transitions and the distance to the neutron star X-ray transient IGR J17473-2721

    DEFF Research Database (Denmark)

    Altamirano, D.; Galloway, D.; Chenevez, Jérôme

    2008-01-01

    We report on RXTE monitoring observations of the transient X-ray binary IGR J17473-2721 since the beginning of its latest outburst on March 26th, 2008 (see ATEL #1445, #1459, #1460, #1461 and #1468). IGR J17473-2721 reached a maximum unabsorbed flux of ~1.30E-8 ergs cm-2 s-1 (2-10 keV, assuming n...

  11. The galactic center GeV excess from a series of leptonic cosmic-ray outbursts

    Energy Technology Data Exchange (ETDEWEB)

    Cholis, Ilias [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Evoli, Carmelo [Univ. Hamburg, Hamburg (Germany); Calore, Francesca [Univ. of Amsterdam, Amsterdam (Netherlands); Linden, Tim [Univ. of Chicago, Chicago, IL (United States); Weniger, Christoph [Univ. of Amsterdam, Amsterdam (Netherlands); Hooper, Dan [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Univ. of Chicago, Chicago, IL (United States)

    2015-06-16

    It has been proposed that a recent outburst of cosmic-ray electrons could account for the excess of GeV-scale gamma rays observed from the region surrounding the Galactic Center. After studying this possibility in some detail, we identify scenarios in which a series of leptonic cosmic-ray outbursts could plausibly generate the observed excess. The morphology of the emission observed outside of ~1° – 2° from the Galactic Center can be accommodated with two outbursts, one which took place approximately ~106 years ago, and another (injecting only about 10% as much energy as the first) about ~105 years ago. The emission observed from the innermost ~1° – 2° requires one or more additional recent outbursts and/or a contribution from a centrally concentrated population of unresolved millisecond pulsars. Furthermore, in order to produce a spectrum that is compatible with the measured excess (whose shape is approximately uniform over the region of the excess), the electrons from the older outburst must be injected with significantly greater average energy than those injected more recently, enabling their spectra to be similar after ~106 years of energy losses.

  12. Formation of Outburst Structure in Hot Dip Galvannealed Coatings on IF Steels

    Directory of Open Access Journals (Sweden)

    Kollárová, M.

    2007-01-01

    Full Text Available Outburst structure in two industrially produced hot dip galvanized interstitial free steel sheets for automotive industry after additional annealing has been examined. Ti IF steel was found to form weak outburst structure in the early stage of annealing, followed by frontal growth of Fe-Zn phases during further heating. The high reactivity of this steel was confirmed by rapid G-phase formation. Under the same conditions, Ti-Nb-P IF steel exhibited frontal growth of Fe-Zn compounds without G-phase formation due to relatively high phosphorous content, which is known as inhibitor of Fe-Zn reaction, but simultaneously significant occurrence of undesired outburst structures was recorded. It was assumed that the phosphorous content was insufficient and/or ferrite grain was very fine.

  13. Sound wave generation by a spherically symmetric outburst and AGN feedback in galaxy clusters

    Science.gov (United States)

    Tang, Xiaping; Churazov, Eugene

    2017-07-01

    We consider the evolution of an outburst in a uniform medium under spherical symmetry, having in mind active galactic nucleus feedback in the intracluster medium. For a given density and pressure of the medium, the spatial structure and energy partition at a given time tage (since the onset of the outburst) are fully determined by the total injected energy Einj and the duration tb of the outburst. We are particularly interested in the late phase evolution when the strong shock transforms into a sound wave. We studied the energy partition during such transition with different combinations of Einj and tb. For an instantaneous outburst with tb → 0, which corresponds to the extension of classic Sedov-Taylor solution with counter-pressure, the fraction of energy that can be carried away by sound waves is ≲12 per cent of Einj. As tb increases, the solution approaches the 'slow piston' limit, with the fraction of energy in sound waves approaching zero. We then repeat the simulations using radial density and temperature profiles measured in Perseus and M87/Virgo clusters. We find that the results with a uniform medium broadly reproduce an outburst in more realistic conditions once proper scaling is applied. We also develop techniques to map intrinsic properties of an outburst (Einj, tb and tage) to the observables like the Mach number of the shock and radii of the shock and ejecta. For the Perseus cluster and M87, the estimated (Einj, tb and tage) agree with numerical simulations tailored for these objects with 20-30 per cent accuracy.

  14. Nucleosynthesis in nova outbursts

    International Nuclear Information System (INIS)

    Iliadis, C.; Azuma, R.E.; Buchmann, L.

    1994-02-01

    Astronomical observations have shown that He, CNO material and/or heavy elements are considerably enriched in certain nova ejecta relative to solar matter. The heavy element enrichments can be explained by the dredge-up of matter from an underlying ONeMg white dwarf and subsequent redistribution of the material by the rp-process. The proton capture reactions on 32 S and 36 A r important for hydrogen burning during nova outbursts have been measured experimentally. The derived stellar reaction rates have been incorporated into large-scale network calculations and the astrophysical consequences are discussed. (author)

  15. Regulation of black-hole accretion by a disk wind during a violent outburst of V404 Cygni.

    Science.gov (United States)

    Muñoz-Darias, T; Casares, J; Mata Sánchez, D; Fender, R P; Armas Padilla, M; Linares, M; Ponti, G; Charles, P A; Mooley, K P; Rodriguez, J

    2016-06-02

    Accretion of matter onto black holes is universally associated with strong radiative feedback and powerful outflows. In particular, black-hole transients have outflows whose properties are strongly coupled to those of the accretion flow. This includes X-ray winds of ionized material, expelled from the accretion disk encircling the black hole, and collimated radio jets. Very recently, a distinct optical variability pattern has been reported in the transient stellar-mass black hole V404 Cygni, and interpreted as disrupted mass flow into the inner regions of its large accretion disk. Here we report observations of a sustained outer accretion disk wind in V404 Cyg, which is unlike any seen hitherto. We find that the outflowing wind is neutral, has a large covering factor, expands at one per cent of the speed of light and triggers a nebular phase once accretion drops sharply and the ejecta become optically thin. The large expelled mass (>10(-8) solar masses) indicates that the outburst was prematurely ended when a sizeable fraction of the outer disk was depleted by the wind, detaching the inner regions from the rest of the disk. The luminous, but brief, accretion phases shown by transients with large accretion disks imply that this outflow is probably a fundamental ingredient in regulating mass accretion onto black holes.

  16. LONG-TERM EVOLUTION OF PROTOSTELLAR AND PROTOPLANETARY DISKS. I. OUTBURSTS

    International Nuclear Information System (INIS)

    Zhu Zhaohuan; Hartmann, Lee; Gammie, Charles F.; Book, Laura G.; Simon, Jacob B.; Engelhard, Eric

    2010-01-01

    As an initial investigation into the long-term evolution of protostellar disks, we explore the conditions required to explain the large outbursts of disk accretion seen in some young stellar objects. We use one-dimensional time-dependent disk models with a phenomenological treatment of the magnetorotational instability (MRI) and gravitational torques to follow disk evolution over long timescales. Comparison with our previous two-dimensional disk model calculations indicates that the neglect of radial effects and two-dimensional disk structure in the one-dimensional case makes only modest differences in the results; this allows us to use the simpler models to explore parameter space efficiently. We find that the mass infall rates typically estimated for low-mass protostars generally result in AU-scale disk accretion outbursts, as predicted by our previous analysis. We also confirm quasi-steady accretion behavior for high mass infall rates if the values of α-parameter for the MRI are small, while at this high accretion rate convection from the thermal instability may lead to some variations. We further constrain the combinations of the α-parameter and the MRI critical temperature, which can reproduce observed outburst behavior. Our results suggest that dust sublimation may be connected with full activation of the MRI. This is consistent with the idea that small dust captures ions and electrons to suppress the MRI. In a companion paper, we will explore both long-term outburst and disk evolution with this model, allowing for infall from protostellar envelopes with differing angular momenta.

  17. Mechanism for transient migration of xenon in UO2

    International Nuclear Information System (INIS)

    Liu, X.-Y.; Uberuaga, B. P.; Andersson, D. A.; Stanek, C. R.; Sickafus, K. E.

    2011-01-01

    In this letter, we report recent work on atomistic modeling of diffusion migration events of the fission gas product xenon in UO 2 nuclear fuel. Under nonequilibrium conditions, Xe atoms can occupy the octahedral interstitial site, in contrast to the thermodynamically most stable uranium substitutional site. A transient migration mechanism involving Xe and two oxygen atoms is identified using basin constrained molecular dynamics employing a Buckingham type interatomic potential. This mechanism is then validated using density functional theory calculations using the nudged elastic band method. An overall reduction in the migration barrier of 1.6-2.7 eV is obtained compared to vacancy-mediated diffusion on the uranium sublattice.

  18. Ultraviolet and optical observations of the dwarf novae VW and WX Hydri during outburst

    International Nuclear Information System (INIS)

    Hassall, B.J.M.; Pringle, J.E.; Schwarzenberge-Czerny, A.; Wade, R.A.; Whelan, J.A.J.; Hill, P.W.

    1983-01-01

    Simultaneous spectrophotometry in the range 1200-7000 A, of the dwarf novae at quiescence and maximum is presented. The continuum spectra are compared with the standard model disc spectrum and, with one exception, the fit is poor. The assumptions that the disc is both steady-state and blackbody are reconsidered and it is pointed out that a νsup(1/3) spectrum is not to be expected from a disc sufficiently small to be accommodated within these short binary period systems. On the rise to outburst the UV flux in VW Hydri is observed to lag at least one day behind the optical, supporting the mass accretion event explanation of dwarf nova outbursts. The behaviour of the UV and optical line features during outbursts is described, in particular, the P Cygni features observed in a super-outburst of WX Hydri, from which a mass loss rate is estimated, small compared with the mass transfer rate from the secondary star. (author)

  19. Investigations of outbursts and tremors in Polish collieries with application of radon measurements

    International Nuclear Information System (INIS)

    Wysocka, M.

    2010-01-01

    In the 80's and 90's of the last century some attempts were undertaken to apply specific radiometric methods to support the prediction of outbursts in collieries, located in Lower Silesian Coal Basin (LSCB) in south-western Poland. This idea was developed as an analogy to the application of radon changes in groundwater prior to earthquakes, and on this basis the hypothesis of variations of radon emanation from coal seams, preceding approaching outburst, was formulated. It has been stated, that a certain correlation between temporal and spatial variations of radon level and the level of outburst's hazard existed. Then, new investigations have been started in copper and coal mines with the hope to use radon as a tool for the prediction of another dynamic phenomena - tremors. In the case of these investigations, only weak evidences were found. In the last years the occurrence of outburst was noticed in the collieries of Upper Silesian Coal Basin (USCB). Therefore, we started observations of changes of radon concentration in gas, sampled from headings, driven in endangered coal seams. The goal of the research is an attempt to formulate '' radon index of outburst hazard '' to support other, routinely used, methods of the prediction of dangerous events. In this paper some results of investigations, done in collieries in LSCB and in copper mines are quoted to give the background for preliminary results of new research, ongoing in one of the coal mines in the Upper Silesia region. (authors)

  20. Look at Epilepsy: Electrical Outbursts in the Brain

    Science.gov (United States)

    ... November 2015 Print this issue A Look at Epilepsy Electrical Outbursts in the Brain En español Send us your comments When you hear the word epilepsy, you might think of intense seizures with muscle ...

  1. Transient hypofrontality as a mechanism for the psychological effects of exercise.

    Science.gov (United States)

    Dietrich, Arne

    2006-11-29

    Although exercise is known to promote mental health, a satisfactory understanding of the mechanism underlying this phenomenon has not yet been achieved. A new mechanism is proposed that is based on established concepts in cognitive psychology and the neurosciences as well as recent empirical work on the functional neuroanatomy of higher mental processes. Building on the fundamental principle that processing in the brain is competitive and the fact that the brain has finite metabolic resources, the transient hypofrontality hypothesis suggests that during exercise the extensive neural activation required to run motor patterns, assimilate sensory inputs, and coordinate autonomic regulation results in a concomitant transient decrease of neural activity in brain structures, such as the prefrontal cortex, that are not pertinent to performing the exercise. An exercise-induced state of frontal hypofunction can provide a coherent account of the influences of exercise on emotion and cognition. The new hypothesis is proposed primarily on the strength of its heuristic value, as it suggests several new avenues of research.

  2. Canyon formation constraints on the discharge of catastrophic outburst floods of Earth and Mars

    Science.gov (United States)

    Lapotre, Mathieu G. A.; Lamb, Michael P.; Williams, Rebecca M. E.

    2016-07-01

    Catastrophic outburst floods carved amphitheater-headed canyons on Earth and Mars, and the steep headwalls of these canyons suggest that some formed by upstream headwall propagation through waterfall erosion processes. Because topography evolves in concert with water flow during canyon erosion, we suggest that bedrock canyon morphology preserves hydraulic information about canyon-forming floods. In particular, we propose that for a canyon to form with a roughly uniform width by upstream headwall retreat, erosion must occur around the canyon head, but not along the sidewalls, such that canyon width is related to flood discharge. We develop a new theory for bedrock canyon formation by megafloods based on flow convergence of large outburst floods toward a horseshoe-shaped waterfall. The model is developed for waterfall erosion by rock toppling, a candidate erosion mechanism in well fractured rock, like columnar basalt. We apply the model to 14 terrestrial (Channeled Scablands, Washington; Snake River Plain, Idaho; and Ásbyrgi canyon, Iceland) and nine Martian (near Ares Vallis and Echus Chasma) bedrock canyons and show that predicted flood discharges are nearly 3 orders of magnitude less than previously estimated, and predicted flood durations are longer than previously estimated, from less than a day to a few months. Results also show a positive correlation between flood discharge per unit width and canyon width, which supports our hypothesis that canyon width is set in part by flood discharge. Despite lower discharges than previously estimated, the flood volumes remain large enough for individual outburst floods to have perturbed the global hydrology of Mars.

  3. Classification of coal seam outburst hazards and evaluation of the importance of influencing factors

    OpenAIRE

    Shi Xianzhi; Song Dazhao; Qian Ziwei

    2017-01-01

    Coal and gas outbursts are the result of several geological factors related to coal seam gas (coal seam gas pressure P, coal seam sturdiness coefficient f and coal seam gas content W), and these parameters can be used to classify the outburst hazard level of a coal seam.

  4. Monitoring Chandra Observations of the Quasi-persistent Neutron Star X-Ray Transient MXB 1659-29 in Quiescence: The Cooling Curve of the Heated Neutron Star Crust

    NARCIS (Netherlands)

    Wijnands, R.A.D.; Homan, J.; Miller, J.M.; Lewin, W.H.G.

    2004-01-01

    We have observed the quasi-persistent neutron star X-ray transient and eclipsing binary MXB 1659-29 in quiescence on three occasions with Chandra. The purpose of our observations was to monitor the quiescent behavior of the source after its last prolonged (~2.5 yr) outburst that ended in 2001

  5. The quiescent state of the neutron-star X-ray transient GRS 1747-312 in the globular cluster Terzan 6

    Science.gov (United States)

    Vats, Smriti; Wijnands, Rudy; Parikh, Aastha S.; Ootes, Laura; Degenaar, Nathalie; Page, Dany

    2018-04-01

    We studied the transient neutron-star low-mass X-ray binary GRS 1747-312, located in the globular cluster Terzan 6, in its quiescent state after its outburst in August 2004, using an archival XMM-Newton observation. A source was detected in this cluster and its X-ray spectrum can be fitted with the combination of a soft, neutron-star atmosphere model and a hard, power-law model. Both contributed roughly equally to the observed 0.5-10 keV luminosity (˜4.8 × 1033 erg s-1). This type of X-ray spectrum is typically observed for quiescent neutron-star X-ray transients that are perhaps accreting in quiescence at very low rates. Therefore, if this X-ray source is the quiescent counterpart of GRS 1747-312, then this source is also accreting at low levels in-between outbursts. Since source confusion a likely problem in globular clusters, it is quite possible that part, if not all, of the emission we observed is not related to GRS 1747-312, and is instead associated with another source or conglomeration of sources in the cluster. Currently, it is not possible to determine exactly which part of the emission truly originates from GRS1747-312, and a Chandra observation (when no source is in outburst in Terzan 6) is needed to be conclusive. Assuming that the detected emission is due to GRS 1747-312, we discuss the observed results in the context of what is known about other quiescent systems. We also investigated the thermal evolution of the neutron-star in GRS 1747-312, and inferred that GRS 1747-312 can be considered a typical quiescent system under our assumptions.

  6. Nucleosynthesis in nova outbursts

    Energy Technology Data Exchange (ETDEWEB)

    Iliadis, C [TRIUMF, Vancouver, BC (Canada); [Univ. of Toronto, McLennan Physical Labs., Toronto, ON (Canada); Azuma, R E [Univ. of Toronto, McLennan Physical Lab., Toronto, ON (Canada); Buchmann, L [TRIUMF, Vancouver, BC (Canada); and others

    1994-02-01

    Astronomical observations have shown that He, CNO material and/or heavy elements are considerably enriched in certain nova ejecta relative to solar matter. The heavy element enrichments can be explained by the dredge-up of matter from an underlying ONeMg white dwarf and subsequent redistribution of the material by the rp-process. The proton capture reactions on 32{sup S} and 36{sup A}r important for hydrogen burning during nova outbursts have been measured experimentally. The derived stellar reaction rates have been incorporated into large-scale network calculations and the astrophysical consequences are discussed. (author) 17 refs., 2 figs.

  7. RENEWED ACTIVITY FROM THE X-RAY TRANSIENT SAXJ 1810.8-2609 WITH INTEGRAL

    DEFF Research Database (Denmark)

    Fiocchi, M.; Natalucci, L.; Chenevez, Jérôme

    2009-01-01

    (36) erg s(-1) in the 20-100 keV energy range. This low outburst luminosity and the long-term time-average accretion rate of similar to 5 x 10(-12) M-circle dot yr(-1) suggest that SAX J1810.8-2609 is a faint soft X-ray transient. During the flux increase, spectra are consistent with a thermal...... Comptonization model with a temperature plasma of kT(e) similar to 23-30 keV and an optical depth of tau similar to 1.2-1.5, independent of the luminosity of the system. This is a typical low hard spectral state for which the X-ray emission is attributed to the upscattering of soft seed photons by a hot......, optically thin electron plasma. During the decay, spectra have a different shape, the high energy tail being compatible with a single power law. This confirm similar behavior observed by BeppoSAX during the previous outburst, with the absence of visible cutoff in the hard X-ray spectrum. INTEGRAL...

  8. Short-term variability of dwarf nova SS Cyg during outbursts

    International Nuclear Information System (INIS)

    Voloshina, I; Metlov, V; Rovithis-Livaniou, H

    2009-01-01

    Here we report the results of CCD observations of classical dwarf nova SS Cyg carried out with the two 60-cm telescopes in Crimea during the last years. These observations cover a few outbursts in 2006, 2007 and 2008. Power spectrum analysis of our CCD data clearly shows the existence of rapid periodic oscillations in the light curve of SS Cyg at the stage of decline after maximum. CCD observations of SS Cyg in autumn 2006 outburst revealed oscillations with the two periods 10 s and 76 s, in November 2007 - with 41 s period and in January 2008 with 98 s. We interpret detected variations as quasi-periodic oscillations.

  9. Short-term variability of dwarf nova SS Cyg during outbursts

    Energy Technology Data Exchange (ETDEWEB)

    Voloshina, I; Metlov, V; Rovithis-Livaniou, H, E-mail: vib@sai.msu.r [Section of Astrophysics, Astronomy and Mechanics, Department of Physics, Athens University, Zagrafos 15784, Athens (Greece)

    2009-06-01

    Here we report the results of CCD observations of classical dwarf nova SS Cyg carried out with the two 60-cm telescopes in Crimea during the last years. These observations cover a few outbursts in 2006, 2007 and 2008. Power spectrum analysis of our CCD data clearly shows the existence of rapid periodic oscillations in the light curve of SS Cyg at the stage of decline after maximum. CCD observations of SS Cyg in autumn 2006 outburst revealed oscillations with the two periods 10 s and 76 s, in November 2007 - with 41 s period and in January 2008 with 98 s. We interpret detected variations as quasi-periodic oscillations.

  10. EVIDENCE FOR AN FU ORIONIS-LIKE OUTBURST FROM A CLASSICAL T TAURI STAR

    International Nuclear Information System (INIS)

    Miller, Adam A.; Poznanski, Dovi; Silverman, Jeffrey M.; Kleiser, Io K. W.; Cenko, S. Bradley; Bloom, Joshua S.; Filippenko, Alexei V.; Hillenbrand, Lynne A.; Kasliwal, Mansi M.; Ofek, Eran O.; Quimby, Robert M.; Covey, Kevin R.; Rojas-Ayala, Barbara; Muirhead, Philip S.; Law, Nicholas M.; Dekany, Richard G.; Rahmer, Gustavo; Hale, David; Smith, Roger; Nugent, Peter

    2011-01-01

    We present pre- and post-outburst observations of the new FU Orionis-like young stellar object PTF 10qpf (also known as LkHα 188-G4 and HBC 722). Prior to this outburst, LkHα 188-G4 was classified as a classical T Tauri star (CTTS) on the basis of its optical emission-line spectrum superposed on a K8-type photosphere and its photometric variability. The mid-infrared spectral index of LkHα 188-G4 indicates a Class II-type object. LkHα 188-G4 exhibited a steady rise by ∼1 mag over ∼11 months starting in August 2009, before a subsequent more abrupt rise of >3 mag on a timescale of ∼2 months. Observations taken during the eruption exhibit the defining characteristics of FU Orionis variables: (1) an increase in brightness by ∼>4 mag, (2) a bright optical/near-infrared reflection nebula appeared, (3) optical spectra are consistent with a G supergiant and dominated by absorption lines, the only exception being Hα which is characterized by a P Cygni profile, (4) near-infrared spectra resemble those of late K-M giants/supergiants with enhanced absorption seen in the molecular bands of CO and H 2 O, and (5) outflow signatures in H and He are seen in the form of blueshifted absorption profiles. LkHα 188-G4 is the first member of the FU Orionis-like class with a well-sampled optical to mid-infrared spectral energy distribution in the pre-outburst phase. The association of the PTF 10qpf outburst with the previously identified CTTS LkHα 188-G4 (HBC 722) provides strong evidence that FU Orionis-like eruptions represent periods of enhanced disk accretion and outflow, likely triggered by instabilities in the disk. The early identification of PTF 10qpf as an FU Orionis-like variable will enable detailed photometric and spectroscopic observations during its post-outburst evolution for comparison with other known outbursting objects.

  11. SAX J2103.5+4545 in outburst

    DEFF Research Database (Denmark)

    Galis, R.; Beckmann, V.; Bianchin, V.

    2008-01-01

    We report an intense hard X-ray outburst detected from the Be/ neutron star HMXB SAX J2103.5+4545 (Blay et al. 2004, A&A, 427, 293), which is known to be a pulsar. The source was detected during INTEGRAL observations of the Galactic Plane in the Cygnus region, starting at 2007-04-25T09:14 (UTC...

  12. a Synoptic Study of AN X-Ray Nova in Outburst

    Science.gov (United States)

    McClintock, Jeffrey

    Optical studies of X-ray novae in quiescence have yielded compelling evidence for black holes in binary systems. However, X-ray studies in quiescence are severely constrained by the near absence of high energy emission. Thus, further observational advances in black hole astrophysics require a substantial commitment to observe X-ray novae in outburst in just that spectral range accessible to XTE. We propose an agressive campaign of X-ray observations of the next non-pulsing X-ray nova that rises above 3 Crab at 2-10 keV. We further propose a coordinated and intensive campaign of optical and radio observations covering both hemispheres. The observations will provide a full temporal and spectral view of the outburst cycle.

  13. An isotopic study of the role of carbon dioxide in outbursts in coal mines

    International Nuclear Information System (INIS)

    Smith, J.W.; Gould, K.W.

    1980-01-01

    The occurrence of instantaneous outbursting in the Bulli coal seam at the West Cliff Colliery, Appin, NSW can be correlated directly with an increase in concentration (0.5 to 75%) and a related decrease in the 13 C content (delta 13 C + 16 to -0.8% PDB) of the CO 2 in the seam gas. Two sources of CO 2 are required. The greater incidence of outbursting in CO 2 -rich zones is explained by the conversion to bicarbonate of cleat and fracture filling calcite deep within the coal and the transport of this bicarbonate in water to mine openings. The weakening of the resistance of the coal to shear by this removal of carbonate is an additional factor to be considered in assessing outbursting situations. (author)

  14. The Mechanical Transient Process at Asynchronous Motor Oscillating Mode

    Science.gov (United States)

    Antonovičs, Uldis; Bražis, Viesturs; Greivulis, Jānis

    2009-01-01

    The research object is squirrel-cage asynchronous motor connected to single-phase sinusoidal. There are shown, that by connecting to the stator windings a certain sequence of half-period positive and negative voltage, a motor rotor is rotated, but three times slower than in the three-phase mode. Changing the connecting sequence of positive and negative half-period voltage to stator windings, motor can work in various oscillating modes. It is tested experimentally. The mechanical transient processes had been researched in rotation and oscillating modes.

  15. A New Stellar Outburst Associated with the Magnetic Activities of the K-type Dwarf in a White Dwarf Binary

    Energy Technology Data Exchange (ETDEWEB)

    Qian, S.-B.; Han, Z.-T.; Zhang, B.; Zhu, L.-Y.; Zhao, E.-G.; Liao, W.-P.; Tian, X.-M.; Wang, Z.-H. [Yunnan Observatories, Chinese Academy of Sciences (CAS), P.O. Box 110, 650011 Kunming (China); Zejda, M. [Department of Theoretical Physics and Astrophysics, Masaryk University, Kotlářská 2, CZ-611 37 Brno (Czech Republic); Michel, R., E-mail: qsb@ynao.ac.cn [Instituto de Astronomía, Universidad Nacional Autónoma de México, Ensenada, Baja California, México (Mexico)

    2017-10-20

    1SWASP J162117.36+441254.2 was originally classified as an EW-type binary with a period of 0.20785 days. However, it was detected to have undergone a stellar outburst on 2016 June 3. Although the system was later classified as a cataclysmic variable (CV) and the event was attributed as a dwarf nova outburst, the physical reason is still unknown. This binary has been monitored photometrically since 2016 April 19, and many light curves were obtained before, during, and after the outburst. Those light and color curves observed before the outburst indicate that the system is a special CV. The white dwarf is not accreting material from the secondary and there are no accretion disks surrounding the white dwarf. By comparing the light curves obtained from 2016 April 19 to those from September 14, it was found that magnetic activity of the secondary is associated with the outburst. We show strong evidence that the L {sub 1} region on the secondary was heavily spotted before and after the outburst and thus quench the mass transfer, while the outburst is produced by a sudden mass accretion of the white dwarf. These results suggest that J162117 is a good astrophysical laboratory to study stellar magnetic activity and its influences on CV mass transfer and mass accretion.

  16. A New Stellar Outburst Associated with the Magnetic Activities of the K-type Dwarf in a White Dwarf Binary

    Science.gov (United States)

    Qian, S.-B.; Han, Z.-T.; Zhang, B.; Zejda, M.; Michel, R.; Zhu, L.-Y.; Zhao, E.-G.; Liao, W.-P.; Tian, X.-M.; Wang, Z.-H.

    2017-10-01

    1SWASP J162117.36+441254.2 was originally classified as an EW-type binary with a period of 0.20785 days. However, it was detected to have undergone a stellar outburst on 2016 June 3. Although the system was later classified as a cataclysmic variable (CV) and the event was attributed as a dwarf nova outburst, the physical reason is still unknown. This binary has been monitored photometrically since 2016 April 19, and many light curves were obtained before, during, and after the outburst. Those light and color curves observed before the outburst indicate that the system is a special CV. The white dwarf is not accreting material from the secondary and there are no accretion disks surrounding the white dwarf. By comparing the light curves obtained from 2016 April 19 to those from September 14, it was found that magnetic activity of the secondary is associated with the outburst. We show strong evidence that the L 1 region on the secondary was heavily spotted before and after the outburst and thus quench the mass transfer, while the outburst is produced by a sudden mass accretion of the white dwarf. These results suggest that J162117 is a good astrophysical laboratory to study stellar magnetic activity and its influences on CV mass transfer and mass accretion.

  17. A New Stellar Outburst Associated with the Magnetic Activities of the K-type Dwarf in a White Dwarf Binary

    International Nuclear Information System (INIS)

    Qian, S.-B.; Han, Z.-T.; Zhang, B.; Zhu, L.-Y.; Zhao, E.-G.; Liao, W.-P.; Tian, X.-M.; Wang, Z.-H.; Zejda, M.; Michel, R.

    2017-01-01

    1SWASP J162117.36+441254.2 was originally classified as an EW-type binary with a period of 0.20785 days. However, it was detected to have undergone a stellar outburst on 2016 June 3. Although the system was later classified as a cataclysmic variable (CV) and the event was attributed as a dwarf nova outburst, the physical reason is still unknown. This binary has been monitored photometrically since 2016 April 19, and many light curves were obtained before, during, and after the outburst. Those light and color curves observed before the outburst indicate that the system is a special CV. The white dwarf is not accreting material from the secondary and there are no accretion disks surrounding the white dwarf. By comparing the light curves obtained from 2016 April 19 to those from September 14, it was found that magnetic activity of the secondary is associated with the outburst. We show strong evidence that the L 1 region on the secondary was heavily spotted before and after the outburst and thus quench the mass transfer, while the outburst is produced by a sudden mass accretion of the white dwarf. These results suggest that J162117 is a good astrophysical laboratory to study stellar magnetic activity and its influences on CV mass transfer and mass accretion.

  18. Shock Dynamics in Stellar Outbursts. I. Shock Formation

    Energy Technology Data Exchange (ETDEWEB)

    Ro, Stephen; Matzner, Christopher D., E-mail: ro@astro.utoronto.ca [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada)

    2017-05-20

    Wave-driven outflows and non-disruptive explosions have been implicated in pre-supernova outbursts, supernova impostors, luminous blue variable eruptions, and some narrow-line and superluminous supernovae. To model these events, we investigate the dynamics of stars set in motion by strong acoustic pulses and wave trains, focusing on nonlinear wave propagation, shock formation, and an early phase of the development of a weak shock. We identify the shock formation radius, showing that a heuristic estimate based on crossing characteristics matches an exact expansion around the wave front and verifying both with numerical experiments. Our general analytical condition for shock formation applies to one-dimensional motions within any static environment, including both eruptions and implosions. We also consider the early phase of shock energy dissipation. We find that waves of super-Eddington acoustic luminosity always create shocks, rather than damping by radiative diffusion. Therefore, shock formation is integral to super-Eddington outbursts.

  19. The intermediate polar GK Persei: An unstable relation of the X-ray and the optical intensities in a series of outbursts

    Science.gov (United States)

    Šimon, V.

    2015-03-01

    Context. GK Per is an intermediate polar that has been displaying dwarf nova outbursts since the middle of the twentieth century. Aims: I analyzed a series of such outbursts in the optical and X-ray bands. I pay attention to the relation of intensities of the optical and X-ray emissions, and its reproducibility in a series of these consecutive outbursts. Methods: This analysis uses the data from the BAT/Swift, ASM/RXTE, AAVSO, and AFOEV databases. It investigates the relation of the time evolution of the profiles of outbursts in the individual bands (hard X-ray, medium/hard X-ray, and optical). Results: This analysis shows that the X-ray intensity steeply rises only in the start of the optical outburst and steeply declines only when the optical outburst comes to its end. However, the 1.5-50 keV band intensity saturates and balances on a plateau during the outburst. (The longer the outburst, the longer its plateau.) The peak X-ray intensities of this series display a significantly narrower range than the optical ones (a factor of about two versus a factor of about eight). This implies a discrepancy between the mass flow through the disk and the production of the X-ray emission via bremsstrahlung at the polar caps of the white dwarf. This discrepancy is the largest in the time of the peak optical intensity when the whole disk (or at least its inner part) is in the hot state and the flow of matter through the disk is the greatest. This study shows that a series of outbursts constitutes more general properties of this discrepancy. I argue that the saturation of the X-ray luminosity in outburst cannot be caused by a dominant increase in X-ray absorption. In the interpretation, large structural changes of the accreting regions at the magnetic poles of the white dwarf occur during the outburst. A buried shock proposed by some authors for polars is also promising for explaining the X-ray light curves of outbursts of GK Per. This research made use of the BAT/Swift, ASM

  20. The quiescent state of the neutron-star X-ray transient GRS 1747-312 in the globular cluster Terzan 6

    Science.gov (United States)

    Vats, Smriti; Wijnands, Rudy; Parikh, Aastha S.; Ootes, Laura; Degenaar, Nathalie; Page, Dany

    2018-06-01

    We studied the transient neutron-star low-mass X-ray binary GRS 1747-312, located in the globular cluster Terzan 6, in its quiescent state after its outburst in August 2004, using an archival XMM-Newton observation. A source was detected in this cluster and its X-ray spectrum can be fitted with the combination of a soft, neutron-star atmosphere model and a hard, power-law model. Both contributed roughly equally to the observed 0.5-10 keV luminosity (˜4.8 × 1033 erg s-1). This type of X-ray spectrum is typically observed for quiescent neutron-star X-ray transients that are perhaps accreting in quiescence at very low rates. Therefore, if this X-ray source is the quiescent counterpart of GRS 1747-312, then this source is also accreting at low levels in-between outbursts. Since source confusion is a likely problem in globular clusters, it is quite possible that part, if not all, of the emission we observed is not related to GRS 1747-312, and is instead associated with another source or conglomeration of sources in the cluster. Currently, it is not possible to determine exactly which part of the emission truly originates from GRS 1747-312, and a Chandra observation (when no source is in outburst in Terzan 6) is needed to be conclusive. Assuming that the detected emission is due to GRS 1747-312, we discuss the observed results in the context of what is known about other quiescent systems. We also investigated the thermal evolution of the neutron star in GRS 1747-312, and inferred that GRS 1747-312 can be considered a typical quiescent system under our assumptions.

  1. A NEW CLASS OF LUMINOUS TRANSIENTS AND A FIRST CENSUS OF THEIR MASSIVE STELLAR PROGENITORS

    International Nuclear Information System (INIS)

    Thompson, Todd A.; Prieto, Jose L.; Stanek, K. Z.; Beacom, John F.; Kochanek, Christopher S.; Kistler, Matthew D.

    2009-01-01

    The progenitors of SN 2008S and the 2008 luminous transient in NGC 300 were deeply dust-enshrouded massive stars, with extremely red mid-infrared (MIR) colors and relatively low bolometric luminosities (∼5 x 10 4 L sun ). The transients were optically faint compared to normal core-collapse supernovae (ccSNe), with peak absolute visual magnitudes of -13 ∼> M V ∼> -15, and their spectra exhibit narrow Balmer and [Ca II] emission lines. These events are unique among transient-progenitor pairs and hence constitute a new class. Additional members of this class may include the M85 transient, SN 1999bw, 2002bu, and others. Whether they are true supernovae or bright massive-star eruptions, we argue that their rate is of order ∼20% of the ccSN rate in star-forming galaxies. This fact is remarkable in light of the observation that a very small fraction of all massive stars in any one galaxy, at any moment, have the infrared colors of the progenitors of SN 2008S and the NGC 300 transient. We show this by extracting MIR and optical luminosity, color, and variability properties of massive stars in M33 using archival imaging. We find that the fraction of massive stars with colors consistent with the progenitors of SN 2008S and the NGC 300 transient is ∼ -4 . In fact, only ∼ 4 yr before explosion, be it death or merely eruption. We discuss the implications of this finding for the evolution and census of 'low-mass' massive stars (i.e., ∼8-12 M sun ), and we connect it with theoretical discussions of electron-capture supernovae (ecSNe) near this mass range. Other potential mechanisms, including the explosive birth of massive white dwarfs and massive star outbursts, are also discussed. A systematic census with (warm) Spitzer of galaxies in the local universe (D ∼< 10 Mpc) for analogous progenitors would significantly improve our knowledge of this channel to massive stellar explosions, and potentially to others with obscured progenitors.

  2. MULTIWAVELENGTH OBSERVATIONS OF V2775 Ori, AN OUTBURSTING PROTOSTAR IN L 1641: EXPLORING THE EDGE OF THE FU ORIONIS REGIME

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, William J.; Megeath, S. Thomas; Kounkel, Marina [Department of Physics and Astronomy, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606 (United States); Tobin, John J. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Stutz, Amelia M.; Henning, Thomas [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Ali, Babar [NHSC/IPAC/Caltech, 770 South Wilson Avenue, Pasadena, CA 91125 (United States); Remming, Ian; Manoj, P. [Department of Physics and Astronomy, 500 Wilson Boulevard, University of Rochester, Rochester, NY 14627 (United States); Stanke, Thomas [ESO, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei Muenchen (Germany); Osorio, Mayra [Instituto de Astrofisica de Andalucia, CSIC, Camino Bajo de Huetor 50, E-18008, Granada (Spain); Wilson, T. L., E-mail: wfische@utnet.utoledo.edu [Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375 (United States)

    2012-09-01

    Individual outbursting young stars are important laboratories for studying the physics of episodic accretion and the extent to which this phenomenon can explain the luminosity distribution of protostars. We present new and archival data for V2775 Ori (HOPS 223), a protostar in the L 1641 region of the Orion molecular clouds that was discovered by Caratti o Garatti et al. to have recently undergone an order-of-magnitude increase in luminosity. Our near-infrared spectra of the source have strong blueshifted He I {lambda}10830 absorption, strong H{sub 2}O and CO absorption, and no H I emission, all typical of FU Orionis sources. With data from the Infrared Telescope Facility, the Two Micron All Sky Survey, the Hubble Space Telescope, Spitzer, the Wide-field Infrared Survey Explorer, Herschel, and the Atacama Pathfinder Experiment that span from 1 to 70 {mu}m pre-outburst and from 1 to 870 {mu}m post-outburst, we estimate that the outburst began between 2005 April and 2007 March. We also model the pre- and post-outburst spectral energy distributions of the source, finding it to be in the late stages of accreting its envelope with a disk-to-star accretion rate that increased from {approx}2 Multiplication-Sign 10{sup -6} M{sub Sun} yr{sup -1} to {approx}10{sup -5} M{sub Sun} yr{sup -1} during the outburst. The post-outburst luminosity at the epoch of the FU Orionis-like near-IR spectra is 28 L{sub Sun }, making V2775 Ori the least luminous documented FU Orionis outburster with a protostellar envelope. The existence of low-luminosity outbursts supports the notion that a range of episiodic accretion phenomena can partially explain the observed spread in protostellar luminosities.

  3. The Outburst Decay of the Low Magnetic Field Magnetar SGR 0418+5729

    Science.gov (United States)

    Rea, N.; Israel, G. L.; Pons, J. A.; Turolla, R.; Viganò, D.; Zane, S.; Esposito, P.; Perna, R.; Papitto, A.; Terreran, G.; Tiengo, A.; Salvetti, D.; Girart, J. M.; Palau, Aina; Possenti, A.; Burgay, M.; Göğüş, E.; Caliandro, G. A.; Kouveliotou, C.; Götz, D.; Mignani, R. P.; Ratti, E.; Stella, L.

    2013-06-01

    We report on the long-term X-ray monitoring of the outburst decay of the low magnetic field magnetar SGR 0418+5729 using all the available X-ray data obtained with RXTE, Swift, Chandra, and XMM-Newton observations from the discovery of the source in 2009 June up to 2012 August. The timing analysis allowed us to obtain the first measurement of the period derivative of SGR 0418+5729: \\dot{P}=4(1)\\times 10^{-15} s s-1, significant at a ~3.5σ confidence level. This leads to a surface dipolar magnetic field of B dip ~= 6 × 1012 G. This measurement confirms SGR 0418+5729 as the lowest magnetic field magnetar. Following the flux and spectral evolution from the beginning of the outburst up to ~1200 days, we observe a gradual cooling of the tiny hot spot responsible for the X-ray emission, from a temperature of ~0.9 to 0.3 keV. Simultaneously, the X-ray flux decreased by about three orders of magnitude: from about 1.4 × 10-11 to 1.2 × 10-14 erg s-1 cm-2. Deep radio, millimeter, optical, and gamma-ray observations did not detect the source counterpart, implying stringent limits on its multi-band emission, as well as constraints on the presence of a fossil disk. By modeling the magneto-thermal secular evolution of SGR 0418+5729, we infer a realistic age of ~550 kyr, and a dipolar magnetic field at birth of ~1014 G. The outburst characteristics suggest the presence of a thin twisted bundle with a small heated spot at its base. The bundle untwisted in the first few months following the outburst, while the hot spot decreases in temperature and size. We estimate the outburst rate of low magnetic field magnetars to be about one per year per galaxy, and we briefly discuss the consequences of such a result in several other astrophysical contexts.

  4. THE OUTBURST DECAY OF THE LOW MAGNETIC FIELD MAGNETAR SGR 0418+5729

    International Nuclear Information System (INIS)

    Rea, N.; Papitto, A.; Terreran, G.; Girart, J. M.; Palau, Aina; Caliandro, G. A.; Israel, G. L.; Pons, J. A.; Viganò, D.; Turolla, R.; Zane, S.; Esposito, P.; Tiengo, A.; Salvetti, D.; Perna, R.; Possenti, A.; Burgay, M.; Göğüş, E.; Kouveliotou, C.; Götz, D.

    2013-01-01

    We report on the long-term X-ray monitoring of the outburst decay of the low magnetic field magnetar SGR 0418+5729 using all the available X-ray data obtained with RXTE, Swift, Chandra, and XMM-Newton observations from the discovery of the source in 2009 June up to 2012 August. The timing analysis allowed us to obtain the first measurement of the period derivative of SGR 0418+5729: P-dot =4(1)×10 -15 s s –1 , significant at a ∼3.5σ confidence level. This leads to a surface dipolar magnetic field of B dip ≅ 6 × 10 12 G. This measurement confirms SGR 0418+5729 as the lowest magnetic field magnetar. Following the flux and spectral evolution from the beginning of the outburst up to ∼1200 days, we observe a gradual cooling of the tiny hot spot responsible for the X-ray emission, from a temperature of ∼0.9 to 0.3 keV. Simultaneously, the X-ray flux decreased by about three orders of magnitude: from about 1.4 × 10 –11 to 1.2 × 10 –14 erg s –1 cm –2 . Deep radio, millimeter, optical, and gamma-ray observations did not detect the source counterpart, implying stringent limits on its multi-band emission, as well as constraints on the presence of a fossil disk. By modeling the magneto-thermal secular evolution of SGR 0418+5729, we infer a realistic age of ∼550 kyr, and a dipolar magnetic field at birth of ∼10 14 G. The outburst characteristics suggest the presence of a thin twisted bundle with a small heated spot at its base. The bundle untwisted in the first few months following the outburst, while the hot spot decreases in temperature and size. We estimate the outburst rate of low magnetic field magnetars to be about one per year per galaxy, and we briefly discuss the consequences of such a result in several other astrophysical contexts.

  5. The Discovery of an Outburst and Pulsed X-ray Flux from SMC X-2 from RXTE Observations

    CERN Document Server

    Corbet, R H D; Coe, M J; Laycock, S; Handler, G

    2001-01-01

    Rossi X-ray Timing Explorer All Sky Monitor observations of SMC X-2 show that the source experienced an outburst in January to April 2000 reaching a peak luminosity of greater than ~10^38 ergs s^-1. RXTE Proportional Counter Array observations during this outburst reveal the presence of pulsations with a 2.37s period. However, optical photometry of the optical counterpart showed the source to be still significantly fainter than it was more than half a year after the outburst in the 1970s when SMC X-2 was discovered.

  6. Simulating X-ray bursts during a transient accretion event

    Science.gov (United States)

    Johnston, Zac; Heger, Alexander; Galloway, Duncan K.

    2018-06-01

    Modelling of thermonuclear X-ray bursts on accreting neutron stars has to date focused on stable accretion rates. However, bursts are also observed during episodes of transient accretion. During such events, the accretion rate can evolve significantly between bursts, and this regime provides a unique test for burst models. The accretion-powered millisecond pulsar SAX J1808.4-3658 exhibits accretion outbursts every 2-3 yr. During the well-sampled month-long outburst of 2002 October, four helium-rich X-ray bursts were observed. Using this event as a test case, we present the first multizone simulations of X-ray bursts under a time-dependent accretion rate. We investigate the effect of using a time-dependent accretion rate in comparison to constant, averaged rates. Initial results suggest that using a constant, average accretion rate between bursts may underestimate the recurrence time when the accretion rate is decreasing, and overestimate it when the accretion rate is increasing. Our model, with an accreted hydrogen fraction of X = 0.44 and a CNO metallicity of ZCNO = 0.02, reproduces the observed burst arrival times and fluences with root mean square (rms) errors of 2.8 h, and 0.11× 10^{-6} erg cm^{-2}, respectively. Our results support previous modelling that predicted two unobserved bursts and indicate that additional bursts were also missed by observations.

  7. ULTRAVIOLET SPECTROSCOPIC ANALYSIS OF TRANSIENT MASS FLOW OUTBURST IN U CEPHEI

    Energy Technology Data Exchange (ETDEWEB)

    Tupa, Peter R.; DeLeo, Gary G.; McCluskey, George E. [Physics Department, Lehigh University, Bethlehem, PA 18015 (United States); Kondo, Yoji [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Sahade, Jorge [Facultad de Ciencias Astronómicas, Paseo del Bosque s/n, B1900FWA-La Plata (Argentina); Giménez, Alvaro [Centro de Astrobiologia, CSIC/INTA, Carretera de Torrejon a Ajalvir, E-28850 Torrejon de Ardoz (Madrid) (Spain); Caton, Daniel B., E-mail: pet205@lehigh.edu [Appalachian State University, Boone, NC 28608 (United States)

    2013-09-20

    Spectra from the International Ultraviolet Explorer taken in 1989 September over one full orbital period of U Cephei (U Cep, HD 5796) are analyzed. The TLUSTY and SYNSPEC stellar atmospheric simulation programs are used to generate synthetic spectra to which U Cep continuum levels are normalized. Absorption lines attributed to the photosphere are divided out to isolate mass flow and accretion spectra. A radial velocity curve is constructed for conspicuous gas stream features, and shows evidence for a transient flow during secondary eclipse with outward velocities ranging between 200 and 350 km s{sup –1}, and a number density of (3 ± 2) × 10{sup 10} cm{sup –3}. The validity of C IV 1548 and 1550 and Si IV 1393 and 1402 lines are re-examined in the context of extreme rotational blending effects. A G-star to B-star mass transfer rate of (5 ± 4) × 10{sup –9} M{sub ☉} yr{sup –1} is calculated as an approximate upper limit, and a model system is presented.

  8. ULTRAVIOLET SPECTROSCOPIC ANALYSIS OF TRANSIENT MASS FLOW OUTBURST IN U CEPHEI

    International Nuclear Information System (INIS)

    Tupa, Peter R.; DeLeo, Gary G.; McCluskey, George E.; Kondo, Yoji; Sahade, Jorge; Giménez, Alvaro; Caton, Daniel B.

    2013-01-01

    Spectra from the International Ultraviolet Explorer taken in 1989 September over one full orbital period of U Cephei (U Cep, HD 5796) are analyzed. The TLUSTY and SYNSPEC stellar atmospheric simulation programs are used to generate synthetic spectra to which U Cep continuum levels are normalized. Absorption lines attributed to the photosphere are divided out to isolate mass flow and accretion spectra. A radial velocity curve is constructed for conspicuous gas stream features, and shows evidence for a transient flow during secondary eclipse with outward velocities ranging between 200 and 350 km s –1 , and a number density of (3 ± 2) × 10 10 cm –3 . The validity of C IV 1548 and 1550 and Si IV 1393 and 1402 lines are re-examined in the context of extreme rotational blending effects. A G-star to B-star mass transfer rate of (5 ± 4) × 10 –9 M ☉ yr –1 is calculated as an approximate upper limit, and a model system is presented

  9. Exploring the Connection between Parsec-scale Jet Activity and Broadband Outbursts in 3C 279

    Science.gov (United States)

    Rani, B.; Jorstad, S. G.; Marscher, A. P.; Agudo, I.; Sokolovsky, K. V.; Larionov, V. M.; Smith, P.; Mosunova, D. A.; Borman, G. A.; Grishina, T. S.; Kopatskaya, E. N.; Mokrushina, A. A.; Morozova, D. A.; Savchenko, S. S.; Troitskaya, Yu. V.; Troitsky, I. S.; Thum, C.; Molina, S. N.; Casadio, C.

    2018-05-01

    We use a combination of high-resolution very long baseline interferometry (VLBI) radio and multiwavelength flux density and polarization observations to constrain the physics of the dissipation mechanism powering the broadband flares in 3C 279 during an episode of extreme flaring activity in 2013–2014. Six bright flares superimposed on a long-term outburst are detected at γ-ray energies. Four of the flares have optical and radio counterparts. The two modes of flaring activity (faster flares sitting on top of a long-term outburst) present at radio, optical, and γ-ray frequencies are missing in X-rays. X-ray counterparts are only observed for two flares. The first three flares are accompanied by ejection of a new VLBI component (NC2), suggesting the 43 GHz VLBI core as the site of energy dissipation. Another new component, NC3, is ejected after the last three flares, which suggests that the emission is produced upstream from the core (closer to the black hole). The study therefore indicates multiple sites of energy dissipation in the source. An anticorrelation is detected between the optical percentage polarization (PP) and optical/γ-ray flux variations, while the PP has a positive correlation with optical/γ-ray spectral indices. Given that the mean polarization is inversely proportional to the number of cells in the emission region, the PP versus optical/γ-ray anticorrelation could be due to more active cells during the outburst than at other times. In addition to the turbulent component, our analysis suggests the presence of a combined turbulent and ordered magnetic field, with the ordered component transverse to the jet axis.

  10. Challenges in mechanical modeling of SFR fuel rod transient behavior

    Energy Technology Data Exchange (ETDEWEB)

    Feria, F.; Herranz, L. E.

    2013-07-01

    Modeling of SFR fuel rod mechanical behavior under transient conditions entails the development of a creep law to predict cladding viscoplastic strain. In this regard, this work is focused on defining a proper clad creep law structure as the basis to set a suitable model under SFR off-normal conditions as transient overpower and loss of fluid. To do so, a review of in-codes clad creep models has been done by using SAS-SFR, SCANAIR and ASTEC. The proposed creep model has been structured in two parts: viscoplastic behaviour before the failure (primary and secondary creep) and the failure due to viscoplastic collapse (tertiary creep). In order to model the first part, Norton creep law has been proposed as a conservative option. An irradiation hardening factor should be included for best estimate calculations. The recommendation for the second part is to apply a failure criterion based on strain limit or rupture time, which allows achieving conservative results.

  11. Behavioral Outbursts in a Child with a Deletion Syndrome, Generalized Epilepsy, Global Developmental Delay, and Failure to Thrive.

    Science.gov (United States)

    Lewis, Adam H; Chugh, Ankur; Sobotka, Sarah A

    2018-03-01

    A 7-year-old girl with 20q13.33 deletion and a history of generalized convulsive epilepsy presented to the Developmental and Behavioral Pediatrics Clinic due to concerns about her behavioral outbursts in the context of overall delayed development. Evaluation by the Developmental and Behavioral and Gastroenterology teams revealed failure to thrive (FTT) as the primary cause of the behavioral outbursts and developed a high-calorie, high-fat, high-protein nutritional counseling plan. Children who have FTT and a genetic disorder are often thought to not thrive because of their underlying genetic disorder; however, feeding skills and nutritional intake need to be thoroughly investigated before determining an etiology for FTT. Motoric, communicative, and developmental skills in children with genetic disorders may impede appropriate feeding mechanisms, inducing or exaggerating FTT in these children with developmental disabilities due to genetic etiologies. [Pediatr Ann. 2018;47(3):e130-e134.]. Copyright 2018, SLACK Incorporated.

