WorldWideScience

Sample records for burst x-ray flares

  1. Flare classification with X-ray, particles, and radio bursts

    International Nuclear Information System (INIS)

    Some important works are concisely reviewed on flare classification with the observational results from various satellites during the last solar maximum. First, the observational definitions of impulsive and gradual types of flares are given. Next, the phenomena pertaining to meter-wave bursts are described and explained. When these meter-wave phenomena are taken into account, it is shown that clear classification can be achieved. Basically, all the flares are classified into two types of events, that is, impulsive and gradual flares. This simple classification may help to understand the relationships among the various phenomena on the sun and those in the interplanetary space. (author)

  2. Comprehensive Study of the X-Ray Flares from Gamma-ray Bursts Observed by Swift

    Science.gov (United States)

    Yi, Shuang-Xi; Xi, Shao-Qiang; Yu, Hai; Wang, F. Y.; Mu, Hui-Jun; Lü, Lian-Zhong; Liang, En-Wei

    2016-06-01

    X-ray flares are generally supposed to be produced by later activities of the central engine, and may share a similar physical origin with the prompt emission of gamma-ray bursts (GRBs). In this paper, we have analyzed all significant X-ray flares from the GRBs observed by Swift from 2005 April to 2015 March. The catalog contains 468 bright X-ray flares, including 200 flares with redshifts. We obtain the fitting results of X-ray flares, such as start time, peak time, duration, peak flux, fluence, peak luminosity, and mean luminosity. The peak luminosity decreases with peak time, following a power-law behavior {L}{{p}}\\propto {T}{peak,z}-1.27. The flare duration increases with peak time. The 0.3–10 keV isotropic energy of the distribution of X-ray flares is a log-normal peaked at {10}51.2 erg. We also study the frequency distributions of flare parameters, including energies, durations, peak fluxes, rise times, decay times, and waiting times. Power-law distributions of energies, durations, peak fluxes, and waiting times are found in GRB X-ray flares and solar flares. These distributions could be well explained by a fractal-diffusive, self-organized criticality model. Some theoretical models based on magnetic reconnection have been proposed to explain X-ray flares. Our result shows that the relativistic jets of GRBs may be dominated by Poynting flux.

  3. Self-organized criticality in X-ray flares of gamma-ray burst afterglows

    OpenAIRE

    Wang, F.Y.; Dai, Z. G.

    2013-01-01

    X-ray flares detected in nearly half of gamma-ray burst (GRB) afterglows are one of the most intriguing phenomena in high-energy astrophysics. All the observations indicate that the central engines of bursts, after the gamma-ray emission has ended, still have long periods of activity, during which energetic explosions eject relativistic materials, leading to late-time X-ray emission. It is thus expected that X-ray flares provide important clues to the nature of the central engines of GRBs, an...

  4. Lag-luminosity relation in gamma-ray burst X-ray flares

    CERN Document Server

    Margutti, R

    2010-01-01

    In strict analogy to prompt pulses, X-ray flares observed by Swift-XRT in long Gamma-Ray Bursts define a lag-luminosity relation: L_p,iso \\propto t_lag^{-0.95+/-0.23}. The lag-luminosity is proven to be a fundamental law extending 5 decades in time and 5 in energy. This is direct evidence that GRB X-ray flares and prompt gamma-ray pulses are produced by the same mechanism.

  5. Self-organized criticality in X-ray flares of gamma-ray burst afterglows

    CERN Document Server

    Wang, F Y

    2013-01-01

    X-ray flares detected in nearly half of gamma-ray burst (GRB) afterglows are one of the most intriguing phenomena in high-energy astrophysics. All the observations indicate that the central engines of bursts, after the gamma-ray emission has ended, still have long periods of activity, during which energetic explosions eject relativistic materials, leading to late-time X-ray emission. It is thus expected that X-ray flares provide important clues to the nature of the central engines of GRBs, and more importantly, unveil the physical mechanism of the flares themselves, which has so far remained mysterious. Here we report statistical results of X-ray flares of GRBs with known redshifts, and show that X-ray flares and solar flares share three statistical properties: power-law frequency distributions for energies, durations, and waiting times. All of the distributions can be well understood within the physical framework of a self-organized criticality (SOC) system. The statistical properties of X-ray flares of GRBs...

  6. Comprehensive study of the X-ray flares from gamma-ray bursts observed by Swift

    CERN Document Server

    Yi, Shuang-Xi; Yu, Hai; Wang, F Y; Mu, Hui-Jun; Lv, Lian-Zhong; Liang, En-Wei

    2016-01-01

    X-ray flares are generally supposed to be produced by the later central engine activities, and may share the similar physical origin with prompt emission of gamma-ray bursts (GRBs). In this paper, we have analyzed all significant X-ray flares from the GRBs observed by {\\em Swift} from April 2005 to March 2015. The catalog contains 468 bright X-ray flares, including 200 flares with redshifts. We obtain the fitting results of X-ray flares, such as start time, peak time, duration, peak flux, fluence, peak luminosity, and mean luminosity. The peak luminosity decreases with peak time, following a power-law behavior $L_p \\propto T_{peak,z}^{-1.27}$. The flare duration increases with peak time. The 0.3-10 keV isotropic energy of X-ray flares distribution is a lognormal peaked at $10^{51.2}$ erg. We also study the frequency distributions of flare parameters, including energies, durations, peak fluxes, rise times, decay times and waiting times. Power-law distributions of energies, durations, peak fluxes, and waiting t...

  7. X-ray flares from dense shells formed in gamma-ray burst explosions

    CERN Document Server

    Hascoet, R; Daigne, F; Mochkovitch, R

    2015-01-01

    Bright X-ray flares are routinely detected by the Swift satellite during the early afterglow of gamma-ray bursts, when the explosion ejecta drives a blast wave into the external medium. We suggest that the flares are produced as the reverse shock propagates into the tail of the ejecta. The ejecta is expected to contain a few dense shells formed at an earlier stage of the explosion. We show an example of how such dense shells form and describe how the reverse shock interacts with them. A new reflected shock is generated in this interaction, which produces a short-lived X-ray flare. The model provides a natural explanation for the main observed features of the X-ray flares --- the fast rise, the steep power-law decline, and the characteristic peak duration \\Delta t /t= (0.1-0.3).

  8. GeV-TeV and X-ray flares from gamma-ray burst

    CERN Document Server

    Wang, X Y; Mészáros, P; Li, Zhuo; Meszaros, Peter; Wang, Xiang-Yu

    2006-01-01

    The recent detection of delayed X-ray flares during the afterglow phase of gamma-ray bursts (GRBs) suggests an inner-engine origin, at radii inside the deceleration radius characterizing the beginning of the forward shock afterglow emission. Given the observed temporal overlapping between the flares and afterglows, there must be inverse Compton (IC) emission arising from such flare photons scattered by forward shock afterglow electrons. We find that this IC emission produces GeV-TeV flares, which may be detected by GLAST and ground-based TeV telescopes. We speculate that this kind of emission may already have been detected by EGRET from a very strong burst--GRB940217, if it had a bright X-ray flare at the time of its delayed GeV emission. The enhanced cooling of the forward shock electrons by the X-ray flare photons may suppress the synchrotron emission of the afterglows during the flare period. The detection of GeV-TeV flares combined with low energy observations may help to constrain the poorly known magnet...

  9. Modeling Gamma-Ray Burst X-Ray Flares Within the Internal Shock Model

    Science.gov (United States)

    Maxham, Amanda; Zhang, Bing

    2009-12-01

    X-ray afterglow light curves have been collected for over 400 Swift gamma-ray bursts (GRBs) with nearly half of them having X-ray flares superimposed on the regular afterglow decay. Evidence suggests that gamma-ray prompt emission and X-ray flares share a common origin and that at least some flares can only be explained by long-lasting central engine activity. We have developed a shell model code to address the question of how X-ray flares are produced within the framework of the internal shock model. The shell model creates randomized GRB explosions from a central engine with multiple shells and follows those shells as they collide, merge, and spread, producing prompt emission and X-ray flares. We pay special attention to the time history of central engine activity, internal shocks, and observed flares, but do not calculate the shock dynamics and radiation processes in detail. Using the empirical Ep -E iso (Amati) relation with an assumed Band function spectrum for each collision and an empirical flare temporal profile, we calculate the gamma-ray (Swift/BAT band) and X-ray (Swift/XRT band) lightcurves for arbitrary central engine activity and compare the model results with the observational data. We show that the observed X-ray flare phenomenology can be explained within the internal shock model. The number, width, and occurring time of flares are then used to diagnose the central engine activity, putting constraints on the energy, ejection time, width, and number of ejected shells. We find that the observed X-ray flare time history generally reflects the time history of the central engine, which reactivates multiple times after the prompt emission phase with progressively reduced energy. The same shell model predicts an external shock X-ray afterglow component, which has a shallow decay phase due to the initial pile-up of shells onto the blast wave. However, the predicted X-ray afterglow is too bright as compared with the observed flux level, unless epsilon e is

  10. MODELING GAMMA-RAY BURST X-RAY FLARES WITHIN THE INTERNAL SHOCK MODEL

    International Nuclear Information System (INIS)

    X-ray afterglow light curves have been collected for over 400 Swift gamma-ray bursts (GRBs) with nearly half of them having X-ray flares superimposed on the regular afterglow decay. Evidence suggests that gamma-ray prompt emission and X-ray flares share a common origin and that at least some flares can only be explained by long-lasting central engine activity. We have developed a shell model code to address the question of how X-ray flares are produced within the framework of the internal shock model. The shell model creates randomized GRB explosions from a central engine with multiple shells and follows those shells as they collide, merge, and spread, producing prompt emission and X-ray flares. We pay special attention to the time history of central engine activity, internal shocks, and observed flares, but do not calculate the shock dynamics and radiation processes in detail. Using the empirical Ep -Eiso (Amati) relation with an assumed Band function spectrum for each collision and an empirical flare temporal profile, we calculate the gamma-ray (Swift/BAT band) and X-ray (Swift/XRT band) lightcurves for arbitrary central engine activity and compare the model results with the observational data. We show that the observed X-ray flare phenomenology can be explained within the internal shock model. The number, width, and occurring time of flares are then used to diagnose the central engine activity, putting constraints on the energy, ejection time, width, and number of ejected shells. We find that the observed X-ray flare time history generally reflects the time history of the central engine, which reactivates multiple times after the prompt emission phase with progressively reduced energy. The same shell model predicts an external shock X-ray afterglow component, which has a shallow decay phase due to the initial pile-up of shells onto the blast wave. However, the predicted X-ray afterglow is too bright as compared with the observed flux level, unless εe is as low

  11. X-ray flares of γ-ray bursts: Quakes of solid quark stars?

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A star-quake model is proposed to understand X-ray flares of both long and short γ-ray bursts (GRBs) in a solid quark star regime. Two kinds of central engines for GRBs are available if pulsar-like stars are actually (solid) quark stars, i.e., the SNE-type GRBs and the SGR-type GRBs. It is found that a quark star could be solidified about 103 to 106 s later after its birth if the critical temperature of phase transi- tion is a few Metga-electron-volts, and then a new source of free energy (i.e., elastic and gravitational ones, rather than rotational or magnetic energy) could be possible to power GRB X-ray flares.

  12. X-Ray Flares of Gamma-Ray Bursts: Quakes of Solid Quark Stars?

    CERN Document Server

    Xu, Renxin

    2008-01-01

    We propose a star-quake model to understand X-ray flares of both long and short Gamma-ray bursts (GRBs) in a solid quark star regime. Two kinds of central engines for GRBs are available if pulsar-like stars are actually (solid) quark stars, i.e., the SNE-type GRBs and the SGR-type GRBs. It is found that a quark star could be solidified about 10^3 to 10^6 s later after its birth if the critical temperature of phase transition is a few MeV, and then a new source of free energy (i.e., elastic and gravitational ones, rather than rotational or magnetic energy) could be possible to power GRB X-ray flares.

  13. Numbers of Electrons in Solar Flares as Deduced from Microwave and X-Ray Bursts

    Institute of Scientific and Technical Information of China (English)

    YU Xing-Feng; YAO Jin-Xing

    2001-01-01

    We discuss whether the numbers of x-ray and radio-produced electrons in solar flares are the same. The number of radio-produced electrons that is estimated with an inhomogeneous source increases by a factor of 103 - 104because of the inhomogeneity and the decreased magnetic field (B = 120 G) of the radio source. The number of x-ray-produced electrons decreases by a factor of 10 - 30 due to the increase of the number density of ions (3 × 1010 cm-3). These are the reasons why the number of radio-produced electrons is approximately equal tothat of x-ray-produced electrons in the 1981 April 27 burst.

  14. Photosphere emission in the X-ray flares of swift gamma-ray bursts and implications for the fireball properties

    International Nuclear Information System (INIS)

    X-ray flares of gamma-ray bursts (GRBs) are usually observed in the soft X-ray range and the spectral coverage is limited. In this paper, we present an analysis of 32 GRB X-ray flares that are simultaneously observed by both Burst Alert Telescope and X-Ray Telescope on board the Swift mission, so that a joint spectral analysis with a wider spectral coverage is possible. Our results show that the joint spectra of 19 flares are fitted with the absorbed single power law or the Band function models. More interestingly, the joint spectra of the other 13 X-ray flares are fitted with the absorbed single power-law model plus a blackbody component. Phenomenally, the observed spectra of these 13 flares are analogous to several GRBs with a thermal component, but only with a much lower temperature of kT = 1 ∼ 3 keV. Assuming that the thermal emission is the photosphere emission of the GRB fireball, we derive the fireball properties of the 13 flares that have redshift measurements, such as the bulk Lorentz factor Γph of the outflow. The derived Γph range from 50 to 150 and a relation of Γph to the thermal emission luminosity is found. It is consistent with the Γ0 – L iso relations that are derived for the prompt gamma-ray emission. We discuss the physical implications of these results within the content of jet composition and the radiation mechanism of GRBs and X-ray flares.

  15. Gamma-Ray Burst long lasting X-ray flaring activity

    CERN Document Server

    Bernardini, M G; Chincarini, G; Guidorzi, C; Mao, J; Pasotti, F

    2010-01-01

    We complete the flare observational picture analysing the late time (i.e. t_{pk} >~ 1000 s) flares observed by Swift in the 0.3-10 keV energy band. The aim is to extend the knowledge of the temporal and energetic properties of X-ray flares up to 3 orders of magnitude in time in order to identify possible differences in the mechanism producing the early and late time flaring emission, if any. This requires the complete understanding of the observational biases affecting the detection of X-ray flares superimposed on a fading continuum at t > 1000 s. We find that the width of flares increases with time up to 10^6 s, and the linear relation between decay time and rise time still holds for late time flares. Late time flares are less energetic than early time flares by at least 1 order of magnitude, and they are also dimmer, being the peak luminosity anticorrelated with the peak time. Whatever produces each X-ray flare keeps memory of the previous GRB history, starting from the prompt emission, and it has to be cap...

  16. Energetics of impulsive solar flares: Correlating BATSE hard x-ray bursts and the solar atmosphere's soft x-ray response

    Science.gov (United States)

    Newton, Elizabeth

    1996-01-01

    This investigation has involved the correlation of BATSE-observed solar hard X-ray emission with the characteristics of soft X-ray emitting plasma observed by the Yohkoh Bragg Crystal Spectrometers. The goal was to test the hypothesis that localized electron beam heating is the dominant energy transport mechanism in impulsive flares, as formulated in the thick-target electron-heated model of Brown.

  17. The influence of the energy emitted by solar flare soft X-ray bursts on the propagation of their associated interplanetary shock waves

    Science.gov (United States)

    Pinter, S.; Dryer, M.

    1985-01-01

    The relationship between the thermal energy released from 29 solar flares and the propagation features of their associated interplanetary shock waves that were detected at 1 AU is investigated. The 29 interplanetary shock waves were identified unambiguously and their tracking from each solar flare was deduced by tracking their associated interplanetary type-II radio emission. The thermal energy released in the solar flares was estimated from the time-intensity profiles of 1-8 A soft X-ray bursts from each flare. A good relationship is found between the flares' thermal energy with the IP shock-waves' transient velocity and arrival time at the earth - that is, the largest flare energy released is associated with the faster shock waves. Finally, a possible scenario of formation of a shock wave during the early phase of the flare and its propagation features is discussed.

  18. Characteristic studies on solar x-ray flares and solar radio bursts during descending phases of solar cycles 22 and 23

    International Nuclear Information System (INIS)

    In this paper, a comparative study between the solar X-ray flares and solar radio bursts in terms of their duration and energy has been done. This has been done by analyzing the data in a statistical way covering the descending phase of the 22nd and 23rd solar cycles. It has been observed that the most probable value of duration of both solar X-ray flares and solar radio bursts remain same for a particular cycle. There is a slight variation in the most probable value of duration in going from 22nd cycle to 23rd cycle in the case of both kinds of events. This small variation may be due to the variation of polar field. A low correlation has been observed between energy fluxes in solar X-ray flares and in solar radio bursts. This has been attributed to the non symmetric contribution of energy to the solar radio and X-ray band controlled by solar magnetic field

  19. Joint Spectral Analysis for Early Bright X-ray Flares of -Ray Bursts with Swift BAT and XRT Data

    Indian Academy of Sciences (India)

    Fang-Kun Peng; You-Dong Hu; Xiang-Gao Wang; Rui-Jing Lu; En-Wei Liang

    2014-09-01

    A joint spectral analysis for early bright X-ray flares that were simultaneously observed with Swift BAT and XRT are present. Both BAT and XRT lightcurves of these flares are correlated. Our joint spectral analysis shows that the radiations in the two energy bands are from the same spectral component, which can be well fitted with a single power-law. Except for the flares in GRBs 060904B and 100906A, the photon spectral indices are < 2.0, indicating the peak energies (p) of the prompt -rays should be above the high energy end of the BAT band.

  20. X-ray flares from propagation instabilities in long Gamma-Ray Burst jets

    OpenAIRE

    Lazzati, Davide; Blackwell, Chris H.; Morsony, Bran J.; Begelman, Mitch C.

    2010-01-01

    We present a numerical simulation of a gamma-ray burst jet from a long-lasting engine in the core of a 16 solar mass Wolf-Rayet star. The engine is kept active for 6000 s with a luminosity that decays in time as a power-law with index -5/3. Even though there is no short time-scale variability in the injected engine luminosity, we find that the jet's kinetic luminosity outside the progenitor star is characterized by fluctuations with relatively short time scale. We analyze the temporal charact...

  1. Internal energy dissipation of gamma-ray bursts observed with Swift: Precursors, prompt gamma-rays, extended emission, and late X-ray flares

    International Nuclear Information System (INIS)

    We jointly analyze the gamma-ray burst (GRB) data observed with Burst Alert Telescope (BAT) and X-ray Telescope on board the Swift mission to present a global view on the internal energy dissipation processes in GRBs, including precursors, prompt gamma-ray emission, extended soft gamma-ray emission, and late X-ray flares. The Bayesian block method is utilized to analyze the BAT light curves to identify various emission episodes. Our results suggest that these emission components likely share the same physical origin, which is the repeated activation of the GRB central engine. What we observe in the gamma-ray band may be a small part of more extended underlying activities. The precursor emission, which is detected in about 10% of Swift GRBs, is preferably detected in those GRBs that have a massive star core-collapse origin. The soft extended emission tail, on the other hand, is preferably detected in those GRBs that have a compact star merger origin. Bright X-ray emission is detected during the BAT quiescent phases prior to subsequent gamma-ray peaks, implying that X-ray emission may be detectable prior the BAT trigger time. Future GRB alert instruments with soft X-ray capability are essential for revealing the early stages of GRB central engine activities, and shedding light on jet composition and the jet launching mechanism in GRBs.

  2. X-ray Emission from Solar Flares

    Indian Academy of Sciences (India)

    Rajmal Jain; Malini Aggarwal; Raghunandan Sharma

    2008-03-01

    Solar X-ray Spectrometer (SOXS), the first space-borne solar astronomy experiment of India was designed to improve our current understanding of X-ray emission from the Sun in general and solar flares in particular. SOXS mission is composed of two solid state detectors, viz., Si and CZT semiconductors capable of observing the full disk Sun in X-ray energy range of 4–56 keV. The X-ray spectra of solar flares obtained by the Si detector in the 4–25 keV range show evidence of Fe and Fe/Ni line emission and multi-thermal plasma. The evolution of the break energy point that separates the thermal and non-thermal processes reveals increase with increasing flare plasma temperature. Small scale flare activities observed by both the detectors are found to be suitable to heat the active region corona; however their location appears to be in the transition region.

  3. X-ray Studies of Flaring Plasma

    Indian Academy of Sciences (India)

    B. Sylwester; J. Sylwester; K. J. H. Phillips

    2008-03-01

    We present some methods of X-ray data analysis employed in our laboratory for deducing the physical parameters of flaring plasma. For example, we have used a flare well observed with Polish instrument RESIK aboard Russian CORONAS-F satellite. Based on a careful instrument calibration, the absolute fluxes in a number of individual spectral lines have been obtained. The analysis of these lines allows us to follow the evolution of important thermodynamic parameters characterizing the emitting plasma throughout this flare evolution.

  4. The smallest hard X-ray flare?

    Science.gov (United States)

    Glesener, Lindsay; Krucker, Sam; Hannah, Iain; Smith, David M.; Grefenstette, Brian; Marsh, Andrew; Hudson, Hugh S.; White, Stephen M.; Chen, Bin

    2016-05-01

    We report a NuSTAR observation of a small solar flare on 2015 September 1, estimated to be on the order of a GOES class A.05 flare in brightness. This flare is fainter than any hard X-ray (HXR) flares in the existing literature, and with a peak rate of only ∼5 counts s‑1 detector‑1 observed by RHESSI, is effectively the smallest that can just barely be detected by the current standard (indirectly imaging) solar HXR instrumentation, though we expect that smaller flares will continue to be discovered as instrumental and observational techniques progress. The flare occurred during a solar observation by the highly sensitive NuSTAR astrophysical HXR spacecraft, which used its direct focusing optics to produce detailed flare spectra and images. The flare exhibits properties commonly observed in larger flares, including a fast rise and more gradual decay, and similar spatial dimensions to the RHESSI microflares. We will discuss the presence of non-thermal (flare-accelerated) electrons during the impulsive phase. The flare is small in emission measure, temperature, and energy, though not in physical dimensions. Its presence is an indication that flares do indeed scale down to smaller energies and retain what we customarily think of as “flarelike” properties.

  5. Short-living Supermassive Magnetar Model for the Early X-ray Flares Following Short GRBs

    Institute of Scientific and Technical Information of China (English)

    Wei-Hong Gao; Yi-Zhong Fan

    2006-01-01

    We suggest a short-lived supermassive magnetar model to account for the X-ray flares following short γ-ray bursts. In this model the central engine of the short γ-ray bursts is a supermassive millisecond magnetar, formed in coalescence of double neutron stars. The X-ray flares are powered by the dipole radiation of the magnetar. When the magnetar has lost a significant part of its angular momentum, it collapses to a black hole and the X-ray flares cease abruptly.

  6. The observers' view of (very) long X-ray bursts: they are super!

    OpenAIRE

    Kuulkers, Erik

    2003-01-01

    In many X-ray point sources on the sky, the X-ray emission arises because hydrogen and/or helium is accreted onto a neutron star from a nearby donor star. When this matter settles on the neutron star surface, it will undergo nuclear fusion. For a large range of physical parameters the fusion is unstable. The resulting thermo-nuclear explosions last from seconds to minutes. They are observed as short flares in X-rays and are called `type I X-ray bursts'. Recently, hours-long X-ray flares have ...

  7. X-ray bursts observed with JEM-X

    DEFF Research Database (Denmark)

    Brandt, Søren Kristian; Chenevez, Jérôme; Lund, Niels; Budtz-Jørgensen, Carl; Westergaard, Niels Jørgen Stenfeldt

    We report on the search for X-ray bursts in the JEM-X X-ray monitor on INTEGRAL during the first two years of operations. More than 350 bursts from 25 different type-I X-ray burst sources were found.......We report on the search for X-ray bursts in the JEM-X X-ray monitor on INTEGRAL during the first two years of operations. More than 350 bursts from 25 different type-I X-ray burst sources were found....

  8. X-ray bursts observed with JEM-X

    DEFF Research Database (Denmark)

    Brandt, Søren Kristian; Chenevez, Jérôme; Lund, Niels;

    2006-01-01

    We report on the search for X-ray bursts in the JEM-X X-ray monitor on INTEGRAL during the first two years of operations. More than 350 bursts from 25 different type-I X-ray burst sources were found.......We report on the search for X-ray bursts in the JEM-X X-ray monitor on INTEGRAL during the first two years of operations. More than 350 bursts from 25 different type-I X-ray burst sources were found....

  9. Analysis of ultraviolet and X-ray observations of three homologous solar flares from SMM

    International Nuclear Information System (INIS)

    Three homologous flares observed in the UV lines of Fe XXI and O V and in X-rays from the SMM were studied. It was found that: (1) the homology of the flares was most noticeable in Fe XXI and soft X-ray emissions; (2) the three flares shared many of the same loop footprints which were located in O V bright kernals associated with hard X-ray bursts; and (3) in spite of the strong spatial homology, the temporal evolution in UV and X-ray emissions varied from flare to flare. A comparison between the UV observations and photospheric magnetograms revealed that the basic flare configuration was a complex loop system consisting of many loops or bundles of loops

  10. High-energy gamma-rays from GRB X-ray flares

    International Nuclear Information System (INIS)

    The recent detection of X-ray flares during the afterglow phase of gamma-ray bursts (GRBs) suggests an inner-engine origin, at radii inside the forward shock. There must be inverse Compton (IC) emission arising from such flare photons scattered by forward shock afterglow electrons when they are passing through the forward shock. We find that this IC emission produces high energy gamma-ray flares, which may be detected by AGILE, GLAST and ground-based TeV telescopes. The anisotropic IC scattering between flare photons and forward shock electrons does not affect the total IC component intensity, but cause a time delay of the IC component peak relative to the flare peak. We speculate that this IC component may already have been detected by EGRET from a very strong burst--GRB940217. Future observations by GLAST may help to distinguish whether X-ray flares originate from late central engine activity or from external shocks

  11. YOHKOH remnants: partially occulted flares in hard X-rays

    OpenAIRE

    M. Tomczak

    2009-01-01

    Flares being partially occulted by the solar limb, are the best reservoir of our knowledge about hard X-ray loop-top sources. Recently, the survey of partially occulted flares observed by the RHESSI has been published (Krucker & Lin 2008). The extensive YOHKOH database still awaits such activities. This work is an attempt to fill this gap. Among from 1286 flares in the YOHKOH Hard X-ray Telescope Flare Catalogue, for which the hard X-ray images had been enclosed, we identified 98 events that ...

  12. Swift XRT Observations of X-ray Flares in GRB Afterglows

    OpenAIRE

    Burrows, David N.; Romano, P; Godet, O.; Falcone, A; Pagani, C.; Cusumano, G.; Campana, S.; Chincarini, G.; Hill, J E; Giommi, P.; Goad, M. R.; Kennea, J. A.; Kobayashi, S; Meszaros, P.; Nousek, J. A.

    2005-01-01

    The Swift XRT has been observing GRB afterglows since December 23, 2004. Three-quarters of these observations begin within 300 s of the burst onset, providing an unprecendented look at the behavior of X-ray emission from GRB afterglows in the first few hours after the burst. While most of the early afterglows have smoothly declining lightcurves, a substantial fraction has large X-ray flares on short time-scales. We suggest that these flares provide support for models with extended central eng...

  13. Directivity of non-thermal X-ray emission from solar flares

    International Nuclear Information System (INIS)

    An attempt has been made in the present work to reveal the directivity of solar non-thermal X-ray emission using the data obtained from the Prognoz and Explorer satellites. The frequency of occurrence of X-ray bursts and the mean intensities of the emission are studied as a function of distance from the central meridian. The most complete statistics have been obtained for the 4-24 keV X-ray bursts for the period 1970-1973. The X-ray burst frequency of occurrence normalized to the corresponding Hα flare frequency increases towards the solar limb. During the studied period this trend is more pronounced to the east than to the west. Distributions of the mean intensities of X-ray bursts are very similar to those of the frequency of occurrence of X-ray bursts; the effect is more noticeable for the low intensity bursts. The effect of the east-west asymmetry for Hα flares has been found to vary in magnitude and direction during the 20th solar activity cycle. (Auth.)

  14. In-progress X-ray Flare Forecasting

    Science.gov (United States)

    Balasubramaniam, K. S.; Winter, L. M.

    2015-12-01

    Solar X-ray flares release intense amounts of radiation and can be associated with subsequent changes in the geomagnetic field as well as a large influx of solar energetic particles. From analyses of 50,000 flares detected with the NOAA GOES satellites over the past 40 years, Winter & Balasubramaniam (2015) introduced a flare phase diagram where X-ray observables indicating flare temperature and background solar activity levels can be used to separate flares of different peak flux. We present results from adapting this method into a real-time forecast tool. Real-time GOES X-ray observations are used to predict expected flare class, with updates made every 1-minute. KSB, in part by the Air Force Office of Scientific Research on "the Physics of Coupled Flares and CME Systems". LM was supported by AER, and in part by a contract supported by AFRL/RV

  15. An Extended Burst Tail from SGR 1900+14 with a Thermal X-ray Spectrum

    Science.gov (United States)

    Lenters, Geoffrey T.; Woods, Peter M.; Goupell, Johnathan E.; Kouveliotou, Chryssa; Goegues, Ersin; Hurley, Kevin; Frederiks, Dmitry; Golenetskii, Sergey; Swank, Jean; Six, N. Frank (Technical Monitor)

    2002-01-01

    The Soft Gamma Repeater, SGR 1900+14, entered a new phase of activity in April 2001 initiated by the intermediate flare recorded on April 18. Ten days following this flare, we discovered an abrupt increase in the source flux between consecutive RXTE orbits. This X-ray flux excess decayed over the next several minutes and was subsequently linked to a high fluence burst from SGR 1900+14 recorded by other spacecraft (Ulysses and KONUS) while the SGR was Earth-occulted for RXTE. We present here spectral and temporal analysis of both the burst of 28 April and the long X-ray tail following it. We draw comparisons with other bursts and flares from SGR 1900+14 which have shown extended X-ray excesses (e.g. 1998 August 29) and discuss their physical origin.

  16. The Fermi-GBM X-ray burst monitor

    Science.gov (United States)

    Linares, M.; Fermi GBM X-ray Burst Collaboration

    2010-12-01

    We discuss the first results of the Fermi-GBM all-sky search for X-ray bursts. The very large field of view and X-ray response of the Fermi-GBM make it a unique instrument to study rare, bright and short-lived X-ray bursts. We are performing a systematic search that exploits such capabilities. We present results on long/intermediate type I X-ray bursts, an unusual kind of thermonuclear bursts from accreting neutron stars, and show how Fermi-GBM is giving for the first time robust measurements of their recurrence time.

  17. Long X-ray burst monitoring with INTEGRAL

    DEFF Research Database (Denmark)

    X-ray bursts are thermonuclear explosions on the surface of accreting neutron stars in low mass X-ray binary systems. In the frame of the INTEGRAL observational Key Programme over the Galactic Center a good number of the known X-ray bursters are frequently being monitored. An international....... Of special interest are low luminosity bursting sources that exhibit X-ray bursts of very different durations allowing to study the transition from a hydrogen-rich bursting regime to a pure helium regime and from helium burning to carbon burning. I will present results obtained from INTEGRAL archive...

  18. X-ray Variability of AGN and the Flare Model

    OpenAIRE

    Goosmann, R. W.; Czerny, B.; Dumont, A. -M.; Mouchet, M.; Rozanska, A.

    2004-01-01

    Short-term variability of X-ray continuum spectra has been reported for several Active Galactic Nuclei. Significant X-ray flux variations are observed within time scales down to 10^3-10^5 seconds. We discuss short variability time scales in the frame of the X-ray flare model, which assumes the release of a large hard X-ray flux above a small portion of the accretion disk. The resulting observed X-ray spectrum is composed of the primary radiation and of a reprocessed Compton reflection compone...

  19. UNIVERSAL BEHAVIOR OF X-RAY FLARES FROM BLACK HOLE SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    Wang, F. Y.; Dai, Z. G.; Yi, S. X. [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China); Xi, S. Q., E-mail: fayinwang@nju.edu.cn, E-mail: dzg@nju.edu.cn [Department of Physics and GXU-NAOC Center for Astrophysics and Space Sciences, Guangxi University, Nanning 530004 (China)

    2015-01-01

    X-ray flares have been discovered in black hole systems such as gamma-ray bursts, the tidal disruption event Swift J1644+57, the supermassive black hole Sagittarius A* at the center of our Galaxy, and some active galactic nuclei. Occurrences of X-ray flares are always accompanied by relativistic jets. However, it is still unknown whether or not there is a physical analogy among such X-ray flares produced in black hole systems spanning nine orders of magnitude in mass. Here, we report observed data of X-ray flares and show that they have three statistical properties similar to solar flares, including power-law distributions of their energies, durations, and waiting times, which can be explained by a fractal-diffusive, self-organized criticality model. These statistical similarities, together with the fact that solar flares are triggered by a magnetic reconnection process, suggest that all of the X-ray flares are consistent with magnetic reconnection events, implying that their concomitant relativistic jets may be magnetically dominated.

  20. Linking burst-only X-ray binary sources to faint X-ray transients

    OpenAIRE

    Campana, S.

    2009-01-01

    Burst-only sources are X-ray sources showing up only during short bursts but with no persistent emission (at least with the monitoring instrument which led to their discovery). These bursts have spectral characteristics consistent with thermonuclear (type I) burst from the neutron star surface, linking burst-only sources to neutron star X-ray binary transients. We have carried out a series of snapshot observations of the entire sample of burst-only sources with the Swift satellite. We found a...

  1. The coevolution of decimetric millisecond spikes and hard X-ray emission during solar flares

    Science.gov (United States)

    Aschwanden, Markus J.; Guedel, Manuel

    1992-01-01

    Results are presented of an analysis of a comprehensive data set of 27 solar flares with decimetric millisecond spikes between 1980 and 1989, simultaneously observed with the Zuerich radio spectrometers and the Hard X-ray Burst Spectrometer on the SMM spacecraft. Two contradictory relationships of the coevolution of hard X-ray and spiky radio emissions during flares are found: the temporal evolution of both emissions reveals a close functional dependence, but there is a substantial time delay between the two emissions. Five possible scenarios for the hard-X-ray-associated radio spike emission which may account for both their detailed coevolution and their substantial intervening time delay are discussed. All five scenarios are able to explain both the close coevolution of hard X-ray and radio emission as well as their mutual delay to some degree, but none of them can explain all observational aspects in a simple way.

  2. Deka-keV X-ray observations of solar bursts with WATCH/GRANAT: frequency distributions of burst parameters

    DEFF Research Database (Denmark)

    Crosby, N.; Vilmer, N.; Lund, Niels;

    1998-01-01

    Solar flare observations in the deka-keV range are performed by the WATCH experiment on board the GRANAT satellite. The WATCH experiment is presented, including the energy calibration as applied in the present work. The creation of the solar burst catalogue covering two years of observation...... is described and some examples of solar observations are given. The estimated energy releases in the flares presented here are found to extend below the range of hard X-ray flares which were previously studied by ISEE-3 and HXRBS/SMM detectors. The X-ray emitting component cannot be exclusively explained...... be observed as low as 10 keV. A statistical study is performed on the total WATCH solar database and frequency distributions are built on measured X-ray flare parameters. It is also investigated how the properties of these frequency distributions behave when subgroups of events defined by different ranges...

  3. X-ray Emission Characteristics of Flares Associated with CMEs

    Indian Academy of Sciences (India)

    Malini Aggarwal; Rajmal Jain; A. P. Mishra; P. G. Kulkarni; Chintan Vyas; R. Sharma; Meera Gupta

    2008-03-01

    We present the study of 20 solar flares observed by ``Solar X-ray Spectrometer (SOXS)” mission during November 2003 to December 2006 and found associated with coronal mass ejections (CMEs) seen by LASCO/SOHO mission. In this investigation, X-ray emission characteristics of solar flares and their relationship with the dynamics of CMEs have been presented.We found that the fast moving CMEs, i.e., positive acceleration are better associated with short rise time (< 150 s) flares. However, the velocity of CMEs increases as a function of duration of the flares in both 4.1–10 and 10–20 keV bands. This indicates that the possibility of association of CMEs with larger speeds exists with long duration flare events. We observed that CMEs decelerate with increasing rise time, decay time and duration of the associated X-ray flares. A total 10 out of 20 CMEs under current investigation showed positive acceleration, and 5 of them whose speed did not exceed 589 km/s were associated with short rise time (< 150 s) and short duration (< 1300 s) flares. The other 5 CMEs were associated with long duration or large rise time flare events. The unusual feature of all these positive accelerating CMEs was their low linear speed ranging between 176 and 775 km/s. We do not find any significant correlation between X-ray peak intensity of the flares with linear speed as well as acceleration of the associated CMEs. Based on the onset time of flares and associated CMEs within the observing cadence of CMEs by LASCO, we found that in 16 cases CME preceded the flare by 23 to 1786 s, while in 4 cases flare occurred before the CME by 47 to 685 s. We argue that both events are closely associated with each other and are integral parts of one energy release system.

  4. INTEGRAL monitoring of unusually long X-ray bursts

    DEFF Research Database (Denmark)

    Thermonuclear bursts on the surface of accreting neutron stars in low mass X-ray binaries have been studied for many years and have in a few cases confirmed theoretical models of nuclear ignition and burning mechanisms. The large majority of X-ray bursts last less than 100s. A good number of the...... known X-ray bursters are frequently observed by INTEGRAL, in particular in the frame of the Key Programmes. Taking advantage of the INTEGRAL instrumentation, an international collaboration led by the JEM-X team at the Danish National Space Institute has been monitoring the occurrence of uncommon burst...... events lasting more than a few minutes. Of special interest are exceptional X-ray bursts which duration about a few tens of minutes is intermediate between usual short bursts and hour long superbursts. The processes driving such long bursts are not yet fully understood: depending on the composition of...

  5. The Fermi–GBM Three-year X-Ray Burst Catalog

    Science.gov (United States)

    Jenke, P. A.; Linares, M.; Connaughton, V.; Beklen, E.; Camero-Arranz, A.; Finger, M. H.; Wilson-Hodge, C. A.

    2016-08-01

    The Fermi Gamma-ray Burst Monitor (GBM) is an all-sky gamma-ray monitor well known in the gamma-ray burst (GRB) community. Although GBM excels in detecting the hard, bright extragalactic GRBs, its sensitivity above 8 keV and its all-sky view make it an excellent instrument for the detection of rare, short-lived Galactic transients. In 2010 March, we initiated a systematic search for transients using GBM data. We conclude this phase of the search by presenting a three-year catalog of 1084 X-ray bursts. Using spectral analysis, location, and spatial distributions we classified the 1084 events into 752 thermonuclear X-ray bursts, 267 transient events from accretion flares and X-ray pulses, and 65 untriggered gamma-ray bursts. All thermonuclear bursts have peak blackbody temperatures broadly consistent with photospheric radius expansion (PRE) bursts. We find an average rate of 1.4 PRE bursts per day, integrated over all Galactic bursters within about 10 kpc. These include 33 and 10 bursts from the ultra-compact X-ray binaries 4U 0614+09 and 2S 0918-549, respectively. We discuss these recurrence times and estimate the total mass ejected by PRE bursts in our Galaxy.

  6. Universal Behavior of X-ray Flares from Black Hole Systems

    CERN Document Server

    Wang, F Y; Yi, S X; Xi, S Q

    2014-01-01

    X-ray flares have been discovered in black hole systems, such as gamma-ray bursts, the tidal disruption event Swift J1644+57, the supermassive black hole Sagittarius A$^*$ at the center of our Galaxy, and some active galactic nuclei. Their occurrences are always companied by relativistic jets. However, it is still unknown whether there is a physical analogy among such X-ray flares produced in black hole systems spanning nine orders of magnitude in mass. Here we report the observed data of X-ray flares, and show that they have three statistical properties similar to solar flares, including power-law distributions of energies, durations, and waiting times, which both can be explained by a fractal-diffusive self-organized criticality model. These statistical similarities, together with the fact that solar flares are triggered by a magnetic reconnection process, suggest that all of the X-ray flares are consistent with magnetic reconnection events, implying that their concomitant relativistic jets may be magnetica...

  7. X-Ray Observations of Gamma-Ray Burst Afterglows

    OpenAIRE

    Frontera, Filippo

    2004-01-01

    The discovery by the BeppoSAX satellite of X-ray afterglow emission from the gamma-ray burst which occurred on 28 February 1997 produced a revolution in our knowledge of the gamma-ray burst phenomenon. Along with the discovery of X-ray afterglows, the optical afterglows of gamma-ray bursts were discovered and the distance issue was settled, at least for long $\\gamma$-ray bursts. The 30 year mystery of the gamma-ray burst phenomenon is now on the way to solution. Here I rewiew the observationa...

  8. INTEGRAL monitoring of unusually long X-ray bursts

    DEFF Research Database (Denmark)

    Chenevez, Jérôme; Falanga, M.; Kuulkers, E.;

    2008-01-01

    exceptional burst events lasting more than ~10 minutes. Half of the dozen so-called intermediate long bursts registered so far have been observed by INTEGRAL. The goal is to derive a comprehensive picture of the relationship between the nuclear ignition processes and the accretion states of the system leading......X-ray bursts are thermonuclear explosions on the surface of accreting neutron stars in X-ray binaries. As most of the known X-ray bursters are frequently observed by INTEGRAL, an international collaboration have been taking advantage of its instrumentation to specifically monitor the occurrence of...

  9. X-ray spectra of bursting neutron stars

    International Nuclear Information System (INIS)

    The global properties of type-I x-ray bursts can be successfully accounted for by the thermonuclear shell flash model of accreting neutron stars. According to this model, the luminosity of a relatively large burst approaches to the Eddington luminosity. We calculate the atmospheric structure and the photon energy spectrum of x-ray bursting neutron star taking account of comptonization. From the x-ray spectrum, theoretical color temperature-luminosity diagram is obtained. Observational color temperature-luminosity diagram of x-ray burster is constructed using data of Japanese x-ray sutellite Tenma. Comparing our theoretical diagram with observational ones, we can estimate a mass-radius relation of neutron stars and distances to the galactic center. (Mori, K.)

  10. Soft X-ray Pulsations in Solar Flares

    CERN Document Server

    Simões, Paulo J A; Fletcher, Lyndsay

    2014-01-01

    The soft X-ray emissions of solar flares come mainly from the bright coronal loops at the highest temperatures normally achieved in the flare process. Their ubiquity has led to their use as a standard measure of flare occurrence and energy, although the bulk of the total flare energy goes elsewhere. Recently Dolla et al. (2012) noted quasi-periodic pulsations (QPP) in the soft X-ray signature of the X-class flare SOL2011-02-15, as observed by the standard photometric data from the GOES (Geostationary Operational Environmental Satellite) spacecraft. We analyze the suitability of the GOES data for this kind of analysis and find them to be generally valuable after Sept. 2010 (GOES-15). We then extend Dolla et al. results to a list of X-class flares from Cycle 24, and show that most of them display QPP in the impulsive phase. During the impulsive phase the footpoints of the newly-forming flare loops may also contribute to the observed soft X-ray variations. The QPP show up cleanly in both channels of the GOES dat...

  11. Evidence of the radio-quiet hard X-ray precursor of the 13 December 2006 solar flare

    International Nuclear Information System (INIS)

    We report multi-wavelength investigation of the pre-impulsive phase of the 13 December 2006 X-class solar flare. We use hard X-ray data from the anticoincidence system of spectrometer onboard INTEGRAL (ACS) jointly with soft X-ray data from the GOES-12 and Hinode satellites. Radio data are from Nobeyama and Learmonth solar observatories and from the Culgoora Solar Radio Spectrograph. The main finding of our analysis is a spiky increase of the ACS count rate accompanied by surprisingly gradual and weak growth of microwave emission and without detectable radio emission at meter and decimeter wavelengths about 10 min prior to the impulsive phase of the solar flare. At the time of this pre-flare hard X-ray burst the onset of the GOES soft X-ray event has been reported, positive derivative of the GOES soft X-ray flux started to rise and a bright spot has appeared in the images of the Hinode X-ray telescope (XRT) between the flare ribbons near the magnetic inversion line close to the sources of thermal and non-thermal hard X-ray emission observed by Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) during the flare. These facts we consider as evidences of solar origin of the increased pre-flare ACS count rate. We briefly discuss a possible cause of the pre-flare emission peculiarities. (authors)

  12. Which process will happen in GRB radiation zone based on X-ray flares data, Internal Shock or ICMART?

    Science.gov (United States)

    Jia, Lanwei; Zhang, Bing

    2015-08-01

    If the emission from the central engine ceases abruptly in Gamma-ray burst radiation zone where Internal Shock or ICMART process may happen, then the curvature effect of the relativistic shell will shape the observed light curves. Bright X-ray flares have been detected in the early X-ray light curves of nearly one-half of the burst population, and curvature effect has been invoked to interpret the decay segment of the X-ray flares. So we choose all X-ray flares which display a very neat light curve detected by Swift satellite from 2004 to 2014, and find that the shell in radiation zone still in acceleration, demonstrating ICMART process is happening in radiation zone for our GRB sample.

  13. X-ray flares in Orion young stars. I. Flare characteristics

    OpenAIRE

    Getman, Konstantin V.; Feigelson, Eric D.; Broos, Patrick S.; Micela, Giuseppina; Garmire, Gordon P.

    2008-01-01

    Pre-main sequence (PMS) stars are known to produce powerful X-ray flares which resemble magnetic reconnection solar flares scaled by factors up to 10^4. However, numerous puzzles are present including the structure of X-ray emitting coronae and magnetospheres, effects of protoplanetary disks, and effects of stellar rotation. To investigate these issues in detail, we examine 216 of the brightest flares from 161 PMS stars observed in the Chandra Orion Ultradeep Project (COUP). These constitute ...

  14. The X-ray quiescence of Swift J195509.6+261406 (GRB 070610): an optical bursting X-ray binary?

    NARCIS (Netherlands)

    N. Rea; P.G. Jonker; G. Nelemans; J.A. Pons; M.M. Kasliwal; S.R. Kulkarni; R. Wijnands

    2011-01-01

    We report on an ~63 ks Chandra observation of the X-ray transient Swift J195509.6+261406 discovered as the afterglow of what was first believed to be a long-duration gamma-ray burst (GRB 070610). The outburst of this source was characterized by unique optical flares on timescales of second or less,

  15. Microflares and the Statistics of X-ray Flares

    Czech Academy of Sciences Publication Activity Database

    Hannah, I.G.; Hudson, H. S.; Battaglia, M.; Christe, S.; Kašparová, Jana; Krucker, S.; Kundu, M.R.; Veronig, A.

    2011-01-01

    Roč. 159, 1-4 (2011), s. 263-300. ISSN 0038-6308 R&D Projects: GA ČR GP205/06/P135 Institutional research plan: CEZ:AV0Z10030501 Keywords : Sun * flares * X-rays Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 3.611, year: 2011

  16. X-ray flare properties of Sgr A*

    Science.gov (United States)

    Wang, Daniel; Yuan, Qiang

    2016-04-01

    Daily X-ray flaring represents an enigmatic phenomenon of Sgr A* --- the supermassive black hole at the center of our Galaxy. We report results from a systematic X-ray study of this phenomenon, based on extensive Chandra observations obtained from 1999 to 2012, totaling about 4.5 Ms. We detect flares, using a combination of the maximum likelihood and Markov Chain Monte Carlo methods, which allow for a direct accounting for the pile-up effect in the modeling of the flare lightcurves and an optimal use of the data, as well as the measurements of flare parameters, including their uncertainties. A total of 82 flares are detected. About one third of them are relatively faint, which were not detected previously. The observation-to-observation variation of the quiescent emission has an average root-mean-square of 6%-14%, including the Poisson statistical fluctuation of faint flares below our detection limits. We find no significant long-term variation in the quiescent emission and the flare rate over the 14 years. In particular, we see no evidence of changing quiescent emission and flare rate around the pericenter passage of the S2 star around 2002. We show clear evidence of a short-term clustering for the flares on time scale of 20-70 ks. We will also report new results on the spectral and lightcurve properties of the flares, as well as their fluence-duration relation after carefully accounting for the detection incompleteness and bias. Finally, we will use these results to constrain the origin and emission mechanism of the flares, which further helps to establish Sgr A* as a unique laboratory to understand the astrophysics of prevailing low-luminosity black holes in the Universe.

  17. Soft X-ray spectroscopy of solar flares - An overview

    Science.gov (United States)

    Doschek, G. A.

    1990-01-01

    An overview of the current status of high spectral resolution soft X-ray observations of solar flares is given. The review concentrates primarily on recent results and interpretations of results obtained from orbiting Bragg crystal spectrometers flow during the last solar maximum on the US DoD P78-1 spacecraft, the NASA SMM, and the ISAS Hinotori spacecraft. Results and several key issues regarding interpretation of the spectra are presented. Specifically, the dynamics of coronal flare plasmas as revealed by X-ray line profiles and wavelength shifts are discussed. Recent results concerning the theory of chromospheric evaporation are given. The temperature of coronal flare plasma is discussed within the context of a differential mission measure. Results concerning electron density measurements, nonequilibrium processes, and relative element abundances are also reviewed.

  18. The INTEGRAL view of intermediate long X-ray bursts

    DEFF Research Database (Denmark)

    CONCLUSIONS Most intermediate bursts are observed from low luminosity sources and are interpreted as long pure He bursts. If no H is accreted, they are consistent with the burning of a slowly accreted, thick He layer, in Ultra Compact X-ray Binaries (UCXB) where the donor star is probably a...

  19. Bright flares in supergiant fast X-ray transients

    Science.gov (United States)

    Shakura, N.; Postnov, K.; Sidoli, L.; Paizis, A.

    2014-08-01

    At steady low-luminosity states, supergiant fast X-ray transients (SFXTs) can be at the stage of quasi-spherical settling accretion on to slowly rotating magnetized neutron stars from the OB-companion winds. At this stage, a hot quasi-static shell is formed above the magnetosphere, the plasma entry rate into magnetosphere is controlled by (inefficient) radiative plasma cooling, and the accretion rate on to the neutron star is suppressed by a factor of ˜30 relative to the Bondi-Hoyle-Littleton value. Changes in the local wind velocity and density due to, e.g. clumps, can only slightly increase the mass accretion rate (a factor of ˜10) bringing the system into the Compton-cooling-dominated regime and led to the production of moderately bright flares (Lx ≲ 1036 erg s-1). To interpret the brightest flares (Lx > 1036 erg s-1) displayed by the SFXTs within the quasi-spherical settling accretion regimes, we propose that a larger increase in the mass accretion rate can be produced by sporadic capture of magnetized stellar wind plasma. At sufficiently low accretion rates, magnetic reconnection can enhance the magnetospheric plasma entry rate, resulting in copious production of X-ray photons, strong Compton cooling and ultimately in unstable accretion of the entire shell. A bright flare develops on the free-fall time-scale in the shell, and the typical energy released in an SFXT bright flare corresponds to the mass of the shell. This view is consistent with the energy released in SFXT bright flares (˜1038-1040 erg), their typical dynamic range (˜100) and with the observed dependence of these characteristics on the average unflaring X-ray luminosity of SFXTs. Thus, the flaring behaviour of SFXTs, as opposed to steady HMXBs, may be primarily related to their low X-ray luminosity allowing sporadic magnetic reconnection to occur during magnetized plasma entry into the magnetosphere.

  20. The Fermi-GBM 3-year X-ray Burst Catalog

    CERN Document Server

    Jenke, P A; Connaughton, V; Beklen, E; Camero-Arranz, A; Finger, M H; Wilson-Hodge, C A

    2016-01-01

    The Fermi Gamma Ray Burst Monitor (GBM) is an all sky gamma-ray monitor well known in the gamma-ray burst community. Although GBM excels in detecting the hard, bright extragalactic GRBs, its sensitivity above 8 keV and all-sky view make it an excellent instrument for the detection of rare, short-lived Galactic transients. In March 2010, we initiated a systematic search for transients using GBM data. We conclude this phase of the search by presenting a 3 year catalog of 1084 non-solar events. Using spectral analysis, location and spatial distributions we subdivided the 1084 events into 752 thermonuclear X-ray bursts, 267 transient events from accretion flares and X-ray pulses, and 65 untriggered gamma-ray bursts.

  1. X-Ray Emission from Flare Collapsing Trap

    Czech Academy of Sciences Publication Activity Database

    Karlický, Marian

    2006-01-01

    Roč. 122, 1-4 (2006), s. 161-168. ISSN 0038-6308 R&D Projects: GA AV ČR IAA3003202; GA AV ČR 1QS300120506; GA ČR GA205/04/0358 Institutional research plan: CEZ:AV0Z10030501 Keywords : solar flares * X-ray emission Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 3.789, year: 2006

  2. X-ray flare in XRF 050406: evidence for prolonged engine activity

    CERN Document Server

    Romano, P; Banat, P L; Burrows, D N; Campana, S; Chincarini, G; Covino, S; Malesani, D; Tagliaferri, G; Kobayashi, S; Zhang, B; Falcone, A D; Angelini, L; Barthelmy, S; Beardmore, A P; Capalbi, M; Cusumano, G; Giommi, P; Goad, M R; Godet, O; Grupe, D; Hill, J E; Kennea, J A; La Parola, V; Mangano, V; Mészáros, P; Morris, D C; Nousek, J A; O'Brien, P T; Osborne, J P; Parsons, A; Perri, M; Pagani, C; Page, K L; Wells, A A; Gehrels, N

    2006-01-01

    We present observations of XRF 050406, the first burst detected by Swift showing a flare in its X-ray light curve. During this flare, which peaks at t_peak ~210s after the BAT trigger, a flux variation of (delta F)/F~6 in a very short time (delta t)/t_peak<<1 was observed. Its measured fluence in the 0.2-10 keV band was ~1.4x10^-8 erg cm^-2, which corresponds to 1-15% of the prompt fluence. We present indications of spectral variations during the flare. We argue that the producing mechanism is late internal shocks, which implies that the central engine is still active at 210s, though with a reduced power with respect to the prompt emission. The X-ray light curve flattens to a very shallow slope with decay index of ~0.5 after ~4400s, which also supports continued central engine activity at late times. This burst is classified as an X-ray flash, with a relatively low fluence (~10^-7 erg cm^-2 in the 15-350 keV band, E_iso~10^51 erg), a soft spectrum (photon index 2.65), no significant flux above ~50 keV a...

  3. The discovery of X-ray bursts from a region in the constellation Norma

    International Nuclear Information System (INIS)

    A search through the first 15 months of data from X-ray detectors aboard the two Vela-5 satellites has revealed 20 count-rate enhancements at least 15 sigma above background. The detectors respond to X-rays in the energy band approx.3--12 keV. The collimator design permits direction determinations within a 12degree x 12degree error box. All of the observations are consistent with short X-ray bursts from distant point sources but not with incident charged-particle fluxes or with spacecraft electronic noise. Eleven of the observations above 15 sigma can be attributed to 10 X-ray flares (one outburst was observed by both spacecraft) located in a region centered at αapprox.16/sup h/, deltaapprox.-53degree in the constellation Norma. Another two of these 10 flares seen above the 15 sigma level were seen by the second spacecraft at levels of 9 sigma and 10 sigma. The observations are consistent with a single object as the source of all 10 outbursts. The most intense of these Norma flares was approximately 3/4 of the quiet phase Sco X-1 intensity. Flare durations were observed to be more than 2 s and less than 128 s for all of the events. The spectra varied considerably but were relatively hard compared to Sco X-1

  4. An X-ray flare from 47 Cas

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, Jeewan C.; Karmakar, Subhajeet, E-mail: jeewan@aries.res.in [Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital-263 001 (India)

    2015-02-01

    Using XMM-Newton observations, we investigate properties of a flare from the very active but poorly known stellar system 47 Cas. The luminosity at the peak of the flare is found to be 3.54 × 10{sup 30} erg s{sup −1}, which is ∼2 times higher than that at a quiescent state. The quiescent state corona of 47 Cas can be represented by two temperature plasma: 3.7 and 11.0 MK. The time-resolved X-ray spectroscopy of the flare show the variable nature of the temperature, the emission measure, and the abundance. The maximum temperature during the flare is derived as 72.8 MK. We infer the length of a flaring loop to be 3.3 × 10{sup 10} cm using a hydrodynamic loop model. Using the RGS spectra, the density during the flare is estimated as 4.0 × 10{sup 10} cm{sup −3}. The loop scaling laws are also applied when deriving physical parameters of the flaring plasma.

  5. Discovery of the optical polarization flare following the X-ray giant outburst of V0332+53.

    Science.gov (United States)

    Slowikowska, Agnieszka; Reig, Pablo; Krzeszowski, Krzysztof; Zejmo, M. Michal

    2016-07-01

    V0332+53 is a transient Be X-ray binary that went through a giant outburst between June 2015 and October 2015 registered by the Gamma-ray Burst Monitor (GMB) on board of the Fermi satellite. We present the discovery of a flare of linearly polarized optical light in V0332+53 that followed the X-ray outburst. We monitored the source with the multi-wavelength optical polarimeter RINGO3 on the 2-m fully robotic Liverpool Telescope located at the Observatorio del Roque de Los Muchachos on La Palma. RINGO3 measures polarization simultaneously in three spectral wavelength bands: blue (350-640 nm), green (650-760 nm) and red (770-1000 nm). The polarized optical flare went off around 90 days after the X-ray burst and lasted another 90 days in all three wavelength bands of RINGO3. Polarization degree reached up to 6% in blue and up to 4% in red, while the PA changed by more than 100 degrees during the flare. This is the first detection of optical polarization flare of high mass X-ray binary correlated with a preceding X-ray outburst. Our observations shed new light on the activities of X-ray binaries.

  6. Supercollapsars and their X-ray Bursts

    CERN Document Server

    Komissarov, S S

    2009-01-01

    The very first stars in the Universe can be very massive, frequently reaching $10^3M_\\odot$. If born in large numbers such massive stars can have strong impact on the subsequent star formation producing strong ionising radiation and contaminating the primordial gas with heavy elements. They would leave behind massive black holes that could act as seeds for growing supermassive black holes of active galactic nuclei. Given the anticipated fast rotation such stars would end their live as supermassive collapsars and drive powerful magnetically-dominated jets. In this letter we investigate the possibility of observing the bursts of high-energy emission similar to the Long Gamma Ray Bursts associated with normal collapsars. We show that during the collapse of supercollapsars, the Blandford-Znajek mechanism can extract up to $10^{56}$erg at a rate of few$\\times10^{52}$erg/s. Due to the higher intrinsic time scale and higher redshift the observed burst duration increases by a factor of $\\simeq 1000$ and can reach one...

  7. Repeated X-ray Flaring Activity in Sagittarius A*

    CERN Document Server

    Bélanger, G; Melia, F; Yusef-Zadeh, F; Ferrando, P; Porquet, D; Grosso, N; Warwick, R; Belanger, Guillaume; Goldwurm, Andrea; Melia, Fulvio; Yusef-Zadeh, Farah; Ferrando, Philippe; Porquet, Delphine; Grosso, Nicolas; Warwick, Robert

    2005-01-01

    Investigating the spectral and temporal characteristics of the X-rays coming from Sagittarius A* (Sgr A*) is essential to our development of a more complete understanding of the emission mechanisms in this supermassive black hole located at the center of our Galaxy. Several X-ray flares with varying durations and spectral features have already been observed from this object. Here we present the results of two long XMM-Newton observations of the Galactic nucleus carried out in 2004, for a total exposure time of nearly 500 ks. During these observations we detected two flares from Sgr A* with peak 2-10 keV luminosities about 40 times (L ~ 9x10^34 erg s−1) above the quiescent luminosity: one on 2004 March 31 and another on 2004 August 31. The first flare lasted about 2.5 ks and the second about 5 ks. The combined fit on the Epic spectra yield photon indeces of about 1.5 and 1.9 for the first and second flare respectively. This hard photon index strongly suggests the presence of an important population o...

  8. White-light flares, Hard X-Rays, and Heights

    Science.gov (United States)

    Martinez Oliveros, Juan Carlos; Hudson, Hugh S.; Krucker, Sam

    2016-05-01

    The white-light continuum of a solar flare was the first manifestation of a solar flare ever detected. Nevertheless, its mechanisms remain unknown, even today. Improved observations confirm the identification of white-light continuum emission and hard X-rays during the impulsive phase of a solar flare, both in space and in time, to within the observational limits. Two events observed near the limb, but not occulted by it (SOL2011-02-24 and SOL2012-02-18), show that these emissions appear to have physical heights lower than predicted by models by hundreds of kms, referring height to the location of optical-depth unity at disk center in the 500 nm continuum. We describe these results and place them in the context of the three extreme-limb events (within about 1o) reported by Krucker et al. (2015). The electrons responsible for hard X-ray bremsstrahlung coincide with the most intense flare energy release, but we do not presently understand the physics of energy transport nor the nature of particle acceleration apparently taking place at heights below the preflare temperature minimum.

  9. X-ray flares in Orion young stars. I. Flare characteristics

    CERN Document Server

    Getman, Konstantin V; Broos, Patrick S; Micela, Giuseppina; Garmire, Gordon P

    2008-01-01

    Pre-main sequence (PMS) stars are known to produce powerful X-ray flares which resemble magnetic reconnection solar flares scaled by factors up to 10^4. However, numerous puzzles are present including the structure of X-ray emitting coronae and magnetospheres, effects of protoplanetary disks, and effects of stellar rotation. To investigate these issues in detail, we examine 216 of the brightest flares from 161 PMS stars observed in the Chandra Orion Ultradeep Project (COUP). These constitute the largest homogeneous dataset of PMS, or indeed stellar flares at any stellar age, ever acquired. Our effort is based on a new flare spectral analysis technique that avoids nonlinear parametric modeling. It can be applied to much weaker flares and is more sensitive than standard methods. We provide a catalog with >30 derived flare properties and an electronic atlas for this unique collection of stellar X-ray flares. The current study (Paper I) examines the flare morphologies, and provides general comparison of COUP flar...

  10. A Strong X-Ray Burst from the Low Mass X-Ray Binary EXO0748-676

    OpenAIRE

    Wolff, Michael T.; Becker, Peter A.; Ray, Paul S.; Wood, Kent S.

    2005-01-01

    We have observed an unusually strong X-ray burst as a part of our regular eclipse timing observations of the low mass binary system EXO0748-676. The burst peak flux was 5.2x10^-8 ergs cm^-2 s^-1, approximately five times the normal peak X-ray burst flux observed from this source by RXTE. Spectral fits to the data strongly suggest that photospheric radius expansion occurred during the burst. In this Letter we examine the properties of this X-ray burst, which is the first example of a radius ex...

  11. High-Energy Gamma-Rays from GRB X-ray Flares

    CERN Document Server

    Wang, X Y; Mészáros, P; Wang, Xiang-Yu; Li, Zhuo; Meszaros, Peter

    2007-01-01

    The recent detection of X-ray flares during the afterglow phase of gamma-ray bursts (GRBs) suggests an inner-engine origin, at radii inside the forward shock. There must be inverse Compton (IC) emission arising from such flare photons scattered by forward shock afterglow electrons when they are passing through the forward shock. We find that this IC emission produces high energy gamma-ray flares, which may be detected by AGILE, GLAST and ground-based TeV telescopes. The anisotropic IC scattering between flare photons and forward shock electrons does not affect the total IC component intensity, but cause a time delay of the IC component peak relative to the flare peak. The anisotropic scattering effect may also weaken, to some extent, the suppression effect of the afterglow intensity induced by the enhanced electron cooling due to flare photons. We speculate that this IC component may already have been detected by EGRET from a very strong burst--GRB940217. Future observations by GLAST may help to distinguish w...

  12. Neutron Stars and Thermonuclear X-ray Bursts

    Science.gov (United States)

    Bhattacharyya, Sudip

    2007-01-01

    Studies of thermonuclear X-ray bursts can be very useful to constrain the spin rate, mass and radius of a neutron star approaching EOS model of high density cold matter in the neutron star cores. +k Extensive observation and analysis of the data from the rising portions of the bursts - modeling of burst oscillations and thermonuclear flame spreading. +k Theoretical study of thermonuclear flame spreading on the rapidly spinning neutron stars should be done considering all the main physical effects (including magnetic field, nuclear energy generation, Coriolis effect, strong gravity, etc.).

  13. Understanding Neutron Stars using Thermonuclear X-ray Bursts

    Science.gov (United States)

    Bhattacharyya, S.

    2007-01-01

    Studies of thermonuclear X-ray bursts can be very useful to constrain the spin rate, mass and radius of a neutron star = EOS model of high density cold matter in the neutron star cores. Extensive observation and analysis of the data from the rising portions of the bursts = modeling of burst oscillations and thermonuclear flame spreading. Theoretical study of thermonuclear flame spreading on the rapidly spinning neutron stars should be done considering all the main physical effects (including magnetic field, nuclear energy generation, Coriolis effect, strong gravity, etc.).

  14. Positions and sizes of X-ray solar flare sources

    CERN Document Server

    Kontar, E P

    2010-01-01

    We investigate the positions and source sizes of X-ray solar flare sources taking into account Compton backscattering (albedo). Using a Monte Carlo simulation of X-ray photon transport including photo-electric absorption and Compton scattering, we calculate the apparent source sizes and positions of X-ray sources at the solar disk for various source sizes, spectral indices and directivities of the primary source. We show that the albedo effect will alter the true source positions and substantially increase the measured source sizes. The source positions are shifted up to $\\sim 0.5"$ radially towards the disk centre and 5 arcsecond source sizes can be two times larger even for an isotropic source (minimum albedo effect) at 1 Mm above the photosphere. X-ray sources therefore should have minimum observed sizes, thus FWHM source size (2.35 times second-moment) will be as large as $\\sim 7"$ in the 20-50 keV range for a disk-centered point source at a height of 1 Mm ($\\sim 1.4"$) above the photosphere. The source s...

  15. Ejection Lorentz Factor and Radiation Location of X-ray Flares

    CERN Document Server

    Mu, Hui-Jun; Xi, Shao-Qiang; Lin, Ting-Ting; Wang, Yuan-Zhu; Liang, Yun-Feng; Lv, Lian-Zhong; Zhang, Jin; Liang, En-Wei

    2016-01-01

    We present time-resolved spectral analysis of the steep decay segments of 29 bright X-ray flares of gamma-ray bursts (GRBs) observed with the Swift/X-ray telescope, and model their lightcurves and spectral index evolution behaviors with the curvature effect model. Our results show that the observed rapid flux decay and strong spectral index evolution with time can be well fit with this model, and the derived characteristic timescales ($t_c$) are in the range of $33\\sim 264$ seconds. Using an empirical relation between the peak luminosity and the Lorentz factor derived from the prompt gamma-rays, we estimate the Lorentz factors of the flares ($\\Gamma_{\\rm X}$). We obtain $\\Gamma_{\\rm X}=17\\sim 87$ with a median value of $52$, which is smaller than the initial Lorentz factors of prompt gamma-ray fireballs. With the derived $t_c$ and $\\Gamma_{\\rm X}$, we constrain the radiating regions of 13 X-ray flares, yielding $R_{\\rm X}=(0.2\\sim 1.1)\\times 10^{16}$ cm, which are smaller than the radii of the afterglow fireb...

  16. Maxi observations of long X-ray bursts

    CERN Document Server

    Serino, Motoko; Tamagawa, Toru; Sakamoto, Takanori; Nakahira, Satoshi; Matsuoka, Masaru; Yamaoka, Kazutaka; Negoro, Hitoshi

    2016-01-01

    We report nine long X-ray bursts from neutron stars, detected with Monitor of All-sky X-ray Image (MAXI). Some of these bursts lasted for hours, and hence are qualified as superbursts, which are prolonged thermonuclear flashes on neutron stars and are relatively rare events. MAXI observes roughly 85% of the whole sky every 92 minutes in the 2-20 keV energy band, and has detected nine bursts with a long e-folding decay time, ranging from 0.27 to 5.2 hours, since its launch in 2009 August until 2015 August. The majority of the nine events were found to originate from transient X-ray sources. The persistent luminosities of the sources, when these prolonged bursts were observed, were lower than 1% of the Eddington luminosity for five of them and lower than 20% for the rest. This trend is contrastive to the 18 superbursts observed before MAXI, all but two of which originated from bright persistent sources. The distribution of the total emitted energy, i.e., the product of e-folding time and luminosity, of these bu...

  17. Studies of soft x-ray emission during solar flares

    International Nuclear Information System (INIS)

    Solar flare soft x-ray emission from 0.5 A to 8.5 A was observed during 1967-68 by Bragg crystal (LiF and EDDT) spectrometers aboard the OSO-4 satellite and also by NRL broad-band ionization detectors aboard the OGO-4 satellite. In this work, instrumental parameters for the LiF crystal spectrometer based on experimental values have been determined and used in the data analysis. The total continuum emission in the 0.5 to 3 A and the 1 to 8 A broad band segments has been determined from OGO-4 data for 21 flares. In doing this, a simple and approximate method of converting the total emission based on the gray body approximation (in which the OGO-4 data are reported) to one based on the thermal continuum spectrum has been developed. (author)

  18. Two Solar Flares that Became X-ray Plasma Ejections

    Science.gov (United States)

    Tomczak, M.

    Solar flares and X-ray plasma ejections (XPEs) occur simultaneously but usually are separated spatially. We present two exceptional events observed by Yohkoh in 2001 October 2 (event 1) and 2000 October 16 (event 2), in which features of flares and XPEs are mixed. Namely, the soft and hard X-ray images show intense sources of emission that move dynamically. Both events occurred inside broad active regions showing complicated multi-level structure reaching up to 200 Mm high. Both events show also similar four-stages evolution: (1) a fast rise of a system of loops, (2) sudden changes in their emission distribution, (3) a reconfiguration leading to liberation of large amounts of plasma, (4) a small, static loop as the final remnant. Nevertheless, the events are probably caused by different physical processes: emerging magnetic flux plus reconnection (event 1) and reconnection plus ballooning instability (event 2). Different is also the final destination of the ejected plasma: in the event 1 overlying magnetic fields stop the ejection, in the event 2 the ejection destabilizes the overall magnetic structure and forms a coronal mass ejection (CME).

  19. Using the Maximum X-ray Flux Ratio and X-ray Background to Predict Solar Flare Class

    OpenAIRE

    Winter, Lisa M.; Balasubramaniam, K.

    2015-01-01

    We present the discovery of a relationship between the maximum ratio of the flare flux (namely, 0.5-4 Ang to the 1-8 Ang flux) and non-flare background (namely, the 1-8 Ang background flux), which clearly separates flares into classes by peak flux level. We established this relationship based on an analysis of the Geostationary Operational Environmental Satellites (GOES) X-ray observations of ~ 50,000 X, M, C, and B flares derived from the NOAA/SWPC flares catalog. Employing a combination of ...

  20. Millisecond Oscillations During Thermonuclear X-ray Bursts

    CERN Document Server

    Muno, M P

    2004-01-01

    I review the basic phenomenology and theory of the millisecond brightness oscillations observed during thermonuclear X-ray bursts from 13 of approximately 70 accreting neutron stars in low-mass X-ray binaries. Compelling observations indicate that the oscillations are produced by surface brightness patterns on the rapidly rotating neutron stars. However, it remains to be understood (1) why the brightness patterns producing them persist for up to 15 s during an X-ray burst, whereas the burning should cover the entire surface in less than 1 s, and (2) why the frequencies drift upward by about 5 Hz during the course of the burst. These peculiarities can probably be explained by taking into account the expansion of the surface layers caused by the burning, zonal flows that form due to pressure gradients between the equator and poles, and Rossby-Alfven modes that are excited in the surface ocean. Further progress toward understanding how burning progresses on the surface of the neutron star can be made with a next...

  1. Detection of burning ashes from thermonuclear X-ray bursts

    CERN Document Server

    Kajava, J J E; Poutanen, J; Cumming, A; Suleimanov, V; Kuulkers, E

    2016-01-01

    When neutron stars (NS) accrete gas from low-mass binary companions, explosive nuclear burning reactions in the NS envelope fuse hydrogen and helium into heavier elements. The resulting thermonuclear (type-I) X-ray bursts produce energy spectra that are fit well with black bodies, but a significant number of burst observations show deviations from Planck spectra. Here we present our analysis of RXTE/PCA observations of X-ray bursts from the NS low-mass X-ray binary HETE J1900.1-2455. We have discovered that the non-Planckian spectra are caused by photo-ionization edges. The anti-correlation between the strength of the edges and the colour temperature suggests that the edges are produced by the nuclear burning ashes that have been transported upwards by convection and become exposed at the photosphere. The atmosphere model fits show that occasionally the photosphere can consist entirely of metals, and that the peculiar changes in black body temperature and radius can be attributed to the emergence and disappea...

  2. Timing analysis of hard X-ray emission and 22 GHz flux and polarization in a solar burst

    International Nuclear Information System (INIS)

    A solar flare occurring on 26 February 1981 at 1932 UT was observed simultaneously, in hard X-rays and microwaves with a time resolution of a fraction of a second. The X-ray observations were made with the Hard X-ray Monitor on Hinotori, and the microwave observations were made at 22 GHz with the 13.7 m Itapetinga mm-wave antenna. Timing accuracy was restricted to 62.5 ms, the best time resolution obtained in hard X-rays for this burst. It is found that: (a) all 22 GHz flux structures were delayed by 0.2 - 0.9 second relative to similar structures in hard X-rays throughout the burst duration; (b) different burst structures showed different delays, suggesting that they are independent of each other; (c) the time structures of the degree of polarization at 22 GHz precede the total microwave flux time structures by 0.1-0.5 sec; (d) The time evolutions of time delays of microwaves with respect to hard X-rays and also the degree of microwave polarization show fluctuations with are not clearly related to any other time structures. If it is taken mean values for the 32 sec burst duration, it is found that hard X-ray emission precedes the degree of microwave polarization by 450 ms, which in turn precedes the total microwave flux by 110 ms. (Author)

  3. Hard X-ray bremsstrahlung production in solar flares by high-energy proton beams

    Science.gov (United States)

    Emslie, A. G.; Brown, J. C.

    1985-01-01

    The possibility that solar hard X-ray bremsstrahlung is produced by acceleration of stationary electrons by fast-moving protons, rather than vice versa, as commonly assumed, was investigated. It was found that a beam of protons which involves 1836 times fewer particles, each having an energy 1836 times greater than that of the electrons in the equivalent electron beam model, has exactly the same bremsstrahlung yield for a given target, i.e., the mechanism has an energetic efficiency equal to that of conventional bremsstrahlung models. Allowance for the different degrees of target ionization appropriate to the two models (for conventional flare geometries) makes the proton beam model more efficient than the electron beam model, by a factor of order three. The model places less stringent constraints than a conventional electron beam model on the flare energy release mechanism. It is also consistent with observed X-ray burst spectra, intensities, and directivities. The altitude distribution of hard X-rays predicted by the model agrees with observations only if nonvertical injection of the protons is assumed. The model is inconsistent with gamma-ray data in terms of conventional modeling.

  4. AN INVERSE COMPTON SCATTERING ORIGIN OF X-RAY FLARES FROM Sgr A*

    Energy Technology Data Exchange (ETDEWEB)

    Yusef-Zadeh, F. [Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208 (United States); Wardle, M. [Department of Physics and Astronomy, Macquarie University, Sydney NSW 2109 (Australia); Dodds-Eden, K.; Gillessen, S.; Genzel, R. [Max Planck Institut fuer Extraterrestrische Physik, Postfach 1312, D-85741 Garching (Germany); Heinke, C. O. [Department of Physics, University of Alberta, 4-183 CCIS, Edmonton, AB T6G 2E1 (Canada); Bushouse, H. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Grosso, N.; Porquet, D. [Observatoire astronomique de Strasbourg, Universite de Strasbourg, CNRS, INSU, 11 rue de l' Universite, 67000 Strasbourg (France)

    2012-07-15

    The X-ray and near-IR emission from Sgr A* is dominated by flaring, while a quiescent component dominates the emission at radio and submillimeter (sub-mm) wavelengths. The spectral energy distribution of the quiescent emission from Sgr A* peaks at sub-mm wavelengths and is modeled as synchrotron radiation from a thermal population of electrons in the accretion flow, with electron temperatures ranging up to {approx}5-20 MeV. Here, we investigate the mechanism by which X-ray flare emission is produced through the interaction of the quiescent and flaring components of Sgr A*. The X-ray flare emission has been interpreted as inverse Compton, self-synchrotron Compton, or synchrotron emission. We present results of simultaneous X-ray and near-IR observations and show evidence that X-ray peak flare emission lags behind near-IR flare emission with a time delay ranging from a few to tens of minutes. Our inverse Compton scattering modeling places constraints on the electron density and temperature distributions of the accretion flow and on the locations where flares are produced. In the context of this model, the strong X-ray counterparts to near-IR flares arising from the inner disk should show no significant time delay, whereas near-IR flares in the outer disk should show a broadened and delayed X-ray flare.

  5. AN INVERSE COMPTON SCATTERING ORIGIN OF X-RAY FLARES FROM Sgr A*

    International Nuclear Information System (INIS)

    The X-ray and near-IR emission from Sgr A* is dominated by flaring, while a quiescent component dominates the emission at radio and submillimeter (sub-mm) wavelengths. The spectral energy distribution of the quiescent emission from Sgr A* peaks at sub-mm wavelengths and is modeled as synchrotron radiation from a thermal population of electrons in the accretion flow, with electron temperatures ranging up to ∼5-20 MeV. Here, we investigate the mechanism by which X-ray flare emission is produced through the interaction of the quiescent and flaring components of Sgr A*. The X-ray flare emission has been interpreted as inverse Compton, self-synchrotron Compton, or synchrotron emission. We present results of simultaneous X-ray and near-IR observations and show evidence that X-ray peak flare emission lags behind near-IR flare emission with a time delay ranging from a few to tens of minutes. Our inverse Compton scattering modeling places constraints on the electron density and temperature distributions of the accretion flow and on the locations where flares are produced. In the context of this model, the strong X-ray counterparts to near-IR flares arising from the inner disk should show no significant time delay, whereas near-IR flares in the outer disk should show a broadened and delayed X-ray flare.

  6. Bright Flares in Supergiant Fast X-ray Transients

    CERN Document Server

    Shakura, N; Sidoli, L; Paizis, A

    2014-01-01

    At steady low-luminosity states, Supergiant Fast X-ray Transients (SFXTs) can be at the stage of quasi-spherical settling accretion onto slowly rotating magnetized NS from the OB-companion winds. At this stage, a hot quasi-static shell is formed above the magnetosphere, the plasma entry rate into magnetosphere is controlled by (inefficient) radiative plasma cooling, and the accretion rate onto the NS is suppressed by a factor of \\sim 30 relative to the Bondi-Hoyle-Littleton value. Changes in the local wind velocity and density can only slightly increase the mass accretion rate (a factor of \\sim 10) bringing the system into the Compton cooling dominated regime and led to the production of moderately bright flares (L_x\\lesssim 10^{36} erg/s). To interpret the brightest flares (L_x>10^{36}~erg/s) displayed by the SFXTs, we propose that a larger increase in the mass accretion rate can be produced by sporadic capture of magnetized stellar wind plasma. At sufficiently low accretion rates, magnetic reconnection can ...

  7. DETECTION OF HIGH-ENERGY GAMMA-RAY EMISSION DURING THE X-RAY FLARING ACTIVITY IN GRB 100728A

    International Nuclear Information System (INIS)

    We present the simultaneous Swift and Fermi observations of the bright GRB 100728A and its afterglow. The early X-ray emission is dominated by a vigorous flaring activity continuing until 1 ks after the burst. In the same time interval, high-energy emission is significantly detected by the Fermi/Large Area Telescope. Marginal evidence of GeV emission is observed up to later times. We discuss the broadband properties of this burst within both the internal and external shock scenarios, with a particular emphasis on the relation between X-ray flares, the GeV emission, and a continued long-duration central engine activity as their power source.

  8. Using the Maximum X-ray Flux Ratio and X-ray Background to Predict Solar Flare Class

    CERN Document Server

    Winter, Lisa M

    2015-01-01

    We present the discovery of a relationship between the maximum ratio of the flare flux (namely, 0.5-4 Ang to the 1-8 Ang flux) and non-flare background (namely, the 1-8 Ang background flux), which clearly separates flares into classes by peak flux level. We established this relationship based on an analysis of the Geostationary Operational Environmental Satellites (GOES) X-ray observations of ~ 50,000 X, M, C, and B flares derived from the NOAA/SWPC flares catalog. Employing a combination of machine learning techniques (K-nearest neighbors and nearest-centroid algorithms) we show a separation of the observed parameters for the different peak flaring energies. This analysis is validated by successfully predicting the flare classes for 100% of the X-class flares, 76% of the M-class flares, 80% of the C-class flares and 81% of the B-class flares for solar cycle 24, based on the training of the parametric extracts for solar flares in cycles 22-23.

  9. Correlation of hard X-ray and white light emission in solar flares

    OpenAIRE

    Kuhar, Matej; Krucker, Säm; Oliveros, Juan Carlos Martínez; Battaglia, Marina; Kleint, Lucia; Casadei, Diego; Hudson, Hugh S.

    2015-01-01

    A statistical study of the correlation between hard X-ray and white light emission in solar flares is performed in order to search for a link between flare-accelerated electrons and white light formation. We analyze 43 flares spanning GOES classes M and X using observations from RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager) and HMI (Helioseismic and Magnetic Imager). We calculate X-ray fluxes at 30 keV and white light fluxes at 6173 \\r{A} summed over the hard X-ray flare ribbo...

  10. Large X-ray Flares on Stars Detected with MAXI/GSC: A Universal Correlation between the Duration of a Flare and its X-ray Luminosity

    CERN Document Server

    Tsuboi, Yohko; Sugawara, Yasuharu; Kawagoe, Atsushi; Kaneto, Soichiro; Iizuka, Ryo; Matsumura, Takanori; Nakahira, Satoshi; Higa, Masaya; Matsuoka, Masaru; Sugizaki, Mutsumi; Ueda, Yoshihiro; Kawai, Nobuyuki; Morii, Mikio; Serino, Motoko; Mihara, Tatehiro; Tomida, Hiroshi; Ueno, Shiro; Negoro, Hitoshi; Daikyuji, Arata; Ebisawa, Ken; Eguchi, Satoshi; Hiroi, Kazuo; Ishikawa, Masaki; Isobe, Naoki; Kawasaki, Kazuyoshi; Kimura, Masashi; Kitayama, Hiroki; Kohama, Mitsuhiro; Kotani, Taro; Nakagawa, Yujin E; Nakajima, Motoki; Ozawa, Hiroshi; Shidatsu, Megumi; Sootome, Tetsuya; Sugimori, Kousuke; Suwa, Fumitoshi; Tsunemi, Hiroshi; Usui, Ryuichi; Yamamoto, Takayuki; Yamaoka, Kazutaka; Yoshida, Atsumasa

    2016-01-01

    23 giant flares from 13 active stars (eight RS CVn systems, one Algol system, three dMe stars and one YSO) were detected during the first two years of our all-sky X-ray monitoring with the gas propotional counters (GSC) of the Monitor of All-sky X-ray Image (MAXI). The observed parameters of all of these MAXI/GSC flares are found to be at the upper ends for stellar flares with the luminosity of 10^(31-34) ergs s-1 in the 2-20 keV band, the emission measure of 10^(54-57) cm-3, the e-folding time of 1 hour to 1.5 days, and the total radiative energy released during the flare of 10^(34-39) ergs. Notably, the peak X-ray luminosity of 5(3-9)*10^33 ergs s-1 in the 2-20 keV band was detected in one of the flares on II Peg, which is one of the, or potentially the, largest ever observed in stellar flares. X-ray flares were detected from GT Mus, V841 Cen, SZ Psc, and TWA-7 for the first time in this survey. Whereas most of our detected sources are multiple-star systems, two of them are single stars (YZ CMi and TWA-7). ...

  11. Correlated optical and X-ray flares in the afterglow of XRF 071031

    CERN Document Server

    Krühler, T; McBreen, S; Klose, S; Rossi, A; Afonso, P; Clemens, C; Filgas, R; Yoldas, A Küpcü; Szokoly, G P; Yoldas, A

    2009-01-01

    We present a densely sampled early light curve of the optical/near-infrared (NIR) afterglow of the X-Ray Flash (XRF) 071031 at z=2.692. Simultaneous and continuous observations in seven photometric bands from g' to K with GROND at the 2.2 m MPI/ESO telescope on LaSilla were performed between 4 minutes and 7 hours after the burst. The light curve consists of 547 individual points which allows us to study the early evolution of the optical transient associated with XRF 071031 in great detail. The optical/NIR light curve is dominated by an early increase in brightness which can be attributed to the apparent onset of the forward shock emission. There are several bumps which are superimposed onto the overall rise and decay. Significant flaring is also visible in the Swift X-Ray Telescope (XRT) light curve from early to late times. The availability of high quality, broadband data enables detailed studies of the connection between the X-ray and optical/NIR afterglow and its colour evolution during the first night po...

  12. Fermi Detection of \\gamma-ray emission from the M2 Soft X-ray Flare on 2010 June 12

    OpenAIRE

    Fermi GBM Collaboration; Fermi LAT collaboration; Dennis, B. R.; Schwartz, R. A.; Tolbert, A. K.

    2011-01-01

    The GOES M2-class solar flare, SOL2010-06-12T00:57, was modest in many respects yet exhibited remarkable acceleration of energetic particles. The flare produced an ~50 s impulsive burst of hard X- and \\gamma-ray emission up to at least 400 MeV observed by the Fermi GBM and LAT experiments. The remarkably similar hard X-ray and high-energy \\gamma-ray time profiles suggest that most of the particles were accelerated to energies >300 MeV with a delay of ~10 s from mildly relativistic electrons, ...

  13. Temporal aspects and frequency distributions of solar soft X-ray flares

    OpenAIRE

    Veronig, A.; Temmer, M.; Hanslmeier, A.; Otruba, W.; Messerotti, M.

    2002-01-01

    A statistical analysis of almost 50000 soft X-ray (SXR) flares observed by GOES during the period 1976-2000 is presented. On the basis of this extensive data set, statistics on temporal properties of soft X-ray flares, such as duration, rise and decay times with regard to the SXR flare classes is presented. Correlations among distinct flare parameters, i.e. SXR peak flux, fluence and characteristic times, and frequency distributions of flare occurrence as function of the peak flux, the fluenc...

  14. The Rapid Burster and its X-ray bursts: extremes of accretion and thermonuclear burning

    OpenAIRE

    Klis, van der, M.; Zand, in 't, J.J.M.; Watts, A.; Bagnoli, T.

    2015-01-01

    X-ray bursts originate from accreting neutron stars (NSs) in X-ray binaries (XRBs). They come in two flavours: thermonuclear bursts are due to the sudden runaway burning of the material accreted on the surface; accretion bursts signal a sudden change in the mass accretion rate, leading to enhanced emission in the innermost regions of the accretion flow. While thermonuclear bursts have been observed from 105 NSs as of writing, accretion bursts remain enigmatically confined to only two sources....

  15. The Search for Type 1 X-ray Bursts with Fermi/GBM

    Science.gov (United States)

    Jenke, Peter; Linares, M.; Connaughton, V.; Camero-Arranz, A.; Finger, M. H.; WIlson-Hodge, C. A.; Van Der Horst, A.; Fermi GBM X-ray Burst Collaboration

    2012-01-01

    We discuss the first results of the Fermi-GBM all-sky search for X-ray bursts. The very large field of view and X-ray response of the Fermi-GBM make it a unique instrument to study rare, bright and short-lived X-ray bursts. We are performing a systematic search that exploits such capabilities. We present results on long/intermediate type I X-ray bursts, an unusual kind of thermonuclear bursts from accreting neutron stars, and show how Fermi-GBM is giving, for the first time, robust measurements of their recurrence time.

  16. Spectral evolution of microwaves and hard X-rays in the 1989 March 18 flare and its interpretation

    Science.gov (United States)

    Lee, Jeongwoo W.; Gary, Dale E.

    1994-01-01

    We analyze the time variation of microwave spectra and hard X-ray spectra of 1989 March 18, which are obtained from the Solar Array at the Owens Valley Radio Observatory (OVRO) and the Hard X-Ray Burst Spectrometer (HXRBS) on the Solar Maximum Mission (SMM), respectively. From this observation, it is noted that the hard X-ray spectra gradually soften over 50 - 200 keV on-and-after the maximum phase while the microwaves at 1 - 15 GHz show neither a change in spectral shape nor as rapid a decay as hard X-rays. This leads to decoupling of hard X-rays from the microwaves in the decay phase away from their good correlation seen in the initial rise phase. To interpret this observation, we adopt a view that microwave-emitting particles and hard X-ray particles are physically separated in an inhomogeneous magnetic loop, but linked via interactions with the Whistler waves generated during flares. From this viewpoint, it is argued that the observed decoupling of microwaves from hard X-rays may be due to the different ability of each source region to maintain high energy electrons in response to the Whistler waves passing through the entire loop. To demonstrate this possibility, we solve a Fokker-Planck equation that describes evolution of electrons interacting with the Whistler waves, taking into account the variation of Fokker-Planck coefficients with physical quantities of the background medium. The numerical Fokker-Planck solutions are then used to calculate microwave spectra and hard X-ray spectra for agreement with observations. Our model results are as follows: in a sronger field region, the energy loss by electron escape due to scattering by the waves is greatly enhanced resulting in steep particle distributions that reproduce the observed hard X-ray spectra. In a region with weaker fields and lower density, this loss term is reduced allowing high energy electrons to survive longer so that microwaves can be emitted there in excess of hard X-rays during the decay phase

  17. Multiscale self-organized criticality and powerful X-ray flares

    OpenAIRE

    Bershadskii, A.; Sreenivasan, K. R.

    2003-01-01

    A combination of spectral and moments analysis of the continuous X-ray flux data is used to show consistency of statistical properties of the powerful solar flares with 2D BTW prototype model of self-organized criticality.

  18. Dependence of X-Ray Burst Models on Nuclear Reaction Rates

    OpenAIRE

    Cyburt, R. H.; Amthor, A. M.; Heger, A.; Johnson, E.; Keek, L.; Meisel, Z.; Schatz, H.; Smith, K

    2016-01-01

    X-ray bursts are thermonuclear flashes on the surface of accreting neutron stars and reliable burst models are needed to interpret observations in terms of properties of the neutron star and the binary system. We investigate the dependence of X-ray burst models on uncertainties in (p,$\\gamma$), ($\\alpha$,$\\gamma$), and ($\\alpha$,p) nuclear reaction rates using fully self-consistent burst models that account for the feedbacks between changes in nuclear energy generation and changes in astrophy...

  19. Delayed X-Ray Afterglows from Obscured Gamma-Ray Bursts in Star-Forming Regions

    OpenAIRE

    Meszaros, P.; Gruzinov, A.

    2000-01-01

    For Gamma-Ray Bursts occurring in dense star-forming regions, the X-ray afterglow behavior minutes to days after the trigger may be dominated by the small-angle scattering of the prompt X-ray emission off dust grains. We give a simple illustrative model for the X-ray light curves at different X-ray energies, and discuss possible implications. A bump followed by a steeper decay in soft X-rays is predicted for bursts which are heavily obscured in the optical.

  20. THE HARD X-RAY BEHAVIOR OF AQL X-1 DURING TYPE-I BURSTS

    International Nuclear Information System (INIS)

    We report the discovery of an anti-correlation between the soft and hard X-ray light curves of the X-ray binary Aql X-1 when bursting. This behavior may indicate that the corona is cooled by the soft X-ray shower fed by the type-I X-ray bursts, and that this process happens within a few seconds. Stacking the Aql X-1 light curves of type-I bursts, we find a shortage in the 40-50 keV band, delayed by 4.5 ± 1.4 s with respect to the soft X-rays. The photospheric radius expansion bursts are different in that neither a shortage nor an excess shows up in the hard X-ray light curve

  1. Early Abnormal Temperature Structure of X-ray Looptop Source of Solar Flares

    OpenAIRE

    Shen, Jinhua; Zhou, Tuanhui; Ji, Haisheng; Na WANG; Cao, Wenda; Wang, Haimin

    2008-01-01

    This Letter is to investigate the physics of a newly discovered phenomenon -- contracting flare loops in the early phase of solar flares. In classical flare models, which were constructed based on the phenomenon of expansion of flare loops, an energy releasing site is put above flare loops. These models can predict that there is a vertical temperature gradient in the top of flare loops due to heat conduction and cooling effects. Therefore, the centroid of an X-ray looptop source at higher ene...

  2. Two-phase X-ray burst from GX 3+1 observed by INTEGRAL

    NARCIS (Netherlands)

    Chenevez, J.; Falanga, M.; Brandt, S.; Farinelli, R.; Frontera, F.; Goldwurm, A.; in 't Zand, J.J.M.; Kuulkers, E.; Lund, N.

    2006-01-01

    INTEGRAL detected on August 31, 2004, an unusual thermonuclear X-ray burst from the low-mass X-ray binary GX 3+1. Its duration was 30 min, which is between the normal burst durations for this source (

  3. Thermonuclear X-ray bursts from IGR J17473-2721

    DEFF Research Database (Denmark)

    The X-ray transient source IGR J17473-2721 exhibited a renewed episode of activity between March and September 2008, which was shortly preceded by a thermonuclear X-ray burst. Interpretation of the source bursting behaviour will be presented from observation results obtained by four satellites....

  4. The eclipsing bursting X-ray binary EXO 0748-676 revisited by XMM-Newton

    CERN Document Server

    Bonnet-Bidaud, J M; Ferrando, P; Bennie, P J; Kendziorra, E

    2001-01-01

    The bright eclipsing and bursting low-mass X-ray binary EXO 0748-676 has been observed at several occasions by XMM-Newton during the initial calibration and performance verification (CAL/PV) phase. We present here the results obtained from observations with the EPIC cameras. Apart from several type-I X-ray bursts, the source shows a high degree of variability with the presence of soft flares. The wide energy coverage and high sensitivity of XMM-Newton allows for the first time a detailed description of the spectral variability. The source is found to be the superposition of a central (~2 10^8 cm) Comptonized emission, most probably a corona surrounding the inner edge of an accretion disk, associated with a more extended (~3 10^10 cm) thermal halo at a typical temperature of ~0.6 keV with an indication of non-solar abundances. Most of the variations of the source can be accounted for by a variable absorption affecting only the central comptonized component and reaching up to NH ~1.3 10^23 cm^{-2}. The characte...

  5. Interpreting Sgr A*'s Most Luminous X-ray Flares

    Science.gov (United States)

    Haggard, Daryl; Baganoff, Frederick K.; Capellupo, Daniel M.; Neilsen, Joseph; Nowak, Michael; Markoff, Sera; Ponti, Gabriele; Degenaar, Nathalie; Heinke, Craig O.; Yusef-Zadeh, Farhad

    2016-04-01

    During ambitious X-ray and radio monitoring campaigns with Chandra, XMM, Swift, and the VLA, we have detected the brightest-ever X-ray flares from Sgr A*. These flares likely probe the physical processes and accretion flow near the black hole's event horizon. Yet, despite years of observational and theoretical study, we do not have a complete, unique model to explain these high-energy flares, or their relationship to variability at other wavelengths. Viable models range from the tidal disruption of asteroids to collimated outflows to magnetic reconnection, motivating observers to place tighter constraints on the timing and multiwavelength properties of these outbursts. X-ray flares may also help us relate Sgr A* to weakly accreting black holes across the mass spectrum. I will discuss the possible origins and continuing mysteries surrounding Sgr A*'s high-energy flares and give a brief update on the Sgr A*/G2 interaction.

  6. SGR 1806-20 distance and dust properties in molecular clouds by analysis of a flare x-ray echoes

    CERN Document Server

    Svirski, Gilad; Ofek, Eran O

    2011-01-01

    The soft gamma repeater SGR 1806-20 is most famous for its giant flare from 2004, which yielded the highest gamma-ray flux ever observed on Earth. The flare emphasized the importance of determining the distance to the SGR, thus revealing the flare's energy output, with implications on SGRs energy budget and giant flare rates. We analyze x-ray scattering echoes observed by Swift/XRT following the 2006 August 6 intermediate burst of SGR 1806-20. Assuming positions and opacities of the molecular clouds along the line-of-sight from previous works, we derive direct constrains on the distance to SGR 1806-20, setting a lower limit of 9.4 kpc and an upper limit of 18.6 kpc (90% confidence), compared with a 6-15 kpc distance range by previous works. This distance range matches an energy output of ~10^46 erg/s for the 2004 giant flare. We further use, for the first time, the x-ray echoes in order to study the dust properties in molecular clouds. Analyzing the temporal evolution of the observed flux using a dust scatter...

  7. Fermi Detection of Gamma-Ray Emission from the M2 Soft X-Ray Flare on 2010 June 12

    Science.gov (United States)

    Ackermann, M.; Ajello, M.; Allafort, A.; Atwood, W. B.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bhat, P. N.; Blandford, R. D.; Bonamente, E.; Borgland, A. W.; Bregeon, J.; Briggs, M. S.; Brigida, M.; Bruel, P.; Buehler, R.; Burgess, J. M.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Gruber, D.; Troja, E.; Casandjian, J. M.

    2012-01-01

    The GOES M2-class solar flare, SOL2010-06-12T00:57, was modest in many respects yet exhibited remarkable acceleration of energetic particles. The flare produced an approximately 50 s impulsive burst of hard X- and gamma-ray emission up to at least 400 MeV observed by the Fermi GBM and LAT experiments. The remarkably similar hard X-ray and high-energy gamma-ray time profiles suggest that most of the particles were accelerated to energies greater than or equal to 300 MeV with a delay of approximately 10 s from mildly relativistic electrons, but some reached these energies in as little as approximately 3 s. The gamma-ray line fluence from this flare was about ten times higher than that typically observed from this modest GOES class of X-ray flare. There is no evidence for time-extended greater than 100 MeV emission as has been found for other flares with high-energy gamma rays.

  8. Implications of X-Ray Observations for Electron Acceleration and Propagation in Solar Flares

    Science.gov (United States)

    Holman, G. D.; Aschwanden, M. J.; Aurass, H.; Battaglia, M.; Grigis, P. C.; Kontar, E. P.; Liu, W.; Saint-Hilaire, P.; Zharkova, V. V.

    2011-01-01

    High-energy X-rays and gamma-rays from solar flares were discovered just over fifty years ago. Since that time, the standard for the interpretation of spatially integrated flare X-ray spectra at energies above several tens of keV has been the collisional thick-target model. After the launch of the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) in early 2002, X-ray spectra and images have been of sufficient quality to allow a greater focus on the energetic electrons responsible for the X-ray emission, including their origin and their interactions with the flare plasma and magnetic field. The result has been new insights into the flaring process, as well as more quantitative models for both electron acceleration and propagation, and for the flare environment with which the electrons interact. In this article we review our current understanding of electron acceleration, energy loss, and propagation in flares. Implications of these new results for the collisional thick-target model, for general flare models, and for future flare studies are discussed.

  9. 30S RI Beam Production and X-ray Bursts

    CERN Document Server

    Kahl, David; Binh, Dam Nguyen; Chen, Jun; Hashimoto, Takashi; Hayakawa, Seiya; Kim, Aram; Kubono, Shigeru; Kurihara, Yuzo; Lee, Nam Hee; Michimasa, Shin'ichiro; Nishimura, Shunji; Van Ouellet, Christian; nia, Kiana Setoodeh; Wakabayashi, Yasuo; Yamaguchi, Hideotoshi

    2009-01-01

    The present work reports the results of 30S radioactive beam development for a future experiment directly measuring data to extrapolate the 30S(alpha,p) stellar reaction rate in Type I X-ray bursts, a phenomena where nuclear explosions occur repeatedly on the surface of accreting neutron stars. We produce the radioactive ion 30S via the 3He(28Si,30S)n reaction, by bombarding a cryogenically cooled target of 3He at 400 Torr and 80 K with 28Si beams of 6.9 and 7.54 MeV/u. In order to perform a successful future experiment which allows us to calculate the stellar 30S(alpha, p) reaction rate, Hauser-Feshbach calculations indicate we require a 30S beam of ~10^5 particles per second at ~32 MeV. Based on our recent beam development experiments in 2006 and 2008, it is believed that such a beam may be fabricated in 2009 according to the results presented. We plan to measure the 4He(30S,p) cross-section at astrophysical energies in 2009, and some brief remarks on the planned (alpha,p) technique are also elucidated.

  10. Solar flares with similar soft but different hard X-ray emissions: case and statistical studies

    Science.gov (United States)

    Sharykin, Ivan N.; Struminsky, Alexei B.; Zimovets, Ivan V.; Gan, Wei-Qun

    2016-01-01

    From the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) catalog we select events which have approximately the same GOES class (high C - low M or 500-1200 counts s-1 within the RHESSI 6-12 keV energy band), but with different maximal energies of detected hard X-rays. The selected events are subdivided into two groups: (1) flares with X-ray emissions observed by RHESSI up to only 50 keV and (2) flares with hard X-ray emission observed also above 50 keV. The main task is to understand observational peculiarities of these two flare groups. We use RHESSI X-ray data to obtain spectral and spatial information in order to find differences between selected groups. Spectra and images are analyzed in detail for six events (case study). For a larger number of samples (85 and 28 flares in the low-energy and high-energy groups respectively) we only make some generalizations. In spectral analysis we use the thick-target model for hard X-ray emission and one temperature assumption for thermal soft X-ray emission. RHESSI X-ray images are used for determination of flare region sizes. Although thermal and spatial properties of these two groups of flares are not easily distinguishable, power law indices of hard X-rays show significant differences. Events from the high-energy group generally have a harder spectrum. Therefore, the efficiency of chromospheric evaporation is not sensitive to the hardness of nonthermal electron spectra but rather depends on the total energy flux of nonthermal electrons.

  11. A Systematic Chandra study of Sgr A$^{\\star}$: I. X-ray flare detection

    OpenAIRE

    Yuan, Qiang; Wang, Q. Daniel

    2015-01-01

    Daily X-ray flaring represents an enigmatic phenomenon of Sgr A$^{\\star}$ --- the supermassive black hole at the center of our Galaxy. We report initial results from a systematic X-ray study of this phenomenon, based on extensive {\\it Chandra} observations obtained from 1999 to 2012, totaling about 4.5 Ms. We detect flares, using a combination of the maximum likelihood and Markov Chain Monte Carlo methods, which allow for a direct accounting for the pile-up effect in the modeling of the flare...

  12. An Inverse Compton Scattering Origin of X-ray Flares from Sgr A*

    CERN Document Server

    Yusef-Zadeh, F; Dodds-Eden, K; Heinke, C O; Gillessen, S; Genzel, R; Bushouse, H; Grosso, N; Porquet, D

    2012-01-01

    The X-ray and near-IR emission from Sgr A* is dominated by flaring, while a quiescent component dominates the emission at radio and sub-mm wavelengths. The spectral energy distribution of the quiescent emission from Sgr A* peaks at sub-mm wavelengths and is modeled as synchrotron radiation from a thermal population of electrons in the accretion flow, with electron temperatures ranging up to $\\sim 5-20$\\,MeV. Here we investigate the mechanism by which X-ray flare emission is produced through the interaction of the quiescent and flaring components of Sgr A*. The X-ray flare emission has been interpreted as inverse Compton, self-synchrotron-Compton, or synchrotron emission. We present results of simultaneous X-ray and near-IR observations and show evidence that X-ray peak flare emission lags behind near-IR flare emission with a time delay ranging from a few to tens of minutes. Our Inverse Compton scattering modeling places constraints on the electron density and temperature distributions of the accretion flow an...

  13. The hard X-ray shortages prompted by the clock bursts in GS 1826-238

    International Nuclear Information System (INIS)

    We report on a study of GS 1826-238 using all available Rossi X-Ray Timing Explorer observations, concentrating on the behavior of the hard X-rays during type-I bursts. We find a hard X-ray shortage at 30-50 keV prompted by the shower of soft X-rays coming from type-I bursts. This shortage happens with a time delay after the peak of the soft flux of 3.6 ± 1.2 s. The behavior of hard X-rays during bursts indicates cooling and reheating of the corona, during which a large amount of energy is required. We speculate that this energy originates from the feedback of the type-I bursts to the accretion process, resulting in a rapid temporary increase of the accretion rate.

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

    DEFF Research Database (Denmark)

    Chenevez, Jérôme; Altamirano, Diego; Galloway, Duncan;

    2010-01-01

    We investigate the thermonuclear bursting behaviour of IGR J17473−2721, an X-ray transient that in 2008 underwent a 6-month long outburst, starting (unusually) with an X-ray burst. We detected a total of 57 thermonuclear bursts throughout the outburst with AGILE, Swift, Rossi X-ray Timing Explore...

  15. Correlation of hard X-ray and white light emission in solar flares

    CERN Document Server

    Kuhar, Matej; Oliveros, Juan Carlos Martínez; Battaglia, Marina; Kleint, Lucia; Casadei, Diego; Hudson, Hugh S

    2015-01-01

    A statistical study of the correlation between hard X-ray and white light emission in solar flares is performed in order to search for a link between flare-accelerated electrons and white light formation. We analyze 43 flares spanning GOES classes M and X using observations from RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager) and HMI (Helioseismic and Magnetic Imager). We calculate X-ray fluxes at 30 keV and white light fluxes at 6173 \\r{A} summed over the hard X-ray flare ribbons with an integration time of 45 seconds around the peak hard-X ray time. We find a good correlation between hard X-ray fluxes and excess white light fluxes, with a highest correlation coefficient of 0.68 for photons with energy of 30 keV. Assuming the thick target model, a similar correlation is found between the deposited power by flare-accelerated electrons and the white light fluxes. The correlation coefficient is found to be largest for energy deposition by electrons above ~50 keV. At higher electron energies the co...

  16. Particle Acceleration and the Origin of X-ray Flares in GRMHD simulations of Sgr A*

    CERN Document Server

    Ball, David; Psaltis, Dimitrios; Chan, Chi-kwan

    2016-01-01

    Significant X-ray variability and flaring has been observed from Sgr A* but is poorly understood from a theoretical standpoint. We perform GRMHD simulations that take into account a population of non-thermal electrons with energy distributions and injection rates that are motivated by PIC simulations of magnetic reconnection. We explore the effects of including these non-thermal electrons on the predicted broadband variability of Sgr A* and find that X-ray variability is a generic result of localizing non-thermal electrons to highly magnetized regions, where particles are likely to be accelerated via magnetic reconnection. The proximity of these high-field regions to the event horizon forms a natural connection between IR and X-ray variability and accounts for the rapid timescales associated with the X-ray flares. The qualitative nature of this variability is consistent with observations, producing X-ray flares that are always coincident with IR flares, but not vice versa, i.e., there are a number of IR flare...

  17. Risks due to X-ray Flares during Astronaut Extravehicular Activity

    CERN Document Server

    Smith, David S; 10.1029/2006SW000300

    2009-01-01

    Solar hard X-ray flares can expose astronauts on lunar and deep space extravehicular activities (EVAs) to dangerous acute biological doses. We combine calculations of radiative transfer through shielding materials with subsequent transfer through tissue to show that hazardous doses, taken as >= 0.1 Gy, should occur with a probability of about 10% per 100 hours of accumulated EVA inside current spacesuits. The rapid onset and short duration of X-ray flares and the lack of viable precursor events require strategies for quick retreat, in contrast to solar proton events, which usually take hours to deliver significant fluence and can often be anticipated by flares or other light-speed precursors. Our results contrast with the view that only particle radiation poses dangers for human space exploration. Heavy-element shields provide the most efficient protection from X-ray flares, since X-rays produce no significant secondary radiation. We calculate doses due to X-ray flares behind aluminum shields and estimate the...

  18. Long Type I X-ray Bursts and Neutron Star Interior Physics

    OpenAIRE

    Cumming, Andrew; Macbeth, Jared; Zand, J. J. M. in't; Page, Dany

    2005-01-01

    Superbursts are very energetic Type I X-ray bursts discovered in recent years by long term monitoring of X-ray bursters, believed to be due to unstable ignition of carbon in the deep ocean of the neutron star. A number of "intermediate duration" bursts have also been observed, probably associated with ignition of a thick helium layer. We investigate the sensitivity of these long X-ray bursts to the thermal profile of the neutron star crust and core. We first compare cooling models of superbur...

  19. The flare position obtained from MHD simulation and comparison with X-ray observations

    Science.gov (United States)

    Podgorny, Alexander; Podgorny, Igor

    It was for the first time shown that the position of the current sheet, obtained by numerical MHD simulation, coincides with the position of the thermal X-ray source. In our 3D MHD simulation we do not use any hypotheses about the flare mechanism. Several mechanisms of solar flare production are considered by different authors. Usually the initial conditions at numerical simulation are artificially set such a way that it is required for development of the proposed mechanism. In this approach, the unstable configuration of the magnetic field is set as the initial conditions, and the possibility of forming such an unstable system at the real evolution of the active region before the flare is not considered. Here the flare mechanism is obtained from the numerical MHD simulations in which all the conditions are taken from observations in the active region. It is shown that flare energy accumulation occurs in the current sheet magnetic field created by disturbances focusing in the vicinity of an X-type singular line. According to the developed solar flare electrodynamical model the thermal X-ray emission source appears in a current sheet, where plasma is heated due to magnetic field dissipation. Using 3D MHD numerical simulation the position of source of thermal X-ray emission are found for the flare occurred May 27, 2003 at 02:53. To find positions of sources of thermal X-ray radiation in the corona from MHD simulation results the graphical system is developed. The comparison with RHESSI X-ray observations show the coincidence of current sheet and observed the thermal X-ray emission source.

  20. The Thermal Properties of Solar Flares Over Three Solar Cycles Using GOES X-ray Observations

    CERN Document Server

    Ryan, Daniel F; Gallagher, Peter T; Dennis, Brian R; Tolbert, A Kim; Schwartz, Richard A; Young, C Alex

    2012-01-01

    Solar flare X-ray emission results from rapidly increasing temperatures and emission measures in flaring active region loops. To date, observations from the X-Ray Sensor (XRS) onboard the Geostationary Operational Environmental Satellite (GOES) have been used to derive these properties, but have been limited by a number of factors, including the lack of a consistent background subtraction method capable of being automatically applied to large numbers of flares. In this paper, we describe an automated temperature and emission measure-based background subtraction method (TEBBS), which builds on the methods of Bornmann (1990). Our algorithm ensures that the derived temperature is always greater than the instrumental limit and the pre-flare background temperature, and that the temperature and emission measure are increasing during the flare rise phase. Additionally, TEBBS utilizes the improved estimates of GOES temperatures and emission measures from White et al. (2005). TEBBS was successfully applied to over 50,...

  1. Flares of Sgr A*: from X-ray to mm

    Czech Academy of Sciences Publication Activity Database

    Zamaninasab, M.; Eckart, A.; Kunneriath, D.; Witzel, G.; Schödel, R.; Meyer, L.; Dovčiak, Michal; Karas, Vladimír; König, S.; Krichbaum, T.P.; Lu, R.-S.; Straubmeier, C.; Zensus, A.

    2008-01-01

    Roč. 79, č. 4 (2008), s. 1054-1057. ISSN 0037-8720. [Central Kiloparsec - Active Galactic Nuclei and Their Hosts. Ierapetra, Crete, 04.06.2008-06.06.2008] Institutional research plan: CEZ:AV0Z10030501 Keywords : black hole physics * X-rays general * accretion disks Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  2. Polarized NIR and X-ray flares from Sagittarius A*

    Czech Academy of Sciences Publication Activity Database

    Eckart, A.; Baganoff, F. K.; Zamaninasab, M.; Morris, M.; Schödel, R.; Meyer, L.; Muzic, K.; Bautz, M.W.; Brandt, W.N.; Garmire, G.P.; Ricker, G.; Kunneriath, D.; Straubmeier, C.; Duschl, W.J.; Dovčiak, Michal; Karas, Vladimír; Markoff, S. B.; Najarro, F.; Mauerhan, J.; Moultaka, J.; Zensus, A.

    2008-01-01

    Roč. 479, č. 3 (2008), s. 625-639. ISSN 0004-6361 Institutional research plan: CEZ:AV0Z10030501 Keywords : black hole physics * accretion disks * Galactic nucleus * NIR * X-rays * polarization Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.153, year: 2008

  3. Polarized NIR and X-ray flares from Sagittarius A*

    NARCIS (Netherlands)

    A. Eckart; F.K. Baganoff; M. Zamaninasab; M.R. Morris; R. Schödel; L. Meyer; K. Muzic; M.W. Bautz; W.N. Brandt; G.P. Garmire; G.R. Ricker; D. Kunneriath; C. Straubmeier; W. Duschl; M. Dovciak; V. Karas; S. Markoff; F. Najarro; J. Mauerhan; J. Moultaka; A. Zensus

    2008-01-01

    Context. Stellar dynamics indicate the presence of a supermassive 3 - 4 x 10(6) M-circle dot black hole at the Galactic Center. It is associated with the variable radio, near-infrared, and X-ray source Sagittarius A*(SgrA*). Aims. The goal is the investigation and understanding of the physical proce

  4. HARD X-RAY AND ULTRAVIOLET EMISSION DURING THE 2011 JUNE 7 SOLAR FLARE

    International Nuclear Information System (INIS)

    The relationship between X-ray and UV emission during flares, particularly in the context of quasi-periodic pulsations, remains unclear. To address this, we study the impulsive X-ray and UV emission during an eruptive flare on 2011 June 7 utilizing X-ray imaging from RHESSI and UV 1700 Å imaging from SDO/AIA. This event is associated with quasi-periodic pulsations in X-ray and possibly UV emission, as well as substantial parallel and perpendicular motion in the hard X-ray footpoints. The motion of the footpoints parallel to the flare ribbons is unusual; it reverses direction on at least two occasions. However, there is no associated short timescale motion of the UV bright regions. Over the same time interval, the footpoints also gradually move apart at v ≈ 12 km s–1, consistent with the gradual outward expansion of the UV ribbons and the standard flare model. Additionally, we find that the locations of the brightest X-ray and UV regions are different, particularly during the early portion of the flare impulsive phase, despite their integrated emission being strongly correlated in time. Correlation analysis of measured flare properties, such as the footpoint separation, flare shear, photospheric magnetic field, and coronal reconnection rate, reveals that—in the impulsive phase—the 25-50 keV hard X-ray flux is only weakly correlated with these properties, in contrast with previous studies. We characterize this event in terms of long-term behavior, where the X-ray non-thermal, thermal, and UV emission sources appear temporally and spatially consistent, and short-term behavior, where the emission sources are inconsistent and quasi-periodic pulsations are a dominant feature requiring explanation. We suggest that the short timescale behavior of hard X-ray footpoints and the nature of the observed quasi-periodic pulsations are determined by fundamental, as yet unobserved properties of the reconnection region and particle acceleration sites. This presents a

  5. Imaging observations of X-ray albedo in a compact disc flare

    Science.gov (United States)

    Battaglia, Marina; Kontar, Eduard

    X-rays from solar flare sources are an important diagnostic tool for particle acceleration and transport in the solar atmosphere. However, the observed flux at Earth is composed of direct emission and photons which are Compton backscattered from the photosphere. This contribu-tion can account for up to 40 We present imaging observations of a compact flare on the solar disc. The source full-width-half maximum was determined at different energies using X-ray visibility forward fitting. The observed source size increases and decreases with energy with a maximum size at about 40 keV, contrary to observations made in limb events. The behavior is consistent with predictions from Monte Carlo simulations of X-ray photon transport in which X-ray visibilities were computed from simulated maps and fitted using visibility forward fit.

  6. Looptop and Footpoint Impulsive Hard X-Rays and Stochastic Electron Acceleration in Solar Flares

    OpenAIRE

    Petrosian, Vahé

    2002-01-01

    The discovery of hard X-rays from tops of flaring loops by the HXT of YOHKOH represents a significant progress in the understanding of solar flares. This report describes the properties of 20 limb flares observed by YOHKOH from October 1991 to August 1998, 15 of which show detectable impulsive looptop emission. Considering the finite dynamic range (about a decade) of the detection it can be concluded that looptop emission is a common feature of all flares. The light curves and images of a rep...

  7. Evidence for X-ray synchrotron emission from simultaneous mid-IR to X-ray observations of a strong Sgr A* flare

    CERN Document Server

    Dodds-Eden, K; Trap, G; Quataert, E; Haubois, X; Gillessen, S; Grosso, N; Pantin, E; Falcke, H; Rouan, D; Genzel, R; Hasinger, G; Goldwurm, A; Yusef-Zadeh, F; Clénet, Y; Trippe, S; Lagage, P -O; Bartko, H; Eisenhauer, F; Ott, T; Paumard, T; Perrin, G; Yuan, F; Fritz, T K; Mascetti, L

    2009-01-01

    This paper reports measurements of Sgr A* made with NACO in L' -band (3.80 um), Ks-band (2.12 um) and H-band (1.66 um) and with VISIR in N-band (11.88 um) at the ESO VLT, as well as with XMM-Newton at X-ray (2-10 keV) wavelengths. On 4 April, 2007, a very bright flare was observed from Sgr A* simultaneously at L'-band and X-ray wavelengths. No emission was detected using VISIR. The resulting SED has a blue slope (beta > 0 for nuL_nu ~ nu^beta, consistent with nuL_nu ~ nu^0.4) between 12 micron and 3.8 micron. For the first time our high quality data allow a detailed comparison of infrared and X-ray light curves with a resolution of a few minutes. The IR and X-ray flares are simultaneous to within 3 minutes. However the IR flare lasts significantly longer than the X-ray flare (both before and after the X-ray peak) and prominent substructures in the 3.8 micron light curve are clearly not seen in the X-ray data. From the shortest timescale variations in the L'-band lightcurve we find that the flaring region must...

  8. Modification of gravitational redshift of x-ray burst produced by pulsar surface magnetoplasma

    Institute of Scientific and Technical Information of China (English)

    Zhu Jun; Ji Pei-Yong

    2008-01-01

    In this paper,the propagation of x-ray bursts in the magnetoplasma of pulsar magnetosphere is discussed.The electromagnetic interaction between x-ray bursts and magnetoplasma is described as some geometry.The electromagnetic effects of surface superstrong magnetic field and dynamic effects of outflowing magnetoplasma of pulsars are treated as an optical metric.The Gordon metric is introduced to represent the gravitational metric and optical metric.So the propagation of x-ray bursts in magnetoplasma of pulsars can be described as x-ray bursts transmitting in an effective space characterized by Gordon metric.The modification of gravitational redshift,attributed to the flowing magnetoplasma of pulsars,is obtained and it is shown that the modification is of redshift and can reach the same magnitude as the gravitational redshift for ordinary pulsars.

  9. Spectroscopic comparison between ultraluminous X-ray sources and magnetar bursts

    CERN Document Server

    Kajava, J J E

    2016-01-01

    Nearby galaxies host ultra-luminous X-ray sources (ULXs), whose nature remains largely unknown. Until the discovery of the first ULX pulsar, M82 X-2, the mechanism powering the large luminosities of most ULXs was thought to be super-Eddington accretion onto black holes. The ULX pulsar clearly indicates that this hypothesis is not universal, and the question arises if other ULXs are as well powered by accretion onto neutron stars. One possibility to have highly super-Eddington luminosity is by reducing the opacity by strong magnetic fields as in magnetars, as proposed for M82 X-2. To study the link between ULXs and magnetar bursts/flares, we have performed a comparative spectral study between these classes, which both emit at similar super-Eddington luminosities at around $L \\sim 10^{40}$ erg s$^{-1}$. We find that, when their spectra are fitted with dual thermal models, the long term spectral variations of ULXs are similar to short term spectral variability seen during magnetar flares. In both classes of sour...

  10. Inverse Compton X-rays from relativistic flare electrons and positrons

    CERN Document Server

    MacKinnon, Alec L

    2009-01-01

    In solar flares, inverse Compton scattering (ICS) of photospheric photons might give rise to detectable hard X-ray photon fluxes from the corona where ambient densities are too low for significant bremsstrahlung or recombination. Gamma-ray lines and continuum in some large flares imply the presence of the necessary ~100 MeV electrons and positrons, the latter as by-products of GeV energy ions. Recent observations of coronal hard X-ray sources in particular prompt us to reconsider here the possible contribution of ICS. We aim to evaluate the ICS X-ray fluxes to be expected from prescribed populations of relativistic electrons and positrons in the solar corona. The ultimate aim is to determine if ICS coronal X-ray sources might offer a new diagnostic window on relativistic electrons and ions in flares. We use the complete formalism of ICS to calculate X-ray fluxes from possible populations of flare primary electrons and secondary positrons, paying attention to the incident photon angular distribution near the s...

  11. Comparative study of x ray and microwave emissions during solar flares

    Science.gov (United States)

    Winglee, Robert M.

    1993-01-01

    The work supported by the grant consisted of two projects. The first project involved making detailed case studies of two flares using SMM data in conjunction with ground based observations. The first flare occurred at 1454 UT on June 20, 1989 and involved the eruption of a prominence near the limb. In the study we used data from many wavelength regimes including the radio, H-alpha, hard X-rays, and soft X-rays. We used a full gyrosynchrotron code to model the apparent presence of a 1.4 GHz source early in the flare that was in the form of a large coronal loop. The model results lead us to conclude that the initial acceleration occurs in small, dense loops which also produced the flare's hard X-ray emission. We also found evidence that a source at 1.4 GHz later in the event was due to second harmonic plasma emission. This source was adjacent to a leg of the prominence and comes from a dense column of material in the magnetic structure supporting the prominence. Finally, we investigated a source of microwaves and soft X-rays, occurring approximately 10 min after the hard X-ray peak, and calculate a lower limit for the density of the source. The second flare that was studied occurred at 2156 UT on June 20, 1989 and was observed with the VLA and the Owens Valley Radio Observatory (OVRO) Frequency Agile Array. We have developed a gyrosynchrotron model of the sources at flare peak using a new gyrosynchrotron approximation which is valid at very low harmonics of the gyrofrequency. We found that the accelerated particle densities of the sources decreased much more with radius from the source center than had been supposed in previous work, while the magnetic field varied less. We also used the available data to analyze a highly polarized source which appeared late in the flare. The second project involved compiling a statistical base for the relative timing of the hard X-ray peak, the turbulent and blue-shift velocities inferred from soft X-ray line emissions observed by

  12. The discovery of rapidly repetitive X-ray bursts from a new source in Scorpius

    Science.gov (United States)

    Lewin, W. H. G.; Doty, J.; Clark, G. W.; Bradt, H. V. D.; Doxsey, R.; Hearn, D. R.; Hoffman, J. A.; Jernigan, J. G.; Li, F. K.; Rappaport, S. A.

    1976-01-01

    Rapidly repetitive X-ray bursts have been observed from a new X-ray source in Scorpius. More than 2000 bursts were observed during the 4-day continual SAS-3 observations of this source designated MXB 1730-335. The time interval between bursts varied from a minimum of about 6 s to a maximum of about 5 minutes. The energy in a given burst is approximately linearly proportional to the time interval to the next burst. The largest bursts observed last for about 60 s and represent an energy release of approximately 10 to the 40th ergs for an assumed distance to the source of 10 kpc. The smallest bursts observed last only for a few seconds. We suggest that the bursts are caused by sporadic precipitations of plasma from a reservoir in the magnetosphere of a neutron star. The reservoir is replenished at a nearly constant rate by mass transferred from a binary companion.

  13. Latitudinal distribution of soft X-ray flares and dispairty in butterfly diagram

    Science.gov (United States)

    Pandey, K. K.; Yellaiah, G.; Hiremath, K. M.

    2015-04-01

    We present statistical analysis of about 63000 soft X-ray flare (class≥C) observed by geostationary operational environmental satellite (GOES) during the period 1976-2008. Class wise occurrence of soft X-ray (SXR) flare is in declining trend since cycle 21. The distribution pattern of cycle 21 shows the transit of hemispheric dominance of flare activity from northern to southern hemisphere and remains there during cycle 22 and 23. During the three cycles, 0-100, 21-300 latitude belts in southern hemisphere (SH) and 31-400 latitude belt in northern hemisphere (NH) are mightier. The 11-200 latitude belt of both hemisphere is mightiest. Correlation coefficient between consecutive latitude appears to be increasing from equator to poleward in northern hemisphere whereas pole to equatorward in southern hemisphere. Slope of the regression line fitted with asymmetry time series of daily flare counts is negative in all three cycles for different classes of flares. The yearly asymmetry curve fitted by a sinusoidal function varies from 5.6 to 11 years period and depends upon the intensity of flare. Variation, of curve fitted with wings of butterfly diagram, from first to second order polynomial suggests that latitudinal migration of flare activity varies from cycle to cycle, northern to southern hemisphere. The variation in slope of the butterfly wing of different flare class indicates the non uniform migration of flare activity.