  12. Characterizing Outbursts and Nucleus Properties of Comet 29P/Schwassmann-Wachmann 1

    Science.gov (United States)

    Fernandez, Yanga

    2015-10-01

    Today's comets are remnant bodies leftover from the era of planet formation in our own Solar System. Therefore characterizing cometary structure and composition can give clues to the thermal, physical, and chemical environment of the protoplanetary disk. However before this long-term 'holy grail' of planetary astronomy can be achieved, we must understand cometary evolution so that we can know how comets have changed since their formation. The phenomenon of cometary activity, where a porous matrix of icy and rocky material turns into the gases and the dust grains we see in a comet's coma, remains a poorly-understood puzzle of short-term cometary evolution. We are in the midst of an ongoing project to understand cometary activity in a particular comet, 29P/Schwassmann-Wachmann 1, by taking advantage of existing imaging datasets that show the comet in outburst. Outbursts are useful for constraining the nucleus's spin state and the location of active areas. We propose here to analyze archival WFPC2 images of comet 29P obtained in March 1996 (Cycle 5, Project 5829), spanning 21 hours, that show the comet in outburst. These data are the highest-resolution imaging of this comet ever obtained while it was in outburst. We will analyze the morphology of the comet's dust coma to constrain properties of the nucleus and of the dust grains themselves. Additionally, we will analyze images taken in May 2000 (Cycle 8, Project 8274) that show the comet at its steady-state level of activity but may also allow us to place further constraints on the nucleus's active regions.

  13. Determining air distribution during outbursts of gases and rocks

    Energy Technology Data Exchange (ETDEWEB)

    Struminski, A; Sikora, M; Urbanski, J [Politechnika Wroclawska (Poland). Instytut Gornictwa

    1989-01-01

    Discusses use of the KPW-1 iterative and autocorrelation method developed by A. Struminski for forecasting effects of rock bursts on ventilation systems of underground coal mines with increased content of methane or carbon dioxide in coal seams and adjacent rock strata. The method is used for prediction of air flow changes caused by a rock burst accompanied by violent outburst of gases. Directions of air flow, flow rate and concentration of gases emitted from surrounding strata to mine workings are predicted. On the basis of this prediction concentration of gases from a coal outburst is determined for any point in a ventilation network. The prediction method is used for assessing hazards for coal mines during and after a rock burst. Use of the method is explained on the example of the Thorez and Walbrzych coal mines. Computer programs developed for ODRA and IBM/XT computers are discussed. 6 refs.

  14. RXTE Observations of Anomalous X-ray Pulsar 1E 1547.0-5408 During and After its 2008 and 2009 Outbursts

    Science.gov (United States)

    Dib, Rim; Kaspi, Victoria M.; Scholz, Paul; Gavriil, Fotis P.

    2012-01-01

    We present the results of Rossi X-ray Timing Explorer (RXTE) and Swift monitoring observations of the magnetar 1E 1547.0-5408 following the pulsar's radiative outbursts in 2008 October and 2009 January. We report on a study of the evolution of the timing properties and the pulsed flux from 2008 October 4 through 2009 December 26. In our timing study, a phase-coherent analysis shows that for the first 29 days following the 2008 outburst, there was a very fast increase in the magnitude of the rotational frequency derivative upsilon-dot, such that upsilon-dot-dot was a factor of 60 larger than that reported in data from 2007. This upsilon-dot magnitude increase occurred in concert with the decay of the pulsed flux following the start of the 2008 event. Following the 2009 outburst, for the first 23 days, upsilon-dot-dot was consistent with zero, and upsilon-dot had returned to close to its 2007 value. In contrast to the 2008 event, the 2009 outburst showed a major increase in persistent flux, relatively little change in the pulsed flux, and sudden significant spectral hardening approx 15 days after the outburst. We show that, excluding the month following each of the outbursts, and because of the noise and the sparsity in the data, multiple plausible timing solutions fit the pulsar's frequency behavior. We note similarities in the behavior of 1E 1547.0-5408 following the 2008 outburst to that seen in the AXP 1E 1048.1-5937 following its 2001-2002 outburst and discuss this in terms of the magnetar model.

  15. Effect of axial stress on the transient mechanical response of 20%, cold-worked Type 316 stainless-steel cladding

    International Nuclear Information System (INIS)

    Yamada, H.

    1979-01-01

    To understand the effects of the fuel-cladding mechanical interaction on the failure of 20% cold-worked Type 316 stainless-steel cladding during anticipated nuclear reactor transients, the transient mechanical response of the cladding was investigated using a transient tube burst method at a heating rate of 5.6 0 C/s and axial-to-hoop-stress ratios in the range of 1/2 to 2. The failure temperatures were observed to remain essentially constant for the transient tests at axial-to-hoop-stress ratios between 1/2 and 1, but to decrease with an increase in axial-to-hoop-stress ratios above unity. The uniform diametral strains to failure were observed to decrease monotonically with an increase in axial-to-hoop-stress ratio from 1/2 to 2, and in general, the uniform axial strains to failure were observed to increase with an increase in axial-to-hoop-stress ratio. The fracture of the cladding during thermal transients was found to be strongly affected by the maximum principal stress but not by the effective stress

  16. Periodic outburst floods from an ice-dammed lake in East Greenland.

    Science.gov (United States)

    Grinsted, Aslak; Hvidberg, Christine S; Campos, Néstor; Dahl-Jensen, Dorthe

    2017-08-30

    We report evidence of four cycles of outburst floods from Catalina Lake, an ice-dammed lake in East Greenland, identified in satellite imagery between 1966-2016. The lake measures 20-25 km 2 , and lake level drops 130-150 m in each event, corresponding to a water volume of 2.6-3.4 Gt, and a release of potential energy of 10 16  J, among the largest outburst floods reported in historical times. The drainage cycle has shortened systematically, and the lake filling rate has increased over each cycle, suggesting that the drainage pattern is changing due to climate warming with possible implications for environmental conditions in Scoresbysund fjord.

  17. Transient hypoxia stimulates mitochondrial biogenesis in brain subcortex by a neuronal nitric oxide synthase-dependent mechanism

    Science.gov (United States)

    The adaptive mechanisms that protect brain metabolism during and after hypoxia, for instance, during hypoxic preconditioning, are coordinated in part by nitric oxide (NO). We tested the hypothesis that acute transient hypoxia stimulates NO synthase (NOS)-activated mechanisms of m...

  18. Near-infrared monitoring and modeling of V1647 Ori in its ongoing 2008–2012 outburst phase

    International Nuclear Information System (INIS)

    Raman, Veeman Venkata; Anandarao, Boddapati G.; Janardhan, Padmanabhan; Pandey, Rajesh

    2013-01-01

    We present results of the Mt Abu JHK photometric and HI Brackett γ line monitoring of the eruptive young stellar object V1647 Orionis (McNeil's Object) during its ongoing outburst phase in 2008–2012. We discuss JHK color patterns and extinction during the outburst and compare them with those from the previous outburst phase in 2004–2005 and in the intervening quiescent period that lasted about 2 yr. Commencing from early 2012, the object has shown a slow fading out in all the bands. We report brightness variations in the nearby Herbig-Haro object HH22 that are possibly associated with those in V1647 Ori. We also present modeling of the spectral energy distributions of V1647 Ori during both its recent outburst and its quiescent phase. The physical parameters of the protostar and its circumstellar environment obtained from the modeling indicate marked differences between the two phases

  19. High-velocity winds from a dwarf nova during outburst

    Science.gov (United States)

    Cordova, F. A.; Mason, K. O.

    1982-01-01

    An ultraviolet spectrum of the dwarf nova TW Vir during an optical outburst shows shortward-shifted absorption features with edge velocities as high as 4800 km/s, about the escape velocity of a white dwarf. A comparison of this spectrum with the UV spectra of other cataclysmic variables suggests that mass loss is evident only for systems with relatively high luminosities (more than about 10 solar luminosities) and low inclination angles with respect to the observer's line of sight. The mass loss rate for cataclysmic variables is of order 10 to the -11th solar mass per yr; this is from 0.01 to 0.001 of the mass accretion rate onto the compact star in the binary. The mass loss may occur by a mechanism similar to that invoked for early-type stars, i.e., radiation absorbed in the lines accelerates the accreting gas to the high velocities observed.

  20. Geochemical discrimination of five pleistocene Lava-Dam outburst-flood deposits, western Grand Canyon, Arizona

    Science.gov (United States)

    Fenton, C.R.; Poreda, R.J.; Nash, B.P.; Webb, R.H.; Cerling, T.E.

    2004-01-01

    Pleistocene basaltic lava dams and outburst-flood deposits in the western Grand Canyon, Arizona, have been correlated by means of cosmogenic 3He (3Hec) ages and concentrations of SiO2, Na2O, K2O, and rare earth elements. These data indicate that basalt clasts and vitroclasts in a given outburst-flood deposit came from a common source, a lava dam. With these data, it is possible to distinguish individual dam-flood events and improve our understanding of the interrelations of volcanism and river processes. At least five lava dams on the Colorado River failed catastrophically between 100 and 525 ka; subsequent outburst floods emplaced basalt-rich deposits preserved on benches as high as 200 m above the current river and up to 53 km downstream of dam sites. Chemical data also distinguishes individual lava flows that were collectively mapped in the past as large long-lasting dam complexes. These chemical data, in combination with age constraints, increase our ability to correlate lava dams and outburst-flood deposits and increase our understanding of the longevity of lava dams. Bases of correlated lava dams and flood deposits approximate the elevation of the ancestral river during each flood event. Water surface profiles are reconstructed and can be used in future hydraulic models to estimate the magnitude of these large-scale floods.

  1. Peak discharge of a Pleistocene lava-dam outburst flood in Grand Canyon, Arizona, USA

    Science.gov (United States)

    Fenton, Cassandra R.; Webb, Robert H.; Cerling, Thure E.

    2006-03-01

    The failure of a lava dam 165,000 yr ago produced the largest known flood on the Colorado River in Grand Canyon. The Hyaloclastite Dam was up to 366 m high, and geochemical evidence linked this structure to outburst-flood deposits that occurred for 32 km downstream. Using the Hyaloclastite outburst-flood deposits as paleostage indicators, we used dam-failure and unsteady flow modeling to estimate a peak discharge and flow hydrograph. Failure of the Hyaloclastite Dam released a maximum 11 × 10 9 m 3 of water in 31 h. Peak discharges, estimated from uncertainty in channel geometry, dam height, and hydraulic characteristics, ranged from 2.3 to 5.3 × 10 5 m 3 s -1 for the Hyaloclastite outburst flood. This discharge is an order of magnitude greater than the largest known discharge on the Colorado River (1.4 × 10 4 m 3 s -1) and the largest peak discharge resulting from failure of a constructed dam in the USA (6.5 × 10 4 m 3 s -1). Moreover, the Hyaloclastite outburst flood is the oldest documented Quaternary flood and one of the largest to have occurred in the continental USA. The peak discharge for this flood ranks in the top 30 floods (>10 5 m 3 s -1) known worldwide and in the top ten largest floods in North America.

  2. IOTA interferometer observations of the B[e] star/X-ray transient object CI Cam.

    Science.gov (United States)

    Thureau, N. D.; Traub, W.; Millan-Gabet, R.; Monnier, J. D.; Pedretti, E.; Berger, J.-P.; Schloerb, P.

    2005-12-01

    We present the results from an observing campaign on the star CI Cam carried out at the IOTA interferometer in November-December 2004 using the IONIC 3 telescope beam combiner in the H spectral band with projected baselines in the range 10-36m. CI Cam is a known B[e] star and X-ray transient source and has been intensively observed since its powerful X-ray, radio and optical outburst occurred in April 1998. Our visibility measurements put strong constraints on the nature of the source and we can rule out all existing SED models available in the literature. Our new results are in agreement with previous observations of CI Cam obtained with IOTA2 in the H and K' spectral bands in September-November 1998, indicating the infrared excess is long-lived and not directly associated with the outburst. We have explored new models that can better fit our observations. Additionally, we have measured small non-zero closure phases which are the signature of asymmetries in the brightness distribution function. Financial support for NDT is provided by the European Commission through a Marie Curie Outgoing International Fellowships MOIF-CT-2004-002990.

  3. Restablished Accretion in Post-outburst Classical Novae Revealed by X-rays

    Science.gov (United States)

    Hernanz, Margarita; Ferri, Carlo; Sala, Glòria

    2009-05-01

    Classical novae are explosions on accreting white dwarfs (hereinafter WDs) in cataclysmic variables (hereinafter CVs) a hydrogen thermonuclear runaway on top of the WD is responsible for the outburst. X-rays provide a unique way to study the turn-off of H-burning, because super soft X-rays reveal the hot WD photosphere, but also to understand how accretion is established again in the binary system. Observations with XMM-Newton of some post-outburst novae have revealed such a process, but a coverage up to larger energies -as Simbol-X will provide- is fundamental to well understand the characteristics of the binary system and of the nova ejecta. We present a brief summary of our results up to now and prospects for the Simbol-X mission.

  4. Probabilistic fracture mechanics analysis of boiling water reactor vessel for cool-down and low temperature over-pressurization transients

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jeong Soon; Choi, Young Hwan; Jhung, Myung Jo [Safety Research Division, Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

    2016-04-15

    The failure probabilities of the reactor pressure vessel (RPV) for low temperature over-pressurization (LTOP) and cool-down transients are calculated in this study. For the cool-down transient, a pressure-temperature limit curve is generated in accordance with Section XI, Appendix G of the American Society of Mechanical Engineers (ASME) code, from which safety margin factors are deliberately removed for the probabilistic fracture mechanics analysis. Then, sensitivity analyses are conducted to understand the effects of some input parameters. For the LTOP transient, the failure of the RPV mostly occurs during the period of the abrupt pressure rise. For the cool-down transient, the decrease of the fracture toughness with temperature and time plays a main role in RPV failure at the end of the cool-down process. As expected, the failure probability increases with increasing fluence, Cu and Ni contents, and initial reference temperature-nil ductility transition (RTNDT). The effect of warm prestressing on the vessel failure probability for LTOP is not significant because most of the failures happen before the stress intensity factor reaches the peak value while its effect reduces the failure probability by more than one order of magnitude for the cool-down transient.

  5. Transient-field strength measurements for 52Cr traversing Fe hosts at high velocity and polarization transfer mechanisms

    International Nuclear Information System (INIS)

    Stuchbery, A.E.; Doran, C.E.; Byrne, A.P.; Bolotin, H.H.; Dracoulis, G.D.

    1986-12-01

    Transient-field strengths were measured for 52 Cr ions traversing polarized Fe hosts at velocities up to 12v>=o (v>=o = c/137 = Bohr velocity). The results are compared with predictions of various transient field parametrizations and discussed in terms of possible mechanisms by which polarization might be transferred from the Fe host to inner vacancies of the moving Cr ions. The g-factor of the first 2 + state of 52 Cr was also measured by the transient field technique and found to be in accord with shell-model calculations

  6. X-Ray and Radio Observations of the Magnetar SGR J1935+2154 during Its 2014, 2015, and 2016 Outbursts

    Energy Technology Data Exchange (ETDEWEB)

    Younes, George; Kouveliotou, Chryssa; Van der Horst, Alexander J. [Department of Physics, The George Washington University, Washington, DC 20052 (United States); Jaodand, Amruta; Hessels, Jason W. T. [ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA Dwingeloo (Netherlands); Baring, Matthew G. [Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Harding, Alice K.; Gehrels, Neil [Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Gill, Ramandeep; Granot, Jonathan [Department of Natural Sciences, The Open University of Israel, 1 University Road, P.O. Box 808, Raánana 43537 (Israel); Huppenkothen, Daniela [Center for Data Science, New York University, 726 Broadway, 7th Floor, New York, NY 10003 (United States); Göğüş, Ersin [Sabancı University, Orhanlı-Tuzla, İstanbul 34956 (Turkey); Lin, Lin, E-mail: gyounes@gwu.edu [Department of Astronomy, Beijing Normal University, Beijing 100875 (China)

    2017-10-01

    We analyzed broadband X-ray and radio data of the magnetar SGR J1935+2154 taken in the aftermath of its 2014, 2015, and 2016 outbursts. The source soft X-ray spectrum <10 keV is well described with a blackbody+power-law (BB+PL) or 2BB model during all three outbursts. Nuclear Spectroscopic Telescope Array observations revealed a hard X-ray tail, with a PL photon index Γ = 0.9, extending up to 50 keV, with flux comparable to the one detected <10 keV. Imaging analysis of Chandra data did not reveal small-scale extended emission around the source. Following the outbursts, the total 0.5–10 keV flux from SGR J1935+2154 increased in concordance to its bursting activity, with the flux at activation onset increasing by a factor of ∼7 following its strongest 2016 June outburst. A Swift /X-Ray Telescope observation taken 1.5 days prior to the onset of this outburst showed a flux level consistent with quiescence. We show that the flux increase is due to the PL or hot BB component, which increased by a factor of 25 compared to quiescence, while the cold BB component kT = 0.47 keV remained more or less constant. The 2014 and 2015 outbursts decayed quasi-exponentially with timescales of ∼40 days, while the stronger 2016 May and June outbursts showed a quick short-term decay with timescales of about four days. Our Arecibo radio observations set the deepest limits on the radio emission from a magnetar, with a maximum flux density limit of 14 μ Jy for the 4.6 GHz observations and 7 μ Jy for the 1.4 GHz observations. We discuss these results in the framework of the current magnetar theoretical models.

  7. The outbursts of the comet 29P/Schwassmann-Wachmann 1: A new approach to the old problem

    Science.gov (United States)

    Gronkowski, P.

    2014-02-01

    As far as outbursts activity is concerned, the 29P/Schwassmann-Wachmann 1 is the exceptional comet. This Centaur object shows quasi-regular flares with periodicities of 50 days eriodicity (Trigo-Rodriguez et al. 2010). In the introductory part of the presented paper the most well-known hypotheses which try to explain this cometary behaviour are reviewed. The second, actual part of this paper presents the new model for the outburst activity of this comet. The model is based on the idea of Ipatov (2012), according to which there are large cavities %%in comets %%with material under gas pressure, below a considerable fraction of the comet's surface containing material under high gas pressure. In favourite conditions the surface layers over the cavities are thrown away and the interior of these cavities is exposed. Consequently, an outburst of the comet's brightness may be observed. The main characteristics of an outburst of this comet, the brightness jump, %%in its brightness is calculated. Numerical simulations were carried out for wide range of possible cometary parameters. The obtained results are in good agreement with the real observations.

  8. WATCHDOG: A COMPREHENSIVE ALL-SKY DATABASE OF GALACTIC BLACK HOLE X-RAY BINARIES

    International Nuclear Information System (INIS)

    Tetarenko, B. E.; Sivakoff, G. R.; Heinke, C. O.; Gladstone, J. C.

    2016-01-01

    With the advent of more sensitive all-sky instruments, the transient universe is being probed in greater depth than ever before. Taking advantage of available resources, we have established a comprehensive database of black hole (and black hole candidate) X-ray binary (BHXB) activity between 1996 and 2015 as revealed by all-sky instruments, scanning surveys, and select narrow-field X-ray instruments on board the INTErnational Gamma-Ray Astrophysics Laboratory, Monitor of All-Sky X-ray Image, Rossi X-ray Timing Explorer, and Swift telescopes; the Whole-sky Alberta Time-resolved Comprehensive black-Hole Database Of the Galaxy or WATCHDOG. Over the past two decades, we have detected 132 transient outbursts, tracked and classified behavior occurring in 47 transient and 10 persistently accreting BHs, and performed a statistical study on a number of outburst properties across the Galactic population. We find that outbursts undergone by BHXBs that do not reach the thermally dominant accretion state make up a substantial fraction (∼40%) of the Galactic transient BHXB outburst sample over the past ∼20 years. Our findings suggest that this “hard-only” behavior, observed in transient and persistently accreting BHXBs, is neither a rare nor recent phenomenon and may be indicative of an underlying physical process, relatively common among binary BHs, involving the mass-transfer rate onto the BH remaining at a low level rather than increasing as the outburst evolves. We discuss how the larger number of these “hard-only” outbursts and detected outbursts in general have significant implications for both the luminosity function and mass-transfer history of the Galactic BHXB population

  9. NuSTAR and SWIFT Observations of the Black Hole Candidate XTE J1908+094 during its 2013 Outburst

    DEFF Research Database (Denmark)

    Tao, Lian; Tomsick, John A.; Walton, Dominic J.

    2015-01-01

    The black hole (BH) candidate XTE J1908+094 went into outburst for the first time since 2003 in 2013 October. We report on an observation with the Nuclear Spectroscopic Telescope Array (NuSTAR) and monitoring observations with Swift during the outburst. NuSTAR caught the source in the soft state...

  10. Transient Oscilliations in Mechanical Systems of Automatic Control with Random Parameters

    Science.gov (United States)

    Royev, B.; Vinokur, A.; Kulikov, G.

    2018-04-01

    Transient oscillations in mechanical systems of automatic control with random parameters is a relevant but insufficiently studied issue. In this paper, a modified spectral method was applied to investigate the problem. The nature of dynamic processes and the phase portraits are analyzed depending on the amplitude and frequency of external influence. It is evident from the obtained results, that the dynamic phenomena occurring in the systems with random parameters under external influence are complex, and their study requires further investigation.

  11. A capacitively coupled dose-rate-dependent transient upset mechanism in a bipolar memory

    International Nuclear Information System (INIS)

    Turfler, R.M.; Pease, R.L.; Dinger, G.; Armstrong, B.

    1992-01-01

    This paper reports on a pattern sensitivity that was observed in the threshold dose rate response of a bipolar 16K PROM for radiation pulse widths of 20-100 ns. For the worst case pattern, the upset threshold was a factor of three lower than for the commonly used checkerboard pattern. The mechanism for this pattern sensitivity was found to be a capacitively coupled voltage transient on a sensitive node which caused a low-to-high transition at the output. A design fix was implemented to significantly alter the ratio of the two parasitic capacitances in a capacitive divider which reduced the amplitude of the voltage transient at the sensitive node. It was demonstrated that in the redesign, the pattern sensitivity was eliminated

  12. X-Ray Observations of the Black Hole Transient 4U 1630-47 during 2 Years of X-Ray Activity

    Science.gov (United States)

    Tomsick, John A.; Corbel, Stéphane; Goldwurm, Andrea; Kaaret, Philip

    2005-09-01

    The black hole candidate (BHC) X-ray transient 4U 1630-47 continuously produced strong X-ray emission for more than 2 years during its 2002-2004 outburst, which is one of the brightest and longest outbursts ever seen from this source. We use more than 300 observations made with the Rossi X-Ray Timing Explorer (RXTE) to study the source throughout the outburst, along with hard X-ray images from the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), which are critical for interpreting the RXTE data in this crowded field. The source exhibits extreme behaviors, which can be interpreted as an indication that the system luminosity approaches the Eddington limit. For 15 observations, fitting the spectral continuum with a disk-blackbody plus power-law model results in measured inner disk temperatures between 2.7 and 3.8 keV, and such temperatures are only rivaled by the brightest BHC systems, such as GRS 1915+105 and XTE J1550-564. If the high temperatures are caused by the dominance of electron scattering opacity in the inner regions of the accretion disk, it is theoretically required that the source luminosity be considerably higher than 20% of the Eddington limit. We detect a variety of high-amplitude variability, including hard 10-100 s flares, which peak at levels as much as 2-3 times higher than nonflare levels. This flaring occurs at the highest disk luminosities in a regime in which the source deviates from the Ldisk~T4in relationship that is seen at lower luminosities, possibly suggesting that we are seeing transitions between a Shakura & Sunyaev disk and a ``slim'' disk, which is predicted to occur at very high mass accretion rates. The X-ray properties in 2002-2004 are significantly different from those seen during the 1998 outburst, which is the only outburst with detected radio jet emission. Our results support the ``jet line'' concept recently advanced by Fender and coworkers. Our study allows for a test of the quantitative McClintock & Remillard

  13. Underlying mechanisms of transient luminous events: a review

    Directory of Open Access Journals (Sweden)

    V. V. Surkov

    2012-08-01

    Full Text Available Transient luminous events (TLEs occasionally observed above a strong thunderstorm system have been the subject of a great deal of research during recent years. The main goal of this review is to introduce readers to recent theories of electrodynamics processes associated with TLEs. We examine the simplest versions of these theories in order to make their physics as transparent as possible. The study is begun with the conventional mechanism for air breakdown at stratospheric and mesospheric altitudes. An electron impact ionization and dissociative attachment to neutrals are discussed. A streamer size and mobility of electrons as a function of altitude in the atmosphere are estimated on the basis of similarity law. An alternative mechanism of air breakdown, runaway electron mechanism, is discussed. In this section we focus on a runaway breakdown field, characteristic length to increase avalanche of runaway electrons and on the role played by fast seed electrons in generation of the runaway breakdown. An effect of thunderclouds charge distribution on initiation of blue jets and gigantic jets is examined. A model in which the blue jet is treated as upward-propagating positive leader with a streamer zone/corona on the top is discussed. Sprite models based on streamer-like mechanism of air breakdown in the presence of atmospheric conductivity are reviewed. To analyze conditions for sprite generation, thunderstorm electric field arising just after positive cloud-to-ground stroke is compared with the thresholds for propagation of positively/negatively charged streamers and with runway breakdown. Our own estimate of tendril's length at the bottom of sprite is obtained to demonstrate that the runaway breakdown can trigger the streamer formation. In conclusion we discuss physical mechanisms of VLF (very low frequency and ELF (extremely low frequency phenomena associated with sprites.

  14. Hydro-morphodynamic modelling of a volcano-induced sediment-laden outburst flood at Sólheimajökull, Iceland

    Science.gov (United States)

    Guan, M.; Wright, N.; Sleigh, P. A.; Carrivick, J.; Staines, K.

    2013-12-01

    Outburst floods are one of the most catastrophic natural hazards for populations and infrastructure. Such high-magnitude sudden onset floods generally comprise of an advancing intense kinematic water wave that can induce considerable sediment transport. The exploration and investigation of sediment-laden outburst floods cannot be limited solely to water flow but must also include the flood-induced sediment transport. Understanding the complex flow-bed interaction process in large (field) scale outburst floods is still limited, not least due to a lack of well-constrained field data, but also because consensus on appropriate modelling schemes has yet to be decided. In recent years, attention has focussed on the numerical models capable of describing the process of erosion, transport and deposition in such flows and they are now at a point at which they provide useful quantitative data. Although the "exact" measure of bed change is still unattainable the numerical models enhance and improve insights into large outburst flood events. In this study, a volcano-induced jökulhlaup or glacial outburst flood (GLOF) at Sólheimajökull, Iceland is reproduced by novel 2D hydro-morphodynamic model that considers both bedload and suspended load based on shallow water theory. The simulation of sediment-laden outburst flood is shown to perform well, with further insights into the flow-bed interaction behaviour obtained from the modelling output. These results are beneficial to flood risk management and hazard prevention and mitigation. In summary, the modelling outputs show that (1) the quantity of bed erosion and deposition are sensitive to the sediment gain size, yet, the influences are not so significant when considering flow discharge; (2) finer resolution of topography increases the computational time significantly yet the results are not affected correspondingly; (3) the bed changes simulated by the present model achieves reasonably good agreement with those by the

  15. NuSTAR and XMM-Newton Observations of the 2015 Outburst Decay of GX 339-4

    Energy Technology Data Exchange (ETDEWEB)

    Stiele, H.; Kong, A. K. H., E-mail: hstiele@mx.nthu.edu.tw [National Tsing Hua University, Department of Physics and Institute of Astronomy, No. 101 Sect. 2 Kuang-Fu Road, 30013, Hsinchu, Taiwan (China)

    2017-07-20

    The extent of the accretion disk in the low/hard state of stellar mass black hole X-ray binaries remains an open question. There is some evidence suggesting that the inner accretion disk is truncated and replaced by a hot flow, while the detection of relativistic broadened iron emission lines seems to require an accretion disk extending fully to the innermost stable circular orbit. We present comprehensive spectral and timing analyses of six Nuclear Spectroscopic Telescope Array and XMM-Newton observations of GX 339–4 taken during outburst decay in the autumn of 2015. Using a spectral model consisting of a thermal accretion disk, Comptonized emission, and a relativistic reflection component, we obtain a decreasing photon index, consistent with an X-ray binary during outburst decay. Although we observe a discrepancy in the inner radius of the accretion disk and that of the reflector, which can be attributed to the different underlying assumptions in each model, both model components indicate a truncated accretion disk that resiles with decreasing luminosity. The evolution of the characteristic frequency in Fourier power spectra and their missing energy dependence support the interpretation of a truncated and evolving disk in the hard state. The XMM-Newton data set allowed us to study, for the first time, the evolution of the covariance spectra and ratio during outburst decay. The covariance ratio increases and steeps during outburst decay, consistent with increased disk instabilities.

  16. Experimental Analyses of the Major Parameters Affecting the Intensity of Outbursts of Coal and Gas

    Science.gov (United States)

    Nie, W.; Peng, S. J.; Xu, J.; Liu, L. R.; Wang, G.; Geng, J. B.

    2014-01-01

    With an increase in mining depth and production, the intensity and frequency of outburst of coal and gas have a tendency to increase. Estimating the intensity of outbursts of coal and gas plays an important role because of its relation with the risk value. In this paper, we described the semiquantitative relations between major parameters and intensity of outburst based on physical experiments. The results showed increment of geostress simulated by horizontal load (from 1.4, 2.4, 3.2, to 3.4 MPa) or vertical load (from 2, 3, 3.6, to 4 MPa) improved the relative intensity rate (3.763–7.403% and 1.273–7.99%); the increment of porosity (from 1.57, 2.51, 3, to 3.6%) improved the relative intensity rate from 3.8 to 13.8%; the increment of gas pressure (from 0, 0.5, 0.65, 0.72, 1, to 1.5 Mpa) induced the relative intensity rate to decrease from 38.22 to 0%; the increment of water content (from 0, 2, 4, to 8%) caused the relative intensity rate to drop from 5.425 to 0.5%. Furthermore, sensitivity and range analysis evaluates coupled factors affecting the relative intensity. In addition, the distinction with initiation of outburst of coal and gas affected by these parameters is discussed by the relative threshold of gas content rate. PMID:25162042

  17. Effect of vortex generators on the closing transient flow of bileaflet mechanical heart valves

    Science.gov (United States)

    Murphy, David; Dasi, Lakshmi; Yoganathan, Ajit; Glezer, Ari

    2006-11-01

    The time-periodic closing of bileaflet mechanical heart valves is accompanied by a strong flow transient that is associated with the formation of a counter-rotating vortex pair near the b-datum line of leaflet edges. The strong transitory shear that is generated by these vortices may be damaging to blood elements and may result in platelet activation. In the present work, these flow transients are mitigated using miniature vortex generator arrays that are embedded on the surface of the leaflets. Two vortex generator designs were investigated: one design comprised staggered rectangular fins and the other one staggered hemispheres. The closing transients in the absence and presence of the passive vortex generators are characterized using phase locked PIV measurements. The study utilizes a 25 mm St. Jude Medical valve placed in the aortic position of the Georgia Tech left heart simulator. Measurements of the velocity field in the center plane of the leaflets demonstrate that the dynamics of the transient vortices that precede the formation of the leakage jets can be significantly altered and controlled by relatively simple passive modifications of existing valve designs. Human blood experiments validated the effectiveness of miniature vortex generators in reducing thrombus formation by over 42 percent.

  18. X-Ray Outburst from Young Star in McNeil's Nebula

    Science.gov (United States)

    2004-07-01

    Observations with NASA's Chandra X-ray Observatory captured an X-ray outburst from a young star, revealing a probable scenario for the intermittent brightening of the recently discovered McNeil's Nebula. It appears the interaction between the young star's magnetic field and an orbiting disk of gas can cause dramatic, episodic increases in the light from the star and disk, illuminating the surrounding gas. "The story of McNeil's Nebula is a wonderful example of the importance of serendipity in science," said Joel Kastner of the Rochester Institute of Technology in Rochester, New York, lead author of a paper in the July 22 issue of Nature describing the X-ray results. "Visible-light images were made of this region several months before Jay McNeil made his discovery, so it could be determined approximately when and by how much the star flared up to produce McNeil's Nebula." The small nebula, which lies in the constellation Orion about 1300 light years from Earth, was discovered with a 3-inch telescope by McNeil, an amateur astronomer from Paducah, Kentucky, in January 2004. In November 2002, a team led by Ted Simon of the Institute for Astronomy in Hawaii had observed the star-rich region with Chandra in search of young, X-ray emitting stars, and had detected several objects. Optical and infrared astronomers had, as part of independent surveys, also observed the region about a year later, in 2003. After the announcement of McNeil's discovery, optical, infrared and X-ray astronomers rushed to observe the region again. They found that a young star buried in the nebula had flared up, and was illuminating the nebula. This star was coincident with one of the X-ray sources discovered earlier by Simon. Chandra observations obtained by Kastner's group just after the optical outburst showed that the source had brightened fifty-fold in X-rays when compared to Simon's earlier observation. The visible-light eruption provides evidence that the cause of the X-ray outburst is the

  19. Optical, UV, and EUV Oscillations of SS Cygni in Outburst

    Science.gov (United States)

    Mauche, Christopher W.

    2004-07-01

    I provide a review of observations in the optical, UV (HST), and EUV (EUVE and Chandra LETG) of the rapid periodic oscillations of nonmagnetic, disk-accreting, high mass-accretion rate cataclysmic variables (CVs), with particular emphasis on the dwarf nova SS Cyg in outburst. In addition, I drawn attention to a correlation, valid over nearly six orders of magnitude in frequency, between the frequencies of the quasi-periodic oscillations (QPOs) of white dwarf, neutron star, and black hole binaries. This correlation identifies the high frequency quasi-coherent oscillations (so-called ``dwarf nova oscillations'') of CVs with the kilohertz QPOs of low mass X-ray binaries (LMXBs), and the low frequency and low coherence QPOs of CVs with the horizontal branch oscillations (or the broad noise component identified as such) of LMXBs. Assuming that the same mechanisms produce the QPOs of white dwarf, neutron star, and black hole binaries, this correlation has important implications for QPO models.

  20. Isotopic ratios in outbursting comet C/2015 ER61

    Science.gov (United States)

    Yang, Bin; Hutsemékers, Damien; Shinnaka, Yoshiharu; Opitom, Cyrielle; Manfroid, Jean; Jehin, Emmanuël; Meech, Karen J.; Hainaut, Olivier R.; Keane, Jacqueline V.; Gillon, Michaël

    2018-02-01

    Isotopic ratios in comets are critical to understanding the origin of cometary material and the physical and chemical conditions in the early solar nebula. Comet C/2015 ER61 (PANSTARRS) underwent an outburst with a total brightness increase of 2 magnitudes on the night of 2017 April 4. The sharp increase in brightness offered a rare opportunity to measure the isotopic ratios of the light elements in the coma of this comet. We obtained two high-resolution spectra of C/2015 ER61 with UVES/VLT on the nights of 2017 April 13 and 17. At the time of our observations, the comet was fading gradually following the outburst. We measured the nitrogen and carbon isotopic ratios from the CN violet (0, 0) band and found that 12C/13C = 100 ± 15, 14N/15N = 130 ± 15. In addition, we determined the 14N/15N ratio from four pairs of NH2 isotopolog lines and measured 14N/15N = 140 ± 28. The measured isotopic ratios of C/2015 ER61 do not deviate significantly from those of other comets.

  1. The application of a coupled artificial neural network and fault tree analysis model to predict coal and gas outbursts

    Energy Technology Data Exchange (ETDEWEB)

    Ruilin, Zhang [School of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo, Henan Province, 454003, PR (China); Lowndes, Ian S. [Process and Environmental Research Division, Faculty of Engineering, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom)

    2010-11-01

    This paper proposes the use of a coupled fault tree analysis (FTA) and artificial neural network (ANN) model to improve the prediction of the potential risk of coal and gas outburst events during the underground mining of thick and deep Chinese coal seams. The model developed has been used to investigate the gas emission characteristics and the geological conditions that exist within the Huaibei coal mining region, Anhui province, China. The coal seams in this region exhibit a high incidence of coal and gas outbursts. An analysis of the results obtained from an initial application of an FTA model, identified eight dominant model parameters related to the gas content or geological conditions of the coal seams, which characterize the potential risk of in situ coal and gas outbursts. The eight dominant model parameters identified by the FTA method were subsequently used as input variables to an ANN model. The results produced by the ANN model were used to develop a qualitative risk index to characterize the potential risk level of occurrence of coal and gas outburst events. Four different potential risk alarm levels were defined: SAFE, POTENTIAL, HIGH and STRONG. Solutions to the prediction model were obtained using a combination of quantitative and qualitative data including the gas content or gas pressure and the geological and geotechnical conditions of coal seams. The application of this combined solution method identified more explicit and accurate model relationships between the in situ geological conditions and the potential risk of coal and gas outbursts. An analysis of the model solutions concluded that the coupled FTA and ANN model may offer a reliable alternative method to forecast the potential risk of coal and gas outbursts. (author)

  2. Evolution of the accretion structure of the compact object in the symbiotic binary BF Cygni during outburst in 2009-2014

    Science.gov (United States)

    Tomov, N. A.; Tomova, M. T.; Bisikalo, D. V.

    2017-12-01

    The eclipsing symbiotic binary BF Cyg has had five orbital minima during its last optical outburst after 2006. The second minimum is much shallower than the first one and after that the minimum get deeper again. We determined the parameters of the accretion structure surrounding the compact object in two minima and traced its evolution until 2014. Moreover, we analysed the continuum of the system in the region of the UBVRCIC photometric bands to derive the parameters of its components at two times orbital maximum and calculated the mass-loss rate of the compact object. The results obtained allow us to conclude about the mechanism of fading of the optical light of the system until 2014. These results show that the optical flux of the outbursted compact object decreases because of "contraction" of its observed photosphere (pseudophotosphere) which, on its side, is due to increase of the velocity of its stellar wind, and the optical flux of the circumbinary nebula decreases mainly because of reduction of its mean density, which, on its side, is due to destruction of the accretion structure.

  3. Helical Root Buckling: A Transient Mechanism for Stiff Interface Penetration

    Science.gov (United States)

    Silverberg, Jesse; Noar, Roslyn; Packer, Michael; Harrison, Maria; Cohen, Itai; Henley, Chris; Gerbode, Sharon

    2011-03-01

    Tilling in agriculture is commonly used to loosen the topmost layer of soil and promote healthy plant growth. As roots navigate this mechanically heterogeneous environment, they encounter interfaces between the compliant soil and the underlying compacted soil. Inspired by this problem, we used 3D time-lapse imaging of Medicago Truncatula plants to study root growth in two-layered transparent hydrogels. The layers are mechanically distinct; the top layer is more compliant than the bottom. We observe that the roots form a transient helical structure as they attempt to penetrate the bi-layer interface. Interpreting this phenotype as a form of buckling due to root elongation, we measured the helix size as a function of the surrounding gel modulus. Our measurements show that by twisting the root tip during growth, the helical structure recruits the surrounding medium for an enhanced penetration force allowing the plants access to the lower layer of gel.

  4. The 2011 Outburst of Recurrent Nova T Pyx: X-Ray Observations Expose the White Dwarf Mass and Ejection Dynamics

    Science.gov (United States)

    Chomiuk, Laura; Nelson, Thomas; Mukai, Koji; Solokoski, J. L.; Rupen, Michael P.; Page, Kim L.; Osborne, Julian P.; Kuulkers, Erik; Mioduszewski, Amy J.; Roy, Nirupam; hide

    2014-01-01

    The recurrent nova T Pyx underwent its sixth historical outburst in 2011, and became the subject of an intensive multi-wavelength observational campaign.We analyze data from the Swift and Suzaku satellites to produce a detailed X-ray light curve augmented by epochs of spectral information. X-ray observations yield mostly non-detections in the first four months of outburst, but both a super-soft and hard X-ray component rise rapidly after Day 115. The super-soft X-ray component, attributable to the photosphere of the nuclear-burning white dwarf, is relatively cool (approximately 45 electron volts) and implies that the white dwarf in T Pyx is significantly below the Chandrasekhar mass (approximately 1 M). The late turn-on time of the super-soft component yields a large nova ejecta mass (approximately greater than 10(exp -5) solar mass), consistent with estimates at other wavelengths. The hard X-ray component is well fit by a approximately 1 kiloelectron volt thermal plasma, and is attributed to shocks internal to the 2011 nova ejecta. The presence of a strong oxygen line in this thermal plasma on Day 194 requires a significantly super-solar abundance of oxygen and implies that the ejecta are polluted by white dwarf material. The X-ray light curve can be explained by a dual-phase ejection, with a significant delay between the first and second ejection phases, and the second ejection finally released two months after outburst. A delayed ejection is consistent with optical and radio observations of T Pyx, but the physical mechanism producing such a delay remains a mystery.

  5. The Aftermath of the Largest Cometary Outburst in Recorded History - An In-Depth Study of Comet 17P/Holmes

    Science.gov (United States)

    Stevenson, Rachel Ann

    On UT 2007 Oct. 23, Jupiter Family comet 17P/Holmes underwent the largest cometary outburst in recorded history when it brightened by a factor of nearly a million in less than 2 days. This unprecedented event prompted a four-month observing campaign to observe the aftermath of the outburst. The wide field imager, MegaCam mounted on the Canada-France-Hawaii telescope was used to obtain r' images of the nucleus and the rapidly expanding dust coma. These images are unequaled in their quality and scope, and form a unique dataset with which to study the outburst aftermath. This original work examines the morphology of the outburst, and constrains the characteristics of the ejected material. Spatial filtering of images obtained in 2007 Nov. revealed numerous fragments moving away from the nucleus. The fragments were too bright to have been inactive, monolithic blocks and must have been acting as mini-comets with their own sources of sublimating volatiles and dust comae. They represented a significant (~ 10%) of the total ejected mass. The fragments had unusually high velocities relative to the nucleus, suggesting that they were accelerated by high gas pressure inside the nucleus prior to ejection. This work presents the first detection of such large, rapidly moving cometary fragments. The scarcity of similar ejecta around other fragmenting comets may be due to observational biases, rather than being unique to 17P/Holmes. Aperture photometry was used to study the evolution of the inner coma, which faded rapidly in the weeks and months following the initial outburst. Despite the observed fading, the nucleus must have remained active, continuing to supply fresh material to the inner coma. A second, much smaller outburst was detected on UT 2007 Nov. 12, which released an estimated 106 kg of dust into the inner coma. The secondary outburst showed that the nucleus remained unstable for several weeks after the initial event. Surface brightness profiles of the inner coma were

  6. On the 2011 Outburst of the Recurrent Nova T Pyxidis

    Directory of Open Access Journals (Sweden)

    L. Izzo

    2015-02-01

    Full Text Available We discuss the nebular phase emission during the 2011 outburst of the recurrent nova T Pyxidis and present preliminaryresults on the analysis of the line profiles. We also present some discussions about the binary system configurations and the X-ray emission, showing that the white dwarf mass should be larger than 0.8 MΘ.

  7. THE 2008 OUTBURST IN THE YOUNG STELLAR SYSTEM Z CMa: THE FIRST DETECTION OF TWIN JETS

    International Nuclear Information System (INIS)

    Whelan, E. T.; Dougados, C.; Bonnefoy, M.; Bouvier, J.; Chauvin, G.; Garcia, P. J. V.; Malbet, F.; Perrin, M. D.; Bains, I.; Redman, M. P.; Ray, T. P.; Bouy, H.; Benisty, M.; Grankvin, K.

    2010-01-01

    The Z CMa binary is understood to undergo both FU Orionis (FUOR) and EX Orionis (EXOR) type outbursts. While the SE component has been spectroscopically classified as an FUOR, the NW component, a Herbig Be star, is the source of the EXOR outbursts. The system has been identified as the source of a large outflow; however, previous studies have failed to identify the driver. Here, we present adaptive optics assisted [Fe II] spectro-images which reveal for the first time the presence of two small-scale jets. Observations made using OSIRIS at the Keck Observatory show the Herbig Be star to be the source of the parsec-scale outflow, which within 2'' of the source shows signs of wiggling and the FUOR to be driving a ∼0.''4 jet. The wiggling of the Herbig Be star's jet is evidence for an additional companion which could in fact be generating the EXOR outbursts, the last of which began in 2008. Indeed, the dynamical scale of the wiggling corresponds to a timescale of 4-8 years which is in agreement with the timescale of these outbursts. The spectro-images also show a bow-shock-shaped feature and possible associated knots. The origin of this structure is as of yet unclear. Finally, interesting low velocity structure is also observed. One possibility is that it originates in a wide-angle outflow launched from a circumbinary disk.

  8. DETECTION OF REMNANT DUST CLOUD ASSOCIATED WITH THE 2007 OUTBURST OF 17P/HOLMES

    International Nuclear Information System (INIS)

    Ishiguro, Masateru; Kim, Yoonyoung; Kwon, Yuna G.; Sarugaku, Yuki; Kuroda, Daisuke; Maehara, Hiroyuki; Hanayama, Hidekazu; Takahashi, Jun; Terai, Tsuyoshi; Usui, Fumihiko; Vaubaillon, Jeremie J.; Morokuma, Tomoki; Kobayashi, Naoto; Watanabe, Jun-ichi

    2016-01-01

    This article reports a new optical observation of 17P/Holmes one orbital period after the historical outburst event in 2007. We detected not only a common dust tail near the nucleus but also a long narrow structure that extended along the position angle 274.°6 ± 0.°1 beyond the field of view (FOV) of the Kiso Wide Field Camera, i.e., >0.°2 eastward and >2.°0 westward from the nuclear position. The width of the structure decreased westward with increasing distance from the nucleus. We obtained the total cross section of the long extended structure in the FOV, C FOV  = (2.3 ± 0.5) × 10 10 m 2 . From the position angle, morphology, and mass, we concluded that the long narrow structure consists of materials ejected during the 2007 outburst. On the basis of the dynamical behavior of dust grains in the solar radiation field, we estimated that the long narrow structure would be composed of 1 mm–1 cm grains having an ejection velocity of >50 m s −1 . The velocity was more than one order of magnitude faster than that of millimeter–centimeter grains from typical comets around a heliocentric distance r h of 2.5 AU. We considered that sudden sublimation of a large amount of water-ice (≈10 30 mol s −1 ) would be responsible for the high ejection velocity. We finally estimated a total mass of M TOT  = (4–8) × 10 11 kg and a total kinetic energy of E TOT  = (1–6) × 10 15 J for the 2007 outburst ejecta, which are consistent with those of previous studies that were conducted soon after the outburst

  9. Challenges in understanding, modelling, and mitigating Lake Outburst Flood Hazard: experiences from Central Asia

    Science.gov (United States)

    Mergili, Martin; Schneider, Demian; Andres, Norina; Worni, Raphael; Gruber, Fabian; Schneider, Jean F.

    2010-05-01

    Lake Outburst Floods can evolve from complex process chains like avalanches of rock or ice that produce flood waves in a lake which may overtop and eventually breach glacial, morainic, landslide, or artificial dams. Rising lake levels can lead to progressive incision and destabilization of a dam, to enhanced ground water flow (piping), or even to hydrostatic failure of ice dams which can cause sudden outflow of accumulated water. These events often have a highly destructive potential because a large amount of water is released in a short time, with a high capacity to erode loose debris, leading to a powerful debris flow with a long travel distance. The best-known example of a lake outburst flood is the Vajont event (Northern Italy, 1963), where a landslide rushed into an artificial lake which spilled over and caused a flood leading to almost 2000 fatalities. Hazards from the failure of landslide dams are often (not always) fairly manageable: most breaches occur in the first few days or weeks after the landslide event and the rapid construction of a spillway - though problematic - has solved some hazardous situations (e.g. in the case of Hattian landslide in 2005 in Pakistan). Older dams, like Usoi dam (Lake Sarez) in Tajikistan, are usually fairly stable, though landsildes into the lakes may create floodwaves overtopping and eventually weakening the dams. The analysis and the mitigation of glacial lake outburst flood (GLOF) hazard remains a challenge. A number of GLOFs resulting in fatalities and severe damage have occurred during the previous decades, particularly in the Himalayas and in the mountains of Central Asia (Pamir, Tien Shan). The source area is usually far away from the area of impact and events occur at very long intervals or as singularities, so that the population at risk is usually not prepared. Even though potentially hazardous lakes can be identified relatively easily with remote sensing and field work, modeling and predicting of GLOFs (and also

  10. A delayed transition to the hard state for 4U 1630-47 at the end of its 2010 outburst

    Energy Technology Data Exchange (ETDEWEB)

    Tomsick, John A. [Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450 (United States); Yamaoka, Kazutaka [Solar-Terrestrial Environment Laboratory, Department of Particles and Astronomy, Nagoya University, Furocho, Chikusa-ku, Nagoya, Aichi 464-8601 (Japan); Corbel, Stephane [AIM - Unité Mixte de Recherche CEA - CNRS - Université Paris VII - UMR 7158, CEA-Saclay, Service d' Astrophysique, F-91191 Gif-sur-Yvette Cedex (France); Kalemci, Emrah [Sabanci University, Orhanli-Tuzla, Istanbul 34956 (Turkey); Migliari, Simone [Department d' Astronomia i Meteorologia, Universitat de Barcelona, Marti I Franques 1, E-08028 Barcelona (Spain); Kaaret, Philip, E-mail: jtomsick@ssl.berkeley.edu [Department of Physics and Astronomy, University of Iowa, Van Allen Hall, Iowa City, IA 52242 (United States)

    2014-08-10

    Here we report on Swift and Suzaku observations near the end of an outburst from the black hole transient 4U 1630-47 and Chandra observations when the source was in quiescence. 4U 1630-47 made a transition from a soft state to the hard state ∼50 days after the main outburst ended. During this unusual delay, the flux continued to drop, and one Swift measurement found the source with a soft spectrum at a 2-10 keV luminosity of L = 1.07 × 10{sup 35} erg s{sup –1} for an estimated distance of 10 kpc. While such transients usually make a transition to the hard state at L/L{sub Edd} = 0.3%-3%, where L{sub Edd} is the Eddington luminosity, the 4U 1630-47 spectrum remained soft at L/L{sub Edd} = 0.008 M{sub 10}{sup −1}% (as measured in the 2-10 keV band), where M{sub 10} is the mass of the black hole in units of 10 M{sub ☉}. An estimate of the luminosity in the broader 0.5-200 keV bandpass gives L/L{sub Edd} = 0.03 M{sub 10}{sup −1}%, which is still an order of magnitude lower than typical. We also measured an exponential decay of the X-ray flux in the hard state with an e-folding time of 3.39 ± 0.06 days, which is much less than previous measurements of 12-15 days during decays by 4U 1630-47 in the soft state. With the ∼100 ks Suzaku observation, we do not see evidence for a reflection component, and the 90% confidence limits on the equivalent width of a narrow iron Kα emission line are <40 eV for a narrow line and <100 eV for a line of any width, which is consistent with a change of geometry (either a truncated accretion disk or a change in the location of the hard X-ray source) in the hard state. Finally, we report a 0.5-8 keV luminosity upper limit of <2 × 10{sup 32} erg s{sup –1} in quiescence, which is the lowest value measured for 4U 1630-47 to date.

  11. The use of Lyapunov differential inequalities for estimating the transients of mechanical systems

    Science.gov (United States)

    Alyshev, A. S.; Dudarenko, N. A.; Melnikov, V. G.; Melnikov, G. I.

    2018-05-01

    In this paper we consider an autonomous mechanical system in a finite neighborhood of the zero of the phase space of states. The system is given as a matrix differential equation in the Cauchy form with the right-hand side of the polynomial structure. We propose a method for constructing a sequence of linear inhomogeneous differential inequalities for Lyapunov functions. As a result, we obtain estimates of transient processes in the form of functional inequalities.

  12. Transient phenomena in electrical power systems

    CERN Document Server

    Venikov, V A; Higinbotham, W

    1964-01-01

    Electronics and Instrumentation, Volume 24: Transient Phenomena in Electrical Power Systems presents the methods for calculating the stability and the transient behavior of systems with forced excitation control. This book provides information pertinent to the analysis of transient phenomena in electro-mechanical systems.Organized into five chapters, this volume begins with an overview of the principal requirements in an excitation system. This text then explains the electromagnetic and electro-mechanical phenomena, taking into account the mutual action between the components of the system. Ot

  13. Radio outburst from a massive (proto)star. When accretion turns into ejection

    Science.gov (United States)

    Cesaroni, R.; Moscadelli, L.; Neri, R.; Sanna, A.; Caratti o Garatti, A.; Eisloffel, J.; Stecklum, B.; Ray, T.; Walmsley, C. M.

    2018-05-01

    Context. Recent observations of the massive young stellar object S255 NIRS 3 have revealed a large increase in both methanol maser flux density and IR emission, which have been interpreted as the result of an accretion outburst, possibly due to instabilities in a circumstellar disk. This indicates that this type of accretion event could be common in young/forming early-type stars and in their lower mass siblings, and supports the idea that accretion onto the star may occur in a non-continuous way. Aims: As accretion and ejection are believed to be tightly associated phenomena, we wanted to confirm the accretion interpretation of the outburst in S255 NIRS 3 by detecting the corresponding burst of the associated thermal jet. Methods: We monitored the radio continuum emission from S255 NIRS 3 at four bands using the Karl G. Jansky Very Large Array. The millimetre continuum emission was also observed with both the Northern Extended Millimeter Array of IRAM and the Atacama Large Millimeter/Submillimeter Array. Results: We have detected an exponential increase in the radio flux density from 6 to 45 GHz starting right after July 10, 2016, namely 13 months after the estimated onset of the IR outburst. This is the first ever detection of a radio burst associated with an IR accretion outburst from a young stellar object. The flux density at all observed centimetre bands can be reproduced with a simple expanding jet model. At millimetre wavelengths we infer a marginal flux increase with respect to the literature values and we show this is due to free-free emission from the radio jet. Conclusions: Our model fits indicate a significant increase in the jet opening angle and ionized mass loss rate with time. For the first time, we can estimate the ionization fraction in the jet and conclude that this must be low (memory of MalcolmWalmsley, who passed away before the present study could be completed. Without his insights and enlightened advice this work would have been impossible

  14. The Accretion Powered Spin-up of GRO 1750–27

    DEFF Research Database (Denmark)

    Kretschmar, P.; Shaw, S.; Hill, A. B.

    2009-01-01

    The transient Be X-ray pulsar GRO J1750-27 was originally detected in 1995 by CGRO/BATSE during a giant outburst. After a long period of quiescence the source was detected in another outburst early 2008. Following this outburst with hard X-ray data from INTEGRAL and Swift, the orbital parameters...

  15. A CHALLENGING VIEW OF THE 2015 SUMMER V404 CYG OUTBURST AT HIGH ENERGY WITH INTEGRAL /SPI: THE FINALE

    International Nuclear Information System (INIS)

    Jourdain, Elisabeth; Roques, Jean-Pierre; Rodi, James

    2017-01-01

    During its strong outburst of 2015 June/July, the X-ray transient V404 Cygni (=GS2023+338) was observed up to a level of 50 Crab in the hard X-ray domain. We focus here on a particularly intense episode preceeding a definitive decline of the source activity. We benefit from large signal-to-noise ratios to investigate the source spectral variability, on a timescale of five minutes. A hardness–intensity study of three broad bands reveals clearly different behaviors at low and high energy (below and above ∼100 keV). In particular, on two occasions, the source intensity varies by a factor of 3–4 in amplitude while keeping the same spectral shape. On the other hand, at the end of the major flare, the emission presents a clear anticorrelation between flux and hardness. These behaviors strongly suggest the presence of two spectral components related to emission processes varying in a largely independent way. The first component ( E < 100–150 keV) is classically identified with a Comptonizing thermal electron population, and requires either an unusual seed photon population or a specific geometry with strong absorbing/reflecting material. The second component is modeled by a cutoff power-law, which could correspond to a second hotter Comptonizing population or another mechanism (synchrotron, non-thermal Comptonization...). In the framework of such a model, hardness–intensity and flux–flux diagrams clearly demonstrate that the source evolution follows a well-organized underlying scheme. They reveal unique information about the hard X-ray emission processes and connections between them.

  16. Evidence for quiescent synchrotron emission in the black hole X-ray transient Swift J1357.2–0933

    Directory of Open Access Journals (Sweden)

    Shahbaz T.

    2013-12-01

    Full Text Available We present high time-resolution optical and infrared observations of the edge-on black hole X-ray transient Swift J1357.2-0933. Our data taken in 2012 shows the system to be at its pre-outburst magnitude and so the system is in quiescence. In contrast to other X-ray transients, the quiescent light curves of Swift J1357.2-0933 do not show the secondary star’s ellipsoidal modulation. The optical and infrared light curves is dominated by variability with an optical fractional rms of about 20 per cent, much larger than what is observed in other systems. The quiescent ultraviolet to mid-IR spectral energy distribution in quiescence is dominated by a nonthermal component with a power–law index of −1.4, (the broad-band rms SED has a similar index which arises from optically thin synchrotron emission from a jet; the lack of a peak in the spectral energy distribution rules out advection-dominated models (based on [19].

  17. INTEGRAL observations of SAX J1808.4-3658 currently in outburst

    DEFF Research Database (Denmark)

    Del Santo, M.; Bozzo, E.; Kuulkers, E.

    2015-01-01

    The latest INTEGRAL Galactic Bulge monitoring (ATel #438) was performed during revolution 1529 on 2015 April 12 starting at 18:15 UT (57124.761 MJD) for a total of 12462 seconds. We report on the IBIS/ISGRI detection of the new outburst from the millisecond X-ray pulsar SAX J1808.4-3658 (ATels...

  18. Outburst from the SFXT IGR J17544-2619 detected by INTEGRAL

    DEFF Research Database (Denmark)

    Paizis, A.; Kuulkers, E.; Chenevez, J.

    2015-01-01

    During public INTEGRAL Galactic bulge monitoring observations (ATel #438) performed on 2015 February 20-21 at UT 23:04-02:45, we detected the SFXT IGR J17544-2619 (see ATel #7137 for the recent Swift detection of the source outburst). The source was detected using IBIS/ISGRI in the 18-40 keV rang...

  19. INTEGRAL observations of the BHC IGR J17091-3624 in outburst

    DEFF Research Database (Denmark)

    Capitanio, F.; Tramacere, A.; Del Santo, M.

    2011-01-01

    During the monitoring of the RX J1712.7-3946 region (PI. R. Terrier), INTEGRAL observed the currently ongoing outburst of the BHC IGRJ17091-3624 (Atels #3144, #3148, #3150). These observations were performed from 2011 Feb. 07 at 11:53 to 2011 Feb. 08 at 18:56 (UTC). The source was detected by IBI...

  20. Sedimentary and rock magnetic signatures and event scenarios of deglacial outburst floods from the Laurentian Channel Ice Stream

    Science.gov (United States)

    Leng, Wei; von Dobeneck, Tilo; Bergmann, Fenna; Just, Janna; Mulitza, Stefan; Chiessi, Cristiano M.; St-Onge, Guillaume; Piper, David J. W.

    2018-04-01

    Eastern Canadian margin sediments bear testimony to several catastrophic deglacial meltwater discharges from the retreating Laurentide Ice Sheet. The reddish-brown plumite layers deposited on the levees of the Laurentian Fan valleys have been recognized as indications of multiple outburst floods between Heinrich events 2 and 1. Five event layers have been consistently recorded in three new gravity cores retrieved on the SW Grand Banks slope and comply with the previously published Laurentian Fan core MD95-2029. The apparently huge extent of these outburst plumes around the Laurentian Fan as well as their causes and consequences are investigated in this study using physical properties, rock magnetic and grain-size analyses, together with seismoacoustic profiling. We provide the first detailed 14C ages of the outburst event sequence and discuss their recurrence intervals in the context of regional ice retreat. Compared to the hemipelagic interlayers, event layers have overall uniform and systematic changes of rock-magnetic properties. Hematite contents increase over time and proximally while magnetite grain sizes fine upwards and spatially away from the fan. Based on the sediment composition and load, we argue that these plumites were formed by recurrent erosion of glacial mud deposits in the Laurentian Channel by meltwater outbursts. Three alternative glaciological scenarios are evaluated: in each case, the provenance of the transported sediment is not an indicator of the precise source of the meltwater.

  1. Regional-scale GIS-models for assessment of hazards from glacier lake outbursts: evaluation and application in the Swiss Alps

    Directory of Open Access Journals (Sweden)

    C. Huggel

    2003-01-01

    Full Text Available Debris flows triggered by glacier lake outbursts have repeatedly caused disasters in various high-mountain regions of the world. Accelerated change of glacial and periglacial environments due to atmospheric warming and increased anthropogenic development in most of these areas raise the need for an adequate hazard assessment and corresponding modelling. The purpose of this paper is to pro-vide a modelling approach which takes into account the current evolution of the glacial environment and satisfies a robust first-order assessment of hazards from glacier-lake outbursts. Two topography-based GIS-models simulating debris flows related to outbursts from glacier lakes are presented and applied for two lake outburst events in the southern Swiss Alps. The models are based on information about glacier lakes derived from remote sensing data, and on digital elevation models (DEM. Hydrological flow routing is used to simulate the debris flow resulting from the lake outburst. Thereby, a multiple- and a single-flow-direction approach are applied. Debris-flow propagation is given in probability-related values indicating the hazard potential of a certain location. The debris flow runout distance is calculated on the basis of empirical data on average slope trajectory. The results show that the multiple-flow-direction approach generally yields a more detailed propagation. The single-flow-direction approach, however, is more robust against DEM artifacts and, hence, more suited for process automation. The model is tested with three differently generated DEMs (including aero-photogrammetry- and satellite image-derived. Potential application of the respective DEMs is discussed with a special focus on satellite-derived DEMs for use in remote high-mountain areas.

  2. Application of the third theory of quantification in coal and gas outburst forecast

    Energy Technology Data Exchange (ETDEWEB)

    Wu, C.; Qin, Y.; Zhang, X. [China University of Mining and Technology, Xuzhou (China). School of Resource and Geoscience Engineering

    2004-12-01

    The essential principles of the third theory of quantification are discussed. The concept and calculated method of reaction degree are put forward which extend the applying range and scientificalness of the primary reaction. Taking the Zhongmacun mine as example, on the base of analyzing the rules of gas geology synthetically and traversing the geological factors affecting coal and gas outburst. The paper adopts the method of combining statistical units with the third theory of quantification, screens out 8 sensitive geological factors from 11 geological indexes and carries through the work of gas geology regionalism to the exploited area of Zhongmacun according to the research result. The practice shows that it is feasible to apply the third theory of quantification to gas geology, which offers a new thought to screen the sensitive geological factors of gas outburst forecast. 3 refs., 3 figs., 3 tabs.

  3. Sound wave generation by a spherically symmetric outburst and AGN feedback in galaxy clusters II: impact of thermal conduction.

    Science.gov (United States)

    Tang, Xiaping; Churazov, Eugene

    2018-04-01

    We analyze the impact of thermal conduction on the appearance of a shock-heated gas shell which is produced when a spherically symmetric outburst of a supermassive black hole inflates bubbles of relativistic plasma at the center of a galaxy cluster. The presence of the hot and low-density shell can be used as an ancillary indicator for a high rate of energy release during the outburst, which is required to drive strong shocks into the gas. Here we show that conduction can effectively erase such shell, unless the diffusion of electrons is heavily suppressed. We conclude that a more robust proxy to the energy release rate is the ratio between the shock radius and bubble radius. We also revisited the issue of sound waves dissipation induced by thermal conduction in a scenario, where characteristic wavelength of the sound wave is set by the total energy of the outburst. For a fiducial short outburst model, the dissipation length does not exceed the cooling radius in a typical cluster, provided that the conduction is suppressed by a factor not larger than ˜100. For quasi-continuous energy injection neither the shock-heated shell nor the outgoing sound wave are important and the role of conduction is subdominant.

  4. The mechanism of transient myopia induced by sulfonamide therapy.

    Science.gov (United States)

    Bovino, J A; Marcus, D F

    1982-07-01

    We performed acute and convalescent A-scan echographic ocular measurements documenting the anterior chamber depth, lens thickness, and axial length of a patient with acute transient sulfamethoxazole-induced myopia. Shallowing of the anterior chamber, independent of changes in the thickness of the lens, was the only anatomic variation found that could explain the myopia. Swelling of the ciliary body, with forward movement of the lens-iris diaphragm, could produce this transient anatomic change.

  5. ASAS-SN Discovery of a Bright Be Star Undergoing a Possible Outburst

    Science.gov (United States)

    Jayasinghe, T.; Stanek, K. Z.; Kochanek, C. S.; Thorstensen, J.; Rupert, J.; Prieto, J. L.; Shields, J. V.; Thompson, T. A.; Holoien, T. W.-S.; Shappee, B. J.; Dong, Subo

    2017-09-01

    As part of an ongoing effort by ASAS-SN project (Shappee et al. 2014; Kochanek et al. 2017) to characterize and catalog all bright variable stars (e.g., Jayasinghe et al. 2017, ATel #10634, #10677), we report the discovery of a bright Be star undergoing a possible outburst.

  6. DETECTION OF REMNANT DUST CLOUD ASSOCIATED WITH THE 2007 OUTBURST OF 17P/HOLMES

    Energy Technology Data Exchange (ETDEWEB)

    Ishiguro, Masateru; Kim, Yoonyoung; Kwon, Yuna G. [Department of Physics and Astronomy, Seoul National University, Gwanak, Seoul 151-742 (Korea, Republic of); Sarugaku, Yuki [Kiso Observatory, Institute of Astronomy, Graduate School of Science, The University of Tokyo, Mitake, Kiso-machi, Kiso, Nagano 397-0101 (Japan); Kuroda, Daisuke; Maehara, Hiroyuki [Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, Asakuchi, Okayama 719-0232 (Japan); Hanayama, Hidekazu [Ishigakijima Astronomical Observatory, National Astronomical Observatory of Japan, 1024-1 Arakawa, Ishigaki, Okinawa 907-0024 (Japan); Takahashi, Jun [Nishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyogo, Sayo, Hyogo 679-5313 (Japan); Terai, Tsuyoshi [Subaru Telescope, National Astronomical Observatory of Japan, Hilo, HI 96720 (United States); Usui, Fumihiko [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Vaubaillon, Jeremie J. [Observatoire de Paris, I.M.C.C.E., Denfert Rochereau, Bat. A., F-75014 Paris (France); Morokuma, Tomoki; Kobayashi, Naoto [Institute of Astronomy, Graduate School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Watanabe, Jun-ichi [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan)

    2016-01-20

    This article reports a new optical observation of 17P/Holmes one orbital period after the historical outburst event in 2007. We detected not only a common dust tail near the nucleus but also a long narrow structure that extended along the position angle 274.°6 ± 0.°1 beyond the field of view (FOV) of the Kiso Wide Field Camera, i.e., >0.°2 eastward and >2.°0 westward from the nuclear position. The width of the structure decreased westward with increasing distance from the nucleus. We obtained the total cross section of the long extended structure in the FOV, C{sub FOV} = (2.3 ± 0.5) × 10{sup 10} m{sup 2}. From the position angle, morphology, and mass, we concluded that the long narrow structure consists of materials ejected during the 2007 outburst. On the basis of the dynamical behavior of dust grains in the solar radiation field, we estimated that the long narrow structure would be composed of 1 mm–1 cm grains having an ejection velocity of >50 m s{sup −1}. The velocity was more than one order of magnitude faster than that of millimeter–centimeter grains from typical comets around a heliocentric distance r{sub h} of 2.5 AU. We considered that sudden sublimation of a large amount of water-ice (≈10{sup 30} mol s{sup −1}) would be responsible for the high ejection velocity. We finally estimated a total mass of M{sub TOT} = (4–8) × 10{sup 11} kg and a total kinetic energy of E{sub TOT} = (1–6) × 10{sup 15} J for the 2007 outburst ejecta, which are consistent with those of previous studies that were conducted soon after the outburst.

  7. INTEGRAL observation of SWIFT J1756.9-2508 in outburst

    Science.gov (United States)

    Mazzola, S.; Bozzo, E.; Kuulkers, E.; Ferrigno, C.; Savchenko, V.; Ducci, L.

    2018-04-01

    Following the discovery of a new outburst from the accreting millisecond X-ray pulsar SWIFT J1756.9-2508 (ATel #11497, #11502, #11505), a dedicated target of opportunity observation with INTEGRAL was carried out from 2018 April 1 at 08:30 to 23:15 (UTC; total exposure time 85 ks). The source was detected in the 20-40 keV IBIS/ISGRI mosaic at a significance level of 20 sigma.

  8. Monitoring of Bashkara glacial lakes (the Central Caucasus) and modelling of their potential outburst.

    Science.gov (United States)

    Krylenko, I.; Norin, S.; Petrakov, D.; Tutubalina, O.; Chernomorets, S.

    2009-04-01

    In recent decades due to glacier retreat the glacial lakes in the Central Caucasus, as well as in other high-mountainous areas of the world, have expanded intensively. As result the risk of lake outbursts and destructive floods is raising. In this paper we present one of the most potentially hazardous lakes of this region - a group of glacial lakes near the Bashkara glacier in the upper Adylsu river valley, to the southeast of Mt. Elbrus. Total area of these lakes is about 100,000m2, and a total volume exceeds 1,000,000 m3. The biggest of them - the Bashkara lake has formed in late 1930s - early 1940s and the small Lapa lake has appeared in the end of 1980s. The Bashkara lake outburst occurred twice in the end of 1950s and produced devastating debris flows of ca. 2 million m3. We have monitored these lakes since 1999. Our work includes detailed field research: constant measurements of water level during warm period, annually repeated bathymetric surveys, geodetic surveys, observations on dam condition and some special measurements (i.e. water temperature distribution, current velocity). Also we use aerial and satellite images to obtain data about dynamic of areas for the lakes. From 2001 to 2006 years volume of the Lapa lake has increased 5 times (from 30,000 m3 to 140,000 m3), the Bashkara lake in this period was quasi-stable. In 2006-2008 volume of the Lapa lake has decreased due to sedimentation, however, rapid growth of water level in Bashkara lake (more than 20 sm. per day) has suddenly begun. As a result, volume of the Bashkara lake exceeded 1,000000 m3 in July 2008 whereas in 2001 -2007 year it was about 800,000 m3. Previous maximum of water level was exceeded on 3,5 m, moraine dam with ice core was overtopped and overflow has started. Thus, Bashkara glacier lakes are unstable and risk of outburst is increasing. To assess parameters and zones of potential outburst flood in the Adylsu River valley we have carried out hydrodynamic simulation. Two computer

  9. Discovery of a Transient Magnetar: XTE J1810-197

    Science.gov (United States)

    Ibrahim, Alaa I.; Markwardt, Craig B.; Swank, Jean H.; Ransom, Scott; Roberts, Mallory; Kaspi, Victoria; Woods, Peter M.; Safi-Harb, Samar; Balman, Solen; Parke, William C.

    2004-01-01

    We report the discovery of a new X-ray pulsar, XTE J1810-197, that was serendipitously discovered on 2003 July 15 by the Rossi X-Ray Timing Explorer (RXTE) while observing the soft gamma repeater SGR 1806-20. The pulsar has a 5.54 s spin period, a soft X-ray spectrum (with a photon index of approx. = 4). and is detectable in earlier RXTE observations back to 2003 January but not before. These show that a transient outburst began between 2002 November 17 and 2003 January 23 and that the source's persistent X-ray flux has been declining since then. The pulsar exhibits a high spin-down rate P approx.= l0(exp -11) s/s with no evidence of Doppler shifts due to a binary companion. The rapid spin-down rate and slow spin period imply a supercritical characteristic magnetic field B approx. = 3 x l0(exp 14) G and a young age tau less than or = 7600 yr. Follow-up Chandra observations provided an accurate position of the source. Within its error radius, the 1.5 m Russian-Turkish Optical Telescope found a limiting magnitude R(sub c) = 21.5. All such properties are strikingly similar to those of anomalous X-ray pulsars ad soft gamma repeaters, providing strong evidence that the source is a new magnetar. However, archival ASCA and ROSAT observations found the source nearly 2 orders of magnitude fainter. This transient behavior and the observed long-term flux variability of the source in absence of an observed SGR-like burst activity make it the first confirmed transient magnetar and suggest that other neutron stars that share the properties of XTE 51810- 197 during its inactive phase may be unidentified transient magnetars awaiting detection via a similar activity. This implies a larger population of magnetars than previously surmised and a possible evolutionary connection between magnetars and other neutron star families. Subject headings: pulsars: general -pulsars: individual (XTE 51810- 197) - stars: magnetic fields -

  10. The joy of transient chaos

    Energy Technology Data Exchange (ETDEWEB)

    Tél, Tamás [Institute for Theoretical Physics, Eötvös University, and MTA-ELTE Theoretical Physics Research Group, Pázmány P. s. 1/A, Budapest H-1117 (Hungary)

    2015-09-15

    We intend to show that transient chaos is a very appealing, but still not widely appreciated, subfield of nonlinear dynamics. Besides flashing its basic properties and giving a brief overview of the many applications, a few recent transient-chaos-related subjects are introduced in some detail. These include the dynamics of decision making, dispersion, and sedimentation of volcanic ash, doubly transient chaos of undriven autonomous mechanical systems, and a dynamical systems approach to energy absorption or explosion.

  11. The joy of transient chaos.

    Science.gov (United States)

    Tél, Tamás

    2015-09-01

    We intend to show that transient chaos is a very appealing, but still not widely appreciated, subfield of nonlinear dynamics. Besides flashing its basic properties and giving a brief overview of the many applications, a few recent transient-chaos-related subjects are introduced in some detail. These include the dynamics of decision making, dispersion, and sedimentation of volcanic ash, doubly transient chaos of undriven autonomous mechanical systems, and a dynamical systems approach to energy absorption or explosion.

  12. NEAR-IR STUDIES OF RECURRENT NOVA V745 SCORPII DURING ITS 2014 OUTBURST

    International Nuclear Information System (INIS)

    Banerjee, D. P. K.; Joshi, Vishal; Venkataraman, V.; Ashok, N. M.; Raj, A.; Marion, G. H.; Hsiao, E. Y.

    2014-01-01

    The recurrent nova V745 Scorpii underwent its third known outburst on 2014 February 6. Infrared monitoring of the eruption on an almost daily basis, starting from 1.3 days after discovery, shows the emergence of a powerful blast wave generated by the high velocity nova ejecta exceeding 4000 km s –1 plowing into its surrounding environment. The temperature of the shocked gas is raised to a high value exceeding 10 8 K immediately after outburst commencement. The energetics of the outburst clearly surpass those of similar symbiotic systems like RS Oph and V407 Cyg which have giant secondaries. The shock does not show a free-expansion stage but rather shows a decelerative Sedov-Taylor phase from the beginning. Such strong shock fronts are known to be sites for γ-ray generation. V745 Sco is the latest nova, apart from five other known novae, to show γ-ray emission. It may be an important testbed to resolve the crucial question of whether or not all novae are generically γ-ray emitters by virtue of having a circumbinary reservoir of material that is shocked by the ejecta rather than γ-ray generation being restricted to only symbiotic systems with a shocked red giant (RG) wind. The lack of a free-expansion stage favors V745 Sco to have a density enhancement around the white dwarf (WD), above that contributed by a RG wind. Our analysis also suggests that the WD in V745 Sco is very massive and a potential progenitor for a future SN Ia explosion

  13. Outbursts In Symbiotic Binaries (FUSE 2000)

    Science.gov (United States)

    Kenyon, Scott J.; Sonneborn, George (Technical Monitor)

    2002-01-01

    During the past year, we made good progress on analysis of FUSE observations of the symbiotic binary Z And. For background, Z And is a binary system composed of a red giant and a hot component of unknown status. The orbital period is roughly 750 days. The hot component undergoes large-scale eruptions every 10-20 yr. An outburst began several years ago, triggering this FUSE opportunity. First, we obtained an excellent set of ground-based optical data in support, of the FUSE observations. We used FAST, a high throughput low resolution spectrograph on the 1.5-m telescope at Mt. Hopkins, Arizona. A 300 g/ mm grating blazed at 4750 A, a 3 in. slit, and a thinned Loral 512 x 2688 CCD gave us spectra covering 3800-7500 A at a resolution of 6 A. The wavelength solution for each spectrum has a probable error of +/- 0.5 A or better. Most of the resulting spectra have moderate signal-to-noise, S/.N approx. greater than 30 per pixel. The time coverage for these spectra is excellent. Typically, we acquired spectra every 1-2 nights during dark runs at Mt. Hopkins. These data cover most of the rise and all of the decline of the recent outburst. The spectra show a wealth of emission lines, including H I, He I, He II, [Fe V11], and the Raman scattering bands at 6830 A and 7088 A. The Raman bands and other high ionization features vary considerably throughout the outburst. These features will enable us to correlate variations in the FUSE spectra with variations in the optical spectra. Second, we began an analysis of FUSE spectra of Z And. We have carefully examined the spectra, identifying real features and defects. We have identified and measured fluxes for all strong emission lines, including the O VI doublet at 1032 A and 1038 A. These and several other strong emission lines display pronounced P Cygni absorption components indicative of outgrowing gas. We will attempt to correlate these velocities with similar profiles observed on optical spectra. The line velocities - together

  14. Transient-Switch-Signal Suppressor

    Science.gov (United States)

    Bozeman, Richard J., Jr.

    1995-01-01

    Circuit delays transmission of switch-opening or switch-closing signal until after preset suppression time. Used to prevent transmission of undesired momentary switch signal. Basic mode of operation simple. Beginning of switch signal initiates timing sequence. If switch signal persists after preset suppression time, circuit transmits switch signal to external circuitry. If switch signal no longer present after suppression time, switch signal deemed transient, and circuit does not pass signal on to external circuitry, as though no transient switch signal. Suppression time preset at value large enough to allow for damping of underlying pressure wave or other mechanical transient.

  15. Outburst in Mira AB?

    Science.gov (United States)

    Karovska, Margarita

    2003-09-01

    The nearby system Mira AB composed of an aging AGB star (Mira A) and a WD companion (Mira B) offers a unique laboratory for studying wind accretion processes, a poorly understood phenomenon in many sources. Recent Chandra ACIS-S Obs.(70ks on 12/6/03; PI.M.Karovska) resolved for the first time the components (~0.6") in X-rays, and detected a new bright soft source (A. This is the first detection of X-rays from an AGB star. This source was not detected by ROSAT in 1993 or recently by XMM 8/03 (AAS/03,J.Kastner), and could be a transient phenomenon. Model fitting shows that the soft X-ray emission is likely several emission lines, rather then a continuum; with ACIS spectral resolution we cannot resolve or identify these lines. We propose a 40ks LETG+HRC-S obs. to identify the lines and determine the emission mechanism.

  16. CW 316 mechanical properties during thermal transients

    International Nuclear Information System (INIS)

    Cauvin, R.; Boutard, J.L.; Allegraud, G.

    1984-06-01

    During in pile incidents, the cladding can experience higher temperatures than the nominal one; it is necessary to know the mechanical properties of the cladding material during such thermal transients to predict the time and location of rupture. Two types of tests have been developed: first tensile (constant strain rate) tests after a heating at a constant rate and secondly constant load tests where heating is performed until rupture occurs. The tensile tests clearly show the role of the heating rate: the higher is the heating rate, the lower is the cold work recovery. Constant load tests were conducted with either uniaxial or biaxial (burst tests) loading. The same stress/failure temperature relation is found in both types of loading using the Von Mises equivalent stress. To predict failure, the Larson Miller parameter is not adequate, as well as all parameters based on a time/temperature equivalence. The yield stress measured in the two types of tests are very different probably due to a strain rate effect. Indeed the tensile tests are dynamic ones to avoid thermal recovery during the test duration, while the strain rate measured in constant load tests ranges only from 10 -5 s -1 to 10 -3 s -1 , being an increasing function of heating rate (ranging from 1 0 c/s to 100 0 c/s)

  17. Optical spectroscopy of V404 Cyg during its latest outburst

    Science.gov (United States)

    Somogyi, Peter

    2016-01-01

    Low resolution spectra were obtained during the current outburst (announced in ATel #8453) of the microquasar V404 Cyg. Ten 600 sec exposures were obtained on 2015 Dec. 31 (JD 2457388.202 - 0.27) with a 250 mm Newtonian reflector using an LHires III spectrograph with 150 line/mm grating (R ~ 500) spanning 4500-7500A with the combined S/N ~ 10 (continuum at 6000A; calibration used the standard HD192640).

  18. Lakes near the glacier Maliy Azau on the Elbrus (Central Caucasus: dynamics and outbursts

    Directory of Open Access Journals (Sweden)

    M. D. Dokukin

    2016-01-01

    Full Text Available The lake dynamics and the current state of them were analyzed on the basis of interpretation of aerial and satellite images of different years together with results of field surveys. Areas of six lakes existing in different years near the Maliy Azau Glacier had been determined. On August 22, 2011, the maximum area of one of the lakes was equal to 25.5 thousand m2. The first outburst was caused by the landslide deformations of the moraine massif forming a part of the lake basin, while the second one was a result of degradation of the lake ice dam and the water overflow on top of it. The present‑day lake dams (terminal‑moraine ramparts and medial moraine ridges are the result of the Maliy Azau Glacier advance in 1990s. The revealed feature of the lake dynamics on the mountain Elbrus was a drop of the water level and corresponding decrease of the lake areas in winter that was related to existence of the groundwater runoff into fractured volcanic rocks. At present, moraine dams of lakes and areas of the surface water runoff from the lakes are in stable condition due to which there is no threat of a lake outburst. However, the potential threat of outburst still remains because of high seismicity and possible volcanic activity in this region.

  19. Faulkes Telescope monitoring of the current outburst of IGR J00291+5934

    NARCIS (Netherlands)

    Russell, D.M.; Lewis, F.; Linares, M.; Roche, P.; Maitra, D.

    2008-01-01

    As part of an optical monitoring project of low-mass X-ray binaries (Lewis et al. 2008, http://adsabs.harvard.edu/abs/2008AIPC.1010..204L), we report on recent observations just prior to, and during the current outburst of the millisecond X-ray pulsar IGR J00291+5934 (ATel #1660, #1664, #1665). The

  20. The extreme carbon dioxide outburst at the Menzengraben potash mine 7 July 1953

    DEFF Research Database (Denmark)

    Hedlund, Frank Huess

    2012-01-01

    Carbon dioxide is an asphyxiant and an irritant gas. An extreme outburst of carbon dioxide took place 7 July 1953 in a potash mine in the former East Germany. During 25 min, a large amount of CO2 was blown out of the mine shaft with great force. It was wind still and concentrated CO2 accumulated....... It is concluded that 1100–3900 tonnes of CO2 were blown out of the mine shaft, possibly with intensities around 4 tonnes/s. It is also concluded that the large majority of the gas escaped as a near-vertical high-velocity jet with only little loss of momentum due to impingement. The release was modelled using...... histories to date include sudden releases of CO2 of up to 50 tonnes only, far too small to provide a suitable empirical perspective on predicted hazard distances for CCS projects. The 1953 outburst contributes to filling this gap....

  1. Extremely organic-rich coma of comet C/2010 G2 (Hill) during its outburst in 2012

    International Nuclear Information System (INIS)

    Kawakita, Hideyo; Kobayashi, Hitomi; Russo, Neil Dello; Vervack, Ron Jr.; Weaver, Harold A.; DiSanti, Mike A.; Opitom, Cyrielle; Jehin, Emmanuel; Manfroid, Jean; Gillon, Michael; Cochran, Anita L.; Harris, Walter M.; Bockelée-Morvan, Dominique; Biver, Nicolas; Crovisier, Jacques; McKay, Adam J.

    2014-01-01

    We performed high-dispersion near-infrared spectroscopic observations of comet C/2010 G2 (Hill) at 2.5 AU from the Sun using NIRSPEC (R ≈ 25,000) at the Keck II Telescope on UT 2012 January 9 and 10, about a week after an outburst had occurred. Over the two nights of our observations, prominent emission lines of CH 4 and C 2 H 6 , along with weaker emission lines of H 2 O, HCN, CH 3 OH, and CO were detected. The gas production rate of CO was comparable to that of H 2 O during the outburst. The mixing ratios of CO, HCN, CH 4 , C 2 H 6 , and CH 3 OH with respect to H 2 O were higher than those for normal comets by a factor of five or more. The enrichment of CO and CH 4 in comet Hill suggests that the sublimation of these hypervolatiles sustained the outburst of the comet. Some fraction of water in the inner coma might exist as icy grains that were likely ejected from nucleus by the sublimation of hypervolatiles. Mixing ratios of volatiles in comet Hill are indicative of the interstellar heritage without significant alteration in the solar nebula.

  2. Extremely organic-rich coma of comet C/2010 G2 (Hill) during its outburst in 2012

    Energy Technology Data Exchange (ETDEWEB)

    Kawakita, Hideyo; Kobayashi, Hitomi [Koyama Astronomical Observatory, Kyoto Sangyo University, Motoyama, Kamitamo, Kita, Kyoto 603-8555 (Japan); Russo, Neil Dello; Vervack, Ron Jr.; Weaver, Harold A. [The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723-6099 (United States); DiSanti, Mike A. [Goddard Center for Astrobiology, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Opitom, Cyrielle; Jehin, Emmanuel; Manfroid, Jean; Gillon, Michael [F. R. S.-FNRS, Institut d' Astrophysique et de Géophysique, Université de Liège, Allée du 6 août 17, B-4000 Liège (Belgium); Cochran, Anita L. [McDonald Observatory, 1 University Station C1402, Austin, TX 78712-0259 (United States); Harris, Walter M. [Department of Applied Sciences, University of California, One Shields Avenue, Davis, CA 95616 (United States); Bockelée-Morvan, Dominique; Biver, Nicolas; Crovisier, Jacques [LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, 5 Place Jules Janssen, F-92195 Meudon (France); McKay, Adam J., E-mail: kawakthd@cc.kyoto-su.ac.jp [New Mexico State University, Las Cruces, NM 88001 (United States)

    2014-06-20

    We performed high-dispersion near-infrared spectroscopic observations of comet C/2010 G2 (Hill) at 2.5 AU from the Sun using NIRSPEC (R ≈ 25,000) at the Keck II Telescope on UT 2012 January 9 and 10, about a week after an outburst had occurred. Over the two nights of our observations, prominent emission lines of CH{sub 4} and C{sub 2}H{sub 6}, along with weaker emission lines of H{sub 2}O, HCN, CH{sub 3}OH, and CO were detected. The gas production rate of CO was comparable to that of H{sub 2}O during the outburst. The mixing ratios of CO, HCN, CH{sub 4}, C{sub 2}H{sub 6}, and CH{sub 3}OH with respect to H{sub 2}O were higher than those for normal comets by a factor of five or more. The enrichment of CO and CH{sub 4} in comet Hill suggests that the sublimation of these hypervolatiles sustained the outburst of the comet. Some fraction of water in the inner coma might exist as icy grains that were likely ejected from nucleus by the sublimation of hypervolatiles. Mixing ratios of volatiles in comet Hill are indicative of the interstellar heritage without significant alteration in the solar nebula.

  3. Transient electromagnetic detecting technique for water hazard to the roof of fully mechanized sub-level caving face

    Energy Technology Data Exchange (ETDEWEB)

    Yu Jing-cun; Liu Zhi-xin; Tang Jin-yun; Wang Yang-zhou [China University of Mining & Technology, Xuzhou (China). School of Resources and Geoscience Science

    2007-07-01

    In coal mining, with the popularization of fully mechanized equipment, the roof control becomes more and more important. The development of water body in roofs may seriously affect the efficiency of the fully mechanized mining, quite possible to cause an accident in working face. Therefore, to make clear the position of a water body located in roofs so as to provide a basis for water drainage borehole layout is an urgent problem to be solved by geophysical exploration. Based on the transient electromagnetic theory and the technique used on ground surface and on the actual situation in underground coal mines, a square superimposed loop device (2 m in side length) which is non-contact and multi-turns was developed to detect the water bodies in coal seam roofs. Based on the 'smoke ring effect' theory and the physical simulation criterion, the mathematical model for calculating the apparent resistivity of full space transient electromagnetism is deduced. In addition, the water detection technology for the roof of fully mechanized sub-level caving face was researched and applied in several coal mines, which has been verified by boreholes and mining practice, indicating that this method is very effective in detecting the water source in the roof of fully mechanized sub-level caving face. 11 refs., 5 figs.

  4. Optical Precursors to Black Hole X-Ray Binary Outbursts: An Evolving Synchrotron Jet Spectrum in Swift J1357.2–0933

    Science.gov (United States)

    Russell, David M.; Qasim, Ahlam Al; Bernardini, Federico; Plotkin, Richard M.; Lewis, Fraser; Koljonen, Karri I. I.; Yang, Yi-Jung

    2018-01-01

    We present six years of optical monitoring of the black hole (BH) candidate X-ray binary Swift J1357.2–0933, during and since its discovery outburst in 2011. On these long timescales, the quiescent light curve is dominated by high amplitude, short-term (seconds–days) variability spanning ∼2 mag, with an increasing trend of the mean flux from 2012 to 2017 that is steeper than in any other X-ray binary found to date (0.17 mag yr‑1). We detected the initial optical rise of the 2017 outburst of Swift J1357.2–0933, and we report that the outburst began between 2017 April 1 and 6. Such a steep optical flux rise preceding an outburst is expected according to disk instability models, but the high amplitude variability in quiescence is not. Previous studies have shown that the quiescent spectral, polarimetric, and rapid variability properties of Swift J1357.2–0933 are consistent with synchrotron emission from a weak compact jet. We find that a variable optical/infrared spectrum is responsible for the brightening: a steep, red spectrum before and soon after the 2011 outburst evolves to a brighter, flatter spectrum since 2013. The evolving spectrum appears to be due to the jet spectral break shifting from the infrared in 2012 to the optical in 2013, then back to the infrared by 2016–2017 while the optical remains relatively bright. Swift J1357.2–0933 is a valuable source to study BH jet physics at very low accretion rates and is possibly the only quiescent source in which the optical jet properties can be regularly monitored.

  5. Understanding Epileptiform After-Discharges as Rhythmic Oscillatory Transients.

    Science.gov (United States)

    Baier, Gerold; Taylor, Peter N; Wang, Yujiang

    2017-01-01

    Electro-cortical activity in patients with epilepsy may show abnormal rhythmic transients in response to stimulation. Even when using the same stimulation parameters in the same patient, wide variability in the duration of transient response has been reported. These transients have long been considered important for the mapping of the excitability levels in the epileptic brain but their dynamic mechanism is still not well understood. To investigate the occurrence of abnormal transients dynamically, we use a thalamo-cortical neural population model of epileptic spike-wave activity and study the interaction between slow and fast subsystems. In a reduced version of the thalamo-cortical model, slow wave oscillations arise from a fold of cycles (FoC) bifurcation. This marks the onset of a region of bistability between a high amplitude oscillatory rhythm and the background state. In vicinity of the bistability in parameter space, the model has excitable dynamics, showing prolonged rhythmic transients in response to suprathreshold pulse stimulation. We analyse the state space geometry of the bistable and excitable states, and find that the rhythmic transient arises when the impending FoC bifurcation deforms the state space and creates an area of locally reduced attraction to the fixed point. This area essentially allows trajectories to dwell there before escaping to the stable steady state, thus creating rhythmic transients. In the full thalamo-cortical model, we find a similar FoC bifurcation structure. Based on the analysis, we propose an explanation of why stimulation induced epileptiform activity may vary between trials, and predict how the variability could be related to ongoing oscillatory background activity. We compare our dynamic mechanism with other mechanisms (such as a slow parameter change) to generate excitable transients, and we discuss the proposed excitability mechanism in the context of stimulation responses in the epileptic cortex.

  6. Strain-rate dependent plasticity in thermo-mechanical transient analysis

    International Nuclear Information System (INIS)

    Rashid, Y.R.; Sharabi, M.N.

    1980-01-01

    The thermo-mechanical transient behavior of fuel element cladding and other reactor components is generally governed by the strain-rate properties of the material. Relevant constitutive modeling requires extensive material data in the form of strain-rate response as function of true-stress, temperature, time and environmental conditions, which can then be fitted within a theoretical framework of an inelastic constitutive model. In this paper, we present a constitutive formulation that deals continuously with the entire strain-rate range and has the desirable advantage of utilizing existing material data. The derivation makes use of strain-rate sensitive stress-strain curve and strain-rate dependent yield surface. By postulating a strain-rate dependent on Mises yield function and a strain-rate dependent kinematic hardening rule, we are able to derive incremental stress-strain relations that describe the strain-rate behavior in the entire deformation range spanning high strain-rate plasticity and creep. The model is sufficiently general as to apply to any materials and loading histories for which data is available. (orig.)

  7. Discovery of the 198 s X-Ray Pulsar GRO J2058+42

    Science.gov (United States)

    Wilson, Colleen A.; Finger, Mark H.; Harmon, B. Alan; Chakrabarty, Deepto; Strohmayer, Tod

    1997-01-01

    GRO J2058+42, a transient 198 second x-ray pulsar, was discovered by the Burst and Transient Source Experiment (BATSE) on the Compton Gamma-Ray Observatory (CGRO), during a "giant" outburst in 1995 September-October. The total flux peaked at about 300 mCrab (20-50 keV) as measured by Earth occultation. The pulse period decreased from 198 s to 196 s during the 46-day outburst. The pulse shape evolved over the course of the outburst and exhibited energy dependent variations. BATSE observed five additional weak outbursts from GRO J2058+427 each with two week duration and peak pulsed flux of about 15 mcrab (20-50 keV), that were spaced by about 110 days. An observation of the 1996 November outburst by the Rossi X-ray Timing Explorer (RXTE) Proportional Counter Array (PCA) localized the source to within a 4' radius error circle (90% confidence) centered on R.A. = 20 h 59 m.0, Decl. = 41 deg 43 min (J2000). Additional shorter outbursts with peak pulsed fluxes of about 8 mCrab were detected by BATSE halfway between the first four 15 mCrab outbursts. The RXTE All-Sky Monitor detected 8 weak outbursts with approximately equal durations and intensities. GRO J2058+42 is most likely a Be/X-ray binary that appears to outburst at periastron and apastron. No optical counterpart has been identified to date and no x-ray source was present in the error circle in archival ROSAT observations.

  8. Discovery of the 198 Second X-Ray Pulsar GRO J2058+42

    Science.gov (United States)

    Wilson, Colleen A.; Finger, Mark H.; Harmon, B. Alan; Chakrabarty, Deepto; Strohmayer, Tod

    1998-01-01

    GRO J2058+42, a transient 198 s X-ray pulsar, was discovered by the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory (CGRO) during a "giant" outburst in 1995 September-October. The total flux peaked at about 300 mcrab (20-50 keV) as measured by Earth occultation. The pulse period decreased from 198 to 196 s during the 46 day outburst. The pulse shape evolved over the course of the outburst and exhibited energy-dependent variations. BATSE observed five additional weak outbursts from GRO J2058 + 42, each with a 2 week duration and a peak-pulsed flux of about 15 mcrab (20-50 keV), that were spaced by about 110 days. An observation of the 1996 November outburst by the Rossi X-Ray Timing Explorer (RXTE) proportional counter array (PCA) localized the source to within a 4 s radius error circle (90% confidence) centered on R.A. = 20h 59m.0, decl. = 41 deg 43 s (J2000). Additional shorter outbursts with peak-pulsed fluxes of about 8 mcrab were detected by BATSE halfway between the first four 15 mcrab outbursts. The RXTE All-Sky Monitor detected all eight weak outbursts with approximately equal durations and intensities. GRO J2058 + 42 is most likely a Be/X-ray binary that appears to outburst at periastron and apastron, No optical counterpart has been identified to date, and no X-ray source was present in the error circle in archival ROSAT observations.

  9. Fracture mechanical analysis of relevant transients in the pressure vessel of Atucha I reactor

    International Nuclear Information System (INIS)

    Saavedra, Fernando M.

    2001-01-01

    The evolution of the applied stress intensity factor K I for 10 relevant transients of the nuclear power station Atucha I obtained from thermohydraulic data is analyzed according to the methodology proposed in Section XI of ASME Boiler and Pressure Vessel Code. Vast knowledge was thus obtained about basic concepts of fracture mechanics and its application to remanent life of nuclear components. Basic knowledge which commands the performance of nuclear power stations was also obtained, especially that related to the Atucha I utility [es

  10. Outburst Properties of V1504 Cyg and V344 Lyr

    Directory of Open Access Journals (Sweden)

    J. K. Cannizzo

    2015-02-01

    Full Text Available I begin by reviewing dwarf novae and the disk instability theory, and then present an overview of three ideas for producing superoutbursts in the SU UMa stars − the thermal tidal instability, irradiation-induced secondary mass overflow, and the plain vanilla disk limit cycle instability. I discuss the properties of the outbursts in two SU UMa systems observed by Kepler in the context of the three theories. I conclude with a look beyond the SU UMa systems.

  11. [Transient amnesia in the elderly].

    Science.gov (United States)

    Sellal, François

    2006-03-01

    The two main aetiologies of transient amnesia in the elderly are idiopathic transient global amnesia (TGA) and iatrogenic or toxic amnesia. Vascular and epileptic amnesia are less common. According to the literature, transient psychogenic amnesia, which is a frequent cause of amnesia at age 30 to 50, is very rare in the elderly. TGA is the prototypical picture of transient amnesia. It occurs more often after age 50, with no identified cause, even if some authors accept emotional stress or minor head trauma as occasional precipitants. The mechanism of TGA remains a matter of discussion. It may be the consequence of a spreading depression similar to that described in migraine with aura, but other arguments support an ischemic mechanism. Iatrogenic amnesias are mainly caused by benzodiazepines (BZs) or anticholinergics. The former may occur in a non-anxious subject, who is not a usual consumer of BZ and takes a single dose. The latter are more often due to a hypersensitivity to anticholinergic drugs, in particular in patients presenting with a covert, incipient Alzheimer's disease. A vascular origin must be considered when amnesia is accompanied by other neurological symptoms, and when the regression of the amnesic disorder is slow, lasting several days. It results from lesions involving various mechanisms and locations, mainly subcortical. Partial seizures, most often mesio-temporal, more rarely frontal, may be the cause of transient amnesia in the elderly, in the absence of a past history of epilepsy. The red flag supportive of an epileptic origin is the repetition of stereotyped amnesic episodes. EEG demonstration of seizures may be difficult and the response to antiepileptic drugs effective on partial seizures is usually good.

  12. Renewed Activity from the X-Ray Transient SAXJ 1810.8-2609 with Integral

    Science.gov (United States)

    Fiocchi, M.; Natalucci, L.; Chenevez, J.; Bazzano, A.; Tarana, A.; Ubertini, P.; Brandt, S.; Beckmann, V.; Federici, M.; Galis, R.; Hudec, R.

    2009-03-01

    We report on the results of International Gamma-Ray Astrophysics Laboratory (INTEGRAL) observations of the neutron star low-mass X-ray binary SAX J1810.8-2609 during its latest active phase in 2007 August. The current outburst is the first one since 1998 and the derived luminosity is 1.1-2.6 ×1036 erg s-1 in the 20-100 keV energy range. This low outburst luminosity and the long-term time-average accretion rate of ~5 × 10-12 M sun yr-1 suggest that SAX J1810.8-2609 is a faint soft X-ray transient. During the flux increase, spectra are consistent with a thermal Comptonization model with a temperature plasma of kT e~ 23-30 keV and an optical depth of τ~ 1.2-1.5, independent of the luminosity of the system. This is a typical low hard spectral state for which the X-ray emission is attributed to the upscattering of soft seed photons by a hot, optically thin electron plasma. During the decay, spectra have a different shape, the high energy tail being compatible with a single power law. This confirm similar behavior observed by BeppoSAX during the previous outburst, with the absence of visible cutoff in the hard X-ray spectrum. INTEGRAL/JEM-X instrument observed four X-ray bursts in Fall 2007. The first one has the highest peak flux (≈3.5 crab in 3-25 keV) giving an upper limit to the distance of the source of about 5.7 kpc, for a L Edd ≈ 3.8 × 1038 erg s-1. The observed recurrence time of ~ 1.2 days and the ratio of the total energy emitted in the persistent flux to that emitted in the bursts (α~ 73) allow us to conclude that the burst fuel was composed by mixed hydrogen and helium with X >= 0.4. INTEGRAL is an ESA project with Instruments and Science Data Center funded by ESA member states, especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain; Czech Republic and Poland; and with the participation of Russia and USA.

  13. Outbursts of binary X-ray sources suitable for monitoring of their

    Czech Academy of Sciences Publication Activity Database

    Šimon, Vojtěch

    -, č. 125 (2010), s. 21-23 ISSN 1801-5964 R&D Projects: GA ČR GA205/08/1207 Grant - others:ESA(XE) ESA-PECS project No. 98058 Institutional research plan: CEZ:AV0Z10030501 Keywords : satellites * high energy sources * X-ray transients Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  14. The 2014-2017 outburst of the young star ASASSN-13db. A time-resolved picture of a very-low-mass star between EXors and FUors

    Science.gov (United States)

    Sicilia-Aguilar, A.; Oprandi, A.; Froebrich, D.; Fang, M.; Prieto, J. L.; Stanek, K.; Scholz, A.; Kochanek, C. S.; Henning, Th.; Gredel, R.; Holoien, T. W.-S.; Rabus, M.; Shappee, B. J.; Billington, S. J.; Campbell-White, J.; Zegmott, T. J.

    2017-11-01

    Context. Accretion outbursts are key elements in star formation. ASASSN-13db is a M5-type star with a protoplanetary disk, the lowest-mass star known to experience accretion outbursts. Since its discovery in 2013, it has experienced two outbursts, the second of which started in November 2014 and lasted until February 2017. Aims: We explore the photometric and spectroscopic behavior of ASASSN-13db during the 2014-2017 outburst. Methods: We use high- and low-resolution spectroscopy and time-resolved photometry from the ASAS-SN survey, the LCOGT and the Beacon Observatory to study the light curve of ASASSN-13db and the dynamical and physical properties of the accretion flow. Results: The 2014-2017 outburst lasted for nearly 800 days. A 4.15 d period in the light curve likely corresponds to rotational modulation of a star with hot spot(s). The spectra show multiple emission lines with variable inverse P-Cygni profiles and a highly variable blue-shifted absorption below the continuum. Line ratios from metallic emission lines (Fe I/Fe II, Ti I/Ti II) suggest temperatures of 5800-6000 K in the accretion flow. Conclusions: Photometrically and spectroscopically, the 2014-2017 event displays an intermediate behavior between EXors and FUors. The accretion rate ([Ṁ]= 1-3 × 10-7 M⊙/yr), about two orders of magnitude higher than the accretion rate in quiescence, is not significantly different from the accretion rate observed in 2013. The absorption features in the spectra suggest that the system is viewed at a high angle and drives a powerful, non-axisymmetric wind, maybe related to magnetic reconnection. The properties of ASASSN-13db suggest that temperatures lower than those for solar-type stars are needed for modeling accretion in very-low-mass systems. Finally, the rotational modulation during the outburst reveals that accretion-related structures settle after the beginning of the outburst and can be relatively stable and long-lived. Our work also demonstrates the power

  15. TIDALLY INDUCED OUTBURSTS IN OJ 287 DURING 2005-2008

    International Nuclear Information System (INIS)

    Valtonen, M. J.; Nilsson, K.; Villforth, C.; Lehto, H. J.; Takalo, L. O.; Lindfors, E.; Sillanpaeae, A.; Hentunen, V.-P.; Mikkola, S.; Zola, S.; Drozdz, M.; Ogloza, W.; Winiarski, M.; Koziel, D.; Kurpinska-Winiarska, M.; Siwak, M.; Heidt, J.; Kidger, M.; Pursimo, T.; Wu, J.-H.

    2009-01-01

    The blazar OJ 287 has produced two major optical outburst events during the years 2005-2008. These are the latest in a series of outbursts that have occurred repeatedly at 12 year intervals since early 1900s. It has been possible to explain the historical light curve fairly well by using a binary black hole model where the secondary black hole impacts the accretion disk of the primary twice during the 12 year orbital cycle. We will ask here how well does the latest light-curve fit with this model. We use a 10 million particle disk to model the accretion disk of the primary black hole. The rate of transfer of particles through the 10 Schwarzschild radius cylinder around the primary is followed. The secondary induces an inward flow through this surface. The inward flow rate is compared with the historical light curve as well as with the most recent observations reported in this paper. The observations have been carried out by using a number of small and medium size telescopes in different locations in order to ensure a dense light-curve coverage. The 'inflow light curve' and the optical light curve of OJ 287 have a close resemblance to each other. It suggests that the tidally induced accretion flow is responsible for the main features of the optical light curve, with the exception of the quasi-periodic double peaks. It implies a close connection between the accretion disk and the jet where the optical synchrotron emission is presumably generated.