  14. THE FERMI-GBM X-RAY BURST MONITOR: THERMONUCLEAR BURSTS FROM 4U 0614+09

    Energy Technology Data Exchange (ETDEWEB)

    Linares, M.; Chakrabarty, D. [Massachusetts Institute of Technology, Kavli Institute for Astrophysics and Space Research, Cambridge, MA 02139 (United States); Connaughton, V.; Bhat, P. N.; Briggs, M. S.; Preece, R. [CSPAR and Physics Department, University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Jenke, P.; Kouveliotou, C.; Wilson-Hodge, C. A. [Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Van der Horst, A. J. [Astronomical Institute ' Anton Pannekoek' , University of Amsterdam, NL-1090-GE Amsterdam (Netherlands); Camero-Arranz, A.; Finger, M.; Paciesas, W. S. [Universities Space Research Association, Huntsville, AL 35805 (United States); Beklen, E. [Physics Department, Suleyman Demirel University, 32260 Isparta (Turkey); Von Kienlin, A. [Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse, Postfach 1312, D-85748 Garching (Germany)

    2012-12-01

    Thermonuclear bursts from slowly accreting neutron stars (NSs) have proven difficult to detect, yet they are potential probes of the thermal properties of the NS interior. During the first year of a systematic all-sky search for X-ray bursts using the Gamma-ray Burst Monitor aboard the Fermi Gamma-ray Space Telescope we have detected 15 thermonuclear bursts from the NS low-mass X-ray binary 4U 0614+09 when it was accreting at nearly 1% of the Eddington limit. We measured an average burst recurrence time of 12 {+-} 3 days (68% confidence interval) between 2010 March and 2011 March, classified all bursts as normal duration bursts and placed a lower limit on the recurrence time of long/intermediate bursts of 62 days (95% confidence level). We discuss how observations of thermonuclear bursts in the hard X-ray band compare to pointed soft X-ray observations and quantify such bandpass effects on measurements of burst radiated energy and duration. We put our results for 4U 0614+09 in the context of other bursters and briefly discuss the constraints on ignition models. Interestingly, we find that the burst energies in 4U 0614+09 are on average between those of normal duration bursts and those measured in long/intermediate bursts. Such a continuous distribution in burst energy provides a new observational link between normal and long/intermediate bursts. We suggest that the apparent bimodal distribution that defined normal and long/intermediate duration bursts during the last decade could be due to an observational bias toward detecting only the longest and most energetic bursts from slowly accreting NSs.

  15. The Fermi-GBM X-Ray Burst Monitor: Thermonuclear Bursts from 4U 0614+09

    Science.gov (United States)

    Linares, M.; Connaughton, V.; Jenke, P.; van der Horst, A. J.; Camero-Arranz, A.; Kouveliotou, C.; Chakrabarty, D.; Beklen, E.; Bhat, P. N.; Briggs, M. S.; Finger, M.; Paciesas, W. S.; Preece, R.; von Kienlin, A.; Wilson-Hodge, C. A.

    2012-12-01

    Thermonuclear bursts from slowly accreting neutron stars (NSs) have proven difficult to detect, yet they are potential probes of the thermal properties of the NS interior. During the first year of a systematic all-sky search for X-ray bursts using the Gamma-ray Burst Monitor aboard the Fermi Gamma-ray Space Telescope we have detected 15 thermonuclear bursts from the NS low-mass X-ray binary 4U 0614+09 when it was accreting at nearly 1% of the Eddington limit. We measured an average burst recurrence time of 12 ± 3 days (68% confidence interval) between 2010 March and 2011 March, classified all bursts as normal duration bursts and placed a lower limit on the recurrence time of long/intermediate bursts of 62 days (95% confidence level). We discuss how observations of thermonuclear bursts in the hard X-ray band compare to pointed soft X-ray observations and quantify such bandpass effects on measurements of burst radiated energy and duration. We put our results for 4U 0614+09 in the context of other bursters and briefly discuss the constraints on ignition models. Interestingly, we find that the burst energies in 4U 0614+09 are on average between those of normal duration bursts and those measured in long/intermediate bursts. Such a continuous distribution in burst energy provides a new observational link between normal and long/intermediate bursts. We suggest that the apparent bimodal distribution that defined normal and long/intermediate duration bursts during the last decade could be due to an observational bias toward detecting only the longest and most energetic bursts from slowly accreting NSs.

  16. Boundary conditions for the solar burst phenomenons stablished from the statistical behaviour in the hard X-ray range

    International Nuclear Information System (INIS)

    A review on the statistical studies of solar burst parameters at X-rays and microwaves, as well as an analysis of the limits caused by instrumental sensitivity and their effect on the form of the distributions and on the establishment of boundary conditions for solar flare phenomena are presented. A study on the statistical behaviour of events observed with high sensitivity at hard X-rays with the HXRBS experiment (SMM) was performed. Maxima have been formed in the parameters distribution, which may be related to intrinsic characteristics of the source-regions. This result seems to confirm searly studies which indicated the influence of the sensitivity limits. Assuming the maxima of the distributions as real, it was possible to establish boundary conditions for the mechanisms of primary energy release. The principal condition establishes that solar bursts can be interpreted as a superposition of primary explosions. The statistical analysis permitted the estimate of a value for the amount of energy in a primary explosion, making use of adjustments of Poisson functions. The value found is consistent with values derived directly from ultra-fast time structures observed in bursts. Assuming an empirical pulse shape for the primary burst and the superposition condition, simulations of bursts have been successfully obtained. (Author)

  17. The Fermi-GBM X-ray burst monitor: thermonuclear bursts from 4U 0614+09

    CERN Document Server

    Linares, M; Jenke, P; van der Horst, A J; Camero-Arranz, A; Kouveliotou, C; Chakrabarty, D; Beklen, E; Bhat, P N; Briggs, M S; Finger, M; Paciesas, W; Preece, R; von Kienlin, A; Wilson-Hodge, C A

    2012-01-01

    Thermonuclear bursts from slowly accreting neutron stars (NSs) have proven difficult to detect, yet they are potential probes of the thermal properties of the neutron star interior. During the first year of a systematic all-sky search for X-ray bursts using the Gamma-ray Burst Monitor (GBM) aboard the Fermi Gamma-ray Space Telescope we have detected 15 thermonuclear bursts from the NS low-mass X-ray binary 4U 0614+09, when it was accreting at nearly 1% of the Eddington limit. We measured an average burst recurrence time of 12+/-3 d (68% confidence interval) between March 2010 and March 2011, classified all bursts as normal duration bursts and placed a lower limit on the recurrence time of long/intermediate bursts of 62 d (95% confidence level). We discuss how observations of thermonuclear bursts in the hard X-ray band compare to pointed soft X-ray observations, and quantify such bandpass effects on measurements of burst radiated energy and duration. We put our results for 4U 0614+09 in the context of other bu...

  18. Prediction soft-X-ray spectrum of solar flares from Very Low Frequency observations: an inverse problem in ionospheric science

    Science.gov (United States)

    Palit, Sourav; Chakrabarti, Sandip Kumar; Ray, Suman

    2016-07-01

    Earth's lower ionosphere and upper atmosphere absorb X-rays and gamma-rays from astronomical sources such as solar flares, Short Gamma ray Repeaters (SGRs) or Gamma Ray Bursts (GRBs). The electron-ion production rates due to the ionization of such energetic photons at different heights depend on the intensity and wavelength of the injected spectrum and hence vary from one source to another. Obviously the ion density vs. altitude profile has the imprint of the incident photon spectrum. In this paper, we examine the possibility of inverting the electron density-height profiles uniquely by deconvolution of the VLF amplitude signal to obtain information on the injected spectrum. We have been able to reproduce the soft-X-ray part of the injected spectra from two different classes of solar flares with satisfactory accuracy. With the possibilities of probing even lower parts of the atmosphere, the method presented here is useful to carry out a similar exercise to infer the higher energy part of solar flare spectra and spectra of more energetic events such as the GRBs, SGRs etc. We show that to a certain accuracy, the Earth's atmosphere may be used as a gigantic detector of relatively strong ionizing extra-terrestrial events.

  19. X-ray suppression in gamma-ray bursts through resonant Compton scattering

    Science.gov (United States)

    Brainerd, J. J.

    1992-01-01

    An X-ray that scatters with an electron in the first Landau level of a strong magnetic field is converted into a gamma ray. This process has a resonant cross section at X-ray energies and is therefore highly likely to occur even when the first Landau level is sparsely populated. Converted X-rays are cyclotron absorbed, maintaining the equilibrium between the cyclotron photon density and the population of the first Landau level. By suppressing a neutron star's black body emission, this mechanism can produce a gamma-ray burst with a low X-ray flux.

  20. Solar X-ray Flare Hazards on the Surface of Mars

    CERN Document Server

    Smith, D S; Smith, David S.; Scalo, John M.

    2006-01-01

    Putative organisms on the Martian surface would be exposed to potentially high doses of ionizing radiation during strong solar X-ray flares. We extrapolate the observed flare frequency-energy release scaling relation to releases much larger than seen so far for the sun, an assumption supported by observations of flares on other solar- and subsolar-mass main sequence stars. We calculate the surficial reprocessed X-ray spectra using a Monte Carlo code we have developed. Biological doses from indirect genome damage are calculated for each parameterized flare spectrum by integration over the X-ray opacity of water. We estimate the mean waiting time for solar flares producing a given biological dose of ionizing radiation on Mars and compare with lethal dose data for a wide range of terrestrial organisms. These timescales range from decades for significant human health risk to 0.5 Myr for D. radiodurans lethality. Such doses require total flare energies of 10^33--10^38 erg, the lower range of which has been observe...

  1. Energy relation between hard X-ray and O V emission in solar flares

    International Nuclear Information System (INIS)

    The relationship between energy emitted in hard X-rays and the ultraviolet during the impulsive phase of solar flares provides an important diagnostic for understanding the energy flow from nonthermal to thermal. Many flares were observed from the Solar Maximum Mission satellite simultaneously in hard X-rays and the O V line at 1371 A formed at 2.5 x 105 K, providing information relevant to this problem. Previous work has shown that short time scale peaks in emission of these two types of radiation coincide in time to within 1 s. In this work we investigate the energy relation between the two types of emission and find that for any given flare there is a difinite relation between hard X-ray and O V emissions throughout the flare, but from one flare to the next this relation varies markedly. We attribute these differences to the initial conditions in the flaring loops and present some exploratory model calculations to support this hypothesis

  2. Analysis of the 1980 November 18 limb flare observed by the hard X-ray imaging spectrometer (HXIS)

    NARCIS (Netherlands)

    Hoyng, P.; Haug, E.; Elwert, G.

    1984-01-01

    X-ray images of the 18 November 1980 limb flare taken by the HXIS instrument aboard SMM were analysed. The hard X-rays originated from three spots on the SW limb of the solar disk with different altitudes and time evolution. The locations of the brightest spots in hard and soft X-rays are compared w

  3. The X-ray Bursts from the Magnetar Candidate 1E 2259+586

    CERN Document Server

    Gavriil, F P; Woods, P M; Gavriil, Fotis P.; Kaspi, Victoria M.; Woods, Peter M.

    2004-01-01

    We present a statistical analysis of the X-ray bursts observed from the 2002 June 18 outburst of the Anomalous X-ray Pulsar (AXP) 1E 2259+586, observed with the Proportional Counter Array aboard the Rossi X-ray Timing Explorer. We show that the properties of these bursts are similar to those of Soft Gamma-Repeaters (SGRs). The similarities we find are: the burst durations follow a log-normal distribution which peaks at 99 ms, the differential burst fluence distribution is well described by a power law of index -1.7, the burst fluences are positively correlated with the burst durations, the distribution of waiting times is well described by a log-normal distribution of mean 47 s, and the bursts are generally asymmetric with faster rise than fall times. However, we find several quantitative differences between the AXP and SGR bursts. Specifically, there is a correlation of burst phase with pulsed intensity, the AXP bursts we observed exhibit a wider range of durations, the correlation between burst fluence and ...

  4. Transient response of the ionosphere to the X-ray solar flares

    Czech Academy of Sciences Publication Activity Database

    Chum, Jaroslav; Urbář, Jaroslav; Liu, J.-Y.

    Ostende: STCE, 2015. [European Space Weather Week /12./. 23.11.2015-27.11.2015, Ostende] Institutional support: RVO:68378289 Keywords : solar flare * X-rays * ionosphere * solar activity Subject RIV: DG - Athmosphere Sciences, Meteorology http://www.stce.be/esww12/program/session_details.php?nr=4#

  5. Science Fair Report: Detection of Solar X-Ray Flares with a Geiger Counter.

    Science.gov (United States)

    Mims, Vicki Rae

    1991-01-01

    Described is a science fair project in which M- and X-class x-ray flares on the surface of the earth were detected using a Geiger counter. Background information, the problem, hypothesis, a list of needed materials, the procedure, observations, conclusions, and a critique are included. (KR)

  6. Solar flares: radio and X-ray signatures of magnetic reconnection processes

    Czech Academy of Sciences Publication Activity Database

    Karlický, Marian

    2014-01-01

    Roč. 14, č. 7 (2014), s. 753-772. ISSN 1674-4527 R&D Projects: GA ČR GAP209/12/0103 Institutional support: RVO:67985815 Keywords : Sun: flares * Sun: radio radiation * Sun: X-rays Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 1.640, year: 2014

  7. THE THERMAL PROPERTIES OF SOLAR FLARES OVER THREE SOLAR CYCLES USING GOES X-RAY OBSERVATIONS

    International Nuclear Information System (INIS)

    Solar flare X-ray emission results from rapidly increasing temperatures and emission measures in flaring active region loops. To date, observations from the X-Ray Sensor (XRS) on board the Geostationary Operational Environmental Satellite (GOES) have been used to derive these properties, but have been limited by a number of factors, including the lack of a consistent background subtraction method capable of being automatically applied to large numbers of flares. In this paper, we describe an automated Temperature and Emission measure-Based Background Subtraction method (TEBBS), that builds on the methods of Bornmann. Our algorithm ensures that the derived temperature is always greater than the instrumental limit and the pre-flare background temperature, and that the temperature and emission measure are increasing during the flare rise phase. Additionally, TEBBS utilizes the improved estimates of GOES temperatures and emission measures from White et al. TEBBS was successfully applied to over 50,000 solar flares occurring over nearly three solar cycles (1980-2007), and used to create an extensive catalog of the solar flare thermal properties. We confirm that the peak emission measure and total radiative losses scale with background subtracted GOES X-ray flux as power laws, while the peak temperature scales logarithmically. As expected, the peak emission measure shows an increasing trend with peak temperature, although the total radiative losses do not. While these results are comparable to previous studies, we find that flares of a given GOES class have lower peak temperatures and higher peak emission measures than previously reported. The TEBBS database of flare thermal plasma properties is publicly available at http://www.SolarMonitor.org/TEBBS/.

  8. Bright X-ray flares in XRF 050406 and GRB 050502B provide evidence for extended central engine activity

    CERN Document Server

    Burrows, D N; Falcone, A; Kobayashi, S; Zhang, B; Moretti, A; O'Brien, P T; Goad, M R; Campana, S; Page, K L; Angelini, L; Barthelmy, S D; Beardmore, A P; Capalbi, M; Chincarini, G; Cummings, J; Cusumano, G; Fox, D; Giommi, P; Hill, J E; Kennea, J A; Krimm, H; Mangano, V; Marshall, F; Mészáros, P; Morris, D C; Nousek, J A; Osborne, J P; Pagani, C; Perri, M; Tagliaferri, G; Wells, A A; Woosley, S; Gehrels, N

    2005-01-01

    Gamma-ray bursts (GRBs) are the most powerful explosions since the Big Bang, with typical energies around 10**51 ergs. Long GRBs (duration > 2 s) are thought to signal the creation of black holes, most likely by collapse of massive stars. The detected signals from the resulting highly relativistic fireball consist of prompt gamma-ray emission (from internal shocks in the fireball) lasting for several seconds to minutes, followed by afterglow emission (from external shocks as the fireball encounters surrounding material) covering a broad range of frequencies from radio through X-rays. Because of the time needed to determine the GRB position, most afterglow measurements have been made hours after the burst, and little is known about the characteristics of afterglows in the minutes following a burst, when the afterglow emission is actively responding to inhomogeneities in both the fireball and the circumburst environment. Here we report our discovery of two bright X-ray flares peaking a few minutes after the bur...

  9. What can NuSTAR do for X-ray bursts?

    DEFF Research Database (Denmark)

    Chenevez, Jérôme; Tomsick, John; Chakrabarty, Deepto;

    2012-01-01

    Unstable thermonuclear burning on the surface of accreting neutron stars is commonly observed as type I X-ray bursts. The flux released during some strong bursts can temporarily exceed the Eddington limit, driving the neutron star photosphere to such large radii that heavy-element ashes of nuclear...

  10. What can NuSTAR do for X-ray bursts?

    DEFF Research Database (Denmark)

    Chenevez, Jérôme; Tomsick, J.; Chakrabarty, D.;

    Unstable thermonuclear burning on the surface of accreting neutron stars is commonly observed as type I X-ray bursts. The flux released during some strong bursts can temporarily exceed the Eddington limit, driving the neutron star photosphere to such large radii that heavy-element ashes of nuclear...

  11. Continuous heating of a giant X-ray flare on Algol

    OpenAIRE

    Schmitt, J. H. M. M.; Favata, F.

    1999-01-01

    Giant flares can release large amounts of energy within a few days: X-ray emission alone can be up to ten percent of the star's bolometric luminosity. These flares exceed the luminosities of the largest solar flares by many orders of magnitude, which suggests that the underlying physical mechanisms supplying the energy are different from those on the Sun. Magnetic coupling between the components in a binary system or between a young star and an accretion disk has been proposed as a prerequisi...

  12. The first radius-expansion X-ray burst from GX 3+1

    OpenAIRE

    Kuulkers, E; Klis, van der, M.

    2000-01-01

    During several observations in 1999 August with RXTE of the low-mass X-ray binary GX 3+1, we found a single short and strong X-ray burst. This is the first burst from GX 3+1 which clearly shows evidence for radius expansion of the neutron-star photosphere during the thermo-nuclear runaway. We show that the cooling phase of the neutron star photosphere starts already just before the end of the contraction phase. Considering the fact that the radius expansion is due to the burst luminosity bein...

  13. Three X-ray Flares Near Primary Eclipse of the RS CVn Binary XY UMa

    CERN Document Server

    Gong, Hang; Maccarone, Thomas; Reale, Fabio; Liu, Jifeng; Heckert, Paul A

    2016-01-01

    We report on an archival X-ray observation of the eclipsing RS CVn binary XY UMa ($\\rm P_{orb}\\approx$ 0.48d). In two $\\emph{Chandra}$ ACIS observations spanning 200 ks and almost five orbital periods, three flares occurred. We find no evidence for eclipses in the X-ray flux. The flares took place around times of primary eclipse, with one flare occurring shortly ($<0.125\\rm P_{orb}$) after a primary eclipse, and the other two happening shortly ($<0.05\\rm P_{orb}$) before a primary eclipse. Two flares occurred within roughly one orbital period ($\\Delta \\phi\\approx1.024\\rm P_{orb}$) of each other. We analyze the light curve and spectra of the system, and investigate coronal length scales both during quiescence and during flares, as well as the timing of the flares. We explore the possibility that the flares are orbit-induced by introducing a small orbital eccentricity, which is quite challenging for this close binary.

  14. EVIDENCE FOR X-RAY SYNCHROTRON EMISSION FROM SIMULTANEOUS MID-INFRARED TO X-RAY OBSERVATIONS OF A STRONG Sgr A* FLARE

    International Nuclear Information System (INIS)

    This paper reports measurements of Sgr A* made with NACO in L' band (3.80 μm), Ks band (2.12 μm), and H band (1.66 μm), and with VISIR in N band (11.88 μm) at the ESO VLT, as well as with XMM-Newton at X-ray (2-10 keV) wavelengths. On 2007 April 4, a very bright flare was observed from Sgr A* simultaneously at L' band and X-ray wavelengths. No emission was detected using VISIR. The resulting spectral energy distribution has a blue slope (β>0 for νL ν ∝ νβ, consistent with νL ν ∝ ν0.4) between 12 μm and 3.8 μm. For the first time, our high-quality data allow a detailed comparison of infrared (IR) and X-ray light curves with a resolution of a few minutes. The IR and X-ray flares are simultaneous to within 3 minutes. However, the IR flare lasts significantly longer than the X-ray flare (both before and after the X-ray peak), and prominent substructures in the 3.8 μm light curve are clearly not seen in the X-ray data. From the shortest timescale variations in the L'-band light curve, we find that the flaring region must be no more than 1.2RS in size. The high X-ray to IR flux ratio, blue νL ν slope MIR to L' band, and the soft νL ν spectral index of the X-ray flare together place strong constraints on possible flare emission mechanisms. We find that it is quantitatively difficult to explain this bright X-ray flare with inverse Compton processes. A synchrotron emission scenario from an electron distribution with a cooling break is a more viable scenario.

  15. The Variable Crab Nebula: Evidence for a Connection between GeV flares and Hard X-ray Variations

    Science.gov (United States)

    Wilson-Hodge, Colleen A.; Kust Harding, Alice; Hays, Elizabeth A.; Cherry, Michael L.; Case, Gary L.; Finger, Mark H.; Jenke, Peter; Zhang, Xiao-Ling

    2016-04-01

    In 2010, hard X-ray variations (Wilson-Hodge et al. 2011) and GeV flares (Tavani et al 2011, Abdo et al. 2011) from the Crab Nebula were discovered. Connections between these two phenomena were unclear, in part because the timescales were quite different, with yearly variations in hard X-rays and hourly to daily variations in the GeV flares. The hard X-ray flux from the Crab Nebula has again declined since 2014, much like it did in 2008-2010. During both hard X-ray decline periods, the Fermi LAT detected no GeV flares, suggesting that injection of particles from the GeV flares produces the much slower and weaker hard X-ray variations. The timescale for the particles emitting the GeV flares to lose enough energy to emit synchrotron photons in hard X-rays is consistent with the yearly variations observed in hard X-rays and with the expectation that the timescale for variations slowly increases with decreasing energy. This hypothesis also predicts even slower and weaker variations below 10 keV, consistent with the non-detection of counterparts to the GeV flares by Chandra (Weisskopf et al 2013). We will present a comparison of the observed hard X-ray variations and a simple model of the decay of particles from the GeV flares to test our hypothesis.

  16. The Variable Crab Nebula: Evidence for a Connection Between GeV Flares and Hard X-ray Variations

    Science.gov (United States)

    Wilson-Hodge, Colleen A.; Harding, A. K.; Hays, E. A.; Cherry, M. L.; Case, G. L.; Finger, M. H.; Jenke, P.; Zhang, X.

    2016-01-01

    In 2010, hard X-ray variations (Wilson-Hodge et al. 2011) and GeV flares (Tavani et al 2011, Abdo et al. 2011) from the Crab Nebula were discovered. Connections between these two phenomena were unclear, in part because the timescales were quite different, with yearly variations in hard X-rays and hourly to daily variations in the GeV flares. The hard X-ray flux from the Crab Nebula has again declined since 2014, much like it did in 2008-2010. During both hard X-ray decline periods, the Fermi LAT detected no GeV flares, suggesting that injection of particles from the GeV flares produces the much slower and weaker hard X-ray variations. The timescale for the particles emitting the GeV flares to lose enough energy to emit synchrotron photons in hard X-rays is consistent with the yearly variations observed in hard X-rays and with the expectation that the timescale for variations slowly increases with decreasing energy. This hypothesis also predicts even slower and weaker variations below 10 keV, consistent with the non-detection of counterparts to the GeV flares by Chandra (Weisskopf et al 2013). We will present a comparison of the observed hard X-ray variations and a simple model of the decay of particles from the GeV flares to test our hypothesis.

  17. The WATCH solar X-ray burst catalogue

    DEFF Research Database (Denmark)

    Crosby, N.; Lund, Niels; Vilmer, N.; Sunyaev, R.

    1998-01-01

    The WATCH experiment aboard the GRANAT satellite provides observations of the Sun in the deka-keV range covering the years 1990 through mid-1992. An introduction to the experiment is given followed by an explanation of how the WATCH solar burst catalogue was created. The different parameters listed...... for each burst is given and are furthermore explained....

  18. Skylab ATM/S-056 X-ray event analyzer: Instrument description, parameter determination, and analysis example (15 June 1973 1B/M3 flare)

    Science.gov (United States)

    Wilson, R. M.

    1976-01-01

    The Skylab ATM/S-056 X-Ray Event Analyzer, part of an X-ray telescope experiment, is described. The techniques employed in the analysis of its data to determine electron temperatures and emission measures are reviewed. The analysis of a sample event - the 15 June 1973 1B/M3 flare - is performed. Comparison of the X-Ray Event Analyzer data with that of the SolRad 9 observations indicates that the X-Ray Event Analyzer accurately monitored the sun's 2.5 to 7.25 A X-ray emission and to a lesser extent the 6.1 to 20 A emission. A mean average peak temperature of 15 million K at 1,412 UT and a mean average peak electron density (assuming a flare volume of 10 to the 13 power cu km) of 27 million/cu mm at 1,416 to 1,417 UT are deduced for the event. The X-Ray Event Analyzer data, having a 2.5 s time resolution, should be invaluable in comparisons with other high-time resolution data (e.g., radio bursts).

  19. Long duration X-ray burst from GX 3+1

    DEFF Research Database (Denmark)

    Brandt, Søren; Lund, Niels; Chenevez, Jérôme;

    2004-01-01

    During an observation of the Galactic Center the JEM-X instrument on INTEGRAL detected an unusally long X-ray burst from GX 3+1. The burst began on August 31 at 18:57 UTC After an precursor spike lasting 7 s where the burst reached a flux of about 2000 mCrab in the 4 to 20 keV band the flux fell to...

  20. A systematic Chandra study of Sgr A⋆ - I. X-ray flare detection

    Science.gov (United States)

    Yuan, Qiang; Wang, Q. Daniel

    2016-02-01

    Daily X-ray flaring represents an enigmatic phenomenon of Sagittarius A⋆ (Sgr A⋆) - the supermassive black hole at the centre of our Galaxy. We report initial results from a systematic X-ray study of this phenomenon, based on extensive Chandra observations obtained from 1999 to 2012, totalling about 4.5 Ms. We detect flares, using a combination of the maximum likelihood and Markov Chain Monte Carlo methods, which allow for a direct accounting for the pileup effect in the modelling of the flare light curves and an optimal use of the data, as well as the measurements of flare parameters, including their uncertainties. A total of 82 flares are detected. About one third of them are relatively faint, which were not detected previously. The observation-to-observation variation of the quiescent emission has an average root-mean-square of 6-14 per cent, including the Poisson statistical fluctuation of faint flares below our detection limits. We find no significant long-term variation in the quiescent emission and the flare rate over the 14 years. In particular, we see no evidence of changing quiescent emission and flare rate around the pericentre passage of the S2 star around 2002. We show clear evidence of a short-term clustering for the Advanced CCD Imaging Spectrometer - Spectroscopy array/high energy transmission gratings 0th-order flares on time-scale of 20-70 ks. We further conduct detailed simulations to characterize the detection incompleteness and bias, which is critical to a comprehensive follow-up statistical analysis of flare properties. These studies together will help to establish Sgr A⋆ as a unique laboratory to understand the astrophysics of prevailing low-luminosity black holes in the Universe.

  1. 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. The ...

  2. INTEGRAL study of temporal properties of bright flares in Supergiant Fast X-ray Transients

    CERN Document Server

    Sidoli, L; Postnov, K

    2016-01-01

    We have characterized the typical temporal behaviour of the bright X-ray flares detected from the three Supergiant Fast X-ray Transients showing the most extreme transient behaviour (XTEJ1739-302, IGRJ17544-2619, SAXJ1818.6-1703). We focus here on the cumulative distributions of the waiting-time (time interval between two consecutive X-ray flares), and the duration of the hard X-ray activity (duration of the brightest phase of an SFXT outburst), as observed by INTEGRAL/IBIS in the energy band 17-50 keV. Adopting the cumulative distribution of waiting-times, it is possible to identify the typical timescale that clearly separates different outbursts, each composed by several single flares at ks timescale. This allowed us to measure the duration of the brightest phase of the outbursts from these three targets, finding that they show heavy-tailed cumulative distributions. We observe a correlation between the total energy emitted during SFXT outbursts and the time interval covered by the outbursts (defined as the ...

  3. Principal component analysis of solar flares in the soft X-ray flux

    Science.gov (United States)

    Teuber, D. L.; Reichmann, E. J.; Wilson, R. M.

    1979-01-01

    The paper considers principal component analysis of solar flares in the soft X-ray flux, a technique for extracting the salient features from a mass of data. The method applies particularly to the analysis of nonstationary ensembles, and its computations require the evaluation of eigenvalues of matrices. The Eispack matrix eigen system routines were used to analyze full-disk proportional-counter data from the X-ray event analyzer which was part of the Skylab experiment. Empirical orthogonal functions were derived for events in the soft X-ray spectrum between 2.5 and 20 A during different time periods, indicating that about 90% of the cumulative power of each analyzed flare is contained in the largest eigenvector. The first two largest eigenvectors are sufficient for an empirical curve fit through the raw data and a characterization of solar flares in the soft X-ray flux, and power spectra of two largest eigenvectors reveal a reported periodicity of about 5 min.

  4. MULTI-WAVELENGTH OBSERVATIONS OF SOLAR FLARES WITH A CONSTRAINED PEAK X-RAY FLUX

    International Nuclear Information System (INIS)

    We present an analysis of soft X-ray (SXR) and extreme-ultraviolet (EUV) observations of solar flares with an approximate C8 Geostationary Operational Environmental Satellite (GOES) class. Our constraint on peak GOES SXR flux allows for the investigation of correlations between various flare parameters. We show that the duration of the decay phase of a flare is proportional to the duration of its rise phase. Additionally, we show significant correlations between the radiation emitted in the flare rise and decay phases. These results suggest that the total radiated energy of a given flare is proportional to the energy radiated during the rise phase alone. This partitioning of radiated energy between the rise and decay phases is observed in both SXR and EUV wavelengths. Though observations from the EUV Variability Experiment show significant variation in the behavior of individual EUV spectral lines during different C8 events, this work suggests that broadband EUV emission is well constrained. Furthermore, GOES and Atmospheric Imaging Assembly data allow us to determine several thermal parameters (e.g., temperature, volume, density, and emission measure) for the flares within our sample. Analysis of these parameters demonstrate that, within this constrained GOES class, the longer duration solar flares are cooler events with larger volumes capable of emitting vast amounts of radiation. The shortest C8 flares are typically the hottest events, smaller in physical size, and have lower associated total energies. These relationships are directly comparable with several scaling laws and flare loop models.

  5. A Systematic Chandra study of Sgr A$^{\\star}$: I. X-ray flare detection

    CERN Document Server

    Yuan, Qiang

    2016-01-01

    Daily X-ray flaring represents an enigmatic phenomenon of Sgr A$^{\\star}$ --- the supermassive black hole at the center of our Galaxy. We report initial results from a systematic X-ray study of this phenomenon, based on extensive {\\it Chandra} observations obtained from 1999 to 2012, totaling about 4.5 Ms. We detect flares, using a combination of the maximum likelihood and Markov Chain Monte Carlo methods, which allow for a direct accounting for the pile-up effect in the modeling of the flare lightcurves and an optimal use of the data, as well as the measurements of flare parameters, including their uncertainties. A total of 82 flares are detected. About one third of them are relatively faint, which were not detected previously. The observation-to-observation variation of the quiescent emission has an average root-mean-square of $6\\%-14\\%$, including the Poisson statistical fluctuation of faint flares below our detection limits. We find no significant long-term variation in the quiescent emission and the flar...

  6. Plasma heating in solar flares and their soft and hard X-ray emissions

    International Nuclear Information System (INIS)

    In this paper, the energy budgets of two single-loop-like flares observed in X-ray are analyzed under the assumption that nonthermal electrons (NTEs) are the only source of plasma heating during all phases of both events. The flares were observed by RHESSI and GOES on 2002 February 20 and June 2, respectively. Using a one-dimensional (1D) hydrodynamic code for both flares, the energy deposited in the chromosphere was derived applying RHESSI observational data. The use of the Fokker-Planck formalism permits the calculation of distributions of the NTEs in flaring loops and thus spatial distributions of the X-ray nonthermal emissions and integral fluxes for the selected energy ranges that were compared with the observed ones. Additionally, a comparative analysis of the spatial distributions of the signals in the RHESSI images was conducted for the footpoints and for all the flare loops in selected energy ranges with these quantities' fluxes obtained from the models. The best compatibility of the model and observations was obtained for the 2002 June 2 event in the 0.5-4 Å GOES range and total fluxes in the 6-12 keV, 12-25 keV, 20-25 keV, and 50-100 keV energy bands. Results of photometry of the individual flaring structures in a high energy range show that the best compliance occurred for the 2002 June 2 flare, where the synthesized emissions were at least 30% higher than the observed emissions. For the 2002 February 20 flare, synthesized emission is about four times lower than the observed one. However, in the low energy range the best conformity was obtained for the 2002 February 20 flare, where emission from the model is about 11% lower than the observed one. The larger inconsistency occurs for the 2002 June 2 solar flare, where synthesized emission is about 12 times greater or even more than the observed emission. Some part of these differences may be caused by inevitable flaws of the applied methodology, like by an assumption that the model of the flare is

  7. Investigation of the X-Ray Emission of the Large Arcade Flare of 2 March 1993

    Science.gov (United States)

    Jakimiec, J.; Tomczak, M.

    2014-06-01

    A large arcade flare, occurring on 2 March 1993, has been investigated using X-ray observations recorded by the Yohkoh and GOES satellites and the Compton Gamma Ray Observatory. We analyzed the quasi-periodicity of the hard-X-ray (HXR) pulses in the impulsive phase of the flare and found a close similarity between the quasi-periodic sequence of the pulses to that observed in another large arcade flare, that of 2 November 1991. This similarity helped to explain the strong HXR pulses which were recorded at the end of the impulsive phase as due to the inflow of dense plasma (coming from the chromospheric evaporation) into the acceleration volume inside the cusp. In HXR images a high flaring loop was seen with a triangular cusp structure at the top, where the electrons were efficiently accelerated. The sequence of HXR images allowed us to investigate complicated changes in the precipitation of the accelerated electrons toward the flare footpoints. We have shown that all these impulsive-phase observations can be easily explained in terms of the model of electron acceleration in oscillating magnetic traps located within the cusp structure. Some soft-X-ray (SXR) images were available for the late decay phase. They show a long arcade of SXR loops. Important information about the evolution of the flare during the slow decay phase is contained in the time variation of the temperature, T( t), and emission measure, EM( t). This information is the following: i) weak heating occurs during the slow decay phase and it slowly decreases; ii) the decrease in the heating determines a slow and smooth decrease in EM; iii) the coupling between the heating and the amount of the hot plasma makes the flare evolve along a sequence of quasi-steady states during the slow decay phase (QSS evolution).

  8. The 3 Ms Chandra Campaign on Sgr A*: A Census of X-ray Flaring Activity from the Galactic Center

    CERN Document Server

    Neilsen, J; Gammie, C; Dexter, J; Markoff, S; Haggard, D; Nayakshin, S; Wang, Q D; Grosso, N; Porquet, D; Tomsick, J A; Degenaar, N; Fragile, P C; Houck, J C; Wijnands, R; Miller, J M; Baganoff, F K

    2013-01-01

    Over the last decade, X-ray observations of Sgr A* have revealed a black hole in a deep sleep, punctuated roughly once per day by brief flares. The extreme X-ray faintness of this supermassive black hole has been a long-standing puzzle in black hole accretion. To study the accretion processes in the Galactic Center, Chandra (in concert with numerous ground- and space-based observatories) undertook a 3 Ms campaign on Sgr A* in 2012. With its excellent observing cadence, sensitivity, and spectral resolution, this Chandra X-ray Visionary Project (XVP) provides an unprecedented opportunity to study the behavior of the closest supermassive black hole. We present a progress report from our ongoing study of X-ray flares, including the brightest flare ever seen from Sgr A*. Focusing on the statistics of the flares and the quiescent emission, we discuss the physical implications of X-ray variability in the Galactic Center.

  9. Localization of the solar flare SF900610 in X-rays with the WATCH instrument of the GRANAT observatory

    DEFF Research Database (Denmark)

    Terekhov, O.V.; Kuzmin, A.G.; Shevchenko, A.V.;

    2002-01-01

    During the solar flare of June 10, 1990, the WATCH instrument of the GRANAT space observatory obtained 110 localizations of the X-ray source in the X-ray range 8-20 keV. Its coordinates were measured with an accuracy of similar to2 arcmin at a 3sigma confidence level. The coordinates of the X......-ray source do not coincide with the coordinates of the Ha-line flare. The X-ray source moved over the solar disk during the flare. This probably implies that, as the X-ray emission was generated, different parts of one loop or a system of magnetic loops dominated at different flare times....

  10. Solar flare composition and thermodynamics from RESIK X-ray spectra

    International Nuclear Information System (INIS)

    Previous estimates of the solar flare abundances of Si, S, Cl, Ar, and K from the RESIK X-ray crystal spectrometer on board the CORONAS-F spacecraft were made on the assumption of isothermal X-ray emission. We investigate the effect on these estimates by relaxing this assumption and instead determining the differential emission measure (DEM) or thermal structure of the emitting plasma by re-analyzing RESIK data for a GOES class M1.0 flare on 2002 November 14 (SOL2002-11-14T22:26) for which there was good data coverage. The analysis method uses a maximum-likelihood (Withbroe-Sylwester) routine for evaluating the DEM. In a first step, called here AbuOpt, an optimized set of abundances of Si, S, Ar, and K is found that is consistent with the observed spectra. With these abundances, the DEM evolution during the flare is found. The abundance optimization leads to revised abundances of silicon and sulfur in the flare plasma: A(S) = 6.94 ± 0.06 and A(Si) = 7.56 ± 0.08 (on a logarithmic scale with A(H) = 12). Previously determined abundances of Ar, K, and Cl from an isothermal assumption are still the preferred values. During the flare's maximum phase, the X-ray-emitting plasma has a basically two-temperature structure, with the cooler plasma with approximately constant temperature (3-6 MK) and a hotter plasma with temperature 16-21 MK. Using imaging data from the RHESSI hard X-ray spacecraft, the emission volume of the hot plasma is deduced from which lower limits of the electron density Ne and the thermal content of the plasma are given.

  11. Iron lines in the X-ray afterglows of Gamma-ray bursts

    Science.gov (United States)

    Piro, L.

    1998-12-01

    X-ray measurements of iron lines can provide a powerful diagnostics of the environment of Gamma-ray bursts, thus enlightening the still misterious nature of the central engine powering these phenomena. Furthermore, they would allow a direct measurement of the distance of the GRB, bypassing completely the long chain of steps that, from the Gamma and X-ray localization, brings to the optical determination of the redshift. In this contribution we will present the results of a search of this feature in the BeppoSAX X-ray afterglows of GRB. We will discuss their implication for near future missions, as AXAF and XMM.

  12. Beacons in the sky. Classical novae vs. X-ray bursts

    International Nuclear Information System (INIS)

    Thermonuclear runaways are at the origin of some of the most energetic and frequent stellar cataclysmic events. In this review talk, we outline our understanding of the mechanisms leading to classical nova explosions and X-ray bursts, together with their associated nucleosynthesis. In particular, we focus on the interplay between nova outbursts and the Galactic chemical abundances (mainly 13C, 15N, and 17O), the synthesis of radioactive nuclei of interest for gamma-ray astronomy (7Be-7Li, 22Na, or 26Al), the endpoint of nova nucleosynthesis, based both on theoretical and observational grounds, and the recent discovery of presolar meteoritic grains, both in the Murchison and Acfer 094 meteorites, likely condensed in nova shells. Recent progress in the modeling of X-ray bursts as well as an insight into the nuclear uncertainties affecting critical reactions, for both novae and X-ray bursts, will also be presented. (author)

  13. Stellar Pyrotechnics: Nucleosynthesis in Classical Novae and X-Ray Bursts

    International Nuclear Information System (INIS)

    Thermonuclear runaways are at the origin of some of the most energetic and frequent stellar cataclysmic events. In this paper, we review our understanding of the mechanisms leading to classical nova explosions and x-ray bursts, together with their associated nu- cleosynthesis. In particular, we focus on the interplay between nova outbursts and the Galactic chemical abundances (mainly 13C, 15N, and 17O), the synthesis of radioactive nuclei of interest for gamma-ray astronomy (7Be-7Li, 22Na, or 26Al), the endpoint of nova nucleosynthesis, based both on theoretical and observational grounds, and the recent discovery of presolar meteoritic grains, both in the Murchison and Acfer 094 meteorites, likely condensed in nova shells. Recent progress in the modeling of x-ray bursts as well as an insight into the nuclear uncertainties affecting critical reactions, for both novae and x-ray bursts, are also reviewed

  14. Hard X-ray morphology of the X1.3 April 25, 2014 partially occulted limb solar flare

    CERN Document Server

    Effenberger, Frederic; Petrosian, Vahe

    2016-01-01

    At hard X-ray energies, the bright footpoint emission from solar flare loops often prevents a detailed analysis of the weaker loop-top source morphology due to the limited dynamic range available for X-ray imaging. Here, we study the X1.3 April 25, 2014 flare with the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI). This partially occulted limb flare allows the analysis of the loop-top emission in isolation. We present results on the flare light curve at different energies, the source morphology from X-ray imaging and a detailed spectral analysis of the different source components by imaging spectroscopy. The loop-top source, a likely site of particle acceleration, shows a clear composition of different emission components. The results indicate the opportunities that detailed imaging of hard X-rays can provide to learn about particle acceleration, transport and heating processes in solar flares.

  15. X-Ray Flares and Oscillations from the Black Hole Candidate X-Ray Transient XTE J1650-500 at Low Luminosity

    CERN Document Server

    Tomsick, J A; Corbel, S; Kaaret, P E; Tomsick, John A.; Kalemci, Emrah; Corbel, Stephane; Kaaret, Philip

    2003-01-01

    We report on X-ray observations made with the Rossi X-ray Timing Explorer of the black hole candidate (BHC) transient XTE J1650-500 at the end of its first, and currently only, outburst. By monitoring the source at low luminosities over several months, we found 6 bright ~100 second X-ray flares and long time scale oscillations of the X-ray flux. The oscillations are aperiodic with a characteristic time scale of 14.2 days and an order of magnitude variation in the 2.8-20 keV flux. The oscillations may be related to optical "mini-outbursts" that have been observed at the ends of outbursts for other short orbital period BHC transients. The X-ray flares have durations between 62 and 215 seconds and peak fluxes that are 5-24 times higher than the persistent flux. The flares have non-thermal energy spectra and occur when the persistent luminosity is near 3E34 (d/4 kpc)^2 erg/s (2.8-20 keV). The rise time for the brightest flare demonstrates that physical models for BHC systems must be able to account for the situat...

  16. Parameters of Type I Chains and Their Association with Flares in X-ray

    Science.gov (United States)

    Sodré, Z. A. L.; Fernandes, F. C. R.

    2016-04-01

    Chains of type I are associated with the Radio Noise Storms (RNS). We report the analysis of the parameters of the two RNS: one associated with the occurrence of solar flares in X-rays and one recorded on a day without the presence of a flare. The spectral information about the chains in these events were obtained from the e-CALLISTO (Compact Astronomical Low-cost Low-frequency Instrument for Spectroscopy and Transportable Observatory) network. On 07/May/2011 (day without flare) the bandwidth was in the range 5.7 - 91 MHz, the duration varied from 7 - 361 seconds, and the drift-rate frequency was in the range -5.2 - +2.5 MHz s-1. The day with flare (01/August/2011) had bandwidth in the range of 4.7 - 60 MHz, duration between 6 and 214 seconds, and frequency drift-rate varying from -6 to +1.8 MHz s-1.

  17. Gamma-ray burst optical light-curve zoo: comparison with X-ray observations

    CERN Document Server

    Zaninoni, Elena; Margutti, Raffaella; Oates, Samantha; Chincarini, Guido

    2013-01-01

    We present a comprehensive analysis of the optical and X-ray light curves (LCs) and spectral energy distributions (SEDs) of a large sample of gamma-ray burst (GRB) afterglows to investigate the relationship between the optical and X-ray emission after the prompt phase. We collected the optical data from the literature and determined the shapes of the optical LCs. Then, using previously presented X-ray data we modeled the optical/X-ray SEDs. We studied the SED parameter distributions and compared the optical and X-ray LC slopes and shapes. The optical and X-ray spectra become softer as a function of time while the gas-to-dust ratios of GRBs are higher than the values calculated for the Milky Way and the Large and Magellanic Clouds. For 20% of the GRBs the difference between the optical and X-ray slopes is consistent with 0 or 1=4 within the uncertainties (we did it not consider the steep decay phase), while in the remaining 80% the optical and X-ray afterglows show significantly different temporal behaviors. I...

  18. Investigation of the X-ray Emission of the Large Arcade Flare of 2 March 1993

    CERN Document Server

    Jakimiec, Jerzy

    2013-01-01

    A large arcade flare of 2 March 1993 has been investigated using X-ray observations recorded by the {\\sl Yohkoh} and GOES satellites and the {\\sl Compton Gamma Ray Observatory}. We analyzed quasi-periodicity of the hard-X-ray (HXR) pulses in the flare impulsive phase and found close similarity between the quasi-periodic sequence of the pulses with that observed in another large arcade flare of 2 November 1991. This similarity helped to explain the strong HXR pulses which were recorded at the end of the impulsive phase, as due to an inflow of dense plasma (coming from the chromospheric evaporation) into the acceleration volume inside the cusp. In HXR images a high flaring loop was seen with a triangular cusp structure at the top, where the electrons were efficiently accelerated. The sequence of HXR images allowed us to investigate complicated changes in the precipitation of the accelerated electrons toward the flare footpoints. We have shown that all these impulsive-phase observations can be easily explained i...

  19. Solar Flare Element Abundances from the Solar Assembly for X-rays (SAX) on MESSENGER

    CERN Document Server

    Dennis, B R; Schwartz, R A; Tolbert, A K; Starr, R D; Nittler, L R

    2015-01-01

    X-ray spectra in the range $1.5-8.5$~keV have been analyzed for 526 large flares detected with the Solar Assembly for X-rays (SAX) on the Mercury {\\em MESSENGER} spacecraft between 2007 and 2013. For each flare, the temperature and emission measure of the emitting plasma were determined from the spectrum of the continuum. In addition, with the SAX energy resolution of 0.6 keV (FWHM) at 6~keV, the intensities of the clearly resolved Fe-line complex at 6.7~keV and the Ca-line complex at 3.9~keV were determined, along with those of unresolved line complexes from S, Si, and Ar at lower energies. Comparisons of these line intensities with theoretical spectra allow the abundances of these elements relative to hydrogen to be derived, with uncertainties due to instrument calibration and the unknown temperature distribution of the emitting plasma. While significant deviations are found for the abundances of Fe and Ca from flare to flare, the abundances averaged over all flares are found to be enhanced over photospheri...

  20. Decomposition of the X-ray waveform of soft gamma-ray repeaters during giant flares

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    We have analyzed the observations of SGR 1806-20 and SGR 1900+14 during giant flares made with the Rossi X-ray Timing Explorer.We have studied the pulsating tail after the initial spike and decomposed the pulse waveform into separate components of sub-pulses.We found evidence for phase shifts of those sub-pulses.This is probably due to rapid geometrical changes in the magnetic field of the neutron star during giant flares.The phase shifts could be used to constrain the geometry of the magnetic field.

  1. The WATCH solar X-ray burst catalogue

    DEFF Research Database (Denmark)

    Crosby, N.; Lund, Niels; Vilmer, N.;

    1998-01-01

    The WATCH experiment aboard the GRANAT satellite provides observations of the Sun in the deka-keV range covering the years 1990 through mid-1992. An introduction to the experiment is given followed by an explanation of how the WATCH solar burst catalogue was created. The different parameters listed...

  2. Improved analysis of differential rotation parameters of active longitudes of solar x-ray flares

    International Nuclear Information System (INIS)

    Complete text of publication follows. There is increasing evidence that various manifestations of solar activity are non-axisymmetric and mainly occur in two preferred longitude ranges, so called active longitudes. We have earlier analyzed the longitudinal occurrence of solar X-ray flares observed by GOES satellites using a specially developed dynamic, differentially rotating coordinate system. In this frame, the longitude distribution shows two persistent preferred longitudes separated by about 180 degrees whose strength alternates in time, similarly to the so called flip-flop phenomenon. Here we make an improved statistical analysis to find the globally best fitting values for the parameters describing the differential rotation of active longitudes. We find that the revised analysis gives a more consistent set of parameters, e.g., for the different classes of X-ray flares. Also, the improved parameters yield a higher level of non-axisymmetry for the longitudinal distribution, thus increasing evidence for the existence of active longitudes.

  3. Modelling a Simultaneous Radio/X-Ray Flare from Cyg X-1

    Science.gov (United States)

    Leventis, Konstantinos; Markoff, Sera; Wilsm, Joern; Nowak, Michael A.; Maitra, Dipankar; Pottschmidt, Katja; Pooley, Guy G.; Kreykenbohm, Ingo; Rotschild, Richard E.

    2008-01-01

    The long-term monitoring campaign of Cyg X-1 has provided the detection of the first simultaneous radio/X-ray flare seen from that source. We investigate the physical characteristics of the event in terms of emission from a homogeneous, expanding blob of pair-plasma, superimposed on a baseline flux in both bands. We find that while the radio flare can be reconstructed under various configurations of a cooling blob, continuous (re)acceleration of particles inside the jet is necessary to sustain X-ray emission at the levels implied by the data, for the observed duration. We present major results of the modelling and discuss implications for the role of microquasar jets.

  4. The Flare Activity of SgrA*; New Coordinated mm to X-Ray Observations

    CERN Document Server

    Eckart, A; Bautz, M W; Bower, G C; Brandt, W N; Garmire, G P; Genzel, R; Marrone, D; Moran, J M; Morris, M; Ott, T; Rao, R; Ricker, G R; Roberts, D A; Schödel, R; Straubmeier, C; Trippe, S; Viehmann, T; Yusef-Zadeh, F; Zhao, J H

    2005-01-01

    We report new simultaneous near-infrared/sub-millimeter/X-ray observations of the SgrA* counterpart associated with the massive 3-4x10**6 solar mass black hole at the Galactic Center. The main aim is to investigate the physical processes responsible for the variable emission from SgrA*. The observations have been carried out using the NACO adaptive optics (AO) instrument at the European Southern Observatory's Very Large Telescope and the ACIS-I instrument aboard the Chandra X-ray Observatory as well as the Submillimeter Array SMA on Mauna Kea, Hawaii, and the Very Large Array in New Mexico. We detected one moderately bright flare event in the X-ray domain and 5 events at infrared wavelengths.

  5. X-ray Burst Oscillations: From Flame Spreading to the Cooling Wake

    CERN Document Server

    Mahmoodifar, Simin

    2015-01-01

    Type I X-ray bursts are thermonuclear flashes observed from the surface of accreting neutron stars in Low Mass X-ray Binaries. Oscillations have been observed during the rise and/or decay of some of these X-ray bursts. Those seen during the rise can be well explained by a spreading hot spot model, but to date there haven't been any quantitative studies that consistently track the oscillation amplitude both during the rise and decay (tail) of bursts. Here we compute the light curves and amplitudes of oscillations in X-ray burst models that realistically account for both flame spreading and subsequent cooling. We present results for two such "cooling wake" models, a "canonical" cooling model where each patch on the neutron star surface heats and cools identically, and an "asymmetric" model where parts of the star cool at different rates. We show that while canonical cooling models can generate oscillations in the tails of bursts, they cannot easily produce the highest observed modulation amplitudes. Alternative...

  6. Modeling the X-ray fractional variability spectrum of Active Galactic Nuclei using multiple flares

    OpenAIRE

    Goosmann, R. W.; Dovciak, M.; Karas, V.; Czerny, B.; Mouchet, M.; Ponti, G.

    2007-01-01

    Using Monte-Carlo simulations of X-ray flare distributions across the accretion disk of active galactic nuclei (AGN), we obtain modeling results for the energy-dependent fractional variability amplitude. Referring to previous results of this model, we illustrate the relation between the shape of the point-to-point fractional variability spectrum, F_pp, and the time-integrated spectral energy distribution, F_E. The results confirm that the spectral shape and variability of the iron Kalpha line...

  7. Modeling the X-ray Fractional Variability Spectrum of Active Galactic Nuclei Using Multiple Flares

    Czech Academy of Sciences Publication Activity Database

    Goosmann, René; Dovčiak, Michal; Karas, Vladimír; Czerny, B.; Mouchet, M.; Ponti, G.

    San Francisco : Astronomical Society of the Pacific, 2007 - (Ho, L.; Wang, J.), s. 167-168 ISBN 978-1-58381-307-2. - (ASP Conference Series. 373). [The Central Engine of Active Galactic Nuclei. Xi'an (CN), 16.10.2006-21.10.2006] R&D Projects: GA MŠk(CZ) LC06014 Institutional research plan: CEZ:AV0Z10030501 Keywords : X-rays: galaxies * variability * flares Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  8. Stereoscopic electron spectroscopy of solar hard X-ray flares with a single spacecraft

    OpenAIRE

    Kontar, Eduard P.; John C. Brown

    2006-01-01

    Hard X-ray (HXR) spectroscopy is the most direct method of diagnosing energetic electrons in solar flares. Here we present a technique which allows us to use a single HXR spectrum to determine an effectively stereoscopic electron energy distribution. Considering the Sun's surface to act as a 'Compton mirror' allows us to look at emitting electrons also from behind the source, providing vital information on downward-propagating particles. Using this technique we determine simultaneously the el...

  9. Kappa distribution and hard X-ray emission of solar flares

    Czech Academy of Sciences Publication Activity Database

    Kašparová, Jana; Karlický, Marian

    2009-01-01

    Roč. 497, č. 3 (2009), L13-L16. ISSN 0004-6361 R&D Projects: GA ČR GP205/06/P135; GA ČR GA205/09/1705; GA AV ČR IAA300030701 Institutional research plan: CEZ:AV0Z10030501 Keywords : solar flares * X-rays * gamma rays Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.179, year: 2009

  10. SAS-3 observations of an X-ray flare from Cygnus X-1

    Science.gov (United States)

    Canizares, C. R.; Bradt, H.; Buff, J.; Laufer, B.

    1976-01-01

    Preliminary results are presented for the SAS-3 observation of an X-ray flare from Cygnus X-1. The 1.5 to 6 keV intensity rose by a factor of four and exhibited variability on several time scales from seconds to hours. The 6 to 15 keV intensity showed less activity. The event is similar to that observed by ANS and Ariel 5, but lasted less than two weeks.

  11. A recent strong X-ray flaring activity of 1ES 1959+650 with possibly less efficient stochastic acceleration

    Science.gov (United States)

    Kapanadze, B.; Dorner, D.; Vercellone, S.; Romano, P.; Kapanadze, S.; Mdzinarishvili, T.

    2016-03-01

    We present an X-ray flaring activity of 1ES 1959+650 in 2015 August - 2016 January, which was the most powerful and prolonged during the 10.75 yr period since the start of its monitoring with X-ray Telescope onboard Swift. A new highest historical 0.3 - 10 keV count rate was recorded three times that makes this object the third BL Lacertae source exceeding the level of 20 cts s-1. Along with the overall variability by a factor of 5.7, this epoch was characterized by fast X-ray flares by a factor of 2.0 - 3.1, accompanied with an extreme spectral variability. The source also shows a simultaneous flaring activity in the optical - UV and 0.3 - 100 GeV bands, although a fast γ-ray flare without significant optical - X-ray counterparts is also found. In contrast to the X-ray flares in the previous years, the stochastic acceleration seems be less important for the electrons responsible for producing X-ray emission during this flare that challenges the earlier suggestion that the electrons in the jets of TeV-detected BL Lacertae objects should undergo an efficient stochastic acceleration resulting in a lower X-ray spectral curvature.

  12. GRB 121027A: long-lasting, energetic X-ray flares and clues to radiation mechanism and progenitor star

    CERN Document Server

    Peng, Fang-kun; Xi, Shao-Qiang; Wang, Xiang-Gao; Lu, Rui-Jing; Liang, En-Wei; Zhang, Bing

    2013-01-01

    GRB 121027A is un-usual with its extremely long-lasting, energetic X-ray flares. The total energy release in X-ray flares is about one order of magnitude higher than prompt gamma-rays, making it special from most long GRBs. We show that while the prompt gamma-ray emission satisfies the empirical E_{iso}-E_{p} relation of typical long GRBs, the X-ray flares, whose spectra can be fit with a cutoff-power-law model with well-constrained E_p, significantly deviate from such a relation. Nonetheless, a time-resolved spectral analysis of X-ray flares suggest that the X-ray emission is consistent with the L_{iso}-E_{p} relation of long GRBs. We constrain the minimum Lorentz factor of the X-ray flares to be ~14, which is consistent with the Gamma-L_{iso} relation. Our results imply that prompt gamma-ray emission and late X-ray flares share the similar radiation mechanism, but originate from the outflows with different Lorentz factors. We search for similar GRBs from the Swift GRB archives, and find that the z=6.29 GRB ...

  13. A recent strong X-ray flaring activity of 1ES 1959+650 with possibly less efficient stochastic acceleration

    Science.gov (United States)

    Kapanadze, B.; Dorner, D.; Vercellone, S.; Romano, P.; Kapanadze, S.; Mdzinarishvili, T.

    2016-09-01

    We present an X-ray flaring activity of 1ES 1959+650 in 2015 August-2016 January, which was the most powerful and prolonged during the 10.75 yr period since the start of its monitoring with X-ray Telescope onboard Swift. A new highest historical 0.3-10 keV count rate was recorded three times that makes this object the third BL Lacertae source exceeding the level of 20 counts s-1. Along with the overall variability by a factor of 5.7, this epoch was characterized by fast X-ray flares by a factor of 2.0-3.1, accompanied with an extreme spectral variability. The source also shows a simultaneous flaring activity in the optical - UV and 0.3-100 GeV bands, although a fast γ-ray flare without significant optical - X-ray counterparts is also found. In contrast to the X-ray flares in the previous years, the stochastic acceleration seems be less important for the electrons responsible for producing X-ray emission during this flare that challenges the earlier suggestion that the electrons in the jets of TeV-detected BL Lacertae objects should undergo an efficient stochastic acceleration resulting in a lower X-ray spectral curvature.

  14. Spatio-temporal dynamics of sources of hard X-ray pulsations in solar flares

    CERN Document Server

    Kuznetsov, S A; Morgachev, A S; Struminsky, A B

    2016-01-01

    We present systematic analysis of spatio-temporal evolution of sources of hard X-ray (HXR) pulsations in solar flares. We concentrate on disk flares whose impulsive phase are accompanied by a series of more than three peaks (pulsations) of HXR emission detected in the RHESSI 50-100 keV channel with 4-second cadence. 29 such flares observed from February 2002 to June 2015 with time differences between successive peaks of 8-270 s are studied. The main observational result is that sources of HXR pulsations in all flares are not stationary, they demonstrate apparent displacements from pulsation to pulsation. The flares can be subdivided into two groups depending on character of dynamics of HXR sources. The group-1 consists of 16 flares (55%) with systematic dynamics of HXR sources from pulsation to pulsation with respect to a magnetic polarity inversion line (MPIL), which has simple extended trace on the photosphere. The group-2 consists of 13 flares (45%) with more chaotic displacements of HXR sources with respe...

  15. Hydrogen-Triggered Type I X-ray Bursts in a Two-Zone Model

    OpenAIRE

    Cooper, Randall L.; Narayan, Ramesh

    2007-01-01

    We use the two-zone model of Cooper & Narayan to study the onset and time evolution of hydrogen-triggered type I X-ray bursts on accreting neutron stars. At the lowest accretion rates, thermally unstable hydrogen burning ignites helium as well and produces a mixed hydrogen and helium burst. For somewhat higher accretion rates, thermally unstable hydrogen burning does not ignite helium and thus triggers only a weak hydrogen flash. The peak luminosities of weak hydrogen flashes are typically mu...

  16. The Energetics of Wight-light Flares Observed in Visible Continuum and Hard X-ray

    Science.gov (United States)

    Huang, Nengyi; Xu, Yan; Wang, Haimin

    2016-05-01

    White-light (WL) flares have been observed and studied more than a century since the first discovery. However, some fundamental physics behind the brilliant emission remains highly controversial. One of the important facts in addressing the flare energetics is the spatial-temporal correlation between the white-light emission and the hard X-ray radiation, presumably suggesting that the energetic electrons are the energy sources. In this study, we present a statistical analysis of 26 strong flares (>M5) observed simultaneously by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Among these events, WL emission was detected by SDO/HMI in 13 flares, associated with HXR emission. To quantitatively describe the strength of WL emission, equivalent area is defined as the integrated contrast enhancement over the entire flaring area. Our results show that the equivalent area is inversely proportional to the HXR power index, indicating that stronger WL emission tends to be associated with larger population of high energy electrons. Furthermore, we studied an M6.6 flare on 2015 June 22 observed by BBSO’s New Solar Telescope (NST), showing WL emission in TiO continuum (705.7 nm), but no detectable WL signal from SDO/HMI. The power index- equivalent area relationship of this flare matches the trend found in the statistical analysis. In addition, for the other group of 13 flares without detectable WL emission, the HXR spectra are softer (larger power index) than those flares with WL emission, especially for the X-class flares in this group.

  17. The X-ray Telescope for the SWIFT Gamma-Ray Burst Mission

    International Nuclear Information System (INIS)

    The X-ray Telescope (XRT) for the SWIFT mission, built by the international consortium from Pennsylvania State University (United States), University of Leicester (UK) and Osservatorio Astronomico di Brera (Italy), is already installed on the SWIFT spacecraft. The XRT has two key functions on SWIFT; to determine locations of GRBs to better than 5 arc seconds within 100 seconds of initial detection of a burst and to measure spectra and light curves of the X-ray afterglow over around four orders of magnitude of decay in the afterglow intensity. This paper summarises the XRT performance, operating modes and sensitivity for the detection of prompt and extended X-ray afterglows from gamma-ray bursts. The performance characteristics have been determined from data taken during the ground calibration campaign at MPE's Panter facility in September 2002

  18. IMPULSIVE PHASE CORONAL HARD X-RAY SOURCES IN AN X3.9 CLASS SOLAR FLARE

    International Nuclear Information System (INIS)

    We present the analysis of a pair of unusually energetic coronal hard X-ray (HXR) sources detected by the Reuven Ramaty High Energy Solar Spectroscopic Imager during the impulsive phase of an X3.9 class solar flare on 2003 November 3, which simultaneously shows two intense footpoint (FP) sources. A distinct loop top (LT) coronal source is detected up to ∼150 keV and a second (upper) coronal source up to ∼80 keV. These photon energies, which were not fully investigated in earlier analysis of this flare, are much higher than commonly observed in coronal sources and pose grave modeling challenges. The LT source in general appears higher in altitude with increasing energy and exhibits a more limited motion compared to the expansion of the thermal loop. The high-energy LT source shows an impulsive time profile and its nonthermal power-law spectrum exhibits soft-hard-soft evolution during the impulsive phase, similar to the FP sources. The upper coronal source exhibits an opposite spatial gradient and a similar spectral slope compared to the LT source. These properties are consistent with the model of stochastic acceleration of electrons by plasma waves or turbulence. However, the LT and FP spectral index difference (varying from ∼0 to 1) is much smaller than commonly measured and than that expected from a simple stochastic acceleration model. Additional confinement or trapping mechanisms of high-energy electrons in the corona are required. Comprehensive modeling including both kinetic effects and the macroscopic flare structure may shed light on this behavior. These results highlight the importance of imaging spectroscopic observations of the LT and FP sources up to high energies in understanding electron acceleration in solar flares. Finally, we show that the electrons producing the upper coronal HXR source may very likely be responsible for the type III radio bursts at the decimetric/metric wavelength observed during the impulsive phase of this flare.