  16. The Cyclic variation of the outburst recurrence time in GRS 1747-312

    Czech Academy of Sciences Publication Activity Database

    Šimon, Vojtěch

    2009-01-01

    Roč. 14, č. 5 (2009), s. 443-450 ISSN 1384-1076 Institutional research plan: CEZ:AV0Z10030501 Keywords : X-ray transients * neutron stars * X-rays binaries Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 1.675, year: 2009

  17. Forecast and Prevention of Coal and Gas Outbursts in the Case of Application of a New Mining Method - Drilling of a Coal Pillar

    Directory of Open Access Journals (Sweden)

    Vlastimil Hudeček

    2010-10-01

    Full Text Available Coal and gas outbursts are one of risk factors accompanying the mining of coal in low seams in the Ostrava-Karviná Coalfield.At the use of the method of longwall mining, all coal reserves have not been mined out owing to tectonic faults. For mining outthe residual reserves, the application of a new mining method - drilling of a coal pillar was proposed.The method of mining of a coal seam utilizing long large diameter boreholes is verified in the Paskov Mine (company OKD, JSC –Czech Republic under conditions of rock mass with hazard of rock and gas outbursts in localities of residual pillars left in seams afterfinishing the mining operations performed with using the classical method of longwall working along the strike. [5]Forecast and preventive measures applied to the verification of the new method were based on previous experience withthe mining of seams with hazard of coal and gas outbursts. They accepted fully valid legislation, i.e. Ordinance of Ostrava RegionalMining Authority No. 3895/2002 and supplementary materials (Instructions and Guidelines. The proposed measures respectedthe character of the method being verified. [4]For all areas being mined, projects containing also chapters specifying the problems of ensuring the safety of mining worksand operation under conditions of hazard of coal and gas outbursts were prepared.In the contributions, basic proposals for the principles of coal and gas outburst forecast and prevention when applying the newmining method – drilling of a coal pillar are presented

  18. POST-OUTBURST RADIO OBSERVATIONS OF THE HIGH MAGNETIC FIELD PULSAR PSR J1119-6127

    Energy Technology Data Exchange (ETDEWEB)

    Majid, Walid A.; Pearlman, Aaron B.; Dobreva, Tatyana; Kocz, Jonathon; Prince, Thomas A. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Horiuchi, Shinji [CSIRO Astronomy and Space Science, Canberra Deep Space Communications Complex, P.O. Box 1035, Tuggeranong, ACT 2901 (Australia); Lippuner, Jonas [TAPIR, Walter Burke Institute for Theoretical Physics, MC 350-17, California Institute of Technology, Pasadena, CA 91125 (United States)

    2017-01-01

    We have carried out high-frequency radio observations of the high magnetic field pulsar PSR J1119-6127 following its recent X-ray outburst. While initial observations showed no evidence of significant radio emission, subsequent observations detected pulsed emission across a large frequency band. In this Letter, we report on the initial disappearance of the pulsed emission and its prompt reactivation and dramatic evolution over several months of observation. The periodic pulse profile at S -band (2.3 GHz) after reactivation exhibits a multi-component emission structure, while the simultaneous X -band (8.4 GHz) profile shows a single emission peak. Single pulses were also detected at S -band near the main emission peaks. We present measurements of the spectral index across a wide frequency bandwidth, which captures the underlying changes in the radio emission profile of the neutron star. The high-frequency radio detection, unusual emission profile, and observed variability suggest similarities with magnetars, which may independently link the high-energy outbursts to magnetar-like behavior.

  19. Multiwavelength Picture of the Blazar S5 0716+714 during Its Brightest Outburst

    Directory of Open Access Journals (Sweden)

    Marina Manganaro

    2016-11-01

    Full Text Available S5 0716+714 is a well known BL Lac object, and one of the brightest and most active blazars. The discovery in the Very High Energy band (VHE, E > 100 GeV by MAGIC happened in 2008. In January 2015, the source went through the brightest optical state ever observed, triggering MAGIC follow-up and a VHE detection with ∼ 13 σ significance (ATel ♯ 6999 . Rich multiwavelength coverage of the flare allowed us to construct the broad-band spectral energy distribution of S5 0716+714 during its brightest outburst. In this work, we will present the preliminary analysis of MAGIC and Fermi-LAT data of the flaring activity in January and February 2015 for the HE (0.1 < HE < 300 GeV and VHE band, together with radio (Metsähovi, OVRO, VLBA, Effelsberg, sub-millimeter (SMA, optical (Tuorla, Perkins, Steward, AZT-8+ST7, LX-200, Kanata, X-ray and UV (Swift-XRT and UVOT, in the same time-window and discuss the time variability of the multiwavelength light curves during this impressive outburst.

  20. Detecting EUV transients in near real time with ALEXIS

    Energy Technology Data Exchange (ETDEWEB)

    Roussel-Dupre`, D.; Bloch, J.J.; Theiler, J.; Pfafman, T.; Beauchesne, B.

    1995-12-31

    The Array of Low Energy X-ray Imaging Sensors (ALEXIS) experiment consists of a mini-satellite containing six wide angle EUV/ultrasoft X-ray telescopes (Priedhorsky et al. 1989, and Bloch et al. 1994). Its scientific objective is to map out the sky in three narrow ({Delta}E/E {approx} 5%) bandpasses around 66, 71, and 93 eV. During each 50 second satellite rotation period the six telescopes, each with a 30{degrees} field, of:view and a spatial resolution of 0.25{degrees}, scan most of the antisolar hemisphere of the sky. The project is a collaborative effort between Los Alamos National Laboratory, Sandia National Laboratory, and the University of California-Berkeley Space Sciences Laboratory. It is controlled entirely from a small ground station located at Los Alamos. The mission was launched on a Pegasus Air Launched Vehicle on April 25, 1993. An incident at launch delayed our ability to properly analyze the data until November of 1994. In January of 1995, we brought on line automated software to routinely carry out the transient search. After the data is downlinked from the satellite, the software processes and transforms it into sky maps that are automatically searched for new sources. The software then sends the results of these searches by e-mail to the science team within two hours of the downlink. This system has successfully detected the Cataclysmic Variables VW Hyi, U Gem and AR UMa in outburst, and has detected at least two unidentified short duration EUV transients (Roussel-Dupre et al 1995, Roussel-Dupre 1995).

  1. Timing Studies and QPO Detection for Transient Xray Pulsar 4u 0115+634 by RXTE.

    Science.gov (United States)

    Ram Dugair, Moti; Jaaffrey, S. N. A.

    We present results of timing analysis of data of the transient X-ray pulsar 4U 0115+634 (Neu-tron star with fast spin entry) taken by the Rossi X-ray Timing Explorer (RXTE) space satellite. We first time observed the occurrence of 3 QPOs of 3 m Hz, 8 m Hz and 60 m Hz of the X-ray outburst of 2008. In particular the frequencies of the QPO's may be attributed to those of oscillations of disturbance occuring in the inner region of the accreted disk of the neutron star during the truncation of viscous circum stellar disc around the Be-star. The role of the interaction between the neutron star and the circumstellar is very important. Appearance of three QPOs in X-ray Binary system is a new phenomenon and difficult to understand.

  2. SCANAIR: A transient fuel performance code

    International Nuclear Information System (INIS)

    Moal, Alain; Georgenthum, Vincent; Marchand, Olivier

    2014-01-01

    Highlights: • Since the early 1990s, the code SCANAIR is developed at IRSN. • The software focuses on studying fast transients such as RIA in light water reactors. • The fuel rod modelling is based on a 1.5D approach. • Thermal and thermal-hydraulics, mechanical and gas behaviour resolutions are coupled. • The code is used for safety assessment and integral tests analysis. - Abstract: Since the early 1990s, the French “Institut de Radioprotection et de Sûreté Nucléaire” (IRSN) has developed the SCANAIR computer code with the view to analysing pressurised water reactor (PWR) safety. This software specifically focuses on studying fast transients such as reactivity-initiated accidents (RIA) caused by possible ejection of control rods. The code aims at improving the global understanding of the physical mechanisms governing the thermal-mechanical behaviour of a single rod. It is currently used to analyse integral tests performed in CABRI and NSRR experimental reactors. The resulting validated code is used to carry out studies required to evaluate margins in relation to criteria for different types of fuel rods used in nuclear power plants. Because phenomena occurring during fast power transients are complex, the simulation in SCANAIR is based on a close coupling between several modules aimed at modelling thermal, thermal-hydraulics, mechanical and gas behaviour. During the first stage of fast power transients, clad deformation is mainly governed by the pellet–clad mechanical interaction (PCMI). At the later stage, heat transfers from pellet to clad bring the cladding material to such high temperatures that the boiling crisis might occurs. The significant over-pressurisation of the rod and the fact of maintaining the cladding material at elevated temperatures during a fairly long period can lead to ballooning and possible clad failure. A brief introduction describes the context, the historical background and recalls the main phenomena involved under

  3. SCANAIR: A transient fuel performance code

    Energy Technology Data Exchange (ETDEWEB)

    Moal, Alain, E-mail: alain.moal@irsn.fr; Georgenthum, Vincent; Marchand, Olivier

    2014-12-15

    Highlights: • Since the early 1990s, the code SCANAIR is developed at IRSN. • The software focuses on studying fast transients such as RIA in light water reactors. • The fuel rod modelling is based on a 1.5D approach. • Thermal and thermal-hydraulics, mechanical and gas behaviour resolutions are coupled. • The code is used for safety assessment and integral tests analysis. - Abstract: Since the early 1990s, the French “Institut de Radioprotection et de Sûreté Nucléaire” (IRSN) has developed the SCANAIR computer code with the view to analysing pressurised water reactor (PWR) safety. This software specifically focuses on studying fast transients such as reactivity-initiated accidents (RIA) caused by possible ejection of control rods. The code aims at improving the global understanding of the physical mechanisms governing the thermal-mechanical behaviour of a single rod. It is currently used to analyse integral tests performed in CABRI and NSRR experimental reactors. The resulting validated code is used to carry out studies required to evaluate margins in relation to criteria for different types of fuel rods used in nuclear power plants. Because phenomena occurring during fast power transients are complex, the simulation in SCANAIR is based on a close coupling between several modules aimed at modelling thermal, thermal-hydraulics, mechanical and gas behaviour. During the first stage of fast power transients, clad deformation is mainly governed by the pellet–clad mechanical interaction (PCMI). At the later stage, heat transfers from pellet to clad bring the cladding material to such high temperatures that the boiling crisis might occurs. The significant over-pressurisation of the rod and the fact of maintaining the cladding material at elevated temperatures during a fairly long period can lead to ballooning and possible clad failure. A brief introduction describes the context, the historical background and recalls the main phenomena involved under

  4. Review of HEDL fuel pin transient analyses analytical programs

    International Nuclear Information System (INIS)

    Scott, J.H.; Baars, R.E.

    1975-05-01

    Methods for analysis of transient fuel pin performance are described, as represented by the steady-state SIEX code and the PECT series of codes used for steady-state and transient mechanical analyses. The empirical fuel failure correlation currently in use for analysis of transient overpower accidents is described. (U.S.)

  5. Mechanical behavior of irradiated fuel-pin cladding evaluated under transient heating and pressure conditions

    International Nuclear Information System (INIS)

    Hamilton, M.L.; Johnson, G.D.; Hunter, C.W.; Duncan, D.R.

    1982-11-01

    Fast breeder fuel-pin cladding has been tested under experimental conditions simulating the temperature and pressure history characteristic of anticipated transient events. Irradiation induces severe reductions in both strength and ductility. Ductility losses are independent of the rate of temperature increase and saturate by a fluence of approx. 2 x 10 22 n/cm 2 (E > 0.1 MeV). Losses in strength are dependent on the rate of temperature increase but saturate at a fluence of approx.5 x 10 22 n/cm 2 . Evidence is presented to show that fission products are probably responsible for the degradation in mechanical properties

  6. Fission gas behavior during fast thermal transients

    International Nuclear Information System (INIS)

    Esteves, R.G.

    1976-01-01

    The behavior of non-equilibrium fission in fuel elements undergoing fast thermal transients is analyzed. To facilitate the analysis, a new variable, the equilibrium variable (EV) is defined. This variable, together with bubble radius, completely specifies a bubble with respect to its size and equilibrium condition. The analysis is coded using a two-variable (radius and EV) multigroup numerical approximation that accepts as input the time-temperature history, the time-fission rate history, and the time-thermal gradient history of the fuel element. Studies were performed to test the code for convergence with respect to the time interval and the number of groups chosen. For a series of transient simulation studies, the measurements obtained at HEDL (microscopic examination of intragranular porosity in oxide fuel transient-tested in TREAT) are used. Two different transient histories were selected; the first, a high-temperature transient (HTT) with a peak at 2477 0 K and the second, a low-temperature transient (LTT) with a peak-temperature at 2000 0 K. The LTT was simulated for three different conditions: Bubbles were allowed to move via (a) only biased migration, (b) via random migration, and (c) via both mechanisms. The HTT was also run for both mechanisms. The agreement with HEDL microscopic observations was fair for bubbles smaller than 964 A in diameter, and poor for larger bubbles. Bubbles that grew during the heat-up part of the transient were frozen at a larger size during the cool down

  7. X-Ray Observations of Magnetar SGR 0501+4516 from Outburst to Quiescence

    Science.gov (United States)

    Mong, Y.-L.; Ng, C.-Y.

    2018-01-01

    Magnetars are neutron stars having extreme magnetic field strengths. Study of their emission properties in quiescent state can help understand effects of a strong magnetic field on neutron stars. SGR 0501+4516 is a magnetar that was discovered in 2008 during an outburst, which has recently returned to quiescence. We report its spectral and timing properties measured with new and archival observations from the Chandra X-ray Observatory, XMM-Newton, and Suzaku. We found that the quiescent spectrum is best fit by a power-law plus two blackbody model, with temperatures of kT low ∼ 0.26 keV and kT high ∼ 0.62 keV. We interpret these two blackbody components as emission from a hotspot and the entire surface. The hotspot radius shrunk from 1.4 km to 0.49 km since the outburst, and there was a significant correlation between its area and the X-ray luminosity, which agrees well with the prediction by the twisted magnetosphere model. We applied the two-temperature spectral model to all magnetars in quiescence and found that it could be a common feature among the population. Moreover, the temperature of the cooler blackbody shows a general trend with the magnetar field strength, which supports the simple scenario of heating by magnetic field decay.

  8. Monitoring of the Y2K Outburst of Cyg X-3 with BeppoSAX

    Science.gov (United States)

    Palazzi, E.; dal Fiume, D.; Amati, L.; del Sordo, S.; Frontera, F.; Masetti, N.; Orlandini, M.; Santangelo, A.; Segreto, A.

    2001-09-01

    The latest outburst of Cyg X-3, occurred during year 2000, was extensively monitored with the BeppoSAX satellite, which observed the source 6 times at different brightness levels. We here report on these observations, in which the X-ray spectrum appears very complex and strongly evolving as the brightness of the object changes.

  9. A Fisher’s Criterion-Based Linear Discriminant Analysis for Predicting the Critical Values of Coal and Gas Outbursts Using the Initial Gas Flow in a Borehole

    Directory of Open Access Journals (Sweden)

    Xiaowei Li

    2017-01-01

    Full Text Available The risk of coal and gas outbursts can be predicted using a method that is linear and continuous and based on the initial gas flow in the borehole (IGFB; this method is significantly superior to the traditional point prediction method. Acquiring accurate critical values is the key to ensuring accurate predictions. Based on ideal rock cross-cut coal uncovering model, the IGFB measurement device was developed. The present study measured the data of the initial gas flow over 3 min in a 1 m long borehole with a diameter of 42 mm in the laboratory. A total of 48 sets of data were obtained. These data were fuzzy and chaotic. Fisher’s discrimination method was able to transform these spatial data, which were multidimensional due to the factors influencing the IGFB, into a one-dimensional function and determine its critical value. Then, by processing the data into a normal distribution, the critical values of the outbursts were analyzed using linear discriminant analysis with Fisher’s criterion. The weak and strong outbursts had critical values of 36.63 L and 80.85 L, respectively, and the accuracy of the back-discriminant analysis for the weak and strong outbursts was 94.74% and 92.86%, respectively. Eight outburst tests were simulated in the laboratory, the reverse verification accuracy was 100%, and the accuracy of the critical value was verified.

  10. Partitioning the Outburst Energy of a Low Eddington Accretion Rate AGN at the Center of an Elliptical Galaxy: The Recent 12 Myr History of the Supermassive Black Hole in M87

    Energy Technology Data Exchange (ETDEWEB)

    Forman, W.; Jones, C.; Kraft, R.; Vikhlinin, A. [Smithsonian Astrophysical Observatory, Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Churazov, E. [MPI für Astrophysik, Karl-Schwarzschild-Strasse 1, D-85740 Garching (Germany); Heinz, S., E-mail: wrf@cfa.harvard.edu [University of Wisconsin, Madison, Wisconsin (United States)

    2017-08-01

    M87, the active galaxy at the center of the Virgo cluster, is ideal for studying the interaction of a supermassive black hole (SMBH) with a hot, gas-rich environment. A deep Chandra observation of M87 exhibits an approximately circular shock front (13 kpc radius, in projection) driven by the expansion of the central cavity (filled by the SMBH with relativistic radio-emitting plasma) with projected radius ∼1.9 kpc. We combine constraints from X-ray and radio observations of M87 with a shock model to derive the properties of the outburst that created the 13 kpc shock. Principal constraints for the model are (1) the measured Mach number ( M ∼ 1.2), (2) the radius of the 13 kpc shock, and (3) the observed size of the central cavity/bubble (the radio-bright cocoon) that serves as the piston to drive the shock. We find that an outburst of ∼5 × 10{sup 57} erg that began about 12 Myr ago and lasted ∼2 Myr matches all the constraints. In this model, ∼22% of the energy is carried by the shock as it expands. The remaining ∼80% of the outburst energy is available to heat the core gas. More than half the total outburst energy initially goes into the enthalpy of the central bubble, the radio cocoon. As the buoyant bubble rises, much of its energy is transferred to the ambient thermal gas. For an outburst repetition rate of about 12 Myr (the age of the outburst), 80% of the outburst energy is sufficient to balance the radiative cooling.

  11. New developments in French transient monitoring: SYSFAC

    International Nuclear Information System (INIS)

    L'huby, Y.; Genette, P.; Faidy, C.; Kappler, F.; Balley, J.; Bimont, G.

    1991-01-01

    After more than ten years of experience with Transient Monitoring and Logging Procedure (TMLP) and six years of successfully experience with Fatiguemeters, EDF has decided to study a new concept of Fatigue Monitoring System: SYSFAC. This new automatic system which is developed to be operating in all the French PWR units is composed of three modules: mechanical transient logging, functional transient logging and fatiguemeters. This application must be connected to the on-site data acquisition system without complementary instrumentation on the plant. (author)

  12. Radio and white-light observations of coronal transients

    International Nuclear Information System (INIS)

    Dulk, G.A.

    1980-01-01

    Optical, radio and X-ray evidence of violent mass motions in the corona has existed for some years but only recently have the form, nature, frequency and implication of the transients become obvious. The author reviews the observed properties of coronal transients, concentrating on the white-light and radio manifestations. The classification according to speeds seems to be meaningful, with the slow transients having thermal emissions at radio wavelengths and the fast ones non-thermal. The possible mechanisms involved in the radio bursts are discussed and the estimates of various forms of energy are reviewed. It appears that the magnetic energy transported from the Sun by the transient exceeds that of any other form, and that magnetic forces dominate in the dynamics of the motions. The conversion of magnetic energy into mechanical energy, by expansion of the fields, provides a possible driving force for the coronal and interplanetary shock waves. (Auth.)

  13. OUTBURST OF COMET 17P/HOLMES OBSERVED WITH THE SOLAR MASS EJECTION IMAGER

    International Nuclear Information System (INIS)

    Li Jing; Jewitt, David; Clover, John M.; Jackson, Bernard V.

    2011-01-01

    We present time-resolved photometric observations of the Jupiter family comet 17P/Holmes during its dramatic 2007 outburst. The observations, from the orbiting Solar Mass Ejection Imager (SMEI), provide the most complete measure of the whole-coma brightness, free from the effects of instrumental saturation and with a time resolution well matched to the rapid brightening of the comet. The light curve is divided into two distinct parts. A rapid rise between the first SMEI observation on UT 2007 October 24 06h 37m (mid-integration) and UT 2007 October 25 is followed by a slow decline until the last SMEI observation on UT 2008 April 6 22h 16m (mid-integration). We find that the rate of change of the brightness is reasonably well described by a Gaussian function having a central time of UT 2007 October 24.54 ± 0.01 and a full width at half-maximum of 0.44 ± 0.02 days. The maximum rate of brightening occurs some 1.2 days after the onset of activity. At the peak, the scattering cross-section grows at 1070 ± 40 km 2 s -1 while the (model-dependent) mass loss rates inferred from the light curve reach a maximum at 3 x 10 5 kg s -1 . The integrated mass in the coma lies in the range (2-90) x 10 10 kg, corresponding to 0.2%-10% of the nucleus mass, while the kinetic energy of the ejecta is (0.7-30) megatonnes TNT. The particulate coma mass could be contained within a shell on the nucleus of thickness 1-60 m. This is also the approximate distance traveled by conducted heat in the century since the previous outburst of 17P/Holmes. This coincidence is consistent with, but does not prove, the idea that the outburst was triggered by the action of conducted heat, possibly through the crystallization of buried amorphous ice.

  14. Transient Liquid Water as a Mechanism for Induration of Soil Crusts on Mars

    Science.gov (United States)

    Landis, G. A.; Blaney, D.; Cabrol, N.; Clark, B. C.; Farmer, J.; Grotzinger, J.; Greeley, R.; McLennan, S. M.; Richter, L.; Yen, A.

    2004-01-01

    The Viking and the Mars Exploration Rover missions observed that the surface of Mars is encrusted by a thinly cemented layer tagged as "duricrust". A hypothesis to explain the formation of duricrust on Mars should address not only the potential mechanisms by which these materials become cemented, but also the textural and compositional components of cemented Martian soils. Elemental analyzes at five sites on Mars show that these soils have sulfur content of up to 4%, and chlorine content of up to 1%. This is consistent with the presence of sulfates and halides as mineral cements. . For comparison, the rock "Adirondack" at the MER site, after the exterior layer was removed, had nearly five times lower sulfur and chlorine content , and the Martian meteorites have ten times lower sulfur and chlorine content, showing that the soil is highly enriched in the saltforming elements compared with rock.Here we propose two alternative models to account for the origin of these crusts, each requiring the action of transient liquid water films to mediate adhesion and cementation of grains. Two alternative versions of the transient water hypothesis are offered, a top down hypothesis that emphasizes the surface deposition of frost, melting and downward migration of liquid water and a bottom up alternative that proposes the presence of interstitial ice/brine, with the upward capillary migration of liquid water.

  15. Impacts of the 2016 outburst flood on the Bhote Koshi River valley, central Nepal

    Science.gov (United States)

    Cook, Kristen; Andermann, Christoff; Gimbert, Florent; Hovius, Niels; Adhikari, Basanta

    2017-04-01

    The central Nepal Himalaya is a region of rapid erosion where fluvial processes are largely driven by the annual Indian Summer Monsoon, which delivers up to several meters of precipitation each year. However, the rivers in this region are also subject to rare catastrophic floods caused by the sudden failure of landslide or moraine dams. Because these floods happen rarely, it has been difficult to isolate their impact on the rivers and adjacent hillslopes, and their importance for the long-term evolution of Himalayan rivers is poorly constrained. On the 5th of July, 2016, the Bhote Koshi River in central Nepal was hit by a glacial lake outburst flood (GLOF). The flood passed through a seismic and hydrological observatory installed along the river in June 2015, and we have used the resulting data to constrain the timing, duration, and bedload transport properties of the outburst flood. The impact of the flood on the river can be further observed with hourly time-lapse photographs, daily measurements of suspended sediment load, repeat lidar surveys, and satellite imagery. Overall, our observatory data span two monsoon seasons, allowing us to evaluate the impacts of the outburst flood relative to the annual monsoon flood. The outburst flood affected the river on several timescales. In the short term, it transported large amounts of coarse sediment and restructured the river bed during the hours of the flood pulse itself. Over intermediate timescales it resulted in elevated bedload and suspended load transport for several weeks following the flood. Over longer timescales the flood undercut and destabilized the river banks and hillslopes in a number of locations, leading to bank collapses, slumps, and landslides. We map changes in the channel and associated mass wasting using rapidEye imagery from Oct. 2015 and Oct. 2016. We also use repeat terrestrial lidar scans to quantify the magnitude of change in multiple locations along the river channel and to measure bank

  16. Discovery and Evolution of the New Black Hole Candidate Swift J1539.2-6227 During Its 2008 Outburst

    Science.gov (United States)

    Krimm, H. A.; Tomsick, J. A.; Markwardt, C. B.; Brocksopp, C.; Grise, F.; Kaaret, P.; Romano, P.

    2010-01-01

    We report on the discovery by the Swift Gamma-Ray Burst Explorer of the black hole candidate Swift J1539.2-6227 and the subsequent course of an outburst beginning in November 2008 and lasting at least seven months. The source was discovered during normal observations with the Swift Burst Alert Telescope (BAT) on 2008 November 25. An extended observing campaign with the Rossi X-Ray Timing Explorer (RXTE) and Swift provided near-daily coverage over 176 days, giving us a rare opportunity to track the evolution of spectral and timing parameters with fine temporal resolution through a series of spectral states. The source was first detected in a hard state during which strong low-frequency quasiperiodic oscillations (QPOs) were detected. The QPOs persisted for about 35 days and a signature of the transition from the hard to soft intermediate states was seen in the timing data. The source entered a short-lived thermal state about 40 days after the start of the outburst. There were variations in spectral hardness as the source flux declined and returned to a hard state at the end of the outburst. The progression of spectral states and the nature of the timing features provide strong evidence that Swift J1539.2-6227 is a candidate black hole in a low-mass X-ray binary system.

  17. Transient fault tolerant control for vehicle brake-by-wire systems

    International Nuclear Information System (INIS)

    Huang, Shuang; Zhou, Chunjie; Yang, Lili; Qin, Yuanqing; Huang, Xiongfeng; Hu, Bowen

    2016-01-01

    Brake-by-wire (BBW) systems that have no mechanical linkage between the brake pedal and the brake mechanism are expected to improve vehicle safety through better braking capability. However, transient faults in BBW systems can cause dangerous driving situations. Most existing research in this area focuses on the brake control mechanism, but very few studies try to solve the problem associated with transient fault propagation and evolution in the brake control system hierarchy. In this paper, a hierarchical transient fault tolerant scheme with embedded intelligence and resilient coordination for BBW system is proposed based on the analysis of transient fault propagation characteristics. In this scheme, most transient faults are tackled rapidly by a signature-based detection method at the node level, and the remaining transient faults, which cannot be detected directly at the node level and could degrade the system performance through fault propagation and evolution, are detected and recovered through function and structure models at the system level. To jointly accommodate these BBW transient faults at the system level, a sliding mode control algorithm and a task reallocation strategy are designed. A simulation platform based on Architecture Analysis and Design Language (AADL) is established to evaluate the task reallocation strategy, and a hardware-in-the-loop simulation is carried out to validate the proposed scheme systematically. Experimental results show the effectiveness of this new approach to BBW systems. - Highlights: • We propose a hierarchical transient fault tolerant scheme for BBW systems. • A sliding mode algorithm and a task strategy are designed to tackle transient fault. • The effectiveness of the scheme is verified in both simulation and HIL environments.

  18. Irradiation creep transients in Ni-4 at.% Si

    International Nuclear Information System (INIS)

    Nagakawa, J.

    1983-01-01

    In the course of irradiation creep experiments on Ni-4 at.% Si alloy, two types of creep transients were observed on the termination of irradiation. The short term transient was completed within one minute while the long term transient persisted for nearly ten hours. A change in the temperature distribution was excluded from the possible causes, partly because the stress dependence of the observed transient strains was not linear, and partly because the strain increase expected from the temperature change was much smaller than the observed value. Transient behavior of point defects was examined in conjunction with the climb-glide mechanism and the steady-state irradiation creep data. Calculated creep transient due to excess vacancy flux to dislocations was in good agreement with the observed short term transient. The long term transient appears to be a result of dislocation microstructure change. The present results suggest an enhanced irradiation creep under cyclic irradiation conditions which will be encountered in the early generations of fusion reactors. (orig.)

  19. Swift observations of the accreting millisecond pulsar IGR J17498-2921 : From outburst to quiescence

    NARCIS (Netherlands)

    Linares, M.; Bozzo, E.; Altamirano, D.; Degenaar, N.; Wijnands, R.; Soleri, P.; Belloni, T.; Di Salvo, T.; D'Ai, A.; Papitto, A.; Riggio, A.; Burderi, L.

    Swift has been monitoring the accreting millisecond pulsar IGR J17498-2921 since the start of its outburst in 2011 August 12 (ATels #3551, #3555, #3556). We detected two X-ray bursts on Aug. 18 and 28. During the first ~12 days the average persistent XRT count rate remained approximately constant at

  20. Radio and white-light observations of coronal transients

    Science.gov (United States)

    Dulk, G. A.

    1980-01-01

    Optical, radio and X-ray evidence of violent mass motions in the corona has existed for some years but only recently have the form, nature, frequency and implication of the transients become obvious. In this paper the observed properties of coronal transients are reviewed, with concentration on the white-light and radio manifestations. The classification according to speeds seems to be meaningful, with the slow transients having thermal emissions at radio wavelengths and the fast ones nonthermal. The possible mechanisms involved in the radio bursts are then discussed and estimates of various forms of energy are reviewed. It appears that the magnetic energy transported from the sun by the transient exceeds that of any other form, and that magnetic forces dominate in the dynamics of the motions. The conversion of magnetic energy into mechanical energy, by expansion of the field, provides a possible driving force for the coronal and interplanetary shock waves.

  1. Limits and challenges to compiling and developing a database of glacial lake outburst floods

    Czech Academy of Sciences Publication Activity Database

    Emmer, Adam; Vilímek, V.; Huggel, C.; Klimeš, Jan; Schaub, Y.

    2016-01-01

    Roč. 13, feb (2016), s. 1579-1584 ISSN 1612-510X R&D Projects: GA MŠk(CZ) LO1415; GA MŠk(CZ) LG15007 Institutional support: RVO:67179843 ; RVO:67985891 Keywords : Database * Glacial lake outburst floods * GLOF * ICL/IPL activities * Natural hazards Subject RIV: EH - Ecology, Behaviour; DE - Earth Magnetism, Geodesy, Geography (USMH-B) Impact factor: 3.657, year: 2016

  2. Fast thermal transients on valve

    International Nuclear Information System (INIS)

    Ferjancic, M.; Stok, B.; Halilovic, M.; Koc, P.; Mole, N.; Otrin, Z.; Kotar, A.

    2007-01-01

    One of the regulatory body methods to supervise nuclear safety of a nuclear power plant is a review of plant modifications and evaluation of their impact on plant operating experience. The Slovenian Nuclear Safety Administration (SNSA) licensed in April 2003 the use of leak-before-break (LBB) methodology in the Krsko NPP for the primary loop including surge line and connecting pipelines with minimal diameter of 6 inch. The SNSA decision based also on fracture mechanics analyses that include direct pipe failure mechanisms such as water hammer, creep damage, erosion and corrosion, fatigue and environmental conditions over the entire life of the plant. The evaluation of the operating transients pointed out, that presumed loadings, used for the LBB analysis, did not incorporate all the fast thermal transients data. For that purpose the SNSA requested Faculty of Mechanical Engineering (FS) in Ljubljana to perform additional analyses. The results of the analysis shall confirm the validity of the LBB analysis. (author)

  3. Research on generation mechanism of single event transient current generated in the semiconductor using ion accelerator

    International Nuclear Information System (INIS)

    Hirao, Toshio

    2007-01-01

    Single-event upset (SEU) is triggered when an amount of electric charges induced by energetic ion incidence exceeds a value known as a critical charge in a very short time period. Therefore, accurate evaluation of electric charge and understanding of basic mechanism of SEU are necessary for the improvement of SEU torrance of electronic devices. In this paper, the collected charges for the single event transient current induced on semiconductor by heavy ion microbeams, and application to use microbeam for single event studies are presented. (author)

  4. Multiwavelength Variations of 3C 454.3 during the 2010 November to 2011 January Outburst

    Science.gov (United States)

    Wehrle, Ann E.; Marscher, Alan P.; Jorstad, Svetlana G.; Gurwell, Mark A.; Joshi, Manasvita; MacDonald, Nicholas R.; Williamson, Karen E.; Agudo, Iván; Grupe, Dirk

    2012-10-01

    We present multiwavelength data of the blazar 3C 454.3 obtained during an extremely bright outburst from 2010 November through 2011 January. These include flux density measurements with the Herschel Space Observatory at five submillimeter-wave and far-infrared bands, the Fermi Large Area Telescope at γ-ray energies, Swift at X-ray, ultraviolet (UV), and optical frequencies, and the Submillimeter Array at 1.3 mm. From this data set, we form a series of 52 spectral energy distributions (SEDs) spanning nearly two months that are unprecedented in time coverage and breadth of frequency. Discrete correlation analysis of the millimeter, far-infrared, and γ-ray light curves show that the variations were essentially simultaneous, indicative of cospatiality of the emission, at these wavebands. In contrast, differences in short-term fluctuations at various wavelengths imply the presence of inhomogeneities in physical conditions across the source. We locate the site of the outburst in the parsec-scale "core," whose flux density as measured on 7 mm Very Long Baseline Array images increased by 70% during the first five weeks of the outburst. Based on these considerations and guided by the SEDs, we propose a model in which turbulent plasma crosses a conical standing shock in the parsec-scale region of the jet. Here, the high-energy emission in the model is produced by inverse Compton scattering of seed photons supplied by either nonthermal radiation from a Mach disk, thermal emission from hot dust, or (for X-rays) synchrotron radiation from plasma that crosses the standing shock. For the two dates on which we fitted the model SED to the data, the model corresponds very well to the observations at all bands except at X-ray energies, where the spectrum is flatter than observed.

  5. MULTIWAVELENGTH VARIATIONS OF 3C 454.3 DURING THE 2010 NOVEMBER TO 2011 JANUARY OUTBURST

    International Nuclear Information System (INIS)

    Wehrle, Ann E.; Marscher, Alan P.; Jorstad, Svetlana G.; Joshi, Manasvita; MacDonald, Nicholas R.; Williamson, Karen E.; Agudo, Iván; Gurwell, Mark A.; Grupe, Dirk

    2012-01-01

    We present multiwavelength data of the blazar 3C 454.3 obtained during an extremely bright outburst from 2010 November through 2011 January. These include flux density measurements with the Herschel Space Observatory at five submillimeter-wave and far-infrared bands, the Fermi Large Area Telescope at γ-ray energies, Swift at X-ray, ultraviolet (UV), and optical frequencies, and the Submillimeter Array at 1.3 mm. From this data set, we form a series of 52 spectral energy distributions (SEDs) spanning nearly two months that are unprecedented in time coverage and breadth of frequency. Discrete correlation analysis of the millimeter, far-infrared, and γ-ray light curves show that the variations were essentially simultaneous, indicative of cospatiality of the emission, at these wavebands. In contrast, differences in short-term fluctuations at various wavelengths imply the presence of inhomogeneities in physical conditions across the source. We locate the site of the outburst in the parsec-scale 'core', whose flux density as measured on 7 mm Very Long Baseline Array images increased by 70% during the first five weeks of the outburst. Based on these considerations and guided by the SEDs, we propose a model in which turbulent plasma crosses a conical standing shock in the parsec-scale region of the jet. Here, the high-energy emission in the model is produced by inverse Compton scattering of seed photons supplied by either nonthermal radiation from a Mach disk, thermal emission from hot dust, or (for X-rays) synchrotron radiation from plasma that crosses the standing shock. For the two dates on which we fitted the model SED to the data, the model corresponds very well to the observations at all bands except at X-ray energies, where the spectrum is flatter than observed.

  6. Engineering research on coal and gas outburst control for outburst coal seam floor roadway in deep mine%深井突出煤层底板巷防治煤与瓦斯突出工程研究

    Institute of Scientific and Technical Information of China (English)

    吕有厂; 王玉杰

    2017-01-01

    文章针对平煤股份首山一矿突出煤层结构复杂、渗透性低,致使预抽煤层瓦斯效果差、效率低的问题,以平煤股份首山一矿突出煤层底板岩巷瓦斯治理工程典型应用模式为研究对象,现场观测分析上覆突出煤层采掘过程中低板岩巷围岩应力变化规律,观测分析卸压瓦斯抽采效果,优化煤岩巷层位关系、为深部突出煤层巷道支护和抽采瓦斯提供指导,对提高深井突出煤层瓦斯治理效果具有重要的借鉴意义.%Aiming at the complex structure and low permeability of outburst coal seam in Shouyishan Coal Mine,resulting in poor effect in the gas pre-drainage,based on the typical application mode of gas control engineering in floor rock roadway of the outburst coal seam,surrounding rock stress variation law of floor rock roadway was observed and analyzed in the field during mining and tunneling in the overlying outburst coal seam.The pressure-relieving gas drainage effect was analyzed,and the position arrangement of coal and rock roadway was optimized.

  7. Model Atmosphere Spectrum Fit to the Soft X-Ray Outburst Spectrum of SS Cyg

    Directory of Open Access Journals (Sweden)

    V. F. Suleimanov

    2015-02-01

    Full Text Available The X-ray spectrum of SS Cyg in outburst has a very soft component that can be interpreted as the fast-rotating optically thick boundary layer on the white dwarf surface. This component was carefully investigated by Mauche (2004 using the Chandra LETG spectrum of this object in outburst. The spectrum shows broad ( ≈5 °A spectral features that have been interpreted as a large number of absorption lines on a blackbody continuum with a temperature of ≈250 kK. Because the spectrum resembles the photospheric spectra of super-soft X-ray sources, we tried to fit it with high gravity hot LTE stellar model atmospheres with solar chemical composition, specially computed for this purpose. We obtained a reasonably good fit to the 60–125 °A spectrum with the following parameters: Teff = 190 kK, log g = 6.2, and NH = 8 · 1019 cm−2, although at shorter wavelengths the observed spectrum has a much higher flux. The reasons for this are discussed. The hypothesis of a fast rotating boundary layer is supported by the derived low surface gravity.

  8. e-EVN radio detection of Aql X-1 in outburst

    Science.gov (United States)

    Tudose, V.; Paragi, Z.; Yang, J.; Miller-Jones, J. C. A.; Fender, R.; Garrett, M.; Rushton, A.; Spencer, R.

    2013-06-01

    The neutron star X-ray binary Aql X-1 is currently in outburst (ATel #5114, #5117, #5129, #5136, #5148). Using the European VLBI Network (e-EVN) we observed Aql X-1 at 5 GHz in two time-slots: 2013 June 18 between 19:48 - 20:36 UT (MJD 56461.825 - 56461.858), and 2013 June 19 between 02:53 - 05:54 UT (MJD 56462.120 - 56462.246). The two datasets were combined together and then calibrated. The participating radio telescopes were: Effelsberg (Germany), Jodrell Bank Mk2 (UK), Medicina (Italy), Noto (Italy), Onsala 25m (Sweden), Torun (Poland), Yebes (Spain), Westerbork Synthesis Radio Telescope (Netherlands), Shanghai (China), Hartebeesthoek (South Africa).

  9. Flare stars of the Orion Nebula - spectra of an outburst

    International Nuclear Information System (INIS)

    Carter, B.D.; O'Mara, B.J.; Ross, J.E.

    1988-01-01

    For the first time, detailed, time-resolved spectra of a flare event of an Orion cluster flare star are presented. These spectra, covering ∼ λλ3600-4600, were obtained by using the Anglo-Australian Telescope with a fibre coupler to simultaneously monitor 23 flare stars in the region of the Orion Nebula. The flare spectra reveal continuous emission which filled in the photospheric Ca I 4226 A absorption, and hydrogen Balmer, Ca II H and K, He I 4026 A and He I 4471 A line emission. Overall, the spectral behaviour indicates similarities to strong outbursts of the classical dMe flare stars. (author)

  10. Transient hardened power FETs

    International Nuclear Information System (INIS)

    Dawes, W.R. Jr.; Fischer, T.A.; Huang, C.C.C.; Meyer, W.J.; Smith, C.S.; Blanchard, R.A.; Fortier, T.J.

    1986-01-01

    N-channel power FETs offer significant advantages in power conditioning circuits. Similiarily to all MOS technologies, power FET devices are vulnerable to ionizing radiation, and are particularily susceptible to burn-out in high dose rate irradiations (>1E10 rads(Si)/sec.), which precludes their use in many military environments. This paper will summarize the physical mechanisms responsible for burn-out, and discuss various fabrication techniques designed to improve the transient hardness of power FETs. Power FET devices were fabricated with several of these techniques, and data will be presented which demonstrates that transient hardness levels in excess of 1E12 rads(Si)/sec. are easily achievable

  11. Outburst flood evolution at Russell Glacier, western Greenland

    DEFF Research Database (Denmark)

    Carrivick, Jonathan; Russell, Andrew; Ingeman-Nielsen, Thomas

    2013-01-01

    of the evolution of a bedrockchannelled outburst flood. Channel topography was obtained from digitised aerial photographs, a 5m grid resolution DEM and bathymetric surveys. Flood inundation was measured in the field from dGPS measurements. Flood evolution was analysed with application of a numerical model. Novel...... to considerable flow recirculation during the rising stage of the flood, and after overtopping of the outlet are moderated in terms of peak discharge; (ii) may have a limited geomorphological impact if sediment supply due to antecedent geomorphological activity is limited; (iii) can have kinematic waves...... that are introduced to a flood via hydraulic ponding and these waves most likely account for distinctive ‘hydropeaking’, (iv) can have a hydrograph that evolves in shape down channel and through time in a complex manner dependant on channel topography, and (v) may develop a partitioning of flow regimes...

  12. THE CONTINUING OUTBURST OF V1647 ORIONIS: WINTER/SPRING 2011 OBSERVATIONS

    International Nuclear Information System (INIS)

    Aspin, Colin

    2011-01-01

    We present optical and near-IR observations of the young eruptive variable star V1647 Orionis which illuminates McNeil's Nebula. In late 2003, V1647 Ori was observed to brighten by around 5 mag to r' = 17.7. In early 2006 the star faded back to its quiescent brightness of r' ∼ 23, however in mid-2008 it brightened yet again by ∼5 mag. Our new observations, taken in early 2011, show V1647 Ori to be in an elevated photometric state with an optical brightness similar to the value found at the start of the 2003 and 2008 outbursts. Optical images taken between 2008 and 2011 suggest that the star has remained in outburst from mid-2008 to the present. Hα and the far-red Ca II triplet lines remain in emission with Hα possessing a significant P Cygni profile. A self-consistent study of the accretion luminosity and rate using data taken in 2004, 2007, 2008, and 2011 indicates that when bright, V1647 Ori has values of 16 ± 2 L sun and (4 ± 2) x 10 -6 M sun yr -1 , respectively. We support the premise that the accretion luminosity and rate both declined by a factor of 2-3 during the 5 mag fading in 2007. However, a significant part of the fading was due to either variable extinction or dust reformation. We discuss these new observations in relation to previous published data and the classification schemes for young eruptive variables.

  13. A strongly heated neutron star in the transient z source MAXI J0556-332

    Energy Technology Data Exchange (ETDEWEB)

    Homan, Jeroen; Remillard, Ronald A. [MIT Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue 37-582D, Cambridge, MA 02139 (United States); Fridriksson, Joel K.; Wijnands, Rudy [Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands); Cackett, Edward M. [Department of Physics and Astronomy, Wayne State University, 666 W. Hancock St., Detroit, MI 48201 (United States); Degenaar, Nathalie [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Linares, Manuel [Instituto de Astrofísica de Canarias, c/ Vía Láctea s/n, E-38205 La Laguna, Tenerife (Spain); Lin, Dacheng, E-mail: jeroen@space.mit.edu [Space Science Center, University of New Hampshire, Durham, NH 03824 (United States)

    2014-11-10

    We present Chandra, XMM-Newton, and Swift observations of the quiescent neutron star in the transient low-mass X-ray binary MAXI J0556-332. Observations of the source made during outburst (with the Rossi X-ray Timing Explorer) reveal tracks in its X-ray color-color and hardness-intensity diagrams that closely resemble those of the neutron-star Z sources, suggesting that MAXI J0556-332 had near- or super-Eddington luminosities for a large part of its ∼16 month outburst. A comparison of these diagrams with those of other Z sources suggests a source distance of 46 ± 15 kpc. Fits to the quiescent spectra of MAXI J0556-332 with a neutron-star atmosphere model (with or without a power-law component) result in distance estimates of 45 ± 3 kpc, for a neutron-star radius of 10 km and a mass of 1.4 M {sub ☉}. The spectra show the effective surface temperature of the neutron star decreasing monotonically over the first ∼500 days of quiescence, except for two observations that were likely affected by enhanced low-level accretion. The temperatures we obtain for the fits that include a power law (kT{sub eff}{sup ∞} = 184-308 eV) are much higher than those seen for any other neutron star heated by accretion, while the inferred cooling (e-folding) timescale (∼200 days) is similar to other sources. Fits without a power law yield higher temperatures (kT{sub eff}{sup ∞} = 190-336 eV) and a shorter e-folding time (∼160 days). Our results suggest that the heating of the neutron-star crust in MAXI J0556-332 was considerably more efficient than for other systems, possibly indicating additional or more efficient shallow heat sources in its crust.

  14. Acute chlorine gas exposure produces transient inflammation and a progressive alteration in surfactant composition with accompanying mechanical dysfunction

    Energy Technology Data Exchange (ETDEWEB)

    Massa, Christopher B.; Scott, Pamela; Abramova, Elena; Gardner, Carol; Laskin, Debra L.; Gow, Andrew J., E-mail: Gow@rci.rutgers.edu

    2014-07-01

    Acute Cl{sub 2} exposure following industrial accidents or military/terrorist activity causes pulmonary injury and severe acute respiratory distress. Prior studies suggest that antioxidant depletion is important in producing dysfunction, however a pathophysiologic mechanism has not been elucidated. We propose that acute Cl{sub 2} inhalation leads to oxidative modification of lung lining fluid, producing surfactant inactivation, inflammation and mechanical respiratory dysfunction at the organ level. C57BL/6J mice underwent whole-body exposure to an effective 60 ppm-hour Cl{sub 2} dose, and were euthanized 3, 24 and 48 h later. Whereas pulmonary architecture and endothelial barrier function were preserved, transient neutrophilia, peaking at 24 h, was noted. Increased expression of ARG1, CCL2, RETLNA, IL-1b, and PTGS2 genes was observed in bronchoalveolar lavage (BAL) cells with peak change in all genes at 24 h. Cl{sub 2} exposure had no effect on NOS2 mRNA or iNOS protein expression, nor on BAL NO{sub 3}{sup −} or NO{sub 2}{sup −}. Expression of the alternative macrophage activation markers, Relm-α and mannose receptor was increased in alveolar macrophages and pulmonary epithelium. Capillary surfactometry demonstrated impaired surfactant function, and altered BAL phospholipid and surfactant protein content following exposure. Organ level respiratory function was assessed by forced oscillation technique at 5 end expiratory pressures. Cl{sub 2} exposure had no significant effect on either airway or tissue resistance. Pulmonary elastance was elevated with time following exposure and demonstrated PEEP refractory derecruitment at 48 h, despite waning inflammation. These data support a role for surfactant inactivation as a physiologic mechanism underlying respiratory dysfunction following Cl{sub 2} inhalation. - Highlights: • Effect of 60 ppm*hr Cl{sub 2} gas on lung inflammation and mechanical function examined. • Pulmonary inflammation is transient and minor.

  15. Evolution and Outbursts of Cataclysmic Variables

    Directory of Open Access Journals (Sweden)

    S.-B. Qian

    2015-02-01

    Full Text Available Mass transfer and accretion are very important to understand the evolution and observational properties of cataclysmic variables (CVs. Due to the lack of an accretion disk, eclipsing profiles of polars are the best source to study the character of mass transfer in CVs. By analyzing long-term photometric variations in the eclipsing polar HU Aqr, the property of mass transfer and accretion are investigated. The correlation between the brightness state change and the variation of the ingress profile suggests that both the accretion hot spot and the accretion stream are produced instantaneously. The observations clearly show that it is the variation of mass transfer causing the brightness state changes that is a direct evidence of variable mass transfer in a CV. It is shown that it is the local dark-spot activity near the L1 point to cause the change of the mass transfer rather than the activity cycles of the cool secondary star. Our results suggest that the evolution of CVs is more complex than that predicted by the standard model and we should consider the effect of variable mass accretion in nova and dwarf nova outbursts.

  16. Consequences and potential problems of operating room outbursts and temper tantrums by surgeons

    OpenAIRE

    Jacobs, George B.; Wille, Rosanne L.

    2012-01-01

    Background: Anecdotal tales of colorful temper tantrums and outbursts by surgeons directed at operating room nurses and at times other health care providers, like residents and fellows, are part of the history of surgery and include not only verbal abuse but also instrument throwing and real harassment. Our Editor-in-Chief, Dr. Nancy Epstein, has made the literature review of “Are there truly any risks and consequences when spine surgeons mistreat their predominantly female OR nursing staff/c...

  17. Hard X-ray variability of V404 Cygni during the 2015 outburst

    Science.gov (United States)

    Sánchez-Fernández, C.; Kajava, J. J. E.; Motta, S. E.; Kuulkers, E.

    2017-06-01

    Aims: Hard X-ray spectra of black hole binaries (BHB) are produced by Comptonization of soft seed photons by hot electrons near the black hole. The slope of the resulting energy spectra is governed by two main parameters: the electron temperature (Te) and optical depth (τ) of the emitting plasma. Given the extreme brightness of V404 Cyg during the 2015 outburst, we aim to constrain the source spectral properties using an unprecedented time resolution in hard X-rays, and to monitor the evolution of Te and τ over the outburst. Methods: We have extracted and analysed 602 X-ray spectra of V404 Cyg obtained by the IBIS/ISGRI instrument on-board INTEGRAL during the 2015 June outburst, using effective integration times ranging between 8 and 176 000 s. We fitted the resulting spectra in the 20-200 keV energy range. Results: We find that while the light curve and soft X-ray spectra of V404 Cyg are remarkably different from those of other BHBs, the spectral evolution of V404 Cyg in hard X-rays and the relations between the spectral parameters are consistent with those observed in other BHBs. We identify a hard branch in which the Te is anti-correlated with the hard X-ray flux, and a soft flaring branch in which the relation reverses. In addition, we find that during long X-ray plateaus detected at intermediate fluxes, the thermal Comptonization models fail to describe the spectra. However, the statistics improve if we allow NH to vary freely in the fits to these spectra. Conclusions: We conclude that the hard branch in V404 Cyg is analogous to the canonical hard state of BHBs. V404 Cyg never seems to enter the canonical soft state, although the soft flaring branch bears resemblance to the BHB intermediate state and ultra-luminous state. The X-ray plateaus are likely the result of absorption by a Compton-thick outflow (NH ≳ 1024 cm-2) which reduces the observed flux by a factor of about 10. Variable covering of the central source by this Compton-thick material may be the

  18. On the Location of the gamma-Ray Outburst Emission in the BL Lacertae Object AO 0235 + 164 Through Observations Across the Electromagnetic Spectrum

    Science.gov (United States)

    Agudo, Ivan; Marscher, Alan P.; Jorstad, Svetlana G.; Larionov, Valeri M.; Gomez, Jose L.; Laehteenmaeki, Anne; Smith, Paul S.; Nilsson, Kari; Readhead, Anthony C. S.; Aller, Margo F.; hide

    2011-01-01

    We present observations of a major outburst at centimeter, millimeter, optical, X-ray, and gamma-ray wavelengths of the BL Lacertae object AO 0235+164. We analyze the timing of multi-waveband variations in the flux and linear polarization, as well as changes in Very Long Baseline Array images at A = 7 mm with approx.0.15 milliarcsec resolution. The association of the events at different wavebands is confirmed at high statistical significance by probability arguments and Monte Carlo simulations. A series of sharp peaks in optical linear polarization, as well as a pronounced maximum in the 7 mm polarization of a superluminal jet knot, indicate rapid fluctuations in the degree of ordering of the magnetic field. These results lead us to conclude that the outburst occurred in the jet both in the quasi-stationary "core" and in the superluminal knot, both parsecs downstream of the supermassive black hole. We interpret the outburst as a consequence of the propagation of a disturbance, elongated along the line of sight by light-travel time delays, that passes through a standing recollimation shock in the core and propagates down the jet to create the superluminal knot. The multi-wavelength light curves vary together on long timescales (months/ years), but the correspondence is poorer on shorter timescales. This, as well as the variability of the polarization and the dual location of the outburst, agrees with the expectations of a multi-zone emission model in which turbulence plays a major role in modulating the synchrotron and inverse Compton fluxes.

  19. Global Crustal Dynamics of Magnetars in Relation to Their Bright X-Ray Outbursts

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Christopher [Canadian Institute for Theoretical Astrophysics, 60 St. George Street, Toronto, ON M5S 3H8 (Canada); Yang, Huan; Ortiz, Néstor [Perimeter Institute for Theoretical Physics, Waterloo, ON N2L 2Y5 (Canada)

    2017-05-20

    This paper considers the yielding response of a neutron star crust to smooth, unbalanced Maxwell stresses imposed at the core–crust boundary, and the coupling of the dynamic crust to the external magnetic field. Stress buildup and yielding in a magnetar crust are global phenomena: an elastic distortion radiating from one plastically deforming zone is shown to dramatically increase the creep rate in distant zones. Runaway creep to dynamical rates is shown to be possible, being enhanced by in situ heating and suppressed by thermal conduction and shearing of an embedded magnetic field. A global and time-dependent model of elastic, plastic, magnetic, and thermal evolution is developed. Fault-like structures develop naturally, and a range of outburst timescales is observed. Transient events with time profiles similar to giant magnetar flares (millisecond rise, ∼0.1 s duration, and decaying power-law tails) result from runaway creep that starts in localized sub-kilometer-sized patches and spreads across the crust. A one-dimensional model of stress relaxation in the vertically stratified crust shows that a modest increase in applied stress allows embedded magnetic shear to escape the star over ∼3–10 ms, dissipating greater energy if the exterior field is already sheared. Several such zones coupled to each other naturally yield a burst of duration ∼0.1 s, as is observed over a wide range of burst energies. The collective interaction of many plastic zones forces an overstability of global elastic modes of the crust, consistent with quasi-periodic oscillation (QPO) activity extending over ∼100 s. Giant flares probably involve sudden meltdown in localized zones, with high-frequency (≫100 Hz) QPOs corresponding to standing Alfvén waves within these zones.

  20. 18 centimeter VLBI observations of the quasar NRAO 140 during and after a low-frequency outburst

    International Nuclear Information System (INIS)

    Marscher, A.P.; Broderick, J.J.; Padrielli, L.; Bartel, N.; Romney, J.D.; Virginia Polytechnic Institute and State Univ., Blacksburg; CNR, Istituto di Radioastronomia, Bologna, Italy; Harvard-Smithsonian Center for Astrophysics, Cambridge, MA; Natitonal Radio Astronomy Observatory, Charlottesville, VA)

    1987-01-01

    VLBI and spectra observations have been used to identify the specific site of a low-frequency outburst in the quasar NRAO 140. The properties of the low-frequency variability in the quasar are compared with the predictions of several models. The refractive scintillation model alone does not account for the source's properties. 32 references

  1. Geometrical considerations in the transient ionization testing of digital logic circuits

    International Nuclear Information System (INIS)

    Johnston, A.

    1982-01-01

    Mechanisms are identified that can cause the transient response of digital logic circuits to depend on the logic state in which they are irradiated. Several of these mechanisms depend on surface topology, and for these cases the sensitive logic states can be determined by examining the topology. General approaches for transient radiation testing are also discussed for several MSI and LSI device technologies

  2. DIM light on Black Hole X-ray Transients

    OpenAIRE

    Dubus, Guillaume

    2005-01-01

    The current model for the outburst of stellar-mass black holes X-ray binaries is the disk instability model (DIM). An overview of this model and a discussion of its theoretical and observational challenges are given.

  3. The FU Orionis outburst as a thermal accretion event: Observational constraints for protostellar disk models

    Science.gov (United States)

    Bell, K. R.; Lin, D. N. C.; Hartmann, L. W.; Kenyon, S. J.

    1995-01-01

    The results of the time-dependent disk models developed in Bell & Lin are compared with observed properties of FU Orionis variables. Specific models are fit to the light curves of Fu Ori, V1515 Cyg, and V1057 Cyg. The slow risetime of V1515 Cyg can be matched by a self-regulated outburst model. The rapid risetimes of FU Ori and V1057 Cyg can be fitted with the application of modest perturbations to the disk surface density. Model disks display spectral features characteristic of observed objects. The color evolution of V1057 Cyg is naturally explained if mass flux drops in the inner disk (r less than 1/4 AU) while remaining steady in the outer disk. The decrease in optical line width (rotational velocity) observed during the decay of V1057 Cyg may be accounted for by an outward-propagating ionization front. We predict that before final decay to the quiescent phase, short-wavelength line widths (lambda less than 1.5 microns) will again increase. It is suggested that FU Orionis outbursts primarily occur to systems during the embedded phase with ages less than several times 10(exp 5) yr.

  4. Infrared observations of an outburst of small dust grains from the nucleus of Comet P/Halley 1986 III at perihelion

    Science.gov (United States)

    Gehrz, R. D.; Johnson, C. H.; Magnuson, S. D.; Ney, E. P.; Hayward, T. L.

    1995-01-01

    A close examination of the 0.7- to 23-micron infrared data base acquired by Gehrz and Ney (1992), suggests that the nucleus of Comet P/Halley 1986 III emitted a burst of small dust grains during a 3-day period commencing within hours of perihelion passage on 1986 February 9.46 UT. The outburst was characterized by significant increases in the coma's grain color temperature T(sub obs), temperature excess (superheat: S = T(sub obs)/T(sub BB)), infrared luminosity, albedo, and 10-micron silicate emission feature strength. These changes are all consistent with the sudden ejection from the nucleus of a cloud of grains with radii of approximately 0.5 micron. This outburst may have produced the dust that was responsible for some of the tail streamers photographed on 1986 February 22 UT. The peak of the dust outburst occurred about 3 days before a pronounced increase in the water production rate measured by the Pioneer Venus Orbiter Ultraviolet Spectrometer. We suggest that jets that release large quantities of small particles may be largely responsible for some of the variable infrared behavior that has been reported for P/Halley and other comets during the past two decades. Such jets may also account for some of the differences IR Type I and IR Type II comets.

  5. Compressive Transient Imaging

    KAUST Repository

    Sun, Qilin

    2017-04-01

    High resolution transient/3D imaging technology is of high interest in both scientific research and commercial application. Nowadays, all of the transient imaging methods suffer from low resolution or time consuming mechanical scanning. We proposed a new method based on TCSPC and Compressive Sensing to achieve a high resolution transient imaging with a several seconds capturing process. Picosecond laser sends a serious of equal interval pulse while synchronized SPAD camera\\'s detecting gate window has a precise phase delay at each cycle. After capturing enough points, we are able to make up a whole signal. By inserting a DMD device into the system, we are able to modulate all the frames of data using binary random patterns to reconstruct a super resolution transient/3D image later. Because the low fill factor of SPAD sensor will make a compressive sensing scenario ill-conditioned, We designed and fabricated a diffractive microlens array. We proposed a new CS reconstruction algorithm which is able to denoise at the same time for the measurements suffering from Poisson noise. Instead of a single SPAD senor, we chose a SPAD array because it can drastically reduce the requirement for the number of measurements and its reconstruction time. Further more, it not easy to reconstruct a high resolution image with only one single sensor while for an array, it just needs to reconstruct small patches and a few measurements. In this thesis, we evaluated the reconstruction methods using both clean measurements and the version corrupted by Poisson noise. The results show how the integration over the layers influence the image quality and our algorithm works well while the measurements suffer from non-trival Poisson noise. It\\'s a breakthrough in the areas of both transient imaging and compressive sensing.

  6. AN ENERGETIC AGN OUTBURST POWERED BY A RAPIDLY SPINNING SUPERMASSIVE BLACK HOLE OR AN ACCRETING ULTRAMASSIVE BLACK HOLE

    International Nuclear Information System (INIS)

    McNamara, B. R.; Kazemzadeh, F.; Kirkpatrick, C. C.; Rafferty, D. A.; Birzan, L.; Nulsen, P. E. J.; Wise, M. W.

    2009-01-01

    Powering the 10 62 erg nuclear outburst in the MS0735.6+7421 cluster central galaxy by accretion with a 10% mass-to-energy conversion efficiency implies that its putative supermassive black hole (SMBH) grew by ∼6 x 10 8 M sun over the past 100 Myr. Guided by data at several wavelengths, we place upper limits on the amount of cold gas and star formation near the nucleus of 9 M sun and sun yr -1 , respectively. These limits imply that an implausibly large fraction of the preexisting cold gas in the inner several kpc must have been consumed by its SMBH at the rate of ∼3-5 M sun yr -1 during the past 100 Myr while leaving no trace of star formation. Such a high accretion rate would be difficult to maintain by stellar accretion or the Bondi mechanism, unless the black hole mass approaches 10 11 M sun . Furthermore, its feeble nuclear luminosities in the UV, I, and X-ray bands compared to its enormous mechanical power are inconsistent with rapid accretion onto a ∼5 x 10 9 M sun black hole. We suggest instead that the active galactic nucleus (AGN) outburst is powered by angular momentum released from a rapidly spinning black hole. The rotational energy and power available from a spinning black hole are consistent with the cavity and shock energetics inferred from X-ray observations. A maximally spinning 10 9 M sun black hole contains enough rotational energy, ∼10 62 erg, to quench a cooling flow over its lifetime and to contribute significantly to the excess entropy found in the hot atmospheres of groups and clusters. Two modes of AGN feedback may be quenching star formation in elliptical galaxies centered in cooling halos at late times. An accretion mode that operates in gas-rich systems, and a spin mode operating at modest accretion rates. The spin conjecture may be avoided in MS0735 by appealing to Bondi accretion onto a central black hole whose mass greatly exceeds 10 10 M sun . The host galaxy's unusually large 3.8 kpc stellar core radius (light deficit) may

  7. THE X-RAY PROPERTIES OF THE BLACK HOLE TRANSIENT MAXI J1659-152 IN QUIESCENCE

    Energy Technology Data Exchange (ETDEWEB)

    Homan, Jeroen [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 70 Vassar Street, Cambridge, MA 02139 (United States); Fridriksson, Joel K.; Altamirano, Diego [Astronomical Institute ' ' Anton Pannekoek' ' , University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands); Jonker, Peter G. [SRON, Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht (Netherlands); Russell, David M. [Instituto de Astrofisica de Canarias (IAC), E-38200 La Laguna, Tenerife (Spain); Gallo, Elena [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Kuulkers, Erik [European Space Astronomy Centre (ESA/ESAC), Science Operations Department, E-28691 Villanueva de la Canada (Madrid) (Spain); Rea, Nanda, E-mail: jeroen@space.mit.edu [Institute of Space Sciences (CSIC-IEEC), Campus UAB, Faculty of Science, Torre C5-parell, E-08193 Barcelona (Spain)

    2013-09-20

    We present new Chandra X-ray observations of the transient black hole X-ray binary MAXI J1659-152 in quiescence. These observations were made more than one year after the end of the source's 2010-2011 outburst. We detect the source at a 0.5-10 keV flux of 2.8(8) Multiplication-Sign 10{sup -15} erg s{sup -1} cm{sup -2}, which corresponds to a luminosity of {approx}1.2 Multiplication-Sign 10{sup 31} (d/6 kpc){sup 2} erg s{sup -1}. This level, while being the lowest at which the source has been detected, is within factors of {approx}2 of the levels seen at the end of the initial decay of the outburst and soon after a major reflare of the source. The quiescent luminosity of MAXI J1659-152, which is the shortest-orbital-period black hole X-ray binary ({approx}2.4 hr), is lower than that of neutron-star X-ray binaries with similar periods. However, it is higher than the quiescent luminosities found for black hole X-ray binaries with orbital periods {approx}2-4 times longer. This could imply that a minimum quiescent luminosity may exist for black hole X-ray binaries, around orbital periods of {approx}5-10 hr, as predicted by binary-evolution models for the mass transfer rate. Compared to the hard state, we see a clear softening of the power-law spectrum in quiescence, from an index of 1.55(4) to an index of 2.5(4). We constrain the luminosity range in which this softening starts to (0.18-6.2) Multiplication-Sign 10{sup -5} (d/6 kpc){sup 2} (M/8 M{sub Sun }) L{sub Edd}, which is consistent with the ranges inferred for other sources.

  8. THE NATURE AND FREQUENCY OF THE GAS OUTBURSTS IN COMET 67P/CHURYUMOV–GERASIMENKO OBSERVED BY THE ALICE FAR-ULTRAVIOLET SPECTROGRAPH ON ROSETTA

    Energy Technology Data Exchange (ETDEWEB)

    Feldman, Paul D. [Department of Physics and Astronomy, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218 (United States); A’Hearn, Michael F.; Feaga, Lori M. [Astronomy Department, University of Maryland, College Park, MD 20742 (United States); Bertaux, Jean-Loup [LATMOS, CNRS/UVSQ/IPSL, 11 Boulevard d’Alembert, F-78280 Guyancourt (France); Noonan, John; Parker, Joel Wm.; Schindhelm, Eric; Steffl, Andrew J.; Stern, S. Alan [Southwest Research Institute, Department of Space Studies, Suite 300, 1050 Walnut Street, Boulder, CO 80302 (United States); Weaver, Harold A., E-mail: pfeldman@jhu.edu [Space Exploration Sector, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723-6099 (United States)

    2016-07-01

    ALICE is a far-ultraviolet imaging spectrograph on board Rosetta that, among multiple objectives, is designed to observe emissions from various atomic and molecular species from within the coma of comet 67P/Churyumov–Gerasimenko. The initial observations, made following orbit insertion in 2014 August, showed emissions of atomic hydrogen and oxygen spatially localized close to the nucleus and attributed to photoelectron impact dissociation of H{sub 2}O vapor. Weaker emissions from atomic carbon were subsequently detected and also attributed to electron impact dissociation, of CO{sub 2}, the relative H i and C i line intensities reflecting the variation of CO{sub 2} to H{sub 2}O column abundance along the line of sight through the coma. Beginning in 2015 mid-April, Alice sporadically observed a number of outbursts above the sunward limb characterized by sudden increases in the atomic emissions, particularly the semi-forbidden O i λ 1356 multiplet, over a period of 10–30 minutes, without a corresponding enhancement in long-wavelength solar reflected light characteristic of dust production. A large increase in the brightness ratio O i λ 1356/O i λ 1304 suggests O{sub 2} as the principal source of the additional gas. These outbursts do not correlate with any of the visible images of outbursts taken with either OSIRIS or the navigation camera. Beginning in 2015 June the nature of the Alice spectrum changed considerably with CO Fourth Positive band emission observed continuously, varying with pointing but otherwise fairly constant in time. However, CO does not appear to be a major driver of any of the observed outbursts.

  9. Prediction, prevention and fight automatic control in mining an outburst prone coal seam; Control Automatico de las Medidas de Prediccion, Prevencion y Lucha, para la Explotacion Mecanizada de una Capa Susceptible de desprendimientos Instantaneos

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-07-01

    Outburst are instantaneous catastrophic failure of the coal mine structure, characterised by emissions of large quantities of finely divided coal dust and gas from a coal face. In Spain, outbursts have represented a serious problem in the zone of Aller (Asturias), particularly in San Antonio mine. The main objective of the research work was to determine whether outburst precursory micro seismic activity could be discerned by monitoring the coal mining district of San Antonio. Micro seismic activity on the underground seismometer contains distinct style of events: natural events, stress events and outburst events. The correlation between the rate of extraction and the number of micro seismic activity has been analysed. A real time software was developed which would discriminate mining activity from background seismic noise. the algorithm used for event detection in based on comparing the short term average (STA) with the long term average (LTA) of the signal energy. (Author)

  10. The transient radiation effects and hardness of programmed device

    International Nuclear Information System (INIS)

    Du Chuanhua; Xu Xianguo; Zhao Hailin

    2014-01-01

    A review and summary of research and development in the investigation of transient ionizing radiation effects in device and cirviut is presented. The transient ionizing radiation effects in two type of programmed device, that's 32 bit Microcontroller and antifuse FPGA, were studied. The expeiment test data indicate: The transient ionizing radiation effects of 32 bit Microcontroller manifested self-motion restart and Latchup, the Latchup threshold was 5 × 10"7 Gy (Si)/s. The transient ionizing radiation effects of FPGA was reset, no Latchup. The relationship of circuit effects to physical mechanisms was analized. A new method of hardness in circiut design was put forward. (authors)

  11. XMM-Newton Spectroscopy of the Accretion-driven Millisecond X-Ray Pulsar XTE J1751-305 in Outburst

    NARCIS (Netherlands)

    Miller, J. M.; Wijnands, R.; Méndez, M.; Kendziorra, E.; Tiengo, A.; van der Klis, M.; Chakrabarty, D.; Gaensler, B. M.; Lewin, W. H. G.

    2003-01-01

    We present an analysis of the first high-resolution spectra measured from an accretion-driven millisecond X-ray pulsar in outburst. We observed XTE J1751-305 with XMM-Newton on 2002 April 7 for approximately 35 ks. Using a simple absorbed blackbody plus power-law model, we measure an unabsorbed flux

  12. Possibility of employing of radon emission and migration to forecast of sudden outburst

    International Nuclear Information System (INIS)

    Lebecka, J.; Lebecki, K.; Kobiela, Z.; Mnich, K.

    1991-01-01

    Presented paper is continuation of previous work published on the Conference in Beijing, 1987. During two years observations of changes in radon concentration have been extended to different workings, including sandstone. The radon emission from long drainage boreholes was measured, and the results have been used for the estimation of degasification of boreholes impact. The most essential result is the real possibility to use this phenomenon, that is the changes in radon emission, to forecast outbursts in coal seams and as a means of warning in sandstones

  13. Swift observations of SDSS J141118.31+481257.6 during its first detected outburst

    Science.gov (United States)

    Sandoval, L. E. Rivera; Maccarone, T.

    2018-05-01

    We report Swift observations of the AM CVn-type system SDSS J141118.31+481257.6 (RA=14:11:18.31, Dec=+48:12:57.6) during its first ever recorded outburst. The system was detected by Tadashi Kojima on 2018-May-20 with a V magnitude of 12.6 +- 0.2 (http://ooruri.kusastro.kyoto-u.ac.jp/mailarchive/vsnet-alert/22176), an increase of 7 mags compared to any previous measurement in the same filter.

  14. Connections Between Jet Formation and Multiwavelength Spectral Evolution in Black Hole Transients

    Science.gov (United States)

    Kakemci, Emrah; Chun, Yoon-Young; Dincer, Tolga; Buxton, Michelle; Tomsick, John A.; Corbel, Stephane; Kaaret, Philip

    2011-01-01

    Multiwavelength observations are the key to understand conditions of jet formation in Galactic black hole transient (GBHT) systems. By studying radio and optical-infrared evolution of such systems during outburst decays, the compact jet formation can be traced. Comparing this with X-ray spectral and timing evolution we can obtain physical and geometrical conditions for jet formation, and study the contribution of jets to X-ray emission. In this work, first X-ray evolution - jet relation for XTE J1752-223 will be discussed. This source had very good coverage in X-rays, optical, infrared and radio. A long exposure with INTEGRAL also allowed us to study gamma-ray behavior after the jet turns on. We will also show results from the analysis of data from GX 339-4 in the hard state with SUZAKU at low flux levels. The fits to iron line fluorescence emission show that the inner disk radius increases by a factor of greater than 27 with respect to radii in bright states. This result, along with other disk radius measurements in the hard state will be discussed within the context of conditions for launching and sustaining jets.

  15. The X-ray spectra of the black hole candidate 4U 1630-47 during its 2012 outburst

    NARCIS (Netherlands)

    Wang, Y.; Mendez, M.

    2015-01-01

    Diaz Trigo et al. (2013) reported the detection of three Doppler-shifted emission lines arising from baryonic matter in the jet of 4U 1630-47 during its 2012 outburst. Here we propose an alternative model that, without the need of the lines from the jet, and with less free parameters, fits the same

  16. Analytical Assessment for Transient Stability Under Stochastic Continuous Disturbances

    Energy Technology Data Exchange (ETDEWEB)

    Ju, Ping [Hohai Univ., Nanjing (China); Li, Hongyu [Hohai Univ., Nanjing (China); Gan, Chun [The Univ. of Tennessee, Knoxville, TN (United States); Liu, Yong [The Univ. of Tennessee, Knoxville, TN (United States); Yu, Yiping [Hohai Univ., Nanjing (China); Liu, Yilu [Univ. of Tennessee, Knoxville, TN (United States)

    2017-06-28

    Here, with the growing integration of renewable power generation, plug-in electric vehicles, and other sources of uncertainty, increasing stochastic continuous disturbances are brought to power systems. The impact of stochastic continuous disturbances on power system transient stability attracts significant attention. To address this problem, this paper proposes an analytical assessment method for transient stability of multi-machine power systems under stochastic continuous disturbances. In the proposed method, a probability measure of transient stability is presented and analytically solved by stochastic averaging. Compared with the conventional method (Monte Carlo simulation), the proposed method is many orders of magnitude faster, which makes it very attractive in practice when many plans for transient stability must be compared or when transient stability must be analyzed quickly. Also, it is found that the evolution of system energy over time is almost a simple diffusion process by the proposed method, which explains the impact mechanism of stochastic continuous disturbances on transient stability in theory.

  17. DETECTION OF VERY LOW-FREQUENCY, QUASI-PERIODIC OSCILLATIONS IN THE 2015 OUTBURST OF V404 CYGNI

    Energy Technology Data Exchange (ETDEWEB)

    Huppenkothen, D. [Center for Data Science, New York University, 726 Broadway, 7th Floor, New York, NY 10003 (United States); Younes, G.; Kouveliotou, C. [Department of Physics, The George Washington University, Washington, DC 20052 (United States); Ingram, A.; Van der Klis, M. [Anton Pannekoek Institute, University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Göğüş, E. [Sabancı University, Orhanlı-Tuzla, İstanbul 34956 (Turkey); Bachetti, M. [INAF/Osservatorio Astronomico di Cagliari, via della Scienza 5, I-09047 Selargius (Italy); Sánchez-Fernández, C.; Kuulkers, E. [European Space Astronomy Centre (ESA/ESAC), Science Operations Department, E-28691 Villanueva de la Cañada, Madrid (Spain); Chenevez, J. [DTU Space—National Space Institute, Technical University of Denmark, Elektrovej 327-328, DK-2800 Lyngby (Denmark); Motta, S. [University of Oxford, Department of Physics, Astrophysics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Granot, J. [Department of Natural Sciences, The Open University of Israel, 1 University Road, P.O. Box 808, Raanana 43537 (Israel); Gehrels, N. [Astrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771 (United States); Tomsick, J. A. [Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450 (United States); Walton, D. J., E-mail: daniela.huppenkothen@nyu.edu [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States)

    2017-01-01

    In 2015 June, the black hole X-ray binary (BHXRB) V404 Cygni went into outburst for the first time since 1989. Here, we present a comprehensive search for quasi-periodic oscillations (QPOs) of V404 Cygni during its recent outburst, utilizing data from six instruments on board five different X-ray missions: Swift /XRT, Fermi /GBM, Chandra /ACIS, INTEGRAL ’s IBIS/ISGRI and JEM-X, and NuSTAR . We report the detection of a QPO at 18 mHz simultaneously with both Fermi /GBM and Swift /XRT, another example of a rare but slowly growing new class of mHz-QPOs in BHXRBs linked to sources with a high orbital inclination. Additionally, we find a duo of QPOs in a Chandra /ACIS observation at 73 mHz and 1.03 Hz, as well as a QPO at 136 mHz in a single Swift /XRT observation that can be interpreted as standard Type-C QPOs. Aside from the detected QPOs, there is significant structure in the broadband power, with a strong feature observable in the Chandra observations between 0.1 and 1 Hz. We discuss our results in the context of current models for QPO formation.

  18. All-Union Congress on the problem of dealing with sudden outbursts of coal, rock and gas

    Energy Technology Data Exchange (ETDEWEB)

    1983-05-01

    In recent years several measures have been taken to prevent the occurrence of outbursts, involving research, special training and new technology. In the 10th 5 year plan period the number of outbursts and associated injuries fell by 1.7 times, but in recent years the rate has started to increase again (52 in 1982). The reasons for this were chiefly slack discipline and the inadequacy of forecasting techniques. The slow progress of research and the introduction of new equipment is criticized. Not enough gassy mines are worked by the pillar system, and stowing of the goaf is still the exception. Automation of plows, narrow-web cutter loaders, heading machines, drills and supports is continuing, as is the introduction of radio control, loudspeaker warning systems, intrinsically safe power sources, etc. The M87 DGA remote control support has been working in a Donbass mine for 3 years with no reports of injuries during this period. LIRA and IKAR radio control systems and control panels connected by cables are in use with cutter loaders allowing operating personnel to remain at a safe distance from danger zones. A list of papers and reports delivered at the Congress is given.

  19. MAXI/GSC detection of a new outburst from SAX J1810.8-2609

    Science.gov (United States)

    Negoro, H.; Mihara, T.; Nakahira, S.; Yatabe, F.; Takao, Y.; Matsuoka, M.; Kawai, N.; Sugizaki, M.; Tachibana, Y.; Morita, K.; Sakamoto, T.; Serino, M.; Sugita, S.; Kawakubo, Y.; Hashimoto, T.; Yoshida, A.; Nakajima, M.; Sakamaki, A.; Maruyama, W.; Ueno, S.; Tomida, H.; Ishikawa, M.; Sugawara, Y.; Isobe, N.; Shimomukai, R.; Ueda, Y.; Tanimoto, A.; Morita, T.; Yamada, S.; Tsuboi, Y.; Iwakiri, W.; Sasaki, R.; Kawai, H.; Sato, T.; Tsunemi, H.; Yoneyama, T.; Yamauchi, M.; Hidaka, K.; Iwahori, S.; Kawamuro, T.; Yamaoka, K.; Shidatsu, M.

    2018-05-01

    We report a new X-ray outburst from the low-mass X-ray binary SAX J1810.8-2609 (aka V4722 Sgr; Ubertini et al. 1998, IAUC 6838) observed with MAXI/GSC. The enhancement was recognized from 2018 April 23 (MJD 58231), and X-ray count rates in the 2-4 keV and 4-10 keV bands peaked on April 26 at 0.085 +/- 0.008 c/s/cm2 ( 80 mCrab) and 0.096+/-0.008 c/s/cm2 ( 82 mCrab), respectively.

  20. An X-ray outburst from the rapidly accreting young star that illuminates McNeil's nebula.

    Science.gov (United States)

    Kastner, J H; Richmond, M; Grosso, N; Weintraub, D A; Simon, T; Frank, A; Hamaguchi, K; Ozawa, H; Henden, A

    2004-07-22

    Young, low-mass stars are luminous X-ray sources whose powerful X-ray flares may exert a profound influence over the process of planet formation. The origin of the X-ray emission is uncertain. Although many (or perhaps most) recently formed, low-mass stars emit X-rays as a consequence of solar-like coronal activity, it has also been suggested that X-ray emission may be a direct result of mass accretion onto the forming star. Here we report X-ray imaging spectroscopy observations which reveal a factor approximately 50 increase in the X-ray flux from a young star that is at present undergoing a spectacular optical/infrared outburst (this star illuminates McNeil's nebula). The outburst seems to be due to the sudden onset of a phase of rapid accretion. The coincidence of a surge in X-ray brightness with the optical/infrared eruption demonstrates that strongly enhanced high-energy emission from young stars can occur as a consequence of high accretion rates. We suggest that such accretion-enhanced X-ray emission from erupting young stars may be short-lived, because intense star-disk magnetospheric interactions are quenched rapidly by the subsequent flood of new material onto the star.

  1. 缓倾斜严重突出煤层快速揭煤优化研究%Research on Optimization of Fast Exposing Gently-inclined Serious Outburst Coal Seam by a Crosscut

    Institute of Scientific and Technical Information of China (English)

    王建; 张荻; 李正刚

    2015-01-01

    为了提高缓倾斜严重突出煤层的揭煤效率,采用缩短揭煤巷道距离、水力压裂增透结合底板穿层钻孔预抽的方法,优化揭煤步骤. 现场应用表明,该方法可以减少2次区域验证次数,减少施工9~24个钻孔,揭煤时间平均缩短5. 0~15. 4 d,费用减少50%,实现了安全快速石门揭煤.%In order to improve the efficiency of exposing the gently-inclined serious outburst coal seam by a crosscut, the steps of exposing the outburst coal seam by a crosscut were optimized by adopting the measures of shortening the distance of the roadway exposing the outburst coal seam, gas permeability enhancement by hydraulic fracturing and gas pre-drainage by floor crossing holes. The site application showed that this method can reduce two regional verifications, reduce the drilling construction of 9~24 holes, the average time for exposing the outburst coal seam was shortened by 5. 0~15. 4 d and the costs were reduced by 50%, as a result, the fast exposing outburst coal seam by a crosscut was realized.

  2. Nova outburst modeling and its application to the recurrent nova phenomenon

    International Nuclear Information System (INIS)

    Sparks, W.M.; Starrfield, S.; Truran, J.

    1985-12-01

    The thermonuclear runaway (TNR) theory for the cause of the common novae is reviewed. Numerical simulations of this theory were performed using an implicit hydrodynamic Lagrangian computer code. Relevant physical phenomena are explained with the simpler envelope-in-place calculations. Next the models that include accretion are discussed. The calculations agree very well with observations of common novae. The observational differences between common novae and recurrent novae are examined. We propose input parameters to the TNR model which can give the outburst characteristics of RS Ophiuchi and discuss the implications. This review is concluded with a brief discussion of two current topics in novae research: shear mixing on the white dwarf and Neon novae. 36 refs., 4 figs

  3. Disc structure and variability in dwarf novae

    Science.gov (United States)

    Harlaftis, Emilios Theofanus

    An introduction is given to dwarf novae reviewing the current research status in the field. We present IUE observations of Z Cha which support the mass transfer instability as the cause of the superoutbursts observed in SU UMa type dwarf novae. Comparison between the superoutburst and a normal outburst of Z Cha shows that the disc is flatter and has significantly less azimuthal structure than during superoutburst. Z Cha exhibits a soft x-ray deficit during superoutburst compared to OY Car. We find that the secondary star of Z Cha contributes approximately 30 percent of the infrared flux at peak of outburst. The second part of the thesis presents results from the 1988 International Time Project at the Observatorio del Roque de los Muchachos. Investigation of the behavior of SU UMa and YZ Cnc is carried out through the outburst cycle. The secular changes of the equivalent widths of both systems shows an increasing trend even during quiescence and are caused by the continuum decrease. Both systems show a low-velocity emission component which contaminates the wings of the H(alpha) profile. In addition to doppler broadening, the Stark effect is found to cause significant broadening to the line profile. The radial dependence of the emission lines is discussed in relation to other cataclysmic variables. H(alpha) emission from the secondary star of YZ Cnc is found during superoutburst, during outburst and during quiescence after outburst. Photometry during late decline of outburst shows a sinusoidal, weak variation peaking at 0.5 orbital phase and which is related to heating of the red star or to a transient disc event. During quiescence, the flickering is found to be caused by the bright spot. This modulation increases with time and is maximum before the outburst. Doppler tomography of IP Peg during quiescence reveals an emission line distribution not consistent to the standard model. We find Balmer emission from the secondary star, at a level of only 2.5 percent of the

  4. Mechanism of transient force augmentation varying with two distinct timescales for interacting vortex rings

    Science.gov (United States)

    Fu, Zhidong; Qin, Suyang; Liu, Hong

    2014-01-01

    The dynamics of dual vortex ring flows is studied experimentally and numerically in a model system that consists of a piston-cylinder apparatus. The flows are generated by double identical strokes which have the velocity profile characterized by the sinusoidal function of half the period. By calculating the total wake impulse in two strokes in the experiments, it is found that the average propulsive force increases by 50% in the second stroke for the sufficiently small stroke length, compared with the first stroke. In the numerical simulations, two types of transient force augmentation are revealed, there being the transient force augmentation for the small stroke lengths and the absolute transient force augmentation for the large stroke lengths. The relative transient force augmentation increases to 78% for L/D = 1, while the absolute transient force augmentation for L/D = 4 is twice as much as that for L/D = 1. Further investigation demonstrates that the force augmentation is attributed to the interaction between vortex rings, which induces transport of vortex impulse and more evident fluid entrainment. The critical situation of vortex ring separation is defined and indicated, with vortex spacing falling in a narrow gap when the stroke lengths vary. A new model is proposed concerning the limiting process of impulse, further suggesting that apart from vortex formation timescale, vortex spacing should be interpreted as an independent timescale to reflect the dynamics of vortex interaction.

  5. Multi-wavelength observations of novae in outburst

    International Nuclear Information System (INIS)

    Starrfield, S.; Arizona State Univ., Tempe, AZ

    1989-01-01

    This review serves as the introduction to the observational studies of novae and I will mention a number of results that will be emphasized by other reviewers. Therefore, I will try to provide the physical framework for multi-wavelength observations as applied to studies of novae. I divide the outburst into phases based on the physical effects that are occurring at that time. The first phase is the rise to bolometric maximum and occurs on a convective time scale. The second phase is the rise to visual maximum and occurs on the time scale for the envelope to expand to ∼10 12 cm. The third phase is the time when the nova is emitting at constant bolometric luminosity, but declining optical magnitude, and it lasts until most of the accreted material has been either exhausted or eroded from the surface of the white dwarf. The fourth and final phase is the return is the return to quiescence (turn-off phase) and it occurs at the time that nuclear burning is ending. I will discuss each of these phases in turn and end with a discussion. 36 refs

  6. Flickering of the symbiotic variable CH Cygni during outburst

    Energy Technology Data Exchange (ETDEWEB)

    Slovak, M H [Texas Univ., Austin (USA). Dept. of Astronomy; Africano, J

    1978-11-01

    High-speed and conventional BVRI photometry are reported for the bright symbiotic variable CH Cygni (M6 IIIe), obtained during the course of a recent outburst. Unlike the quiescent symbiotic stars, the presence of flickering similar in nature to that seen in the cataclysmic variables has been confirmed during this active phase. The BVRI photometry for a sample of stars in the field is used to derive the reddening and the distance to CH Cyg. A composite energy distribution is derived from 0.35 to 11.0 ..mu..m which clearly establishes the existence of a variable, blue continuum. The lack of variability in the near infrared suggests that the blue continuum arises from a hot companion. A binary model including a subluminous hot companion accreting material from the stellar wind of an SRa variable is discussed to account for the observed photometric properties.

  7. Nucleosynthesis and the nova outburst

    International Nuclear Information System (INIS)

    Starrfield, S.

    1995-01-01

    A nova outburst is the consequence of the accretion of hydrogen rich material onto a white dwarf and it can be considered as the largest hydrogen bomb in the Universe. The fuel is supplied by a secondary star in a close binary system while the strong degeneracy of the massive white dwarf acts to contain the gas during the early stages of the explosion. The containment allows the temperature in the nuclear burning region to exceed 10 8 K under all circumstances. As a result a major fraction of CNO nuclei in the envelope are transformed into β + -unstable nuclei. We discuss the effects of these nuclei on the evolution. Recent observational studies have shown that there are two compositional classes of novae; one which occurs on carbon-oxygen white dwarfs, and a second class that occurs on oxygen-neon-magnesium white dwarfs. In this review we will concentrate on the latter explosions since they produce the most interesting nucleosynthesis. We report both on the results of new observational determinations of nova abundances and, in addition, new hydrodynamic calculations that examine the consequences of the accretion process on 1.0M circle-dot , 1.25M circle-dot , and 1.35M circle-dot white dwarfs. Our results show that novae can produce 22 Na, 26 Al, and other intermediate mass nuclei in interesting amounts. We will present the results of new calculations, done with updated nuclear reaction rates and opacities, which exhibit quantitative differences with respect to published work

  8. Polymers for combatting sudden outbursts in coal mines

    Energy Technology Data Exchange (ETDEWEB)

    Gadzhiev, G P; Sukhanov, V V

    1988-02-01

    Describes investigations in coal mines in the Donetsk basin (hazardous because of the high methane presence, the risk of outbursts of coal and gas, underground fires and the high dust levels) with the aim of studying the toxic emissions of formaldehyde and methanol produced when a urea formaldehyde resin binder is applied to the coal seam. The measurements taken led to the following recommendations: the amount of free formaldehyde in the binder should be limited to 0.5%; the use of concentrated (50%) solutions should be limited to 10 l per ton of coal in areas where there are geologic faults; underground workings need ventilation of at least 200 m/sup 3//min; the binder should be introduced to the borehole separately from the water and hardener; individual protection measures and wet dusting should be used during coal extraction; a period of not less than 4 months should elapse between application of the resin and commencement of coal extraction; there should be at least 80 m between the point where the binder is applied and the coal face.

  9. Tramadol Overdose Induced Transient Paresthesia and Decreased Muscle Strength: A Case Series

    Directory of Open Access Journals (Sweden)

    Khosrow Ghasempouri

    2014-06-01

    Conclusion: Transient paresthesia and transient symmetrical decline in muscle strength of upper and lower limbs are potential neurologic complications following tramadol abuse and overdose. Further studies are needed to fully clarify the pathogenesis and mechanism of these complications following tramadol overdose.

  10. THE TRANSIENT ACCRETING X-RAY PULSAR XTE J1946+274: STABILITY OF X-RAY PROPERTIES AT LOW FLUX AND UPDATED ORBITAL SOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    Marcu-Cheatham, Diana M.; Pottschmidt, Katja [CRESST and Department of Physics, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250 (United States); Kühnel, Matthias; Müller, Sebastian; Falkner, Sebastian; Kreykenbohm, Ingo [Dr. Karl Remeis-Observatory and ECAP, University Erlangen-Nuremberg, Sternwartstr. 7, Bamberg (Germany); Caballero, Isabel [Laboratoire AIM, CEA/IRFU, CNRS/INSU, Université Paris Diderot, CEA DSM/IRFU/SAp, F-91191 Gif-sur-Yvette (France); Finger, Mark H. [Universities Space Research Association, National Space Science and Technology Center, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Jenke, Peter J. [University of Alabama in Huntsville, 301 Sparkman Drive, Huntsville, AL 35899 (United States); Wilson-Hodge, Colleen A. [Astrophysics Office, ZP 12, NASA Marshall Space Flight Center, Huntsville, AL 35812 (United States); Fürst, Felix [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Grinberg, Victoria [Massachusetts Institute of Technology, Kavli Institute for Astrophysics, Cambridge, MA 02139 (United States); Hemphill, Paul B.; Rothschild, Richard E. [University of California, San Diego, Center for Astrophysics and Space Sciences, 9500 Gilman Drive, La Jolla, CA 92093-0424 (United States); Klochkov, Dmitry [Institut für Astronomie und Astrophysik, Universität Tübingen (IAAT), Sand 1, Tübingen (Germany); Terada, Yukikatsu [Graduate School of Science and Engineering, Saitama University, 255 Simo-Ohkubo, Sakura-ku, Saitama City, Saitama 338-8570 (Japan); and others

    2015-12-10

    We present a timing and spectral analysis of the X-ray pulsar XTE J1946+274 observed with Suzaku during an outburst decline in 2010 October and compare with previous results. XTE J1946+274 is a transient X-ray binary consisting of a Be-type star and a neutron star with a 15.75 s pulse period in a 172 days orbit with 2–3 outbursts per orbit during phases of activity. We improve the orbital solution using data from multiple instruments. The X-ray spectrum can be described by an absorbed Fermi–Dirac cut-off power-law model along with a narrow Fe Kα line at 6.4 keV and a weak Cyclotron Resonance Scattering Feature (CRSF) at ∼35 keV. The Suzaku data are consistent with the previously observed continuum flux versus iron line flux correlation expected from fluorescence emission along the line of sight. However, the observed iron line flux is slightly higher, indicating the possibility of a higher iron abundance or the presence of non-uniform material. We argue that the source most likely has only been observed in the subcritical (non-radiation dominated) state since its pulse profile is stable over all observed luminosities and the energy of the CRSF is approximately the same at the highest (∼5 × 10{sup 37} erg s{sup −1}) and lowest (∼5 × 10{sup 36} erg s{sup −1}) observed 3–60 keV luminosities.

  11. Seismic Monitoring and Characterization of the 2012 Outburst Flood of the Ice-Dammed Lake A.P.Olsen (NE Greenland)

    Science.gov (United States)

    Behm, M.; Walter, J. I.; Binder, D.; Mertl, S.

    2017-12-01

    Since the Zackenberg Research Station (ZRS) in NE-Greenland was established in 1995, regular floods of the adjacent Zackenberg River have been observed. The floods result from the sudden discharge of a marginal, ice-dammed lake at the pre-dominantly cold-based A.P. Olsen Ice Cap about 35 km inland. The lake filling usually starts with the melting season in May/June and ends with the flood sometime after early July. The run-off water from the lake discharges through the subsurface of the adjacent Argo glacier. The actual migration paths and depth of the water within the glacier are unknown until it re-appears at the glacier terminus at a distance of 4 km to the ice-dam. In spring 2012 a surface seismic monitoring network was installed on Argo glacier in 2-3 m boreholes near the lake to acquire continuous data for the whole fill- and drain cycle from start of May to end of November. The network comprises 3 stations with three-component sensors and 2 stations designed as tripartite arrays with vertically oriented sensors. The maximum interstation distance is 1.2 km. Microseismic event detection and localization is facilitated by the homogenous seismic structure of the ice and the extremely high S/N ratio of the borehole installations. An initial detection based on an STA/LTA algorithm and event assocator results in order-of-magnitude 100,000 seismic events. These events are generally attributed to the opening of surface crevasses due to the presence of weak body waves and strong surface wave energy, interpreted to be Rayleigh waves with dominant frequencies around 1-4 Hz. Time-lapse cross-correlations of the ambient seismic noise field reconstruct the surface waves travelling between the stations. Weekly stacks of the cross-correlations are stable, and show a distinct change correlated with the outburst flood. Apparent surface wave velocities increase slightly several weeks prior to the outburst event, which itself is characterized by a decrease in the correlation

  12. Mechanisms for the control of two-mode transient stimulated Raman scattering in liquids

    International Nuclear Information System (INIS)

    Spanner, Michael; Brumer, Paul

    2006-01-01

    Recent adaptive feedback control experiments demonstrated control of transient (i.e. nonimpulsive) Stokes emission from two closely spaced Raman-active modes in liquid methanol [e.g., B. J. Pearson et al., Phys. Rev. A 63, 063412 (2001)]. Optimally shaped pulses were found that selectively excited one of the two Stokes lines alone, optimized emission from both modes together, or completely suppressed all Stokes emission. Here, two general control mechanisms capable of affecting the ratio of intensities of the Stokes lines are identified. The first is operational when the duration of the pump pulse (t p ) is on the order of the collisional dephasing time (t d ). The ratio of the peak heights of the two Stokes lines can then be controlled by simply varying the duration and/or intensity of the pump pulse. The second operates when 1/t p is on the order of the energy separation of the two Raman modes, and hence when the two Raman modes are coupled due to overlapping nonlinear polarizations that drive the stimulated Raman scattering. In this regime, asymmetry in the spectral amplitudes within the pump pulse can control the asymmetry in the peak heights of the Stokes emission. Both these mechanisms have the same clear physical interpretation: shaping the pump pulse controls the nonlinear optical response of the medium, which in turn controls the stimulated Stokes emission, itself a χ (3) nonlinear effect. In neither mechanism does the ratio of peak heights in the Stokes spectrum reflect directly the ratio of excited-state populations associated with the two Raman modes, as was assumed in the experiments, nor does the control involve coherent quantum interference effects

  13. Comparison of LIFE-4 and TEMECH code predictions with TREAT transient test data

    International Nuclear Information System (INIS)

    Gneiting, B.C.; Bard, F.E.; Hunter, C.W.

    1984-09-01

    Transient tests in the TREAT reactor were performed on FFTF Reference design mixed-oxide fuel pins, most of which had received prior steady-state irradiation in the EBR-II reactor. These transient test results provide a data base for calibration and verification of fuel performance codes and for evaluation of processes that affect pin damage during transient events. This paper presents a comparison of the LIFE-4 and TEMECH fuel pin thermal/mechanical analysis codes with the results from 20 HEDL TREAT experiments, ten of which resulted in pin failure. Both the LIFE-4 and TEMECH codes provided an adequate representation of the thermal and mechanical data from the TREAT experiments. Also, a criterion for 50% probability of pin failure was developed for each code using an average cumulative damage fraction value calculated for the pins that failed. Both codes employ the two major cladding loading mechanisms of differential thermal expansion and central cavity pressurization which were demonstrated by the test results. However, a detailed evaluation of the code predictions shows that the two code systems weigh the loading mechanism differently to reach the same end points of the TREAT transient results

  14. Influence of Base Oil Polarity on the Transient Shear Flow of Biodegradable Lubricating Greases

    Directory of Open Access Journals (Sweden)

    Martin Fiedler

    2015-09-01

    Full Text Available The scope of this study is to elucidate the physical mechanisms influencing the transient flow behavior of lubricating greases based on biogenic oleochemicals from a polarity point of view. This includes the mutually interacting influence of base oil polarity and thickening agents on the rheologically-measured mechanical structural degradation in transient shear flow. Due to the high temperature dependence of Keesom forces in the background of polar-active bond mechanisms, the analysis of the transient flow response as a function of temperature allows to attribute the observed influences to differences in base oil polarity. In general, clay-thickened greases show a greater tendency to be rheologically influenced by base oil polarities than soap-thickened lubricating greases.

  15. Nonlinear Diffusion and Transient Osmosis

    International Nuclear Information System (INIS)

    Igarashi, Akira; Rondoni, Lamberto; Botrugno, Antonio; Pizzi, Marco

    2011-01-01

    We investigate both analytically and numerically the concentration dynamics of a solution in two containers connected by a narrow and short channel, in which diffusion obeys a porous medium equation. We also consider the variation of the pressure in the containers due to the flow of matter in the channel. In particular, we identify a phenomenon, which depends on the transport of matter across nano-porous membranes, which we call ''transient osmosis . We find that nonlinear diffusion of the porous medium equation type allows numerous different osmotic-like phenomena, which are not present in the case of ordinary Fickian diffusion. Experimental results suggest one possible candidate for transiently osmotic processes. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  16. HIGH-RESOLUTION INFRARED IMAGING AND SPECTROSCOPY OF THE Z CANIS MAJORIS SYSTEM DURING QUIESCENCE AND OUTBURST

    Energy Technology Data Exchange (ETDEWEB)

    Hinkley, Sasha; Hillenbrand, Lynne; Crepp, Justin R. [Department of Astronomy, California Institute of Technology, 1200 E. California Blvd, MC 249-17, Pasadena, CA 91125 (United States); Oppenheimer, Ben R.; Zimmerman, Neil; Brenner, Douglas [Astrophysics Department, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024 (United States); Rice, Emily L. [Department of Engineering Science and Physics, College of Staten Island, City University of New York, 2800 Victory Bvld, Staten Island, NY 10314 (United States); Pueyo, Laurent [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Vasisht, Gautam; Roberts, Jennifer E.; Roberts, Lewis C. Jr.; Burruss, Rick; Wallace, J. Kent; Cady, Eric; Zhai, Chengxing [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109 (United States); Kraus, Adam L. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, 02138 (United States); Ireland, Michael J. [Department of Physics and Astronomy, Macquarie University, New South Wales, NSW 2109 (Australia); Beichman, Charles [NASA Exoplanet Science Institute, California Institute of Technology, Pasadena, CA 91125 (United States); Dekany, Richard [Caltech Optical Observatories, California Institute of Technology, Pasadena, CA 91125 (United States); Parry, Ian R. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); and others

    2013-01-20

    We present adaptive optics photometry and spectra in the JHKL bands along with high spectral resolution K-band spectroscopy for each component of the Z Canis Majoris system. Our high angular resolution photometry of this very young ({approx}<1 Myr) binary, comprised of an FU Ori object and a Herbig Ae/Be star, was gathered shortly after the 2008 outburst while our high-resolution spectroscopy was gathered during a quiescent phase. Our photometry conclusively determines that the outburst was due solely to the embedded Herbig Ae/Be member, supporting results from earlier works, and that the optically visible FU Ori component decreased slightly ({approx}30%) in luminosity during the same period, consistent with previous works on the variability of FU Ori type systems. Further, our high-resolution K-band spectra definitively demonstrate that the 2.294 {mu}m CO absorption feature seen in composite spectra of the system is due solely to the FU Ori component, while a prominent CO emission feature at the same wavelength, long suspected to be associated with the innermost regions of a circumstellar accretion disk, can be assigned to the Herbig Ae/Be member. These findings clarify previous analyses of the origin of the CO emission in this complex system.

  17. Assessment of glacial lake development and prospects of outburst susceptibility: Chamlang South Glacier, eastern Nepal Himalaya

    Directory of Open Access Journals (Sweden)

    Damodar Lamsal

    2016-01-01

    Full Text Available Chamlang South Tsho has been identified as one of the six high-priority glacial lakes in terms of glacial lake outburst flood (GLOF danger in Nepal Himalaya, despite the fact that no detailed investigations of the lake had been hitherto undertaken. We conducted detailed mapping of the lake and its surroundings along with field surveys in October 2009 to determine the developmental history of Chamlang South Tsho and to assess its potential for GLOF. The lake expanded rapidly between 1964 (0.04 km2 and 2000 (0.86 km2 and has been stable ever since. Future lake expansion is improbable as its sides are confined by relatively stable landforms. The lake is 87-m deep with a water volume of approximately 34.9–35.6 × 106 m3. Hanging glaciers on the steep surrounding mountain slopes and prominent seepage water in the terminal moraine dam could be potential triggers for a future outburst flood. Additionally, the debris-covered dead-ice dam, which is higher than the lake water level, is narrow and low; therefore, it could be overtopped easily by surge waves. Furthermore, the pronounced difference in elevation between the lake and the base of the terminal moraine dam makes the lake susceptible for a large flood.

  18. Dramatic change of the recurrence time and outburst parameters of the intermediate polar GK Persei

    Science.gov (United States)

    Šimon, V.

    2002-02-01

    This analysis has shown that the intermediate polar GK Per experienced a very striking evolution. Its outbursts became wider and brighter in the last five decades. These changes were accompanied by striking variations of the recurrence time T_C, from 385 days within the years 1948-1967 to 890 days in 1970. Nowadays, T_C displays a strong trend of linear increase. Decrease of irradiation of the disk by the WD, combined with the decrease of viscosity, offers a plausible explanation. It is argued that variations of the mass transfer rate are unlikely to play a major role. The morphology of the outburst light curves in the optical and the X-ray region is also studied. The decay branch in the optical remains remarkably similar for all the events while the largest changes of the light curve occur in the rising branch. This can be explained if the thermal instability may start at different distances from the disk center. The quiescent level of brightness does not display any secular trend in recent decades but a wave on the time scale of about 30 years with the full amplitude of 0.3 m_v, probably due to activity of the cool star, is detected. This research has made use of the AFOEV database, operated at CDS, France, and the observations provided by the ASM/RXTE team.

  19. Concrete creep at transient temperature: constitutive law and mechanism

    International Nuclear Information System (INIS)

    Chern, J.C.; Bazant, Z.P.; Marchertas, A.H.

    1985-01-01

    A constitutive law which describes the transient thermal creep of concrete is presented. Moisture and temperature are two major parameters in this constitutive law. Aside from load, creep, cracking, and thermal (shrinkage) strains, stress-induced hygrothermal strains are also included in the analysis. The theory agrees with most types of test data which include basic creep, thermal expansion, shrinkage, swelling, creep at cyclic heating or drying, and creep at heating under compression or bending. Examples are given to demonstrate agreement between the theory and the experimental data. 15 refs., 6 figs

  20. Outbursts and diamagnetic cavities in comet 67P/Churyumov-Gerasimenko

    Science.gov (United States)

    Voelzke, M. R.

    2018-03-01

    On 2014 August 06 the Rosetta spacecraft arrived at comet 67P/Churyumov-Gerasimenko. Since then, the spacecraft accompanied the comet on its journey around the Sun (Glassmeier et al. 2007), until the end of the mission on 2016 September 30. This work tries to understand the possible connections between the 665 reported diamagnetic regions (Goetz et al. 2016), detected from April 2015 to February 2016 around the comet 67P/Churyumov-Gerasimenko, with the fluxgate magnetometer of the Rosetta Plasma Consortium (RPC-MAG), when the heliocentric distance of the comet from the sun varied from 1.8 to 2.4 AU and the 34 reported outbursts (Vincent et al. 2016), detected from July to September 2015, with the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) cameras, when the ESA's Rosetta spacecraft changed the cometocentric distance from 155 to 817 km.