  19. Differential emission measure analysis of hot-flare plasma from solar-maximum mission X-ray data

    NARCIS (Netherlands)

    Schrijver, J.; Jakimiec, J.; Sylwester, J.; Lemen, J.R.; Mewe, R.; Bentley, R.D.; Fludra, A.; Sylwester, B.

    1984-01-01

    We have investigated differential emission measure (DEM) distribution of hot flare plasma (T>10 MK) using SMM X-ray data from Bent Crystal Spectrometer (BCS) and Hard X-ray Imaging Spectrometer (HXIS). We have found that the analysis provide a very sensitive test of consistency of observational data

  20. Accretion disk signatures in Type I X-ray Bursts: prospects for future missions

    CERN Document Server

    Keek, L; Ballantyne, D R

    2016-01-01

    Type I X-ray bursts and superbursts from accreting neutron stars illuminate the accretion disk and produce a reflection signal that evolves as the burst fades. Examining the evolution of reflection features in the spectra will give insight into the burst-disk interaction, a potentially powerful probe of accretion disk physics. At present, reflection has been observed during only two bursts of exceptional duration. We investigate the detectability of reflection signatures with four of the latest well-studied X-ray observatory concepts: Hitomi, NICER, Athena, and LOFT. Burst spectra are modeled for different values for the flux, temperature, and the disk ionization parameter, which are representative for most known bursts and sources. The effective area and through-put of a Hitomi-like telescope are insufficient for characterizing burst reflection features. NICER and Athena will detect reflection signatures in Type I bursts with peak fluxes $\\ge 10^{-7.5}$ erg cm$^{-2}$ s$^{-1}$, and also effectively constrain ...

  1. THREE-DIMENSIONAL RADIO AND X-RAY MODELING AND DATA ANALYSIS SOFTWARE: REVEALING FLARE COMPLEXITY

    International Nuclear Information System (INIS)

    Many problems in solar physics require analysis of imaging data obtained in multiple wavelength domains with differing spatial resolution in a framework supplied by advanced three-dimensional (3D) physical models. To facilitate this goal, we have undertaken a major enhancement of our IDL-based simulation tools developed earlier for modeling microwave and X-ray emission. The enhanced software architecture allows the user to (1) import photospheric magnetic field maps and perform magnetic field extrapolations to generate 3D magnetic field models; (2) investigate the magnetic topology by interactively creating field lines and associated flux tubes; (3) populate the flux tubes with user-defined nonuniform thermal plasma and anisotropic, nonuniform, nonthermal electron distributions; (4) investigate the spatial and spectral properties of radio and X-ray emission calculated from the model; and (5) compare the model-derived images and spectra with observational data. The package integrates shared-object libraries containing fast gyrosynchrotron emission codes, IDL-based soft and hard X-ray codes, and potential and linear force-free field extrapolation routines. The package accepts user-defined radiation and magnetic field extrapolation plug-ins. We use this tool to analyze a relatively simple single-loop flare and use the model to constrain the magnetic 3D structure and spatial distribution of the fast electrons inside this loop. We iteratively compute multi-frequency microwave and multi-energy X-ray images from realistic magnetic flux tubes obtained from pre-flare extrapolations, and compare them with imaging data obtained by SDO, NoRH, and RHESSI. We use this event to illustrate the tool's use for the general interpretation of solar flares to address disparate problems in solar physics

  2. Three-dimensional Radio and X-Ray Modeling and Data Analysis Software: Revealing Flare Complexity

    Science.gov (United States)

    Nita, Gelu M.; Fleishman, Gregory D.; Kuznetsov, Alexey A.; Kontar, Eduard P.; Gary, Dale E.

    2015-02-01

    Many problems in solar physics require analysis of imaging data obtained in multiple wavelength domains with differing spatial resolution in a framework supplied by advanced three-dimensional (3D) physical models. To facilitate this goal, we have undertaken a major enhancement of our IDL-based simulation tools developed earlier for modeling microwave and X-ray emission. The enhanced software architecture allows the user to (1) import photospheric magnetic field maps and perform magnetic field extrapolations to generate 3D magnetic field models; (2) investigate the magnetic topology by interactively creating field lines and associated flux tubes; (3) populate the flux tubes with user-defined nonuniform thermal plasma and anisotropic, nonuniform, nonthermal electron distributions; (4) investigate the spatial and spectral properties of radio and X-ray emission calculated from the model; and (5) compare the model-derived images and spectra with observational data. The package integrates shared-object libraries containing fast gyrosynchrotron emission codes, IDL-based soft and hard X-ray codes, and potential and linear force-free field extrapolation routines. The package accepts user-defined radiation and magnetic field extrapolation plug-ins. We use this tool to analyze a relatively simple single-loop flare and use the model to constrain the magnetic 3D structure and spatial distribution of the fast electrons inside this loop. We iteratively compute multi-frequency microwave and multi-energy X-ray images from realistic magnetic flux tubes obtained from pre-flare extrapolations, and compare them with imaging data obtained by SDO, NoRH, and RHESSI. We use this event to illustrate the tool's use for the general interpretation of solar flares to address disparate problems in solar physics.

  3. THREE-DIMENSIONAL RADIO AND X-RAY MODELING AND DATA ANALYSIS SOFTWARE: REVEALING FLARE COMPLEXITY

    Energy Technology Data Exchange (ETDEWEB)

    Nita, Gelu M.; Fleishman, Gregory D.; Gary, Dale E. [Center For Solar-Terrestrial Research, New Jersey Institute of Technology, Newark, NJ 07102 (United States); Kuznetsov, Alexey A. [Institute of Solar-Terrestrial Physics, Irkutsk 664033 (Russian Federation); Kontar, Eduard P. [School of Physics and Astronomy, The University of Glasgow, Glasgow G12 8QQ (United Kingdom)

    2015-02-01

    Many problems in solar physics require analysis of imaging data obtained in multiple wavelength domains with differing spatial resolution in a framework supplied by advanced three-dimensional (3D) physical models. To facilitate this goal, we have undertaken a major enhancement of our IDL-based simulation tools developed earlier for modeling microwave and X-ray emission. The enhanced software architecture allows the user to (1) import photospheric magnetic field maps and perform magnetic field extrapolations to generate 3D magnetic field models; (2) investigate the magnetic topology by interactively creating field lines and associated flux tubes; (3) populate the flux tubes with user-defined nonuniform thermal plasma and anisotropic, nonuniform, nonthermal electron distributions; (4) investigate the spatial and spectral properties of radio and X-ray emission calculated from the model; and (5) compare the model-derived images and spectra with observational data. The package integrates shared-object libraries containing fast gyrosynchrotron emission codes, IDL-based soft and hard X-ray codes, and potential and linear force-free field extrapolation routines. The package accepts user-defined radiation and magnetic field extrapolation plug-ins. We use this tool to analyze a relatively simple single-loop flare and use the model to constrain the magnetic 3D structure and spatial distribution of the fast electrons inside this loop. We iteratively compute multi-frequency microwave and multi-energy X-ray images from realistic magnetic flux tubes obtained from pre-flare extrapolations, and compare them with imaging data obtained by SDO, NoRH, and RHESSI. We use this event to illustrate the tool's use for the general interpretation of solar flares to address disparate problems in solar physics.

  4. THE RELATIONSHIP BETWEEN X-RAY LUMINOSITY AND MAJOR FLARE LAUNCHING IN GRS 1915+105

    Energy Technology Data Exchange (ETDEWEB)

    Punsly, Brian [1415 Granvia Altamira, Palos Verdes Estates, CA 90274 (United States); Rodriguez, Jerome, E-mail: brian.punsly1@verizon.net, E-mail: brian.punsly@comdev-usa.com [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, IRFU SAp, F-91191 Gif-sur-Yvette (France)

    2013-02-20

    We perform the most detailed analysis to date of the X-ray state of the Galactic black hole candidate GRS 1915+105 just prior to (0-4 hr) and during the brief (1-7 hr) ejection of major (superluminal) radio flares. A very strong model independent correlation is found between the 1.2 keV-12 keV X-ray flux 0-4 hr before flare ejections with the peak optically thin 2.3 GHz emission of the flares. This suggests a direct physical connection between the energy in the ejection and the luminosity of the accretion flow preceding the ejection. In order to quantify this concept, we develop techniques to estimate the intrinsic (unabsorbed) X-ray luminosity, L {sub intrinsic}, from RXTE All Sky Monitor data and to implement known methods to estimate the time-averaged power required to launch the radio emitting plasmoids, Q (sometimes called jet power). We find that the distribution of intrinsic luminosity from 1.2 keV-50 keV, L {sub intrinsic} (1.2-50), is systematically elevated just before ejections compared to arbitrary times when there are no major ejections. The estimated Q is strongly correlated with L {sub intrinsic} (1.2-50) 0-4 hr before the ejection, the increase in L {sub intrinsic} (1.2-50) in the hours preceding the ejection and the time-averaged L {sub intrinsic} (1.2-50) during the flare rise. Furthermore, the total time-averaged power during the ejection (Q + the time average of L {sub intrinsic} (1.2-50) during ejection) is strongly correlated with L {sub intrinsic} (1.2-50) just before launch with near equality if the distance to the source is Almost-Equal-To 10.5 kpc.

  5. THE RELATIONSHIP BETWEEN X-RAY LUMINOSITY AND MAJOR FLARE LAUNCHING IN GRS 1915+105

    International Nuclear Information System (INIS)

    We perform the most detailed analysis to date of the X-ray state of the Galactic black hole candidate GRS 1915+105 just prior to (0-4 hr) and during the brief (1-7 hr) ejection of major (superluminal) radio flares. A very strong model independent correlation is found between the 1.2 keV-12 keV X-ray flux 0-4 hr before flare ejections with the peak optically thin 2.3 GHz emission of the flares. This suggests a direct physical connection between the energy in the ejection and the luminosity of the accretion flow preceding the ejection. In order to quantify this concept, we develop techniques to estimate the intrinsic (unabsorbed) X-ray luminosity, L intrinsic, from RXTE All Sky Monitor data and to implement known methods to estimate the time-averaged power required to launch the radio emitting plasmoids, Q (sometimes called jet power). We find that the distribution of intrinsic luminosity from 1.2 keV-50 keV, L intrinsic (1.2-50), is systematically elevated just before ejections compared to arbitrary times when there are no major ejections. The estimated Q is strongly correlated with L intrinsic (1.2-50) 0-4 hr before the ejection, the increase in L intrinsic (1.2-50) in the hours preceding the ejection and the time-averaged L intrinsic (1.2-50) during the flare rise. Furthermore, the total time-averaged power during the ejection (Q + the time average of L intrinsic (1.2-50) during ejection) is strongly correlated with L intrinsic (1.2-50) just before launch with near equality if the distance to the source is ≈10.5 kpc.

  6. Modeling Flare Hard X-ray Emission from Electrons in Contracting Magnetic Islands

    Science.gov (United States)

    Guidoni, Silvina E.; Allred, Joel C.; Alaoui, Meriem; Holman, Gordon D.; DeVore, C. Richard; Karpen, Judith T.

    2016-05-01

    The mechanism that accelerates particles to the energies required to produce the observed impulsive hard X-ray emission in solar flares is not well understood. It is generally accepted that this emission is produced by a non-thermal beam of electrons that collides with the ambient ions as the beam propagates from the top of a flare loop to its footpoints. Most current models that investigate this transport assume an injected beam with an initial energy spectrum inferred from observed hard X-ray spectra, usually a power law with a low-energy cutoff. In our previous work (Guidoni et al. 2016), we proposed an analytical method to estimate particle energy gain in contracting, large-scale, 2.5-dimensional magnetic islands, based on a kinetic model by Drake et al. (2010). We applied this method to sunward-moving islands formed high in the corona during fast reconnection in a simulated eruptive flare. The overarching purpose of the present work is to test this proposed acceleration model by estimating the hard X-ray flux resulting from its predicted accelerated-particle distribution functions. To do so, we have coupled our model to a unified computational framework that simulates the propagation of an injected beam as it deposits energy and momentum along its way (Allred et al. 2015). This framework includes the effects of radiative transfer and return currents, necessary to estimate flare emission that can be compared directly to observations. We will present preliminary results of the coupling between these models.

  7. Anisotropy of X-ray bursts from neutron stars with concave accretion disks

    CERN Document Server

    He, Chong-Chong

    2015-01-01

    Emission from neutron stars and accretion disks in low-mass X-ray binaries is not isotropic. The non-spherical shape of the disk as well as blocking of the neutron star by the disk and vice versa cause the observed flux to depend on the inclination angle of the disk with respect to the line of sight. This is of special importance for the interpretation of Type I X-ray bursts, which are powered by the thermonuclear burning of matter accreted onto the neutron star. Because part of the X-ray burst is reflected off the disk, the observed burst flux depends on the anisotropies for both direct emission from the neutron star and reflection off the disk. This influences measurements of source distance, mass accretion rate, and constraints on the neutron star equation of state. Previous studies made predictions of the anisotropy factor for the total burst flux, assuming a geometrically flat disk. Recently, detailed observations of two exceptionally long bursts (so-called superbursts) allowed for the first time for the...

  8. Data Selection Criteria for Spectroscopic Measurements of Neutron Star Radii with X-ray Bursts

    CERN Document Server

    Ozel, Feryal; Guver, Tolga

    2015-01-01

    Data selection and the determination of systematic uncertainties in the spectroscopic measurements of neutron star radii from thermonuclear X-ray bursts have been the subject of numerous recent studies. In one approach, the uncertainties and outliers were determined by a data-driven Bayesian mixture model, whereas in a second approach, data selection was performed by requiring that the observations follow theoretical expectations. We show here that, due to inherent limitations in the data, the theoretically expected trends are not discernible in the majority of X-ray bursts even if they are present. Therefore, the proposed theoretical selection criteria are not practical with the current data for distinguishing clean data sets from outliers. Furthermore, when the data limitations are not taken into account, the theoretically motivated approach selects a small subset of bursts with properties that are in fact inconsistent with the underlying assumptions of the method. We conclude that the data-driven selection...

  9. High-Resolution X-Ray Spectroscopy of the Bursting Pulsar GRO J1744-28

    CERN Document Server

    Degenaar, N; Harrison, F A; Kennea, J A; Kouveliotou, C; Younes, G

    2014-01-01

    The bursting pulsar GRO J1744-28 is a Galactic low-mass X-ray binary that distinguishes itself by displaying type-II X-ray bursts: brief, bright flashes of X-ray emission that likely arise from spasmodic accretion. Combined with its coherent 2.1 Hz X-ray pulsations and relatively high estimated magnetic field, it is a particularly interesting source to study the physics of accretion flows around neutron stars. Here we report on Chandra/HETG observations obtained near the peak of its bright 2014 accretion outburst. Spectral analysis suggests the presence of a broad iron emission line centered at E_l ~ 6.7 keV. Fits with a disk reflection model yield an inclination angle of i ~ 52 degrees and an inner disk radius of R_in ~ 85 GM/c^2, which is much further out than typically found for neutron star low-mass X-ray binaries. Assuming that the disk is truncated at the magnetospheric radius of the neutron star, we estimate a magnetic field strength of B ~ (2-6)E10 G. Furthermore, we identify an absorption feature nea...

  10. Spatial distribution of X-ray bursts in triggered lightning experiments

    Science.gov (United States)

    Bakhtiari, M.; Saleh, Z.; Dwyer, J.; Rassoul, H.; Uman, M.; Howard, J.

    2007-12-01

    During rocket-triggered lightning experiments, it has been observed that the dart leader phase is accompanied by bursts of X-rays. These experiments were carried out at the University of Florida/Florida Tech International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, FL. We report here the analysis of a sequence of X-ray bursts that occurred during the dart leader of a lightning flash triggered on July 31, 2007. The measurement of the penetrating X-ray photons was done with the Thunderstorm Energetic Radiation Array (TERA), which consists of more than 40 NaI detectors systematically distributed at various distances within 500 m from the launching tower. The integrated observed X-ray intensity at ground level over a short time prior to the return stroke shows a strong radial decay. On the other hand, the integrated radial X-ray distribution is rather flat at earlier times. The measurements are compared with simulations that include the physics of photon propagation through air. The results are consistent with a source that travels from high altitude to near ground level (the top of the rocket launching tower).

  11. Relationship of type III radio bursts with quasi-periodic pulsations in a solar flare

    CERN Document Server

    Kupriyanova, E G; Reid, H A S; Myagkova, I N

    2016-01-01

    We studied a solar flare with pronounced quasi-periodic pulsations detected in the microwave, X-ray, and radio bands. We used the methods of correlation, Fourier, and wavelet analyses to examine the temporal fine structures and relationships between the time profiles in each wave band. We found that the time profiles of the microwaves, hard X-rays and type III radio bursts vary quasi-periodically with the common period of 40-50 s. The average amplitude of the variations is high, above 30% of the background flux level and reaching 80% after the flare maximum. We did not find the periodicity in either the thermal X-ray flux component or source size dynamics. Our findings indicate that the detected periodicity is likely to be associated with periodic dynamics in the injection of non-thermal electrons, that can be produced by periodic modulation of magnetic reconnection.

  12. Binary phase correlated X-ray intensity variations and flaring activity in the RS CVn binary HR 1099

    Science.gov (United States)

    Agrawal, P. C.; Vaidya, J.

    1988-01-01

    The monitor proportional counter and the imaging proportional counter of the Einstein Observatory were used to observe the X-ray variability of the RS CVn binary HR 1099. The X-ray intensity is found to vary with the 2.837-day period of the binary. An intense X-ray flare was noted on February 17, 1980. The present results are explained using a star spot model, and it is suggested that the flare heated plasma cools either mainly by radiation or equally by conduction and radiation.

  13. Discovery of a high confidence soft lag from an X-ray flare of Markarian 421

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    We present the X-ray variability properties of the X-ray and TeV bright blazar Mrk 421 with a-60 ks long XMM-Newton observation performed on November 9-10,2005.The source experienced a pronounced flare,of which the inter-band time lags were determined with a very high confidence level.The soft(0.6-0.8 keV) X-ray variations lagged the hard(4-10 keV) ones by 1.09+0.11-0.12 ks,and the soft lag increases with increasing difference in the photon energy.The energy-dependent soft lags can be well fitted with the difference of the energy-dependent cooling timescales of the relativistic electron distribution responsible for the observed X-ray emission,which constrains the magnetic field strength and Doppler factor of the emitting region to be Bδ 1/3-1.78 Gauss.

  14. X-ray Spectral Diagnostics of $\\gamma$-Ray Burst Environments

    CERN Document Server

    Paerels, F B S; Heise, J; Liedahl, D A; Paerels, Frits; Kuulkers, Erik; Heise, John; Liedahl, Duane A.

    2000-01-01

    Recently, the detection of discrete features in the X-ray afterglow spectra of GRB970508 and GRB970828 was reported. The most natural interpretation of these features is that they are redshifted Fe K emission complexes. The identification of the line emission mechanism has drastic implications for the inferred mass of radiating material, end hence the nature of the burst site. X-ray spectroscopy provides a direct observational constraint on these properties of gamma-ray bursters. We briefly discuss how these constraints arise, in the context of an application to the spectrum of GRB970508.

  15. Millihertz Oscillation Frequency Drift Predicts the Occurrence of Type I X-ray Bursts

    CERN Document Server

    Altamirano, D; Wijnandsm, R; Cumming, A

    2007-01-01

    Millihertz quasi-periodic oscillations reported in three neutron-star low mass X-ray binaries have been suggested to be a mode of marginally stable nuclear burning on the neutron star surface. In this Letter, we show that close to the transition between the island and the banana state, 4U~1636--53 shows mHz QPOs whose frequency systematically decreases with time until the oscillations disappear and a Type I X-ray burst occurs. There is a strong correlation between the QPO frequency $\

  16. Solar flares X-ray polarimetry in a wide energy band

    Science.gov (United States)

    Fabiani, Sergio; Campana, Riccardo; Costa, Enrico; Muleri, Fabio; Bellazzini, Ronaldo; Soffitta, Paolo; Del Monte, Ettore; Rubini, Alda

    2012-07-01

    Polarimetry of solar flares X-ray emission is an additional tool for investigating particles dynamics within the solar atmosphere. Accelerated electrons by magnetic reconnection in the corona produce bremsstrahlung radiation as primary emission in the footpoints of a solar flare which has moreover the possibility to be Compton backscattered resulting in albedo emission. Non-thermal bremsstrahlung emission is expected to be a significant above 15 keV and highly polarized. The albedo component peaks between 20 and 50 keV, its polarization properties depend on the Compton scattering angle. Such a diffusion modifies the spectrum and the polarization of the primary bremsstrahlung emission. Hard X-ray polarimetry, spectroscopy and imaging are therefore necessary to disentangle and modeling the different components in a solar flare. We present a non imaging Compton polarimeter sensitive from 20 keV designed as a single scattering unit surrounded by absorbers of high atomic number. A photelectric polarimeter based on the Gas Pixel Detector technology sensitive in the 15-35 keV energy band can be coupled for imaging.

  17. Measurements of electron anisotropy in solar flares using albedo with RHESSI X-ray data

    CERN Document Server

    Dickson, Ewan Cameron Mackenzie

    2012-01-01

    The angular distribution of electrons accelerated in solar flares is a key parameter in the understanding of the acceleration and propagation mechanisms that occur there. However, the anisotropy of energetic electrons is still a poorly known quantity, with observational studies producing evidence for an isotropic distribution and theoretical models mainly considering the strongly beamed case. We use the effect of photospheric albedo to infer the pitch angle distribution of X-ray emitting electrons using Hard X-ray data from RHESSI. A bi-directional approximation is applied and a regularized inversion is performed for eight large flare events to deduce the electron spectra in both downward (towards the photosphere) and upward (away from the photosphere) directions. The electron spectra and the electron anisotropy ratios are calculated for broad energy range from about 10 and up to ~ 300 keV near the peak of the flares. The variation of electron anisotropy over short periods of time intervals lasting 4, 8 and 1...

  18. Wide field X-ray telescopes: Detecting X-ray transients/afterglows related to gamma ray bursts

    International Nuclear Information System (INIS)

    The recent discovery of X-ray afterglows of GRBs opens the possibility of analyses of GRBs by their X-ray detections. However, imaging X-ray telescopes in current use mostly have limited field of view. Alternative X-ray optics geometries achieving very large fields of view have been theoretically suggested in the 70ies but not constructed and used so far. We review the geometries and basic properties of the wide-field X-ray optical systems based on one- and two-dimensional lobster-eye geometry and suggest technologies for their development and construction. First results of the development of double replicated X-ray reflecting flats for use in one-dimensional X-ray optics of lobster eye type are presented and discussed. Optimum strategy for locating GRBs upon their X-ray counterparts is also presented and discussed

  19. A search for thermal X-ray signatures in Gamma-Ray Bursts I: Swift bursts with optical supernovae

    CERN Document Server

    Starling, R L C; Pe'er, A; Beardmore, A P; Osborne, J P

    2012-01-01

    The X-ray spectra of Gamma-Ray Bursts can generally be described by an absorbed power law. The landmark discovery of thermal X-ray emission in addition to the power law in the unusual GRB 060218, followed by a similar discovery in GRB 100316D, showed that during the first thousand seconds after trigger the soft X-ray spectra can be complex. Both the origin and prevalence of such spectral components still evades understanding, particularly after the discovery of thermal X-ray emission in the classical GRB 090618. Possibly most importantly, these three objects are all associated with optical supernovae, begging the question of whether the thermal X-ray components could be a result of the GRB-SN connection, possibly in the shock breakout. We therefore performed a search for blackbody components in the early Swift X-ray spectra of 11 GRBs that have or may have associated optical supernovae, accurately recovering the thermal components reported in the literature for GRBs 060218, 090618 and 100316D. We present the ...

  20. Hard X-Ray Imaging of Individual Spectral Components in Solar Flares

    CERN Document Server

    Caspi, Amir; McTiernan, James M; Krucker, Säm

    2015-01-01

    We present a new analytical technique, combining Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) high-resolution imaging and spectroscopic observations, to visualize solar flare emission as a function of spectral component (e.g., isothermal temperature) rather than energy. This computationally inexpensive technique is applicable to all spatially-invariant spectral forms and is useful for visualizing spectroscopically-determined individual sources and placing them in context, e.g., comparing multiple isothermal sources with nonthermal emission locations. For example, while extreme ultraviolet images can usually be closely identified with narrow temperature ranges, due to the emission being primarily from spectral lines of specific ion species, X-ray images are dominated by continuum emission and therefore have a broad temperature response, making it difficult to identify sources of specific temperatures regardless of the energy band of the image. We combine RHESSI calibrated X-ray visibilities wi...

  1. RECONCILIATION OF WAITING TIME STATISTICS OF SOLAR FLARES OBSERVED IN HARD X-RAYS

    International Nuclear Information System (INIS)

    We study the waiting time distributions of solar flares observed in hard X-rays with ISEE-3/ICE, HXRBS/SMM, WATCH/GRANAT, BATSE/CGRO, and RHESSI. Although discordant results and interpretations have been published earlier, based on relatively small ranges (-3-103 hr), can be reconciled with a single distribution function, N(Δt) ∝ λ0(1 + λ0Δt)-2, which has a power-law slope of p ∼ 2.0 at large waiting times (Δt ∼ 1-1000 hr) and flattens out at short waiting times Δt ∼0 = 1/λ0. We find a consistent breakpoint at Δt 0 = 1/λ0 = 0.80 ± 0.14 hr from the WATCH, HXRBS, BATSE, and RHESSI data. The distribution of waiting times is invariant for sampling with different flux thresholds, while the mean waiting time scales reciprocically with the number of detected events, Δt 0 ∝ 1/n det. This waiting time distribution can be modeled with a nonstationary Poisson process with a flare rate λ = 1/Δt that varies as f(λ) ∝ λ-1exp - (λ/λ0). This flare rate distribution requires a highly intermittent flare productivity in short clusters with high rates, separated by relatively long quiescent intervals with very low flare rates.

  2. HARD X-RAY AND MICROWAVE EMISSIONS FROM SOLAR FLARES WITH HARD SPECTRAL INDICES

    International Nuclear Information System (INIS)

    We analyze 10 flare events that radiate intense hard X-ray (HXR) emission with significant photons over 300 keV to verify that the electrons that have a common origin of acceleration mechanism and energy power-law distribution with solar flares emit HXRs and microwaves. Most of these events have the following characteristics. HXRs emanate from the footpoints of flare loops, while microwaves emanate from the tops of flare loops. The time profiles of the microwave emission show delays of peak with respect to those of the corresponding HXR emission. The spectral indices of microwave emissions show gradual hardening in all events, while the spectral indices of the corresponding HXR emissions are roughly constant in most of the events, though rather rapid hardening is simultaneously observed in some for both indices during the onset time and the peak time. These characteristics suggest that the microwave emission emanates from the trapped electrons. Then, taking into account the role of the trapping of electrons for the microwave emission, we compare the observed microwave spectra with the model spectra calculated by a gyrosynchrotron code. As a result, we successfully reproduce the eight microwave spectra. From this result, we conclude that the electrons that have a common acceleration and a common energy distribution with solar flares emit both HXR and microwave emissions in the eight events, though microwave emission is contributed to by electrons with much higher energy than HXR emission.

  3. Nearly Coherent Oscillations in Type I X-Ray Bursts from KS 1731-260

    CERN Document Server

    Muno, M P; Morgan, E H; Bildsten, L; Muno, Michael P.; Fox, Derek W.; Morgan, Edward H.; Bildsten, Lars

    2000-01-01

    We present an analysis of the nine type I X-ray bursts that were observed from KS 1731-260 with RXTE. We find that the bursts divide naturally into two populations: ``fast bursts'' occur on the Banana Branch when the accretion rate is high and exhibit short decay times, high peak fluxes, and radius expansion episodes. ``Slow bursts'' occur in the Island State at lower accretion rates, have lower peak fluxes, higher fluences, longer decay times, and show no evidence of radius expansion. All five of the fast bursts, and none of the four slow bursts, show coherent oscillations near 524 Hz. We perform in-burst phase connection of the burst pulsations, which allows us to unambiguously characterize their frequency evolution. That evolution exhibits a variety of behaviors, including a sharp spin-down during one burst. Applying our phase models, we find that the pulsations are spectrally harder than the burst emission, with the strength of the pulsations increasing monotonically with photon energy. Coherently summing...

  4. Swift detection of an intermediately long X-ray burst from the very faint X-ray binary XMMU J174716.1-281048

    CERN Document Server

    Degenaar, N; Kaur, R

    2011-01-01

    We report on the Swift detection of a thermonuclear X-ray burst from the very-faint quasi-persistent neutron star X-ray binary XMMU J174716.1-281048, which triggered the satellite's Burst Alert Telescope (BAT) on 2010 August 13. Analysis of the BAT spectrum yields an observed bolometric peak flux of ~4.5E-8 erg/cm2/s, from which we infer a source distance of <8.4 kpc. Follow-up observations with Swift's X-ray Telescope (XRT) suggest that the event had a duration of ~3 h, and classifies as an intermediately long X-ray burst. This is only the second X-ray burst ever reported from this source. Inspection of Swift/XRT observations performed between 2007-2010 suggests that the 2-10 keV accretion luminosity of the system is only ~5E34 erg/s for an assumed distance of 8.4 kpc. Despite being transient, XMMU J174716.1-281048 appears to have been continuously active since its discovery in 2003.

  5. TEMPORAL VARIATIONS OF X-RAY SOLAR FLARE LOOPS: LENGTH, CORPULENCE, POSITION, TEMPERATURE, PLASMA PRESSURE, AND SPECTRA

    OpenAIRE

    Jeffrey, Natasha L. S.; Kontar, Eduard P.

    2013-01-01

    The spatial and spectral properties of three solar flare coronal X-ray loops are studied before, during and after the peak X-ray emission. Using observations from the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), we deduce the temporal changes in emitting X-ray length, corpulence, volume, position, number density and thermal pressure. We observe a decrease in the loop length, width and volume before the X-ray peak, and an increasing number density and thermal pressure. After the X-r...

  6. Simultaneous H.E.S.S. and Chandra observations of Sgr A* during an X-ray flare

    OpenAIRE

    Hinton, Jim; Vivier, Matthieu; Bühler, Rolf; Pühlhofer, Gerd; Wagner, Stefan

    2007-01-01

    The rapidly varying non-thermal X-ray emission observed from Sgr A* points to particle acceleration taking place close to the supermassive black hole. The TeV gamma-ray source HESS J1745-290 is coincident with Sgr A* and may be closely related to the X-ray emission. Simultaneous X-ray and TeV observations are required to elucidate the relationship between these two objects. Here we report on joint H.E.S.S./Chandra observations in July 2005, during which an X-ray flare was detected. Despite a ...

  7. Exceptional flaring activity of the anomalous X-ray pulsar 1E 1547.0-5408

    CERN Document Server

    Savchenko, V; Beckmann, V; Produit, N; Walter, R

    2009-01-01

    (Abridged) We studied an exceptional period of activity of the anomalous X-ray pulsar 1E 1547.0-5408 in January 2009, during which about 200 bursts were detected by INTEGRAL. The major activity episode happened when the source was outside the field of view of all the INTEGRAL instruments. But we were still able to study the properties of 84 bursts detected simultaneously by the anti-coincidence shield of the spectrometer SPI and by the detector of the imager ISGRI. We find that the luminosity of the 22 January 2009 bursts of 1E 1547.0-5408 was > 1e42 erg/s. This luminosity is comparable to that of the bursts of soft gamma repeaters (SGR) and is at least two orders of magnitude larger than the luminosity of the previously reported bursts from AXPs. Similarly to the SGR bursts, the brightest bursts of 1E 1547.0-5408 consist of a short spike of ~100 ms duration with a hard spectrum, followed by a softer extended tail of 1-10 s duration, which occasionally exhibits pulsations with the source spin period of ~2 s. ...

  8. Long Type I X-ray Bursts and Neutron Star Interior Physics

    CERN Document Server

    Cumming, A; in 't Zand, J J M; Page, D; Cumming, Andrew; Macbeth, Jared; Page, Dany

    2005-01-01

    Superbursts are very energetic Type I X-ray bursts discovered in recent years by long term monitoring of X-ray bursters, believed to be due to unstable ignition of carbon in the deep ocean of the neutron star. A number of "intermediate duration" bursts have also been observed, probably associated with ignition of a thick helium layer. We investigate the sensitivity of these long X-ray bursts to the thermal profile of the neutron star crust and core. We first compare cooling models of superburst lightcurves with observations, and derive constraints on the ignition mass and energy release, and then calculate ignition models for superbursts and pure helium bursts, and compare to observations. The superburst lightcurves and ignition models imply that the carbon mass fraction is approximately 20% or greater in the fuel layer, constraining models of carbon production. However, the most important result is that when Cooper pairing neutrino emission is included in the crust, the temperature is too low to support unst...

  9. Statistics of X-Ray Flares of Sagittarius A*: Evidence for Solar-like Self-organized Criticality Phenomena

    Science.gov (United States)

    Li, Ya-Ping; Yuan, Feng; Yuan, Qiang; Wang, Q. Daniel; Chen, P. F.; Neilsen, Joseph; Fang, Taotao; Zhang, Shuo; Dexter, Jason

    2015-09-01

    X-ray flares have routinely been observed from the supermassive black hole at our Galactic center, Sagittarius A{}\\star (Sgr A⋆). The nature of these flares remains largely unclear, despite many theoretical models. In this paper, we study the statistical properties of the Sgr A⋆ X-ray flares by fitting the count rate (CR) distribution and the structure function of the light curve with a Markov Chain Monte Carlo method. With the 3-million-second Chandra observations accumulated in the Sgr A⋆ X-ray Visionary Project, we construct the theoretical light curves through Monte Carlo simulations. We find that the 2-8 keV X-ray light curve can be decomposed into a quiescent component with a constant CR of 6× {10}-3 count s-1 and a flare component with a power-law fluence distribution {dN}/{dE}\\propto {E}-{α {{E}}} with {α }{{E}}=1.65+/- 0.17. The duration-fluence correlation can also be modeled as a power law T\\propto {E}{α {ET}} with {α }{ET}\\lt 0.55 (95% confidence). These statistical properties are consistent with the theoretical prediction of the self-organized criticality system with the spatial dimension S = 3. We suggest that the X-ray flares represent plasmoid ejections driven by magnetic reconnection (similar to solar flares) in the accretion flow onto the black hole.

  10. Reconciliation of Waiting Time Statistics of Solar Flares Observed in Hard X-Rays

    OpenAIRE

    Aschwanden, Markus J.; McTiernan, James M.

    2010-01-01

    We study the waiting time distributions of solar flares observed in hard X-rays with ISEE-3/ICE, HXRBS/SMM, WATCH/GRANAT, BATSE/CGRO, and RHESSI. Although discordant results and interpretations have been published earlier, based on relatively small ranges ($< 2$ decades) of waiting times, we find that all observed distributions, spanning over 6 decades of waiting times ($\\Delta t \\approx 10^{-3}- 10^3$ hrs), can be reconciled with a single distribution function, $N(\\Delta t) \\propto \\lambda_0...

  11. Quantitative representation of nonrepetitive temporal behavior. [solar flares in soft x-ray flux application

    Science.gov (United States)

    Nakagawa, Y.; Teuber, D. L.

    1980-01-01

    Analytical representations suitable to analyze the nonrepetitive pulse-like temporal behavior of physical quantities are derived. The representation utilizes solutions of a linear model equation in which the temporal variation is subject to time-dependent driving and dissipative forces. The property of solutions is described, and it is shown that such representations can provide a basis for quantitative comparisons of behaviors and a basis for physically meaningful interpretations of the results. Observations of solar flares in the soft X-ray flux have been analyzed with this method.

  12. Statistical Analysis of Soft X-Ray Solar Flares During Solar Cycles 21, 22 and 23

    OpenAIRE

    Joshi, Navin Chandra; Bankoti, Neeraj Singh; Pande, Seema; Pande, Bimal; Pandey, Kavita

    2009-01-01

    This paper presents a statistical analysis of Soft X-ray (SXR) flares during the period January 1976 to December 2007 covering solar cycles (SCs) 21, 22, and 23. We have analysed north-south (N-S) and east-west (E-W) asymmetry of SXR at low (less than equal to 40 degree), high (greater than equal to 50 degree) and total latitudes and center meridian distances (CMDs) respectively. We have also presented the N-S and E-W asymmetry of different intensity classes (B, C, M, and X) during the period...

  13. RESIK observations of He-like Ar X-ray line emission in solar flares

    OpenAIRE

    Sylwester, J.; Sylwester, B.; Phillips, K. J. H.

    2008-01-01

    The Ar XVII X-ray line group principally due to transitions 1s2 - 1s2l (l=s, p) near 4 Anstroms was observed in numerous flares by the RESIK bent crystal spectrometer aboard CORONAS-F between 2001 and 2003. The three line features include the Ar XVII w (resonance line), a blend of x and y (intercombination lines), and z (forbidden line), all of which are blended with Ar XVI dielectronic satellites. The ratio G, equal to [I(x+y) + I(z)]/I(w), varies with electron temperature Te mostly because ...

  14. X-ray spectra and atmospheric structures of bursting neutron stars

    International Nuclear Information System (INIS)

    I discuss atmospheric structures and emitted x-ray spectra of bursting neutron stars. The x-ray spectrum is deformed from the blackbody spectrum by Comptonization and by a strong energy dependence of absorptive opacities. The atmospheric structures deviate from those of the Eddington atmospheres due to the Compton heating-cooling. I construct color temperature vs. luminosity diagrams from the atmospheric models of neutron stars. Comparing these with observational ones, I obtain two relations among mass, radius, and distance of the x-ray bursters MXB 1636 - 536 and MXB 1608 - 522. I derive two possible sets of mass, radius, and distance of the x-ray burst source MXB 1636 - 536 taking into account of the 4.1-keV absorption line, theoretical mass-radius relation of the neutron star, and the distance to the galactic center. If the absorption line is due to Cr 23 M = 1.7 - 2.0 solar mass, R = 11 - 12 km, and d = 6.3 - 6.7 kpc, and if it is due to Fe 25, M = 1.8 - 2.1 solar mass, R = 8 - 10 km, and d = 5.8 - 6.4 kpc. (author)

  15. Effective absorbing column density in the gamma-ray burst afterglow X-ray spectra

    CERN Document Server

    Campana, S; Braito, V; Cusumano, G; D'Avanzo, P; D'Elia, V; Ghirlanda, G; Ghisellini, G; Melandri, A; Salvaterra, R; Tagliaferri, G; Vergani, S D

    2014-01-01

    We investigate the scaling relation between the observed amount of absorption in the X-ray spectra of Gamma Ray Burst (GRB) afterglows and the absorber redshift. Through dedicated numerical simulations of an ideal instrument, we establish that this dependence has a power law shape with index 2.4. However, for real instruments, this value depends on their low energy cut-off, spectral resolution and on the detector spectral response in general. We thus provide appropriate scaling laws for specific instruments. Finally, we discuss the possibility to measure the absorber redshift from X-ray data alone. We find that 10^5-10^6 counts in the 0.3-10 keV band are needed to constrain the redshift with 10% accuracy. As a test case we discuss the XMM-Newton observation of GRB 090618 at z=0.54. We are able to recover the correct redshift of this burst with the expected accuracy.

  16. Effective absorbing column density in the gamma-ray burst afterglow X-ray spectra

    Science.gov (United States)

    Campana, S.; Bernardini, M. G.; Braito, V.; Cusumano, G.; D'Avanzo, P.; D'Elia, V.; Ghirlanda, G.; Ghisellini, G.; Melandri, A.; Salvaterra, R.; Tagliaferri, G.; Vergani, S. D.

    2014-07-01

    We investigate the scaling relation between the observed amount of absorption in the X-ray spectra of gamma-ray burst afterglows and the absorber redshift. Through dedicated numerical simulations of an ideal instrument, we establish that this dependence has a power-law shape with index 2.4. However, for real instruments, this value depends on their low-energy cut-off, spectral resolution and on the detector spectral response in general. We thus provide appropriate scaling laws for specific instruments. Finally, we discuss the possibility to measure the absorber redshift from X-ray data alone. We find that 105-106 counts in the 0.3-10 keV band are needed to constrain the redshift with 10 per cent accuracy. As a test case, we discuss the XMM-Newton observation of GRB 090618 at z = 0.54. We are able to recover the correct redshift of this burst with the expected accuracy.

  17. Comparisons of Two- and Three-Dimensional Convection in Type I X-ray Bursts

    CERN Document Server

    Zingale, M; Nonaka, A; Almgren, A S; Bell, J B

    2014-01-01

    We perform the first detailed three-dimensional simulation of low Mach number convection preceding thermonuclear ignition in a mixed H/He X-ray burst. Our simulations include a moderate-sized, approximate network that captures hydrogen and helium burning up through rp-process breakout. We look in detail at the difference between two- and three-dimensional convective fields, including the details of the turbulent convection.

  18. Evidence of elevated X-ray absorption before and during major flare ejections in GRS 1915+105

    International Nuclear Information System (INIS)

    We present time-resolved X-ray spectroscopy of the microquasar GRS 1915+105 with the MAXI observatory in order to study the accretion state just before and during the ejections associated with its major flares. Radio monitoring with the RATAN-600 radio telescope from 4.8-11.2 GHz has revealed two large, steep-spectrum major flares in the first eight months of 2013. Since the RATAN has received one measurement per day, we cannot determine the jet-forming time without more information. Fortunately, this is possible since a distinct X-ray light curve signature that occurs preceding and during major ejections has been determined in an earlier study. The X-ray luminosity spikes to very high levels in the hours before ejection, then becomes variable (with a nearly equal X-ray luminosity when averaged over the duration of the ejection) during a brief 3-8 hr ejection process. By comparing this X-ray behavior with MAXI light curves, we can estimate the beginning and end of the ejection episode of the strong 2013 flares to within ∼3 hr. Using this estimate in conjunction with time-resolved spectroscopy from the data in the MAXI archives allows us to deduce that the X-ray absorbing hydrogen column density increases significantly in the hours preceding the ejections and remains elevated during the ejections responsible for the major flares. This finding is consistent with an outflowing wind or enhanced accretion at high latitudes.

  19. Evidence of elevated X-ray absorption before and during major flare ejections in GRS 1915+105

    Energy Technology Data Exchange (ETDEWEB)

    Punsly, Brian [1415 Granvia Altamira, Palos Verdes Estates, CA 90274 (United States); Rodriguez, Jérôme [Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot, IRFU SAp, F-91191 Gif-sur-Yvette (France); Trushkin, Sergei A., E-mail: brian.punsly1@verizon.net, E-mail: brian.punsly@comdev-usa.com [Special Astrophysical Observatory RAS, Nizhnij Arkhyz, 369167 (Russian Federation)

    2014-03-10

    We present time-resolved X-ray spectroscopy of the microquasar GRS 1915+105 with the MAXI observatory in order to study the accretion state just before and during the ejections associated with its major flares. Radio monitoring with the RATAN-600 radio telescope from 4.8-11.2 GHz has revealed two large, steep-spectrum major flares in the first eight months of 2013. Since the RATAN has received one measurement per day, we cannot determine the jet-forming time without more information. Fortunately, this is possible since a distinct X-ray light curve signature that occurs preceding and during major ejections has been determined in an earlier study. The X-ray luminosity spikes to very high levels in the hours before ejection, then becomes variable (with a nearly equal X-ray luminosity when averaged over the duration of the ejection) during a brief 3-8 hr ejection process. By comparing this X-ray behavior with MAXI light curves, we can estimate the beginning and end of the ejection episode of the strong 2013 flares to within ∼3 hr. Using this estimate in conjunction with time-resolved spectroscopy from the data in the MAXI archives allows us to deduce that the X-ray absorbing hydrogen column density increases significantly in the hours preceding the ejections and remains elevated during the ejections responsible for the major flares. This finding is consistent with an outflowing wind or enhanced accretion at high latitudes.

  20. Response of the low ionosphere to X-ray and Lyman-α solar flare emissions

    Science.gov (United States)

    Raulin, Jean-Pierre; Trottet, GéRard; Kretzschmar, Matthieu; Macotela, Edith L.; Pacini, Alessandra; Bertoni, Fernando C. P.; Dammasch, Ingolf E.

    2013-01-01

    Using soft X-ray measurements from detectors onboard the Geostationary Operational Environmental Satellite (GOES) and simultaneous high-cadence Lyman-α observations from the Large Yield Radiometer (LYRA) onboard the Project for On-Board Autonomy 2 (PROBA2) ESA spacecraft, we study the response of the lower part of the ionosphere, the D region, to seven moderate to medium-size solar flares that occurred in February and March of 2010. The ionospheric disturbances are analyzed by monitoring the resulting sub-ionospheric wave propagation anomalies detected by the South America Very Low Frequency (VLF) Network (SAVNET). We find that the ionospheric disturbances, which are characterized by changes of the VLF wave phase, do not depend on the presence of Lyman-α radiation excesses during the flares. Indeed, Lyman-α excesses associated with flares do not produce measurable phase changes. Our results are in agreement with what is expected in terms of forcing of the lower ionosphere by quiescent Lyman-α emission along the solar activity cycle. Therefore, while phase changes using the VLF technique may be a good indicator of quiescent Lyman-α variations along the solar cycle, they cannot be used to scale explosive Lyman-α emission during flares.

  1. A New Relationship Between Soft X-Rays and EUV Flare Light Curves

    Science.gov (United States)

    Thiemann, Edward

    2016-05-01

    Solar flares are the result of magnetic reconnection in the solar corona which converts magnetic energy into kinetic energy resulting in the rapid heating of solar plasma. As this plasma cools, it emits radiation at different EUV wavelengths when the dropping temperature passes a line’s temperature of formation. This results in a delay in the emissions from cooler EUV lines relative to hotter EUV lines. Therefore, characterizing how this hot plasma cools is important for understanding how the corresponding geo-effective extreme ultraviolet (EUV) irradiance evolves in time. I present a simple new framework in which to study flare cooling by using a Lumped Element Thermal Model (LETM). LETM is frequently used in science and engineering to simplify a complex multi-dimensional thermal system by reducing it to a 0-D thermal circuit. For example, a structure that conducts heat out of a system is simplified with a resistive element and a structure that allows a system to store heat is simplified with a capacitive element. A major advantage of LETM is that the specific geometry of a system can be ignored, allowing for an intuitive analysis of the major thermal processes. I show that LETM is able to accurately reproduce the temporal evolution of cooler flare emission lines based on hotter emission line evolution. In particular, it can be used to predict the evolution of EUV flare light curves using the NOAA X-Ray Sensor (XRS).

  2. Hard X-Ray Polarization from Non-vertical Solar Flare Loops

    Science.gov (United States)

    Emslie, A. Gordon; Bradsher, Henry L.; McConnell, Mark L.

    2008-02-01

    McConnell et al. have reported preliminary results of hard X-ray polarization measured by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) in an intense solar flare on 2002 July 23. The magnitude of the reported polarization is broadly consistent with the predictions of existing solar flare models which invoke the precipitation of a nonthermal electron beam into a dense chromospheric target. However, the orientation of the polarization vector lies at a substantial angle to the local solar radial direction. This is inconsistent with model predictions of a polarization vector along the local radial direction, a prediction that is a direct consequence of the assumption of a vertical guiding magnetic field. Smith et al., in a study of the same 2002 July 23 event, have suggested that the magnetic structure in which the flare occurs is tilted relative to the local vertical. Motivated by this observation, and by the preliminary nonradial polarization vector reported by McConnell et al., we explore the effect of tilt of the flaring loop on the magnitude and orientation of the predicted polarization vector. We find that allowing loops tilted from the local solar vertical does indeed permit a much wider range of polarization vector orientations than allowed by purely vertical loop geometries. In particular, adding tilt of the magnitude inferred by Smith et al. for the 2002 July 23 event can in principle account for both the magnitude and direction of the polarization vector reported by McConnell et al. for that event.

  3. Comparative Analysis of VLF Signal Variation along Trajectory Induced by X-ray Solar Flares

    Science.gov (United States)

    Kolarski, A.; Grubor, D.

    2015-12-01

    Comparative qualitative analysis of amplitude and phase delay variations was carried out along the trajectory of GQD/22.1 kHz and NAA/24.0 kHz VLF signal traces, propagating from Skelton (UK) and Maine (USA) toward Belgrade, induced by four isolated solar X-ray flare events occurred during the period from September 2005 to December 2006. For monitoring, recording and for storage of VLF data at the Institute of Physics in Belgrade, Serbia, the AbsPAL system was used. For modeling purposes of propagating conditions along GQD and NAA signal propagation paths, LWPCv21 program code was used. Occurred solar flare events induced lower ionosphere electron density height profile changes, causing perturbations in VLF wave propagation within Earth-ionosphere waveguides. As analyzed VLF signals characterize by different propagation parameters along trajectories from their transmitters to the Belgrade receiver site, their propagation is affected in different ways for different solar flare events and also for the same solar flare events.

  4. Hard X-ray Emission During Flares and Photospheric Field Changes

    CERN Document Server

    Burtseva, O; Petrie, G J D; Pevtsov, A A

    2015-01-01

    We study the correlation between abrupt permanent changes of magnetic field during X-class flares observed by the GONG and HMI instruments, and the hard X-ray (HXR) emission observed by RHESSI, to relate the photospheric field changes to the coronal restructuring and investigate the origin of the field changes. We find that spatially the early RHESSI emission corresponds well to locations of the strong field changes. The field changes occur predominantly in the regions of strong magnetic field near the polarity inversion line (PIL). The later RHESSI emission does not correspond to significant field changes as the flare footpoints are moving away from the PIL. Most of the field changes start before or around the start time of the detectable HXR signal, and they end at about the same time or later than the detectable HXR flare emission. Some of the field changes propagate with speed close to that of the HXR footpoint at a later phase of the flare. The propagation of the field changes often takes place after the...

  5. Beacons in the sky: Classical novae vs. X-ray bursts

    International Nuclear Information System (INIS)

    Thermonuclear runaways are at the origin of some of the most energetic and frequent stellar cataclysmic events. In this review talk, we outline our understanding of the mechanisms leading to classical nova explosions and X-ray bursts, together with their associated nucleosynthesis. In particular, we focus on the interplay between nova outbursts and the Galactic chemical abundances (where 13C, 15N, and 17O constitute the likely imprints of many nova outbursts during the overall 10Gyr of Galactic history), the synthesis of radioactive nuclei of interest for gamma-ray astronomy (7Be-7Li, 22Na, or 26Al), the endpoint of nova nucleosynthesis, based on theoretical and observational grounds, and the recent discovery of presolar meteoritic grains, both in the Murchison and Acfer 094 meteorites, likely condensed in nova shells. Recent progress in the modeling of X-ray bursts as well as an insight into the input nuclear physics requests, for both novae and X-ray bursts, will also be presented. (orig.)

  6. A search for thermal X-ray signatures in gamma-ray bursts - I. Swift bursts with optical supernovae

    Science.gov (United States)

    Starling, R. L. C.; Page, K. L.; Pe'Er, A.; Beardmore, A. P.; Osborne, J. P.

    2012-12-01

    The X-ray spectra of gamma-ray bursts (GRBs) can generally be described by an absorbed power law. The landmark discovery of thermal X-ray emission in addition to the power law in the unusual GRB 060218, followed by a similar discovery in GRB 100316D, showed that during the first thousand seconds after trigger the soft X-ray spectra can be complex. Both the origin and prevalence of such spectral components still evade understanding, particularly after the discovery of thermal X-ray emission in the classical GRB 090618. Possibly most importantly, these three objects are all associated with optical supernovae (SNe), begging the question of whether the thermal X-ray components could be a result of the GRB-SN connection, possibly in the shock breakout. We therefore performed a search for blackbody components in the early Swift X-ray spectra of 11 GRBs that have or may have associated optical SNe, accurately recovering the thermal components reported in the literature for GRBs 060218, 090618 and 100316D. We present the discovery of a cooling blackbody in GRB 101219B/SN2010ma, and in four further GRB-SNe we find an improvement in the fit with a blackbody which we deem possible blackbody candidates due to case-specific caveats. All the possible new blackbody components we report lie at the high end of the luminosity and radius distribution. GRB 101219B appears to bridge the gap between the low-luminosity and the classical GRB-SNe with thermal emission, and following the blackbody evolution we derive an expansion velocity for this source of the order of 0.4c. We discuss potential origins for the thermal X-ray emission in our sample, including a cocoon model which we find can accommodate the more extreme physical parameters implied by many of our model fits.

  7. NuSTAR Observations of X-ray Bursts from the Magnetar 1E 1048.1-5937

    DEFF Research Database (Denmark)

    An, Hongjun; Kaspi, Victoria M.; Beloborodov, Andrei M.;

    2014-01-01

    We report the detection of eight bright X-ray bursts from the 6.5 s magnetar 1E 1048.1–5937, during a 2013 July observation campaign with the Nuclear Spectroscopic Telescope Array. We study the morphological and spectral properties of these bursts and their evolution with time. The bursts resulte...

  8. Observation of Sudden Ionospheric Disturbances over Istanbul in Response to X-Ray Flare Events

    Science.gov (United States)

    Ceren Kalafatoglu Eyiguler, Emine; Kaymaz, Zerefsan; Ceren Moral, Aysegul

    2016-07-01

    Sudden ionospheric disturbances (SID) are the enhanced electron density structures in the D region ionosphere which occur in response to the increase in X-ray flares and EUV flux. SIDs can be monitored using Very Low Frequency (VLF) radio signals (3-30 kHz) which travel between the D-region and the surface of the Earth. In this study, we use SID monitors obtained from the Stanford University Solar Center and two antennas which were built at the Istanbul Technical University to track the ionospheric disturbances in the VLF range. Our antennas are capable of capturing signals from several VLF transmitting stations. In this work, we focus on the variations in the signal strength of the closest VLF transmitting station 'TBB' which is operating at 26.7 kHz frequency at BAFA, Turkey (37.43N, 27.15E). We present ITU SID observations from both antennas; show the daily variation, general structure and the typical patterns we observe as well as case studies of significant events. Our initial analysis shows close relationship between observed X-ray flares from geosynchronous GOES 13 and GOES 15 satellites and VLF station signal strength received by the monitors.

  9. Behaviour of Electron Content in the Ionospheric D-Region During Solar X-Ray Flares

    Science.gov (United States)

    Todorović Drakul, M.; Čadež, V. M.; Bajčetić, J.; Popović, L. Č.; Blagojević, D.; Nina, A.

    2016-08-01

    One of the most important parameters in ionospheric plasma research, also having a wide practical application in wireless satellite telecommunications, is the total electron content (TEC) representing the columnal electron number density. The F-region with high electron density provides the biggest contribution to TEC while the relatively weakly ionized plasma of the D-region (60 km - 90 km above Earth's surface) is often considered as a negligible cause of satellite signal disturbances. However, sudden intensive ionization processes, like those induced by solar X-ray flares, can cause relative increases of electron density that are significantly larger in the D-region than in regions at higher altitudes. Therefore, one cannot exclude a priori the D-region from investigations of ionospheric influences on propagation of electromagnetic signals emitted by satellites. We discuss here this problem which has not been sufficiently treated in literature so far. The obtained results are based on data collected from the D-region monitoring by very low frequency radio waves and on vertical TEC calculations from the Global Navigation Satellite System (GNSS) signal analyses, and they show noticeable variations in the D-region's electron content (TEC_{D}) during activity of a solar X-ray flare (it rises by a factor of 136 in the considered case) when TEC_{D} contribution to TEC can reach several percent and which cannot be neglected in practical applications like global positioning procedures by satellites.

  10. Quasi-periodic Variations in the Hard X-ray emission of a Large Arcade Flare

    CERN Document Server

    Jakimiec, Jerzy

    2013-01-01

    Quasi-periodic oscillations of the hard X-ray (HXR) emission of the large flare of 2 November 1991 have been investigated using HXR light curves and soft X-ray and HXR images recorded by the {\\sl Yohkoh} X-ray telescopes. The results of the analysis of these observations are the following: i) The observations confirm that electrons are accelerated in oscillating magnetic traps which are contained within the cusp magnetic structure. ii) The amplitude of the HXR pulses increase due to the increase in the amplitude of the magnetic trap oscillations and the increase in the density within the traps caused by the chromospheric evaporation upflow. iii) The increase in the amplitude of the HXR pulses terminates when further increase in the density inside the traps inhibits the acceleration of electrons. iv) The model of oscillating magnetic traps is able to explain time variation of the electron precipitation, strong asymmetry in precipitation of accelerated electrons, and systematic differences in the precipitation ...

  11. The influence of albedo on the size of hard X-ray flare sources

    CERN Document Server

    Battaglia, Marina; Hannah, Iain G

    2010-01-01

    Context: Hard X-rays from solar flares are an important diagnostic of particle acceleration and transport in the solar atmosphere. Any observed X-ray flux from on-disc sources is composed of direct emission plus Compton backscattered photons (albedo). This affects both the observed spectra and images as well as the physical quantities derived from them such as the spatial and spectral distributions of accelerated electrons or characteristics of the solar atmosphere. Aims: We propose a new indirect method to measure albedo and to infer the directivity of X-rays in imaging using RHESSI data. Methods: Visibility forward fitting is used to determine the size of a disc event observed by RHESSI as a function of energy. This is compared to the sizes of simulated sources from a Monte Carlo simulation code of photon transport in the chromosphere for different degrees of downward directivity and true source sizes to find limits on the true source size and the directivity. Results: The observed full width half maximum o...

  12. X-ray hiccups from SgrA* observed by XMM-Newton. The second brightest flare and three moderate flares caught in half a day

    CERN Document Server

    Porquet, D; Predehl, P; Hasinger, G; Yusef-Zadeh, F; Aschenbach, B; Trap, G; Melia, F; Warwick, R S; Goldwurm, A; Bélanger, G; Tanaka, Y; Genzel, R; Dodds-Eden, K; Sakano, M; Ferrando, P

    2008-01-01

    [truncated] In Spring 2007, we observed SgrA* with XMM with a total exposure of ~230ks. We have performed timing and spectral analysis of the new X-ray flares detected during this campaign. To study the range of flare spectral properties, in a consistent manner, we have also reprocessed, using the same analysis procedure and the latest calibration, archived XMM data of previously reported rapid flares. The dust scattering was taken into account during the spectral fitting. We also used Chandra archived observations of the quiescent state of SgrA* for comparison. On April 4, 2007, we observed for the first time within a time interval of ~1/2 day, an enhanced incidence rate of X-ray flaring, with a bright flare followed by three flares of more moderate amplitude. The former event represents the second brightest X-ray flare from Sgr A* on record. This new bright flare exhibits similar light-curve shape (nearly symmetrical), duration (~3ks) and spectral characteristics to the very bright flare observed in October...

  13. X-ray Source Heights in a Solar Flare: Thick-target versus Thermal Conduction Front Heating

    CERN Document Server

    Reep, Jeffrey W; Holman, Gordon D

    2015-01-01

    Observations of solar flares with RHESSI have shown X-ray sources traveling along flaring loops, from the corona down to the chromosphere and back up. The 28 November 2002 C1.1 flare, first observed with RHESSI by Sui et al. 2006 and quantitatively analyzed by O'Flannagain et al. 2013, very clearly shows this behavior. By employing numerical experiments, we use these observations of X-ray source height motions as a constraint to distinguish between heating due to a non-thermal electron beam and in situ energy deposition in the corona. We find that both heating scenarios can reproduce the observed light curves, but our results favor non-thermal heating. In situ heating is inconsistent with the observed X-ray source morphology and always gives a height dispersion with photon energy opposite to what is observed.

  14. Dependence of X-Ray Burst Models on Nuclear Reaction Rates

    CERN Document Server

    Cyburt, R H; Heger, A; Johnson, E; Keek, L; Meisel, Z; Schatz, H; Smith, K

    2016-01-01

    X-ray bursts are thermonuclear flashes on the surface of accreting neutron stars and reliable burst models are needed to interpret observations in terms of properties of the neutron star and the binary system. We investigate the dependence of X-ray burst models on uncertainties in (p,$\\gamma$), ($\\alpha$,$\\gamma$), and ($\\alpha$,p) nuclear reaction rates using fully self-consistent burst models that account for the feedbacks between changes in nuclear energy generation and changes in astrophysical conditions. A two-step approach first identified sensitive nuclear reaction rates in a single-zone model with ignition conditions chosen to match calculations with a state-of-the-art 1D multi-zone model based on the {\\Kepler} stellar evolution code. All relevant reaction rates on neutron deficient isotopes up to mass 106 were individually varied by a factor of 100 up and down. Calculations of the 84 highest impact reaction rate changes were then repeated in the 1D multi-zone model. We find a number of uncertain reac...

  15. Statistical Analysis of Soft X-Ray Solar Flares During Solar Cycles 21, 22 and 23

    CERN Document Server

    Joshi, Navin Chandra; Pande, Seema; Pande, Bimal; Pandey, Kavita

    2009-01-01

    This paper presents a statistical analysis of Soft X-ray (SXR) flares during the period January 1976 to December 2007 covering solar cycles (SCs) 21, 22, and 23. We have analysed north-south (N-S) and east-west (E-W) asymmetry of SXR at low (less than equal to 40 degree), high (greater than equal to 50 degree) and total latitudes and center meridian distances (CMDs) respectively. We have also presented the N-S and E-W asymmetry of different intensity classes (B, C, M, and X) during the period of investigation. A slight southern and eastern excess is found after analysis during SC 21, 22, and 23. We found that the annual N-S and E-W hemispheric asymmetry at low latitudes and CMDs is the same as total latitudes and CMDs respectively. E-W asymmetry is different at low and high CMDs. Our statistical result shows that N-S asymmetry is statistically more significant than E-W asymmetry. Total SXR flare activity during SC 23 is high compared to SC 21 and 22. The B class flare activity is higher for SC 23 where as C, ...

  16. The influence of albedo on the size of hard X-ray flare sources

    Science.gov (United States)

    Battaglia, M.; Kontar, E. P.; Hannah, I. G.

    2011-02-01

    Context. Hard X-rays from solar flares are an important diagnostic of particle acceleration and transport in the solar atmosphere. However, any observed X-ray flux from on-disc sources is composed of direct emission plus Compton backscattered photons (albedo). This affects both the observed spectra and images and the physical quantities derived from them, such as the spatial and spectral distributions of accelerated electrons or characteristics of the solar atmosphere (e.g. density). Aims: We propose a new indirect method to measure albedo and to infer the directivity of X-rays in imaging using RHESSI data. We describe this method and demonstrate its application to a compact disc event observed with RHESSI. Methods: Visibility forward fitting is used to determine the size (second moment) of a disc event observed by RHESSI as a function of energy. Using a Monte Carlo simulation code of photon transport in the chromosphere, maps for different degrees of downward directivity and true source sizes are computed. The resulting sizes from the simulated maps are compared with the sizes from the observations to find limits on the true source size and the directivity. Results: The observed full width half maximum of the source varies in size between 7.4 arcsec and 9.1 arcsec with the maximum between 30 and 40 keV. Such behaviour is expected in the presence of albedo and is found in the simulations. The uncertainties in the data are not small enough to make unambiguous statements about the true source size and the directivity simultaneously. However, a source size smaller than 6 arcsec is improbable for modest directivities, and the true source size is likely to be around 7 arcsec for small directivities. Conclusions: While it is difficult to image the albedo patch directly, the effect of backscattered photons on the observed source size can be estimated. This is demonstrated here on observations for the first time. The increase in source size caused by albedo has to be

  17. Constraining cosmological parameters by Gamma Ray Burst X - ray afterglow lightcurves

    CERN Document Server

    Cardone, V F; Capozziello, S; Willingale, R

    2010-01-01

    We present the Hubble diagram (HD) of 66 Gamma Ray Bursts (GRBs) derived using only data from their X - ray afterglow lightcurve. To this end, we use the recently updated L_X - T_a correlation between the break time T_a and the X - ray luminosity L_X measured at T_a calibrated from a sample of Swift GRBs with lightcurves well fitted by the Willingale et al. (2007) model. We then investigate the use of this HD to constrain cosmological parameters when used alone or in combination with other data showing that the use of GRBs leads to constraints in agreement with previous results in literature. We finally argue that a larger sample of high luminosity GRBs can provide a valuable information in the search for the correct cosmological model.

  18. The Early X-ray Afterglows of Optically Bright and Dark Gamma-Ray Bursts

    Institute of Scientific and Technical Information of China (English)

    Yi-Qing Lin

    2006-01-01

    A systematic study on the early X-ray afterglows of both optically bright and dark gamma-ray bursts (B-GRBs and D-GRBs) observed by Swift is presented. Our sample includes 25 GRBs of which 13 are B-GRBs and 12 are D-GRBs. Our results show that the distributions of the X-ray afterglow fluxes (Fx), the gamma-ray fluxes (Sγ), and the ratio (Rγ,X) are similar for the two kinds of GRBs, that any observed differences should be simply statistical fluctuation. These results indicate that the progenitors of the two kinds of GRBs are of the same population with comparable total energies of explosion. The suppression of optical emission in the D-GRBs should result from circumburst but not from their central engine.

  19. A Spectacular Radio Flare from XRF 050416a at 40 days and Implications for the Nature of X-ray Flashes

    CERN Document Server

    Soderberg, A M; Cenko, S B; Cameron, P B; Frail, D A; Kulkarni, S R; Fox, D B; Berger, E; Gal-Yam, A; Moon, D S; Price, P A; Anderson, G; Schmidt, B P; Salvo, M; Rich, J; Rau, A; Ofek, E O; Chevalier, R A; Hamuy, M; Harrison, F A; Kumar, P; MacFadyen, A; McCarthy, P J; Park, H S; Peterson, B A; Phillips, M M; Rauch, M; Roth, M; Shectman, S

    2006-01-01

    We present detailed optical, near-infrared, and radio observations of the X-ray flash 050416a obtained with Palomar and Siding Springs Observatories as well as the Hubble Space Telescope and Very Large Array, placing this event among the best-studied X-ray flashes to date. In addition, we present an optical spectrum from the Low Resolution Spectrograph on Keck from which we measure the redshift of the burst, z=0.6528. At this redshift the isotropic-equivalent prompt energy release was about 10^51 erg, and using a standard afterglow synchrotron model we find that the blastwave kinetic energy is a factor of 10 larger, E(K,iso)~10^52 erg. The lack of an observed jet break to t~20 days indicates that the opening angle is larger than 7 degrees and the total beaming-corrected relativistic energy is greater than 10^50 erg. We further show that the burst produced a strong radio flare at t~40 days accompanied by an observed flattening in the X-ray band which we attribute to an abrupt circumburst density jump or an epi...

  20. The Height of a White-Light Flare and its Hard X-Ray Sources

    Science.gov (United States)

    Oliveros, Juan-Carlos Martinez; Hudson, Hugh S.; Hurford, Gordon J.; Kriucker, Saem; Lin, R. P.; Lindsey, Charles; Couvidat, Sebastien; Schou, Jesper; Thompson, W. T.

    2012-01-01

    We describe observations of a white-light (WL) flare (SOL2011-02-24T07:35:00, M3.5) close to the limb of the Sun, from which we obtain estimates of the heights of the optical continuum sources and those of the associated hard X-ray (HXR) sources. For this purpose, we use HXR images from the Reuven Ramaty High Energy Spectroscopic Imager and optical images at 6173 Ang. from the Solar Dynamics Observatory.We find that the centroids of the impulsive-phase emissions in WL and HXRs (30 -80 keV) match closely in central distance (angular displacement from Sun center), within uncertainties of order 0".2. This directly implies a common source height for these radiations, strengthening the connection between visible flare continuum formation and the accelerated electrons. We also estimate the absolute heights of these emissions as vertical distances from Sun center. Such a direct estimation has not been done previously, to our knowledge. Using a simultaneous 195 Ang. image from the Solar-Terrestrial RElations Observatory spacecraft to identify the heliographic coordinates of the flare footpoints, we determine mean heights above the photosphere (as normally defined; tau = 1 at 5000 Ang.) of 305 +/- 170 km and 195 +/- 70 km, respectively, for the centroids of the HXR and WL footpoint sources of the flare. These heights are unexpectedly low in the atmosphere, and are consistent with the expected locations of tau = 1 for the 6173 Ang and the approx 40 keV photons observed, respectively.

  1. UFCORIN: A Fully Automated Predictor of Solar Flares in GOES X-Ray Flux

    CERN Document Server

    Muranushi, Takayuki; Muranushi, Yuko Hada; Isobe, Hiroaki; Nemoto, Shigeru; Komazaki, Kenji; Shibata, Kazunari

    2015-01-01

    We have developed UFCORIN, a platform for studying and automating space weather prediction. Using our system we have tested 6,160 different combinations of SDO/HMI data as input data, and simulated the prediction of GOES X-ray flux for 2 years (2011-2012) with one-hour cadence. We have found that direct comparison of the true skill statistics (TSS) is ill-posed, and used the standard scores ($z$) of the TSS to compare the performance of the various prediction strategies. The best strategies we have found for predicting X, $\\geq$M and $\\geq$C class flares are better than the average of the 6,160 strategies by 2.3$\\sigma$, 2.1$\\sigma$, 3.8$\\sigma$ confidence levels, respectively. The best three's TSS values were $0.745\\pm0.072$, $0.481\\pm0.017$, and $0.557\\pm0.043$, respectively.

  2. Spatially resolved hard X-ray polarization in solar flares: effects of Compton scattering and bremsstrahlung

    CERN Document Server

    Jeffrey, Natasha

    2011-01-01

    This paper aims to study the polarization of hard X-ray (HXR) sources in the solar atmosphere, including Compton backscattering of photons in the photosphere (the albedo effect) and the spatial distribution of polarization across the source. HXR photon polarization and spectra produced via electron-ion bremsstrahlung are calculated from electron distributions typical for solar flares. Compton scattering and photoelectric absorption are then modelled using Monte Carlo simulations of photon transport in the photosphere. Polarization maps across HXR sources (primary and albedo components) for each of the modelled electron distributions are calculated at various source locations from the solar centre to the limb. We show that Compton scattering produces a distinct polarization variation across the albedo patch at peak albedo energies of 20-50 keV for all anisotropies modelled. The results show that there are distinct spatial polarization changes in both the radial and perpendicular to radial directions across the...

  3. Silicon X-ray line emission from solar flares and active regions

    International Nuclear Information System (INIS)

    New observations of solar flare and active region X-ray spectra obtained with the Columbia University instrument on OSO-8 are presented and discussed. The high sensitivity of the graphite crystal panel has allowed both line and continuum spectra to be observed with moderate spectral resolution. Observations with higher spectral resolution have been made with a panel of pentaerythritol crystals. Twenty-nine lines between 1.5 and 7.0 A have been resolved and identified, including several dielectronic recombination satellite lines to Si XIV and Si XIII lines which have been observed for the first time. It has been found that thermal continuum models specified by single values of temperature and emission measure have fitted that data adequately, there being good agreement with the values of these parameters derived from line intensity ratios. (Auth.)

  4. A Spectacular Radio Flare from XRF 050416a at 40 Days and Implications for the Nature of X-Ray Flashes

    Science.gov (United States)

    Soderberg, A. M.; Nakar, E.; Cenko, S. B.; Cameron, P. B.; Frail, D. A.; Kulkarni, S. R.; Fox, D. B.; Berger, E.; Gal-Yam, A.; Moon, D-S.; Price, P. A.; Anderson, G.; Schmidt, B. P.; Salvo, M.; Rich, J.; Rau, A.; Ofek, E. O.; Chevalier, R. A.; Hamuy, M.; Harrison, F. A.; Kumar, P.; MacFadyen, A.; McCarthy, P. J.; Park, H. S.; Peterson, B. A.

    2007-01-01

    We present detailed optical, near-infrared, and radio observations of the X-ray flash 050416a obtained with Palomar and Siding Springs Observatories as well as HST and the VLA, placing this event among the best-studied X-ray flashes to date. In addition, we present an optical spectrum from Keck LRIS from which we measure the redshift of the burst, Z=0.6528. At this redshift the isotropic-equivalent prompt energy release was about 10(exp 51) erg, and using a standard afterglow synchrotron model we find that the blastwave kinetic energy is a factor of 10 larger, E-K,iso approximately equals 10 (exp 52) erg. The lack of an observed jet break to t - 20 days indicates that the opening angle is larger than 7 deg and the total beaming-corrected relativistic energy is larger than 10 exp (50) erg. We further show that the burst produced a strong radio flare at t is similar to 40 days accompanied by an observed flattening in the X-ray band which we attribute to an abrupt circumburst density jump or an episode of energy injection (either from a refreshed shock or off-axis ejecta). Late-time observations with HST show evidence for an associated supernova with peak optical luminosity roughly comparable to that of SN 1998bw. Next, we show that the host galaxy of XRF 050416a is actively forming stars at a rate of at least 2 M-solar per year with a luminosity of L-B is similar to 0.5L* and metallicity of Z is similar to 0.2-0.8 Z-solar. Finally, we discuss the nature of XRF 050416a in the context of short-hard gamma-ray bursts and under the framework of off-axis and dirty fireball models for X-ray flashes.

  5. On the Late-Time Spectral Softening Found in X-ray Afterglows of Gamma-Ray Bursts

    CERN Document Server

    Wang, Yuan-Zhu; Shao, Lang; Liang, En-Wei; Lu, Zu-Jia

    2016-01-01

    Strong spectral softening has been revealed in the late X-ray afterglows of some gamma-ray bursts (GRBs). The scenario of X-ray scattering around circum-burst dusty medium has been supported by previous works due to its overall successful prediction of both the temporal and spectral evolution of some X-ray afterglows. To further investigate the observed feature of spectral softening, we now systematically search the X-ray afterglows detected by X-Ray Telescope (XRT) of Swift and collect twelve GRBs with significant late-time spectral softening. We find that dust scattering could be the dominant radiative mechanism for these X-ray afterglows regarding their temporal and spectral features. For some well observed bursts with high-quality data, their time-resolved spectra could be well produced within the scattering scenario by taking into account the X-ray absorption from circum-burst medium. We also find that during spectral softening the power-law index in the high energy end of the spectra does not vary much....

  6. RESIK observations of He-like Ar X-ray line emission in solar flares

    CERN Document Server

    Sylwester, J; Phillips, K J H

    2008-01-01

    The Ar XVII X-ray line group principally due to transitions 1s2 - 1s2l (l=s, p) near 4 Anstroms was observed in numerous flares by the RESIK bent crystal spectrometer aboard CORONAS-F between 2001 and 2003. The three line features include the Ar XVII w (resonance line), a blend of x and y (intercombination lines), and z (forbidden line), all of which are blended with Ar XVI dielectronic satellites. The ratio G, equal to [I(x+y) + I(z)]/I(w), varies with electron temperature Te mostly because of unresolved dielectronic satellites. With temperatures estimated from GOES X-ray emission, the observed G ratios agree fairly well with those calculated from CHIANTI and other data. With a two-component emission measure, better agreement is achieved. Some S XV and S XVI lines blend with the Ar lines, the effect of which occurs at temperatures greater than 8MK, allowing the S/Ar abundance ratio to be determined. This is found to agree with coronal values. A nonthermal contribution is indicated for some spectra in the rep...

  7. Possible hard X-ray shortages in bursts from KS 1731-260 and 4U 1705-44

    CERN Document Server

    Ji, Long; Chen, YuPeng; Zhang, Shuang-Nan; Kretschmar, Peter; Wang, Jian-Min; Li, Jian

    2014-01-01

    Aims: A hard X-ray shortage, implying the cooling of the corona, was observed during bursts of IGR J17473-272, 4U 1636-536, Aql X-1, and GS 1826-238. Apart from these four sources, we investigate here an atoll sample, in which the number of bursts for each source is larger than 5, to explore the possible additional hard X-ray shortage during {\\it Rossi X-ray timing explorer (RXTE)} era. Methods: According to the source catalog that shows type-I bursts, we analyzed all the available pointing observations of these sources carried out by the {\\it RXTE} proportional counter array (PCA). We grouped and combined the bursts according to their outburst states and searched for the possible hard X-ray shortage while bursting. Results: We found that the island states of KS 1731-260 and 4U 1705-44 show a hard X-ray shortage at significant levels of 4.5 and 4.7 $\\sigma$ and a systematic time lag of $0.9 \\pm 2.1$ s and $2.5 \\pm 2.0$ s with respect to the soft X-rays, respectively. While in their banana branches and other s...

  8. Recent advances in the modelling of classical novae and type I X-ray bursts

    International Nuclear Information System (INIS)

    Classical nova outbursts and type I X-ray bursts are thermonuclear stellar explosions driven by charged-particle reactions. Extensive numerical simulations of nova explosions have shown that the accreted envelopes attain peak temperatures between 0.1 and 0.4 GK, for about several hundred seconds, and therefore, their ejecta is expected to show signatures of significant nuclear activity. Indeed, it has been claimed that novae play some role in the enrichment of the interstellar medium through a number of intermediate-mass elements. This includes 17O, 15N, and 13C, systematically overproduced in huge amounts with respect to solar abundances, with a lower contribution to a number of species with A7Li, 19F, or 26Al. In this review, we present new 1-D hydrodynamic models of classical nova outbursts, from the onset of accretion up to the explosion and ejection phases. Special emphasis is put on their gross observational properties (including constraints from meteoritic presolar grains and potential gamma-ray signatures) and on their associated nucleosynthesis. Multidimensional models of mixing at the core-envelope interface during outbursts will also be presented. The impact of nuclear uncertainties on the final yields will be also outlined. Detailed analysis of the relevant reactions along the main nuclear path for type I X-ray bursts has only been scarcely addressed, mainly in the context of parameterized one-zone models. Here, we present a detailed study of the nucleosynthesis and nuclear processes powering type I X-ray bursts. The reported bursts have been computed by means of a spherically symmetric (1D), Lagrangian, hydrodynamic code, linked to a nuclear reaction network that contains 325 isotopes (from 1H to 107Te), and 1392 nuclear processes. These evolutionary sequences, followed from the onset of accretion up to the explosion and expansion stages, have been performed for two different metallicities to explore the dependence between the extension of the main

  9. Using infrared/X-ray flare statistics to probe the emission regions near the event horizon of Sgr A*

    CERN Document Server

    Dibi, Salome; Belmont, Renaud; Malzac, Julien; Neilsen, Joey; Witzel, Gunther

    2016-01-01

    The supermassive black hole at the centre of the Galaxy flares at least daily in the infrared (IR) and X-ray bands, yet the process driving these flares is still unknown. So far detailed analysis has only been performed on a few bright flares. In particular, the broadband spectral modelling suffers from a strong lack of simultaneous data. However, new monitoring campaigns now provide data on thousands of flaring events, allowing a statistical analysis of the flare properties. In this paper, we investigate the X-ray and IR flux distributions of the flare events. Using a self-consistent calculation of the particle distribution, we model the statistical properties of the flares. Based on a previous work on single flares, we consider two families of models: pure synchrotron models and synchrotron self-Compton (SSC) models. We investigate the effect of fluctuations in some relevant parameters (e.g. acceleration properties, density, magnetic field) on the flux distributions. The distribution of these parameters is ...

  10. Classical novae and type I X-ray bursts: Challenges for the 21st century

    International Nuclear Information System (INIS)

    Classical nova explosions and type I X-ray bursts are the most frequent types of thermonuclear stellar explosions in the Galaxy. Both phenomena arise from thermonuclear ignition in the envelopes of accreting compact objects in close binary star systems. Detailed observations of these events have stimulated numerous studies in theoretical astrophysics and experimental nuclear physics. We discuss observational features of these phenomena and theoretical efforts to better understand the energy production and nucleosynthesis in these explosions. We also examine and summarize studies directed at identifying nuclear physics quantities with uncertainties that significantly affect model predictions

  11. The Microchannel X-ray Telescope for the Gamma-Ray Burst mission SVOM

    CERN Document Server

    Gotz, D; Cordier, B; Paul, J; Evans, P; Beardmore, A; Martindale, A; Willingale, R; O'Brien, P; Basa, S; Rossin, C; Godet, O; Webb, N; Greiner, J; Nandra, K; Meidinger, N; Perinati, E; Santangelo, A; Mercier, K; Gonzalez, F

    2014-01-01

    We present the Microchannel X-ray Telescope, a new light and compact focussing telescope that will be flying on the Sino-French SVOM mission dedicated to Gamma-Ray Burst science. The MXT design is based on the coupling of square pore micro-channel plates with a low noise pnCCD. MXT will provide an effective area of about 50 cmsq, and its point spread function is expected to be better than 3.7 arc min (FWHM) on axis. The estimated sensitivity is adequate to detect all the afterglows of the SVOM GRBs, and to localize them to better then 60 arc sec after five minutes of observation.

  12. Evidence of Elevated X-Ray Absorption Before and During Major Flare Ejections in GRS 1915+105

    CERN Document Server

    Punsly, Brian; Trushkin, Sergei A

    2014-01-01

    We present time resolved X-ray spectroscopy of the microquasar GRS1915+105 with the MAXI observatory in order to study the accretion state just before and during the ejections associated with its major flares. Radio monitoring with the RATAN-600 radio telescope from 4.8 - 11.2 GHz has revealed two large steep spectrum major flares in the first eight months of 2013. Since, the RATAN receives one measurement per day, we cannot determine the jet forming time without more information. Fortunately, this is possible since a distinct X-ray light curve signature that occurs preceding and during major ejections has been determined in an earlier study. The X-ray luminosity spikes to very high levels in the hours before ejection then becomes variable (with a nearly equal X-ray luminosity when averaged over the duration of the ejection) during a brief 3 to 8 hour ejection process. By comparing this X-ray behavior to MAXI light curves, we can estimate the beginning and end of the ejection episode of the strong 2013 flares...

  13. NuSTAR detection of high-energy X-ray emission and rapid variability from sagittarius A* flares

    DEFF Research Database (Denmark)

    Barrière, Nicolas M.; Tomsick, John A.; Baganoff, Frederick K.;

    2014-01-01

    two brightest flares (∼55 times quiescence in the 2-10 keV band) are compared to simple physical models in an attempt to identify the main X-ray emission mechanism, but the data do not allow us to significantly discriminate between them. However, we confirm the previous finding that the parameters...

  14. Statistics of X-ray flares of Sgr A*: evidence for solar-like self-organized criticality phenomenon

    CERN Document Server

    Li, Ya-Ping; Yuan, Qiang; Wang, Q Daniel; Chen, P F; Neilsen, Joseph; Fang, Taotao; Zhang, Shuo; Dexter, Jason

    2015-01-01

    X-ray flares have routinely been observed from the supermassive black hole, Sgr A*, at our Galactic center. The nature of these flares remains largely unclear, despite of many theoretical models,. In this paper, we study the statistical properties of the Sgr A* X-ray flares, by fitting the count rate (CR) distribution and the structure function (SF) of the light curve with a Markov Chain Monte Carlo (MCMC) method. With the 3 million second \\textit{Chandra} observations accumulated in the Sgr A* X-ray Visionary Project, we construct the theoretical light curves through Monte Carlo simulations. We find that the $2-8$ keV X-ray light curve can be decomposed into a quiescent component with a constant count rate of $ 6\\times10^{-3} $count s$^{-1}$ and a flare component with a power-law fluence distribution $dN/dE\\propto E^{-\\alpha_{\\rm E}}$ with $\\alpha_{\\rm E}=1.65\\pm0.17$. The duration-fluence correlation can also be modelled as a power-law $T\\propto E^{\\alpha_{\\rm ET}}$ with $\\alpha_{\\rm ET} < 0.55$ ($95\\%$ ...

  15. Some studies on low-frequency signal in relation to X-ray flares and climatic conditions

    Directory of Open Access Journals (Sweden)

    S. K. Sarkar

    Full Text Available The statistical behaviour of the sudden enhancement in signal strength (SES in relation to solar X-ray flares has been studied for the near east-west propagation of 40 kHz radio waves from Sanwa (36°11'N; 139°51'E in Japan to Calcutta (22°34'N; 88°24'E over a long distance path of 5100 km for a period of two years. The period has been divided into four phases - P1, P2, P3 and P4, according to the position of the overhead sun. The change in signal strength during X-ray flares is dependent on the solar zenith angle and climatic conditions. The statistical modal values of the time lag of the SES peak with respect to that solar X-ray flare is found to increase as solar zenith angle increases. The relative rates of increase and decrease of the signal strength (RRISS and RRDSS respectively have been evaluated for a number of SES which are related to large X-ray flares. Their characteristics have also been investigated. The modal values of the relaxation time have been found to be highly correlated with climatic conditions like temperature and humidity of the propagation path.

  16. The Solar Flare Chlorine Abundance from RESIK X-ray Spectra

    CERN Document Server

    Sylwester, B; Sylwester, J; Kuznetsov, V D

    2011-01-01

    The abundance of chlorine is determined from X-ray spectra obtained with the RESIK instrument on {\\em CORONAS-F} during solar flares between 2002 and 2003. Using weak lines of He-like Cl, \\ion{Cl}{16}, between 4.44 and 4.50 \\AA, and with temperatures and emission measures from {\\em GOES} on an isothermal assumption, we obtained $A({\\rm Cl}) = 5.75 \\pm 0.26$ on a scale $A({\\rm H}) = 12$. The uncertainty reflects an approximately factor 2 scatter in measured line fluxes. Nevertheless our value represents what is probably the best solar determination yet obtained. It is higher by factors of 1.8 and 2.7 than Cl abundance estimates from an infrared sunspot spectrum and nearby \\ion{H}{2} regions. The constancy of the RESIK abundance values over a large range of flares ({\\em GOES} class from below C1 to X1) argues for any fractionation that may be present in the low solar atmosphere to be independent of the degree of solar activity.

  17. On the Spatial Distribution of Hard X-Rays from Solar Flare Loops

    CERN Document Server

    Petrosyan, V; Petrosian, Vahe; Donaghy, Timothy Q.

    1999-01-01

    The aim of this paper is to investigate the spatial structure of the impulsive phase hard X-ray emission from solar flares. This work is motivated by the YOHKOH and the forthcoming HESSI observations. Summarizing past results, it is shown that the transport effects can account for the observations by inhomogeneous loops where there is a strong field convergence and/or density enhancement at the top of the flaring loop. Scattering by plasma turbulence at the acceleration site or pancake type pitch angle distribution of the accelerated electrons can also give rise to enhanced emission at the loop tops. These could be a natural consequence of acceleration by plasma waves. This paper considers a general case of stochastic scattering and acceleration that leads to an isotropic pitch angle distribution and an enhanced emission from the loop tops or the acceleration site. Following the formalism developed in earlier papers the strength and the spectrum of the radiation expected from the acceleration site and the foo...

  18. A fundamental plane for gamma-ray bursts with X-ray plateaus

    CERN Document Server

    Dainotti, Maria Giovanna; Hernandez, Xavier; Ostrowski, Michał

    2016-01-01

    A class of long Gamma-Ray Bursts (GRBs) presenting light curves with an extended plateau phase in their X-ray afterglows obeys a correlation between the rest frame end time of the plateau, $T_a$, and its corresponding X-ray luminosity, $L_{a}$, Dainotti et al. (2008). In this work we perform an analysis of a total sample of 176 {\\it Swift} GRBs with known redshifts, exhibiting afterglow plateaus. By adding a third parameter, that is the peak luminosity in the prompt emission, $L_{peak}$, we discover the existence of a new three parameter correlation, a GRB `fundamental plane'. The scatter of data about this plane becomes smaller when a class-specific GRB sample is defined. This sample of 122 GRBs is selected from the total sample by excluding GRBs with associated Supernovae (SNe), X-ray flashes and short GRBs with extended emission. Moreover, we further limit our analysis to GRBs with lightcurves having good data coverage and almost flat plateaus, 40 GRBs forming our `gold sample'. The intrinsic scatter, $\\si...

  19. A Comprehensive Study of the X-ray Bursts from the Magnetar Candidate 1E 2259+586

    CERN Document Server

    Gavriil, F P; Woods, P M; Gavriil, Fotis P.; Kaspi, Victoria M.; Woods, Peter M.

    2003-01-01

    We present a statistical analysis of the X-ray bursts observed from the 2002 June 18 outburst of the Anomalous X-ray Pulsar (AXP) 1E 2259+586, observed with the Proportional Counter Array (PCA) aboard the Rossi X-ray Timing Explorer. We show that the properties of these bursts are similar to those of Soft Gamma-Repeaters (SGRs). The similarities we find are the burst durations follow a log-normal distribution which peaks at 99 ms, the differential burst fluence distribution is well described by a power law of index -1.7, the burst fluences are positively correlated with the burst durations, the distribution of waiting times is well described by a log-normal distribution of mean 47 s, and the bursts are generally asymmetric with faster rise than fall times. However, we find several quantitative differences between the AXP and SGR bursts. Specifically, the AXP bursts we observed exhibit a wider range of durations, the correlation between burst fluence and duration is flatter than for SGRs, the observed AXP burs...

  20. Hard X-Ray Flare Source Sizes Measured with the Ramaty High Energy Solar Spectroscopic Imager

    Science.gov (United States)

    Dennis, Brian R.; Pernak, Rick L.

    2009-01-01

    Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observations of 18 double hard X-ray sources seen at energies above 25 keV are analyzed to determine the spatial extent of the most compact structures evident in each case. The following four image reconstruction algorithms were used: Clean, Pixon, and two routines using visibilities maximum entropy and forward fit (VFF). All have been adapted for this study to optimize their ability to provide reliable estimates of the sizes of the more compact sources. The source fluxes, sizes, and morphologies obtained with each method are cross-correlated and the similarities and disagreements are discussed. The full width at half-maximum (FWHM) of the major axes of the sources with assumed elliptical Gaussian shapes are generally well correlated between the four image reconstruction routines and vary between the RHESSI resolution limit of approximately 2" up to approximately 20" with most below 10". The FWHM of the minor axes are generally at or just above the RHESSI limit and hence should be considered as unresolved in most cases. The orientation angles of the elliptical sources are also well correlated. These results suggest that the elongated sources are generally aligned along a flare ribbon with the minor axis perpendicular to the ribbon. This is verified for the one flare in our list with coincident Transition Region and Coronal Explorer (TRACE) images. There is evidence for significant extra flux in many of the flares in addition to the two identified compact sources, thus rendering the VFF assumption of just two Gaussians inadequate. A more realistic approximation in many cases would be of two line sources with unresolved widths. Recommendations are given for optimizing the RHESSI imaging reconstruction process to ensure that the finest possible details of the source morphology become evident and that reliable estimates can be made of the source dimensions.

  1. Polarization evidence for the isotropy of electrons responsible for the production of 5-20 keV X-rays in solar flares

    Science.gov (United States)

    Tramiel, L. J.; Novick, R.; Chanan, G. A.

    1984-05-01

    We have flown a solar flare X-ray polarimeter on the third flight (STS 3) of the Space Shuttle Columbia as part of the OSS-1 pallet of instruments. We observed eight solar flares in the 5-20 keV band on 1982 March 28. The signal-to-background ratio in all cases exceeded 25. A preflight contamination problem invalidated the earlier laboratory calibration, and the instrument had to be calibrated in-flight against two flares near the center of the solar disk, which are expected to be unpolarized on geometric grounds in a variety of models. No statistically significant polarization was then detected in any of the other six flares. Upper limits (99% confidence level) range from 2.5% to 12.7%. For two of the observed flares these results disagree with the predictions of a simple radially beamed, linear bremsstrahlung model at greater than 99% confidence. One of these flares had a hard impulsive burst; the measured upper limit on this burst (10%) also disagrees with the predictions of the beamed hypothesis. If the calibration flares were polarized, then the above upper limits can be interpreted as limits on the changes in polarization from flare to flare. Because the observed flares spanned a large longitude range and because the predictions of the beamed models depend fairly sensitively on viewing angle, the small relative polarizations are still difficult to reconcile with simple beamed models. The results are also compared with recent, more sophisticated models of Leach and Petrosian, which generally predict lower polarizations. We find that the observations are marginally inconsistent with a model in which the electrons are initially strongly beamed, but subsequently become largely isotropic as a result of the effects of a converging magnetic field; they are consistent with a model in which the electrons are injected isotropically, but in which the preference for motion along the magnetic field lines is explicitly taken into account. The results are also consistent

  2. Fast and slow magnetic deflagration fronts in Type I X-ray bursts

    CERN Document Server

    Cavecchi, Yuri; Watts, Anna L; Braithwaite, Jonathan

    2015-01-01

    Type I X-ray bursts are produced by thermonuclear runaways that develop on accreting neutron stars. Once one location ignites, the flame propagates across the surface of the star. Flame propagation is fundamental in order to understand burst properties like rise time and burst oscillations. Previous work quantified the effects of rotation on the front, showing that the flame propagates as a deflagration and that the front strongly resembles a hurricane. However the effect of magnetic fields was not investigated, despite the fact that magnetic fields strong enough to have an effect on the propagating flame are expected to be present on many bursters. In this paper we show how the coupling between fluid layers introduced by an initially vertical magnetic field plays a decisive role in determining the character of the fronts that are responsible for the Type I bursts. In particular, on a star spinning at 450 Hz (typical among the bursters) we test seed magnetic fields of $10^{7} - 10^{10}$ G and find that for th...

  3. Flares from a new Integral hard X-ray source, IGR J17407-2808, likely associated with the ROSAT source SBM 10

    DEFF Research Database (Denmark)

    Kretschmar, P.; Mereghetti, S.; Hermsen, W.;

    2004-01-01

    detected. The last flare, with peak fluxes of 0.8±0.1 Crab and 0.6±0.1 Crab in the energy ranges 20-40 keV and 40-60 keV respectively, triggered an automatic alert message of the Integral Burst Alert System (IBAS Alert #2010) which led to the discovery of the source (Gotz et al., GCN Circ. #2793). The...... observations of [SBM2001] 10 have been published up to date. The flares were observed with the IBIS instrument in the 20-60 keV energy range, starting at MJD 53287.6310 and over a timespan of 2000 seconds finishing in a strong flare at MJD 53287.6327. Before and after this time period the source was not...... source was outside the FOV of the JEM-X and OMC monitor instruments during this flare. Note that the position of J17407-2808 is inconsistent with that of the X-ray burster SLX 1737-282 [AX J1740.7-2818] (in't Zand et al. 2002, A&A 389, L43), which is just ~11 arcmin away. The correct Integral attitude is...

  4. X-ray hiccups from SgrA* observed by XMM-Newton. The second brightest flare and three moderate flares caught in half a day

    OpenAIRE

    Porquet, D.; N. Grosso; Predehl, P.; Hasinger, G.; Yusef-Zadeh, F.; Aschenbach, B.; Trap, G.; Melia, F.; Warwick, R. S.; Goldwurm, A.; Belanger, G.; Tanaka, Y.; Genzel, R.; Dodds-Eden, K.; Sakano, M.

    2008-01-01

    [truncated] In Spring 2007, we observed SgrA* with XMM with a total exposure of ~230ks. We have performed timing and spectral analysis of the new X-ray flares detected during this campaign. To study the range of flare spectral properties, in a consistent manner, we have also reprocessed, using the same analysis procedure and the latest calibration, archived XMM data of previously reported rapid flares. The dust scattering was taken into account during the spectral fitting. We also used Chandr...

  5. Study of underlying particle spectrum during huge X-ray flare of Mkn 421 in April 2013

    CERN Document Server

    Sinha, Atreyee; Misra, Ranjeev; Chitnis, Varsha R; Rao, A R; Acharya, B S

    2015-01-01

    Context: In April 2013, the nearby (z=0.031) TeV blazar, Mkn 421, showed one of the largest flares in X-rays since the past decade. Aim: To study all multiwavelength data available during MJD 56392 to 56403, with special emphasis on X-ray data, and understand the underlying particle energy distribution. Methods: We study the correlations between the UV and gamma bands with the X-ray band using the z-transformed discrete correlation function. We model the underlying particle spectrum with a single population of electrons emitting synchrotron radiation, and do a statistical fitting of the simultaneous, time-resolved data from the Swift-XRT and the NuSTAR. Results: There was rapid flux variability in the X-ray band, with a minimum doubling timescale of $1.69 \\pm 0.13$ hrs. There were no corresponding flares in UV and gamma bands. The variability in UV and gamma rays are relatively modest with $ \\sim 8 \\% $ and $\\sim 16 \\% $ respectively, and no significant correlation was found with the X-ray light curve. The ob...

  6. The bright knots at the tops of soft X-ray flare loops: Quantitative results from Yohkoh

    Science.gov (United States)

    Doschek, G. A.; Strong, K. T.; Tsuneta, S.

    1995-01-01

    Soft X-ray Telescope (SXT) observations from the Japanese Yohkoh spacecraft have shown that confined bright regions are common features at the tops of flare loops throughout most of the duration of the flares. In this paper we present quantitative results for these flare knots, in relation to other flare regions, for four relatively 'simple' flares. Emission measure distributions, electron temperatures, and electron densities are derived from SXT and Yohkoh Bragg Crystal Spectrometer (BCS) observations. The four flares selected are dominated by what appear to be single-loop structures, with bright knots at the loop tops. The flares are neither long-duration nor impulsive events. The spatial distributions of brightness and emission measure in the flares are found to be quite similar for all four events, even though there are significant differences in dynamical behavior between at least two of the events. Temperatures and densities calculated for these flares are consistent with previous results from many solar experiments. An investigation of intensity correlations between adjacent pixels at the tops of the loops suggests the existence of local disturbances in the magnetic loops that occur on spatial scales less than the radii of the loops.

  7. QPOs from Random X-ray Bursts around Rotating Black Holes

    Science.gov (United States)

    Kukumura, Keigo; Kazanas, Demosthenes; Stephenson, Gordon

    2009-01-01

    We continue our earlier studies of quasi-periodic oscillations (QPOs) in the power spectra of accreting, rapidly-rotating black holes that originate from the geometric 'light echoes' of X-ray flares occurring within the black hole ergosphere. Our present work extends our previous treatment to three-dimensional photon emission and orbits to allow for arbitrary latitudes in the positions of the distant observers and the X-ray sources in place of the mainly equatorial positions and photon orbits of the earlier consideration. Following the trajectories of a large number of photons we calculate the response functions of a given geometry and use them to produce model light curves which we subsequently analyze to compute their power spectra and autocorrelation functions. In the case of an optically-thin environment, relevant to advection-dominated accretion flows, we consistently find QPOs at frequencies of order of approximately kHz for stellar-mass black hole candidates while order of approximately mHz for typical active galactic nuclei (approximately equal to 10(exp 7) solar mass) for a wide range of viewing angles (30 degrees to 80 degrees) from X-ray sources predominantly concentrated toward the equator within the ergosphere. As in out previous treatment, here too, the QPO signal is produced by the frame-dragging of the photons by the rapidly-rotating black hole, which results in photon 'bunches' separated by constant time-lags, the result of multiple photon orbits around the hole. Our model predicts for various source/observer configurations the robust presence of a new class of QPOs, which is inevitably generic to curved spacetime structure in rotating black hole systems.

  8. Estimating the Properties of Hard X-Ray Solar Flares by Constraining Model Parameters

    Science.gov (United States)

    Ireland, J.; Tolbert, A. K.; Schwartz, R. A.; Holman, G. D.; Dennis, B. R.

    2013-06-01

    We wish to better constrain the properties of solar flares by exploring how parameterized models of solar flares interact with uncertainty estimation methods. We compare four different methods of calculating uncertainty estimates in fitting parameterized models to Ramaty High Energy Solar Spectroscopic Imager X-ray spectra, considering only statistical sources of error. Three of the four methods are based on estimating the scale-size of the minimum in a hypersurface formed by the weighted sum of the squares of the differences between the model fit and the data as a function of the fit parameters, and are implemented as commonly practiced. The fourth method is also based on the difference between the data and the model, but instead uses Bayesian data analysis and Markov chain Monte Carlo (MCMC) techniques to calculate an uncertainty estimate. Two flare spectra are modeled: one from the Geostationary Operational Environmental Satellite X1.3 class flare of 2005 January 19, and the other from the X4.8 flare of 2002 July 23. We find that the four methods give approximately the same uncertainty estimates for the 2005 January 19 spectral fit parameters, but lead to very different uncertainty estimates for the 2002 July 23 spectral fit. This is because each method implements different analyses of the hypersurface, yielding method-dependent results that can differ greatly depending on the shape of the hypersurface. The hypersurface arising from the 2005 January 19 analysis is consistent with a normal distribution; therefore, the assumptions behind the three non-Bayesian uncertainty estimation methods are satisfied and similar estimates are found. The 2002 July 23 analysis shows that the hypersurface is not consistent with a normal distribution, indicating that the assumptions behind the three non-Bayesian uncertainty estimation methods are not satisfied, leading to differing estimates of the uncertainty. We find that the shape of the hypersurface is crucial in understanding

  9. Parametric X-ray generation using the burst-mode beam at LEBRA and the feasibility of the application

    International Nuclear Information System (INIS)

    At the Laboratory for Electron Beam Research and Application (LEBRA), the parametric X-ray (PXR) beam produced by using the burst-mode beam from the electron linac was observed and the several application experiments were actually performed. In the case of the 64 division mode corresponding to the bunch period of 22.4 ns, the macropulse beam current was approximately one fifth of that of the conventional full bunch mode. The result of the imaging using the PXR beam agrees with the PXR yield proportional to the beam current. Analyzer-based phase-contrast imaging and dispersive X-ray absorption spectroscopy were also carried out using the burst-mode beam. As the result, no serious problem was observed with respect to the X-ray beam quality. Thus, it is expected that the time-resolved experiments with the resolution of 1 ns will be possible using the burst-mode PXR beam. (author)

  10. A Luminous X-Ray Flare from the Nucleus of the Dormant Bulgeless Spiral Galaxy NGC 247

    OpenAIRE

    FENG, HUA; Ho, Luis C.; Kaaret, Philip; Tao, Lian; Yamaoka, Kazutaka; Zhang, Shuo; Grisé, Fabien

    2015-01-01

    NGC 247 is a nearby late-type bulgeless spiral galaxy that contains an inactive nucleus. We report a serendipitous discovery of an X-ray flare from the galaxy center with a luminosity of up to 2 x 10^(39) erg s^(−1) in the 0.3–10 keV band with XMM-Newton. A Chandra observation confirms that the new X-ray source is spatially coincident with the galaxy nucleus. The XMM-Newton data revealed a hard power-law spectrum with a spectral break near 3–4 keV, no pulsations on timescales longer than 150 ...

  11. Analysis of X-ray observations of the 15 June 1973 flare in active region NOAA 131

    International Nuclear Information System (INIS)

    Observations and analyses of the 1B/M3 flare of 15 June, 1973 in active region NOAA 131 (McMath 12379) are presented. The X-ray observations, consisting of broadband photographs and proportional counter data from the Skylab/ATM NASA-MSFC/Aerospace S-056 experiment, are used to infer temperatures, emission measures, and densities for the flaring plasma. The peak temperature from the spatially resolved photographs is 25x106 K, while the temperature from the full-disk proportional counter data is approximately 15x106 K. The density is 3x1010 cm-3. The X-ray flare emission appears to come primarily from two low-lying curvilinear features lying perpendicular to and centered on the line where the photospheric longitudinal magnetic field is zero. Similarities in the preflare and postflare X-ray emission patterns indicate that no large-scale relaxation of the coronal magnetic configuration was observed. Also discussed are Hα and magnetic field observations of the flare and the active region. Finally, results of numerical calculations, including thermal conduction, radiative loss and chromospheric evaporation, are in qualitative agreement with the decay phase observations. (Auth.)

  12. Exposing the Nuclear Burning Ashes of Radius Expansion Type I X-Ray Bursts

    Science.gov (United States)

    Weinberg, Nevin N.; Bildsten, Lars; Schatz, Hendrik

    2006-03-01

    We solve for the evolution of the vertical extent of the convective region of a neutron star atmosphere during a type I X-ray burst. The convective region is well mixed with ashes of nuclear burning, and its extent determines the rise time of the burst light curve. Using a full nuclear reaction network, we show that the maximum vertical extent of the convective region during photospheric radius expansion (RE) bursts can be sufficiently great that (1) some ashes of burning are ejected by the radiation-driven wind during the RE phase and (2) some ashes of burning are exposed at the neutron star surface following the RE phase. We find that ashes with mass numbers in the range A~30-60 are mixed in with the ejected material. We calculate the expected column density of ejected and surface ashes in hydrogen-like states and determine the equivalent widths of the resulting photoionization edges from both the wind and the neutron star surface. We find that these can exceed 100 eV and are potentially detectable. A detection would probe the nuclear burning processes and might enable a measurement of the gravitational redshift of the neutron star. In addition, we find that in bursts with pure helium burning layers, protons from (α, p) reactions cause a rapid onset of the 12C(p, γ)13N(α, p)16O reaction sequence. The sequence bypasses the relatively slow 12C(α, γ)16O reaction and leads to a sudden surge in energy production that is directly observable as a rapid (~millisecond) increase in flux during burst rise.

  13. Using infrared/X-ray flare statistics to probe the emission regions near the event horizon of Sgr A

    Science.gov (United States)

    Dibi, S.; Markoff, S.; Belmont, R.; Malzac, J.; Neilsen, J.; Witzel, G.

    2016-06-01

    The supermassive black hole at the centre of the Galaxy flares at least daily in the infrared (IR) and X-ray bands, yet the process driving these flares is still unknown. So far detailed analysis has only been performed on a few bright flares. In particular, the broadband spectral modelling suffers from a strong lack of simultaneous data. However, new monitoring campaigns now provide data on thousands of flaring events, allowing a statistical analysis of the flare properties. In this paper, we investigate the X-ray and IR flux distributions of the flare events. Using a self-consistent calculation of the particle distribution, we model the statistical properties of the flares. Based on a previous work on single flares, we consider two families of models: pure synchrotron models and synchrotron self-Compton (SSC) models. We investigate the effect of fluctuations in some relevant parameters (e.g. acceleration properties, density, magnetic field) on the flux distributions. The distribution of these parameters is readily derived from the flux distributions observed at different wavelengths. In both scenarios, we find that fluctuations of the power injected in accelerated particles plays a major role. This must be distributed as a power-law (with different indices in each model). In the synchrotron dominated scenario, we derive the most extreme values of the acceleration power required to reproduce the brightest flares. In that model, the distribution of the acceleration slope fluctuations is constrained and in the SSC scenario we constrain the distributions of the correlated magnetic field and flow density variations.

  14. Deka-keV X-ray observations of solar bursts with WATCH/GRANAT: frequency distributions of burst parameters

    DEFF Research Database (Denmark)

    Crosby, N.; Vilmer, N.; Lund, Niels;

    1998-01-01

    Solar flare observations in the deka-keV range are performed by the WATCH experiment on board the GRANAT satellite. The WATCH experiment is presented, including the energy calibration as applied in the present work. The creation of the solar burst catalogue covering two years of observation is...... contributions from a thermal plasma around a few keV. Either a hotter component or a non-thermal population of particles must also be present to produce the observed deka-keV emission. The WATCH data furthermore shows that the relative contributions of these components may change during an event or from event...... to event and that the injection of energy contained in suprathermal electrons may occur throughout an event and not only during the rise phase. For the most energetic WATCH flares simultaneous observations performed by other experiments at higher energies further indicate that non-thermal emission...

  15. Exposing the Nuclear Burning Ashes of Radius Expansion Type I X-ray Bursts

    CERN Document Server

    Weinberg, N N; Schatz, H; Weinberg, Nevin N.; Bildsten, Lars; Schatz, Hendrik

    2006-01-01

    We solve for the evolution of the vertical extent of the convective region of a neutron star atmosphere during a Type I X-ray burst. The convective region is well-mixed with ashes of nuclear burning and its extent determines the rise time of the burst light curve. Using a full nuclear reaction network, we show that the maximum vertical extent of the convective region during photospheric radius expansion (RE) bursts can be sufficiently great that: (1) some ashes of burning are ejected by the radiation driven wind during the RE phase and, (2) some ashes of burning are exposed at the neutron star surface following the RE phase. We find that ashes with mass number A ~ 30 - 60 are mixed in with the ejected material. We calculate the expected column density of ejected and surface ashes in hydrogen-like states and determine the equivalent widths of the resulting photoionization edges from both the wind and neutron star surface. We find that these can exceed 100 eV and are potentially detectable. A detection would pr...

  16. Determining Neutron Star Properties by Fitting Oblate Schwarzschild Waveforms To X-ray Burst Oscillations

    CERN Document Server

    Miller, M Coleman

    2014-01-01

    We have developed sophisticated new Bayesian analysis methods that enable us to estimate quickly the masses and radii of rapidly rotating, oblate neutron stars using the energy-resolved waveforms of their X-ray burst oscillations and to determine the uncertainties in these mass and radius estimates. We demonstrate these methods by generating and analyzing the energy-resolved burst oscillation waveforms that would be produced by a hot spot on various rapidly rotating, oblate stars, using the analytic implementation of the oblate-star Schwarzschild-spacetime (OS) approximation introduced by Morsink et al. 2007. In generating these synthetic data, we assume that 10$^6$ counts have been collected from the hot spot and that the background is $9\\times10^6$ counts. This produces a realistic modulation amplitude and a total number of counts comparable to the number that could be obtained by future space missions, by combining data from many bursts from a given star. We compute the joint posterior distribution of the ...

  17. MAGNETIC NON-POTENTIALITY OF SOLAR ACTIVE REGIONS AND PEAK X-RAY FLUX OF THE ASSOCIATED FLARES

    International Nuclear Information System (INIS)

    Predicting the severity of solar eruptive phenomena such as flares and coronal mass ejections remains a great challenge despite concerted efforts to do so over the past several decades. However, the advent of high-quality vector magnetograms obtained from Hinode (SOT/SP) has increased the possibility of meeting this challenge. In particular, the spatially averaged signed shear angle (SASSA) seems to be a unique parameter for quantifying the non-potentiality of active regions. We demonstrate the usefulness of the SASSA for predicting flare severity. For this purpose, we present case studies of the evolution of magnetic non-potentiality using 115 vector magnetograms of four active regions, namely, ARs NOAA 10930, 10960, 10961, and 10963 during 2006 December 8-15, 2007 June 3-10, 2007 June 28-July 5, and 2007 July 10-17, respectively. The NOAA ARs 10930 and 10960 were very active and produced X and M class flares, respectively, along with many smaller X-ray flares. On the other hand, the NOAA ARs 10961 and 10963 were relatively less active and produced only very small (mostly A- and B-class) flares. For this study, we have used a large number of high-resolution vector magnetograms obtained from Hinode (SOT/SP). Our analysis shows that the peak X-ray flux of the most intense solar flare emanating from the active regions depends on the magnitude of the SASSA at the time of the flare. This finding of the existence of a lower limit of the SASSA for a given class of X-ray flares will be very useful for space weather forecasting. We have also studied another non-potentiality parameter called the mean weighted shear angle (MWSA) of the vector magnetograms along with the SASSA. We find that the MWSA does not show such distinction as the SASSA for upper limits of the GOES X-ray flux of solar flares; however, both the quantities show similar trends during the evolution of all active regions studied.

  18. Constraints on energy release in solar flares from RHESSI and GOES X-ray observations. II. Energetics and energy partition

    Science.gov (United States)

    Warmuth, A.; Mann, G.

    2016-04-01

    Aims: We derive constraints on energy release, transport and conversion processes in solar flares based on a detailed characterization of the physical parameters of both the thermal plasma and the accelerated nonthermal electrons based on X-ray observations. In particular, we address the questions of whether the energy required to heat the thermal plasma can be supplied by nonthermal particles, and how the energetics derived from X-rays compare to the total bolometric radiated energy. Methods: Time series of spectral fits and images for 24 flares ranging from GOES class C3.4 to X17.2 were obtained using RHESSI hard X-ray observations. This has been supplemented by GOES soft X-ray fluxes. In our companion Paper I, we have used this data set to obtain the basic physical parameters for the thermal plasma (using the isothermal approximation) and the injected energetic electrons (assuming the thick-target model). Here, we used this data set to derive the flare energetics, including thermal energy, radiative and conductive energy loss, gravitational and flow energy of the plasma, and kinetic energy of the injected electrons. We studied how the thermal energies compare to the energy in nonthermal electrons, and how the various energetics and energy partition depend on flare importance. Results: All flare energetics show a good to excellent correlation with the peak GOES flux. The gravitational energy of the evaporated plasma and the kinetic energy of plasma flows can be neglected in the discussion of flare energetics. The radiative energy losses are comparable to the maximum thermal energy, while the conductive losses are considerably higher than the maximum thermal energy, especially in weaker flares. The total heating requirement of the hot plasma amounts to ≈50% of the total bolometric energy loss, with the conductive losses as a major contribution. The nonthermal energy input by energetic electrons is not sufficient to account for the total heating requirements of

  19. FLARE-GENERATED TYPE II BURST WITHOUT ASSOCIATED CORONAL MASS EJECTION

    Energy Technology Data Exchange (ETDEWEB)

    Magdalenic, J.; Marque, C.; Zhukov, A. N. [Solar-Terrestrial Center of Excellence, SIDC, Royal Observatory of Belgium, Avenue Circulaire 3, B-1180 Brussels (Belgium); Vrsnak, B. [Hvar Observatory, Faculty of Geodesy, Kaciceva 26, HR-10000 Zagreb (Croatia); Veronig, A., E-mail: Jasmina.Magdalenic@oma.be [IGAM/Kanzelhoehe Observatory, Institut of Physics, Universitaet Graz, Universitaetsplatz 5, A-8010 Graz (Austria)

    2012-02-20

    We present a study of the solar coronal shock wave on 2005 November 14 associated with the GOES M3.9 flare that occurred close to the east limb (S06 Degree-Sign E60 Degree-Sign ). The shock signature, a type II radio burst, had an unusually high starting frequency of about 800 MHz, indicating that the shock was formed at a rather low height. The position of the radio source, the direction of the shock wave propagation, and the coronal electron density were estimated using Nancay Radioheliograph observations and the dynamic spectrum of the Green Bank Solar Radio Burst Spectrometer. The soft X-ray, H{alpha}, and Reuven Ramaty High Energy Solar Spectroscopic Imager observations show that the flare was compact, very impulsive, and of a rather high density and temperature, indicating a strong and impulsive increase of pressure in a small flare loop. The close association of the shock wave initiation with the impulsive energy release suggests that the impulsive increase of the pressure in the flare was the source of the shock wave. This is supported by the fact that, contrary to the majority of events studied previously, no coronal mass ejection was detected in association with the shock wave, although the corresponding flare occurred close to the limb.

  20. Reconciliation of Waiting Time Statistics of Solar Flares Observed in Hard X-Rays

    CERN Document Server

    Aschwanden, Markus J

    2010-01-01

    We study the waiting time distributions of solar flares observed in hard X-rays with ISEE-3/ICE, HXRBS/SMM, WATCH/GRANAT, BATSE/CGRO, and RHESSI. Although discordant results and interpretations have been published earlier, based on relatively small ranges ($< 2$ decades) of waiting times, we find that all observed distributions, spanning over 6 decades of waiting times ($\\Delta t \\approx 10^{-3}- 10^3$ hrs), can be reconciled with a single distribution function, $N(\\Delta t) \\propto \\lambda_0 (1 + \\lambda_0 \\Delta t)^{-2}$, which has a powerlaw slope of $p \\approx 2.0$ at large waiting times ($\\Delta t \\approx 1-1000$ hrs) and flattens out at short waiting times $\\Delta t \\lapprox \\Delta t_0 = 1/\\lambda_0$. We find a consistent breakpoint at $\\Delta t_0 = 1/\\lambda_0 = 0.80\\pm0.14$ hours from the WATCH, HXRBS, BATSE, and RHESSI data. The distribution of waiting times is invariant for sampling with different flux thresholds, while the mean waiting time scales reciprocically with the number of detected event...

  1. UFCORIN: A fully automated predictor of solar flares in GOES X-ray flux

    Science.gov (United States)

    Muranushi, Takayuki; Shibayama, Takuya; Muranushi, Yuko Hada; Isobe, Hiroaki; Nemoto, Shigeru; Komazaki, Kenji; Shibata, Kazunari

    2015-11-01

    We have developed UFCORIN, a platform for studying and automating space weather prediction. Using our system we have tested 6160 different combinations of Solar Dynamic Observatory/Helioseismic and Magnetic Imager data as input data, and simulated the prediction of GOES X-ray flux for 2 years (2011-2012) with 1 h cadence. We have found that direct comparison of the true skill statistic (TSS) from small cross-validation sets is ill posed and used the standard scores (z) of the TSS to compare the performance of the various prediction strategies. The z of a strategy is a stochastic variable of the stochastically chosen cross-validation data set, and the z for the three strategies best at predicting X-, ≥M-, and ≥C-class flares are better than the average z of the 6160 strategies by 2.3σ, 2.1σ, and 3.8σ confidence levels, respectively. The best three TSS values were 0.75 ± 0.07, 0.48 ± 0.02, and 0.56 ± 0.04, respectively.

  2. On the variation of solar flare coronal X-ray source sizes with energy

    Energy Technology Data Exchange (ETDEWEB)

    Jeffrey, Natasha L. S.; Kontar, Eduard P.; Bian, Nicolas H. [School of Physics and Astronomy, University of Glasgow, G12 8QQ Glasgow (United Kingdom); Emslie, A. Gordon, E-mail: n.jeffrey@physics.gla.ac.uk [Department of Physics and Astronomy, Western Kentucky University, Bowling Green, KY 42101 (United States)

    2014-05-20

    Observations with RHESSI have enabled the detailed study of the structure of dense hard X-ray coronal sources in solar flares. The variation of source extent with electron energy has been discussed in the context of streaming of non-thermal particles in a one-dimensional cold target model and the results used to constrain both the physical extent of, and density within, the electron acceleration region. Here, we extend this investigation to a more physically realistic model of electron transport that takes into account the finite temperature of the ambient plasma, the initial pitch angle distribution of the accelerated electrons, and the effects of collisional pitch angle scattering. The finite temperature results in the thermal diffusion of electrons, which leads to the observationally inferred value of the acceleration region volume being an overestimate of its true value. The different directions of the electron trajectories, a consequence of both the non-zero injection pitch angle and scattering within the target, cause the projected propagation distance parallel to the guiding magnetic field to be reduced, so that a one-dimensional interpretation can overestimate the actual density by a factor of up to ∼6. The implications of these results for the determination of acceleration region properties (specific acceleration rate, filling factor, etc.) are discussed.

  3. On the variation of solar flare coronal x-ray source sizes with energy

    CERN Document Server

    Jeffrey, Natasha L S; Bian, Nicolas H; Emslie, A Gordon

    2014-01-01

    Observations with {\\em RHESSI} have enabled the detailed study of the structure of dense hard X-ray coronal sources in solar flares. The variation of source extent with electron energy has been discussed in the context of streaming of non-thermal particles in a one-dimensional cold-target model, and the results used to constrain both the physical extent of, and density within, the electron acceleration region. Here we extend this investigation to a more physically realistic model of electron transport that takes into account the finite temperature of the ambient plasma, the initial pitch-angle distribution of the accelerated electrons, and the effects of collisional pitch-angle scattering. The finite temperature results in the thermal diffusion of electrons, that leads to the observationally-inferred value of the acceleration region volume being an overestimate of its true value. The different directions of the electron trajectories, a consequence of both the non-zero injection pitch-angle and scattering with...

  4. New soft gamma-ray bursts in the BATSE records and spectral properties of X-ray rich bursts

    CERN Document Server

    Tikhomirova, Y; Kozyreva, A V; Poutanen, J; Tikhomirova, Yana; Stern, Boris; Kozyreva, Alexandra; Poutanen, Juri

    2006-01-01

    A population of X-ray dominated gamma-ray bursts (GRBs) observed by Ginga, BeppoSax and Hete-2 should be represented in the BATSE data as presumably soft bursts. We have performed a search for soft GRBs in the BATSE records in the 25--100 keV energy band. A softness of a burst spectrum can be a reason why it has been missed by the on-board procedure and previous searches for untriggered GRBs tuned to 50--300 keV range. We have found a surprisingly small number (~20/yr down to 0.1 ph cm$^{-2}$ s$^{-1}$) of soft GRBs where the count rate is dominated by 25--50 keV energy channel. This fact as well as the analysis of HETE-2 and common BeppoSAX/BATSE GRBs indicates that the majority of GRBs with a low Epeak has a relatively hard tail with the high-energy power-law photon index >-3. An exponential cutoff in GRB spectra below 20 keV may be a distinguishing feature separating non-GRB events.

  5. A time - luminosity correlation for Gamma Ray Bursts in the X - rays

    CERN Document Server

    Dainotti, M G; Capozziello, S

    2008-01-01

    Gamma ray bursts (GRBs) have recently attracted much attention as a possible way to extend the Hubble diagram to very high redshift. However, the large scatter in their intrinsic properties prevents directly using them as distance indicator so that the hunt is open for a relation involving an observable property to standardize GRBs in the same way as the Phillips law makes it possible to use Type Ia Supernovae (SNeIa) as standardizable candles. We use here the data on the X - ray decay curve and spectral index of a sample of GRBs observed with the Swift satellite. These data are used as input to a Bayesian statistical analysis looking for a correlation between the X - ray luminosity L_X(T_a) and the time constant T_a of the afterglow curve. We find a linear relation between \\log{[L_X(T_a)]} and \\log{[T_a/(1+z)]} with an intrinsic scatter sigma_{int} = 0.33 comparable to previously reported relations. Remarkably, both the slope and the intrinsic scatter are almost independent on the matter density Omega_M and ...

  6. Absorption features in the spectra of X-ray bursting neutron stars

    CERN Document Server

    Rauch, Thomas; Werner, Klaus

    2008-01-01

    The discovery of photospheric absorption lines in XMM-Newton spectra of the X-ray bursting neutron star in EXO0748-676 by Cottam and collaborators allows us to constrain the neutron star mass-radius ratio from the measured gravitational redshift. A radius of R=9-12km for a plausible mass range of M=1.4-1.8Msun was derived by these authors. It has been claimed that the absorption features stem from gravitationally redshifted (z=0.35) n=2-3 lines of H- and He-like iron. We investigate this identification and search for alternatives. We compute LTE and non-LTE neutron-star model atmospheres and detailed synthetic spectra for a wide range of effective temperatures (effective temperatures of 1 - 20MK) and different chemical compositions. We are unable to confirm the identification of the absorption features in the X-ray spectrum of EXO0748-676 as n=2-3 lines of H- and He-like iron (Fe XXVI and Fe XXV). These are subordinate lines that are predicted by our models to be too weak at any effective temperature. It is m...

  7. Windowless microfluidic platform based on capillary burst valves for high intensity x-ray measurements

    International Nuclear Information System (INIS)

    We propose and describe a microfluidic system for high intensity x-ray measurements. The required open access to a microfluidic channel is provided by an out-of-plane capillary burst valve (CBV). The functionality of the out-of-plane CBV is characterized with respect to the diameter of the windowless access hole, ranging from 10 to 130 μm. Maximum driving pressures from 22 to 280 mbar corresponding to refresh rates of the exposed sample from 300 Hz to 54 kHz is demonstrated. The microfluidic system is tested at beamline ID09b at the ESRF synchrotron radiation facility in Grenoble, and x-ray scattering measurements are shown to be feasible and to require only very limited amounts of sample, <1 ml/h of measurements without recapturing of sample. With small adjustments of the present chip design, scattering angles up to 30 deg. can be achieved without shadowing effects and integration on-chip mixing and spectroscopy appears straightforward.

  8. X-ray bursting neutron star atmosphere models: spectra and color corrections

    CERN Document Server

    Suleimanov, V; Werner, K

    2010-01-01

    X-ray bursting neutron stars in low mass X-ray binaries constitute an appropriate source class to constrain masses and radii of neutron stars, but a sufficiently extended set of corresponding model atmospheres is necessary for these investigations. We computed such a set of model atmospheres and emergent spectra in a plane-parallel, hydrostatic, and LTE approximation with Compton scattering taken into account. The models were calculated for six different chemical compositions: pure hydrogen and pure helium atmospheres, and atmospheres with solar mix of hydrogen and helium, and various heavy element abundances Z = 1, 0.3, 0.1, and 0.01 Z_sun. For each chemical composition the models are computed for three values of surface gravity, log g =14.0, 14.3, and 14.6, and for 20 values of the luminosity in units of the Eddington luminosity, L/L_Edd, in the range 0.001--0.98. The emergent spectra of all models are redshifted and fitted by a diluted blackbody in the RXTE/PCA 3--20 keV energy band, and corresponding valu...