  1. Landslides in moraines as triggers of glacial lake outburst floods: example from Palcacocha Lake (Cordillera Blanca, Peru)

    Czech Academy of Sciences Publication Activity Database

    Klimeš, Jan; Novotný, J.; Novotná, I.; Urries de, B.J.; Vilímek, V.; Emmer, Adam; Strozzi, T.; Kusák, Michal; Rapre, A.C.; Hartvich, Filip; Frey, H.

    2016-01-01

    Roč. 13, č. 6 (2016), s. 1461-1477 ISSN 1612-510X R&D Projects: GA ČR(CZ) GAP209/11/1000 Institutional support: RVO:67985891 ; RVO:67179843 Keywords : landslides * moraines * glacial lakes * slope stability calculation * glacial lake outburst floods * impact wave models * Cordillera Blanca Subject RIV: DE - Earth Magnetism, Geodesy, Geography; DE - Earth Magnetism, Geodesy, Geography (UEK-B) Impact factor: 3.657, year: 2016

  2. Transient selection in multicellular immune networks

    Science.gov (United States)

    Ivanchenko, M. V.

    2011-03-01

    We analyze the dynamics of a multi-clonotype naive T-cell population competing for survival signals from antigen-presenting cells. We find that this competition provides with an efficacious selection of clonotypes, making the less able and more repetitive get extinct. We uncover the scaling principles for large systems the extinction rate obeys and calibrate the model parameters to their experimental counterparts. For the first time, we estimate the physiological values of the T-cell receptor-antigen presentation profile recognition probability and T-cell clonotypes niche overlap. We demonstrate that, while the ultimate state is a stable fixed point, sequential transients dominate the dynamics over large timescales that may span over years, if not decades, in real time. We argue that what is currently viewed as "homeostasis" is a complex sequential transient process, while being quasi-stationary in the total number of T-cells only. The discovered type of sequential transient dynamics in large random networks is a novel alternative to the stable heteroclinic channel mechanism.

  3. Real-time transient stabilization and voltage regulation of power generators with unknown mechanical power input

    International Nuclear Information System (INIS)

    Kenne, Godpromesse; Goma, Raphael; Nkwawo, Homere; Lamnabhi-Lagarrigue, Francoise; Arzande, Amir; Vannier, Jean Claude

    2010-01-01

    A nonlinear adaptive excitation controller is proposed to enhance the transient stability and voltage regulation of synchronous generators with unknown power angle and mechanical power input. The proposed method is based on a standard third-order model of a synchronous generator which requires only information about the physical available measurements of relative angular speed, active electric power, infinite bus and generator terminal voltages. The operating conditions are computed online using the above physical available measurements, the terminal voltage reference value and the estimate of the mechanical power input. The proposed design is therefore capable of providing satisfactory voltage in the presence of unknown variations of the power system operating conditions. Using the concept of sliding mode equivalent control techniques, a robust decentralized adaptive controller which insures the exponential convergence of the outputs to the desired ones, is obtained. Real-time experimental results are reported, comparing the performance of the proposed adaptive nonlinear control scheme to one of the conventional AVR/PSS controller. The high simplicity of the overall adaptive control scheme and its robustness with respect to line impedance variation including critical unbalanced operating condition and temporary turbine fault, constitute the main positive features of the proposed approach.

  4. Real-time transient stabilization and voltage regulation of power generators with unknown mechanical power input

    Energy Technology Data Exchange (ETDEWEB)

    Kenne, Godpromesse, E-mail: gokenne@yahoo.co [Laboratoire d' Automatique et d' Informatique Appliquee (LAIA), Departement de Genie Electrique, Universite de Dschang, B.P. 134 Bandjoun (Cameroon); Goma, Raphael, E-mail: raphael.goma@lss.supelec.f [Laboratoire des Signaux et Systemes (L2S), CNRS-SUPELEC, Universite Paris XI, 3 Rue Joliot Curie, 91192 Gif-sur-Yvette (France); Nkwawo, Homere, E-mail: homere.nkwawo@iutv.univ-paris13.f [Departement GEII, Universite Paris XIII, 99 Avenue Jean Baptiste Clement, 93430 Villetaneuse (France); Lamnabhi-Lagarrigue, Francoise, E-mail: lamnabhi@lss.supelec.f [Laboratoire des Signaux et Systemes (L2S), CNRS-SUPELEC, Universite Paris XI, 3 Rue Joliot Curie, 91192 Gif-sur-Yvette (France); Arzande, Amir, E-mail: Amir.arzande@supelec.f [Departement Energie, Ecole Superieure d' Electricite-SUPELEC, 3 Rue Joliot Curie, 91192 Gif-sur-Yvette (France); Vannier, Jean Claude, E-mail: Jean-claude.vannier@supelec.f [Departement Energie, Ecole Superieure d' Electricite-SUPELEC, 3 Rue Joliot Curie, 91192 Gif-sur-Yvette (France)

    2010-01-15

    A nonlinear adaptive excitation controller is proposed to enhance the transient stability and voltage regulation of synchronous generators with unknown power angle and mechanical power input. The proposed method is based on a standard third-order model of a synchronous generator which requires only information about the physical available measurements of relative angular speed, active electric power, infinite bus and generator terminal voltages. The operating conditions are computed online using the above physical available measurements, the terminal voltage reference value and the estimate of the mechanical power input. The proposed design is therefore capable of providing satisfactory voltage in the presence of unknown variations of the power system operating conditions. Using the concept of sliding mode equivalent control techniques, a robust decentralized adaptive controller which insures the exponential convergence of the outputs to the desired ones, is obtained. Real-time experimental results are reported, comparing the performance of the proposed adaptive nonlinear control scheme to one of the conventional AVR/PSS controller. The high simplicity of the overall adaptive control scheme and its robustness with respect to line impedance variation including critical unbalanced operating condition and temporary turbine fault, constitute the main positive features of the proposed approach.

  5. Gas Permeability Evolution Mechanism and Comprehensive Gas Drainage Technology for Thin Coal Seam Mining

    Directory of Open Access Journals (Sweden)

    Fangtian Wang

    2017-09-01

    Full Text Available A thin coal seam mined as a protective coal seam above a gas outburst coal seam plays a central role in decreasing the degree of stress placed on a protected seam, thus increasing gas permeability levels and desorption capacities to dramatically eliminate gas outburst risk for the protected seam. However, when multiple layers of coal seams are present, stress-relieved gas from adjacent coal seams can cause a gas explosion. Thus, the post-drainage of gas from fractured and de-stressed strata should be applied. Comprehensive studies of gas permeability evolution mechanisms and gas seepage rules of protected seams close to protective seams that occur during protective seam mining must be carried out. Based on the case of the LongWall (LW 23209 working face in the Hancheng coal mine, Shaanxi Province, this paper presents a seepage model developed through the FLAC3D software program (version 5.0, Itasca Consulting Group, Inc., Minneapolis, MI, USA from which gas flow characteristics can be reflected by changes in rock mass permeability. A method involving theoretical analysis and numerical simulation was used to analyze stress relief and gas permeability evolution mechanisms present during broken rock mass compaction in a goaf. This process occurs over a reasonable amount of extraction time and in appropriate locations for comprehensive gas extraction technologies. In using this comprehensive gas drainage technological tool, the safe and efficient co-extraction of thin coal seams and gas resources can be realized, thus creating a favorable environment for the safe mining of coal and gas outburst seams.

  6. A tool to separate optical/infrared disc and jet emission in X-ray transient outbursts: the colour-magnitude diagrams of XTE J1550-564

    NARCIS (Netherlands)

    Russell, D.M.; Maitra, D.; Dunn, R.J.H.; Fender, R.P.

    2011-01-01

    It is now established that thermal disc emission and non-thermal jet emission can both play a role at optical/infrared (OIR) wavelengths in X-ray transients. The spectra of the jet and disc components differ, as do their dependence on mass accretion properties. Here we demonstrate that the OIR

  7. Outbursting comet P/2010 V1 (Ikeya-Murakami): A miniature comet Holmes

    Energy Technology Data Exchange (ETDEWEB)

    Ishiguro, Masateru [Department of Physics and Astronomy, Seoul National University, Gwanak, Seoul 151-742 (Korea, Republic of); Jewitt, David [Department of Earth, Planetary and Space Sciences, University of California at Los Angeles, 595 Charles Young Drive East, Los Angeles, CA 90095-1567 (United States); Hanayama, Hidekazu; Miyaji, Takeshi; Fukushima, Hideo; Watanabe, Jun-ichi [Ishigakijima Astronomical Observatory, National Astronomical Observatory of Japan, Ishigaki, Okinawa 907-0024 (Japan); Usui, Fumihiko [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Sekiguchi, Tomohiko [Department of Teacher Training, Hokkaido University of Education, 9 Hokumon, Asahikawa 070-8621 (Japan); Yanagisawa, Kenshi; Kuroda, Daisuke [Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, Asaguchi, Okayama 719-0232 (Japan); Yoshida, Michitoshi [Hiroshima Astrophysical Science Center, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Ohta, Kouji [Department of Astronomy, Kyoto University, Kyoto 606-8502 (Japan); Kawai, Nobuyuki [Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)

    2014-05-20

    The short-period comet P/2010 V1 (Ikeya-Murakami, hereafter {sup V}1{sup )} was discovered visually by two amateur astronomers. The appearance of the comet was peculiar, consisting of an envelope, a spherical coma near the nucleus and a tail extending in the anti-solar direction. We investigated the brightness and the morphological development of the comet by taking optical images with ground-based telescopes. Our observations show that V1 experienced a large-scale explosion between UT 2010 October 31 and November 3. The color of the comet was consistent with the Sun (g' – R {sub C} = 0.61 ± 0.20, R {sub C} – I {sub C} = 0.20 ± 0.20, and B – R {sub C} = 0.93 ± 0.25), suggesting that dust particles were responsible for the brightening. We used a dynamical model to understand the peculiar morphology, and found that the envelope consisted of small grains (0.3-1 μm) expanding at a maximum speed of 500 ± 40 m s{sup –1}, while the tail and coma were composed of a wider range of dust particle sizes (0.4-570 μm) and expansion speeds 7-390 m s{sup –1}. The total mass of ejecta is ∼5 × 10{sup 8} kg and kinetic energy ∼5 × 10{sup 12} J. These values are much smaller than in the historic outburst of 17P/Holmes in 2007, but the energy per unit mass (1 × 10{sup 4} J kg{sup –1}) is comparable. The energy per unit mass is about 10% of the energy released during the crystallization of amorphous water ice suggesting that crystallization of buried amorphous ice can supply the mass and energy of the outburst ejecta.

  8. The Evolution of the Phase Lags Associated with the Type-C Quasi-periodic Oscillation in GX 339–4 during the 2006/2007 Outburst

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Liang; Chen, Li [Department of Astronomy, Beijing Normal University, Beijing 100875 (China); Wang, Yanan; Méndez, Mariano [Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, NL-9700 AV Groningen (Netherlands); Qu, Jinlu [Key Laboratory for Particle Astrophysics, Institute of High Energy Physics, CAS, Beijing 100049 (China); Altamirano, Diego [Department of Physics and Astronomy, University of Southampton, Southampton, Hampshire SO17 1BJ (United Kingdom); Belloni, Tomaso, E-mail: 201431160006@mail.bnu.edu.cn [INAF-Osservatorio Astronomico di Brera, via E. Bianchi 46, I-23807 Merate (Italy)

    2017-08-20

    We present the evolution of the phase lags associated with the type-C QPO in GX 339–4 during the rising phase of the 2006/2007 outburst. We find that the phase lags at the QPO frequency are always positive (hard) and show very different behavior between QPOs with frequencies below and above ∼1.7 Hz: when the QPO frequency is below ∼1.7 Hz, the phase lags increase both with QPO frequency and energy, while when the QPO frequency is above ∼1.7 Hz, the phase lags remain more or less constant. When the QPO frequency is higher than ∼1.7 Hz, a broad feature is always present in the lag–energy spectra at around 6.5 keV, suggesting that the reflection component may have a significant contribution to the phase lags. Below ∼1.7 Hz, the QPO rms first decreases with energy and then turns to almost flat, while above ∼1.7 Hz, the QPO rms increases with energy. During the transition from the low-hard state to the hard-intermediate state, the second harmonic and subharmonic of this QPO appear in the power density spectra. The second-harmonic and subharmonic phase lags show very similar evolutions for their centroid frequencies. However, the energy dependence of the second-harmonic and subharmonic phase lags are quite different. Our results suggest that, at different phases of the outburst, different mechanisms may be responsible for the phase lags of the QPO. We briefly discuss the possible scenarios for producing the lags.

  9. SUZAKU OBSERVATION OF STRONG FLUORESCENT IRON LINE EMISSION FROM THE YOUNG STELLAR OBJECT V1647 ORI DURING ITS NEW X-RAY OUTBURST

    International Nuclear Information System (INIS)

    Hamaguchi, Kenji; Grosso, Nicolas; Kastner, Joel H.; Richmond, Michael; Weintraub, David A.

    2010-01-01

    The Suzaku X-ray satellite observed the young stellar object (YSO) V1647 Ori on 2008 October 8 during the new mass accretion outburst reported in 2008 August. During the 87 ks observation with a net exposure of 40 ks, V1647 Ori showed a high level of X-ray emission with a gradual decrease in flux by a factor of 5 and then displayed an abrupt flux increase by an order of magnitude. Such enhanced X-ray variability was also seen in XMM-Newton observations in 2004 and 2005 during the 2003-2005 outburst, but has rarely been observed for other YSOs. The spectrum clearly displays emission from Helium-like iron, which is a signature of hot plasma (kT ∼ 5 keV). It also shows a fluorescent iron Kα line with a remarkably large equivalent width (EW) of ∼600 eV. Such a large EW suggests that a part of the incident X-ray emission that irradiates the circumstellar material and/or the stellar surface is hidden from our line of sight. XMM-Newton spectra during the 2003-2005 outburst did not show a strong fluorescent iron Kα line, so that the structure of the circumstellar gas very close to the stellar core that absorbs and re-emits X-ray emission from the central object may have changed in between 2005 and 2008. This phenomenon may be related to changes in the infrared morphology of McNeil's nebula between 2004 and 2008.

  10. Mechanical response of FFTF reference and P1 cladding tubes under transient heating

    International Nuclear Information System (INIS)

    Youngahl, C.A.; Ariman, T.; Lepacek, B.E.

    1977-01-01

    Burst tests of Type 316 stainless steel cladding tube samples subjected to increasing temperature and relatively constant internal pressure were conducted to assist in the pretest analysis of the P1 experiment performed in the Sodium Loop Safety Facility. This paper reports and analyzes the burst test results and those of subsequent transient heating work. The use of a modified extensometer in obtaining mechanical response data for stainless steel in the high temperature range is illustrated, some of such data is provided, and the potential of further experiments and analysis is indicated. Tubing of the same design as Fast Flux Test Facility (FFTF) cladding (20% cold worked, 0.230 in. OD, 15 mil wall) was tested as-received and after annealing or electrolytic thinning. P1 tubing (38% cold worked, 0.230 in. OD, 10 mil wall) was tested before and after aging under conditions anticipated in the P1 reactor experiment. The P1 cladding was designed to simulate FFTF tubing that had experienced irradiation embrittlement and attack by cesium oxide and sodium impurities

  11. Transient attenuation in optical fibers

    International Nuclear Information System (INIS)

    Hopkins, A.A.; Kelly, R.E.; Looney, L.D.; Lyons, P.B.

    1984-01-01

    Low and high energy pulsed electron beams were used to generate radiation-induced transient attenuation in high-OH, Suprasil core, PCS fibers, demonstrating the energy dependence of the radiation damage and recovery mechanisms. A radiation resistant low-OH fiber was studied and its performance contrasted to that of high-OH materials. Several fibers with differing core compositions were also studied

  12. Transient thermal, hydraulic, and mechanical analysis of a counter flow offset strip fin intermediate heat exchanger using an effective porous media approach

    Science.gov (United States)

    Urquiza, Eugenio

    This work presents a comprehensive thermal hydraulic analysis of a compact heat exchanger using offset strip fins. The thermal hydraulics analysis in this work is followed by a finite element analysis (FEA) to predict the mechanical stresses experienced by an intermediate heat exchanger (IHX) during steady-state operation and selected flow transients. In particular, the scenario analyzed involves a gas-to-liquid IHX operating between high pressure helium and liquid or molten salt. In order to estimate the stresses in compact heat exchangers a comprehensive thermal and hydraulic analysis is needed. Compact heat exchangers require very small flow channels and fins to achieve high heat transfer rates and thermal effectiveness. However, studying such small features computationally contributes little to the understanding of component level phenomena and requires prohibitive computational effort using computational fluid dynamics (CFD). To address this issue, the analysis developed here uses an effective porous media (EPM) approach; this greatly reduces the computation time and produces results with the appropriate resolution [1]. This EPM fluid dynamics and heat transfer computational code has been named the Compact Heat Exchanger Explicit Thermal and Hydraulics (CHEETAH) code. CHEETAH solves for the two-dimensional steady-state and transient temperature and flow distributions in the IHX including the complicating effects of temperature-dependent fluid thermo-physical properties. Temperature- and pressure-dependent fluid properties are evaluated by CHEETAH and the thermal effectiveness of the IHX is also calculated. Furthermore, the temperature distribution can then be imported into a finite element analysis (FEA) code for mechanical stress analysis using the EPM methods developed earlier by the University of California, Berkeley, for global and local stress analysis [2]. These simulation tools will also allow the heat exchanger design to be improved through an

  13. Transient Analysis and Design Improvement of a Gas Turbine Rotor Based on Thermal-Mechanical Method

    Directory of Open Access Journals (Sweden)

    Yang Liu

    2018-01-01

    Full Text Available The rotor is the core component of a gas turbine, and more than 80% of the failures in gas turbines occur in the rotor system, especially during the start-up period. Therefore, the safety assessment of the rotor during the start-up period is essential for the design of the gas turbine. In this paper, the transient equivalent stress of a gas turbine rotor under the cold start-up condition is investigated and the novel tie rod structure is introduced to reduce the equivalent stress. Firstly, a three-dimensional finite element model of the gas turbine rotor is built, and nonlinear contact behaviors such as friction are taken into account. Secondly, the convective heat transfer coefficients of the gas turbine rotor under the cold start-up condition are calculated using thermal dynamic theory. The transient analysis of the gas turbine rotor is conducted considering the thermal load, the centrifugal load, and the pretightening force. The temperature and stress distributions of the rotor under the cold start-up condition are shown in detail. In particular, the generation mechanism of maximum equivalent stress for tie rods and the change tendency of the pretightening force are illustrated in detail. The tie rod holes of the rear shaft and the turbine tie rod are the dangerous locations during the start-up period. Finally, a novel tie rod is proposed to reduce the maximum equivalent stress at the dangerous location. The maximum equivalent stress at this location is decreased by 15%. This paper provides some reference for the design of the gas turbine rotor.

  14. The Spectroscopic Evolution of the Symbiotic-like Recurrent Nova V407 Cygni During Its 2010 Outburst. 2. The Circumstellar Environment and the Aftermath

    Science.gov (United States)

    Shore, S. N.; Wahlgren, G. M.; Augusteijn, T.; Liimets, T.; Koubsky, P.; Slechta, M.; Votruba, V.

    2011-01-01

    The nova outburst of V407 Cyg in 2010 Mar. 10 was the first observed for this star but its close resemblance to the well known symbiotic-like recurrent nova RS Oph suggests that it is also a member of this rare type of Galactic novae. The nova was the first detected at gamma-ray energies and is the first known nova explosion for this system. The extensive multiwavelength coverage of this outburst makes it an ideal comparison with the few other outbursts known for similar systems. We extend our previous analysis of the Mira and the expanding shock from the explosion to detail the time development of the photoionized Mira wind, circumstellar medium, and shocked circumstellar environment to derive their physical parameters and how they relate to large scale structure of the environment, extending the previous coverage to more than 500 days after outburst. We use optical spectra obtained at high resolution with the Nordic Optical Telescope (NOT) (R approx. =.45000 to 65000) and medium resolution Ondrejov Observatory (R approx. = 12000) data and compare the line variations with publicly available archival measurements at 30 GHz OVNR and at X-rays with Swift during the first four months of the outburst, through the end of the epoch of strong XR emission. We use nebular diagnostics and high resolution profile variations to derive the densities and locations of the extended emission. We find that the higher the ionization and/or the higher the excitation energy, the more closely the profiles resemble the He II/Ca V-type high velocity shock profile discussed in Paper I. This also accounts for the comparative development of the [N II] and [O III] isoelectronic transitions: the [O III] 4363A profile does not show the low velocity peaks while the excited [N II] 5754A does. If nitrogen is mainly N(+3) or higher in the shock, the upper state of the [N II] nebular lines will contribute but if the oxygen is O(+2) then this line is formed by recombination, masking the nebular

  15. Topology optimization for transient heat transfer problems

    DEFF Research Database (Denmark)

    Zeidan, Said; Sigmund, Ole; Lazarov, Boyan Stefanov

    The focus of this work is on passive control of transient heat transfer problems using the topology optimization (TopOpt) method [1]. The goal is to find distributions of a limited amount of phase change material (PCM), within a given design domain, which optimizes the heat energy storage [2]. Our......, TopOpt has later been extended to transient problems in mechanics and photonics (e.g. [5], [6] and [7]). In the presented approach, the optimization is gradient-based, where in each iteration the non-steady heat conduction equation is solved,using the finite element method and an appropriate time......-stepping scheme. A PCM can efficiently absorb heat while keeping its temperature nearly unchanged [8]. The use of PCM ine.g. electronics [9] and mechanics [10], yields improved performance and lower costs depending on a.o., the spatial distribution of PCM.The considered problem consists in optimizing...

  16. Chandra, NuSTAR and NICER Observations of MAXI J1535-571

    Science.gov (United States)

    Neilsen, Joseph; Cackett, Ed; Fabian, Andy; Gendreau, Keith C.; Miller, Jon M.; Pasham, Dheeraj; Remillard, Ron; Steiner, Jack; Uttley, Phil

    2018-01-01

    In September 2017, MAXI detected an outburst of a previously-unknown transient, MAXI J1535-571. Subsequent radio and X-ray monitoring indicated that the source is a strong black hole candidate. We began a series of monitoring observations with Chandra HETGS, NuSTAR, and NICER to track the evolution of the outburst. Together, these three observatories represent an incredible opportunity to study the geometry of the accretion flow (via continuum spectroscopy), its variation with accretion state (via spectral variability), and any associated outflows or mass ejections (via line spectroscopy). We will present our analysis of this bright outburst and discuss the physics of accretion and ejection in this new black hole candidate.

  17. Oxide fuel pin transient performance analysis and design with the TEMECH code

    International Nuclear Information System (INIS)

    Bard, F.E.; Dutt, S.P.; Hinman, C.A.; Hunter, C.W.; Pitner, A.L.

    1986-01-01

    The TEMECH code is a fast-running, thermal-mechanical-hydraulic, analytical program used to evaluate the transient performance of LMR oxide fuel pins. The code calculates pin deformation and failure probability due to fuel-cladding differential thermal expansion, expansion of fuel upon melting, and fission gas pressurization. The mechanistic fuel model in the code accounts for fuel cracking, crack closure, porosity decrease, and the temperature dependence of fuel creep through the course of the transient. Modeling emphasis has been placed on results obtained from Fuel Cladding Transient Test (FCTT) testing, Transient Fuel Deformation (TFD) tests and TREAT integral fuel pin experiments

  18. KIC 4552982: outbursts and pulsations in the longest-ever pseudo-continuous light curve of a ZZ Ceti

    Directory of Open Access Journals (Sweden)

    Bell K. J.

    2015-01-01

    Full Text Available KIC 4552982 was the first ZZ Ceti (hydrogen-atmosphere pulsating white dwarf identified to lie in the Kepler field, resulting in the longest pseudo-continuous light curve ever obtained for this type of variable star. In addition to the pulsations, this light curve exhibits stochastic episodes of brightness enhancement unlike any previously studied white dwarf phenomenon. We briefly highlight the basic outburst and pulsation properties in these proceedings.

  19. Past explosive outbursts of entrapped carbon dioxide in salt mines provide a new perspective on the hazards of carbon dioxide

    DEFF Research Database (Denmark)

    Hedlund, Frank Huess

    2013-01-01

    This paper reports on a source of past carbon dioxide accidents which so far has only been sporadically mentioned in the literature. Violent and highly destructive outbursts of hundreds of tons of CO2 occurred regularly, if not routinely, in the now closed salt mines of the former DDR. The Menzen...

  20. Transient analysis for PWR reactor core using neural networks predictors

    International Nuclear Information System (INIS)

    Gueray, B.S.

    2001-01-01

    In this study, transient analysis for a Pressurized Water Reactor core has been performed. A lumped parameter approximation is preferred for that purpose, to describe the reactor core together with mechanism which play an important role in dynamic analysis. The dynamic behavior of the reactor core during transients is analyzed considering the transient initiating events, wich are an essential part of Safety Analysis Reports. several transients are simulated based on the employed core model. Simulation results are in accord the physical expectations. A neural network is developed to predict the future response of the reactor core, in advance. The neural network is trained using the simulation results of a number of representative transients. Structure of the neural network is optimized by proper selection of transfer functions for the neurons. Trained neural network is used to predict the future responses following an early observation of the changes in system variables. Estimated behaviour using the neural network is in good agreement with the simulation results for various for types of transients. Results of this study indicate that the designed neural network can be used as an estimator of the time dependent behavior of the reactor core under transient conditions

  1. The JCMT Transient Survey: Data Reduction and Calibration Methods

    International Nuclear Information System (INIS)

    Mairs, Steve; Lane, James; Johnstone, Doug; Kirk, Helen; Lacaille, Kevin; Chapman, Scott; Bower, Geoffrey C.; Bell, Graham S.; Graves, Sarah

    2017-01-01

    Though there has been a significant amount of work investigating the early stages of low-mass star formation in recent years, the evolution of the mass assembly rate onto the central protostar remains largely unconstrained. Examining in depth the variation in this rate is critical to understanding the physics of star formation. Instabilities in the outer and inner circumstellar disk can lead to episodic outbursts. Observing these brightness variations at infrared or submillimeter wavelengths constrains the current accretion models. The JCMT Transient Survey is a three-year project dedicated to studying the continuum variability of deeply embedded protostars in eight nearby star-forming regions at a one-month cadence. We use the SCUBA-2 instrument to simultaneously observe these regions at wavelengths of 450 and 850 μ m. In this paper, we present the data reduction techniques, image alignment procedures, and relative flux calibration methods for 850 μ m data. We compare the properties and locations of bright, compact emission sources fitted with Gaussians over time. Doing so, we achieve a spatial alignment of better than 1″ between the repeated observations and an uncertainty of 2%–3% in the relative peak brightness of significant, localized emission. This combination of imaging performance is unprecedented in ground-based, single-dish submillimeter observations. Finally, we identify a few sources that show possible and confirmed brightness variations. These sources will be closely monitored and presented in further detail in additional studies throughout the duration of the survey.

  2. The Emergence of the Infrared Transient VVV-WIT-06

    Science.gov (United States)

    Minniti, D.; Saito, R. K.; Forster, F.; Pignata, G.; Ivanov, V. D.; Lucas, P. W.; Beamin, J. C.; Borissova, J.; Catelan, M.; Gonzalez, O. A.; Hempel, M.; Hsiao, E.; Kurtev, R.; Majaess, D.; Masetti, N.; Morrell, N. I.; Phillips, M. M.; Pullen, J. B.; Rejkuba, M.; Smith, L.; Surot, F.; Valenti, E.; Zoccali, M.

    2017-11-01

    We report the discovery of an enigmatic large-amplitude ({{Δ }}{Ks}> 10.5 mag) transient event in near-IR data obtained by the VISTA Variables in the Via Lactea (VVV) ESO Public Survey. The object (designated VVV-WIT-06) is located at R.A. = 17:07:18.917, decl. = -39:06:26.45 (J2000), corresponding to Galactic coordinates l = 347.14539, b = 0.88522. It exhibits a clear eruption, peaking at Ks = 9 mag during 2013 July and fading to {Ks}˜ 16.5 in 2017. Our late near-IR spectra show post-outburst emission lines, including some broad emission lines (upward of {FWHM}˜ 3000 km s-1). We estimate a total extinction of {A}V=10{--}15 mag in the surrounding field, and no progenitor was observed in ZYJHKs images obtained during 2010-2012 (down to {K}s> 18.5 mag). Subsequent deep near-IR imaging and spectroscopy, in concert with the available multiband photometry, indicate that VVV-WIT-06 may be either: (I) the closest Type I SN observed in about 400 years, (II) an exotic high-amplitude nova that would extend the known realm of such objects, or (III) a stellar merger. In all of these cases, VVV-WIT-06 is a fascinating and curious astrophysical target under any of the scenarios considered. Based on observations taken within the ESO programmes 179.B-2002 and 298.D-5048, and on observations carried out at the Magellan Telescope at LCO.

  3. The JCMT Transient Survey: Data Reduction and Calibration Methods

    Energy Technology Data Exchange (ETDEWEB)

    Mairs, Steve; Lane, James [Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 1A1 (Canada); Johnstone, Doug; Kirk, Helen [NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC, V9E 2E7 (Canada); Lacaille, Kevin; Chapman, Scott [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, B3H 4R2 (Canada); Bower, Geoffrey C. [Academia Sinica Institute of Astronomy and Astrophysics, 645 N. A‘ohōkū Place, Hilo, HI 96720 (United States); Bell, Graham S.; Graves, Sarah, E-mail: smairs@uvic.ca [East Asian Observatory, 660 North A‘ohōkū Place, University Park, Hilo, Hawaii 96720 (United States); Collaboration: JCMT Transient Team

    2017-07-01

    Though there has been a significant amount of work investigating the early stages of low-mass star formation in recent years, the evolution of the mass assembly rate onto the central protostar remains largely unconstrained. Examining in depth the variation in this rate is critical to understanding the physics of star formation. Instabilities in the outer and inner circumstellar disk can lead to episodic outbursts. Observing these brightness variations at infrared or submillimeter wavelengths constrains the current accretion models. The JCMT Transient Survey is a three-year project dedicated to studying the continuum variability of deeply embedded protostars in eight nearby star-forming regions at a one-month cadence. We use the SCUBA-2 instrument to simultaneously observe these regions at wavelengths of 450 and 850 μ m. In this paper, we present the data reduction techniques, image alignment procedures, and relative flux calibration methods for 850 μ m data. We compare the properties and locations of bright, compact emission sources fitted with Gaussians over time. Doing so, we achieve a spatial alignment of better than 1″ between the repeated observations and an uncertainty of 2%–3% in the relative peak brightness of significant, localized emission. This combination of imaging performance is unprecedented in ground-based, single-dish submillimeter observations. Finally, we identify a few sources that show possible and confirmed brightness variations. These sources will be closely monitored and presented in further detail in additional studies throughout the duration of the survey.

  4. Study of Cygnus X-3 at ultrahigh energies during the 1989 radio outbursts

    International Nuclear Information System (INIS)

    Alexandreas, D.E.; Allen, R.C.; Berley, D.; Biller, S.D.; Burman, R.L.; Cady, R.; Chang, C.Y.; Dingus, B.L.; Dion, G.M.; Ellsworth, R.W.; Goodman, J.A.; Haines, T.J.; Hoffman, C.M.; Lloyd-Evans, J.; Lu, X.; Nagle, D.E.; Potter, M.E.; Sandberg, V.D.; Stark, M.J.; Talaga, R.L.; Vishwanath, P.R.; Yodh, G.B.; Zhang, W.

    1990-01-01

    A unique feature of Cygnus X-3 is that occasionally it has large radio outbursts that begin very abruptly and last for several days. Several experiments in the past have claimed to observe signals above 1 TeV correlated with these radio bursts; the most recent bursts occurred in June and July 1989. No significant signal was observed by the CYGNUS experiment over time scales longer than a day during this time; a 90%-confidence-level limit of 3.0x10 -13 cm -2 s -1 is placed on the flux above 50 TeV during the period from 15 May to 31 July 1989

  5. LMFBR. Off normal, transient test facilities and programs in the USA

    International Nuclear Information System (INIS)

    Herbst, R.J.

    1985-01-01

    The United States fast breeder reactor development program has included operational transient analyses and experiments to verify the predicted performance of core components. Operational transient testing has focused on off-normal operation during Plant Protection System terminated transient-overpower events. In-pile and out-of-pile tests have been used to simulate predicted thermal and mechanical strain cycles and measure component response. The spectrum of reactivity ramp rates investigated in TOP tests has recently been expanded to include rates of less than $0.1/s. These slow ramp rate studies are being done in cooperation with the Japanese. The US has also cooperated with the UK in the transient testing of Prototype Fast Reactor fuel pins

  6. The X-ray spectra of the black hole candidate 4U 1630-47 during its 2012 outburst

    Science.gov (United States)

    Wang, Y.; Mendez, M.

    2015-07-01

    Diaz Trigo et al. (2013) reported the detection of three Doppler-shifted emission lines arising from baryonic matter in the jet of 4U 1630-47 during its 2012 outburst. Here we propose an alternative model that, without the need of the lines from the jet, and with less free parameters, fits the same data equally well. In our model we allow the abundances of S and Fe in the interstellar medium to vary; the best-fitting values are, respectively, 1.5 and 0.5 times solar, consistent with recent findings. Our model also includes a moderately broad emission line and a narrow absorption line due to highly ionised Fe. (These lines are also present in the other observations of this source during the 2012 outburst.) This model fits well all the XMM-Newton observations of this source, both in burst and timing mode. In addition to the components that we fitted to the burst-mode data, the timing-mode observations show several absorption features due to ionised Fe and Ni, which reveal the presence of a highly-ionised absorber close to the source. Our model also fits well the burst-mode data using the most recent calibration files (March 2015), whereas the model from Diaz Trigo et al. does not.

  7. Rainfall and snow-melt triggered glacial lake outbursts: a systematic analysis of the Kedarnath (Uttarakhand, India), June 2013 disaster

    Science.gov (United States)

    Allen, Simon; Rastner, Philipp; Arora, Manohar; Huggel, Christian; Stoffel, Markus

    2015-04-01

    Heavy rainfall in early June 2013 triggered flash flooding and landslides throughout the Indian Himalayan state of Uttarakhand, killing more than 6000 people. The destruction of roads and trekking routes left around 100,000 pilgrims and tourists stranded. Most fatalities and damages resulted directly from a lake outburst and debris flow disaster originating from above the village of Kedarnath on June 16 and 17. Here we provide a first systematic analysis of the contributing factors leading to the Kedarnath disaster, both in terms of hydro-meteorological triggering (rainfall, snowmelt, and temperature) and topographic predisposition. Specifically, the topographic characteristics of the Charobari lake watershed above Kedarnath are compared with other glacial lakes across the northwestern Indian Himalayan states of Uttarakhand and Himachal Pradesh, and implications for glacier lake outburst hazard assessment in a changing climate are discussed. Our analysis suggests that the early onset of heavy monsoon rainfall (390 mm, June 10 - 17) immediately following a prolonged four week period of unusually rapid snow cover depletion and elevated streamflow is the crucial hydro-meteorological factor, resulting in slope saturation and significant runoff into the small seasonal glacial lake. Over a four week period the MODIS-derived snow covered area above Kedarnath decreased nearly 50%, from above average coverage in mid-May to well below average coverage by the second week of June. Such a rapid decrease has not been observed in the previous 13-year record, where the average decrease in snow covered area over the same four week window is only 15%. The unusual situation of the lake being dammed in a steep, unstable paraglacial environment, but fed entirely from snow-melt and rainfall within a fluvial dominated watershed is important in the context of this disaster. A simple scheme enabling large-scale recognition of such an unfavorable topographic setting is presented, and on the

  8. Test system to simulate transient overpower LMFBR cladding failure

    International Nuclear Information System (INIS)

    Barrus, H.G.; Feigenbutz, L.V.

    1981-01-01

    One of the HEDL programs has the objective to experimentally characterize fuel pin cladding failure due to cladding rupture or ripping. A new test system has been developed which simulates a transient mechanically-loaded fuel pin failure. In this new system the mechanical load is prototypic of a fuel pellet rapidly expanding against the cladding due to various causes such as fuel thermal expansion, fuel melting, and fuel swelling. This new test system is called the Fuel Cladding Mechanical Interaction Mandrel Loading Test (FCMI/MLT). The FCMI/MLT test system and the method used to rupture cladding specimens very rapidly to simulate a transient event are described. Also described is the automatic data acquisition and control system which is required to control the startup, operation and shutdown of the very fast tests, and needed to acquire and store large quantities of data in a short time

  9. Boiling and burnout phenomena under transient heat input, 1

    International Nuclear Information System (INIS)

    Aoki, Shigebumi; Kozawa, Yoshiyuki; Iwasaki, Hideaki.

    1976-01-01

    In order to simulate the thermo-hydrodynamic conditions at reactor power excursions, a test piece was placed in a forced convective channel and heated with exponential power inputs. The boiling heat transfer and the burnout heat flux under the transient heat input were measured, and pressure and water temperature changes in the test section were recorded at the same time. Following experimental results were obtained; (1) Transient boiling heat transfer characteristics at high heat flux stayed on the stationary nucleate boiling curve of each flow condition, or extrapolated line of the curves. (2) Transient burnout heat flux increased remarkably with decreasing heating-time-constant, when the flow rate was lower and the subcooling was higher. (3) Transient burnout phenomena were expressed with the relation of (q sub(max) - q sub(sBO)) tau = constant at several flow conditions. This relation was derived from the stationary burnout mechanism of pool boiling. (auth.)

  10. USA and RXTE Observations of a Variable Low-Frequency QPO in XTEJ1118+480

    Energy Technology Data Exchange (ETDEWEB)

    Bloom, Elliott

    2000-06-29

    The USA experiment on ARGOS and RXTE have extensively observed the X-ray transient XTEJ1118+480 during its recent outburst in 2000 April--June. The authors present detailed monitoring of the evolution of a low frequency QPO which drifts from 0.07 Hz to 0.15 Hz during the outburst. They examine possible correlations of the QPO frequency with the flux and spectral characteristics of the source, and compare this QPO to low frequency QPOs observed in other black hole candidates.

  11. The X-ray outburst of the Galactic Centre magnetar SGR J1745-2900 during the first 1.5 year

    NARCIS (Netherlands)

    Coti Zelati, F.; Rea, N.; Papitto, A.; Viganò, D.; Pons, J.A.; Turolla, R.; Esposito, P.; Haggard, D.; Baganoff, F.K.; Ponti, G.; Israel, G.L.; Campana, S.; Torres, D.F.; Tiengo, A.; Mereghetti, S.; Perna, R.; Zane, S.; Mignani, R.P.; Possenti, A.; Stella, L.

    2015-01-01

    In 2013 April a new magnetar, SGR 1745−2900, was discovered as it entered an outburst, at only 2.4 arcsec angular distance from the supermassive black hole at the centre of the Milky Way, Sagittarius A*. SGR 1745−2900 has a surface dipolar magnetic field of ∼2 × 1014 G, and it is the neutron star

  12. Transient analysis of a variable speed rotary compressor

    International Nuclear Information System (INIS)

    Park, Youn Cheol

    2010-01-01

    A transient simulation model of a rolling piston type rotary compressor is developed to predict the dynamic characteristics of a variable speed compressor. The model is based on the principles of conservation, real gas equations, kinematics of the crankshaft and roller, mass flow loss due to leakage, and heat transfer. For the computer simulation of the compressor, the experimental data were obtained from motor performance tests at various operating frequencies. Using the developed model, re-expansion loss, friction loss, mass flow loss and heat transfer loss is estimated as a function of the crankshaft speed in a variable speed compressor. In addition, the compressor efficiency and energy losses are predicted at various compressor-operating frequencies. Since the transient state of the compressor strongly depends on the system, the developed model is combined with a transient system simulation program to get transient variations of the compression process in the system. Motor efficiency, mechanical efficiency, motor torque and volumetric efficiency are calculated with respect to variation of the driving frequency in a rotary compressor.

  13. High-energy observations of the state transition of the X-ray nova and black hole candidate XTE J1720-318

    DEFF Research Database (Denmark)

    Bel, M.C.; Rodriguez, J.; Sizun, P.

    2004-01-01

    We report the results of extensive high-energy observations of the X-ray transient and black hole candidate XTE J1720-318 performed with INTEGRAL, XMM-Newton and RXTE. The source, which underwent an X-ray outburst in 2003 January, was observed in February in a spectral state dominated by a soft......, typical of a black-hole binary in the so-called High/Soft State. We then followed the evolution of the source outburst over several months using the INTEGRAL Galactic Centre survey observations. The source became active again at the end of March: it showed a clear transition towards a much harder state...... of the black hole X-ray novae class which populate our galactic bulge and we discuss its properties in the frame of the spectral models used for transient black hole binaries....

  14. The INTEGRAL Galactic bulge monitoring program: the first 1.5 years

    DEFF Research Database (Denmark)

    Kuulkers, E.; Shaw, S.E.; Paizis, A.

    2007-01-01

    V) black-hole candidate X-ray transient and three active weaker (less than or similar to 25 mCrab, 20-60 keV) neutron star X-ray transients. Most of the time a clear anti-correlation can be seen between the soft and hard X-ray emission in some of the X-ray bursters. Hard X-ray flares or outbursts in X...

  15. Cladding properties under simulated fuel pin transients

    International Nuclear Information System (INIS)

    Hunter, C.W.; Johnson, G.D.

    1975-01-01

    A description is given of the HEDL fuel pin testing program utilizing a recently developed Fuel Cladding Transient Tester (FCTT) to generate the requisite mechanical property information on irradiated and unirradiated fast reactor fuel cladding under temperature ramp conditions. The test procedure is described, and data are presented

  16. The Electroluminescence Mechanism of Solution-Processed TADF Emitter 4CzIPN Doped OLEDs Investigated by Transient Measurements

    Directory of Open Access Journals (Sweden)

    Peng Wang

    2016-10-01

    Full Text Available High efficiency, solution-processed, organic light emitting devices (OLEDs, using a thermally-activated delayed fluorescent (TADF emitter, 1,2,3,5-tetrakis(carbazol-9-yl-4,6-dicyanobenzene (4CzIPN, are fabricated, and the transient electroluminescence (EL decay of the device with a structure of [ITO/PEDOT: PSS/4CzIPN 5 wt % doped 4,40-N,N0-dicarbazolylbiphenyl(CBP/bis-4,6-(3,5-di-4-pyridylphenyl-2-methylpyrimidine (B4PyMPM/lithium fluoride (LiF/Al], is systematically studied. The results shed light on the dominant operating mechanism in TADF-based OLEDs. Electroluminescence in the host–guest system is mainly produced from the 4CzIPN emitter, rather than the exciplex host materials.

  17. Transient Go: A Mobile App for Transient Astronomy Outreach

    Science.gov (United States)

    Crichton, D.; Mahabal, A.; Djorgovski, S. G.; Drake, A.; Early, J.; Ivezic, Z.; Jacoby, S.; Kanbur, S.

    2016-12-01

    Augmented Reality (AR) is set to revolutionize human interaction with the real world as demonstrated by the phenomenal success of `Pokemon Go'. That very technology can be used to rekindle the interest in science at the school level. We are in the process of developing a prototype app based on sky maps that will use AR to introduce different classes of astronomical transients to students as they are discovered i.e. in real-time. This will involve transient streams from surveys such as the Catalina Real-time Transient Survey (CRTS) today and the Large Synoptic Survey Telescope (LSST) in the near future. The transient streams will be combined with archival and latest image cut-outs and other auxiliary data as well as historical and statistical perspectives on each of the transient types being served. Such an app could easily be adapted to work with various NASA missions and NSF projects to enrich the student experience.

  18. Transient receptor potential channel superfamily: Role in lower urinary tract function.

    Science.gov (United States)

    Ogawa, Teruyuki; Imamura, Tetsuya; Nakazawa, Masaki; Hiragata, Shiro; Nagai, Takashi; Minagawa, Tomonori; Yokoyama, Hitoshi; Ishikawa, Masakuni; Domen, Takahisa; Ishizuka, Osamu

    2015-11-01

    Lower urinary tract symptoms associated with neurogenic bladder and overactive bladder syndrome are mediated in part by members of the transient receptor potential channel superfamily. The best studied member of this superfamily is the vanilloid receptor. Other transient receptor potential channels, such as the melastatin receptor and the ankyrin receptor, are also active in the pathogenesis of lower urinary tract dysfunction. However, the detailed mechanisms by which the transient receptor potential channels contribute to lower urinary tract symptoms are still not clear, and the therapeutic benefits of modulating transient receptor potential channel activity have not been proved in the clinical setting. In the present review, to better understand the pathophysiology and therapeutic potential for lower urinary tract symptoms, we summarize the presence and role of different members of the transient receptor potential channel superfamily in the lower urinary tract. © 2015 The Japanese Urological Association.

  19. Glacial lake outburst floods and fluvial erosion in the Himalaya - insights from the 2016 Bhote Koshi GLOF

    Science.gov (United States)

    Cook, K. L.; Gimbert, F.; Andermann, C.; Hovius, N.; Adhikari, B. R.

    2017-12-01

    The Himalaya is a region of rapid erosion where fluvial processes are assumed to be driven by precipitation delivered during the annual Indian Summer Monsoon. However, the rivers in this region are also subject to catastrophic floods caused by the failure of glacial lake and landslide dams. Because these floods are rarely observed, it has been difficult to isolate their impact on the rivers and adjacent hillslopes, and their importance for the long-term evolution of Himalayan valleys is largely unknown. In July 2016, the Bhotekoshi/Sunkoshi River in central Nepal was hit by a glacial lake outburst flood (GLOF) that caused substantial changes to the channel bed, banks, and adjacent hillslopes, causing at least 26 landslides and an average of 11 m of channel widening. The flood passed through a seismic and hydrological observatory installed along the river in June 2015, and we have used the resulting data to constrain the timing, duration, and bedload transport properties of the outburst flood. The impact of the flood on the river can be further observed with hourly time-lapse photographs, daily measurements of suspended sediment load, repeat lidar surveys, and satellite imagery. The outburst flood affected the river on several timescales. In the short term, it transported large amounts of coarse sediment and restructured the river bed during the hours of the flood pulse itself. Over intermediate timescales it resulted in elevated bedload and suspended load transport for several weeks following the flood. Over longer timescales the flood undercut and destabilized the river banks and hillslopes in a number of locations, leading to bank collapses, slumps, and landslides. Our data indicate that impacts of the GLOF far exceed those driven by the annual summer monsoon, likely due to extremely coarse sediment that armors much of the channel. The relatively frequent occurrence of GLOFs and the extremely high discharges relative to monsoon floods suggest that GLOFs may

  20. Interacting supernovae and supernova impostors

    Science.gov (United States)

    Tartaglia, Leonardo

    2016-02-01

    Massive stars are thought to end their lives with spectacular explosions triggered by the gravitational collapse of their cores. Interacting supernovae are generally attributed to supernova explosions occurring in dense circumstellar media, generated through mass-loss which characterisie the late phases of the life of their progenitors. In the last two decades, several observational evidences revealed that mass-loss in massive stars may be related to violent eruptions involving their outer layers, such as the luminous blue variables. Giant eruptions of extragalactic luminous blue variables, similar to that observed in Eta Car in the 19th century, are usually labelled 'SN impostors', since they mimic the behaviour of genuine SNe, but are not the final act of the life of the progenitor stars. The mechanisms producing these outbursts are still not understood, although the increasing number of observed cases triggered the efforts of the astronomical community to find possible theoretical interpretations. More recently, a number of observational evidences suggested that also lower-mass stars can experience pre-supernova outbursts, hence becoming supernova impostors. Even more interestingly, there is growing evidence of a connection among massive stars, their outbursts and interacting supernovae. All of this inspired this research, which has been focused in particular on the characterisation of supernova impostors and the observational criteria that may allow us to safely discriminate them from interacting supernovae. Moreover, the discovery of peculiar transients, motivated us to explore the lowest range of stellar masses that may experience violent outbursts. Finally, the quest for the link among massive stars, their giant eruptions and interacting supernovae, led us to study the interacting supernova LSQ13zm, which possibly exploded a very short time after an LBV-like major outburst.

  1. Chandra monitoring of the Galactic Centre magnetar SGR J1745-2900 during the initial 3.5 years of outburst decay

    NARCIS (Netherlands)

    Coti Zelati, F.; Rea, N.; Turolla, R.; Pons, J.A.; Papitto, A.; Esposito, P.; Israel, G.L.; Campana, S.; Zane, S.; Tiengo, A.; Mignani, R.P.; Mereghetti, S.; Baganoff, F.K.; Haggard, D.; Ponti, G.; Torres, D.F.; Borghese, A.; Elfritz, J.

    2017-01-01

    We report on 3.5 yr of Chandra monitoring of the Galactic Centre magnetar SGR J1745−2900 since its outburst onset in 2013 April. The magnetar spin-down has shown at least two episodes of period derivative increases so far, and it has slowed down regularly in the past year or so. We observed a

  2. ELOCA: fuel element behaviour during high temperature transients

    International Nuclear Information System (INIS)

    Sills, H.E.

    1979-03-01

    The ELOCA computer code was developed to simulate the uniform thermal-mechanical behaviour of a fuel element during high-temperature transients such as a loss-of-coolant accident (LOCA). Primary emphasis is on the diametral expansion of the fuel sheath. The model assumed is a single UO2/zircaloy-clad element with axisymmetric properties. Physical effects considered by the code are fuel expansion, cracking and melting; variation, during the transient, of internal gas pressure; changing fuel/sheath heat transfer; thermal, elastic and plastic sheath deformation (anisotropic); Zr/H 2 O chemical reaction effects; and beryllium-assisted crack penetration of the sheath. (author)

  3. Transient virulence of emerging pathogens.

    Science.gov (United States)

    Bolker, Benjamin M; Nanda, Arjun; Shah, Dharmini

    2010-05-06

    Should emerging pathogens be unusually virulent? If so, why? Existing theories of virulence evolution based on a tradeoff between high transmission rates and long infectious periods imply that epidemic growth conditions will select for higher virulence, possibly leading to a transient peak in virulence near the beginning of an epidemic. This transient selection could lead to high virulence in emerging pathogens. Using a simple model of the epidemiological and evolutionary dynamics of emerging pathogens, along with rough estimates of parameters for pathogens such as severe acute respiratory syndrome, West Nile virus and myxomatosis, we estimated the potential magnitude and timing of such transient virulence peaks. Pathogens that are moderately evolvable, highly transmissible, and highly virulent at equilibrium could briefly double their virulence during an epidemic; thus, epidemic-phase selection could contribute significantly to the virulence of emerging pathogens. In order to further assess the potential significance of this mechanism, we bring together data from the literature for the shapes of tradeoff curves for several pathogens (myxomatosis, HIV, and a parasite of Daphnia) and the level of genetic variation for virulence for one (myxomatosis). We discuss the need for better data on tradeoff curves and genetic variance in order to evaluate the plausibility of various scenarios of virulence evolution.

  4. Transient redistribution of intragranular fission gas in irradiated mixed oxide

    International Nuclear Information System (INIS)

    Hinman, C.A.; Randklev, E.H.

    1981-01-01

    Safety analyses for an LMFBR require a knowledge of the fuel and fission gas behavior under transient conditions. Analyses of microstructural data derived from transiently heated, irradiated, mixed oxide fuel specimens have allowed the calculation of the degree of nonequilibrium of intragranular bubbles formed during the transient. It is hypothesized that the observed over-pressurization of the intragranular bubbles mechanically loads the fuel within the grain, leading to a stress gradient derived force upon near-grain-surface bubbles, driving them preferentially to the grain boundaries. Using existing models for forced diffusion it can be estimated that the stress derived forces on bubbles are within the same magnitude, and possibly greater, than the forces derived from the thermal gradient

  5. Using satellite images to monitor glacial-lake outburst floods: Lago Cachet Dos drainage, Chile

    Science.gov (United States)

    Friesen, Beverly A.; Cole, Christopher J.; Nimick, David A.; Wilson, Earl M.; Fahey, Mark J.; McGrath, Daniel J.; Leidich, Jonathan

    2015-01-01

    The U.S. Geological Survey (USGS) is monitoring and analyzing glacial-lake outburst floods (GLOFs) in the Colonia valley in the Patagonia region of southern Chile. A GLOF is a type of flood that occurs when water impounded by a glacier or a glacial moraine is released catastrophically. In the Colonia valley, GLOFs originating from Lago Cachet Dos, which is dammed by the Colonia Glacier, have recurred periodically since 2008. The water discharged during these GLOFs flows under or through the Colonia Glacier, into Lago Colonia and then the Río Colonia, and finally into the Río Baker—Chile's largest river in terms of volume of water.