  9. X-raying Extended emission and rapid decay of short gamma-ray bursts

    CERN Document Server

    Kagawa, Yasuaki; Sawano, Tatsuya; Toyanago, Asuka; Nakamura, Takashi; Takahashi, Keitaro; Kashiyama, Kazumi; Ioka, Kunihito

    2015-01-01

    Extended emission is a mystery in short gamma-ray bursts (SGRBs). By making time resolved spectral analyses of brightest eight events observed by {\\it Swift} XRT, we obviously classify the early X-ray emission of SGRBs into two types. One is the extended emission with exponentially rapid decay, which shows significant spectral softening during hundreds seconds since the SGRB trigger and is also detected by {\\it Swift}-BAT. The other is a dim afterglow only showing power-law decay over $10^4$ s. The correlations between the temporal decay and spectral indices of the extended emissions are inconsistent with the $\\alpha$-$\\beta$ correlation expected for the high-latitude curvature emission from a uniform jet. The observed too-rapid decay suggests the emission from a photosphere or a patchy surface, and manifests the stopping central engine via such as magnetic reconnection at the black hole.

  10. Dynamical structure of solar radio burst type III as evidence of energy of solar flares

    Science.gov (United States)

    Hamidi, Zety Sharizat Binti

    2013-11-01

    Observations of low frequency solar type III radio bursts associated with the ejection of plasma oscillations localized disturbance is due to excitation atoms in the plasma frequency incoherent radiations play a dominant role at the meter and decimeter wavelengths. Here, we report the results of the dynamical structure of solar flare type III that occurred on 9th March 2012 at National Space Centre, Sg Lang, Selangor, Malaysia by using the CALLISTO system. These bursts are associated with solar flare type M6 which suddenly ejected in the active region AR 1429 starting at 03:32 UT and ending at 05:00 UT with the peak at 04:12 UT. The observation showed an initial strong burst occurred due to strong signal at the beginning of the phase. We also found that both solar burst and flares tend to be a numerous on the same day and probability of chance coincidence is high. It is clearly seen that an impulsive lace burst was detected at 4:24 UT and it is more plausible that the energies are confined to the top of the loop when we compared with X-ray results. Associated with this event was type II with velocities 1285 km/s and type IV radio sweeps along with a full halo Coronal Mass Ejections (CMEs) first seen in SOHO/LASCO C2 imagery at 09/0426 Z. We concluded that the significance of study solar burst type III lies in the fact that the emission at decimetric wavelength comes from the role of magnetic field in active region that may provide the key to the energy release mechanism in a flare.

  11. THE RELATIONSHIP BETWEEN HARD X-RAY PULSE TIMINGS AND THE LOCATIONS OF FOOTPOINT SOURCES DURING SOLAR FLARES

    International Nuclear Information System (INIS)

    The cause of quasi-periodic pulsations in solar flares remains the subject of debate. Recently, Nakariakov and Zimovets proposed a new model suggesting that, in two-ribbon flares, such pulsations could be explained by propagating slow waves. These waves may travel obliquely to the magnetic field, reflect in the chromosphere, and constructively interfere at a spatially separate site in the corona, leading to quasi-periodic reconnection events progressing along the flaring arcade. Such a slow wave regime would have certain observational characteristics. We search for evidence of this phenomenon during a selection of two-ribbon flares observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager, Solar and Heliospheric Observatory, and Transition Region and Coronal Explorer; the flares of 2002 November 9, 2005 January 19, and 2005 August 22. We were not able to observe a clear correlation between hard X-ray footpoint separations and pulse timings during these events. Also, the motion of hard X-ray footpoints is shown to be continuous within the observational error, whereas a discontinuous motion might be anticipated in the slow wave model. Finally, we find that for a preferential slow wave propagation angle of 25°-28° that is expected for the fastest waves, the velocities of the hard X-ray footpoints lead to estimated pulse periods and ribbon lengths significantly larger than the measured values. Hence, for the three events studied, we conclude that the observational characteristics cannot be easily explained via the Nakariakov and Zimovets propagating slow wave model when only angles of 25°-28° are considered. We provide suggested flare parameters to optimize future studies of this kind.

  12. The influence of accretion geometry on the spectral evolution during thermonuclear (type-I) X-ray bursts

    CERN Document Server

    Kajava, Jari J E; Latvala, Outi-Marja; Pursiainen, Miika; Poutanen, Juri; Suleimanov, Valery F; Revnivtsev, Mikhail G; Kuulkers, Erik; Galloway, Duncan K

    2014-01-01

    Neutron star (NS) masses and radii can be estimated from observations of photospheric radius-expansion X-ray bursts, provided the chemical composition of the photosphere, the spectral colour-correction factors in the observed luminosity range, and the emission area during the bursts are known. By analysing 246 X-ray bursts observed by the Rossi X-ray Timing Explorer from 11 low-mass X-ray binaries, we find a dependence between the persistent spectral properties and the time evolution of the black body normalisation during the bursts. All NS atmosphere models predict that the colour-correction factor decreases in the early cooling phase when the luminosity first drops below the limiting Eddington value, leading to a characteristic pattern of variability in the measured blackbody normalisation. However, the model predictions agree with the observations for most bursts occurring in hard, low-luminosity, 'island' spectral states, but rarely during soft, high-luminosity, 'banana' states. The observed behaviour may...

  13. Impulsive solar X-ray bursts. 4: Polarization, directivity and spectrum of the reflected and total bremsstrahlung radiation from a beam of electrons directed toward the photosphere

    Science.gov (United States)

    Langer, S. H.; Petrosian, V.

    1976-01-01

    A Monte Carlo method is described for evaluation of the spectrum, directivity and polarization of X-rays diffusely reflected from stellar photospheres. the accuracy of the technique is evaluated through comparison with analytic results. Using the characteristics of the incident X-rays of the model for solar X-ray flares, the spectrum, directivity and polarization of the reflected and the total X-ray fluxes are evaluated. The results are compared with observations.

  14. The 2010 May Flaring Episode of Cygnus X-3 in Radio, X-Rays, and gamma-Rays

    Science.gov (United States)

    Williams, Peter K. G.; Tomsick, John A.; Bodaghee, Arash; Bower, Geoffrey C.; Pooley, Guy G.; Pottschmidt, Katja; Rodriguez, Jerome; Wilms, Joern; Migliari, Simone; Trushkin, Sergei A.

    2011-01-01

    In 2009, Cygnus X-3 (Cyg X-3) became the first microquasar to be detected in the GeV gamma-ray regime, via the satellites Fermi and AGILE. The addition of this new band to the observational toolbox holds promise for building a more detailed understanding of the relativistic jets of this and other systems. We present a rich dataset of radio, hard and soft X-ray, and gamma-ray observations of Cyg X-3 made during a flaring episode in 2010 May. We detect a approx.3-d softening and recovery of the X-ray emission, followed almost immediately by a approx.1-Jy radio flare at 15 GHz, followed by a 4.3sigma gamma-ray flare (E > 100 MeV) approx.1.5 d later. The radio sampling is sparse, but we use archival data to argue that it is unlikely the gamma-ray flare was followed by any significant unobserved radio flares. In this case, the sequencing of the observed events is difficult to explain in a model in which the gamma-ray emission is due to inverse Compton scattering of the companion star's radiation field. Our observations suggest that other mechanisms may also be responsible for gamma-ray emission from Cyg X-3.

  15. THE 2010 MAY FLARING EPISODE OF CYGNUS X-3 IN RADIO, X-RAYS, AND γ-RAYS

    International Nuclear Information System (INIS)

    In 2009, Cygnus X-3 (Cyg X-3) became the first microquasar to be detected in the GeV γ-ray regime, via the satellites Fermi and AGILE. The addition of this new band to the observational toolbox holds promise for building a more detailed understanding of the relativistic jets of this and other systems. We present a rich data set of radio, hard and soft X-ray, and γ-ray observations of Cyg X-3 made during a flaring episode in 2010 May. We detect a ∼3 day softening and recovery of the X-ray emission, followed almost immediately by a ∼1 Jy radio flare at 15 GHz, followed by a 4.3σ γ-ray flare (E > 100 MeV) ∼1.5 days later. The radio sampling is sparse, but we use archival data to argue that it is unlikely the γ-ray flare was followed by any significant unobserved radio flares. In this case, the sequencing of the observed events is difficult to explain in a model in which the γ-ray emission is due to inverse Compton scattering of the companion star's radiation field. Our observations suggest that other mechanisms may also be responsible for γ-ray emission from Cyg X-3.

  16. HARD X-RAY FOOTPOINT SIZES AND POSITIONS AS DIAGNOSTICS OF FLARE ACCELERATED ENERGETIC ELECTRONS IN THE LOW SOLAR ATMOSPHERE

    International Nuclear Information System (INIS)

    The hard X-ray (HXR) emission in solar flares comes almost exclusively from a very small part of the flaring region, the footpoints of magnetic loops. Using RHESSI observations of solar flare footpoints, we determine the radial positions and sizes of footpoints as a function of energy in six near-limb events to investigate the transport of flare accelerated electrons and the properties of the chromosphere. HXR visibility forward fitting allows us to find the positions/heights and the sizes of HXR footpoints along and perpendicular to the magnetic field of the flaring loop at different energies in the HXR range. We show that in half of the analyzed events, a clear trend of decreasing height of the sources with energy is found. Assuming collisional thick-target transport, HXR sources are located between 600 and 1200 km above the photosphere for photon energies between 120 and 25 keV, respectively. In the other events, the position as a function of energy is constant within the uncertainties. The vertical sizes (along the path of electron propagation) range from 1.3 to 8 arcsec which is up to a factor four larger than predicted by the thick-target model even in events where the positions/heights of HXR sources are consistent with the collisional thick-target model. Magnetic mirroring, collisional pitch-angle scattering, and X-ray albedo are discussed as potential explanations of the findings.

  17. Discovery of a wandering radio jet base after a large X-ray flare in the blazar Markarian 421

    CERN Document Server

    Niinuma, K; Doi, A; Hada, K; Nagai, H; Koyama, S

    2015-01-01

    We investigate the location of the radio jet bases ("radio cores") of blazars in radio images, and their stationarity by means of dense very long baseline interferometry (VLBI) observations. In order to measure the position of a radio core, we conducted 12 epoch astrometric observation of the blazar Markarian 421 with the VLBI Exploration of Radio Astrometry at 22 GHz immediately after a large X-ray flare, which occurred in the middle of 2011 September. For the first time, we find that the radio core is not stationary but rather changes its location toward 0.5 mas downstream. This angular scale corresponds to the de-projected length of a scale of $10^5$ Schwarzschild radii (Rs) at the distance of Markarian~421. This radio-core wandering may be a new type of manifestation associated with the phenomena of large X-ray flares.

  18. Comparing SSN Index to X-ray Flare and Coronal Mass Ejection Rates from Solar Cycles 22-24

    OpenAIRE

    Winter, Lisa M.; Pernak, Rick; Balasubramaniam, K. S.

    2016-01-01

    The newly revised sunspot number series allows for placing historical geoeffective storms in the context of several hundred years of solar activity. Using statistical analyses of the Geostationary Operational Environmental Satellites (GOES) X-ray observations from the past ~30 years and the Solar and Heliospheric Observatory (SOHO) Large Angle and Spectrometric Coronagraph (LASCO) Coronal Mass Ejection (CME) catalog (1996-present), we present sunspot-number-dependent flare and CME rates. In p...

  19. Compton backscattered and primary x-rays from solar flares: angle dependent Green's function correction for photospheric albedo

    OpenAIRE

    Kontar, E.P.; MacKinnon, A.L.; Schwartz, R. A.; Brown, J. C.

    2006-01-01

    The observed hard X-ray (HXR) flux spectrum I(ε) from solar flares is a combination of primary bremsstrahlung photons Ip(ε) with a spectrally modified component from photospheric Compton backscatter of downward primary emission. The latter can be significant, distorting or hiding the true features of the primary spectrum which are key diagnostics for acceleration and propagation of high energy electrons and of their energy budget. For the first time in solar physics, we use a Green'...

  20. X-ray sources and magnetic reconnection in the X3.9 flare of 2003 November 3

    Czech Academy of Sciences Publication Activity Database

    Veronig, A.; Karlický, Marian; Vršnak, B.; Temmer, M.; Magdalenic, J.; Dennis, B. R.; Otruba, W.; Pötzi, W.

    2006-01-01

    Roč. 446, č. 2 (2006), s. 675-690. ISSN 0004-6361 R&D Projects: GA AV ČR IAA3003202; GA ČR GA205/04/0358 Institutional research plan: CEZ:AV0Z10030501 Keywords : solar flares * magnetic reconnection * X-ray sources Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 3.971, year: 2006

  1. Radio Spectral Evolution of an X-ray Poor Impulsive Solar Flare: Implications for Plasma Heating and Electron Acceleration

    CERN Document Server

    Bastian, T S; Gary, D E

    2007-01-01

    We present radio and X-ray observations of an impulsive solar flare that was moderately intense in microwaves, yet showed very meager EUV and X-ray emission. The flare occurred on 2001 Oct 24 and was well-observed at radio wavelengths by the Nobeyama Radioheliograph (NoRH), the Nobeyama Radio Polarimeters (NoRP), and by the Owens Valley Solar Array (OVSA). It was also observed in EUV and X-ray wavelength bands by the TRACE, GOES, and Yohkoh satellites. We find that the impulsive onset of the radio emission is progressively delayed with increasing frequency relative to the onset of hard X-ray emission. In contrast, the time of flux density maximum is progressively delayed with decreasing frequency. The decay phase is independent of radio frequency. The simple source morphology and the excellent spectral coverage at radio wavelengths allowed us to employ a nonlinear chi-squared minimization scheme to fit the time series of radio spectra to a source model that accounts for the observed radio emission in terms of...

  2. Analysis of Intermittency in Submillimeter Radio and Hard X-Ray Data During the Impulsive Phase of a Solar Flare

    Science.gov (United States)

    Giménez de Castro, G.; Simões, P. J. A.; Raulin, J.-P.; Guimarães, O. M.

    2016-08-01

    We present an analysis of intermittent processes occurring during the impulsive phase of the flare SOL2012-03-13, using hard X-rays and submillimeter radio data. Intermittency is a key characteristic in turbulent plasmas and has so far only been analyzed for hard X-ray data. Since in a typical flare the same accelerated electron population is believed to produce both hard X-rays and gyrosynchrotron radiation, we compare the two time profiles by searching for intermittency signatures. For this, we define a cross-wavelet power spectrum, which is used to obtain the local intermittency measure, or {LIM}. When greater than three, the square {LIM} coefficients indicate a local intermittent process. The {LIM}2 coefficient distribution in time and scale helps to identify avalanche or cascade energy release processes. We find two different and well-separated intermittent behaviors in the submillimeter data: for scales greater than 20 s, a broad distribution during the rising and maximum phases of the emission seems to favor a cascade process; for scales below 1 s, short pulses centered on the peak time are representative of avalanches. When applying the same analysis to hard X-rays, we find that only the scales above 10 s produce a distribution related to a cascade energy fragmentation. Our results suggest that different acceleration mechanisms are responsible for tens of keV and MeV energy ranges of electrons.

  3. The 2006-2007 Active Phase of Anomalous X-ray Pulsar 4U 0142+61: Radiative and Timing Changes, Bursts, and Burst Spectral Features

    CERN Document Server

    Gavriil, Fotis P; Kaspi, Victoria M

    2009-01-01

    After at least 6 years of quiescence, Anomalous X-ray Pulsar (AXP) 4U 0142+61 entered an active phase in 2006 March that lasted several months and included six X-ray bursts as well as many changes in the persistent X-ray emission. The bursts, the first seen from this AXP in >11 years of Rossi X-ray Timing Explorer monitoring, all occurred in the interval between 2006 April 6 and 2007 February 7. The burst durations ranged from 8-3x10^3 s. The first five burst spectra are well modeled by blackbodies, with temperatures kT ~ 2-6 keV. However, the sixth burst had a complicated spectrum that is well characterized by a blackbody plus three emission features whose amplitude varied throughout the burst. The most prominent feature was at 14.0 keV. Upon entry into the active phase the pulsar showed a significant change in pulse morphology and a likely timing glitch. The glitch had a total frequency jump of 1.9+/-0.4 x 10^-7 Hz, which recovered with a decay time of 17+/-2 days by more than the initial jump, implying a n...

  4. IMPULSIVE ACCELERATION OF CORONAL MASS EJECTIONS. II. RELATION TO SOFT X-RAY FLARES AND FILAMENT ERUPTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Bein, B. M.; Berkebile-Stoiser, S.; Veronig, A. M.; Temmer, M. [Kanzelhoehe Observatory-IGAM, Institute of Physics, University of Graz, Universitaetsplatz 5, A-8010 Graz (Austria); Vrsnak, B. [Hvar Observatory, Faculty of Geodesy, University of Zagreb, Kaciceva 26, HR-10000 Zagreb (Croatia)

    2012-08-10

    Using high time cadence images from the STEREO EUVI, COR1, and COR2 instruments, we derived detailed kinematics of the main acceleration stage for a sample of 95 coronal mass ejections (CMEs) in comparison with associated flares and filament eruptions. We found that CMEs associated with flares reveal on average significantly higher peak accelerations and lower acceleration phase durations, initiation heights, and heights, at which they reach their peak velocities and peak accelerations. This means that CMEs that are associated with flares are characterized by higher and more impulsive accelerations and originate from lower in the corona where the magnetic field is stronger. For CMEs that are associated with filament eruptions we found only for the CME peak acceleration significantly lower values than for events that were not associated with filament eruptions. The flare rise time was found to be positively correlated with the CME acceleration duration and negatively correlated with the CME peak acceleration. For the majority of the events the CME acceleration starts before the flare onset (for 75% of the events) and the CME acceleration ends after the soft X-ray (SXR) peak time (for 77% of the events). In {approx}60% of the events, the time difference between the peak time of the flare SXR flux derivative and the peak time of the CME acceleration is smaller than {+-}5 minutes, which hints at a feedback relationship between the CME acceleration and the energy release in the associated flare due to magnetic reconnection.

  5. Simultaneous H.E.S.S. and Chandra observations of Sgr A* during an X-ray flare

    CERN Document Server

    Hinton, Jim; Bühler, Rolf; Pühlhofer, Gerd; Wagner, Stefan

    2007-01-01

    The rapidly varying non-thermal X-ray emission observed from Sgr A* points to particle acceleration taking place close to the supermassive black hole. The TeV gamma-ray source HESS J1745-290 is coincident with Sgr A* and may be closely related to the X-ray emission. Simultaneous X-ray and TeV observations are required to elucidate the relationship between these two objects. Here we report on joint H.E.S.S./Chandra observations in July 2005, during which an X-ray flare was detected. Despite a factor >10 increase in the X-ray flux of Sgr A*, no evidence is found for an increase in the TeV gamma-ray flux. We find that an increase of the gamma-ray flux of a factor 2 or greater can be excluded at a confidence level of 99%. This finding disfavours scenarios in which the bulk of the gamma-ray emission observed is produced close to Sgr A*.

  6. Spatially resolved hard X-ray polarization in solar flares: effects of Compton scattering and bremsstrahlung

    Science.gov (United States)

    Jeffrey, N. L. S.; Kontar, E. P.

    2011-12-01

    Aims: We study the polarization of hard X-ray (HXR) sources in the solar atmosphere, including Compton backscattering of photons in the photosphere (the albedo effect) and the spatial distribution of polarization across the source. Methods: HXR photon polarization and spectra produced via electron-ion bremsstrahlung emission are calculated from various electron distributions typical for solar flares. Compton scattering and photoelectric absorption are then modelled using Monte Carlo simulations of photon transport in the photosphere to study the observed (primary and albedo) sources. Polarization maps across HXR sources (primary and albedo components) for each of the modelled electron distributions are calculated at various source locations from the solar centre to the limb. Results: We show that Compton scattering produces a distinct polarization variation across the albedo patch at peak albedo energies of 20-50 keV for all anisotropies modelled. The results show that there are distinct spatial polarization changes in both the radial and perpendicular to radial directions across the extent of the HXR source at a given disk location. In the radial direction, the polarization magnitude and direction at specific positions along the HXR source will either increase or decrease with increased photon distribution directivity towards the photosphere. We also show how high electron cutoff energies influence the direction of polarization at above ~100 keV. Conclusions: Spatially resolved HXR polarization measurements can provide important information about the directivity and energetics of the electron distribution. Our results indicate the preferred angular resolution of polarization measurements required to distinguish between the scattered and primary components. We also show how spatially resolved polarization measurements could be used to probe the emission pattern of an HXR source, using both the magnitude and the direction of the polarization.

  7. Wind, jet, hybrid corona and hard X-ray flares: multiwavelength evolution of GRO J1655-40 during the 2005 outburst rise

    CERN Document Server

    Kalemci, E; Maccarone, T J; Dincer, T; Russell, T D; Bailyn, C; Tomsick, J A

    2016-01-01

    We have investigated the complex multiwavelength evolution of GRO J1655-40 during the rise of its 2005 outburst. We detected two hard X-ray flares, the first one during the transition from the soft state to the ultra-soft state, and the second one in the ultra-soft state. The first X-ray flare coincided with an optically thin radio flare. We also observed a hint of increased radio emission during the second X-ray flare. To explain the hard flares without invoking a secondary emission component, we fit the entire data set with the eqpair model. This single, hybrid Comptonization model sufficiently fits the data even during the hard X-ray flares if we allow reflection fractions greater than unity. In this case, the hard X-ray flares correspond to a Comptonizing corona dominated by non-thermal electrons. The fits also require absorption features in the soft and ultra-soft state which are likely due to a wind. In this work we show that the wind and the optically thin radio flare co-exist. Finally, we have also in...

  8. Constraints on energy release in solar flares from RHESSI and GOES X-ray observations. I. Physical parameters and scalings

    Science.gov (United States)

    Warmuth, A.; Mann, G.

    2016-04-01

    Aims: We constrain energy release and particle acceleration processes in solar flares by means of comprehensively characterizing the physical parameters of both the thermal plasma and the accelerated nonthermal particles using X-ray data. Our aim is to bridge the gap between detailed case studies and large statistical studies. Methods: We obtained time series of spectral fits and images for 24 flares ranging from GOES class C3.4 to X17.2 using RHESSI hard X-ray observations. These data were used to derive basic physical parameters for the thermal plasma (using the isothermal approximation) and the injected nonthermal electrons (assuming the thick-target model). For the thermal component, this was supplemented by GOES soft X-ray data. We derived the ranges and distributions of the various parameters, the scaling with flare importance, and the relation between thermal parameters derived from RHESSI and GOES. Finally, we investigated the relation between thermal and nonthermal parameters. Results: Temperature and emission measure of the thermal plasma are strongly correlated with the peak GOES X-ray flux. Higher emission measures result both from a larger source volume and a higher density, with the latter effect being more important. RHESSI consistently gives higher temperatures and lower emission measures than GOES does, which is a signature of a multithermal plasma. The discrepancy between RHESSI and GOES is particularly pronounced in the early flare phase, when the thermal X-ray sources tend to be large and located higher in the corona. The energy input rate by nonthermal electrons is correlated with temperature and with the increase rate of emission measure and thermal energy. Conclusions: The derived relations between RHESSI- and GOES-derived thermal parameters and the relation between thermal parameters and energy input by nonthermal electrons are consistent with a two-component model of the thermal flare plasma. Both RHESSI and GOES observe a cooler plasma

  9. NuSTAR observations of X-ray bursts from the magnetar 1E 1048.1–5937

    International Nuclear Information System (INIS)

    We report the detection of eight bright X-ray bursts from the 6.5 s magnetar 1E 1048.1–5937, during a 2013 July observation campaign with the Nuclear Spectroscopic Telescope Array. We study the morphological and spectral properties of these bursts and their evolution with time. The bursts resulted in count rate increases by orders of magnitude, sometimes limited by the detector dead time, and showed blackbody spectra with kT ∼ 6-8 keV in the T90 duration of 1-4 s, similar to earlier bursts detected from the source. We find that the spectra during the tail of the bursts can be modeled with an absorbed blackbody with temperature decreasing with flux. The burst flux decays followed a power law of index 0.8-0.9. In the burst tail spectra, we detect a ∼13 keV emission feature, similar to those reported in previous bursts from this source as well as from other magnetars observed with the Rossi X-ray Timing Explorer. We explore possible origins of the spectral feature such as proton cyclotron emission, which implies a magnetic field strength of B ∼ 2 × 1015 G in the emission region. However, the consistency of the energy of the feature in different objects requires further explanation.

  10. X-Ray Reflection of Thermonuclear Bursts from Neutron Stars: Constraining Flames with RXTE and an Outlook on NICER

    Science.gov (United States)

    Keek, Laurens

    2016-04-01

    Thermonuclear X-ray bursts observed from accreting neutron stars are employed to study, e.g., the nuclear physics of rare isotopes and the dense matter equation of state. Recent observations indicate that bursts strongly affect their accretion environment, and reprocessed burst emission may reflect off the inner accretion disk. The spectra of the short (10-100s) bursts are, however, of insufficient quality to accurately separate the neutron star signal from accretion disk emission and burst reflection. Only for two rare "superbursts" with durations of several hours did RXTE/PCA spectra show burst reflection signatures. We discuss the case of 4U 1636-536, where the reflection signal traced the evolution of the ionization state of the inner disk. Our simulations show that a large reflection fraction may indicate that the disk puffs up due to burst irradiation. After separating the direct burst emission from reflection, we show that the rise of the superburst light curve is shaped by a stalling carbon flame. In the near future, the Neutron Star Interior Composition ExploreR (NICER) will have a band-pass that extends below 2 keV, where reflection dominates the burst spectrum, and which was not probed by RXTE. Therefore, NICER will be able to detect reflection features during the frequent short bursts. NICER will open a new field of studying the interaction of bursts and the accretion environment, which will inform us of which bursts are optimally suited for neutron star mass-radius measurements.

  11. Compton backscattered and primary X-rays from solar flares: angle dependent Green's function correction for photospheric albedo

    CERN Document Server

    Kontar, E P; Schwartz, R A; Brown, J C; Kontar, Eduard P.; Kinnon, Alec L. Mac; Schwartz, Richard A.; Brown, John C.

    2006-01-01

    The observed hard X-ray (HXR) flux spectrum $I(\\epsilon)$ from solar flares is a combination of primary bremsstrahlung photons $I_P(\\epsilon)$ with a spectrally modified component from photospheric Compton backscatter of downward primary emission. The latter can be significant, distorting or hiding the true features of the primary spectrum which are key diagnostics for acceleration and propagation of high energy electrons and of their energy budget. For the first time in solar physics, we use a Green's function approach to the backscatter spectral deconvolution problem, constructing a Green's matrix including photoelectric absorption. This approach allows spectrum-independent extraction of the primary spectrum for several HXR flares observed by the {\\it Ramaty High Energy Solar Spectroscopic Imager} (RHESSI). We show that the observed and primary spectra differ very substantially for flares with hard spectra close to the disk centre. We show in particular that the energy dependent photon spectral index $\\gamm...

  12. A Luminous X-Ray Flare from the Nucleus of the Dormant Bulgeless Spiral Galaxy NGC 247

    Science.gov (United States)

    Feng, Hua; Ho, Luis C.; Kaaret, Philip; Tao, Lian; Yamaoka, Kazutaka; Zhang, Shuo; Grisé, Fabien

    2015-07-01

    NGC 247 is a nearby late-type bulgeless spiral galaxy that contains an inactive nucleus. We report a serendipitous discovery of an X-ray flare from the galaxy center with a luminosity of up to 2× {10}39 erg s-1 in the 0.3-10 keV band with XMM-Newton. A Chandra observation confirms that the new X-ray source is spatially coincident with the galaxy nucleus. The XMM-Newton data revealed a hard power-law spectrum with a spectral break near 3-4 keV, no pulsations on timescales longer than 150 ms, and a flat power spectrum consistent with Poisson noise from 1 mHz to nearly 10 Hz. Follow-up observations with Swift detected a second flux peak followed by a luminosity drop by a factor of almost 20. The spectral and temporal behaviors of the nuclear source are consistent with the scenario that the flare was due to an outburst of a low-mass X-ray binary that contains a stellar-mass black hole emitting near its Eddington limit at the peak. However, it cannot be ruled out that the sudden brightening in the nucleus was due to accretion onto a possible low-mass nuclear black hole, fed by a tidally disrupted star or a gas cloud; the Monitor of All-sky X-ray Image observations limit the peak luminosity of the flare to less than ˜ {10}43 erg s-1, suggesting that it is either a low-mass black hole or an inefficient tidal disruption event.

  13. The EVE plus RHESSI DEM for Solar Flares, and Implications for Residual Non-Thermal X-Ray Emission

    Science.gov (United States)

    McTiernan, James; Caspi, Amir; Warren, Harry

    2016-05-01

    Solar flare spectra are typically dominated by thermal emission in the soft X-ray energy range. The low energy extent of non-thermal emission can only be loosely quantified using currently available X-ray data. To address this issue, we combine observations from the EUV Variability Experiment (EVE) on-board the Solar Dynamics Observatory (SDO) with X-ray data from the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI) to calculate the Differential Emission Measure (DEM) for solar flares. This improvement over the isothermal approximation helps to resolve the ambiguity in the range where the thermal and non-thermal components may have similar photon fluxes. This "crossover" range can extend up to 30 keV.Previous work (Caspi et.al. 2014ApJ...788L..31C) concentrated on obtaining DEM models that fit both instruments' observations well. For this current project we are interested in breaks and cutoffs in the "residual" non-thermal spectrum; i.e., the RHESSI spectrum that is left over after the DEM has accounted for the bulk of the soft X-ray emission. As in our earlier work, thermal emission is modeled using a DEM that is parametrized as multiple gaussians in temperature. Non-thermal emission is modeled as a photon spectrum obtained using a thin-target emission model ('thin2' from the SolarSoft Xray IDL package). Spectra for both instruments are fit simultaneously in a self-consistent manner.For this study, we have examined the DEM and non-thermal resuidual emission for a sample of relatively large (GOES M class and above) solar flares observed from 2011 to 2014. The results for the DEM and non-thermal parameters found using the combined EVE-RHESSI data are compared with those found using only RHESSI data.

  14. The collisional relaxation of electrons in hot flaring plasma and inferring the properties of solar flare accelerated electrons from X-ray observations

    CERN Document Server

    Jeffrey, Natasha; Emslie, Gordon; Bian, Nicolas

    2015-01-01

    X-ray observations are a direct diagnostic of fast electrons produced in solar flares, energized during the energy release process and directed towards the Sun. Since the properties of accelerated electrons can be substantially changed during their transport and interaction with the background plasma, a model must ultimately be applied to X-ray observations in order to understand the mechanism responsible for their acceleration. A cold thick target model is ubiquitously used for this task, since it provides a simple analytic relationship between the accelerated electron spectrum and the emitting electron spectrum in the X-ray source, with the latter quantity readily obtained from X-ray observations. However, such a model is inappropriate for the majority of solar flares in which the electrons propagate in a hot megaKelvin plasma, because it does not take into account the physics of thermalization of fast electrons. The use of a more realistic model, properly accounting for the properties of the background pla...

  15. A Statistical Study of GRB X-ray Flares: Evidence of Ubiquitous Bulk Acceleration in the Emission Region

    CERN Document Server

    Jia, Lan-Wei; Zhang, Bing

    2015-01-01

    When emission in a conical relativistic jet ceases abruptly, the observed decay light curve is controlled by the high-latitude "curvature effect". If the zero time is defined properly, the decay slope and the spectral index has a simple relation \\alpha=2+\\beta if the relativistic jet moves with a constant Lorentz factor. Uhm & Zhang recently found that the decay is steeper than this standard value if the jet is undergoing bulk acceleration when the emission ceases. By applying this theory to the flare data of GRBs, they found that the decay properties of flares demand that the emission region is undergoing significant bulk acceleration. This suggests that the jet is PFD, and that emission is powered by significant dissipation of Poynting-flux energy within the jet. Uhm & Zhang presented three X-ray flares as the examples. In this paper, we systematically analyze the flare data released by Swift to investigate whether bulk acceleration is common among flares. We select a sample of 85 bright flares dete...

  16. Tomographic analysis of the nonthermal x-ray bursts during disruption instability in the T-10 tokamak

    International Nuclear Information System (INIS)

    Non-thermal x-ray radiation (Eγ up to 150 keV) is measured in the T-10 tokamaks during disruption instability using two sets of CdTe detectors (10 vertical and 7 horizontal view detectors). Special narrow cupper tubes collimators with lead screening and CdTe detectors integrated with amplifiers inside metallic containers provides enhanced spatial resolution of the system (r ∼ 3 cm) and assures protection from the parasitic hard x-ray (Eγ up to 1.5 MeV) and electromagnetic loads during disruption. Spatial localization of the nonthermal x-ray emissivity is reconstructed using tomographic Cormack technique with SVD matrix inversion. Analysis indicated appearance of an intensive non-thermal x-ray bursts during initial stage of the disruptions at high density. The bursts are characterized by repetitive spikes (2–3 kHz) of the x-ray emissivity from the plasma core area. Analysis indicated that the spikes can be connected with acceleration of the non-thermal electrons in enhanced longitudinal electric fields induced during energy quench at the disruption instability

  17. Helium in natal HII regions: the origin of the X-ray absorption in gamma-ray burst afterglows

    CERN Document Server

    Watson, Darach; Andersen, Anja C; Fynbo, Johan P U; Gorosabel, Javier; Hjorth, Jens; Jakobsson, Páll; Krühler, Thomas; Laursen, Peter; Leloudas, Giorgos; Malesani, Daniele

    2012-01-01

    Soft X-ray absorption in excess of Galactic is observed in the afterglows of most gamma-ray bursts (GRBs), but the correct solution to its origin has not been arrived at after more than a decade of work, preventing its use as a powerful diagnostic tool. We resolve this long-standing problem and find that He in the GRB's host HII region is responsible for most of the absorption. We show that the X-ray absorbing column density (N_Hx) is correlated with both the neutral gas column density and with the optical afterglow extinction (Av). This correlation explains the connection between dark bursts and bursts with high N_Hx values. From these correlations we exclude an origin of the X-ray absorption which is not related to the host galaxy, i.e. the intergalactic medium or intervening absorbers are not responsible. We find that the correlation with the dust column has a strong redshift evolution, whereas the correlation with the neutral gas does not. From this we conclude that the column density of the X-ray absorpt...

  18. Central compact objects, superslow X-ray pulsars, gamma-ray bursts: do they have anything to do with magnetars?

    CERN Document Server

    Tong, H

    2014-01-01

    Magnetars and many of the magnetar-related objects are summarized together and discussed. It is shown that there is an abuse of language in the use of "magnetar". Anomalous X-ray pulsars and soft gamma-ray repeaters are well-known magnetar candidates. The current so called anti-magnetar (for central compact objects), accreting magnetar (for superslow X-ray pulsars in high mass X-ray binaries), and millisecond magnetar (for the central engine of some gamma-ray bursts), they may not be real magnetars in present understandings. Their observational behaviors are not caused by the magnetic energy. Many of them are just neutron stars with strong surface dipole field. A neutron star plus strong dipole field is not a magnetar. The characteristic parameters of the neutron stars for the central engine of some gamma-ray bursts are atypical from the neutron stars in the Galaxy. Possible signature of magnetic activities in accreting systems are discussed, including repeated bursts and a hard X-ray tail. China's future har...

  19. An investigation of solar flares and associated solar radio bursts on ionospheric total electron content

    Science.gov (United States)

    Uwamahoro, Jean

    2016-07-01

    Solar transients events such as Coronal Mass Ejections (CMEs) and solar flares represent are the cause of various aspects of space weather and can impact the modern man made technological system. Such solar transients are often associated with solar radio bursts (SRBs), particularly of type II and III that , at ground level can be detected by the CALLISTO (Compact Astronomical Low-frequency Low-cost Instrument for Spectroscopy and Transportable Observatories) solar spectrometer. The present study aims at investigating solar flares and associated SRBs impact on the ionospheric total electron content (TEC). SRBs data used are dynamic spectra covering the 2014-2015 period and detected by the CALLISTO instrument that is installed at the university of Rwanda, Kigali. To investigate ionospheric impact, we use TEC data from IGS stations located at almost the same universal time zone, and correlate the observed TEC changes to the corresponding observed solar bursts events. Preliminary observations resulting from this study indicate a slight enhancement in TEC during the burst event days. The observed TEC enhancement on the burst day can be associated to increased UV and X-rays radiations and particle acceleration that are associated with SRBs events. This work is a contribution to more understanding of the geo-space impact of solar transients phenomena for modeling and prediction.

  20. An investigation of solar flares and associated solar radio bursts impact on ionospheric total electron content

    Science.gov (United States)

    Tuyizere, Sarathiel

    2016-07-01

    Solar transients events such as Coronal Mass Ejections (CMEs) and solar flares represent the cause of various aspects of space weather and can impact the modern man made technological system. Such solar transients are often associated with solar radio bursts (SRBs), particularly of type II and III that , at ground level can be detected by the CALLISTO (Compact Astronomical Low-frequency Low-cost Instrument for Spectroscopy and Transportable Observatories) solar spectrometer. The present study aims at investigating solar flares and associated SRBs impact on the ionospheric total electron content (TEC). SRBs data used are dynamic spectra covering the 2014-2015 period and detected by the CALLISTO instrument that is installed at the university of Rwanda, Kigali. To investigate ionospheric impact, we use TEC data from IGS stations located at almost the same universal time zone, and correlate the observed TEC changes to the corresponding observed solar bursts events. Preliminary observations resulting from this study indicate a slight enhancement in TEC during the burst event days. The observed TEC enhancement on the burst day can be associated to increased UV and X-rays radiations and particle acceleration that are associated with SRBs events. This work is a contribution to more understanding of the geo-space impact of solar transients phenomena for modeling and prediction.

  1. Analysis of intermittency in submillimeter radio and Hard X-Rays during the impulsive phase of a solar flare

    CERN Document Server

    de Castro, C Guillermo Giménez; Raulin, Jean-Pierre; Guimarães, Odilon M

    2016-01-01

    We present an analysis of intermittent processes occurred during the impulsive phase of the flare SOL2012-03-13, using hard X-rays and submillimeter radio data. Intermittency is a key characteristic in turbulent plasmas and have been a analyzed recently for Hard X-rays data only. Since in a typical flare the same accelerated electron population is believed to produce both Hard X-rays and gyrosynchrotron, we compare both time profiles searching for intermittency signatures. For that we define a cross-wavelet power spectrum, that is used to obtain the Local Intermittency Measure or LIM. When greater than 3, the square LIM coefficients indicate a local intermittent process. The LIM$^2$ coefficient distribution in time and scale helps to identify avalanche or cascade energy release processes. We find two different and well separated intermittent behaviors in the submillimeter data: for scales greater than 20 s, a broad distribution during the rising and maximum phases of the emission seems to favor a cascade proc...

  2. Comparing SSN Index to X-ray Flare and Coronal Mass Ejection Rates from Solar Cycles 22-24

    CERN Document Server

    Winter, Lisa M; Balasubramaniam, K S

    2016-01-01

    The newly revised sunspot number series allows for placing historical geoeffective storms in the context of several hundred years of solar activity. Using statistical analyses of the Geostationary Operational Environmental Satellites (GOES) X-ray observations from the past ~30 years and the Solar and Heliospheric Observatory (SOHO) Large Angle and Spectrometric Coronagraph (LASCO) Coronal Mass Ejection (CME) catalog (1996-present), we present sunspot-number-dependent flare and CME rates. In particular, we present X-ray flare rates as a function of sunspot number for the past three cycles. We also show that the 1-8 AA X-ray background flux is strongly correlated with sunspot number across solar cycles. Similarly, we show that the CME properties (e.g., proxies related to the CME linear speed and width) are also correlated with sunspot number for SC 23 and 24. These updated rates will enable future predictions for geoeffective events and place historical storms in the context of present solar activity.

  3. A Luminous X-ray Flare From The Nucleus of The Dormant Bulgeless Spiral Galaxy NGC 247

    CERN Document Server

    Feng, Hua; Kaaret, Philip; Tao, Lian; Yamaoka, Kazutaka; Zhang, Shuo; Grisé, Fabien

    2015-01-01

    NGC 247 is a nearby late-type bulgeless spiral galaxy that contains an inactive nucleus. We report a serendipitous discovery of an X-ray flare from the galaxy center with a luminosity up to 2*10^39 erg/s in the 0.3-10 keV band with XMM-Newton. A Chandra observation confirms that the new X-ray source is spatially coincident with the galaxy nucleus. The XMM-Newton data revealed a hard power-law spectrum with a spectral break near 3-4 keV, no pulsations on timescales longer than 150 ms, and a flat power spectrum consistent with Poisson noise from 1 mHz to nearly 10 Hz. Follow-up observations with Swift detected a second flux peak followed by a luminosity drop by factor of almost 20. The spectral and temporal behaviors of the nuclear source are well consistent with the scenario that the flare was due to an outburst of a low-mass X-ray binary that contains a stellar-mass black hole emitting near its Eddington limit at the peak. However, it cannot be ruled out that the sudden brightening in the nucleus was due to a...

  4. Homologous Flare-CME Events and Their Metric Type II Radio Burst Association

    Science.gov (United States)

    Yashiro, S.; Gopalswamy, N.; Makela, P.; Akiyama, S.; Uddin, W.; Srivastava, A. K.; Joshi, N. C.; Chandra, R.; Manoharan, P. K.; Mahalakshmi, K.; Dwivedi, V. C.; Jain, R.; Awasthi, A. K.; Nitta, N. V.; Aschwanden, M. J.; Choudhary, D. P.

    2014-01-01

    Active region NOAA 11158 produced many flares during its disk passage. At least two of these flares can be considered as homologous: the C6.6 flare at 06:51 UT and C9.4 flare at 12:41 UT on February 14, 2011. Both flares occurred at the same location (eastern edge of the active region) and have a similar decay of the GOES soft X-ray light curve. The associated coronal mass ejections (CMEs) were slow (334 and 337 km/s) and of similar apparent widths (43deg and 44deg), but they had different radio signatures. The second event was associated with a metric type II burst while the first one was not. The COR1 coronagraphs on board the STEREO spacecraft clearly show that the second CME propagated into the preceding CME that occurred 50 min before. These observations suggest that CME-CME interaction might be a key process in exciting the type II radio emission by slow CMEs.

  5. Gamma-ray bursts and X-ray melting of material to form chondrules and planets

    CERN Document Server

    Duggan, P; Carr, A J; Winston, E; Vaughan, G; Hanlon, L; McBreen, S; Metcalfe, L; Kvick, A; Terry, A E

    2003-01-01

    Chondrules are millimeter sized objects of spherical to irregular shape that constitute the major component of chondritic meteorites that originate in the region between Mars and Jupiter and which fall to Earth. They appear to have solidified rapidly from molten or partially molten drops. The heat source that melted the chondrules remains uncertain. The intense radiation from a gamma-ray burst (GRB) is capable of melting material at distances up to 300 light years. These conditions were created in the laboratory for the first time when millimeter sized pellets were placed in a vacuum chamber in the white synchrotron beam at the European Synchrotron Radiation Facility. The pellets were rapidly heated in the X-ray and gamma-ray furnace to above 1400C melted and cooled. This process heats from the inside unlike normal furnaces. The melted spherical samples were examined with a range of techniques and found to have microstructural properties similar to the chondrules that come from meteorites. This experiment dem...

  6. Microwave Type III Pair Bursts in Solar Flares

    Science.gov (United States)

    Tan, Baolin; Mészárosová, Hana; Karlický, Marian; Huang, Guangli; Tan, Chengming

    2016-03-01

    A solar microwave type III pair burst is composed of normal and reverse-sloped (RS) burst branches with oppositely fast frequency drifts. It is the most sensitive signature of the primary energy release and electron accelerations in flares. This work reports 11 microwave type III pair events in 9 flares observed by radio spectrometers in China and the Czech Republic at a frequency of 0.80-7.60 GHz during 1994-2014. These type III pairs occurred in flare impulsive and postflare phases with separate frequencies in the range of 1.08-3.42 GHz and a frequency gap of 10-1700 MHz. The frequency drift increases with the separate frequency (fx), the lifetime of each burst is anti-correlated to fx, while the frequency gap is independent of fx. In most events, the normal branches are drifting obviously faster than the RS branches. The type III pairs occurring in flare impulsive phase have lower separate frequencies, longer lifetimes, wider frequency gaps, and slower frequency drifts than that occurring in postflare phase. Also, the latter always has strong circular polarization. Further analysis indicates that near the flare energy release sites the plasma density is about {10}10{--}{10}11 cm-3 and the temperature is higher than 107 K. These results provide new constraints to the acceleration mechanism in solar flares.

  7. The 2006-2007 Active Phase of Anomalous X-Ray Pulsar 4U 0142+61: Radiative and Timing Changes, Bursts,and Burst Spectral Features

    Science.gov (United States)

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

    2011-01-01

    After at least 6 years of quiescence, Anomalous X-ray Pulsar (AXP) 4U 0142+61 entered an active phase in 2006 March that lasted several months and included six X-ray bursts as well as many changes in the persistent X-ray emission. The bursts, the first seen from this AXP in > 11 years of Rossi X-ray Timing Explorer monitoring, all occurred in the interval between 2006 April 6 and 2007 February 7. The burst durations ranged from 0.4 - 1.8 x 10(exp 3) s. The first five burst spectra are well modeled by blackbodies, with temperatures kT approx 2 - 9 keV. However, the sixth burst had a complicated spectrum that is well characterized by a blackbody plus two emission features whose amplitude varied throughout the burst. The most prominent feature was at 14.0 keV. Upon entry into the active phase the pulsar showed a significant change in pulse morphology and a likely timing glitch. The glitch had a total frequency jump of (1.9+/-0.4) x 10(exp -7) Hz, which recovered with a decay time of 17+/-2 days by more than the initial jump, implying a net spin-down of the pulsar. Within the framework of the magnetar model, the net spin-down of the star could be explained by regions of the superfluid that rotate. slower than the rest. The bursts, flux enhancements, and pulse morphology changes can be explained as arising from crustal deformations due to stresses imposed by the highly twisted internal magnetic field. However, unlike other AXP outbursts, we cannot account for a major twist being implanted in the magnetosphere.

  8. X-ray flares and mass outflows driven by magnetic interaction between a protostar and its surrounding disk

    CERN Document Server

    Hayashi, M R; Matsumoto, R

    1996-01-01

    We propose a model of hard X-ray flares in protostars observed by ASCA satellite. Assuming that the dipole magnetic field of the protostar threads the protostellar disk, we carried out 2.5-dimensional magnetohydrodynamic (MHD) simulations of the disk-star interaction. The closed magnetic loops connecting the central star and the disk are twisted by the rotation of the disk. As the twist accumulates, magnetic loops expand and finally approach to the open field configuration. A current sheet is formed inside the expanding loops. In the presence of resistivity, magnetic reconnection takes place in the current sheet. Outgoing magnetic island and post flare loops are formed as a result of the reconnection. The time scale of this `flare' is the order of the rotation period of the disk. The released magnetic energy partly goes into the thermal energy and heats up the flaring plasma up to 10^8 K. The length of the flaring loop is several times of the radius of the central star, consistent with observations. The speed...

  9. Sensing the Earth's low ionosphere during solar flares using VLF signals and GOES X-ray data

    CERN Document Server

    Kolarski, Aleksandra

    2014-01-01

    An analysis of D-region electron density height profile variations, induced by four isolated solar X-ray flares during period from September 2005 to December 2006, based on the amplitude and the phase delay perturbation of 22.1 kHz signal trace from Skelton (54.72 N, 2.88 W) to Belgrade (44.85 N, 20.38 E), coded GQD, was carried out. Solar flare data were taken from NOAA GOES12 satellite one-minute listings. For VLF data acquisition and recordings at the Institute of Physics, Belgrade, Serbia, the AbsPAL system was used. Starting from LWPCv21 code (Ferguson, 1998), the variations of the Earth-ionosphere waveguide characteristic parameters, sharpness and reflection height, were estimated during the flare conditions. It was found that solar flare events affected the VLF wave propagation in the Earth-ionosphere waveguide by changing the lower ionosphere electron density height profile, in a different way, for different solar flare events.

  10. Coronal O VI emission observed with UVCS/SOHO during solar flares: Comparison with soft X-ray observations

    Science.gov (United States)

    Mancuso, S.; Giordano, S.; Raymond, J. C.

    2016-06-01

    In this work, we derive the O VI 1032 Å luminosity profiles of 58 flares, during their impulsive phase, based on off-limb measurements by the Ultraviolet Coronagraph Spectrometer (UVCS) aboard the SOlar and Heliospheric Observatory (SOHO). The O VI luminosities from the transition region plasma (here defined as the region with temperatures 5.0 ≤ log T (K) ≤ 6.0) were inferred from the analysis of the resonantly scattered radiation of the O VI coronal ions. The temperature of maximum ionization for O VI is log Tmax (K) = 5.47. By comparison with simultaneous soft X-ray measurements, we investigate the likely source (chromospheric evaporation, footpoint emission, or heated prominence ejecta) for the transition region emission observed during the impulsive phase. In our study, we find evidence of the main characteristics predicted by the evaporation scenario. Specifically, most O VI flares precede the X-ray peaks typically by several minutes with a mean of 3.2 ± 0.1 min, and clear correlations are found between the soft X-ray and transition region luminosities following power laws with indices ~ 0.7 ± 0.3. Overall, the results are consistent with transition region emission originating from chromospheric evaporation; the thermal X-ray emission peaks after the emission from the evaporation flow as the loops fill with hot plasma. Finally, we were able to infer flow speeds in the range ~20-100 km s-1 for one-third of the events, 14 of which showed speeds between 60 and 80 km s-1. These values are compatible with those found through direct spectroscopic observations at transition region temperatures by the EUV Imaging Spectrometer (EIS) on board Hinode.

  11. Soft X-ray Transmission Spectroscopy of Warm/Hot Intergalactic Medium: Mock Observation of Gamma-Ray Burst X-ray Afterglow

    CERN Document Server

    Kawahara, H; Sasaki, S; Suto, Y; Kawai, N; Mitsuda, K; Ohashi, T; Yamasaki, N; Kawahara, Hajime; Yoshikawa, Kohji; Sasaki, Shin; Suto, Yasushi; Kawai, Nobuyuki; Mitsuda, Kazuhisa; Ohashi, Takaya; Yamasaki, Noriko

    2005-01-01

    We discuss the detectability of Warm/Hot Intergalactic medium (WHIM) via the absorption lines toward bright gamma-ray burst (GRB) afterglows with future X-ray satellite missions like XEUS. We create mock absorption spectra for bright GRB afterglows ($\\sim 40$ per year over the entire sky) using a light-cone output of a cosmological hydrodynamic simulation. We assume that WHIM is under collisional and photo-ionization equilibrium. If we adopt the constant metallicity of $Z=0.1Z_\\odot$, approximately one O{\\sc vii} absorption line system with $>3\\sigma$ will be detected on average along a random line-of-sight up to $z=0.3$ if XEUS starts observing within a couple of hours after the GRB alert. However the above number is very sensitive to the adopted, and currently unknown, metallicity of the WHIM. We also discuss a feasibility of a follow-up observation for the emission line counterpart with a small dedicated X-ray mission like DIOS (Diffuse Intergalactic Oxygen Surveyor) and reliability of the estimate of the ...

  12. Modeling the X-ray variability in MCG-6-30-15: the multiple flare model

    Czech Academy of Sciences Publication Activity Database

    Goosmann, René; Mouchet, M.; Czerny, B.; Karas, Vladimír; Dovčiak, Michal; Goncalves, A.

    Melville : American Institute of Physics, 2010 - (Zatloukal, M.), 441-442-442 ISBN 978-0-7354-0795-4. ISSN 0094-243X. - (AIP Conference Proceedings. 1248). [X-ray astronomy 2009. Bologna (IT), 07.09.2009-11.09.2009] Institutional research plan: CEZ:AV0Z10030501 Keywords : X-ray: variability * galaxies: Seyfert Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  13. Time-resolved hard X-Ray hardness variation of solar flares observed by Suzaku Wide-band All-sky monitor

    OpenAIRE

    遠藤, 輝; Endo, Akira; 守上, 浩市; Morigami, Kouichi; 田代, 信; Tashiro, Makoto; 寺田, 幸功; Terada, Yukikatsu; 山岡, 和貴; Yamaoka, Kazutaka; 園田 絵里; Sonoda, Eri; 簑島, 敬; Minoshima, Takashi; Krucker, Sam

    2010-01-01

    Results of solar flare observations in the hard X-ray band with the Suzaku Wide-band All-sky Monitor (WAM) are reported. On June 2009, 108 solar flares (GOES class X:16, M:29, C:46, B:17) have been detected with the WAM since the launch. One of the brightest flares WAM detected was the event occurring on 2006 December 13. It lasted for more than 700 seconds even in above 500 keV. This event was simultaneously observed by the solar missions Hinode and RHESSI in soft and hard X-ray region respe...

  14. Automated Solar Flare Statistics in Soft X-rays over 37 Years of GOES Observations - The Invariance of Self-Organized Criticality during Three Solar Cycles

    OpenAIRE

    Markus J. Aschwanden; Freeland, Samuel L.

    2012-01-01

    We analyzed the soft X-ray light curves from the {\\sl Geostationary Operational Environmental Satellites (GOES)} over the last 37 years (1975-2011) and measured with an automated flare detection algorithm over 300,000 solar flare events (amounting to $\\approx 5$ times higher sensitivity than the NOAA flare catalog). We find a powerlaw slope of $\\alpha_F=1.98\\pm0.11$ for the (background-subtracted) soft X-ray peak fluxes that is invariant through three solar cycles and agrees with the theoreti...

  15. Model of motion of the X-ray loop-top source at the beginning of cusp-type flares

    Czech Academy of Sciences Publication Activity Database

    Karlický, Marian; Veronig, A.; Vršnak, B.

    2006-01-01

    Roč. 30, č. 1 (2006), s. 85-95. ISSN 1845-8319. [ Central European Solar Physics Meeting /2./. Bairisch Kölldorf, 19.05.2005-21.05.2005] R&D Projects: GA AV ČR IAA3003203; GA AV ČR 1QS300120506; GA ČR GA205/04/0358 Institutional research plan: CEZ:AV0Z10030501 Keywords : solar flares * heating processes * X-ray emission Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  16. DETERMINING NEUTRON STAR MASSES AND RADII USING ENERGY-RESOLVED WAVEFORMS OF X-RAY BURST OSCILLATIONS

    International Nuclear Information System (INIS)

    Simultaneous, precise measurements of the mass M and radius R of neutron stars can yield uniquely valuable information about the still uncertain properties of cold matter at several times the density of nuclear matter. One method that could be used to measure M and R is to analyze the energy-dependent waveforms of the X-ray flux oscillations seen during some thermonuclear bursts from some neutron stars. These oscillations are thought to be produced by X-ray emission from hotter regions on the surface of the star that are rotating at or near the spin frequency of the star. Here we explore how well M and R could be determined by generating and analyzing, using Bayesian techniques, synthetic energy-resolved X-ray data that we produce assuming a future space mission having 2-30 keV energy coverage and an effective area of 10 m2, such as the proposed Large Observatory for X-Ray Timing or Advanced X-Ray Timing Array missions. We find that waveforms from hot spots within 10° of the rotation equator usually constrain both M and R with an uncertainty of about 10%, if there are 106 total counts from the spot, whereas waveforms from spots within 20° of the rotation pole provide no useful constraints. The constraints we report can usually be achieved even if the burst oscillations vary with time and data from multiple bursts must be used to obtain 106 counts from the hot spot. This is therefore a promising method to constrain M and R tightly enough to discriminate strongly between competing models of cold, high-density matter

  17. Evidence for the Connection between Prompt and X-ray Afterglow emission of Swift-Detected Gamma-Ray Bursts

    CERN Document Server

    Grupe, Dirk; Verres, Peter; Zhang, Binbin; Gehrels, Neil

    2013-01-01

    When a massive star explodes as a Gamma Ray Burst information about this explosion is retained in the properties of the prompt and afterglow emission. We report on tight relationships between the prompt and X-ray afterglow emission of Swift-detected Gamma Ray Bursts found from BAT and XRT data between 2004 December and 2013 March. These relations suggest that the prompt and afterglow emission are closely linked. In particular, we find very strong correlations between the BAT 15-150keV T90 and the break times before and after the plateau phase in the X-ray 0.3-10keV afterglow light curves. We also find a strong anti-correlation between the photon index of the GRB prompt emission and the X-ray spectral slope of the afterglow. Further, anti-correlations exist between the rest frame peak energy in the prompt emission, E_ peak, and the X-ray afterglow decay slope during the plateau phase and the break times after the plateau phase. The rest-frame break times before and after the plateau phase are also anti-correla...

  18. NuSTAR detection of high-energy X-ray emission and rapid variability from Sagittarius A{sup *} flares

    Energy Technology Data Exchange (ETDEWEB)

    Barrière, Nicolas M.; Tomsick, John A.; Boggs, Steven E.; Craig, William W.; Zoglauer, Andreas [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Baganoff, Frederick K. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139-4307 (United States); Christensen, Finn E. [DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Kgs. Lyngby (Denmark); Dexter, Jason [Departments of Physics and Astronomy, University of California, Berkeley, CA 94720 (United States); Grefenstette, Brian; Harrison, Fiona A.; Madsen, Kristin K. [Cahill Center for Astronomy and Astrophysics, Caltech, Pasadena, CA 91125 (United States); Hailey, Charles J.; Mori, Kaya; Zhang, Shuo [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Zhang, William W. [X-ray Astrophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2014-05-01

    Sagittarius A{sup *} harbors the supermassive black hole that lies at the dynamical center of our Galaxy. Sagittarius A{sup *} spends most of its time in a low luminosity emission state but flares frequently in the infrared and X-ray, increasing up to a few hundred fold in brightness for up to a few hours at a time. The physical processes giving rise to the X-ray flares are uncertain. Here we report the detection with the NuSTAR observatory in Summer and Fall 2012 of four low to medium amplitude X-ray flares to energies up to 79 keV. For the first time, we clearly see that the power-law spectrum of Sagittarius A{sup *} X-ray flares extends to high energy, with no evidence for a cutoff. Although the photon index of the absorbed power-law fits are in agreement with past observations, we find a difference between the photon index of two of the flares (significant at the 95% confidence level). The spectra of the two brightest flares (∼55 times quiescence in the 2-10 keV band) are compared to simple physical models in an attempt to identify the main X-ray emission mechanism, but the data do not allow us to significantly discriminate between them. However, we confirm the previous finding that the parameters obtained with synchrotron models are, for the X-ray emission, physically more reasonable than those obtained with inverse Compton models. One flare exhibits large and rapid (<100 s) variability, which, considering the total energy radiated, constrains the location of the flaring region to be within ∼10 Schwarzschild radii of the black hole.

  19. Soft X-ray absorption excess in gamma-ray burst afterglow spectra: Absorption by turbulent ISM

    CERN Document Server

    Tanga, M; Gatto, A; Greiner, J; Krause, M G H; Diehl, R; Savaglio, S; Walch, S

    2016-01-01

    Two-thirds of long duration gamma-ray bursts (GRBs) show soft X-ray absorption in excess of the Milky Way. The column densities of metals inferred from UV and optical spectra differ from those derived from soft X-ray spectra, at times by an order of magnitude, with the latter being higher. The origin of the soft X-ray absorption excess observed in GRB X-ray afterglow spectra remains a heavily debated issue, which has resulted in numerous investigations on the effect of hot material both internal and external to the GRB host galaxy on our X-ray afterglow observations. Nevertheless, all models proposed so far have either only been able to account for a subset of our observations (i.e. at z > 2), or they have required fairly extreme conditions to be present within the absorbing material. In this paper, we investigate the absorption of the GRB afterglow by a collisionally ionised and turbulent interstellar medium (ISM). We find that a dense (3 per cubic centimeters) collisionally ionised ISM could produce UV/opti...

  20. INTEGRAL detects an X-ray burst from SAX J1747.0-2853 with no detectable persistent emission

    DEFF Research Database (Denmark)

    Chenevez, Jérôme; Brandt, Søren Kristian; Kuulkers, Erik;

    2009-01-01

    A new season of observations for the INTEGRAL Galactic Bulge monitoring (see ATel #438) has started on 2009 Feb. 21st. During the latest observation between 2009 Feb 25 13:21 and 17:02 (UT) a type I X-ray burst from SAX J1747.0-2853 (1A 1743-288, aka GX .2-0.2) was detected by JEM-X at UT 14:50:5...

  1. Classification of X-ray solar flares regarding their effects on the lower ionosphere electron density profile

    Directory of Open Access Journals (Sweden)

    D. P. Grubor

    2008-06-01

    Full Text Available The classification of X-ray solar flares is performed regarding their effects on the Very Low Frequency (VLF wave propagation along the Earth-ionosphere waveguide. The changes in propagation are detected from an observed VLF signal phase and amplitude perturbations, taking place during X-ray solar flares. All flare effects chosen for the analysis are recorded by the Absolute Phase and Amplitude Logger (AbsPal, during the summer months of 2004–2007, on the single trace, Skelton (54.72 N, 2.88 W to Belgrade (44.85 N, 20.38 E with a distance along the Great Circle Path (GCP D≈2000 km in length.

    The observed VLF amplitude and phase perturbations are simulated by the computer program Long-Wavelength Propagation Capability (LWPC, using Wait's model of the lower ionosphere, as determined by two parameters: the sharpness (β in 1/km and reflection height (H' in km. By varying the values of β and H' so as to match the observed amplitude and phase perturbations, the variation of the D-region electron density height profile Ne(z was reconstructed, throughout flare duration. The procedure is illustrated as applied to a series of flares, from class C to M5 (5×10−5 W/m2 at 0.1–0.8 nm, each giving rise to a different time development of signal perturbation.

    The corresponding change in electron density from the unperturbed value at the unperturbed reflection height, i.e. Ne(74 km=2.16×108 m−3 to the value induced by an M5 class flare, up to Ne(74 km=4×1010 m−3 is obtained. The β parameter is found to range from 0.30–0.49 1/km and the reflection height H' to vary from 74–63 km. The changes in Ne(z during the flares, within height range z=60 to 90 km are determined, as well.

  2. Propagation of Thermonuclear Flames on Rapidly Rotating Neutron Stars: Extreme Weather during Type I X-Ray Bursts

    Science.gov (United States)

    Spitkovsky, Anatoly; Levin, Yuri; Ushomirsky, Greg

    2002-02-01

    We analyze the global hydrodynamic flow in the ocean of an accreting, rapidly rotating, nonmagnetic neutron star in a low-mass X-ray binary during a type I X-ray burst. We use both analytical arguments and numerical simulations of simplified models for ocean burning. Our analysis extends previous work by taking into account the rapid rotation of the star and the lift-up of the burning ocean during the burst. We find a new regime for the spreading of a nuclear burning front, where the flame is carried along a coherent shear flow across the front. If turbulent viscosity is weak, the speed of flame propagation is vflame~(gh)1/2/ftn~20 km s-1, where h is the scale height of the burning ocean, g is the local gravitational acceleration, tn is the timescale for fast nuclear burning during the burst, and f is the Coriolis parameter, i.e., twice the local vertical component of the spin vector. If turbulent viscosity is dynamically important, the flame speed increases and reaches the maximum value, vmaxflame~(gh/ftn)1/2~300 km s-1, when the eddy overturn frequency is comparable to the Coriolis parameter f. We show that, as a result of rotationally reduced gravity, the thermonuclear runaway which ignites the ocean is likely to begin on the equator. The equatorial belt is ignited at the beginning of the burst, and the flame then propagates from the equator to the poles. Inhomogeneous cooling (equator first, poles second) of the hot ashes drives strong zonal currents which may be unstable to the formation of Jupiter-type vortices; we conjecture that these vortices are responsible for coherent modulation of X-ray flux in the tails of some bursts. We consider the effect of strong zonal currents on the frequency of modulation of the X-ray flux and show that the large values of the frequency drifts observed in some bursts can be accounted for within our model combined with the model of homogeneous radial expansion. Additionally, if vortices or other inhomogeneities are trapped in

  3. INTEGRAL/JEM-X detection of a type-I X-ray burst from MAXI J1421-613

    DEFF Research Database (Denmark)

    Bozzo, E.; Bazzano, A.; Kuulkers, Erik;

    2014-01-01

    onset of the burst occurred on 2014 January 10 at 19:05 UTC, and the total event as observed by JEM-X lasted for about 20 s (3-25 keV). The average spectrum of the burst could be roughly described by using a black-body model with temperature kT~1 keV. The corresponding flux was 1.7E-9 erg/cm^2/s...... (translating into a luminosity of 1.3E37 erg/s at 8 kpc; 3-10 keV). We estimated a persistent flux outside the burst of 7E-10 erg/cm^2/s (3-25 keV). This detection reveals that MAXI J1421-613 is a newly discovered X-ray bursting transient source, thus hosting an accreting neutron star....

  4. Quasi -Periodic Pulsations in Solar Flares: new clues from the Fermi Gamma-Ray Burst Monitor

    CERN Document Server

    Gruber, D; Bissaldi, E; Briggs, M S; Connaughton, V; Greiner, J; van der Horst, A J; Kanbach, G; Rau, A; Bhat, P N; Diehl, R; von Kienlin, A; Kippen, R M; Meegan, C A; Paciesas, W S; Preece, R D; Wilson-Hodge, C

    2011-01-01

    In the last four decades it has been observed that solar flares show quasi-periodic pulsations (QPPs) from the lowest, i.e. radio, to the highest, i.e. gamma-ray, part of the electromagnetic spectrum. To this day, it is still unclear which mechanism creates such QPPs. In this paper, we analyze four bright solar flares which show compelling signatures of quasi-periodic behavior and were observed with the Gamma-Ray Burst Monitor (\\gbm) onboard the Fermi satellite. Because GBM covers over 3 decades in energy (8 keV to 40 MeV) it can be a key instrument to understand the physical processes which drive solar flares. We tested for periodicity in the time series of the solar flares observed by GBM by applying a classical periodogram analysis. However, contrary to previous authors, we did not detrend the raw light curve before creating the power spectral density spectrum (PSD). To assess the significance of the frequencies we made use of a method which is commonly applied for X-ray binaries and Seyfert galaxies. This...

  5. Magnetic Non-Potentiality of Solar Active Regions and Peak X-Ray Flux of the Associated Flares

    CERN Document Server

    Tiwari, Sanjiv Kumar; Gosain, Sanjay

    2010-01-01

    Predicting the severity of the solar eruptive phenomena like flares and Coronal Mass Ejections (CMEs) remains a great challenge despite concerted efforts for several decades. The advent of high quality vector magnetograms obtained from Hinode (SOT/SP) has increased the possibility of meeting this challenge. In particular, the Spatially Averaged Signed Shear Angle (SASSA) seems to be an unique parameter to quantify the non-potentiality of the active regions. We demonstrate the usefulness of SASSA for predicting the flare severity. For this purpose we present case studies of the evolution of magnetic non-potentiality using 115 vector magnetograms of four active regions namely ARs NOAA 10930, 10960, 10961 and 10963 during December 08-15, 2006, June 03-10, 2007, June 28-July 5, 2007 and July 10-17, 2007 respectively. The NOAA ARs 10930 and 10960 were very active and produced X and M class flares respectively, along with many smaller X-ray flares. On the other hand, the NOAA ARs 10961 and 10963 were relatively les...

  6. 3D Radio and X-Ray Modeling and Data Analysis Software: Revealing Flare Complexity

    CERN Document Server

    Nita, Gelu M; Kuznetsov, Alexey A; Kontar, Eduard P; Gary, Dale E

    2014-01-01

    We have undertaken a major enhancement of our IDL-based simulation tools developed earlier for modeling microwave and X-ray emission. The object-based architecture provides an interactive graphical user interface that allows the user to import photospheric magnetic field maps and perform magnetic field extrapolations to almost instantly generate 3D magnetic field models, to investigate the magnetic topology of these models by interactively creating magnetic field lines and associated magnetic flux tubes, to populate the flux tubes with user-defined nonuniform thermal plasma and anisotropic, nonuniform, nonthermal electron distributions; to investigate the spatial and spectral properties of radio and X-ray emission calculated from the model, and to compare the model-derived images and spectra with observational data. The application integrates shared-object libraries containing fast gyrosynchrotron emission codes developed in FORTRAN and C++, soft and hard X-ray codes developed in IDL, a FORTRAN-based potentia...

  7. A survey of stellar X-ray flares from the XMM-Newton serendipitous source catalogue: Hipparcos-Tycho cool stars

    CERN Document Server

    Pye, J P; Fyfe, D; Schroeder, A C

    2015-01-01

    The X-ray emission from flares on cool (i.e. spectral-type F-M) stars is indicative of very energetic, transient phenomena, associated with energy release via magnetic reconnection. We present a uniform, large-scale survey of X-ray flare emission. The XMM-Newton Serendipitous Source Catalogue and its associated data products provide an excellent basis for a comprehensive and sensitive survey of stellar flares - both from targeted active stars and from those observed serendipitously in the half-degree diameter field-of-view of each observation. The 2XMM Catalogue and the associated time-series (`light-curve') data products have been used as the basis for a survey of X-ray flares from cool stars in the Hipparcos Tycho-2 catalogue. In addition, we have generated and analysed spectrally-resolved (i.e. hardness-ratio), X-ray light-curves. Where available, we have compared XMM OM UV/optical data with the X-ray light-curves. Our sample contains ~130 flares with well-observed profiles; they originate from ~70 stars. ...

  8. Amended Results for Hard X-Ray Emission by Non-thermal Thick Target Recombination in Solar Flares

    Science.gov (United States)

    Reep, J. W.; Brown, J. C.

    2016-06-01

    Brown & Mallik and the corresponding corrigendum Brown et al. presented expressions for non-thermal recombination (NTR) in the collisionally thin- and thick-target regimes, claiming that the process could account for a substantial part of the hard X-ray continuum in solar flares usually attributed entirely to thermal and non-thermal bremsstrahlung (NTB). However, we have found the thick-target expression to become unphysical for low cut-offs in the injected electron energy spectrum. We trace this to an error in the derivation, derive a corrected version that is real-valued and continuous for all photon energies and cut-offs, and show that, for thick targets, Brown et al. overestimated NTR emission at small photon energies. The regime of small cut-offs and large spectral indices involve large (reducing) correction factors but in some other thick-target parameter regimes NTR/NTB can still be of the order of unity. We comment on the importance of these results to flare and microflare modeling and spectral fitting. An empirical fit to our results shows that the peak NTR contribution comprises over half of the hard X-ray signal if δ ≳ 6{≤ft(\\tfrac{{E}0c}{4{keV}}\\right)}0.4.

  9. On the Power-Law Distributions of X-ray Fluxes from Solar Flares Observed with GOES

    CERN Document Server

    Li, You-ping; Zhang, Ping; Liu, Siming; Gan, Weiqun

    2016-01-01

    Power-law frequency distributions of the peak flux of solar flare X-ray emission have been studied extensively and attributed to a system of self-organized criticality (SOC). In this paper, we first show that, so long as the shape of the normalized light curve is not correlated with the peak flux, the flux histogram of solar flares also follows a power-law distribution with the same spectral index as the power-law frequency distribution of the peak flux, which may partially explain why power-law distributions are ubiquitous in the Universe. We then show that the spectral indexes of the histograms of soft X-ray fluxes observed by GOES satellites in two different energy channels are different: the higher energy channel has a harder distribution than the lower energy channel, which challenges the universal power-law distribution predicted by SOC models and implies a very soft distribution of thermal energy content of plasmas probed by the GOES. The temperature ($T$) distribution, on the other hand, approaches a ...

  10. Modeling the flaring activity of the high z, hard X-ray selected blazar IGR J22517+2217

    CERN Document Server

    Lanzuisi, G; Ghisellini, G; Ubertini, P; Panessa, F; Ajello, M; Bassani, L; Fukazawa, Y; D'Ammando, F

    2011-01-01

    We present new Suzaku and Fermi data, and re-analyzed archival hard X-ray data from INTEGRAL and Swift-BAT survey, to investigate the physical properties of the luminous, high-redshift, hard X-ray selected blazar IGR J22517+2217, through the modelization of its broad band spectral energy distribution (SED) in two different activity states. Through the analysis of the new Suzaku data and the flux selected data from archival hard X-ray observations, we build the source SED in two different states, one for the newly discovered flare occurred in 2005 and one for the following quiescent period. Both SEDs are strongly dominated by the high energy hump peaked at 10^20 -10^22 Hz, that is at least two orders of magnitude higher than the low energy (synchrotron) one at 10^11 -10^14 Hz, and varies by a factor of 10 between the two states. In both states the high energy hump is modeled as inverse Compton emission between relativistic electrons and seed photons produced externally to the jet, while the synchrotron self-Co...

  11. Results from DROXO IV. EXTraS discovery of an X-ray flare from the Class I protostar candidate ISO-Oph 85

    CERN Document Server

    Pizzocaro, Daniele; Paladini, Roberta; Tiengo, Andrea; Lisini, Gianni; Novara, Giovanni; Vianello, Giacomo; Belfiore, Andrea; Marelli, Martino; Salvetti, David; Pillitteri, Ignazio; Sciortino, Salvatore; D'Agostino, Daniele; Haberl, Frank; Watson, Mike; Wilms, Joern; Salvaterra, Ruben; De Luca, Andrea

    2015-01-01

    X-ray emission from Young Stellar Objects (YSOs) is crucial to understand star formation. A very limited amount of X-ray results is available for the protostellar (ClassI) phase. A systematic search of transient X-ray phenomena combined with a careful evaluation of the evolutionary stage offer a widely unexplored window to our understanding of YSOs X-ray properties. Within the EXTraS project, a search for transients and variability in the whole XMM-Newton archive, we discover transient X-ray emission consistent with ISO-Oph 85, a strongly embedded YSO in the rho Ophiuchi region, not detected in previous time-averaged X-ray studies. We extract an X-ray light curve for the flare and determine its spectral parameters from XMM-Newton/EPIC (European Photon Imaging Camera) data using quantile analysis. The X-ray flare ($2500\\,s$), the only one detected in the XMM-Newton archive for ISO-Oph 85, has a luminosity of $LogL_X[erg/s]=31.1$ and a spectrum consistent with a highly-absorbed one-component thermal model ($N_H...

  12. The Solar Flare 4: 10 keV X-ray Spectrum

    Science.gov (United States)

    Phillips, K. J. H.

    2004-01-01

    The 4-10 keV solar flare spectrum includes highly excited lines of stripped Ca, Fe, and Ni ions as well as a continuum steeply falling with energy. Groups of lines at approximately 7 keV and approximately 8 keV, observed during flares by the broad-band RHESSI spectrometer and called here the Fe-line and Fe/Ni-line features, are formed mostly of Fe lines but with Ni lines contributing to the approximately 8 keV feature. Possible temperature indicators of these line features are discussed - the peak or centroid energies of the Fe-line feature, the line ratio of the Fe-line to the Fe/Ni-line features, and the equivalent width of the Fe-line feature. The equivalent width is by far the most sensitive to temperature. However, results will be confused if, as is commonly believed, the abundance of Fe varies from flare to flare, even during the course of a single flare. With temperature determined from the thermal continuum, the Fe-line feature becomes a diagnostic of the Fe abundance in flare plasmas. These results are of interest for other hot plasmas in coronal ionization equilibrium such as stellar flare plasmas, hot gas in galaxies, and older supernova remnants.

  13. X-ray Flaring State in the HBL Source 1ES 1959+650

    Science.gov (United States)

    Kapanadze, Bidzina

    2015-09-01

    The nearby (z=0.048) TeV-detected HBL object 1ES 1959+650 has been observed three times with X-ray Telecope onboard Swift satellite (Swift-XRT) since 2015 August 25 on the basis of our ToO request of medium urgency (see https://www.swift.psu.edu/secure/toop/summary.php).

  14. NuSTAR detection of high-energy X-ray emission and rapid variability from Sagittarius A$^{\\star}$ flares

    CERN Document Server

    Barrière, Nicolas M; Baganoff, Frederick K; Boggs, Steven E; Christensen, Finn E; Craig, William W; Dexter, Jason; Grefenstette, Brian; Hailey, Charles J; Harrison, Fiona A; Madsen, Kristin K; Mori, Kaya; Stern, Daniel; Zhang, William W; Zhang, Shuo; Zoglauer, Andreas

    2014-01-01

    Sagittarius A$^{\\star}$ harbors the supermassive black hole that lies at the dynamical center of our Galaxy. Sagittarius A$^{\\star}$ spends most of its time in a low luminosity emission state but flares frequently in the infrared and X-ray, increasing up to a few hundred fold in brightness for up to a few hours at a time. The physical processes giving rise to the X-ray flares are uncertain. Here we report the detection with the NuSTAR observatory in Summer and Fall 2012 of four low to medium amplitude X-ray flares to energies up to 79 keV. For the first time, we clearly see that the power-law spectrum of Sagittarius A$^{\\star}$ X-ray flares extends to high energy, with no evidence for a cut off. Although the photon index of the absorbed power-law fits are in agreement with past observations, we find a difference between the photon index of two of the flares (significant at the 95% confidence level). The spectra of the two brightest flares (~55 times quiescence in the 2-10 keV band) are compared to simple phys...

  15. High resolution solar flare X-ray spectra: The temporal behavior of electron density, temperature, and emission measure for two class M flares

    International Nuclear Information System (INIS)

    High resolution soft X-ray flare spectra recorded by Naval Research Laboratory (NRL) and Aerospace Corporation Bragg crystal spectrometers flown on an orbiting spacecraft (P78-1) are combined and analyzed. THe instruments were launched on 1979 February 24 by the U.S. Air Force, and the data discussed in this paper cover the wavelength ranges, 1.82--1.97 A, 3.14--3.24 A, and 18.4--23.0 A. The NRL experiment (SOLFLEX) covers the two short wavelength ranges (highly ionized Fe and Ca lines) and the Aerospace experiment (SOLEX) covers the 18.4--23.0 A range, which includes the Lyα O VIII line and the resonance, intercombination, and forbidden lines of O VII. We analyze the spectra of two flares which occurred on 1980 April 8 and May 9. Temporal coverage is fairly complete for both flares, including the rise and decay phases. Measurements of electron density N/sub e/ with rather high time resolution (about 1 minute) have been obtained throughout most of the lifetime of the two flares. These measurements were obtained from the O VII lines and pertain to flare plasma at temperatures near 2 x 106 K. Peak density seems to occur slightly before the times of peak X-ray flux in the resonance lines of Fe XXV, Ca XIX, and O VII, and for both flares the peak density is about 1012 cm-3. Electron temperature T/sub e/ as a function of time is determined from the Fe and Ca spectra. Peak temperature for both flares is about 18 x 106 K. Differential emission measures and volume emission measures are determined from the resonance lines of O VII, Ca XIX, and Fe XXV. The number of electrons N/sub e/ΔV and the volume ΔV over which the O VII lines are formed are determined from the O VII volume emission measure N/sub e/2ΔV and the density N/sub e/. These quantities are determined as a function of time. The relationship of the low and high temperature regions is discussed

  16. Microwave Type III Pair Bursts in Solar Flares

    CERN Document Server

    Tan, Baolin; Karlicky, Marian; Huang, Guangli; Tan, Chengming

    2016-01-01

    Solar microwave type III pair burst is composed of normal and reverse-sloped (RS) burst branches with oppositely fast frequency drifts. It is the most sensitive signature of the primary energy release and electron accelerations in flares. This work reported 11 microwave type III pair events in 9 flares observed by radio spectrometers in China and the Czech Republic at frequency of 0.80 - 7.60 GHz during 1994 - 2014. These type III pairs occurred in flare impulsive and postflare phases with separate frequency in range of 1.08 - 3.42 GHz and frequency gap 10 - 1700 MHz. The frequency drift increases with the separate frequency (f_{x}), the lifetime of each burst is anti-correlated to f_{x}, while the frequency gap is independent to f_{x}. In most events, the normal branches are drifting obviously faster than the RS branches. The type III pairs occurring in flare impulsive phase have lower separate frequency, longer lifetime, wider frequency gap, and slower frequency drift than that occurring in postflare phase....

  17. Superorbital Periodic Modulation in Wind-Accretion High-Mass X-Ray Binaries from Swift Burst Alert Telescope Observations

    Science.gov (United States)

    Corbet, Robin H. D.; Krimm, Hans A.

    2013-01-01

    We report the discovery using data from the Swift-Burst Alert Telescope (BAT) of superorbital modulation in the wind-accretion supergiant high-mass X-ray binaries 4U 1909+07 (= X 1908+075), IGR J16418-4532, and IGR J16479-4514. Together with already known superorbital periodicities in 2S 0114+650 and IGR J16493-4348, the systems exhibit a monotonic relationship between superorbital and orbital periods. These systems include both supergiant fast X-ray transients and classical supergiant systems, and have a range of inclination angles. This suggests an underlying physical mechanism which is connected to the orbital period. In addition to these sources with clear detections of superorbital periods, IGR J16393-4643 (= AX J16390.4-4642) is identified as a system that may have superorbital modulation due to the coincidence of low-amplitude peaks in power spectra derived from BAT, Rossi X-Ray Timing Explorer Proportional Counter Array, and International Gamma-Ray Astrophysics Laboratory light curves. 1E 1145.1-6141 may also be worthy of further attention due to the amount of low-frequency modulation of its light curve. However, we find that the presence of superorbital modulation is not a universal feature of wind-accretion supergiant X-ray binaries.

  18. Results from DROXO. IV. EXTraS discovery of an X-ray flare from the Class I protostar candidate ISO-Oph 85

    Science.gov (United States)

    Pizzocaro, D.; Stelzer, B.; Paladini, R.; Tiengo, A.; Lisini, G.; Novara, G.; Vianello, G.; Belfiore, A.; Marelli, M.; Salvetti, D.; Pillitteri, I.; Sciortino, S.; D'Agostino, D.; Haberl, F.; Watson, M.; Wilms, J.; Salvaterra, R.; De Luca, A.

    2016-03-01

    X-ray emission from young stellar objects (YSOs) is a key ingredient in understanding star formation. For the early, protostellar (Class I) phase, a very limited (and controversial) quantity of X-ray results is available to date. Within the EXTraS (Exploring the X-ray Transient and variable Sky) project, we have discovered transient X-ray emission from a source whose counterpart is ISO-Oph 85, a strongly embedded YSO in the ρ Ophiuchi star-forming region. We extract an X-ray light curve for the flaring state, and determine the spectral parameters for the flare from XMM-Newton/EPIC data with a method based upon quantile analysis. We combine photometry from infrared to millimeter wavelengths from the literature with mid-IR Spitzer and unpublished submm Herschel photometry that we analysed for this work, and we describe the resulting spectral energy distribution (SED) with a set of precomputed models. The X-ray flare of ISO-Oph 85 lasted ~2500 s and is consistent with a highly-absorbed one-component thermal model (NH = 1.0-0.5+1.2 × 1023 cm-2 and kT= 1.15-0.65+2.35 keV). The X-ray luminosity during the flare is log LX [erg/s] = 31.1+2.0-1.2; during quiescence we set an upper limit of log LX [erg/s] < 29.5. We do not detect other flares from this source. The submillimeter fluxes suggest that the object is a Class I protostar. We caution, however, that the offset between the Herschel and optical/infrared position is larger than that for other YSOs in the region, leaving some doubt on this association. To the best of our knowledge, this is the first X-ray flare from a YSO that has been recognised as a candidate Class I protostar via the analysis of its complete SED, including the submm bands that are crucial for detecting the protostellar envelope. This work shows how the analysis of the whole SED is fundamental to the classification of YSOs, and how the X-ray source detection techniques we have developed can open a new era in time-resolved analysis of the X-ray

  19. X-ray flares from runaway pair production in active galactic nuclei

    Science.gov (United States)

    Kirk, J. G.; Mastichiadis, A.

    1992-01-01

    The hard X-ray spectrum of AGNs is nonthermal, probably arising from an electron-positron pair cascade, with some emission reflected off relatively cold matter. There has been interest in models on which protons are accelerated and create relativistic electrons on interaction with a local radiation field. It is shown here that a sufficient column density of protons can lead to runaway pair production: photons generated by the relativistic pairs are the targets for the protons to produce more pairs. This can produce X-ray fluxes with the characteristics observed in AGN. The model predicts the maximum ratio of luminosity to source size as well as their spectrum in the early phases. The same mechanism may also be able to create the knots of synchrotron-radiating pair plasma seen in sources such as 3C273.

  20. X-ray Flashes or soft Gamma-ray Bursts? The case of the likely distant XRF 040912

    CERN Document Server

    Stratta, G; Butler, N; Atteia, J L; Gendre, B; Pelangeon, A; Malacrino, F; Mellier, Y; Kann, D A; Klose, S; Zeh, A; Masetti, N; Palazzi, E; Gorosabel, J; Castro-Tirado, A J; De Postigo, A U; Jelinek, M; Cepa, J; Castaneda, H; Martínez-Delgado, D; Boër, M; Braga, J; Crew, G; Donaghy, T Q; Dezalay, J P; Doty, J; Fenimore, E E; Galassi, M; Graziani, C; Jernigan, J G; Kawai, N; Lamb, D Q; Levine, A; Manchanda, J; Martel, F; Matsuoka, M; Nakagawa, Y; Olive, J F; Pizzichini, G; Prigozhin, G Y; Ricker, G; Sakamoto, T; Shirasaki, Y; Sugita, S; Suzuki, M; Takagishi, K; Tamagawa, T; Vanderspek, R; Villasenor, J; Woosley, S E; Yamauchi, M; Yoshida, A

    2006-01-01

    In this work, we present a multi-wavelength study of XRF 040912, aimed at measuring its distance scale and the intrinsic burst properties. We performed a detailed spectral and temporal analysis of both the prompt and the afterglow emission and we estimated the distance scale of the likely host galaxy. We then used the currently available sample of XRFs with known distance to discuss the connection between XRFs and classical Gamma-ray Bursts (GRBs). We found that the prompt emission properties unambiguously identify this burst as an XRF, with an observed peak energy of E_p=17+/-13 keV and a burst fluence ratio S(2-30keV)/S(30-400keV)>1. A non-fading optical source with R~24 mag and with an apparently extended morphology is spatially consistent with the X-ray afterglow, likely the host galaxy. XRF 040912 is a very dark burst since no afterglow optical counterpart is detected down to R>25 mag (3 sigma limiting magnitude) at 13.6 hours after the burst. The host galaxy spectrum detected from 3800A to 10000A, shows...

  1. X-ray Flares Observed from Six Young Stars Located in the Region of Star Clusters NGC 869 and IC 2602

    Indian Academy of Sciences (India)

    Himali Bhatt; J. C. Pandey; K. P. Singh; Ram Sagar; Brijesh Kumar

    2014-03-01

    We present, for the first time, an analysis of seven intense X-ray flares observed from six stars (LAV 796, LAV 1174, SHM2002 3734, 2MASS 02191082+5707324, V553 Car, V557 Car). These stars are located in the region of young open star clusters NGC 869 and IC 2602. These flares detected in the XMM-Newton data show a rapid rise (10–40 min) and a slow decay (20–90 min). The X-ray luminosities during the flares in the energy band 0.3–7.5 keV are in the range of 1029.9 to 1031.7 erg s-1. The strongest flare was observed with the ratio ∼ 13 for count rates at peak of the flare to the quiescent intensity. The maximum temperature during the flares has been found to be ∼ 100 MK. The semi-loop lengths for the flaring loops are estimated to be of the order of 1010 cm. The physical parameters of the flaring structure, the peak density, pressure and minimum magnetic field required to confine the plasma have been derived and found to be consistent with flares from pre-main sequence stars in the Orion and the Taurus-Auriga-Perseus region.

  2. Radio flares from gamma-ray bursts

    CERN Document Server

    Kopac, D; Kobayashi, S; Virgili, F J; Harrison, R; Japelj, J; Guidorzi, C; Melandri, A; Gomboc, A

    2015-01-01

    We present predictions of centimeter and millimeter radio emission from reverse shocks in the early afterglows of gamma-ray bursts with the goal of determining their detectability with current and future radio facilities. Using a range of GRB properties, such as peak optical brightness and time, isotropic equivalent gamma-ray energy and redshift, we simulate radio light curves in a framework generalized for any circumburst medium structure and including a parametrization of the shell thickness regime that is more realistic than the simple assumption of thick- or thin-shell approximations. Building on earlier work by Mundell et al. (2007) and Melandri et al. (2010) in which the typical frequency of the reverse shock was suggested to lie at radio, rather than optical wavelengths at early times, we show that the brightest and most distinct reverse-shock radio signatures are detectable up to 0.1 -- 1 day after the burst, emphasizing the need for rapid radio follow-up. Detection is easier for bursts with later opt...

  3. Compton backscattered and primary X-rays from solar flares: angle dependent Green's function correction for photospheric albedo

    Science.gov (United States)

    Kontar, E. P.; MacKinnon, A. L.; Schwartz, R. A.; Brown, J. C.

    2006-02-01

    The observed hard X-ray (HXR) flux spectrum I(ɛ) from solar flares is a combination of primary bremsstrahlung photons I_P(ɛ) with a spectrally modified component from photospheric Compton backscatter of downward primary emission. The latter can be significant, distorting or hiding the true features of the primary spectrum which are key diagnostics for acceleration and propagation of high energy electrons and of their energy budget. For the first time in solar physics, we use a Green's function approach to the backscatter spectral deconvolution problem, constructing a Green's matrix including photoelectric absorption. This approach allows spectrum-independent extraction of the primary spectrum for several HXR flares observed by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). We show that the observed and primary spectra differ very substantially for flares with hard spectra close to the disk centre. We show in particular that the energy dependent photon spectral index γ (ɛ)=-d log I/d log ɛ is very different for I_P(ɛ) and for I(ɛ) and that inferred mean source electron spectra F(E) differ greatly. Even for a forward fitting of a parametric F(E) to the data, a clear low-energy cutoff required to fit I(ɛ) essentially disappears when the fit is to I_P(ɛ) - i.e. when albedo correction is included. The self-consistent correction for backscattered photons is thus shown to be crucial in determining the energy spectra of flare accelerated electrons, and hence their total number and energy.

  4. Flare-Associated X-Ray Plasma Ejections and Radio Drifting Structures

    Czech Academy of Sciences Publication Activity Database

    Kołomański, S.; Tomczak, M.; Ronowicz, P.; Karlický, Marian; Aurass, H.

    2007-01-01

    Roč. 31, č. 1 (2007), s. 125-128. ISSN 1845-8319. [Dynamical processes in the solar atmosphere. Hvar, 24.09.2006-29.09.2006] Institutional research plan: CEZ:AV0Z10030501 Keywords : Sun * corona * flares Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  5. Modeling of high frequency radio wave absorption on oblique soundings during a solar X-ray flare

    Science.gov (United States)

    Rogov, D. D.; Moskaleva, E. V.; Zaalov, N. Y.

    2015-01-01

    High frequency radio wave absorption induced by Solar Ultra-Violet (UV) and X-ray flux is investigated. The influence of the solar flare observed on 11 April 2013 on the structure of oblique sounding ionograms in the Arctic region of Russia is considered. An adjustable model of the ionosphere developed for high frequency (HF) propagation problems was employed for this purpose. The simulation algorithm has been designed to accept a large variety of ionospheric conditions. On the basis of the SWPC D-region Absorption model the absorption effects in the ionosphere at sub-auroral latitudes of the Earth were calculated. This approach does not require knowledge of the electron density and electron collision frequency profiles of the D-region ionosphere. The oblique ionograms simulated with the absorption effect and ionograms provided by Russian network of ionospheric observations deployed in Arctic region exhibit quite a good resemblance.

  6. Microwave and X-Ray emission during a isentropic expansion and its application to solar bursts

    International Nuclear Information System (INIS)

    The gyro-synchrotron emission in microwaves and the free-free emission in X-rays of a plasma enclosed in a cylinder coincident with a magnetic force tube were calculated for an isentropic self-similar expansion, with plane and cylindrical symmetries. This expansion model was applied to a region of the low solar corona, and the results were compared to the emission observed in some simple solar events of low intensity. The calculations show satisfactory coincidence with the events in X-rays for energies around 1029 ergs. The solar events analyzed in microwaves, which are not the same that were studied in X-rays, in general do not fit the theoretical results. The origin of the discrepancy is probably the formulation of the processes of emission applied to the expansion. (Author)

  7. The flare model for X-ray variability of NGC 4258

    Czech Academy of Sciences Publication Activity Database

    Trzesniewski, T.; Czerny, B.; Karas, Vladimír; Pecháček, Tomáš; Dovčiak, Michal; Goosmann, R. W.; Nikolajuk, M.

    2011-01-01

    Roč. 530, June (2011), A136/1-A136/6. ISSN 0004-6361 R&D Projects: GA ČR GA205/07/0052; GA MŠk ME09036; GA ČR GA202/09/0772; GA ČR GP205/09/P468 Institutional research plan: CEZ:AV0Z10030501 Keywords : accretion disks * active galaxies * X-rays Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.587, year: 2011

  8. The full curvature effect expected in early X-ray afterglow emission of gamma-ray bursts

    OpenAIRE

    Qin, Y. -P.

    2008-01-01

    We explore the influence of the full curvature effect on the flux of early X-ray afterglow of gamma-ray bursts (GRBs) in cases when the spectrum of the intrinsic emission is a power-law. We find that the well-known $t^{-(2+\\beta)}$ curve is present only when the intrinsic emission is extremely short or the emission arises from an exponential cooling. The time scale of this curve is independent of the Lorentz factor. The resulting light curve would contain two phases when the intrinsic emissio...

  9. Failed Gamma-Ray Bursts: Thermal UV/Soft X-ray Emission Accompanied by Peculiar Afterglows

    CERN Document Server

    Xu, M; Huang, Y -F; Lee, S -H

    2011-01-01

    We show that the photospheres of "failed" Gamma-Ray Bursts (GRBs), whose bulk Lorentz factors are much lower than 100, can be outside of internal shocks. The resulting radiation from the photospheres is thermal and bright in UV/Soft X-ray band. The photospheric emission lasts for about one thousand seconds with luminosity about several times 10^46 erg/s. These events can be observed by current and future satellites. It is also shown that the afterglows of failed GRBs are peculiar at the early stage, which makes it possible to distinguish failed GRBs from ordinary GRBs and beaming-induced orphan afterglows.

  10. Constraining Hot Plasma in a Non-flaring Solar Active Region with FOXSI Hard X-ray Observations

    CERN Document Server

    Ishikawa, Shin-nosuke; Christe, Steven; Ishibashi, Kazunori; Brooks, David H; Williams, David R; Shimojo, Masumi; Sako, Nobuharu; Krucker, Sam

    2015-01-01

    We present new constraints on the high-temperature emission measure of a non-flaring solar active region using observations from the recently flown Focusing Optics X-ray Solar Imager sounding rocket payload. FOXSI has performed the first focused hard X-ray (HXR) observation of the Sun in its first successful flight on 2012 November 2. Focusing optics, combined with small strip detectors, enable high-sensitivity observations with respect to previous indirect imagers. This capability, along with the sensitivity of the HXR regime to high-temperature emission, offers the potential to better characterize high-temperature plasma in the corona as predicted by nanoflare heating models. We present a joint analysis of the differential emission measure (DEM) of active region 11602 using coordinated observations by FOXSI, Hinode/XRT and Hinode/EIS. The Hinode-derived DEM predicts significant emission measure between 1 MK and 3 MK, with a peak in the DEM predicted at 2.0-2.5 MK. The combined XRT and EIS DEM also shows emi...

  11. Interpretation of the burst spectra from X-ray burster MXB 1728-34 with allowance for Thomson scattering

    International Nuclear Information System (INIS)

    Spectral evolution is investigated and interpretations of the spectra are considered for a burst from the X-ray burster MXB 1728-34 detected by ASTRON. Interpretation of the burst spectra in terms of black.body radiation leads to improbably small neutron star (NS) mass M and radius R as well as distance D to the burster. Interpretation of the spectra around the burst maximum (first ≅4 s) in terms of radiation from an isothermal NS photosphere with dominating role of the Thomson scattering allows one to obtain reasonable constraints on M, R, and D (in particular, M=(1.4-2) M Sun, R=(6.5-12) km for D=6 kpk and helium photosphere). This interpretation leads to a conclusion that the photosphere expands up to several tens of kilometers in the burst maximum. The luminosity remains close to the Eddington limit during expansion and contraction; maxima of the observed flux corresponding to minima of the luminosity due to general relativity effects. The burst tail spectra are close to those of thermal bremstrahlung. Such spectra might originate in a corona around NS with mass ∼ 10 -16 MSun, radius ∼ 100 km and electron density ∼ 1019 cm-3, or in a hot layer with thickness ∼ 1-10 gxcm-2 on the photosphere

  12. Constraints on the inner accretion flow of 4U/MXB 1636-53 (V 801 Arae) from a comparison of X-ray burst and persistent emission

    NARCIS (Netherlands)

    E. Damen; R.A.M.J. Wijers; J. van Paradijs; W. Penninx; T. Oosterbroek; W.H.G. Lewin; F. Jansen

    1990-01-01

    A detailed analysis is presented of the importance of Comptonization in burst and persistent spectra of the low-mass X-ray binary 4U/MXB 1636-53, and from this analysis it is inferred that the inner accretion flow is geometrically thin. It is found that burst spectra of 1636-53 are very nearly Planc

  13. Radio and X-ray observations of an exceptional radio flare in the extreme z=4.72 blazar GB B1428+4217

    CERN Document Server

    Worsley, M A; Pooley, G G; Chandler, C J

    2006-01-01

    We report on the extreme behaviour of the high redshift blazar GB B1428+4217 at z=4.72. A continued programme of radio measurements has revealed an exceptional flare in the lightcurve, with the 15.2 GHz flux density rising by a factor ~3 from ~140 mJy to ~430 mJy in a rest-frame timescale of only ~4 months -- much larger than any previous flares observed in this source. In addition to new measurements of the 1.4-43 GHz radio spectrum we also present the analysis and results of a target-of-opportunity X-ray observation using XMM-Newton, made close to the peak in radio flux. Although the X-ray data do not show a flare in the high energy lightcurve, we are able to confirm the X-ray spectral variability hinted at in previous observations. GB B1428+4217 is one of several high-redshift radio-loud quasars that display a low energy break in the X-ray spectrum, probably due to the presence of excess absorption in the source. X-ray spectral analysis of the latest XMM-Newton data is shown to be consistent with the warm ...

  14. Plasmoids in Solar Flares and Their Radio and X-ray Signatures

    Czech Academy of Sciences Publication Activity Database

    Karlický, Marian; Bárta, Miroslav

    Berlin : Springer, 2012 - (Leubner, M.; Vörös, Z.), s. 49-59 ISBN 9783642304415. ISSN 1570-6591. - (Astrophysics and Space Science Proceedings. 33). [International Astrophysics Forum 2011. Tyrolean Alpbach (AT), 20.06.2011-24.06.2011] R&D Projects: GA ČR GAP209/10/1680; GA ČR GAP209/12/0103 Institutional research plan: CEZ:AV0Z10030501 Keywords : solar flares Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  15. High-spatial resolution and high-spectral resolution detector for use in the measurement of solar flare hard x rays

    International Nuclear Information System (INIS)

    In the areas of high spatial resolution, the evaluation of a hard X-ray detector with 65 micron spatial resolution for operation in the energy range from 30 to 400 keV is proposed. The basic detector is a thick large-area scintillator faceplate, composed of a matrix of high-density scintillating glass fibers, attached to a proximity type image intensifier tube with a resistive-anode digital readout system. Such a detector, combined with a coded-aperture mask, would be ideal for use as a modest-sized hard X-ray imaging instrument up to X-ray energies as high as several hundred keV. As an integral part of this study it was also proposed that several techniques be critically evaluated for X-ray image coding which could be used with this detector. In the area of high spectral resolution, it is proposed to evaluate two different types of detectors for use as X-ray spectrometers for solar flares: planar silicon detectors and high-purity germanium detectors (HPGe). Instruments utilizing these high-spatial-resolution detectors for hard X-ray imaging measurements from 30 to 400 keV and high-spectral-resolution detectors for measurements over a similar energy range would be ideally suited for making crucial solar flare observations during the upcoming maximum in the solar cycle

  16. POSSIBLE DETECTION OF APPARENT SUPERLUMINAL INWARD MOTION IN MARKARIAN 421 AFTER THE GIANT X-RAY FLARE IN 2010 FEBRUARY

    Energy Technology Data Exchange (ETDEWEB)

    Niinuma, K. [Graduate School of Science and Engineering, Yamaguchi University, Yamaguchi 753-8511 (Japan); Kino, M.; Oyama, T. [Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588 (Japan); Nagai, H. [ALMA-J Project, National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588 (Japan); Isobe, N. [Institute of Space and Astronautics, Japan Aerospace Exploration Agency, Yoshinodai, Chuo, Sagamihara 252-5210 (Japan); Gabanyi, K. E. [Hungarian Academy of Sciences, Research Group for Physical Geodesy and Geodynamics, FOMI Satellite Geodetic Observatory Budapest, 1592 Budapest (Hungary); Hada, K. [INAF Istituto di Radioastronomia, via Gobetti 101, I-40129 Bologna (Italy); Koyama, S. [Department of Astronomy, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8654 (Japan); Asada, K. [Academia Sinica Institute of Astronomy and Astrophysics, Taipei 10617, Taiwan (China); Fujisawa, K., E-mail: niinuma@yamaguchi-u.ac.jp [Research Institute for Time Studies, Yamaguchi University, Yamaguchi 753-8511 (Japan)

    2012-11-10

    We report on the very long baseline interferometry (VLBI) follow-up observations using the Japanese VLBI Network array at 22 GHz for the largest X-ray flare of TeV blazar Mrk 421 that occurred in 2010 mid-February. The total of five epochs of observations were performed at intervals of about 20 days between 2010 March 7 and May 31. No newborn component associated with the flare was seen directly in the total intensity images obtained by our multi-epoch VLBI observations. However, one jet component located at {approx}1 mas northwest from the core was able to be identified, and its proper motion can be measured as -1.66 {+-} 0.46 mas yr{sup -1}, which corresponds to an apparent velocity of -3.48 {+-} 0.97c. Here, this negative velocity indicates that the jet component was apparently moving toward the core. As the most plausible explanation, we discuss that the apparent negative velocity was possibly caused by the ejection of a new component, which could not be resolved with our observations. In this case, the obtained Doppler factor of the new component is around 10-20, which is consistent with the ones typically estimated by model fittings of spectral energy distribution for this source.

  17. SMM observations of K-alpha radiation from fluorescence of photospheric iron by solar flare X-rays

    Science.gov (United States)

    Parmar, A. N.; Culhane, J. L.; Rapley, C. G.; Wolfson, C. J.; Acton, L. W.; Phillips, K. J. H.; Dennis, B. R.

    1984-01-01

    High-resolution Fe K-alpha spectra near 1.94 A observed during solar flares with the Bent Crystal Spectrometer on the Solar Maximum Mission are presented. The evidence for two possible excitation mechanisms, electron impact and fluorescence, is examined. It is found that the fluorescence mechanism satisfactorily describes the results, while the observations do not support electron collisional excitation of the Fe K-alpha transitions in low ionization stages (II-XII) of iron. Using Bai's model of the fluorescent excitation process, the photospheric iron abundance relative to that of hydrogen is estimated to be 5-6 x 10 to the -5th. The mean height of the soft X-ray source producing the K-alpha fluorescence is calculated on the basis of this model for about 40 large flares. The solar K-alpha lines are found to be about 25 percent wider than those measured in the laboratory. Weak line features observed at wavelengths shorter than that of the K-alpha lines are discussed.

  18. Amended results for hard X-ray emission by non-thermal thick target recombination in solar flares

    CERN Document Server

    Reep, Jeffrey W

    2016-01-01

    Brown & Mallik 2008 and the Brown et al. 2010 corrigendum of it presented expressions for non-thermal recombination (NTR) in the collisionally thin- and thick-target regimes, claiming that the process could account for a substantial part of hard X-ray continuum in solar flares usually attributed entirely to thermal and non-thermal bremsstrahlung (NTB). However, we have found the thick-target expression to become unphysical for low cut-offs in the injected electron energy spectrum. We trace this to an error in the derivation, derive a corrected version which is real-valued and continuous for all photon energies and cut-offs, and show that, for thick targets, Brown et al. over-estimated NTR emission at small photon energies. The regime of small cut-offs and large spectral indices involve large (reducing) correction factors but in some other thick-target parameter regimes NTR/NTB can still be of order unity. We comment on the importance of these results to flare and to microflare modeling and spectral fittin...

  19. AUTOMATED SOLAR FLARE STATISTICS IN SOFT X-RAYS OVER 37 YEARS OF GOES OBSERVATIONS: THE INVARIANCE OF SELF-ORGANIZED CRITICALITY DURING THREE SOLAR CYCLES

    International Nuclear Information System (INIS)

    We analyzed the soft X-ray light curves from the Geostationary Operational Environmental Satellites over the last 37 years (1975-2011) and measured with an automated flare detection algorithm over 300,000 solar flare events (amounting to ≈5 times higher sensitivity than the NOAA flare catalog). We find a power-law slope of αF = 1.98 ± 0.11 for the (background-subtracted) soft X-ray peak fluxes that is invariant through three solar cycles and agrees with the theoretical prediction αF = 2.0 of the fractal-diffusive self-organized criticality (FD-SOC) model. For the soft X-ray flare rise times, we find a power-law slope of αT = 2.02 ± 0.04 during solar cycle minima years, which is also consistent with the prediction αT = 2.0 of the FD-SOC model. During solar cycle maxima years, the power-law slope is steeper in the range of αT ≈ 2.0-5.0, which can be modeled by a solar-cycle-dependent flare pile-up bias effect. These results corroborate the FD-SOC model, which predicts a power-law slope of αE = 1.5 for flare energies and thus rules out significant nanoflare heating. While the FD-SOC model predicts the probability distribution functions of spatio-temporal scaling laws of nonlinear energy dissipation processes, additional physical models are needed to derive the scaling laws between the geometric SOC parameters and the observed emissivity in different wavelength regimes, as we derive here for soft X-ray emission. The FD-SOC model also yields statistical probabilities for solar flare forecasting.

  20. Light Echos in Kerr Geometry: A Source of High Frequency QPOs from Random X-ray Bursts

    Science.gov (United States)

    Fukumura, K.; Kazanas, D.

    2008-01-01

    We propose that high frequency quasi-periodic oscillations (HFQPOs) can be produced from randomly-formed X-ray bursts (flashes) by plasma interior to the ergosphere of a rapidly-rotating black hole. We show by direct computation of their orbits that the photons comprising the observed X-ray light curves, if due to a multitude of such flashes, are affected significantly by the black hole's dragging of inertial frames; the photons of each such burst arrive to an observer at infinity in multiple (double or triple), distinct 'bunches' separated by a roughly constant time lag of t/M approximately equal to 14, regardless of the bursts' azimuthal position. We argue that every other such 'bunch' represents photons that follow trajectories with an additional orbit around the black hole at the photon circular orbit radius (a photon 'echo'). The presence of this constant lag in the response function of the system leads to a QPO feature in its power density spectra, even though the corresponding light curve consists of a totally stochastic signal. This effect is by and large due to the black hole spin and is shown to gradually diminish as the spin parameter a decreases or the radial position of the burst moves outside the static limit surface (ergosphere). Our calculations indicate that for a black hole with Kerr parameter of a/M=0.99 and mass of M=10*Msun the QPO is expected at a frequency of approximately 1.3-1.4 kHz. We discuss the plausibility and observational implications of our model/results as well as its limitations.

  1. X-ray line ratios from helium-like ions - Updated theory and SMM flare observations

    Science.gov (United States)

    Wolfson, C. J.; Leibacher, J. W.; Doyle, J. G.; Phillips, K. J. H.

    1983-01-01

    The potential which the conduction of measurements of the three principal lines emitted from helium-like ions has for the determination of plasma electron density was initially pointed out by Gabriel and Jordan (1969). The diagnostic technique is based on the fact that the ratio, R, of the intensity of a forbidden line to the intensity of an intercombination line decreases as electron density increases due to collisional excitation of levels. In the present investigation a further refinement of this procedure is provided by specifically calculating the effects of cascades from levels with principal quantum numbers up to n=6. Two improved spectrometers recently placed in operation include the SOLEX instrument on the satellite P78-1 and the X-ray Polychromator (XRP) instrument on the NASA Solar Maximum Mission satellite. Measurements obtained with one of the spectrometers making up the XRP are presented, taking into account the emission from Ne IX ions.

  2. Observations of the Crab Nebula with the Chandra X-Ray Observatory During the Gamma-Ray Flare of 2011 April

    Science.gov (United States)

    Weisskopf, Martin C.

    2012-01-01

    Recently, using the AGILE and Fermi satellites, gamma-ray flares have been discovered from the direction of the Crab Nebula (Tavani et al. 2011, Abdo et al. 2011). We have been using the Chandra X-Ray observatory to monitor the Crab on a monthly cadence since just after the 2010 September gamma-ray flare. We were fortunate to trigger series of pre-planned target of opportunity observations during the 2011 April flare. We present the results of these observations and address some implications both for now and for the future.

  3. The Swift Burst Alert Telescope Detected Seyfert 1 Galaxies: X-Ray Broadband Properties and Warm Absorbers

    Science.gov (United States)

    Winter, Lisa M.; Veilleux, Sylvain; McKernan, Barry; Kallman, T.

    2012-01-01

    We present results from an analysis of the broadband, 0.3-195 keV, X-ray spectra of 48 Seyfert 1-1.5 sources detected in the very hard X-rays with the Swift Burst Alert Telescope (BAT). This sample is selected in an all-sky survey conducted in the 14-195 keV band. Therefore, our sources are largely unbiased toward both obscuration and host galaxy properties. Our detailed and uniform model fits to Suzaku/BAT and XMM-Newton/BAT spectra include the neutral absorption, direct power-law, reflected emission, soft excess, warm absorption, and narrow Fe I K[alpha] emission properties for the entire sample. We significantly detect O VII and O VIII edges in 52% of our sample. The strength of these detections is strongly correlated with the neutral column density measured in the spectrum. Among the strongest detections, X-ray grating and UV observations, where available, indicate outflowing material. The ionized column densities of sources with O VII and O VIII detections are clustered in a narrow range with Nwarm [approx] 1021 cm-2, while sources without strong detections have column densities of ionized gas an order of magnitude lower. Therefore, we note that sources without strong detections likely have warm ionized outflows present but at low column densities that are not easily probed with current X-ray observations. Sources with strong complex absorption have a strong soft excess, which may or may not be due to difficulties in modeling the complex spectra of these sources. Still, the detection of a flat [Gamma] [approx] 1 and a strong soft excess may allow us to infer the presence of strong absorption in low signal-to-noise active galactic nucleus spectra. Additionally, we include a useful correction from the Swift BAT luminosity to bolometric luminosity, based on a comparison of our spectral fitting results with published spectral energy distribution fits from 33 of our sources.

  4. Burst Tails from SGR J1550-5418 Observed with Rossi X-ray Timing Explorer

    CERN Document Server

    Mus, Sinem Sasmaz; Kaneko, Yuki; Chakraborty, Manoneeta; Aydin, Berk

    2015-01-01

    We present the results of our extensive search using the Bayesian block method for long tails following short bursts from a magnetar, SGR J1550-5418, over all RXTE observations of the source. We identified four bursts with extended tails, most of which occurred during its 2009 burst active episode. The durations of tails range between ~13 s and over 3 ks, which are much longer than the typical duration of bursts. We performed detailed spectral and temporal analysis of the burst tails. We find that the spectra of three tails show a thermal nature with a trend of cooling throughout the tail. We compare the results of our investigations with the properties of four other extended tails detected from SGR 1900+14 and SGR 1806-20 and suggest a scenario for the origin of the tail in the framework of the magnetar model.

  5. X-Ray and Hα Emission of the 20 Aug 2002 Flare

    Czech Academy of Sciences Publication Activity Database

    Kašparová, Jana; Karlický, Marian; Schwartz, R. A.; Dennis, B. R.

    Dordrecht: Springer, 2005 - (Hanslmeier, A.; Veronig, A.; Messerotti, M.), s. 187-190. (Astrophysics and space science library. 320). ISBN 1-4020-2961-6. [Summerschool and Workshop /3./. Kanzelhoehe (AT), 25.08.2003-05.09.2003] R&D Projects: GA AV ČR IAA3003202; GA AV ČR IAA3003203; GA ČR GA205/02/0980; GA AV ČR KSK2043105 Institutional research plan: CEZ:AV0Z10030501 Keywords : solar flares * RHESSI * Halpha Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  6. X-ray flares on the UV Ceti-type star CC Eridani: a "peculiar" time-evolution of spectral parameters

    CERN Document Server

    Crespo-Chacón, I; Reale, F; Caramazza, M; López-Santiago, J; Pillitteri, I

    2007-01-01

    Context: Weak flares are supposed to be an important heating agent of the outer layers of stellar atmospheres. However, due to instrumental limitations, only large X-ray flares have been studied in detail until now. Aims: We used an XMM-Newton observation of the very active BY-Dra type binary star CC Eri in order to investigate the properties of two flares that are weaker than those typically studied in the literature. Methods: We performed time-resolved spectroscopy of the data taken with the EPIC-PN CCD camera. A multi-temperature model was used to fit the spectra. We inferred the size of the flaring loops using the density-temperature diagram. The loop scaling laws were applied for deriving physical parameters of the flaring plasma. We also estimated the number of loops involved in the observed flares. Results: A large X-ray variability was found. Spectral analysis showed that all the regions in the light curve, including the flare segments, are well-described by a 3-T model with variable emission measures...

  7. Hard X-ray bursts and DD microfusion neutrons from complex plasmas of vacuum discharge

    Indian Academy of Sciences (India)

    Yu K Kurilenkov; M Skowronek

    2003-12-01

    We create the random complex media of high-power density in low-energy nanosecond vacuum discharges. Hard X-ray emission efficiency, generation of energetic ions (∼ 1 MeV) and neutrons, trapping and releasing of fast ions and/or X-rays from interelectrode aerosol ensembles are the subject of our study. The neutrons from DD microfusion, as well as the modelling of some interstellar nuclear burning due to microexplosive nucleosynthesis are discussed. The value of neutron yield from DD fusion in interelectrode space varies and amounts to ∼ 105-107/4 per shot under ≈ 1 J of total energy deposited to create all discharge processes.

  8. Temporal behaviour of the thermal model of hard X-ray bursts

    Science.gov (United States)

    Mackinnon, A. L.

    1985-01-01

    A simple, analytic model is presented of a hot, thermal hard X-ray source, continuously heated, bounded by ion-acoustic conduction fronts, and expanding in a loop. The model is used to investigate the assumption that the 'rise time' of the X-ray emission is approximately given by the loop length divided by the ion-sound speed appropriate to the peak temperature. It is found that a freely-expanding source does not behave in this way; instead, the rise time is symptomatic of the timescale for primary energy release. If the energy release rate does not fall significantly before the source fills the loop, however, then this assumption may be approximately satisfied, if a condition on the temporal behavior of the energy release is satisfied. Finally, some remarks on the relative timing of temperature and emission measure peaks are made, and possible further applications mentioned of the results presented herein.

  9. Burst and Persistent Emission Properties during the Recent Active Episode of the Anomalous X-Ray Pulsar 1E 1841-045

    Science.gov (United States)

    Lin, Lin; Kouveliotou, Chryssa; Gogus, Ersin; van der Horst, Alexander J.; Watts, Anna L.; Baring, Matthew G.; Kaneko, Yuki; Wijers, Ralph A. M. J.; Woods, Peter M.; Barthelmy, Scott; Burgess, J. Michael; Chaplin, Vandiver; Gehrels, Neil; Goldstein, Adam; Granot, Jonathan; Guiriec, Sylvain; Mcenery, Julie; Preece, Robert D.; Tierney, David; van der Klis, Michiel; von Kienlin, Andreas; Zhang, Shuang Nan

    2011-01-01

    SWift/BAT detected the first burst from 1E 1841-045 in May 2010 with intermittent burst activity recorded through at least July 2011. Here we present Swift and Fermi/GBM observations of this burst activity and search for correlated changes to the persistent X-ray emission of the source. The T90 durations of the bursts range between 18 - 140 ms, comparable to other magnetar burst durations, while the energy released in each burst ranges between (0.8-25) x 1038 erg, which is in the low side of SGR bursts. We find that the bursting activity did not have a significant effect on the persistent flux level of the source. We argue that the mechanism leading to this sporadic burst activity in IE 1841-045 might not involve large scale restructuring (either crustal or magnetospheric) as seen in other magnetar sources.

  10. Flares from Galactic Centre pulsars: a new class of X-ray transients?

    Science.gov (United States)

    Giannios, Dimitrios; Lorimer, Duncan R.

    2016-06-01

    Despite intensive searches, the only pulsar within 0.1 pc of the central black hole in our Galaxy, Sgr A*, is a radio-loud magnetar. Since magnetars are rare among the Galactic neutron star population, and a large number of massive stars are already known in this region, the Galactic Centre (GC) should harbour a large number of neutron stars. Population syntheses suggest several thousand neutron stars may be present in the GC. Many of these could be highly energetic millisecond pulsars which are also proposed to be responsible for the GC gamma-ray excess. We propose that the presence of a neutron star within 0.03 pc from Sgr A* can be revealed by the shock interactions with the disc around the central black hole. As we demonstrate, these interactions result in observable transient non-thermal X-ray and gamma-ray emission over time-scales of months, provided that the spin-down luminosity of the neutron star is Lsd ˜ 1035 erg s-1. Current limits on the population of normal and millisecond pulsars in the GC region suggest that a number of such pulsars are present with such luminosities.

  11. Flares from Galactic centre pulsars: a new class of X-ray transients?

    CERN Document Server

    Giannios, Dimitrios

    2016-01-01

    Despite intensive searches, the only pulsar within 0.1 pc of the central black hole in our Galaxy, Sgr A*, is a radio-loud magnetar. Since magnetars are rare among the Galactic neutron star population, and a large number of massive stars are already known in this region, the Galactic centre (GC) should harbor a large number of neutron stars. Population syntheses suggest several thousand neutron stars may be present in the GC. Many of these could be highly energetic millisecond pulsars which are also proposed to be responsible for the GC gamma-ray excess. We propose that the presence of a neutron star within 0.03~pc from Sgr~A* can be revealed by the shock interactions with the disk around the central black hole. As we demonstrate, these interactions result in observable transient non-thermal X-ray and gamma-ray emission over timescales of months, provided that the spin down luminosity of the neutron star is L_{sd}~10^{35} erg/s. Current limits on the population of normal and millisecond pulsars in the GC regi...

  12. Solar and stellar flare observations using WATCH

    DEFF Research Database (Denmark)

    Brandt, Søren; Lund, Niels; Rao, A. R.

    1988-01-01

    The Danish experiment WATCH (Wide Angle Telescope for Cosmic Hard X-rays) is to be flown on board the Soviet satellite GRANAT in middle of 1989. The performance characteristics of the WATCH instrument is described. It is estimated that WATCH can detect about 100 solar hard X-ray bursts per day....... WATCH can also detect about 40 energetic stellar soft X-ray flares, similar to the fast transient X-ray emissions detected by the Ariel V satellite....

  13. Search for galactic sources and X-ray bursts with spectrometers of the Kosmos-914 satellite in the energy range of 20-320 keV

    International Nuclear Information System (INIS)

    The results of observations carried out with two scintillation spectrometers of ''Kosmos-914'' satellite used for searches for bursts of galactic hard X-rays are described. The comparison of the results obtained with ''Kosmos-428'' and ''Kosmos-856'' satellites is given. The results of observation of the Whale constellation and the celestial sphere area near the centre of Galaxy are given, where, according to the data of ''Kosmos-428'' satellite the presence of X-ray sources was experted

  14. Amplitude and phase perturbations on VLF/LF signals at Belgrade due to X-ray flare intensity

    Science.gov (United States)

    Sulic, Desanka

    2016-07-01

    Narrowband very low frequency (VLF, 3-30 kHz) and low frequency (LF, 30-300 kHz) radio signals are powerful tool for long-range remote sensing of the ionospheric D-region electron density. Propagation of VLF/LF signals emitted by man-made transmitters takes place in the Earth-ionosphere waveguide and strongly depends on the electrical properties of the ionosphere. Changes in the D-region electron density cause changes in the received amplitude and phase on VLF/LF signals. Comparing the measured VLF/LF perturbations with LWPC simulations based on the predicted changes to the D-region, so as to infer the average D-region electron density profiles along the waveguide. The data were recorded at a Belgrade (44.85 ^{0} N, 20.38 ^{0} E) Serbia by AbsPAL and AWESOME receivers since 2003 and 2008 up to 2015, respectively. The first purpose of this paper is to give an account on the dropping amplitude phenomena on one long and three short VLF paths. The NAA-BEL path is sufficiently long, D = 6540 km and oriented west-east to show well-developed sunrise and sunset effects on amplitude and phase. Measured NAA/24.00 kHz signal at Belgrade shows three amplitude minima in time interval when sunrise reaches Belgrade and Maine, USA. Similar but less evident changes occur in time interval defined by sunsets at receiver and transmitter sites. The results show that at the times of amplitude minima the rate of change of phase becomes quite large. GQD/22.10 kHz, DHO/23.40 kHz and NSC/45.90 kHz signals propagate over short paths, D flare. During occurrence of solar flare the altitude profile of ionospheric conductivity changes, a VLF/LF signal reflects from lower height and these changes result that VLF/LF propagation is performed with more discrete modes than in normal ionospheric condition. Amplitude and phase perturbations on different VLF/LF signals observed at Belgrade have sensitive dependence on: X-ray flare intensity, solar zenith angle, occurrence of solar flare under solar

  15. Doppler imaging an X-ray flare on the ultrafast rotator BO Mic - A contemporaneous multiwavelength study using XMM-Newton and VLT

    CERN Document Server

    Wolter, U; Schmitt, J H M M; Ness, J U

    2007-01-01

    We present an analysis of contemporaneous photospheric, chromospheric and coronal structures on the highly active K-dwarf star BO Mic (Speedy Mic). We localize a moderate flare in the stellar atmosphere and study its energetics, size and thermal behaviour. The analysis is based on strictly simultaneous X-ray, UV- and optical observations carried out by XMM-Newton and the VLT. We use Doppler imaging and related methods for the localization of features. Based on X-ray spectroscopy we study the the coronal plasma in and outside the flare. The flare emits in X-rays and UV, but is not detected in white light; it is located at intermediate latitude between an extended spot group and the weakly spotted pole. We estimate its height below 0.4 stellar radii making it clearly distinct in longitude and height from the prominences found about two stellar radii above the surface. While BO Mic's photospheric brightness is modulated due to extended starspots, neither the chromospheric nor the X-ray emission show a pronounced...

  16. MAXI/GSC detection of a recent low-level X-ray activity and a bright hard X-ray flare from V404 Cyg

    Science.gov (United States)

    Sugimoto, J.; Negoro, H.; Kawai, N.; Tomida, H.; Nakahira, S.; Ishikawa, M.; Nakagawa, Y. E.; Mihara, T.; Sugizaki, M.; Serino, M.; Shidatsu, M.; Takagi, T.; Matsuoka, M.; Arimoto, M.; Yoshii, T.; Tachibana, Y.; Ono, Y.; Fujiwara, T.; Yoshida, A.; Sakamoto, T.; Kawakubo, Y.; Ohtsuki, H.; Tsunemi, H.; Imatani, R.; Nakajima, M.; Tanaka, K.; Masumitsu, T.; Ueda, Y.; Kawamuro, T.; Hori, T.; Tanimoto, A.; Tsuboi, Y.; Kanetou, S.; Nakamura, Y.; Sasaki, R.; Yamauchi, M.; Itoh, D.; Furuya, K.; Yamaoka, K.; Morii, M.

    2016-01-01

    Since 2015 December 23, a series of hard X-rays detections of the Galactic black hole candidate V404 Cyg (GS 2023+338) were reported with Swift-BAT (Barthelmy et al 2015 GCN #18716; ATel #8455), Fermi-GBM (Jenke at al 2015, GCN #18719; ATel #8457), and INTEGRAL-IBIS/ISGRI (Malyshev et al. ATel #8458).

  17. A Pacemaker with P=2.48 hour Modulated the Generator of Flares in the X-ray Light Curve of Sgr A* in the year 2012

    CERN Document Server

    Leibowitz, Elia M

    2016-01-01

    In an intensive observational campaign in the 9 month duration of Chandra X-ray Visionary Project that was conducted in the year 2012, 39 large X-ray flares of Sgr A* were recorded. An analysis of the times of the observed flares reveals that the 39 flares are separated in time by intervals that are grouped around integer numbers times 0.10333 days. This time interval is thus the period of a uniform grid of equally spaced points on the time axis. The grouping of the flares around tic marks of this grid is derived from the data with at least a 3.2 {\\sigma} level of statistical significance. No signal of any period can be found among 22 flares recorded by Chandra in the years 2013-2014. If the 0.10333 d period is that of a nearly circular Keplerian orbit around the blackhole at the center of the Galaxy, its radius is at 7.6 Schwarzschild radii. Large flares were more likely to be triggered when the agent responsible for their outbursts was near the peri-center phase of its slightly eccentric orbit.