  6. Fatigue status assessment for reactor pressure vessel based on actual operational transient

    International Nuclear Information System (INIS)

    Zhu Guangqiang; Liao Changbin; Dai Bing; Gui Chun

    2013-01-01

    Background: Fatigue is an important aging mechanism in RPV and it must be contained to aging management working range. Purpose: In order to ensure the safety operation of nuclear power plants, as extension of RPV service time, it is necessary to assess the fatigue damage caused by actual operation transient. Methods: Based on monitoring data of actual operation during the past eleven years, refer to design transient, the statistic analysis for types and occurrence times of actual transient is carried out, at the same time, every transients are combined as different operation cycles and the temperature field and stress field of typical components are analyzed by FEM. Results: Based on these information, fatigue analysis and assessment are finished, if later-actual transients are similar with the previous transients, the calculation result shows that the ratio between maximum of cumulative usage factors and design calculation value is 0.4967 the design transients is conservative. Conclusions: Fatigue status of RPV could be assessed and traced quickly through fatigue status assessment method in this paper based on actual operational transient and assessment result would be a good reference for RPV aging management. (authors)

  7. Outburst Prevention Technology with Borehole Hydraulic Jet Through Strata in Floor Gateway%底板巷穿层钻孔水力冲孔防突技术

    Institute of Scientific and Technical Information of China (English)

    刘明举; 郭献林; 李波; 王冕

    2011-01-01

    针对新安矿14211运输巷掘进过程中面临的煤与瓦斯突出问题,为了研究和确定适合新安煤田三软煤层赋存特点的水力冲孔工艺和消突评价体系,使其快速消除工作面突出危险性,提高煤巷掘进速度,采用底板巷穿层钻孔水力冲孔防突措施,按照考察出的冲孔影响半径均匀布置钻孔,排出部分煤体和瓦斯,使煤体卸压增透.试验结果表明,底板巷穿层水力冲孔技术较好地适应和利用了三软煤层的赋存特点,消除了工作面的突出危险性,掘进速度也由之前的40 m/月提高到75m/月,提高了87.5%.%According to coal and gas outburst problems occurred in the heading process of the No.14211 transportation gateway in Xin'an Mine, in order to study and set up the borehole hydraulic jet technique and the outburst evaluation system suitable for the three soft seam deposit features in Xin'an Coalfield, to rapidly eliminate the outburst danger of the heading face and to improve the seam gateway heading speed, the outburst prevention measures with borehole hydraulic jet through the strata in the floor gateway were applied.According the investigation of the borehole hydraulic jet influence radius, a layout of the berehole pattern was evenly set up and a partial coal and gas could be discharged.Thus the seam pressure could be released and the permeability of the seam could be improved.The experiment result showed that the borehole hydraulic jet technology passed through strata in the floor gateway would be well suitable for and utilization of the deposit features of the three soft seam and could eliminate the outburst danger of the heading face.Thus the heading speed could be improved from the previous 40 m/month to 75 m/month and the heading efficiency was improved by 87.5%.

  8. The development of the fuel rod transient performance analysis code FTPAC

    International Nuclear Information System (INIS)

    Han Zhijie; Ji Songtao

    2014-01-01

    Fuel rod behavior, especially the integrity of cladding, played an important role in fuel safety research during reactor transient and hypothetical accidents conditions. In order to study fuel rod performance under transient accidents, FTPAC (Fuel Transient Performance Analysis Code) has been developed for simulating light water reactor fuel rod transient behavior when power or coolant boundary conditions are rapidly changing. It is composed of temperature, mechanical deformation, cladding oxidation and gas pressure model. The assessment was performed by comparing FTPAC code analysis result to experiments data and FRAPTRAN code calculations. Comparison shows that, the FTPAC gives reasonable agreement in temperature, deformation and gas pressure prediction. And the application of slip coefficient is more suitable for simulating the sliding between pellet and cladding when the gap is closed. (authors)

  9. Transient analysis of intermittent multijet sprays

    Energy Technology Data Exchange (ETDEWEB)

    Panao, Miguel R.O.; Moreira, Antonio Luis N. [Universidade Tecnica de Lisboa, IN, Center for Innovation, Technology and Policy Research, Instituto Superior Tecnico, Lisboa (Portugal); Durao, Diamantino G. [Universidade Lusiada, Lisboa (Portugal)

    2012-07-15

    This paper analyzes the transient characteristics of intermittent sprays produced by the single-point impact of multiple cylindrical jets. The aim is to perform a transient analysis of the intermittent atomization process to study the effect of varying the number of impinging jets in the hydrodynamic mechanisms of droplet formation. The results evidence that hydrodynamic mechanisms underlying the physics of ligament fragmentation in 2-impinging jets sprays also apply to sprays produced with more than 2 jets during the main period of injection. Ligaments detaching from the liquid sheet, as well as from its bounding rim, have been identified and associated with distinct droplet clusters, which become more evident as the number of impinging jets increases. Droplets produced by detached ligaments constitute the main spray, and their axial velocity becomes more uniformly distributed with 4-impinging jets because of a delayed ligament fragmentation. Multijet spray dispersion patterns are geometric depending on the number of impinging jets. Finally, an analysis on the Weber number of droplets suggests that multijet sprays are more likely to deposit on interposed surfaces, thus becoming a promising and competitive atomization solution for improving spray cooling. (orig.)

  10. On the recurrence time and outburst properties of the soft X-ray transient Aquila X-1

    Czech Academy of Sciences Publication Activity Database

    Šimon, Vojtěch

    2002-01-01

    Roč. 381, č. 1 (2002), s. 151-167 ISSN 0004-6361 R&D Projects: GA ČR GA205/00/P013 Institutional research plan: CEZ:AV0Z1003909 Keywords : stars activity * stars magnetic fields * close binaries Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 3.781, year: 2002

  11. OPTICAL VARIABILITY OF THE ACCRETION DISK AROUND THE INTERMEDIATE-MASS BLACK HOLE ESO 243-49 HLX-1 DURING THE 2012 OUTBURST

    Energy Technology Data Exchange (ETDEWEB)

    Webb, N. A.; Godet, O.; Barret, D. [Université de Toulouse, UPS-OMP, IRAP, Toulouse (France); Wiersema, K. [University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Lasota, J.-P. [Institut d' Astrophysique de Paris, UMR 7095, CNRS, UPMC Université Paris 06, 98bis Boulevard Arago, F-75014 Paris (France); Farrell, S. A. [Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006 (Australia); Maccarone, T. J. [Department of Physics, Box 41051, Texas Tech University, Lubbock TX 79409-1051 (United States); Servillat, M., E-mail: natalie.webb@irap.omp.eu [Laboratoire AIM (CEA/DSM/IRFU/SAp, CNRS, Université Paris Diderot), CEA Saclay, Bat. 709, F-91191 Gif-sur-Yvette (France)

    2014-01-01

    We present dedicated quasi-simultaneous X-ray (Swift) and optical (Very Large Telescope, V-, and R-band) observations of the intermediate-mass black hole candidate HLX-1 before and during the 2012 outburst. We show that the V-band magnitudes vary with time, thus proving that a portion of the observed emission originates in the accretion disk. Using the first quiescent optical observations of HLX-1, we show that the stellar population surrounding HLX-1 is fainter than V ∼ 25.1 and R ∼ 24.2. We show that the optical emission may increase before the X-ray emission consistent with the scenario proposed by Lasota et al. in which the regular outbursts could be related to the passage at periastron of a star circling the intermediate-mass black hole in an eccentric orbit, which triggers mass transfer into a quasi-permanent accretion disk around the black hole. Further, if there is indeed a delay in the X-ray emission we estimate the mass-transfer delivery radius to be ∼10{sup 11} cm.

  12. Mercury exports from a High-Arctic river basin in Northeast Greenland (74°N) largely controlled by glacial lake outburst floods

    DEFF Research Database (Denmark)

    Søndergaard, Jens; Tamstorf, Mikkel P.; Elberling, Bo

    2015-01-01

    .025 mg kg(-1). Temporal variations in river Hg were mainly associated with snowmelt, sudden erosion events, and outburst floods from a glacier-dammed lake in the upper part of the ZRB. Annual Hg exports from the 514 km(2) ZRB varied from 0.71 to >1.57 kg and the majority (86-96 was associated...... with sediment-bound Hg. Hg yields from the ZRB varied from 1.4-3.1 g Hg km(-2) yr(-1) and were among the highest yields reported from Arctic river basins. River exports of Hg from ZRB were found to be largely controlled by the frequency, magnitude and timing of the glacial lake outburst floods, which occurred...... in four of the five years in July-August. Floods accounted for 5 to >10% of the annual water discharge, and up to >31% of the annual Hg export. Also, the winter snowfall and the summer temperatures were found to be important indirect controls on the annual Hg export. The occurrence and timing of glacial...

  13. The origin of pits on 9P/Tempel 1 and the geologic signature of outbursts in Stardust-NExT images

    Science.gov (United States)

    Belton, Michael J. S.; Thomas, Peter; Carcich, Brian; Quick, Andrew; Veverka, Joseph; Jay Melosh, H.; A'Hearn, Michael F.; Li, Jian-Yang; Brownlee, Donald; Schultz, Peter; Klaasen, Kenneth; Sarid, Gal

    2013-02-01

    We consider the origin of ˜380 quasi-circular depressions (pits) seen to be distributed in a broad band across the surface of 9P/Tempel 1 and show that possibly ˜96% may be due to outburst activity. Of the rest, Lisse, C.M., Holloway, M., Rho, J. [2010]. Icarus 208, 276-292) based on IR observations of 17P.

  14. The transient creep of vapor deposited Ti-6Al-4V

    International Nuclear Information System (INIS)

    Warren, J.; Wadley, H.N.G.

    1996-01-01

    Titanium matrix composites can be synthesized by the consolidation of ceramic fibers (for example, alumina and silicon carbide monofilaments) coated with titanium alloy deposited on the fiber by physical vapor deposition (PVD). Consolidation involves deformation of the matrix coating by both transient and steady-state creep. In a recent paper the mechanisms responsible for steady-state creep in PVD Ti-6Al-4V, between 600 and 900 C, were determined. The analysis of the data first presented has been extended here to consider the transient creep behavior of the material and identify an analogous constitutive law for use in simulating the transient creep contribution to consolidation

  15. Familial Transient Global Amnesia

    Directory of Open Access Journals (Sweden)

    R.Rhys Davies

    2012-12-01

    Full Text Available Following an episode of typical transient global amnesia (TGA, a female patient reported similar clinical attacks in 2 maternal aunts. Prior reports of familial TGA are few, and no previous account of affected relatives more distant than siblings or parents was discovered in a literature survey. The aetiology of familial TGA is unknown. A pathophysiological mechanism akin to that in migraine attacks, comorbidity reported in a number of the examples of familial TGA, is one possibility. The study of familial TGA cases might facilitate the understanding of TGA aetiology.

  16. Deformation modeling and the strain transient dip test

    International Nuclear Information System (INIS)

    Jones, W.B.; Rohde, R.W.; Swearengen, J.C.

    1980-01-01

    Recent efforts in material deformation modeling reveal a trend toward unifying creep and plasticity with a single rate-dependent formulation. While such models can describe actual material deformation, most require a number of different experiments to generate model parameter information. Recently, however, a new model has been proposed in which most of the requisite constants may be found by examining creep transients brought about through abrupt changes in creep stress (strain transient dip test). The critical measurement in this test is the absence of a resolvable creep rate after a stress drop. As a consequence, the result is extraordinarily sensitive to strain resolution as well as machine mechanical response. This paper presents the design of a machine in which these spurious effects have been minimized and discusses the nature of the strain transient dip test using the example of aluminum. It is concluded that the strain transient dip test is not useful as the primary test for verifying any micromechanical model of deformation. Nevertheless, if a model can be developed which is verifiable by other experimentts, data from a dip test machine may be used to generate model parameters

  17. Picosecond transient absorption spectra of aminosalicylates in confirmation of the triple excitation mechanism

    International Nuclear Information System (INIS)

    Gormin, D.

    1989-01-01

    Using picosecond transient absorption studies, it is shown that the twisted intramolecular charge-transfer state (TICT) and the excited intramolecular proton-transfer state (ESIPT or PT) of specific aminosalicylates both contribute to the long-wavelength fluorescence band, F 2 , observed as an unresolved band to the red of the normal fluorescence band, F 1 . The transient absorption band for 2-hydroxy-4-(dimethylamino)benzoic acid methyl ester (PDASE) is shown to be a composite of the two excited-state absorption modes: S n double-prime(TICT) left-arrow S 1 double-prime (TICT) and S n '(PT)left-arrow S 1 '(PT). This corroborates previous steady-state fluorescence studies of the unresolved F 2 band. The assignments are based on comparison with the excited-state absorption spectra of various substituted aminosalicylates in polar and nonpolar solvents

  18. Transients in reactors for power systems compensation

    Science.gov (United States)

    Abdul Hamid, Haziah

    This thesis describes new models and investigations into switching transient phenomena related to the shunt reactors and the Mechanically Switched Capacitor with Damping Network (MSCDN) operations used for reactive power control in the transmission system. Shunt reactors and MSCDN are similar in that they have reactors. A shunt reactor is connected parallel to the compensated lines to absorb the leading current, whereas the MSCDN is a version of a capacitor bank designed as a C-type filter for use in the harmonic-rich environment. In this work, models have been developed and transient overvoltages due to shunt reactor deenergisation were estimated analytically using MathCad, a mathematical program. Computer simulations used the ATP/EMTP program to reproduce both single-phase and three-phase shunt reactor switching at 275 kV operational substations. The effect of the reactor switching on the circuit breaker grading capacitor was also examined by considering various switching conditions.. The main original achievement of this thesis is the clarification of failure mechanisms occurring in the air-core filter reactor due to MSCDN switching operations. The simulation of the MSCDN energisation was conducted using the ATP/EMTP program in the presence of surge arresters. The outcome of this simulation shows that extremely fast transients were established across the air-core filter reactor. This identified transient event has led to the development of a detailed air-core reactor model, which accounts for the inter-turn RLC parameters as well as the stray capacitances-to-ground. These parameters are incorporated into the transient simulation circuit, from which the current and voltage distribution across the winding were derived using electric field and equivalent circuit modelling. Analysis of the results has revealed that there are substantial dielectric stresses imposed on the winding insulation that can be attributed to a combination of three factors. (i) First, the

  19. A NICER View of the Accretion Disk in GX 339-4

    Science.gov (United States)

    Steiner, James Francis; Bulbul, Esra; Cackett, Ed; Fabian, Andy; Gendreau, Keith C.; Neilsen, Joseph; Ranga Reddy Pasham, Dheeraj; Remillard, Ron; Uttley, Phil; Wood, Kent S.

    2018-01-01

    The poster-child black hole transient GX 339-4 has gone into outburst once again. With no pileup, low-background, and high fidelity in the soft X-ray bandpass, NICER is uniquely positioned to detect emergent thermal disk emission from an optically thick accretion flow approaching the innermost-stable circular orbit. We present NICER's results on the 2017 outburst, and detail its implications for the disk-truncation controversy. We also investigate the X-ray state evolution, as seen in NICER's spectral range of 0.2 to 12 keV.

  20. Current interruption transients calculation

    CERN Document Server

    Peelo, David F

    2014-01-01

    Provides an original, detailed and practical description of current interruption transients, origins, and the circuits involved, and how they can be calculated Current Interruption Transients Calculationis a comprehensive resource for the understanding, calculation and analysis of the transient recovery voltages (TRVs) and related re-ignition or re-striking transients associated with fault current interruption and the switching of inductive and capacitive load currents in circuits. This book provides an original, detailed and practical description of current interruption transients, origins,

  1. The properties of cross-correlation and spectra of the low-mass X-ray binary 4U 1608-52

    International Nuclear Information System (INIS)

    Lei, Ya-Juan; Yuan, Hai-Long; Dong, Yi-Qiao; Zhang, Hao-Tong; Zhang, Cheng-Min; Zhao, Yong-Heng; Zhang, Shu; Qu, Jin-Lu; Wang, Ya-Nan; Li, Zhi-Bing

    2014-01-01

    With RXTE data, we analyzed the cross-correlation function between the soft and hard X-rays of the transient atoll source 4U 1608-52. We found anti-correlations in three outbursts occurred in 1998, 2002, and 2010, and we found significant time lags of several hundreds of seconds in the latter two outbursts. Our results show no correlation between the soft and hard X-rays in the extreme island state and a dominated positive correlation in the lower banana state. Anti-correlations are presented at the upper banana state for the outburst of 2010 and at the island and the lower left banana states for the other two outbursts. So far for atoll sources, the cross-correlation has been studied statistically only for 4U 1735-44, where anti-correlations showed up in the upper banana state. Here our investigation on 4U 1608-52 provides a similar result in its 2010 outburst. In addition, we notice that the luminosities in the upper banana of the 1998 and 2002 outbursts are about 1.5 times that of the 2010 outburst whose luminosity in the upper banana is close to that of 4U 1735-44. The results suggest that the states in the color-color diagram of a source could be correlated with the luminosity of the source. A further spectral analysis during the 2010 outburst is also shown, which suggests that the disk can be a little truncated in the upper banana. The feature on the upper banana is similar to the previous results of the flaring branch in Z sources.

  2. Description and characterization of the ACRR's programmable transient rod withdrawal mode

    International Nuclear Information System (INIS)

    Boldt, K.R.; Sullivan, W.H.; Kefauver, H.L.

    1980-01-01

    To satisfy experiment needs for Sandia's Advanced Reactor Safety Program, a programmable Transient Rod Withdrawal (TRW) mode has been developed for the Annular Core Research Reactor (ACRR). The programmable mode is a modification of the existing continuous-withdrawal TRW mode and permits speed and direction changes during the pulse sequence. Basically, a TRW operation is similar to a routine pulse operation except that transient rods are mechanically withdrawn rather than pneumatically fired. Being a pulse-type operation, the TRW mode complies with pulse-mode safety system settings. Control system interlocks prevent the pneumatic firing of rods in the TRW mode. The hardware for the programmable TRW mode includes three ACRR transient rods, the ACRR timer, two rod programmers, a minicomputer and a summing circuit for position indication. Each ACRR transient rod is mechanically driven by a stepping motor (rated torque at 4.24 joules) and is capable of a maximum TRW speed of 26.7 centimeters/ second. The maximum reactivity insertion rate is $2.45/second with a transient rod bank worth of $3.00 and $3.47/second with a bank worth of $4.25, which is expected to be installed soon. The ACRR timer is a multifunctional timer used in all operating modes of the reactor. In the programmable TRW mode, the timer starts the rod programmers and drops regulating rods to terminate the operation. Programmed withdrawal capability is provided by one of two rod programmers (a hardwire-based unit and a microprocessor-based unit). The hardwire unit has eight intervals in which speed, direction and distance are selected by switches on the front panel. The microprocessor-based unit has the capability of 64 intervals in which speed, direction, and distance or time can be specified. Programming this unit is accomplished from the front panel or by inputting data from an HP-9845. minicomputer via a digital I/O interface. Self-test programs in the software provide a continual check of an operating

  3. Hydrological controls on transient aquifer storage in a karst watershed

    Science.gov (United States)

    Spellman, P.; Martin, J.; Gulley, J. D.

    2017-12-01

    While surface storage of floodwaters is well-known to attenuate flood peaks, transient storage of floodwaters in aquifers is a less recognized mechanism of flood peak attenuation. The hydraulic gradient from aquifer to river controls the magnitude of transient aquifer storage and is ultimately a function of aquifer hydraulic conductivity, and effective porosity. Because bedrock and granular aquifers tend to have lower hydraulic conductivities and porosities, their ability to attenuate flood peaks is generally small. In karst aquifers, however, extensive cave systems create high hydraulic conductivities and porosities that create low antecedent hydraulic gradients between aquifers and rivers. Cave springs can reverse flow during high discharges in rivers, temporarily storing floodwaters in the aquifer thus reducing the magnitude of flood discharge downstream. To date however, very few studies have quantified the magnitude or controls of transient aquifer storage in karst watersheds. We therefore investigate controls on transient aquifer storage by using 10 years of river and groundwater data from the Suwannee River Basin, which flows over the karstic upper Floridan aquifer in north-central Florida. We use multiple linear regression to compare the effects of three hydrological controls on the magnitude of transient aquifer storage: antecedent stage, recharge and slope of hydrograph rise. We show the dominant control on transient aquifer storage is antecedent stage, whereby lower stages result in greater magnitudes of transient aquifer storage. Our results suggest that measures of groundwater levels prior to an event can be useful in determining whether transient aquifer storage will occur and may provide a useful metric for improving predictions of flood magnitudes.

  4. Transient ischemic attack presenting in an elderly patient with transient ophthalmic manifestations

    Directory of Open Access Journals (Sweden)

    Sparshi Jain

    2016-01-01

    Full Text Available Transient ischemic attack (TIA is a transient neurological deficit of cerebrovascular origin without infarction which may last only for a short period and can have varying presentations. We report a case of 58-year-old male with presenting features of sudden onset transient vertical diplopia and transient rotatory nystagmus which self-resolved within 12 h. Patient had no history of any systemic illness. On investigating, hematological investigations and neuroimaging could not explain these sudden and transient findings. A TIA could possibly explain these sudden and transient ocular findings in our patient. This case report aims to highlight the importance of TIA for ophthalmologists. We must not ignore these findings as these could be warning signs of an impending stroke which may or may not be detected on neuroimaging. Thus, early recognition, primary prevention strategies, and timely intervention are needed.

  5. Transient analyzer

    International Nuclear Information System (INIS)

    Muir, M.D.

    1975-01-01

    The design and design philosophy of a high performance, extremely versatile transient analyzer is described. This sub-system was designed to be controlled through the data acquisition computer system which allows hands off operation. Thus it may be placed on the experiment side of the high voltage safety break between the experimental device and the control room. This analyzer provides control features which are extremely useful for data acquisition from PPPL diagnostics. These include dynamic sample rate changing, which may be intermixed with multiple post trigger operations with variable length blocks using normal, peak to peak or integrate modes. Included in the discussion are general remarks on the advantages of adding intelligence to transient analyzers, a detailed description of the characteristics of the PPPL transient analyzer, a description of the hardware, firmware, control language and operation of the PPPL transient analyzer, and general remarks on future trends in this type of instrumentation both at PPPL and in general

  6. Testing the ontogenetic base for the transient model of inflorescence development.

    Science.gov (United States)

    Bull-Hereñu, Kester; Claßen-Bockhoff, Regine

    2013-11-01

    Current research in plant science has concentrated on revealing ontogenetic processes of key attributes in plant evolution. One recently discussed model is the 'transient model' successful in explaining some types of inflorescence architectures based on two main principles: the decline of the so called 'vegetativeness' (veg) factor and the transient nature of apical meristems in developing inflorescences. This study examines whether both principles find a concrete ontogenetic correlate in inflorescence development. To test the ontogenetic base of veg decline and the transient character of apical meristems the ontogeny of meristematic size in developing inflorescences was investigated under scanning electron microscopy. Early and late inflorescence meristems were measured and compared during inflorescence development in 13 eudicot species from 11 families. The initial size of the inflorescence meristem in closed inflorescences correlates with the number of nodes in the mature inflorescence. Conjunct compound inflorescences (panicles) show a constant decrease of meristematic size from early to late inflorescence meristems, while disjunct compound inflorescences present an enlargement by merging from early inflorescence meristems to late inflorescence meristems, implying a qualitative change of the apical meristems during ontogeny. Partial confirmation was found for the transient model for inflorescence architecture in the ontogeny: the initial size of the apical meristem in closed inflorescences is consistent with the postulated veg decline mechanism regulating the size of the inflorescence. However, the observed biphasic kinetics of the development of the apical meristem in compound racemes offers the primary explanation for their disjunct morphology, contrary to the putative exclusive transient mechanism in lateral axes as expected by the model.

  7. Analytic models for fuel pin transient performance

    International Nuclear Information System (INIS)

    Bard, F.E.; Fox, G.L.; Washburn, D.F.; Hanson, J.E.

    1976-09-01

    HEDL's ability to analyze various mechanisms that operate within a fuel pin has progressed substantially through development of codes such as PECTCLAD, which solves cladding response, and DSTRESS, which solves fuel response. The PECTCLAD results show good correlation with a variety of mechanical tests on cladding material and also demonstrate the significance of cladding strength when applying the life fraction rule. The DSTRESS results have shown that fuel deforms sufficiently during overpower transient tests that available volumes are filled, whether in the form of a central cavity or start-up cracks

  8. Transient thermal driven bubble's surface and its potential ultrasound-induced damage

    Science.gov (United States)

    Movahed, Pooya; Freund, Jonathan B.

    2017-11-01

    Ultrasound-induced bubble activity in soft tissues is well-known to be a potential injury mechanism in therapeutic ultrasound treatments. We consider damage by transient thermal effects, including a hypothetical mechanism based on transient thermal phenomena, including viscous dissipation. A spherically symmetric compressible Navier-Stokes discretization is developed to solve the full governing equations, both inside and outside of the bubble, without the usual simplifications in the Rayleigh-Plesset bubble dynamics approach. Equations are solved in the Lagrangian framework, which provides a sharp and accurate representation of the interface as well as the viscous dissipation and thermal transport effects, which preclude reduction to the usual Rayleigh-Plesset ordinary differential equation. This method is used to study transient thermal effects at different frequencies and pressure amplitudes relevant to therapeutic ultrasound treatments. High temperatures achieved in the surrounding medium during the violent bubble collapse phase due to the viscous dissipation in the surrounding medium and thermal conduction from the bubble are expected to cause damage. This work was supported by NIH NIDDK Grant P01-DK043881.

  9. A luminous X-ray outburst from an intermediate-mass black hole in an off-centre star cluster

    Science.gov (United States)

    Lin, Dacheng; Strader, Jay; Carrasco, Eleazar R.; Page, Dany; Romanowsky, Aaron J.; Homan, Jeroen; Irwin, Jimmy A.; Remillard, Ronald A.; Godet, Olivier; Webb, Natalie A.; Baumgardt, Holger; Wijnands, Rudy; Barret, Didier; Duc, Pierre-Alain; Brodie, Jean P.; Gwyn, Stephen D. J.

    2018-06-01

    A unique signature for the presence of massive black holes in very dense stellar regions is occasional giant-amplitude outbursts of multi-wavelength radiation from tidal disruption and subsequent accretion of stars that make a close approach to the black holes1. Previous strong tidal disruption event (TDE) candidates were all associated with the centres of largely isolated galaxies2-6. Here, we report the discovery of a luminous X-ray outburst from a massive star cluster at a projected distance of 12.5 kpc from the centre of a large lenticular galaxy. The luminosity peaked at 1043 erg s-1 and decayed systematically over 10 years, approximately following a trend that supports the identification of the event as a TDE. The X-ray spectra were all very soft, with emission confined to be ≲3.0 keV, and could be described with a standard thermal disk. The disk cooled significantly as the luminosity decreased—a key thermal-state signature often observed in accreting stellar-mass black holes. This thermal-state signature, coupled with very high luminosities, ultrasoft X-ray spectra and the characteristic power-law evolution of the light curve, provides strong evidence that the source contains an intermediate-mass black hole with a mass tens of thousand times that of the solar mass. This event demonstrates that one of the most effective means of detecting intermediate-mass black holes is through X-ray flares from TDEs in star clusters.

  10. Improvement of the transient stability using SFCL in Korean power systems

    International Nuclear Information System (INIS)

    Hwang, Intae; Lee, Seung Ryul; Seo, Sangsoo; Yoon, Jaeyoung; Kim, Chul-Hwan

    2013-01-01

    Highlights: •In Korea, the Special Protection System is applied for protecting the power system. •Hybrid SFCL is protecting the power system from viewpoint of the transient stability. •Basic hybrid SFCL system cannot recover during the auto-reclosing operation. •This paper performs analysis of transient stability using the novel hybrid SFCL. -- Abstract: This paper proposed a novel hybrid SFCL system for the enhancement of the transient stability in Korean power transmission system with auto-reclosing operation. The proposed SFCL system has an operation mechanism that the current limiting impedance is eliminated from the power system in a fault clearing time for the enhancement of the transient stability. Also, the system can cover the auto-reclosing operation of the transmission power system. This study analyzed an improvement of the special protection system by applying the proposed SFCL system to real power system in Korea

  11. Final report for the H3 transient overpower failure threshold experiment

    International Nuclear Information System (INIS)

    Wright, A.E.; Rothman, A.B.; Stahl, D.; Agrawal, A.K.; Deitrich, L.W.; Chen, S.S.

    1975-06-01

    Test H3 was the first transient overpower failure-threshold experiment in TREAT to use irradiated fuel and to employ a TREAT transient shaped to produce sample-temperature distributions typical of steady state prior to the overpower excursion. A seven-pin assembly was tested within the Mark-II TREAT sodium loop. The experiment was performed successfully with satisfactory TREAT power transient and loop performance, and demonstrated the capability of intermediate-power EBR-II-irradiated fuel at low burnup (no central void) to withstand a mild overpower transient that terminated with fuel temperatures just short of the solidus without cladding strain. Calculated values of outlet coolant temperature and amount of molten fuel generally agree well with the test data. Posttest thermalhydraulic and mechanical analyses of the fuel pins are reported. Results of detailed nondestructive and destructive examinations of the preirradiated central pin and a fresh peripheral pin are presented. (U.S.)

  12. MECHANISMS GOVERNING TRANSIENTS FROM THE BATCH INCINERATION OF LIQUID WASTES IN ROTARY KILNS

    Science.gov (United States)

    When "containerized" liquid wastes, bound on sorbents. are introduced into a rotary kiln in a batch mode, transient phenomena in-volving heat transfer into, and waste mass transfer out of, the sorbent can oromote the raoid release of waste vaoor into the kiln environment. This ra...

  13. Transient drainage summary report

    International Nuclear Information System (INIS)

    1996-09-01

    This report summarizes the history of transient drainage issues on the Uranium Mill Tailings Remedial Action (UMTRA) Project. It defines and describes the UMTRA Project disposal cell transient drainage process and chronicles UMTRA Project treatment of the transient drainage phenomenon. Section 4.0 includes a conceptual cross section of each UMTRA Project disposal site and summarizes design and construction information, the ground water protection strategy, and the potential for transient drainage

  14. TRANSIENT ELECTRONICS CATEGORIZATION

    Science.gov (United States)

    2017-08-24

    AFRL-RY-WP-TR-2017-0169 TRANSIENT ELECTRONICS CATEGORIZATION Dr. Burhan Bayraktaroglu Devices for Sensing Branch Aerospace Components & Subsystems...SUBTITLE TRANSIENT ELECTRONICS CATEGORIZATION 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER N/A 5c. PROGRAM ELEMENT NUMBER N/A 6. AUTHOR(S) Dr. Burhan...88ABW-2017-3747, Clearance Date 31 July 2017. Paper contains color. 14. ABSTRACT Transient electronics is an emerging technology area that lacks proper

  15. Fuzzy Cognitive Maps for Glacier Hazards Assessment: Application to Predicting the Potential for Glacier Lake Outbursts

    Science.gov (United States)

    Furfaro, R.; Kargel, J. S.; Fink, W.; Bishop, M. P.

    2010-12-01

    Glaciers and ice sheets are among the largest unstable parts of the solid Earth. Generally, glaciers are devoid of resources (other than water), are dangerous, are unstable and no infrastructure is normally built directly on their surfaces. Areas down valley from large alpine glaciers are also commonly unstable due to landslide potential of moraines, debris flows, snow avalanches, outburst floods from glacier lakes, and other dynamical alpine processes; yet there exists much development and human occupation of some disaster-prone areas. Satellite remote sensing can be extremely effective in providing cost-effective and time- critical information. Space-based imagery can be used to monitor glacier outlines and their lakes, including processes such as iceberg calving and debris accumulation, as well as changing thicknesses and flow speeds. Such images can also be used to make preliminary identifications of specific hazardous spots and allows preliminary assessment of possible modes of future disaster occurrence. Autonomous assessment of glacier conditions and their potential for hazards would present a major advance and permit systematized analysis of more data than humans can assess. This technical leap will require the design and implementation of Artificial Intelligence (AI) algorithms specifically designed to mimic glacier experts’ reasoning. Here, we introduce the theory of Fuzzy Cognitive Maps (FCM) as an AI tool for predicting and assessing natural hazards in alpine glacier environments. FCM techniques are employed to represent expert knowledge of glaciers physical processes. A cognitive model embedded in a fuzzy logic framework is constructed via the synergistic interaction between glaciologists and AI experts. To verify the effectiveness of the proposed AI methodology as applied to predicting hazards in glacier environments, we designed and implemented a FCM that addresses the challenging problem of autonomously assessing the Glacier Lake Outburst Flow

  16. A curious fact: Photic sneeze reflex. Autosomical dominant compelling helio-ophthalmic outburst syndrome.

    Science.gov (United States)

    Sevillano, C; Parafita-Fernández, A; Rodriguez-Lopez, V; Sampil, M; Moraña, N; Viso, E; Cores, F J

    2016-07-01

    To assess ocular involvement in the pathophysiology of autosomal dominant compelling helio-ophthalmic outburst syndrome (ACHOOs). An interview was conducted with a Caucasian family that showed clinical features of ACHOOs. Twelve of them had photic reflex and were recruited. A complete eye evaluation was made. A dominant autosomal inheritance with mild penetrance was demonstrated, with 67% of the studied subjects showing some degree of prominent corneal nerves. No other eye changes were found. Prominent corneal nerves may be associated with ACHOOs. The other eye structures studied do not seem to play a role in ACHOOs. Further studies are needed to understand the physiology of the ACHOOs. Copyright © 2016 Sociedad Española de Oftalmología. Published by Elsevier España, S.L.U. All rights reserved.

  17. Transient subcritical crack-growth behavior in transformation-toughened ceramics

    International Nuclear Information System (INIS)

    Dauskardt, R.H.; Ritchie, R.O.; Carter, W.C.; Veirs, D.K.

    1990-01-01

    Transient subcritical crack-growth behavior following abrupt changes in the applied load are studied in transformation-toughened ceramics. A mechanics analysis is developed to model the transient nature of transformation shielding of the crack tip, K s , with subcritical crack extension following the applied load change. conditions for continued crack growth, crack growth followed by arrest, and no crack growth after the load change, are considered and related to the magnitude and sign of the applied load change and to materials properties such as the critical transformation stress. The analysis is found to provide similar trends in K s compared to values calculated from experimentally measured transformation zones in a transformation-toughened Mg-PSZ. In addition, accurate prediction of the post load-change transient crack-growth behavior is obtained using experimentally derived steady-state subcritical crack-growth relationships for cyclic fatigue in the same material

  18. Theoretical basis for a transient thermal elastic-plastic stress analysis of nuclear reactor fuel elements

    International Nuclear Information System (INIS)

    Hsu, T.R.; Bertels, A.W.M.; Banerjee, S.; Harrison, W.C.

    1976-07-01

    This report presents the theoretical basis for a transient thermal elastic-plastic stress analysis of a nuclear reactor fuel element subject to severe transient thermo-mechanical loading. A finite element formulation is used for both the non-linear stress analysis and thermal analysis. These two major components are linked together to form an integrated program capable of predicting fuel element transient behaviour in two dimensions. Specific case studies are presented to illustrate capabilities of the analysis. (author)

  19. The Fall and the Rise of X-Rays from Dwarf Novae in Outburst: RXTE Observations of VW Hydri and WW Ceti

    Science.gov (United States)

    Fertig, D.; Mukai, K.; Nelson, T.; Cannizzo, J. K.

    2011-01-01

    In a dwarf nova, the accretion disk around the white dwarf is a source of ultraviolet, optical, and infrared photons, but is never hot enough to emit X-rays. Observed X-rays instead originate from the boundary layer between the disk and the white dwarf. As the disk switches between quiescence and outburst states, the 2-10 keV X-ray flux is usually seen to be anti-correlated with the optical brightness. Here we present RXTE monitoring observations of two dwarf novae, VW Hyi and WW Cet, confirming the optical/X-ray anti-correlation in these two systems. However, we do not detect any episodes of increased hard X-ray flux on the rise (out of two possible chances for WW Cet) or the decline (two for WW Cet and one for VW Hyi) from outburst, attributes that are clearly established in SS Cyg. The addition of these data to the existing literature establishes the fact that the behavior of SS Cyg is the exception, rather than the archetype as is often assumed. We speculate that only dwarf novae with a massive white dwarf may show these hard X-ray spikes.

  20. Recurrent transient thyrotoxicosis in multinodular goitre.

    OpenAIRE

    Arem, R.

    1990-01-01

    A patient initially presented with an autonomously functioning right thyroid nodule and transient hyperthyroidism which lasted for a few months. Several months after resolution of thyrotoxicosis, the patient had a recurrent episode of hyperthyroidism and was found to have a left hot nodule. The right hyperfunctioning nodule had become cold on scintigraphy, and its aspiration revealed haemorrhagic fluid suggesting haemorrhagic infarction as the mechanism of resolution of the first episode of h...

  1. Transient and steady-state selection in the striatal microcircuit

    Directory of Open Access Journals (Sweden)

    Adam eTomkins

    2014-01-01

    Full Text Available Although the basal ganglia have been widely studied and implicated in signal processing and action selection, little information is known about the active role the striatal microcircuit plays in action selection in the basal ganglia-thalamo-cortical loops. To address this knowledge gap we use a large scale three dimensional spiking model of the striatum, combined with a rate coded model of the basal ganglia-thalamo-cortical loop, to asses the computational role the striatum plays in action selection. We identify a robust transient phenomena generated by the striatal microcircuit, which temporarily enhances the difference between two competing cortical inputs. We show that this transient is sufficient to modulate decision making in the basal ganglia-thalamo-cortical circuit. We also find that the transient selection originates from a novel adaptation effect in single striatal projection neurons, which is amenable to experimental testing. Finally, we compared transient selection with models implementing classical steady-state selection. We challenged both forms of model to account for recent reports of paradoxically enhanced response selection in Huntington's Disease patients. We found that steady-state selection was uniformly impaired under all simulated Huntington's conditions, but transient selection was enhanced given a sufficient Huntington's-like increase in NMDA receptor sensitivity. Thus our models provide an intriguing hypothesis for the mechanisms underlying the paradoxical cognitive improvements in manifest Huntington's patients.

  2. Transient receptor potential channel polymorphisms are associated with the somatosensory function in neuropathic pain patients.

    Directory of Open Access Journals (Sweden)

    Andreas Binder

    Full Text Available Transient receptor potential channels are important mediators of thermal and mechanical stimuli and play an important role in neuropathic pain. The contribution of hereditary variants in the genes of transient receptor potential channels to neuropathic pain is unknown. We investigated the frequency of transient receptor potential ankyrin 1, transient receptor potential melastin 8 and transient receptor potential vanilloid 1 single nucleotide polymorphisms and their impact on somatosensory abnormalities in neuropathic pain patients. Within the German Research Network on Neuropathic Pain (Deutscher Forscbungsverbund Neuropathischer Schmerz 371 neuropathic pain patients were phenotypically characterized using standardized quantitative sensory testing. Pyrosequencing was employed to determine a total of eleven single nucleotide polymorphisms in transient receptor potential channel genes of the neuropathic pain patients and a cohort of 253 German healthy volunteers. Associations of quantitative sensory testing parameters and single nucleotide polymorphisms between and within groups and subgroups, based on sensory phenotypes, were analyzed. Single nucleotide polymorphisms frequencies did not differ between both the cohorts. However, in neuropathic pain patients transient receptor potential ankyrin 1 710G>A (rs920829, E179K was associated with the presence of paradoxical heat sensation (p = 0.03, and transient receptor potential vanilloid 1 1911A>G (rs8065080, I585V with cold hypoalgesia (p = 0.0035. Two main subgroups characterized by preserved (1 and impaired (2 sensory function were identified. In subgroup 1 transient receptor potential vanilloid 1 1911A>G led to significantly less heat hyperalgesia, pinprick hyperalgesia and mechanical hypaesthesia (p = 0.006, p = 0.005 and pG (rs222747, M315I to cold hypaesthesia (p = 0.002, but there was absence of associations in subgroup 2. In this study we found no evidence that genetic

  3. PSH Transient Simulation Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Muljadi, Eduard [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2017-12-21

    PSH Transient Simulation Modeling presentation from the WPTO FY14 - FY16 Peer Review. Transient effects are an important consideration when designing a PSH system, yet numerical techniques for hydraulic transient analysis still need improvements for adjustable-speed (AS) reversible pump-turbine applications.

  4. Transient temperature response of in-vessel components due to pulsed operation in tokamak fusion experimental reactor (FER)

    International Nuclear Information System (INIS)

    Minato, Akio; Tone, Tatsuzo

    1985-12-01

    A transient temperature response of the in-vessel components (first wall, blanket, divertor/limiter and shielding) surrounding plasma in Tokamak Fusion Experimental Reactor (FER) has been analysed. Transient heat load during start up/shut down and pulsed operation cycles causes the transient temperature response in those components. The fatigue lifetime of those components significantly depends upon the resulting cyclic thermal stress. The burn time affects the temperature control in the solid breeder (Li 2 O) and also affects the thermo-mechanical design of the blanket and shielding which are constructed with thick structure. In this report, results of the transient temperature response obtained by the heat transfer and conduction analyses for various pulsed operation scenarios (start up, shut down, burn and dwell times) have been investigated in view of thermo-mechanical design of the in-vessel components. (author)

  5. Cortical computations via transient attractors.

    Science.gov (United States)

    Rourke, Oliver L C; Butts, Daniel A

    2017-01-01

    The ability of sensory networks to transiently store information on the scale of seconds can confer many advantages in processing time-varying stimuli. How a network could store information on such intermediate time scales, between typical neurophysiological time scales and those of long-term memory, is typically attributed to persistent neural activity. An alternative mechanism which might allow for such information storage is through temporary modifications to the neural connectivity which decay on the same second-long time scale as the underlying memories. Earlier work that has explored this method has done so by emphasizing one attractor from a limited, pre-defined set. Here, we describe an alternative, a Transient Attractor network, which can learn any pattern presented to it, store several simultaneously, and robustly recall them on demand using targeted probes in a manner reminiscent of Hopfield networks. We hypothesize that such functionality could be usefully embedded within sensory cortex, and allow for a flexibly-gated short-term memory, as well as conferring the ability of the network to perform automatic de-noising, and separation of input signals into distinct perceptual objects. We demonstrate that the stored information can be refreshed to extend storage time, is not sensitive to noise in the system, and can be turned on or off by simple neuromodulation. The diverse capabilities of transient attractors, as well as their resemblance to many features observed in sensory cortex, suggest the possibility that their actions might underlie neural processing in many sensory areas.

  6. THYROID FUNCTION Quitting smoking-transient risk of autoimmune hypothyroidism

    NARCIS (Netherlands)

    Wiersinga, Wilmar M.

    2012-01-01

    Smoking is a risk factor for Graves disease. However, Carle et al. have demonstrated that individuals have a transient increased risk of developing overt autoimmune hypothyroidism in the first 2 years after quitting smoking. The mechanisms involved in these two opposing effects of smoking on the

  7. TS-1 and TS-2 transient overpower tests on FFTF fuel

    International Nuclear Information System (INIS)

    Pitner, A.L.; Ferrell, P.C.; Culley, G.E.; Weber, E.T.

    1985-01-01

    The TS-1 and TS-2 TREAT transient experiments subjected a low burnup (2 MWd/kg) and a medium burnup (58 MWd/kg), respectively, FFTF irradiated fuel pin to unprotected 5 cents/s overpower transient conditions. The fuel pin failure response was similar in the two tests, which demonstrated a large margin to failure (P/P 0 > 3) and a favorable upper level failure location. Thus, for these transient conditions, burnup effects on transient performance appeared to be minimal in the range tested. Pin disruption in the medium burnup TS-2 test was more severe due to the higher fission gas pressurization, but failure occurred at only a 5% lower power level than for the low burnup TS-1 fuel pin. Both tests exhibited axial extrusion of molten fuel to the region above the fuel column several seconds before pin failure, demonstrating a potentially beneficial inherent safety mechanism to delay failure and mitigate accident consequences

  8. Transient global amnesia: current perspectives

    Directory of Open Access Journals (Sweden)

    Spiegel DR

    2017-10-01

    Full Text Available David R Spiegel, Justin Smith, Ryan R Wade, Nithya Cherukuru, Aneel Ursani, Yuliya Dobruskina, Taylor Crist, Robert F Busch, Rahim M Dhanani, Nicholas Dreyer Department of Psychiatry and Behavioral Sciences, Eastern Virginia Medical School, Norfolk, VA, USA Abstract: Transient global amnesia (TGA is a clinical syndrome characterized by the sudden onset of an extraordinarily large reduction of anterograde and a somewhat milder reduction of retrograde episodic long-term memory. Additionally, executive functions are described as diminished. Although it is suggested that various factors, such as migraine, focal ischemia, venous flow abnormalities, and epileptic phenomena, are involved in the pathophysiology and differential diagnosis of TGA, the factors triggering the emergence of these lesions are still elusive. Recent data suggest that the vulnerability of CA1 neurons to metabolic stress plays a pivotal part in the pathophysiological cascade, leading to an impairment of hippocampal function during TGA. In this review, we discuss clinical aspects, new imaging findings, and recent clinical–epidemiological data with regard to the phenotype, functional anatomy, and putative cellular mechanisms of TGA. Keywords: transient global amnesia, vascular, migraines, psychiatric

  9. Towards a mechanistic understanding of transient fission gas release

    International Nuclear Information System (INIS)

    Matthews, J.R.; Small, G.J.

    1989-01-01

    Recent experimental results on transient fission gas release from oxide fuels are briefly reviewed. These together with associated microstructural observations are compared with the main models for fission gas behaviour. Single gas atom diffusion, bubble migration, heterogeneous percolation and grain boundary sweeping are examined as possible release mechanisms. The role of gas trapping in bubbles and re-solution by irradiation and thermal processes are included in the comparison. As much of the data, and the main range of interest for light water reactor fuels, is for release during mild transients in fuel with a burn-up below 4%, the role of gas retention on grain boundaries is very important and in some cases dominant. The grain boundaries are found to respond very differently to various gas arrival rates and to local temperature conditions. This can lead to early interlinkage and release in some cases, but retention with accompanying large swelling in others. The role of fission products and the local oxygen content of the fuel are found to be important. The effective fuel stoichiometry is likely to change significantly during transients with substantial effects on the transport processes controlling fission gas behaviour. The results of the evaluation of the models are summarized in mechanism maps for intragranular and grain boundary behaviour. (author). 36 refs, 8 figs

  10. Climate Change Adaptation Decision Making for Glacial Lake Outburst Floods From Palcacocha Lake in Peru

    Science.gov (United States)

    Cuellar, A. D.; McKinney, D. C.

    2014-12-01

    Climate change has accelerated glacial retreat in high altitude glaciated regions of Peru leading to the growth and formation of glacier lakes. Glacial lake outburst floods (GLOF) are sudden events triggered by an earthquake, avalanche into the lake or other shock that causes a sudden outflow of water. These floods are catastrophic because of their sudden onset, the difficulty predicting them, and enormous quantity of water and debris rapidly flooding downstream areas. Palcacocha Lake in the Peruvian Andes has experienced accelerated growth since it burst in 1941 and threatens the major city of Huaraz and surrounding communities. Since the 1941 flood stakeholders have advocated for projects to adapt to the increasing threat posed by Palcacocha Lake. Nonetheless, discussions surrounding projects for Palcacocha have not included a rigorous analysis of the potential consequences of a flood, probability of an event, or costs of mitigation projects. This work presents the first step to rationally analyze the risks posed by Palcacocha Lake and the various adaptation projects proposed. In this work the authors use decision analysis to asses proposed adaptation measures that would mitigate damage in downstream communities from a GLOF. We use an existing hydrodynamic model of the at-risk area to determine how adaptation projects will affect downstream flooding. Flood characteristics are used in the HEC-FIA software to estimate fatalities and injuries from an outburst flood, which we convert to monetary units using the value of a statistical life. We combine the monetary consequences of a GLOF with the cost of the proposed projects and a diffuse probability distribution for the likelihood of an event to estimate the expected cost of the adaptation plans. From this analysis we found that lowering the lake level by 15 meters has the least expected cost of any proposal despite uncertainty in the effect of lake lowering on flooding downstream.

  11. Transient analysis on the SMART-P anticipated transients without scram

    International Nuclear Information System (INIS)

    Yang, S. H.; Bae, K. H.; Kim, H. C.; Zee, S. Q.

    2005-01-01

    Anticipated transients without scram (ATWS) are anticipated operational occurrences accompanied by a failure of an automatic reactor trip when required. Although the occurrence probability of the ATWS events is considerably low, these events can result in unacceptable consequences, i.e. the pressurization of the reactor coolant system (RCS) up to an unacceptable range and a core-melting situation. Therefore, the regulatory body requests the installation of a protection system against the ATWS events. According to the request, a diverse protection system (DPS) is installed in the SMART-P (System-integrated Modular Advanced ReacTor-Pilot). This paper presents the results of the transient analysis performed to identify the performance of the SMART-P against the ATWS. In the analysis, the TASS/SMR (Transients And Setpoint Simulation/Small and Medium Reactor) code is applied to identify the thermal hydraulic response of the RCS during the transients

  12. The Evolution of the Phase Lags Associated with the Type-C Quasi-periodic Oscillation in GX 339-4 during the 2006/2007 Outburst

    NARCIS (Netherlands)

    Zhang, Liang; Wang, Yanan; Méndez, Mariano; Chen, Li; Qu, Jinlu; Altamirano, Diego; Belloni, Tomaso

    2017-01-01

    We present the evolution of the phase lags associated with the type-C QPO in GX 339-4 during the rising phase of the 2006/2007 outburst. We find that the phase lags at the QPO frequency are always positive (hard) and show very different behavior between QPOs with frequencies below and above ˜1.7 Hz:

  13. An investigation on microstructure evolution and mechanical properties during transient liquid phase bonding of stainless steel 316L to Ti–6Al–4V

    Energy Technology Data Exchange (ETDEWEB)

    Zakipour, Shahrokh [Department of Materials Engineering, Tehran Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Halvaee, Ayoub; Amadeh, Ahmad Ali [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Samavatian, Majid, E-mail: m.samavatian@srbiau.ac.ir [Department of Materials Engineering, Tehran Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Khodabandeh, Alireza [Department of Materials Engineering, Tehran Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of)

    2015-03-25

    Highlights: • Transient liquid phase bonding of SS316L to Ti–6Al–4V was studied. • A vacuum furnace was used to prevent oxidation during the bonding process. • Diffusion of Fe, Cu and Ti at the interface led to formation of eutectic phases. • The maximum shear strength reached to 220 MPa for the bond with 50 μm thick interlayer at 900 °C. - Abstract: Transient liquid phase bonding mechanism of two dissimilar alloys stainless steel 316L and Ti–6Al–4V using pure Cu interlayer with different thicknesses was studied. In order to characterize the microstructure and compositional changes in the joint zone, scanning electron microscopy equipped with energy dispersive spectroscopy and X-ray diffraction have been applied. Microhardness and shear strength tests have been performed to investigate mechanical properties of the joints. The results showed that there are various intermetallic compounds at the interface caused by interdiffusion of Ti, Fe and Cu across the joint zone. Furthermore, increasing the interlayer thickness led to incompletion of bonding process in 60 min. The maximum shear strength of 220 MPa has been attained for the bond made at 900 °C. With the rise in bonding temperature to 960 °C, a reduction in bond strength occurs attributed to increase in width of joint zone and formation of more brittle intermetallic compounds at the interface.

  14. An investigation on microstructure evolution and mechanical properties during transient liquid phase bonding of stainless steel 316L to Ti–6Al–4V

    International Nuclear Information System (INIS)

    Zakipour, Shahrokh; Halvaee, Ayoub; Amadeh, Ahmad Ali; Samavatian, Majid; Khodabandeh, Alireza

    2015-01-01

    Highlights: • Transient liquid phase bonding of SS316L to Ti–6Al–4V was studied. • A vacuum furnace was used to prevent oxidation during the bonding process. • Diffusion of Fe, Cu and Ti at the interface led to formation of eutectic phases. • The maximum shear strength reached to 220 MPa for the bond with 50 μm thick interlayer at 900 °C. - Abstract: Transient liquid phase bonding mechanism of two dissimilar alloys stainless steel 316L and Ti–6Al–4V using pure Cu interlayer with different thicknesses was studied. In order to characterize the microstructure and compositional changes in the joint zone, scanning electron microscopy equipped with energy dispersive spectroscopy and X-ray diffraction have been applied. Microhardness and shear strength tests have been performed to investigate mechanical properties of the joints. The results showed that there are various intermetallic compounds at the interface caused by interdiffusion of Ti, Fe and Cu across the joint zone. Furthermore, increasing the interlayer thickness led to incompletion of bonding process in 60 min. The maximum shear strength of 220 MPa has been attained for the bond made at 900 °C. With the rise in bonding temperature to 960 °C, a reduction in bond strength occurs attributed to increase in width of joint zone and formation of more brittle intermetallic compounds at the interface

  15. Effects of neutron irradiation on mechanical properties of silicon carbide composites fabricated by nano-infiltration and transient eutectic-phase process

    International Nuclear Information System (INIS)

    Koyanagi, T.; Hinoki, T.; Shimoda, K.; Ozawa, K.; Katoh, Y.

    2014-01-01

    Unidirectional silicon carbide (SiC)-fiber-reinforced SiC matrix (SiC/SiC) composites fabricated by a nano-infiltration and transient eutectic-phase (NITE) process were irradiated with neutrons at 830°C to 5.9 dpa, and at 1270°C to 5.8 dpa. The in-plane and trans-thickness tensile and the inter-laminar shear properties were evaluated at ambient temperature. The mechanical characteristics, including the quasi-ductile behavior, the proportional limit stress, and the ultimate tensile strength, were retained subsequent to irradiation. Analysis of the stress–strain hysteresis loop indicated the increased fiber/matrix interface friction and the decreased residual stresses. The inter-laminar shear strength exhibited a significant decrease following irradiation. (author)

  16. Transient Fuel Behavior and Failure Condition in the CABRI-2 Experiments

    International Nuclear Information System (INIS)

    Sato, Ikken; Lemoine, Francette; Struwe, Dankward

    2004-01-01

    In the CABRI-2 program, 12 tests were performed under various transient conditions covering a wide range of accident scenarios using two types of preirradiated fast breeder reactor (FBR) fuel pins with different smear densities and burnups. For each fuel, a nonfailure-transient test was performed, and it provided basic information such as fuel thermal condition, fuel swelling, and gas release. From the failure tests, information on failure mode, failure time, and axial location was obtained. Based on this information, failure conditions such as fuel enthalpy and cladding temperature were evaluated. These failure conditions were compared with the CABRI-1 tests in which different fuels as well as different transient conditions were used. This comparison, together with supporting information available from existing in-pile and out-of-pile experiments, allowed an effective understanding on failure mechanisms depending on fuel and transient conditions. It is concluded that pellet-cladding mechanical interaction (PCMI) due to fuel thermal expansion and fission-gas-induced swelling is playing an important role on mechanical clad loading especially with high smear density and low fuel-heating-rate conditions. At very high heating-rate conditions, there is no sufficient time to allow significant fuel swelling, so that cavity pressurization with fuel melting becomes the likely failure mechanism. Fuel smear density and fission-gas retention have a strong impact both on PCMI and cavity pressurization. Furthermore, pin failure is strongly dependent on cladding temperature, which plays an important role in the axial failure location. With the low smear-density fuel, considerable PCMI mitigation is possible leading to a high failure threshold as well as in-pin molten-fuel relocation along the central hole. However, even with the low smear density fuel, PCMI failure could take place with an elevated cladding-temperature condition. On the other hand, in case of a sufficiently long

  17. Influence of transient flooding on methane fluxes from subtropical pastures

    Science.gov (United States)

    Seasonally flooded subtropical pastures are major methane (CH4) sources, where transient flooding drives episodic and high-magnitude emissions from the underlying landscape. Understanding the mechanisms that drive these patterns is needed to better understand pasture CH4 emissions and their response...

  18. Transient analysis of mercury experimental loop using the RELAP5 code. 3rd report. Transient analysis using mercury properties

    International Nuclear Information System (INIS)

    Kinoshita, Hidetaka; Kaminaga, Masanori; Hino, Ryutaro

    2000-02-01

    In order to promote the Neutron Science Project of JAERI, the design of a 5MW-spallation target system is in progress with the purpose of producing a practical neutron application while at the same time adhering to the highest levels of safety. To establish the safety of the target system, it is important to understand the transient behaviors during anticipated operational events of the system, and to design the safety protection systems for the safe termination of the transients. This report presents the analytical results of transient behaviors in the mercury experimental loop using mercury properties. At first, the analytical pressure distributions were compared with experimental data measured with the mercury experimental loop. The modeling data were modified to reproduce the actual pressure distributions of the mercury experimental loop. Then a loss of forced convection and a loss of coolant accident were analyzed. In the case of the pump trip, the transient analysis was conducted using two types of mercury pumps, the mechanical type pump with moment of inertia, and the electrical-magnetic type pump without moment of inertia. The results show there was no clear difference in the two analyses, since the mercury had a large inertia, which was 13.5 times that of the water. Moreover, in the case of a pipe rupture at the pump exit, a moderate pressure decrease was confirmed when a small breakage area existed in which the coolant flowed out gradually. Based on these results, it was appeared that the transient fluctuation of pressure in the mercury loop would not become large and accidents would have to be detected by small fluctuations in pressure. Based on these analyses, we plan to conduct a simulation test to verify the RELAP5 code, and then the analysis of a full-scale mercury system will be performed. (author)

  19. Transient absorption study of two-photon excitation mechanism in the LH2 complex from purple bacterium Rhodobacter sphaeroides.

    Science.gov (United States)

    Stepanenko, Ilya; Kompanetz, Viktor; Makhneva, Zoya; Chekalin, Sergey; Moskalenko, Andrei; Razjivin, Andrei

    2012-03-08

    The mechanism of two-photon excitation of a peripheral light-harvesting complex LH2 (B800-850) from purple bacterium Rhodobacter sphaeroides was explained on the basis of femtosecond transient absorption data. Fast bleaching of the B850 absorption band was measured under two-photon excitation by 1350 nm femtosecond pulses, showing fast subpicosecond arrival of excitation energy to B850 circular aggregates. Any spectral changes connected with the B800 absorption band of B800-BChl molecules were absent. A similar picture was observed under one-photon excitation of the LH2 complex by 675 nm femtosecond pulses. We believe these effects may be attributed to direct excitation of high-energy excitonic states of a B850 circular aggregate or its vibrational manifold in accordance with the model of Abe [Chem. Phys. 2001, 264, 355-363].

  20. Transient flow combustion

    Science.gov (United States)

    Tacina, R. R.

    1984-01-01

    Non-steady combustion problems can result from engine sources such as accelerations, decelerations, nozzle adjustments, augmentor ignition, and air perturbations into and out of the compressor. Also non-steady combustion can be generated internally from combustion instability or self-induced oscillations. A premixed-prevaporized combustor would be particularly sensitive to flow transients because of its susceptability to flashback-autoignition and blowout. An experimental program, the Transient Flow Combustion Study is in progress to study the effects of air and fuel flow transients on a premixed-prevaporized combustor. Preliminary tests performed at an inlet air temperature of 600 K, a reference velocity of 30 m/s, and a pressure of 700 kPa. The airflow was reduced to 1/3 of its original value in a 40 ms ramp before flashback occurred. Ramping the airflow up has shown that blowout is more sensitive than flashback to flow transients. Blowout occurred with a 25 percent increase in airflow (at a constant fuel-air ratio) in a 20 ms ramp. Combustion resonance was found at some conditions and may be important in determining the effects of flow transients.

  1. Overshoot mechanism in transient excitation of THz and Gunn oscillations in wide-bandgap semiconductors

    Science.gov (United States)

    Momox, Ernesto; Zakhleniuk, Nick; Balkan, Naci

    2012-11-01

    A detailed study of high-field transient and direct-current (DC) transport in GaN-based Gunn diode oscillators is carried out using the commercial simulator Sentaurus Device. Applicability of drift-diffusion (DD) and hydrodynamic (HD) models to high-speed, high-frequency devices is discussed in depth, and the results of the simulations from these models are compared. It is shown, for a highly homogeneous device based on a short (2 μm) supercritically doped (1017 cm-3) GaN specimen, that the DD model is unable to correctly take into account some essential physical effects which determine the operation mode of the device. At the same time, the HD model is ideally suited to solve such problems due to its ability to incorporate non-local effects. We show that the velocity overshoot near the device contacts and space charge injection and extraction play a crucial role in defining the operation mode of highly homogeneous short diodes in both the transient regime and the voltage-controlled oscillation regime. The transient conduction current responses are fundamentally different in the DD and HD models. The DD current simply repeats the velocity-field (v-F) characteristics, and the sample remains in a completely homogeneous state. In the HD model, the transient current pulse with a full width at half maximum of approximately 0.2 ps is increased about twofold due to the carrier injection (extraction) into (from) the active region and the velocity overshoot. The electron gas is characterized by highly inhomogeneous distributions of the carrier density, the electric field and the electron temperature. The simulation of the DC steady states of the diodes also shows very different results for the two models. The HD model shows the trapped stable anodic domain in the device, while the DD model completely retains all features of the v-F characteristics in a homogeneous gas. Simulation of the voltage-controlled oscillator shows that it operates in the accumulation layer mode

  2. Structure and dynamics of paramagnetic transients by pulsed EPR and NMR detection of nuclear resonance

    International Nuclear Information System (INIS)

    Trifunac, A.D.

    1981-01-01

    Structure and dynamics of transient radicals in pulse radiolysis can be studied by time resolved EPR and NMR techniques. EPR study of kinetics and relaxation is illustrated. The NMR detection of nuclear resonance in transient radicals is a new method which allows the study of hyperfine coupling, population dynamics, radical kinetics, and reaction mechanism. 9 figures

  3. Mechanisms of ignition by transient energy deposition: Regimes of combustion wave propagation

    OpenAIRE

    Kiverin, A. D.; Kassoy, D. R.; Ivanov, M. F.; Liberman, M. A.

    2013-01-01

    Regimes of chemical reaction wave propagating in reactive gaseous mixtures, whose chemistry is governed by chain-branching kinetics, are studied depending on the characteristics of a transient thermal energy deposition localized in a finite volume of reactive gas. Different regimes of the reaction wave propagation are initiated depending on the amount of deposited thermal energy, power of the source, and the size of the hot spot. The main parameters which define regimes of the combustion wave...

  4. Application of transient magnetic field to the measurement of nuclear magnetic moments

    International Nuclear Information System (INIS)

    Ribas, R.V.

    1987-01-01

    A review on: the mechanism for producing transient magnetic field; techniques for measuring nuclear gyromagnetic factor; and some examples of recent measurements using this technique is presented. (M.C.K.) [pt

  5. A hybrid superconducting fault current limiter for enhancing transient stability in Korean power systems

    Science.gov (United States)

    Seo, Sangsoo; Kim, Seog-Joo; Moon, Young-Hwan; Lee, Byongjun

    2013-11-01

    Additional power generation sites have been limited in Korea, despite the fact load demands are gradually increasing. In order to meet these increasing demands, Korea’s power system company has begun constructing new generators at existing sites. Thus, multi-unit plants can create problems in terms of transient stability when a large disturbance occurs. This paper proposes a hybrid superconducting fault current limiter (SFCL) application to enhance the transient stability of multi-unit power plants. SFCLs reduce fault currents, and limitation currents decrease the imbalance of the mechanical and electrical torque of the generators, resulting in an improvement in transient stability.

  6. Transient fuel rod behavior prediction with RODEX-3/SIERRA

    Energy Technology Data Exchange (ETDEWEB)

    Billaux, M R; Shann, S H; Swam, L.F. Van [Siemens Power Corp., Richland, WA (United States)

    1997-08-01

    This paper discusses some aspects of the fuel performance code SIERRA (SIEmens Rod Response Analysis). SIERRA, the latest version of the code RODEX-3, has been developed to improve the fuel performance prediction capabilities of the code, both at high burnup and during transient reactor conditions. The paper emphasizes the importance of the mechanical models of the cracked pellet and of the cladding, in the prediction of the transient response of the fuel rod to power changes. These models are discussed in detail. Other aspects of the modelling of high burnup effects are also presented, in particular the modelling of the rim effect and the way it affects the fuel temperature. (author). 12 refs, 5 figs.

  7. Transient fuel rod behavior prediction with RODEX-3/SIERRA

    International Nuclear Information System (INIS)

    Billaux, M.R.; Shann, S.H.; Swam, L.F. Van

    1997-01-01

    This paper discusses some aspects of the fuel performance code SIERRA (SIEmens Rod Response Analysis). SIERRA, the latest version of the code RODEX-3, has been developed to improve the fuel performance prediction capabilities of the code, both at high burnup and during transient reactor conditions. The paper emphasizes the importance of the mechanical models of the cracked pellet and of the cladding, in the prediction of the transient response of the fuel rod to power changes. These models are discussed in detail. Other aspects of the modelling of high burnup effects are also presented, in particular the modelling of the rim effect and the way it affects the fuel temperature. (author). 12 refs, 5 figs

  8. The mechanism of the transient depression of the erythropoietic rate induced in the rat by a single injection of uranyl nitrate

    International Nuclear Information System (INIS)

    Giglio, M.J.; Brandan, N.; Leal, T.L.; Bozzini, C.E.

    1989-01-01

    With the purpose of assessing the effect of uranyl nitrate (UN) on the rate of erythropoiesis, 1 mg/kg of the compound was injected iv to adult female Wistar rats. The dosing vehicle was injected into control animals. A single injection of UN induced a transient depression of the rate of red cell volume 59 Fe uptake, which reached its lowest value (68% depression) by the seventh postinjection day. By 14 days, 59 Fe incorporation had returned to normal. The amount of iron going to erythroid tissue per hour, reticulocyte count, and immunoreactive erythropoietin concentration in both plasma and kidney extracts were also significantly depressed in UN-treated rats in relation to these values in vehicle-injected rats by the seventh postinjection day. Dose-response curves for exogenous erythropoietin (Epo) performed in polycythemic intact and UN-treated rats 7 days after drug injection revealed a significant depression of the response in UN-injected animals. Moreover, bone marrow cells obtained from rats pretreated with UN formed a reduced number of erythroid colonies in vitro in response to Epo. Therefore, possible mechanisms for the observed transient depression in the rate of erythropoiesis associated with acute UN treatment include decreased Epo production and direct or indirect damage of erythroid progenitor cells

  9. An Optical and Infrared Time-domain Study of the Supergiant Fast X-Ray Transient Candidate IC 10 X-2

    Science.gov (United States)

    Kwan, Stephanie; Lau, Ryan M.; Jencson, Jacob; Kasliwal, Mansi M.; Boyer, Martha L.; Ofek, Eran; Masci, Frank; Laher, Russ

    2018-03-01

    We present an optical and infrared (IR) study of IC 10 X-2, a high-mass X-ray binary in the galaxy IC 10. Previous optical and X-ray studies suggest that X-2 is a Supergiant Fast X-ray Transient: a large-amplitude (factor of ∼100), short-duration (hours to weeks) X-ray outburst on 2010 May 21. We analyze R- and g-band light curves of X-2 from the intermediate Palomar Transient Factory taken between 2013 July 15 and 2017 February 14 that show high-amplitude (≳1 mag), short-duration (≲8 days) flares and dips (≳0.5 mag). Near-IR spectroscopy of X-2 from Palomar/TripleSpec show He I, Paschen-γ, and Paschen-β emission lines with similar shapes and amplitudes as those of luminous blue variables (LBVs) and LBV candidates (LBVc). Mid-IR colors and magnitudes from Spitzer/Infrared Array Camera photometry of X-2 resemble those of known LBV/LBVcs. We suggest that the stellar companion in X-2 is an LBV/LBVc and discuss possible origins of the optical flares. Dips in the optical light curve are indicative of eclipses from optically thick clumps formed in the winds of the stellar counterpart. Given the constraints on the flare duration (0.02–0.8 days) and the time between flares (15.1 ± 7.8 days), we estimate the clump volume filling factor in the stellar winds, f V , to be 0.01interpret the origin of the optical flares as the accretion of clumps formed in the winds of an LBV/LBVc onto the compact object.

  10. Cortical computations via transient attractors.

    Directory of Open Access Journals (Sweden)

    Oliver L C Rourke

    Full Text Available The ability of sensory networks to transiently store information on the scale of seconds can confer many advantages in processing time-varying stimuli. How a network could store information on such intermediate time scales, between typical neurophysiological time scales and those of long-term memory, is typically attributed to persistent neural activity. An alternative mechanism which might allow for such information storage is through temporary modifications to the neural connectivity which decay on the same second-long time scale as the underlying memories. Earlier work that has explored this method has done so by emphasizing one attractor from a limited, pre-defined set. Here, we describe an alternative, a Transient Attractor network, which can learn any pattern presented to it, store several simultaneously, and robustly recall them on demand using targeted probes in a manner reminiscent of Hopfield networks. We hypothesize that such functionality could be usefully embedded within sensory cortex, and allow for a flexibly-gated short-term memory, as well as conferring the ability of the network to perform automatic de-noising, and separation of input signals into distinct perceptual objects. We demonstrate that the stored information can be refreshed to extend storage time, is not sensitive to noise in the system, and can be turned on or off by simple neuromodulation. The diverse capabilities of transient attractors, as well as their resemblance to many features observed in sensory cortex, suggest the possibility that their actions might underlie neural processing in many sensory areas.

  11. What can He II 304 Å tell us about transient seismic emission from solar flares?

    Science.gov (United States)

    Lindsey, C.; Donea, A. C.

    2017-10-01

    After neary 20 years since their discovery by Kosovichev and Zharkova, the mechanics of the release of seismic transients into the solar interior from some flares remain a mystery. Seismically emissive flares invariably show the signatures of intense chromosphere heating consistent with pressure variations sufficient to drive seismic transients commensurate with helioseismic observations-under certain conditions. Magnetic observations show the signatures of apparent magnetic changes, suggesting Lorentz-force transients that could likewise drive seismic transients-similarly subject to certain conditions. But, the diagnostic signatures of both of these prospective drivers are apparent over vast regions from which no significant seismic emission emanates. What distinguishes the source regions of transient seismic emission from the much vaster regions that show the signatures of both transient heating and magnetic variations but are acoustically unproductive? Observations of acoustically active flares in He II 304 Å by the Atomospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO) offer a promising new resource with which to address this question.

  12. Characterization of Pressure Transients Generated by Nanosecond Electrical Pulse (nsEP) Exposure

    Science.gov (United States)

    Roth, Caleb C.; Barnes Jr., Ronald A.; Ibey, Bennett L.; Beier, Hope T.; Christopher Mimun, L.; Maswadi, Saher M.; Shadaram, Mehdi; Glickman, Randolph D.

    2015-01-01

    The mechanism(s) responsible for the breakdown (nanoporation) of cell plasma membranes after nanosecond pulse (nsEP) exposure remains poorly understood. Current theories focus exclusively on the electrical field, citing electrostriction, water dipole alignment and/or electrodeformation as the primary mechanisms for pore formation. However, the delivery of a high-voltage nsEP to cells by tungsten electrodes creates a multitude of biophysical phenomena, including electrohydraulic cavitation, electrochemical interactions, thermoelastic expansion, and others. To date, very limited research has investigated non-electric phenomena occurring during nsEP exposures and their potential effect on cell nanoporation. Of primary interest is the production of acoustic shock waves during nsEP exposure, as it is known that acoustic shock waves can cause membrane poration (sonoporation). Based on these observations, our group characterized the acoustic pressure transients generated by nsEP and determined if such transients played any role in nanoporation. In this paper, we show that nsEP exposures, equivalent to those used in cellular studies, are capable of generating high-frequency (2.5 MHz), high-intensity (>13 kPa) pressure transients. Using confocal microscopy to measure cell uptake of YO-PRO®-1 (indicator of nanoporation of the plasma membrane) and changing the electrode geometry, we determined that acoustic waves alone are not responsible for poration of the membrane. PMID:26450165

  13. Characterization of Pressure Transients Generated by Nanosecond Electrical Pulse (nsEP) Exposure.

    Science.gov (United States)

    Roth, Caleb C; Barnes, Ronald A; Ibey, Bennett L; Beier, Hope T; Christopher Mimun, L; Maswadi, Saher M; Shadaram, Mehdi; Glickman, Randolph D

    2015-10-09

    The mechanism(s) responsible for the breakdown (nanoporation) of cell plasma membranes after nanosecond pulse (nsEP) exposure remains poorly understood. Current theories focus exclusively on the electrical field, citing electrostriction, water dipole alignment and/or electrodeformation as the primary mechanisms for pore formation. However, the delivery of a high-voltage nsEP to cells by tungsten electrodes creates a multitude of biophysical phenomena, including electrohydraulic cavitation, electrochemical interactions, thermoelastic expansion, and others. To date, very limited research has investigated non-electric phenomena occurring during nsEP exposures and their potential effect on cell nanoporation. Of primary interest is the production of acoustic shock waves during nsEP exposure, as it is known that acoustic shock waves can cause membrane poration (sonoporation). Based on these observations, our group characterized the acoustic pressure transients generated by nsEP and determined if such transients played any role in nanoporation. In this paper, we show that nsEP exposures, equivalent to those used in cellular studies, are capable of generating high-frequency (2.5 MHz), high-intensity (>13 kPa) pressure transients. Using confocal microscopy to measure cell uptake of YO-PRO®-1 (indicator of nanoporation of the plasma membrane) and changing the electrode geometry, we determined that acoustic waves alone are not responsible for poration of the membrane.

  14. Structural Integrity Assessment of VVER-1000 RPV under Accidental Cool down Transients

    International Nuclear Information System (INIS)

    Shrivastav, V.; Sen, R.N.; Yadav, R.S.

    2012-01-01

    Corrosion, Fatigue and Irradiation embrittlement are the major degradation mechanisms responsible for ageing of RPV (and its internals) of a Pressurized Water Reactor. While corrosion and fatigue can generate cracks, irradiation damage can lead to brittle fracture initiating from these cracks. Ageing in nuclear power plants needs to be managed so as to ensure that design functions remain available throughout the life of the plant. From safety perspective, this implies that ageing degradation of systems, structures and components important to safety remain within acceptable limits. Reactor Pressure Vessel has been identified as the highest priority key component in plant life management for Pressurized Water Reactors. Therefore special attention is required to ensure its structural integrity during its lifetime. In this paper, structural integrity assessment for typical VVER-1000 RPV is carried out under severe accidental cool down transients using the Finite Element Method. Three different accidental scenarios are postulated and safety of the vessel is conservatively assessed under these transients using the Linear Elastic Fracture Mechanics approach. Transient thermo mechanical stress analysis of the core belt region of the RPV is carried out in presence of postulated cracks and stress intensity factors are calculated and compared with the material fracture toughness to assess the structural integrity of the vessel. The paper also include some parametric analyses to justify the methodology. (author)

  15. Transient feedback from fuel motion in metal IFR [Integral Fast Reactor] fuel

    International Nuclear Information System (INIS)

    Rhodes, E.A.; Stanford, G.S.; Regis, J.P.; Bauer, T.H.; Dickerman, C.E.

    1990-01-01

    Results from hodoscope data analyses are presented for TREAT transient-overpower tests M5 through M7 with emphasis on transient feedback mechanisms, including prefailure expansion at the tops of the fuel pins, subsequent dispersive axial fuel motion, and losses in relative worth of the fuel pins during the tests. Tests M5 and M6 were the first TOP tests of margin to cladding branch and prefailure elongation of D9-clad ternary (U-Pu-Zr) IFR-type fuel. Test M7 extended these results to high-burnup fuel and also initiated transient testing of HT9-clad binary (U-Zr) FFTF-driver fuel. Results show significant prefailure negative reactivity feedback and strongly negative feedback from fuel driven to failure. 4 refs., 6 figs

  16. Transient Dynamics Analysis of The Reachstacker Speader Based On ANSYS

    Directory of Open Access Journals (Sweden)

    Shu Yu Feng

    2016-01-01

    Full Text Available Reachstacker is an indispensable handling machinery, it will inevitably lead to unbalanced force at the job site. This paper does transient dynamics analysis for the spreader mechanism, which is one of the most significance key components. We get dynamic response of the spreader in lifting instant, results not only provide a reference for designers to understand the mechanical characteristics of spreader comprehensively, but also bedding for the future research.

  17. Transient from crystallization to fractal growth observed in both boar bile and SnI sub 2 vapour

    CERN Document Server

    Zhang Ji Zhong; Xie An Jian

    2003-01-01

    A visual transient of the growth mechanism from crystallization to fractal growth was observed clearly in a drop of boar bile. The growing crystals were replaced by treelike fractal structures during solidification of the sample. It is fascinating to compare the transient with the result observed in SnI sub 2 vapour. They were completely identical, and revealed that under certain conditions a linear growth could be transferred spontaneously into nonlinear growth. It may be possible to consider the transient as a 'bridge' between linear and nonlinear growth, and to develop a quantitative expression of transient dynamics.

  18. Spontaneous calcium transients in human neural progenitor cells mediated by transient receptor potential channels.

    Science.gov (United States)

    Morgan, Peter J; Hübner, Rayk; Rolfs, Arndt; Frech, Moritz J

    2013-09-15

    Calcium signals affect many developmental processes, including proliferation, migration, survival, and apoptosis, processes that are of particular importance in stem cells intended for cell replacement therapies. The mechanisms underlying Ca(2+) signals, therefore, have a role in determining how stem cells respond to their environment, and how these responses might be controlled in vitro. In this study, we examined the spontaneous Ca(2+) activity in human neural progenitor cells during proliferation and differentiation. Pharmacological characterization indicates that in proliferating cells, most activity is the result of transient receptor potential (TRP) channels that are sensitive to Gd(3+) and La(3+), with the more subtype selective antagonist Ruthenium red also reducing activity, suggesting the involvement of transient receptor potential vanilloid (TRPV) channels. In differentiating cells, Gd(3+) and La(3+)-sensitive TRP channels also appear to underlie the spontaneous activity; however, no sub-type-specific antagonists had any effect. Protein levels of TRPV2 and TRPV3 decreased in differentiated cells, which is demonstrated by western blot. Thus, it appears that TRP channels represent the main route of Ca(2+) entry in human neural progenitor cells (hNPCs), but the responsible channel types are subject to substitution under differentiating conditions. The level of spontaneous activity could be increased and decreased by lowering and raising the extracellular K(+) concentration. Proliferating cells in low K(+) slowed the cell cycle, with a disproportionate increased percentage of cells in G1 phase and a reduction in S phase. Taken together, these results suggest a link between external K(+) concentration, spontaneous Ca(2+) transients, and cell cycle distribution, which is able to influence the fate of stem and progenitor cells.

  19. Fundamental study on thermo-hydraulic behaviors during power transient, 2

    International Nuclear Information System (INIS)

    Shinano, M.; Inoue, A.

    1988-01-01

    Thermo-hydraulic behaviors during power transient of nuclear reactors are studied. Boiling around test rod heated transiently forces to flow out liquid in the test section and generates high pressure pulse. In this study, it is investigated experimentally and analytically that magnitude of pressure pulse and energy conversion efficiency to the mechanical works in cases of fragmentation and non-fragmentation. In analysis, effects of increasing of heat transfer and of interaction area due to fragmentation is considered. Consequently, 1) magnitude of pressure pulse on fragmentation is about 10 times greater than that on non-fragmentation. 2) analytical model can show characteristics of fragmentation processes qualitatively. (author)

  20. A simplified model for tritium permeation transient predictions when trapping is active

    International Nuclear Information System (INIS)

    Longhurst, G.R.

    1994-01-01

    This report describes a simplified one-dimensional tritium permeation and retention model. The model makes use of the same physical mechanisms as more sophisticated, time-transient codes such as implantation, recombination, diffusion, trapping and thermal gradient effects. It takes advantage of a number of simplifications and approximations to solve the steady-state problem and then provides interpolating functions to make estimates of intermediate states based on the steady-state solution. Comparison calculations with the verified and validated TMAP4 transient code show good agreement. ((orig.))

  1. A simplified model for tritium permeation transient predictions when trapping is active

    Energy Technology Data Exchange (ETDEWEB)

    Longhurst, G.R. (Fusion Safety Program, Idaho National Engineering Laboratory, P.O. Box 1625, Idaho Falls, ID 83415 (United States))

    1994-09-01

    This report describes a simplified one-dimensional tritium permeation and retention model. The model makes use of the same physical mechanisms as more sophisticated, time-transient codes such as implantation, recombination, diffusion, trapping and thermal gradient effects. It takes advantage of a number of simplifications and approximations to solve the steady-state problem and then provides interpolating functions to make estimates of intermediate states based on the steady-state solution. Comparison calculations with the verified and validated TMAP4 transient code show good agreement. ((orig.))

  2. Investigations on heavy ion induced Single-Event Transients (SETs) in highly-scaled FinFETs

    Energy Technology Data Exchange (ETDEWEB)

    Gaillardin, M., E-mail: marc.gaillardin@cea.fr [CEA, DAM, DIF, F-91297 Arpajon (France); Raine, M.; Paillet, P. [CEA, DAM, DIF, F-91297 Arpajon (France); Adell, P.C. [Jet Propulsion Laboratory, Pasadena, CA 91101 (United States); Girard, S. [Université de Saint-Etienne, Laboratoire H. Curien, UMR-5516, 42000 Saint-Etienne (France); Duhamel, O. [CEA, DAM, DIF, F-91297 Arpajon (France); Andrieu, F.; Barraud, S.; Faynot, O. [CEA, LETI-Minatec, 17 avenue des Martyrs, 38000 Grenoble (France)

    2015-12-15

    We investigate Single-Event Transients (SET) in different designs of multiple-gate devices made of FinFETs with various geometries. Heavy ion experimental results are explained by using a thorough charge collection analysis of fast transients measured on dedicated test structures. Multi-level simulations are performed to get new insights into the charge collection mechanisms in multiple-gate devices. Implications for multiple-gate device design hardening are finally discussed.

  3. Implications of the delayed 2013 outburst of ESO 243-49 HLX-1

    Energy Technology Data Exchange (ETDEWEB)

    Godet, O.; Webb, N. A. [Institut de Recherche en Astrophysique and Planétologie (IRAP), Université de Toulouse, UPS, 9 Avenue du colonel Roche, F-31028 Toulouse Cedex 4 (France); Lombardi, J. C.; Vingless, J.; Thomas, M. [Department of Physics, Allegheny College, Meadville, PA 16335 (United States); Antonini, F.; Barret, D. [Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, Ontario M5S 3H8 (Canada)

    2014-10-01

    After showing four quasi-periodic outbursts spaced by ∼1 yr from 2009 to 2012, the hyper luminous X-ray source ESO 243-49 HLX-1, currently the best intermediate mass black hole (IMBH) candidate, showed an outburst in 2013 delayed by more than a month. In Lasota et al., we proposed that the X-ray light curve is the result of enhanced mass transfer episodes at periapsis from a donor star orbiting the IMBH in a highly eccentric orbit. In this scenario, the delay can be explained only if the orbital parameters can change suddenly from orbit to orbit. To investigate this, we ran Newtonian smooth particle hydrodynamical simulations starting with an incoming donor approaching an IMBH on a parabolic orbit. We survey a large parameter space by varying the star-to-black hole mass ratio (10{sup –5}-10{sup –3}) and the periapsis separation r{sub p} from 2.2 to 2.7r{sub t} with r{sub t} , the tidal radius. To model the donor, we choose several polytropes (Γ = 5/2, n = 3/2, Γ = 3/2, n = 2, Γ = 5/3, n = 2, and Γ = 5/3, n = 3). Once the system is formed, the orbital period decreases until reaching a minimum that may be shallow. Then, the period tends to increase over several periapsis passages due to tidal effects and increasing mass transfer, leading ultimately to the ejection of the donor. We show that the development of stochastic fluctuations inside the donor by adding or removing orbital energy from the system could lead to sudden changes in the orbital period from orbit to orbit with the appropriate order of magnitude to that which has been observed for HLX-1. We also show that given the constraints on the black hole (BH) mass (M {sub BH} > 10{sup 4} M {sub ☉}) and assuming that the HLX-1 system is currently near a minimum in period of ∼1 yr, the donor has to be a white dwarf or a stripped giant core. We predict that if HLX-1 is indeed emerging from a minimum in orbital period, then the period would generally increase with each passage, although substantial

  4. Impact of Model Detail of Synchronous Machines on Real-time Transient Stability Assessment

    DEFF Research Database (Denmark)

    Weckesser, Johannes Tilman Gabriel; Jóhannsson, Hjörtur; Østergaard, Jacob

    2013-01-01

    In this paper, it is investigated how detailed the model of a synchronous machine needs to be in order to assess transient stability using a Single Machine Equivalent (SIME). The results will show how the stability mechanism and the stability assessment are affected by the model detail. In order...... of the machine models is varied. Analyses of the results suggest that a 4th-order model may be sufficient to represent synchronous machines in transient stability studies....

  5. Peptidomics Analysis of Transient Regeneration in the Neonatal Mouse Heart.

    Science.gov (United States)

    Fan, Yi; Zhang, Qijun; Li, Hua; Cheng, Zijie; Li, Xing; Chen, Yumei; Shen, Yahui; Wang, Liansheng; Song, Guixian; Qian, Lingmei

    2017-09-01

    Neonatal mouse hearts have completely regenerative capability after birth, but the ability to regenerate rapidly lost after 7 days, the mechanism has not been clarified. Previous studies have shown that mRNA profile of adult mouse changed greatly compared to neonatal mouse. So far, there is no research of peptidomics related to heart regeneration. In order to explore the changes of proteins, enzymes, and peptides related to the transient regeneration, we used comparative petidomics technique to compare the endogenous peptides in the mouse heart of postnatal 1 and 7 days. In final, we identified 236 differentially expressed peptides, 169 of which were upregulated and 67 were downregulated in the postnatal 1 day heart, and also predicted 36 functional peptides associated with transient regeneration. The predicted 36 candidate peptides are located in the important domains of precursor proteins and/or contain the post-transcriptional modification (PTM) sites, which are involved in the biological processes of cardiac development, cardiac muscle disease, cell proliferation, necrosis, and apoptosis. In conclusion, for the first time, we compared the peptidomics profiles of neonatal heart between postnatal 1 day and postnatal 7 day. This study provides a new direction and an important basis for the mechanism research of transient regeneration in neonatal heart. J. Cell. Biochem. 118: 2828-2840, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  6. Mechanistic considerations used in the development of the probability of failure in transient increases in power (PROFIT) pellet-zircaloy cladding (thermo-mechanical-chemical) interactions (pci) fuel failure model

    International Nuclear Information System (INIS)

    Pankaskie, P.J.

    1980-05-01

    A fuel Pellet-Zircaloy Cladding (thermo-mechanical-chemical) interactions (PCI) failure model for estimating the Probability of Failure in Transient Increases in Power (PROFIT) was developed. PROFIT is based on (1) standard statistical methods applied to available PCI fuel failure data and (2) a mechanistic analysis of the environmental and strain-rate-dependent stress versus strain characteristics of Zircaloy cladding. The statistical analysis of fuel failures attributable to PCI suggested that parameters in addition to power, transient increase in power, and burnup are needed to define PCI fuel failures in terms of probability estimates with known confidence limits. The PROFIT model, therefore, introduces an environmental and strain-rate dependent Strain Energy Absorption to Failure (SEAF) concept to account for the stress versus strain anomalies attributable to interstitial-dislocation interaction effects in the Zircaloy cladding

  7. Biodegradable elastomers and silicon nanomembranes/nanoribbons for stretchable, transient electronics, and biosensors.

    Science.gov (United States)

    Hwang, Suk-Won; Lee, Chi Hwan; Cheng, Huanyu; Jeong, Jae-Woong; Kang, Seung-Kyun; Kim, Jae-Hwan; Shin, Jiho; Yang, Jian; Liu, Zhuangjian; Ameer, Guillermo A; Huang, Yonggang; Rogers, John A

    2015-05-13

    Transient electronics represents an emerging class of technology that exploits materials and/or device constructs that are capable of physically disappearing or disintegrating in a controlled manner at programmed rates or times. Inorganic semiconductor nanomaterials such as silicon nanomembranes/nanoribbons provide attractive choices for active elements in transistors, diodes and other essential components of overall systems that dissolve completely by hydrolysis in biofluids or groundwater. We describe here materials, mechanics, and design layouts to achieve this type of technology in stretchable configurations with biodegradable elastomers for substrate/encapsulation layers. Experimental and theoretical results illuminate the mechanical properties under large strain deformation. Circuit characterization of complementary metal-oxide-semiconductor inverters and individual transistors under various levels of applied loads validates the design strategies. Examples of biosensors demonstrate possibilities for stretchable, transient devices in biomedical applications.

  8. Helical Tomography of an Accretion Disk by Superhump Light Curves of the 2001 Outburst of WZ Sagittae

    Science.gov (United States)

    Osaki, Yoji

    2003-06-01

    A new method for analyzing complex superhump light curves for the 2001 outburst of WZ Sagittae is proposed. The complexity arises because intrinsically time-varying and non-axisymmetric distributions of superhump light sources are coupled with the aspect effects around the binary orbital phase because of its high orbital inclination. The new method can disentangle these complexities by separating the non-axisymmetric spatial distribution in the disk from the time variation with the superhump period. It may be called a helical tomography of an accretion disk because it can reconstruct a series of disk images (i.e., disk's azimuthal structures) at different superhump phases. The power spectral data of superhump light curves of the 2001 outburst of WZ Sge by Patterson et al. (2002, PASP, 114, 721) are now interpreted under a new light based on the concept of helical tomography, and the azimuthal wave numbers of various frequency modes are identified. In particular, a frequen! cy component, nω0 - Ω, where ω0 and Ω are the orbital frequency and a low frequency of the apsidal precession of the eccentric disk, is understood as an (n - 1)-armed traveling wave in the disk. A vigorous excitation of a wave component of cos(2Θ - 3ω0t) in the first week of the superhump era of WZ Sge, where Θ is the azimuthal angle, supports Lubow's (1991, AAA 54.064.175) theory of non-linear wave coupling of the eccentric Lindblad resonance for the superhump phenomenon. This method can in principle be applied to other SU UMa stars with high orbital inclination if light curves are fully covered over the beat cycle.

  9. Pressure Transient Model of Water-Hydraulic Pipelines with Cavitation

    Directory of Open Access Journals (Sweden)

    Dan Jiang

    2018-03-01

    Full Text Available Transient pressure investigation of water-hydraulic pipelines is a challenge in the fluid transmission field, since the flow continuity equation and momentum equation are partial differential, and the vaporous cavitation has high dynamics; the frictional force caused by fluid viscosity is especially uncertain. In this study, due to the different transient pressure dynamics in upstream and downstream pipelines, the finite difference method (FDM is adopted to handle pressure transients with and without cavitation, as well as steady friction and frequency-dependent unsteady friction. Different from the traditional method of characteristics (MOC, the FDM is advantageous in terms of the simple and convenient computation. Furthermore, the mechanism of cavitation growth and collapse are captured both upstream and downstream of the water-hydraulic pipeline, i.e., the cavitation start time, the end time, the duration, the maximum volume, and the corresponding time points. By referring to the experimental results of two previous works, the comparative simulation results of two computation methods are verified in experimental water-hydraulic pipelines, which indicates that the finite difference method shows better data consistency than the MOC.

  10. Transients: The regulator's view

    International Nuclear Information System (INIS)

    Sheron, B.W.; Speis, T.P.

    1984-01-01

    This chapter attempts to clarify the basis for the regulator's concerns for transient events. Transients are defined as both anticipated operational occurrences and postulated accidents. Recent operational experience, supplemented by improved probabilistic risk analysis methods, has demonstrated that non-LOCA transient events can be significant contributors to overall risk. Topics considered include lessons learned from events and issues, the regulations governing plant transients, multiple failures, different failure frequencies, operator errors, and public pressure. It is concluded that the formation of Owners Groups and Regulatory Response Groups within the owners groups are positive signs of the industry's concern for safety and responsible dealing with the issues affecting both the US NRC and the industry

  11. Waves of visibility: probing the depth of inter-ocular suppression with transient and sustained targets

    Directory of Open Access Journals (Sweden)

    Lisandro eKaunitz

    2014-07-01

    Full Text Available In order to study non-conscious visual processing, researchers render otherwise consciously perceived images into invisible stimuli. Through the years, several psychophysical techniques have been developed for this purpose. Yet the comparison of experimental results across techniques remains a difficult task as the depth of suppression depends on the interactions between the type of stimuli and the suppression methods employed. This poses a limit to the inferences that researchers make about the extent of non-conscious processes. We investigated the mechanisms underlying inter-ocular suppression during continuous flash suppression (CFS and dichoptic visual masking using a transient onset target stimulus and a variety of stimulus / mask temporal manipulations. We show that target duration, timing of target onset, and mask frequency are key aspects of inter-ocular suppression during CFS with transient targets. The differences between our results and sustained target CFS studies suggest that two distinct mechanisms are involved in the detection of transient and prolonged target stimuli during CFS. Our results provide insight into the dynamics of CFS together with evidence for similarities between transient target CFS and dichoptic visual masking.

  12. Application of the spine-layer jet radiation model to outbursts in the broad-line radio galaxy 3C 120

    Science.gov (United States)

    Janiak, M.; Sikora, M.; Moderski, R.

    2016-05-01

    We present a detailed Fermi/LAT data analysis for the broad-line radio galaxy 3C 120. This source has recently entered into a state of increased γ-ray activity which manifested itself in two major flares detected by Fermi/LAT in 2014 September and 2015 April with no significant flux changes reported in other wavelengths. We analyse available data focusing our attention on aforementioned outbursts. We find very fast variability time-scale during flares (of the order of hours) together with a significant γ-ray flux increase. We show that the ˜6.8 yr averaged γ-ray emission of 3C 120 is likely a sum of the external radiation Compton and the synchrotron self-Compton radiative components. To address the problem of violent γ-ray flares and fast variability we model the jet radiation dividing the jet structure into two components: the wide and relatively slow outer layer and the fast, narrow spine. We show that with the addition of the fast spine occasionally bent towards the observer we are able to explain observed spectral energy distribution of 3C 120 during flares with the Compton upscattered broad-line region and dusty torus photons as main γ-rays emission mechanism.

  13. Structural dynamics and fracture mechanics calculations of the behaviour of a DN 425 test piping system subjected to transient loading by water hammer

    International Nuclear Information System (INIS)

    Kussmaul, K.; Kobes, E.; Diem, H.; Schrammel, D.; Brosi, S.

    1994-01-01

    Within the scope of the German HDR safety programme, several tests were carried out to investigate transient pipe loading initiated by a simulated double-ended guillotine break event, and subsequent closure of a feedwater check valve (water hammer, blow-down). Numerical analyses by means of finite element programmes were performed in parallel to the experiments. Using water hammer tests of a DN 425 piping system with predamaged components, the procedure of such analyses will be demonstrated. The results are presented, beginning with structural dynamic calculations of the undamaged piping; followed by coupling of structural dynamics and fracture mechanics computations with simple flaw elements (line spring); and finishing with costly three-dimensional fracture mechanics analyses. A good description of the real piping behaviour can be made by the numerical methods, even in the case of high plastification processes. ((orig.))

  14. Transient flow analysis of integrated valve opening process

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Xinming; Qin, Benke; Bo, Hanliang, E-mail: bohl@tsinghua.edu.cn; Xu, Xingxing

    2017-03-15

    Highlights: • The control rod hydraulic driving system (CRHDS) is a new type of built-in control rod drive technology and the integrated valve (IV) is the key control component. • The transient flow experiment induced by IV is conducted and the test results are analyzed to get its working mechanism. • The theoretical model of IV opening process is established and applied to get the changing rule of the transient flow characteristic parameters. - Abstract: The control rod hydraulic driving system (CRHDS) is a new type of built-in control rod drive technology and the IV is the key control component. The working principle of integrated valve (IV) is analyzed and the IV hydraulic experiment is conducted. There is transient flow phenomenon in the valve opening process. The theoretical model of IV opening process is established by the loop system control equations and boundary conditions. The valve opening boundary condition equation is established based on the IV three dimensional flow field analysis results and the dynamic analysis of the valve core movement. The model calculation results are in good agreement with the experimental results. On this basis, the model is used to analyze the transient flow under high temperature condition. The peak pressure head is consistent with the one under room temperature and the pressure fluctuation period is longer than the one under room temperature. Furthermore, the changing rule of pressure transients with the fluid and loop structure parameters is analyzed. The peak pressure increases with the flow rate and the peak pressure decreases with the increase of the valve opening time. The pressure fluctuation period increases with the loop pipe length and the fluctuation amplitude remains largely unchanged under different equilibrium pressure conditions. The research results lay the base for the vibration reduction analysis of the CRHDS.

  15. Natural dam failure in the eastern slope of the Central Andes of Argentina. Numerical modelling of the 2005 Santa Cruz river outburst flood

    Science.gov (United States)

    Penna, I.; Daicz, S.; Zlotnik, S.; Derron, M.-H.; Jaboyedoff, M.

    2012-04-01

    In the Central Andes of Argentina, ephemeral river blockage due to landslides deposition are common phenomena. During the first fortnight of January 2005, 11.5 * 106m3 of rock collapsed from the east slope of the Santa Cruz valley (San Juan province, Argentina). The rock mass displaced from 4300 m a.s.l., down to the valley bottom, at 2900 m a.s.l., and ran up the opposite flank of the valley. This produced the blockage of the Santa Cruz river and generated the Los Erizos lake. The rapid snow melting during the spring season caused the increase of the water level of the reservoir, leading to a process of overtopping on November 12th of 2005. 30 * 106m3 of water were released from the reservoir and the consequent outburst flood displaced along 250 km. From local reports of arrival times, we estimated that the outburst flood reduced its velocity from around 40 km/h near the source area to 6 km/h in its distal section. A road, bridges, and a mining post where destroyed. 75 tourists had to be rescued from the mountains using helicopters, and people from two localities had to be evacuated. Near its distal part, the flood damaged the facilities of the Caracoles power dam, which was under construction, and its inauguration had to be delayed one year due to the damage. The outburst flood produced changes in the morphology of the valley floor along almost all its path (erosion of alluvial fans, talus and terraces, and deposition of boulders). The most significant changes occurred in the first 70 km, especially upstream narrow sections, showing the importance of the backwater effects due to hydraulic ponding. In this work we carried out numerical simulations to obtain the velocity patterns of the flood, and compared them with those obtained from local reports. Furthermore, we analyze the relationship between the dynamics of the flood with the patterns of erosion and deposition near the source area.

  16. Subaru/COMICS Mid-Infrared Observation of the Near-Nucleus Region of Comet 17P/Holmes at the Early Phase of an Outburst

    Science.gov (United States)

    Watanabe, Jun-Ichi; Honda, Mitsuhiko; Ishiguro, Masateru; Ootsubo, Takafumi; Sarugaku, Yuki; Kadono, Toshihiko; Sakon, Itsuki; Fuse, Tetsuharu; Takato, Naruhisa; Furusho, Reiko

    2009-08-01

    Mid-infrared 8--25μm imaging and spectroscopic observations of the comet 17P/Holmes in the early phase of its outburst in brightness were performed on 2007 October 25--28UT using the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on the 8.2-m Subaru Telescope. We detected an isolated dust cloud that moved toward the south-west direction from the nucleus. The 11.2μm peak of a crystalline silicate feature onto a broad amorphous silicate feature was also detected both in the central condensation of the nucleus and an isolated dust cloud. The color temperature of the isolated dust cloud was estimated to be ˜200K, which is slightly higher than the black-body temperature. Our analysis of the motion indicates that the isolated cloud moved anti-sunward. We propose several possibilities for the motion of the cloud: fluffy dust particles in the isolated cloud started to depart from the nucleus due to radiation pressure almost as soon as the main outburst occurred, or dust particles moved by some other anti-sunward forces, such as a rocket effect and photophoresis when the surrounding dust coma became optically thin. The origin and the nature of the isolated dust cloud are discussed in this paper.

  17. Transient behaviour of deep underground salt caverns

    International Nuclear Information System (INIS)

    Karimi-Jafari, M.

    2007-11-01

    This work deals with the transient behaviour of deep underground salt caverns. It has been shown that a cavern is a complex system, in which there are mechanical, thermal, chemical and hydraulic evolutions. The importance of the transient evolutions, particularly the role of the 'reverse' creep in the interpretation of the tightness test in a salt cavern is revealed. Creep is characterized by a formulation of the behaviour law which presents the advantage, in a practical point of view, to only have a reduced number of parameters while accounting of the essential of what it is observed. The initiation of the rupture in the effective traction in a salt cavern rapidly pressurized is discussed. A model fitted to a very long term behaviour (after abandonment) is developed too. In this case too, a lot of phenomena, more or less coupled, occur, when the existing literature took only into account some phenomena. (O.M.)

  18. Damage behavior of REE-doped W-based material exposed to high-flux transient heat loads

    International Nuclear Information System (INIS)

    Shi, Jing; Luo, Lai–Ma; Lin, Jin–shan; Zan, Xiang; Zhu, Xiao–yong; Xu, Qiu; Wu, Yu–Cheng

    2016-01-01

    Pure W and W-Lu alloys were prepared by mechanical alloying (MA) and spark plasma sintering (SPS) technology. The performance and relevant damage mechanism of W-(0%, 2%, 5%, 10%) Lu alloys under transient heat loads were investigated using a laser beam heat load test to simulate the transient events in future nuclear fusion reactors. Scanning electron microscopy was used to observe the morphologies of the damaged surfaces and energy dispersive X-ray spectroscopy was used to conduct composition analysis. Damages to the surface such as cracks, pits, melting layers, Lu-rich droplets, and thermal ablation were observed. A mass of dense fuzz-like nanoparticles formed on the outer region of the laser-exposed area. Recrystallization, grain growth, increased surface roughness, and material erosion were also observed. W-Lu samples with low Lu content demonstrated better thermal performance than pure W, and the degree of damage significantly deteriorated under repetitive transient heat loads.

  19. Searching for MHz Transients with the VLA Low-band Ionosphere and Transient Experiment (VLITE)

    Science.gov (United States)

    Polisensky, Emil; Peters, Wendy; Giacintucci, Simona; Clarke, Tracy; Kassim, Namir E.; hyman, Scott D.; van der Horst, Alexander; Linford, Justin; Waldron, Zach; Frail, Dale

    2018-01-01

    NRL and NRAO have expanded the low frequency capabilities of the VLA through the VLA Low-band Ionosphere and Transient Experiment (VLITE, http://vlite.nrao.edu/ ), effectively making the instrument two telescopes in one. VLITE is a commensal observing system that harvests data from the prime focus in parallel with normal Cassegrain focus observing on a subset of VLA antennas. VLITE provides over 6000 observing hours per year in a > 5 square degree field-of-view using 64 MHz bandwidth centered on 352 MHz. By operating in parallel, VLITE offers invaluable low frequency data to targeted observations of transient sources detected at higher frequencies. With arcsec resolution and mJy sensitivity, VLITE additionally offers great potential for blind searches of rarer radio-selected transients. We use catalog matching software on the imaging products from the daily astrophysics pipeline and the LOFAR Transients Pipeline (TraP) on repeated observations of the same fields to search for coherent and incoherent astronomical transients on timescales of a few seconds to years. We present the current status of the VLITE transient science program from its initial deployment on 10 antennas in November 2014 through its expansion to 16 antennas in the summer of 2017. Transient limits from VLITE’s first year of operation (Polisensky et al. 2016) are updated per the most recent analysis.

  20. Multi-scale modeling of the mechanical behavior of polycrystalline ice under transient creep.

    OpenAIRE

    Suquet , Pierre; Moulinec , Hervé; Castelnau , O.; Montagnat , Maurine; Lahellec , Noël; Grennerat , Fanny; Duval , Paul; Brenner , Renald

    2012-01-01

    International audience; Ice is a challenging material for understanding the overall behavior of polycrystalline materials and more specifically the coupling between elastic and viscous effects during transient creep. At the single crystal level, ice is an hexagonal material with a rather weak elastic anisotropy but with a strong viscoplastic anisotropy. The strain-stress curve of ice single crystals shows a softening behavior depending on the strain-rate. The strong viscous anisotropy of ice ...