  18. Fast radio bursts may originate from nearby flaring stars

    OpenAIRE

    Loeb, Abraham; Shvartzvald, Yossi; Maoz, Dan

    2013-01-01

    Six cases of fast radio bursts (FRBs) have recently been discovered. The FRBs are bright (~0.1 - 1 Jy) and brief (~ 1 ms) pulses of radio emission with dispersion measures (DMs) that exceed Galactic values, and hence FRBs have been interpreted to be at cosmological distances. We propose, instead, that FRBs are rare eruptions of flaring main-sequence stars within ~1 kpc. Rather than associating their excess DM with the intergalactic medium, we relate it to a blanket of coronal plasma around th...

  19. Correlated optical, X-ray, and γ-ray flaring activity seen with INTEGRAL during the 2015 outburst of V404 Cygni

    Science.gov (United States)

    Rodriguez, J.; Cadolle Bel, M.; Alfonso-Garzón, J.; Siegert, T.; Zhang, X.-L.; Grinberg, V.; Savchenko, V.; Tomsick, J. A.; Chenevez, J.; Clavel, M.; Corbel, S.; Diehl, R.; Domingo, A.; Gouiffès, C.; Greiner, J.; Krause, M. G. H.; Laurent, P.; Loh, A.; Markoff, S.; Mas-Hesse, J. M.; Miller-Jones, J. C. A.; Russell, D. M.; Wilms, J.

    2015-09-01

    After 25 years of quiescence, the microquasar V404 Cyg entered a new period of activity in June 2015. This X-ray source is known to undergo extremely bright and variable outbursts seen at all wavelengths. It is therefore an object of prime interest to understand the accretion-ejection connections. These can, however, only be probed through simultaneous observations at several wavelengths. We made use of the INTEGRAL instruments to obtain long, almost uninterrupted observations from 2015 June 20, 15:50 UTC to June 25, 4:05 UTC, from the optical V band up to the soft γ-rays. V404 Cyg was extremely variable in all bands, with the detection of 18 flares with fluxes exceeding 6 Crab (20-40 keV) within three days. The flare recurrence can be as short as ~20 min from peak to peak. A model-independent analysis shows that the >6 Crab flares have a hard spectrum. A simple 10-400 keV spectral analysis of the off-flare and flare periods shows that the variation in intensity is likely to be only due to variations of a cut-off power-law component. The optical flares seem to be at least of two different types: one occurring in simultaneity with the X-ray flares, the other showing a delay greater than 10 min. The former could be associated with X-ray reprocessing by either an accretion disk or the companion star. We suggest that the latter are associated with plasma ejections that have also been seen in radio. Table 1 and Fig. 4 are available in electronic form at http://www.aanda.org

  20. X-ray Flare Spectra from the DIOGENESS Spectrometer and its concept applied to ChemiX on the Interhelioprobe spacecraft

    OpenAIRE

    Sylwester, J.; Kordywski, Z.; Plocieniak, S; Siarkowski, M.; Kowalinski, M.; Nowak, S.; Trzebinski, W; Steslinski, M.; Sylwester, B.; Stanczyk, E.; Zawerbny, R.; Szaforz, Z.; Phillips, K. J. H.; Farnik, F.; Stepanov, A.

    2014-01-01

    The {\\em DIOGENESS} X-ray crystal spectrometer on the {\\em CORONAS-F} spacecraft operated for a single month (25~August to 17~September) in 2001 but in its short lifetime obtained one hundred and forty high-resolution spectra from some eight solar flares with {\\em GOES} importance ranging from C9 to X5. The instrument included four scanning flat crystals with wavelength ranges covering the regions of \\sixiii\\ (6.65~\\AA), \\sxv\\ (5.04~\\AA), and \\caxix\\ (3.18~\\AA) X-ray lines and associated diel...

  1. CONJUGATE HARD X-RAY FOOTPOINTS IN THE 2003 OCTOBER 29 X10 FLARE: UNSHEARING MOTIONS, CORRELATIONS, AND ASYMMETRIES

    International Nuclear Information System (INIS)

    We present a detailed imaging and spectroscopic study of the conjugate hard X-ray (HXR) footpoints (FPs) observed with the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) in the 2003 October 29 X10 flare. The double FPs first move toward and then away from each other, mainly parallel and perpendicular to the magnetic neutral line, respectively. The transition of these two phases of FP unshearing motions coincides with the direction reversal of the motion of the loop-top (LT) source, and with the minima of the estimated loop length and LT height. We find temporal correlations between the HXR flux, spectral index, and magnetic field strength of each FP. The HXR flux exponentially correlates with the magnetic field strength, which also anticorrelates with the spectral index before the second HXR peak's maximum, suggesting that particle acceleration sensitively depends on the magnetic field strength and/or reconnection rate. Asymmetries are observed between the FPs: on average, the eastern FP is 2.2 times brighter in HXR flux and 1.8 times weaker in magnetic field strength, and moves 2.8 times faster away from the neutral line than the western FP; the estimated coronal column density to the eastern FP from the LT source is 1.7 times smaller. The two FPs have marginally different spectral indices. The eastern-to-western FP HXR flux ratio and magnetic field strength ratio are anticorrelated only before the second HXR peak's maximum. Neither magnetic mirroring nor column density alone can explain the totality of these observations, but their combination, together with other transport effects, might provide a full explanation. We have also developed novel techniques to remove particle contamination from HXR counts and to estimate effects of pulse pileup in imaging spectroscopy, which can be applied to other RHESSI flares in similar circumstances.

  2. New method for determining temperature and emission measure during solar flares from light curves of soft X-ray line fluxes

    International Nuclear Information System (INIS)

    I describe a new property of soft X-ray line fluxes observed during the decay phase of solar flares and a technique for using this property to determine the plasma temperature and emission measure as functions of time. The soft X-ray line fluxes analyzed in this paper were observed during the decay phase of the 1980 November 5 flare by the X-Ray Polychromator (XRP) instrument on board the Solar Maximum Mission (SMM). The resonance, intercombination, and forbidden lines of Ne IX, Mg XI, Si XIII, S XV, Ca XIX, and Fe XXV, as well as the Lyman-α line of O VIII and the resonance lines of Fe XIX, were observed. The rates at which the observed line fluxes decayed were not constant. For all but the highest temperature lines observed, the rate changed abruptly, causing the fluxes to fall at a more rapid rate later in the flare decay. These changes occurred at earlier times for lines formed at higher temperatures. This behavior is proposed to be due to the decreasing temperature of the flare plasma tracking the rise and subsequent fall of each line emissivity function. This explanation is used to empirically model the observed light curves and to estimate the temperature and the change in emission measure of the plasma as a function of time during the decay phase. Estimates are made of various plasma parameters based on the model results

  3. Temperature measurement during thermonuclear X-ray bursts with BeppoSAX

    Science.gov (United States)

    Beri, Aru; Paul, Biswajit; Orlandini, Mauro; Maitra, Chandreyee

    2016-05-01

    We have carried out a study of temperature evolution during thermonuclear bursts in LMXBs using broad band data from two instruments onboard BeppoSAX, the MECSand the PDS. However, instead of applying the standard technique of time resolved spectroscopy, we have determined the temperature in small time intervals using the ratio of count rates in the two instruments assuming a blackbody nature of burst emission and different interstellar absorption for different sources. Data from a total of twelve observations of six sources were analyzed during which 22 bursts were detected. We have obtained temperatures as high as ˜3.0 keV, even when there is no evidence of photospheric radius expansion. These high temperatures were observed in the sources within different broadband spectral states (soft and hard).

  4. Temperature Measurement during Thermonuclear X-ray Bursts with BeppoSAX

    CERN Document Server

    Beri, Aru; Orlandini, Mauro; Maitra, Chandreyee

    2015-01-01

    We have carried out a study of temperature evolution during thermonuclear bursts in LMXBs using broad band data from two instruments onboard BeppoSAX, the MECS and the PDS. However, instead of applying the standard technique of time resolved spectroscopy, we have determined the temperature in small time intervals using the ratio of count rates in the two instruments assuming a blackbody nature of burst emission and different interstellar absorption for different sources. Data from a total of twelve observations of six sources were analysed during which 22 bursts were detected. We have obtained temperatures as high as ~3.0 keV, even when there is no evidence of photospheric radius expansion. These high temperatures were observed in the sources within different broadband spectral states (soft and hard).

  5. FLARE-ASSOCIATED TYPE III RADIO BURSTS AND DYNAMICS OF THE EUV JET FROM SDO/AIA AND RHESSI OBSERVATIONS

    International Nuclear Information System (INIS)

    We present a detailed description of the interrelation between the Type III radio bursts and energetic phenomena associated with the flare activities in active region AR11158 at 07:58 UT on 2011 February 15. The timing of the Type III radio burst measured by the radio wave experiment on Wind/WAVE and an array of ground-based radio telescopes coincided with an extreme-ultraviolet (EUV) jet and hard X-ray (HXR) emission observed by SDO/AIA and RHESSI, respectively. There is clear evidence that the EUV jet shares the same source region as the HXR emission. The temperature of the jet, as determined by multiwavelength measurements by Atmospheric Imaging Assembly, suggests that Type III emission is associated with hot, 7 MK, plasma at the jet's footpoint.

  6. MAGNETICALLY DRIVEN WINDS FROM DIFFERENTIALLY ROTATING NEUTRON STARS AND X-RAY AFTERGLOWS OF SHORT GAMMA-RAY BURSTS

    International Nuclear Information System (INIS)

    Besides being among the most promising sources of gravitational waves, merging neutron star binaries also represent a leading scenario to explain the phenomenology of short gamma-ray bursts (SGRBs). Recent observations have revealed a large subclass of SGRBs with roughly constant luminosity in their X-ray afterglows, lasting 10-104 s. These features are generally taken as evidence of a long-lived central engine powered by the magnetic spin-down of a uniformly rotating, magnetized object. We propose a different scenario in which the central engine powering the X-ray emission is a differentially rotating hypermassive neutron star (HMNS) that launches a quasi-isotropic and baryon-loaded wind driven by the magnetic field, which is built-up through differential rotation. Our model is supported by long-term, three-dimensional, general-relativistic, and ideal magnetohydrodynamic simulations, showing that this isotropic emission is a very robust feature. For a given HMNS, the presence of a collimated component depends sensitively on the initial magnetic field geometry, while the stationary electromagnetic luminosity depends only on the magnetic energy initially stored in the system. We show that our model is compatible with the observed timescales and luminosities and express the latter in terms of a simple scaling relation

  7. The dependence of gamma-ray burst X-ray column densities on the model for Galactic hydrogen

    CERN Document Server

    Arcodia, Riccardo; Salvaterra, Ruben

    2016-01-01

    We study the X-ray absorption of a complete sample of 99 bright Swift gamma-ray bursts. Over the last few years, a strong correlation between the intrinsic X-ray absorbing column density (N_H(z)) and the redshift was found. This absorption excess in high-z GRBs is now thought to be due to the overlooked contribution of the absorption along the intergalactic medium, by means of both intervening objects and the diffuse warm-hot intergalactic medium along the line of sight. In this work we neglect the absorption along the IGM, because our purpose is to study the eventual effect of a radical change in the Galactic absorption model on the N_H(z) distribution. Therefore, we derive the intrinsic absorbing column densities using two different Galactic absorption models, the Leiden Argentine Bonn HI survey and the more recent model including molecular hydrogen. We find that, if on the one hand the new Galactic model considerably affects the single column density values, on the other hand there is no drastic change in ...

  8. Prompt Ultraviolet-to-Soft X-Ray Emission of Gamma-Ray Bursts: Application to GRB 031203?

    CERN Document Server

    Li, Z; Li, Zhuo; Song, Li-Ming

    2004-01-01

    We discuss the prompt emission of GRBs, allowing for $\\gamma\\gamma$ pair production and synchrotron self-absorption. The observed hard spectra suggest heavy pair-loading in GRBs. The re-emission of the generated pairs results in the energy transmission from high-energy gamma-rays to long-wavelength radiation. Due to strong self-absorption, the synchrotron radiation by pairs is in optically thick regime. Thus, the re-emission would appear as a thermal-like spectral bump in the extreme-ultraviolet/soft X-ray band, other than the peak from the main burst. Recently, the prompt soft X-ray emission of GRB 031203 was detected thanks to the discovery of a delayed dust echo, and it seems to be consistent with the model prediction of a double-peak structure. The confirmation of the thermal-like feature and the double-peak structure by observation would indicate that the dominant radiation mechanism in GRBs is synchrotron rather than inverse-Compton radiation.

  9. Impulsive Phase Coronal Hard X-ray Sources in an X3.9 Class Solar Flare

    CERN Document Server

    Chen, Qingrong

    2012-01-01

    [Abridged]We present analysis of a pair of unusually energetic coronal hard X-ray (HXR) sources detected by RHESSI during the impulsive phase of an X3.9 class solar flare on 2003 November 3, which simultaneously shows two intense footpoint (FP) sources. A distinct loop top (LT) coronal source is detected up to ~150 keV and a second (upper) coronal source up to ~80 keV. These photon energies are much higher than commonly observed in coronal sources and pose grave modeling challenges. The LT source in general appears higher in altitude with increasing energy and exhibits a more limited motion compared to the expansion of the thermal loop. The high energy LT source shows an impulsive time profile and its nonthermal power law spectrum exhibits soft-hard-soft evolution during the impulsive phase, similar to the FP sources. The upper coronal source exhibits an opposite spatial gradient and a similar spectral slope compared to the LT source. These properties are consistent with the model of stochastic acceleration o...

  10. X-ray spectral and timing behavior of Scorpius X-1. Spectral hardening during the flaring branch

    CERN Document Server

    Titarchuk, Lev; Shrader, Chris

    2015-01-01

    We present an analysis of the spectral and timing properties of X-ray emission from the Z-source Sco~X-1 during its evolution between the Horizontal (HB) and Flaring(FB) branches observed with the RXTE during the 1996 -- 2002 period. We find that the broad-band (3 - 250 keV) energy spectra during all spectral states can be adequately reproduced by a model, consisting of two Comptonized components and an iron-line. We suggest that the seed photons of kT_s1~0.7 keV coming from the disk and of temperature kT_s2~1.8 keV coming from the neutron star (NS) are each upscattered by hot electrons of a "Compton cloud" (herein Comptb1 and Comptb2 components respectively with which are associated similarly subscripted parameters). The photon power-law index Gamma_{2} is almost constant (Gamma_{2}~2) for all spectral states. In turn, Gamma_{1} demonstrates a two-phase behavior with the spectral state: Gamma_{1} is quasi-constant at the level Gamma_{1}~2 for the HB-NB and Gamma_{1} is less than 2, namely in the range of 1.3...

  11. Simulated Solar Flare X-Ray and Thermal Cycling Durability Evaluation of Hubble Space Telescope Thermal Control Candidate Replacement Materials

    Science.gov (United States)

    deGroh, Kim K.; Banks, Bruce A.; Sechkar, Edward A.; Scheiman, David A.

    1998-01-01

    During the Hubble Space Telescope (HST) second servicing mission (SM2), astronauts noticed that the multilayer insulation (MLI) covering the telescope was damaged. Large pieces of the outer layer of MLI (aluminized Teflon fluorinated ethylene propylene (Al-FEP)) were torn in several locations around the telescope. A piece of curled up Al-FEP was retrieved by the astronauts and was found to be severely embrittled, as witnessed by ground testing. Goddard Space Flight Center (GSFC) organized a HST MLI Failure Review Board (FRB) to determine the damage mechanism of FEP in the HST environment, and to recommend replacement insulation material to be installed on HST during the third servicing mission (SM3) in 1999. Candidate thermal control replacement materials were chosen by the FRB and tested for environmental durability under various exposures and durations. This paper describes durability testing of candidate materials which were exposed to charged particle radiation, simulated solar flare x-ray radiation and thermal cycling under load. Samples were evaluated for changes in solar absorptance and tear resistance. Descriptions of environmental exposures and durability evaluations of these materials are presented.

  12. Hard X-ray and Microwave Simulation of 2015-06-22 M6.6 flare

    Science.gov (United States)

    Kuroda, Natsuha; Wang, Haimin; Gary, Dale E.; Fleishman, Gregory D.; Nita, Gelu M.; Chen, Bin; Xu, Yan; Jing, Ju

    2016-05-01

    It is well known that the time profiles of the hard X-ray (HXR) emission and the microwave (MW) emission during the impulsive phase of the solar flare are well correlated, and this has led to the expectation that these emissions come from a common population of flare-accelerated electrons. However, the energy ranges of the electrons producing two emissions are believed to be different (below and above several hundred keV for HXR-producing and MW-producing electrons, respectively), and some studies have shown that the indices of their energy spectra may differ as well. To better understand the energy distributions of the electrons producing these emissions, we present realistic forward-fit simulations of the HXR and the MW emissions of 2015 June 22, M6.6 flare using the newly developed, IDL-based platform GX simulator. We use the 3D magnetic field model extrapolated from magnetogram data from the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO), the images and the electron energy distribution parameters deduced from the photon spectrum from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), and the spatially integrated MW spectrum and the cross-correlated amplitude data from the Expanded Owens Valley Solar Array (EOVSA) to guide the modeling. We have observed a possible above the-loop-top HXR source in 20-25 keV image, well separated from the source seen in 6-12 keV that is typically interpreted as a thermal loop-top source. Therefore, we simulate the HXR emissions by combining two flux tubes at different heights: the lower loop dominated by thermal electrons and the higher loop dominated by nonthermal electrons. The MW and HXR emissions produced from the forward-fit model are compared with observations to investigate possible differences in the energy spectra of the HXR-producing and the MW-producing electrons and what they can tell us about particle acceleration.

  13. Correlated optical, X-ray, and gamma-ray flaring activity seen with INTEGRAL during the 2015 outburst of V404 Cygni

    CERN Document Server

    Rodriguez, J; Alfonso-Garzón, J; Siegert, T; Zhang, X -L; Grinberg, V; Savchenko, V; Tomsick, J A; Chenevez, J; Clavel, M; Corbel, S; Diehl, R; Domingo, A; Gouiffès, C; Greiner, J; Krause, M G H; Laurent, P; Loh, A; Markoff, S; Mas-Hesse, J M; Miller-Jones, J C A; Russell, D M; Wilms, J

    2015-01-01

    After 25 years of quiescence, the microquasar V404 Cyg entered a new period of activity in June 2015. This X-ray source is known to undergo extremely bright and variable outbursts seen at all wavelengths. It is therefore an object of prime interest to understand the accretion-ejection connections. These can, however, only be probed through simultaneous observations at several wavelengths. We made use of the INTEGRAL instruments to obtain long, almost uninterrupted observations from the optical V-band, up to the soft gamma-rays. V404 Cyg was extremely variable in all bands, with the detection of 18 flares with fluxes exceeding 6 Crab (20-40 keV) within 3 days. The flare recurrence can be as short as 20~min from peak to peak. A model-independent analysis shows that the >6 Crab flares have a hard spectrum. A preliminary 10-400 keV spectral analysis of the off-flare and flare periods shows that the variation in intensity is likely to be due to variations of a cut-off power law component only. At X-ray and gamma-r...

  14. Search for galactic sources of X-ray bursts with scintillation spectrometers of the Kosmos-856 satellite in the energy range of 20-320 keV

    International Nuclear Information System (INIS)

    Search for galactic sources of X-pay bursts with a scintillation spectrometer of ''Kosmos-856'' satellite has given a negative result. During 21 hours of observations with two independent detectors not one burst of X-rays with the energy flux P 2x10-7 erg/cm2 has been found in the energy range 20-320 keV and duration 10s. This result disagrees with the data obtained with the ''Kosmos-428'' satellite

  15. 2006 May-July Major Radio Flare episodes in Cygnus X-3: spectro-timing analysis of the X-ray data

    CERN Document Server

    Koljonen, K I I; Hannikainen, D C; Droulans, R

    2012-01-01

    We analyse in detail the X-ray data of the microquasar Cygnus X-3 obtained during major radio flaring episodes in 2006 with multiple observatories. The analysis consists of two parts: probing the fast (~ 1 minute) X-ray spectral evolution with Principal Component Analysis followed by subsequent spectral fits to the time-averaged spectra (~ 3 ks). Based on the analysis we find that the overall X-ray variability during major flaring episodes can be attributed to two principal components whose evolution based on spectral fits is best reproduced by a hybrid Comptonization component and a bremsstrahlung or saturated thermal Comptonization component. The variability of the thermal component is found to be linked to the change in the X-ray/radio spectral state. In addition, we find that the seed photons for the Comptonization originate in two seed photon populations that include the additional thermal emission and emission from the accretion disc. The Comptonization of the photons from the thermal component dominate...

  16. Propagation of thermonuclear flames on rapidly rotating neutron stars extreme weather during type I X-ray bursts

    CERN Document Server

    Spitkovsky, A; Ushomirsky, G; Spitkovsky, Anatoly; Levin, Yuri; Ushomirsky, Greg

    2002-01-01

    We analyze the global hydrodynamic flow in the ocean of an accreting, rapidly rotating, non-magnetic neutron star in an LMXB during a type I X-ray burst. Our analysis takes into account the rapid rotation of the star and the lift-up of the burning ocean during the burst. We find a new regime for spreading of a nuclear burning front, where the flame is carried along a coherent shear flow across the front. If turbulent viscosity is weak, the speed of flame propagation is ~20 km/s, while, if turbulent viscosity is dynamically important, the flame speed increases, and reaches the maximum value, ~300 km/s, when the eddy overturn frequency is comparable to the Coriolis parameter. We show that, due to rotationally reduced gravity, the thermonuclear runaway is likely to begin on the equator. The equatorial belt is ignited first, and the flame then propagates from the equator to the poles. Inhomogeneous cooling (equator first, poles second) drives strong zonal currents which may be unstable to formation of Jupiter-typ...

  17. Two types of softening detected in X-ray afterglows of Swift bursts: internal and external shock origins?

    CERN Document Server

    Qin, Y -P; Fan, J H; Lu, R -J

    2008-01-01

    The softening process observed in the steep decay phase of early X-ray afterglows of Swift bursts has remained a puzzle since its discovery. The softening process can also be observed in the later phase of the bursts and its cause has also been unknown. Recently, it was suggested that, influenced by the curvature effect, emission from high latitudes would shift the Band function spectrum from higher energy band to lower band, and this would give rise to the observed softening process accompanied by a steep decay of the flux density. The curvature effect scenario predicts that the terminating time of the softening process would be correlated with the duration of the process. In this paper, based on the data from the UNLV GRB group web-site, we found an obvious correlation between the two quantities. In addition, we found that the softening process can be divided into two classes: the early type softening ($t_{s,max}\\leq "4000"s$) and the late type softening ($t_{s,max} > "4000"s$). The two types of softening s...

  18. Bursting SN 1996cr's Bubble: Hydrodynamic and X-ray Modeling of its Circumstellar Medium

    CERN Document Server

    Dwarkadas, Vikram V; Bauer, Franz

    2010-01-01

    SN1996cr is one of the five closest SNe to explode in the past 30 years. Due to its fortuitous location in the Circinus Galaxy at ~ 3.7 Mpc, there is a wealth of recently acquired and serendipitous archival data available to piece together its evolution over the past decade, including a recent 485 ks Chandra HETG spectrum. In order to interpret this data, we have explored hydrodynamic simulations, followed by computations of simulated spectra and light curves under non-equilibrium ionization conditions, and directly compared them to the observations. Our simulated spectra manage to fit both the X-ray continuum and lines at 4 epochs satisfactorily, while our computed light curves are in good agreement with additional flux-monitoring data sets. These calculations allow us to infer the nature and structure of the circumstellar medium, the evolution of the SN shock wave, and the abundances of the ejecta and surrounding medium. The data imply that SN 1996cr exploded in a low-density medium before interacting with ...

  19. High-temperature differential emission measure and altitude variations in the temperature and density of solar flare coronal X-ray sources

    CERN Document Server

    Jeffrey, Natasha; Dennis, Brian

    2015-01-01

    The detailed knowledge of plasma heating and acceleration region properties presents a major observational challenge in solar flare physics. Using the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), the high temperature differential emission measure, DEM(T), and the energy-dependent spatial structure of solar flare coronal sources are studied quantitatively. The altitude of the coronal X-ray source is observed to increase with energy by ~+0.2 arcsec/keV between 10 and 25 keV. Although an isothermal model can fit the thermal X-ray spectrum observed by RHESSI, such a model cannot account for the changes in altitude, and multi-thermal coronal sources are required where the temperature increases with altitude. For the first time, we show how RHESSI imaging information can be used to constrain the DEM(T) of a flaring plasma. We develop a thermal bremsstrahlung X-ray emission model with inhomogeneous temperature and density distributions to simultaneously reproduce: i) DEM(T), ii) altitude as a function of ...

  20. Correlated optical, X-ray, and γ-ray flaring activity seen with INTEGRAL during the 2015 outburst of V404 Cygni

    DEFF Research Database (Denmark)

    Rodriguez, J.; Cadolle Bel, M.; Alfonso-Garzón, J.;

    2015-01-01

    . These can, however, only be probed through simultaneous observations at several wavelengths. We made use of the INTEGRAL instruments to obtain long, almost uninterrupted observations from 2015 June 20, 15:50 UTC to June 25, 4:05 UTC, from the optical V band up to the soft y-rays. V404 Cyg was extremely...... variable in all bands, with the detection of 18 flares with fluxes exceeding 6 Crab (20-40 keV) within three days. The flare recurrence can be as short as ~20 min from peak to peak. A model-independent analysis shows that the >6 Crab flares have a hard spectrum. A simple 10-400 keV spectral analysis of the...... off-flare and flare periods shows that the variation in intensity is likely to be only due to variations of a cut-off power-law component. The optical flares seem to be at least of two different types: one occurring in simultaneity with the X-ray flares, the other showing a delay greater than 10 min...

  1. Two types of softening detected in x-ray afterglows of Swift bursts: internal and external shock origins?

    International Nuclear Information System (INIS)

    The softening process observed in the steep decay phase of early x-ray afterglows of Swift bursts has remained a puzzle since its discovery. The softening process can also be observed in the later phase of the bursts and its cause has also been unknown. Recently, it was suggested that, influenced by the curvature effect, emission from high latitudes would shift the Band function spectrum from a higher energy band to a lower band, and this would give rise to the observed softening process accompanied by a steep decay of the flux density. The curvature effect scenario predicts that the terminating time of the softening process would be correlated with the duration of the process. In this paper, on the basis of the data from the UNLV GRB (University of Nevada, Las Vegas, Gamma-Ray Burst) group web-site, we found an obvious correlation between the two quantities. In addition, we found that the softening process can be divided into two classes: the early type softening (ts,max≤'4000' s) and the late type softening (ts,max>'4000' s). The two types of softening show different behaviors in the duration versus terminating time plot. In the relation between the variation rates of the flux density and spectral index during the softening process, a discrepancy between the two types of softening is also observed. According to their timescales and the discrepancy between them, we propose that the two types are of different origins: the early type is of internal shock origin and the late type is of external shock origin. The early softening is related to the steep decay just following the prompt emission, whereas for the late decay one typically conceives the transition from flat decay to late afterglow decay. We suspect that there might be a great difference in Lorentz factor between the two classes, which is responsible for the observed discrepancy

  2. Evidence for Harmonic Content and Frequency Evolution of Oscillations During the Rising Phase of X-ray Bursts From 4U 1636-536

    Science.gov (United States)

    Bgattacharyya, Sudip; Strohmayer, E.

    2005-01-01

    We report on a study of the evolution of burst oscillation properties during the rising phase of X-ray bursts from 4U 1636-536 observed with the proportional counter array (PCA) on board the Rossi X-Ray Timing Explorer (RXTE) . We present evidence for significant harmonic structure of burst oscillation pulses during the early rising phases of bursts. This is the first such detection in burst rise oscillations, and is very important for constraining neutron star structure parameters and the equation of state models of matter at the core of a neutron star. The detection of harmonic content only during the initial portions of the burst rise is consistent with the theoretical expectation that with time the thermonuclear burning region becomes larger, and hence the fundamental and harmonic amplitudes both diminish. We also find, for the first time from this source, strong evidence of oscillation frequency increase during the burst rise. The timing behavior of harmonic content, amplitude, and frequency of burst rise oscillations may be important in understanding the spreading of thermonuclear flames under the extreme physical conditions on neutron star surfaces.

  3. Analisis Klaster K-Means dari Data Luas Grup Sunspot dan Data Grup Sunspot Klasifikasi Mc.Intosh yang membangkitkan Flare Soft X-Ray dan H-alpha

    Directory of Open Access Journals (Sweden)

    Siti Jumaroh

    2015-12-01

    Full Text Available Analisis klaster merupakan teknik interpendensi yang mengelompokkan suatu objek berdasarkan kemiripan dan kedekatan jarak antar objek. Pengelompokan objek dengan jumlah banyak membutuhkan waktu yang lama. Salah satu analisis klaster yang dapat digunakan dalam situasi ini adalah analisis klaster non hierarki, yaitu K-means. Pada artikel ini mengelompokkan data luas grup sunspot dan data grup sunspot klasifikasi Mc.Intosh yang membangkitkan flare soft X-Ray dan Hα. Untuk mengetahui luas grup sunspot dan grup sunspot klasifikasi Mc.Intosh yang berpeluang membangkitkan flare soft X-Ray dan Hα dengan intensitas ledakan yang tinggi dan rendah. Berdasarkan hasil analisis, diperoleh dua klaster yaitu klaster pertama yang tergolong mampu membangkitkan flare Soft X-Ray dan Hα dengan intensitas yang tinggi. Sedangkan klaster kedua yang tergolong mampu membangkitkan flare Soft X-Ray dan Hα dengan intensitas yang rendah

  4. The dependence of gamma-ray burst X-ray column densities on the model for Galactic hydrogen

    Science.gov (United States)

    Arcodia, R.; Campana, S.; Salvaterra, R.

    2016-05-01

    We study the X-ray absorption of a complete sample of 99 bright Swift gamma-ray bursts (GRBs). In recent years, a strong correlation has been found between the intrinsic X-ray absorbing column density (NH(z)) and the redshift. This absorption excess in high-z GRBs is now thought to be due to the overlooked contribution of the absorption along the intergalactic medium (IGM), by means of both intervening objects and the diffuse warm-hot intergalactic medium along the line of sight. In this work we neglect the absorption along the IGM, because our purpose is to study the eventual effect of a radical change in the Galactic absorption model on the NH(z) distribution. Therefore, we derive the intrinsic absorbing column densities using two different Galactic absorption models: the Leiden Argentine Bonn HI survey and the more recent model that includes molecular hydrogen. We find that if, on the one hand, the new Galactic model considerably affects the single column density values, on the other hand, there is no drastic change in the distribution as a whole. It becomes clear that the contribution of Galactic column densities alone, no matter how improved, is not sufficient to change the observed general trend and it has to be considered as a second order correction. The cosmological increase of NH(z) as a function of redshift persists and, to explain the observed distribution, it is necessary to include the contribution of both the diffuse intergalactic medium and the intervening systems along the line of sight of the GRBs.

  5. The 100-month Swift catalogue of supergiant fast X-ray transients I. BAT on-board and transient monitor flares

    CERN Document Server

    Romano, P; Palmer, D M; Ducci, L; Esposito, P; Vercellone, S; Evans, P A; Guidorzi, C; Mangano, C; Kennea, J A; Barthelmy, S D; Burrows, D N; Gehrels, N

    2013-01-01

    We investigate the characteristics of bright flares for a sample of supergiant fast X-ray transients and their relation to the orbital phase. We have retrieved all Swift/BAT Transient Monitor light curves, and collected all detections in excess of $5\\sigma$ from both daily- and orbital-averaged light curves in the time range of 2005-Feb-12 to 2013-May-31. We also considered all on-board detections as recorded in the same time span and selected those within 4 arcmin of each source in our sample and in excess of $5\\sigma$. We present a catalogue of over a thousand BAT flares from 11 SFXTs, down to 15-150keV fluxes of $\\sim6\\times10^{-10}$ erg cm$^{-2}$ s$^{-1}$ (daily timescale) and $\\sim1.5\\times10^{-9}$ erg cm$^{-2}$ s$^{-1}$ (orbital timescale, averaging $\\sim800$s) and spanning 100 months. The great majority of these flares are unpublished. This population is characterized by short (a few hundred seconds) and relatively bright (in excess of 100mCrab, 15-50keV) events. In the hard X-ray, these flares last in...

  6. The breakdown of the power-law frequency distributions for the hard X-ray peak count rates of solar flares

    International Nuclear Information System (INIS)

    The frequency distribution for several characteristics of a solar flare obeys a power law only above a certain threshold, below which there is an apparent loss of small scale events presumably caused by limited instrumental sensitivity and the corresponding event selection bias. It is also possible that this deviation in the power law can have a physical origin in the source. We propose two fitting models incorporating a power law distribution with a low count rate cutoff plus a noise component for the frequency distribution of the hard X-ray peak count rate of all solar flare samples obtained with HXRBS/SMM and BATSE/CGRO observations. Our new fitting method produces the same power-law index as previously developed methods, a low cutoff of the power-law function and its corresponding noise level, which is consistent with measurements of the actual noise level of the hard X-ray count rate. We found that the fitted low cutoff appears to be related to the noise level, i.e., flares are only recognized when their peak count rate is 3σ greater than noise. Therefore, the fitted low cutoff, which is smaller than the aforementioned threshold, might be attributed to selection bias, and probably not to the actual count rate cutoff in flares at smaller scales. Whether or not the actual low cutoff physically exists needs to be checked by future observations with increased sensitivities

  7. Observations of quasi-periodic solar X-ray emission as a result of MHD oscillations in a system of multiple flare loops

    CERN Document Server

    Zimovets, I V

    2009-01-01

    We investigate the solar flare of 20 October 2002. The flare was accompanied by quasi-periodic pulsations (QPP) of both thermal and nonthermal hard X-ray emissions (HXR) observed by RHESSI in the 3-50 keV energy range. Analysis of the HXR time profiles in different energy channels made with the Lomb periodogram indicates two statistically significant time periods of about 16 and 36 seconds. The 36-second QPP were observed only in the nonthermal HXR emission in the impulsive phase of the flare. The 16-second QPP were more pronounced in the thermal HXR emission and were observed both in the impulsive and in the decay phases of the flare. Imaging analysis of the flare region, the determined time periods of the QPP and the estimated physical parameters of magnetic loops in the flare region allow us to interpret the observations as follows. 1) In the impulsive phase energy was released and electrons were accelerated by successive acts with the average time period of about 36 seconds in different parts of two spati...

  8. NuSTAR OBSERVATION OF A TYPE I X-RAY BURST FROM GRS 1741.9-2853

    International Nuclear Information System (INIS)

    We report on two NuSTAR observations of GRS 1741.9-2853, a faint neutron star (NS) low-mass X-ray binary burster located 10' away from the Galactic center. NuSTAR detected the source serendipitously as it was emerging from quiescence: its luminosity was 6 × 1034 erg s–1 on 2013 July 31 and 5 × 1035 erg s–1 in a second observation on 2013 August 3. A bright, 800 s long, H-triggered mixed H/He thermonuclear Type I burst with mild photospheric radius expansion (PRE) was present during the second observation. Assuming that the luminosity during the PRE was at the Eddington level, an H mass fraction X = 0.7 in the atmosphere, and an NS mass M = 1.4 M ☉, we determine a new lower limit on the distance for this source of 6.3 ± 0.5 kpc. Combining with previous upper limits, this places GRS 1741.9-2853 at a distance of 7 kpc. Energy independent (achromatic) variability is observed during the cooling of the NS, which could result from the disturbance of the inner accretion disk by the burst. The large dynamic range of this burst reveals a long power-law decay tail. We also detect, at a 95.6% confidence level (1.7σ), a narrow absorption line at 5.46 ± 0.10 keV during the PRE phase of the burst, reminiscent of the detection by Waki et al. We propose that the line, if real, is formed in the wind above the photosphere of the NS by a resonant Kα transition from H-like Cr gravitationally redshifted by a factor 1 + z = 1.09, corresponding to a radius range of 29.0-41.4 km for a mass range of 1.4-2.0 M ☉

  9. EVIDENCE FOR NEW RELATIONS BETWEEN GAMMA-RAY BURST PROMPT AND X-RAY AFTERGLOW EMISSION FROM 9 YEARS OF SWIFT

    International Nuclear Information System (INIS)

    When a massive star explodes as a gamma-ray burst (GRB), information about the explosion is retained in the properties of the prompt and afterglow emission. We report on new relations between the prompt and X-ray afterglow emission of Swift-detected GRBs found from Burst Alert Telescope (BAT) and X-Ray Telescope data covering 2004 December to 2013 August (754 in total). These relations suggest that the prompt and afterglow emission are closely linked. In particular, we find very strong correlations between the BAT 15-150 keV T 90 and the break times before and after the plateau phase in the 0.3-10 keV X-ray afterglow light curves. We also find a strong anticorrelation between the photon index of the GRB prompt emission and the X-ray spectral slope of the afterglow. Moreover, anticorrelations exist between the rest-frame peak energy in the prompt emission E peak, z and the X-ray afterglow decay slope during the plateau phase and the break times after the plateau phase. The rest- frame break times before and after the plateau phase are also anticorrelated with the rest-frame 15-150 keV luminosity and the isotropic energy during the prompt emission. A principal component analysis suggests that the GRB properties are primarily driven by the luminosity/energy release in the 15-150 keV band. Luminosity functions derived at different redshifts from a log N-log S analysis indicate that the density of bright bursts is significantly lower in the local universe than in the universe at z ≈ 3, where the density of bright GRBs peaks. Using cluster analysis, we find that the duration of BAT-detected short GRBs is less than 1 s. We also present a catalog of all Swift onboard-detected bursts

  10. X-ray absorption evolution in Gamma-Ray Bursts: intergalactic medium or evolutionary signature of their host galaxies?

    CERN Document Server

    Starling, R L C; Tanvir, N R; Scott, A E; Wiersema, K; O'Brien, P T; Levan, A J; Stewart, G C

    2013-01-01

    The intrinsic X-ray emission of Gamma-Ray Bursts (GRBs) is often found to be absorbed over and above the column density through our own galaxy. The extra component is usually assumed to be due to absorbing gas lying within the host galaxy of the GRB itself. There is an apparent correlation between the equivalent column density of hydrogen, N(H,intrinsic) (assuming it to be at the GRB redshift), and redshift, z, with the few z>6 GRBs showing the greatest intrinsic column densities. We investigate the N(H,intrinsic) - z relation using a large sample of Swift GRBs, as well as active galactic nuclei (AGN) and quasar samples, paying particular attention to the spectral energy distributions of the two highest redshift GRBs. Various possible sample biases and systematics that might produce such a correlation are considered, and we conclude that the correlation is very likely to be real. This may indicate either an evolutionary effect in the host galaxy properties, or a contribution from gas along the line-of-sight, ...

  11. X-ray flare from a B9 + post-T Tauri star system in the field of the Seyfert Galaxy III Zw 2

    International Nuclear Information System (INIS)

    The serendipitous detection of X-ray emission from the visual binary HD 560, consisting of a B-type primary and a later-type secondary, is reported. This system was seen in the field of the Seyfert type I galaxy III Zw 2, which was observed four times by Exosat. During one of these observations, the serendipitous source was observed to flare in both low-energy and medium-energy experiments. It is shown here that the observed variability was entirely due to the serendipitous source. It is argued that virtually all of the X-ray flux from the binary came from this late-type component, and that this component is probably a post-T Tauri star. 33 references

  12. Multi-thermal representation of the kappa-distribution of solar flare electrons and application to simultaneous X-ray and EUV observations

    CERN Document Server

    Battaglia, Marina; Kontar, Eduard P

    2015-01-01

    Acceleration of particles and plasma heating is one of the fundamental problems in solar flare physics. An accurate determination of the spectrum of flare energized electrons over a broad energy range is crucial for our understanding of aspects such as the acceleration mechanism and the total flare energy. Recent years have seen a growing interest in the kappa-distribution as representation of the total spectrum of flare accelerated electrons. In this work we present the kappa-distribution as a differential emission measure. This allows for inferring the electron distribution from X-ray observations and EUV observations by simultaneously fitting the proposed function to RHESSI and SDO/AIA data. This yields the spatially integrated electron spectra of a coronal source between less than 0.1 keV up to several tens of keV. The method is applied to a single-loop GOES C4.1 flare. The results show that the total energy can only be determined accurately by combining RHESSI and AIA observations. Simultaneously fitting...

  13. Are Homologous Radio Bursts Driven by Solar Post-Flare Loops?

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Three particularly complex radio bursts (2001 October 19, 2001 April 10 and 2003 October 26) obtained with the spectrometers (0.65-7.6 GHz) at the National Astronomical Observatories, Chinese Academy of Sciences (NAOC, Beijing and Yunnan) and other instruments (NoRH, TRACE and SXT) are presented. They each have two groups of peaks occurring in different frequency ranges (broad-band microwave and narrow-band decimeter wavelengths). We stress that the second group of burst peaks that occurred in the late phase of the flares and associated with post-flare loops may be homologous radio bursts. We think that they are driven by the post-flare loops. In contrast to the time profiles of the radio bursts and the images of coronal magnetic polarities, we are able to find that the three events are caused by the active regions including main single-bipole magnetic structures, which are associated with multipole magnetic structures during the flare evolutions. In particular, we point out that the later decimetric radio bursts are possibly the radio counterparts of the homologous flares (called "homologous radio bursts" by us), which are also driven by the single-bipole magnetic structures. By examining the evolutions of the magnetic polarities of sources (17 GHz),we could presume that the drivers of the homologous radio bursts are new and/or recurring appearances/disappearances of the magnetic polarities of radio sources, and that the triggers are the magnetic reconnections of single-bipole configurations.

  14. A synchrotron/inverse Compton interpretation of a solar burst producing fast pulses at λ < 3 mm and hard X-rays

    International Nuclear Information System (INIS)

    The recently discovered new class of solar burst emission component exhibiting very fast pulses (durations ∼ 60 ms) at mm-waves only (λ 13 Hz, the burst sources must be short lived (∼ 60 ms), very small (7cm) and exhibiting high apparent brightness temperature (> or approx. 1010 K). This study suggest further theoretical studies on the nature of the primary acceleration sources, and on their location in the solar atmosphere. A number of crucial observational tests are needed, specially in the sub-mm and infrared range of frequencies, as well as at ratio and hard X-rays with simultaneous high spatial and time resolution. (Author)

  15. Amplitude and phase changes on VLF/LF radio signals depending on solar zenith angle during occurrences of solar X-ray flares

    Science.gov (United States)

    Sulic, Desanka; Sreckovic, Vladimir; Mihajlov, A. A.

    2016-07-01

    The focus of this work is on the extraction of D-region electron density that is induced by the intensive X-ray flux under different solar zenith angle. The sensitivity of Very Low and Low Frequency (VLF and LF) propagation in the lower ionosphere makes it an ideal probe for remotely sensing the ambient state and localized perturbations of the ionosphere. The basis of this work is amplitude and phase data acquired by monitoring DHO/23.40 kHz and NSC/45.90 kHz radio signals during the period of ascending and maximum of the solar cycle 24. All the data were recorded at Belgrade station (44.85 ^{0} N, 20.38 ^{0} E) by AWESOME system. DHO-BEL and NSC-BEL are short paths with distances of 1300 and 953 km, respectively. These paths are in the same time zone. The diurnal amplitude and phase variations on VLF/LF radio signal against time vary in characteristic ways that are caused by solar zenith angles over path. Two amplitude minima are observed when sunrise and sunset terminators reach the middle of the propagation path. During daytime condition there are two amplitude minima (in morning and afternoon) developed under solar zenith angles χ ˜80 ^{0} over short path. In this study we considered amplitude and phase perturbations on VLF/LF radio signal induced by solar X-ray flares under solar zenith angles which are close with timings of amplitude minima during daytime under normal ionospheric condition. We expected and estimated differences in amplitude and phase perturbations on DHO/23.40 kHz and NSC/45.90 kHz radio signals induced by solar X-ray flares which occurrences are under solar zenith angles χ ≤ 80 ^{0}. The observations include solar flares with magnitudes in the range from C2 (I_{X} = 2 10^{-6} Wm^{-2} of X-ray flux in the band at 0.1 - 0.8 nm) to X2.1 (I_{X} = 2.1 10^{-4} Wm^{-2}) class. For example on 11 March 2015 occurred X2.1 class flare with maximum of intensity at 16:22 UT, when solar angle was χ = 81^{0} at Belgrade. One day before, under normal

  16. Fast radio bursts may originate from nearby flaring stars

    CERN Document Server

    Loeb, Abraham; Maoz, Dan

    2013-01-01

    Six cases of fast radio bursts (FRBs) have recently been discovered. The FRBs are bright (~0.1 - 1 Jy) and brief (~ 1 ms) pulses of radio emission with dispersion measures (DMs) that exceed Galactic values, and hence FRBs have been interpreted to be at cosmological distances. We propose, instead, that FRBs are rare eruptions of flaring main-sequence stars within ~1 kpc. Rather than associating their excess DM with the intergalactic medium, we relate it to a blanket of coronal plasma around their host stars. We have monitored at optical bands the stars within the radio beams of three of the known FRBs. In one field, we find a bright (V=13.6 mag) variable star (0.2 mag peak-to-trough) with a main-sequence G-type spectrum and a period P = 7.8 hr, likely a W-UMa-type contact binary. Analysis of our data outside of the FRB beams indicates a 5% chance probability of finding a variable star of this brightness and amplitude within the FRB beams. We find no unusual variable stars in the other two FRB fields. Further o...

  17. Probing Dynamics of Electron Acceleration with Radio and X-ray Spectroscopy, Imaging, and Timing in the 2002 Apr 11 Solar Flare

    CERN Document Server

    Fleishman, Gregory D; Nita, Gelu M; Gary, Dale E

    2013-01-01

    Based on detailed analysis of radio and X-ray observations of a flare on 2002 April 11 augmented by realistic 3D modeling, we have identified a radio emission component produced directly at the flare acceleration region. This acceleration region radio component has distinctly different (i) spectrum, (ii) light curves, (iii) spatial location, and, thus, (iv) physical parameters from those of the separately identified, trapped or precipitating electron components. To derive evolution of physical parameters of the radio sources we apply forward fitting of the radio spectrum time sequence with the gyrosynchrotron source function with 5 to 6 free parameters. At the stage when the contribution from the acceleration region dominates the radio spectrum, the X-ray- and radio- derived electron energy spectral indices agree well with each other. During this time the maximum energy of the accelerated electron spectrum displays a monotonic increase with time from ~ 300 keV to ~ 2 MeV over roughly one minute duration indic...

  18. A very small and super strong zebra pattern burst at the beginning of a solar flare

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Baolin; Tan, Chengming; Zhang, Yin; Huang, Jing; Yan, Yihua [Key Laboratory of Solar Activity, National Astronomical Observatories of Chinese Academy of Sciences, Beijing 100012 (China); Mészárosová, Hana; Karlický, Marian, E-mail: bltan@nao.cas.cn [Astronomical Institute of the Academy of Sciences of the Czech Republic, Ondřejov 15165 (Czech Republic)

    2014-08-01

    Microwave emission with spectral zebra pattern structures (ZPs) is frequently observed in solar flares and the Crab pulsar. The previous observations show that ZP is a structure only overlapped on the underlying broadband continuum with slight increments and decrements. This work reports an unusually strong ZP burst occurring at the beginning of a solar flare observed simultaneously by two radio telescopes located in China and the Czech Republic and by the EUV telescope on board NASA's satellite Solar Dynamics Observatory on 2013 April 11. It is a very short and super strong explosion whose intensity exceeds several times that of the underlying flaring broadband continuum emission, lasting for just 18 s. EUV images show that the flare starts from several small flare bursting points (FBPs). There is a sudden EUV flash with extra enhancement in one of these FBPs during the ZP burst. Analysis indicates that the ZP burst accompanying an EUV flash is an unusual explosion revealing a strong coherent process with rapid particle acceleration, violent energy release, and fast plasma heating simultaneously in a small region with a short duration just at the beginning of the flare.

  19. A very small and super strong zebra pattern burst at the beginning of a solar flare

    International Nuclear Information System (INIS)

    Microwave emission with spectral zebra pattern structures (ZPs) is frequently observed in solar flares and the Crab pulsar. The previous observations show that ZP is a structure only overlapped on the underlying broadband continuum with slight increments and decrements. This work reports an unusually strong ZP burst occurring at the beginning of a solar flare observed simultaneously by two radio telescopes located in China and the Czech Republic and by the EUV telescope on board NASA's satellite Solar Dynamics Observatory on 2013 April 11. It is a very short and super strong explosion whose intensity exceeds several times that of the underlying flaring broadband continuum emission, lasting for just 18 s. EUV images show that the flare starts from several small flare bursting points (FBPs). There is a sudden EUV flash with extra enhancement in one of these FBPs during the ZP burst. Analysis indicates that the ZP burst accompanying an EUV flash is an unusual explosion revealing a strong coherent process with rapid particle acceleration, violent energy release, and fast plasma heating simultaneously in a small region with a short duration just at the beginning of the flare

  20. STELLAR CORONAE, SOLAR FLARES: A DETAILED COMPARISON OF σ GEM, HR 1099, AND THE SUN IN HIGH-RESOLUTION X-RAYS

    International Nuclear Information System (INIS)

    The Chandra High Energy Transmission Grating Spectrometer (HETG) spectra of the coronally active binary stars σ Gem and HR 1099 are among the highest fluence observations for such systems taken at high spectral resolution in X-rays with this instrument. This allows us to compare their properties in detail to solar flare spectra obtained with the Russian CORONAS-F spacecraft's RESIK instrument at similar resolution in an overlapping bandpass. Here we emphasize the detailed comparisons of the 3.3-6.1 A region (including emission from highly ionized S, Si, Ar, and K) from solar flare spectra to the corresponding σ Gem and HR 1099 spectra. We also model the larger wavelength range of the HETG, from 1.7 to 25 A — having emission lines from Fe, Ca, Ar, Si, Al, Mg, Ne, O, and N—to determine coronal temperatures and abundances. σ Gem is a single-lined coronally active long-period binary which has a very hot corona. HR 1099 is a similar, but shorter period, double-lined system. With very deep HETG exposures we can even study emission from some of the weaker species, such as K, Na, and Al, which are important since they have the lowest first ionization potentials, a parameter well known to be correlated with elemental fractionation in the solar corona. The solar flare temperatures reach ≈20 MK, comparable to the σ Gem and HR 1099 coronae. During the Chandra exposures, σ Gem was slowly decaying from a flare and its spectrum is well characterized by a collisional ionization equilibrium plasma with a broad temperature distribution ranging from 2 to 60 MK, peaking near 25 MK, but with substantial emission from 50 MK plasma. We have detected K XVIII and Na XI emission which allow us to set limits on their abundances. HR 1099 was also quite variable in X-rays, also in a flare state, but had no detectable K XVIII. These measurements provide new comparisons of solar and stellar coronal abundances, especially at the lowest first ionization potential (FIP) values. The low

  1. Effect of burst and recombination models for Monte Carlo transport of interacting carriers in a-Se x-ray detectors on Swank noise

    International Nuclear Information System (INIS)

    Purpose: The authors describe the modification to a previously developed Monte Carlo model of semiconductor direct x-ray detector required for studying the effect of burst and recombination algorithms on detector performance. This work provides insight into the effect of different charge generation models for a-Se detectors on Swank noise and recombination fraction. Methods: The proposed burst and recombination models are implemented in the Monte Carlo simulation package, ARTEMIS, developed byFang et al. [“Spatiotemporal Monte Carlo transport methods in x-ray semiconductor detectors: Application to pulse-height spectroscopy in a-Se,” Med. Phys. 39(1), 308–319 (2012)]. The burst model generates a cloud of electron-hole pairs based on electron velocity, energy deposition, and material parameters distributed within a spherical uniform volume (SUV) or on a spherical surface area (SSA). A simple first-hit (FH) and a more detailed but computationally expensive nearest-neighbor (NN) recombination algorithms are also described and compared. Results: Simulated recombination fractions for a single electron-hole pair show good agreement with Onsager model for a wide range of electric field, thermalization distance, and temperature. The recombination fraction and Swank noise exhibit a dependence on the burst model for generation of many electron-hole pairs from a single x ray. The Swank noise decreased for the SSA compared to the SUV model at 4 V/μm, while the recombination fraction decreased for SSA compared to the SUV model at 30 V/μm. The NN and FH recombination results were comparable. Conclusions: Results obtained with the ARTEMIS Monte Carlo transport model incorporating drift and diffusion are validated with the Onsager model for a single electron-hole pair as a function of electric field, thermalization distance, and temperature. For x-ray interactions, the authors demonstrate that the choice of burst model can affect the simulation results for the generation

  2. Discovery of a Black Hole Mass-Period Correlation in Soft X-Ray Transients and Its Implication for Gamma-Ray Burst and Hypernova Mechanisms

    OpenAIRE

    Lee, C.H.; Brown, G. E.; Wijers, R.A.M.J.

    2002-01-01

    We investigate the soft X-ray transients with black hole primaries which may have been the sources of gamma-ray bursts and hypernovae earlier in their evolution. We find that the black-hole mass increases with the orbital period of the binary, both for systems with main-sequence donors and for those with evolved donors. This correlation can be understood in terms of angular-momentum support in the helium star progenitor of the black hole, if the systems with shorter periods had more rapidly r...

  3. Successive Merging of Plasmoids and Fragmentation in a Flare Current Sheet and Their X-Ray and Radio Signatures

    Czech Academy of Sciences Publication Activity Database

    Karlický, Marian; Bárta, M.

    2011-01-01

    Roč. 733, č. 2 (2011), 107/1-107/9. ISSN 0004-637X R&D Projects: GA AV ČR IAA300030701 Institutional research plan: CEZ:AV0Z10030501 Keywords : acceleration of particles * plasmas * solar flares Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 6.024, year: 2011

  4. Mass and radius determination for the neutron star in X-ray burst source 4U/MXB 1728-34

    CERN Document Server

    Majczyna, A

    2006-01-01

    We analyzed archival X-ray spectra of MXB 1728-34 obtained in 1996-99 by the Proportional Counter Array on board of the RXTE satellite. X-ray spectra were fitted to our extensive grids of model atmosphere spectra to determine the effective temperature T_eff on the neutron star surface, logarithm of surface gravity log(g), and the gravitational redshift z simultaneously. We have chosen fitting by numerical model spectra plus broad Gaussian line, modified by interstellar absorption and the absorption on dust. We arbitrarily assumed either hydrogen-helium chemical composition of a model atmosphere, or H-He-Fe mixture in solar proportion. The statistically best values of log(g), and z subsequently were used to determine mass and radius of the neutron star. We obtained the best values of the parameters for the neutron star in X-ray burst source MXB 1728-34: mass either M=0.40 or 0.63 M_sol (for H-He or H-He-Fe models, respectively), radius R=4.6 or 5.3 km, log(g)=14.6 or 14.6 and the gravitational redshift z=0.14 ...

  5. A Correlation Between the Intrinsic Brightness and Average Decay Rate of Gamma-ray Burst X-ray Afterglow Light Curves

    CERN Document Server

    Racusin, J L; de Pasquale, M; Kocevski, D

    2016-01-01

    We present a correlation between the average temporal decay ({\\alpha}X,avg,>200s) and early-time luminosity (LX,200s) of X-ray afterglows of gamma-ray bursts as observed by Swift-XRT. Both quantities are measured relative to a rest frame time of 200 s after the {\\gamma}-ray trigger. The luminosity average decay correlation does not depend on specific temporal behavior and contains one scale independent quantity minimizing the role of selection effects. This is a complementary correlation to that discovered by Oates et al. (2012) in the optical light curves observed by Swift-UVOT. The correlation indicates that on average, more luminous X-ray afterglows decay faster than less luminous ones, indicating some relative mechanism for energy dissipation. The X-ray and optical correlations are entirely consistent once corrections are applied and contamination is removed. We explore the possible biases introduced by different light curve morphologies and observational selection effects, and how either geometrical effe...

  6. A radio jet from the optical and x-ray bright stellar tidal disruption flare ASASSN-14li

    Science.gov (United States)

    van Velzen, S.; Anderson, G. E.; Stone, N. C.; Fraser, M.; Wevers, T.; Metzger, B. D.; Jonker, P. G.; van der Horst, A. J.; Staley, T. D.; Mendez, A. J.; Miller-Jones, J. C. A.; Hodgkin, S. T.; Campbell, H. C.; Fender, R. P.

    2016-01-01

    The tidal disruption of a star by a supermassive black hole leads to a short-lived thermal flare. Despite extensive searches, radio follow-up observations of known thermal stellar tidal disruption flares (TDFs) have not yet produced a conclusive detection. We present a detection of variable radio emission from a thermal TDF, which we interpret as originating from a newly launched jet. The multiwavelength properties of the source present a natural analogy with accretion-state changes of stellar mass black holes, which suggests that all TDFs could be accompanied by a jet. In the rest frame of the TDF, our radio observations are an order of magnitude more sensitive than nearly all previous upper limits, explaining how these jets, if common, could thus far have escaped detection.

  7. A radio jet from the optical and X-ray bright stellar tidal disruption flare ASASSN-14li

    CERN Document Server

    van Velzen, Sjoert; Stone, Nicholas C; Fraser, Morgan; Wevers, Thomas; Metzger, Brian D; Jonker, Peter G; van der Horst, Alexander J; Staley, Trim D; Mendez, Alexander J; Miller-Jones, James C A; Hodgkin, Simon T; Campbell, Heather C; Fender, Rob P

    2015-01-01

    The tidal disruption of a star by a supermassive black hole leads to a short-lived thermal flare. Despite extensive searches, radio follow-up observations of known thermal stellar tidal disruption flares (TDFs) have not yet produced a conclusive detection. We present a detection of variable radio emission from a thermal TDF, which we interpret as originating from a newly-launched jet. The multi-wavelength properties of the source present a natural analogy with accretion state changes of stellar mass black holes, suggesting all TDFs could be accompanied by a jet. In the rest frame of the TDF, our radio observations are an order of magnitude more sensitive than nearly all previous upper limits, explaining how these jets, if common, could thus far have escaped detection.

  8. A radio jet from the optical and x-ray bright stellar tidal disruption flare ASASSN-14li.

    Science.gov (United States)

    van Velzen, S; Anderson, G E; Stone, N C; Fraser, M; Wevers, T; Metzger, B D; Jonker, P G; van der Horst, A J; Staley, T D; Mendez, A J; Miller-Jones, J C A; Hodgkin, S T; Campbell, H C; Fender, R P

    2016-01-01

    The tidal disruption of a star by a supermassive black hole leads to a short-lived thermal flare. Despite extensive searches, radio follow-up observations of known thermal stellar tidal disruption flares (TDFs) have not yet produced a conclusive detection. We present a detection of variable radio emission from a thermal TDF, which we interpret as originating from a newly launched jet. The multiwavelength properties of the source present a natural analogy with accretion-state changes of stellar mass black holes, which suggests that all TDFs could be accompanied by a jet. In the rest frame of the TDF, our radio observations are an order of magnitude more sensitive than nearly all previous upper limits, explaining how these jets, if common, could thus far have escaped detection. PMID:26612833

  9. Case study of the mesospheric and lower thermospheric effects of solar X-ray flares: coupled ion-neutral modelling and comparison with EISCAT and riometer measurements

    Directory of Open Access Journals (Sweden)

    C.-F. Enell

    2008-08-01

    Full Text Available Two case studies of upper mesospheric and lower thermospheric (UMLT high-latitude effects of solar X-ray flares are presented. Sodankylä Ion-neutral Chemistry Model (SIC electron density profiles agree with D-region EISCAT and riometer observations, provided that the profiles of the most variable ionisable component, nitric oxide, are adjusted to compensate for NOx production during preceding geomagnetically active periods. For the M6-class flare of 27 April 2006, following a quiet period, the agreement with cosmic noise absorption observed by the Sodankylä riometers was within reasonable limits without adjustment of the [NO] profile. For the major (X17-class event of 28 October 2003, following high auroral activity and solar proton events, the NO concentration had to be increased up to on the order of 108 cm−3 at the D-region minimum. Thus [NO] can in principle be measured by combining SIC with observations, if the solar spectral irradiance and particle precipitation are adequately known.

    As the two case events were short and modelled for high latitudes, the resulting neutral chemical changes are insignificant. However, changes in the model ion chemistry occur, including enhancements of water cluster ions.

  10. On the features of bursts of neutrons, hard x-rays and alpha-particles in the pulse vacuum discharge with a virtual cathode and self-organization

    Science.gov (United States)

    Kurilenkov, Yu K.; Tarakanov, V. P.; Gus'kov, S. Yu; Samoylov, I. S.; Ostashev, V. E.

    2015-11-01

    In this paper, we continue the discussion of the experimental results on the yield of DD neutrons and hard x-rays in the nanosecond vacuum discharge (NVD) with a virtual cathode, which was started in the previous article of this issue, and previously (Kurilenkov Y K et al 2006 J. Phys. A: Math. Gen. 39 4375). We have considered here the regimes of very dense interelectrode aerosol ensembles, in which diffusion of even hard x-rays is found. The yield of DD neutrons in these regimes is conditioned not only by the head-on deuteron-deuteron collisions in the potential well of virtual cathode, but also by the channel of “deuteron-deuterium cluster” reaction, which exceeds overall yield of neutrons per a shot by more than an order of magnitude, bringing it up to ∼ 107/(4π). Very bright bursts of hard x-rays are also represented and discussed here. Presumably, their nature may be associated with the appearance in the NVD of some properties of random laser in the x-ray spectrum. Good preceding agreeing of the experiment on the DD fusion in the NVD with its particle-in-cell (PIC) simulations provides a basis to begin consideration of nuclear burning “proton-boron” in the NVD, which will be accompanied by the release of alpha particles only. With this objective in view, there has been started the PIC-simulation of aneutronic burning of p-B11, and its preliminary results are presented.

  11. Fluctuation analysis of solar radio bursts associated with geoeffective X-class flares

    Czech Academy of Sciences Publication Activity Database

    Veronese, T.B.; Rosa, R. R.; Bolzan, M.J.A.; Fernandes, F. C. R.; Sawant, H. S.; Karlický, Marian

    2011-01-01

    Roč. 73, 11-12 (2011), s. 1311-1316. ISSN 1364-6826 Institutional research plan: CEZ:AV0Z10030501 Keywords : decimetric solar radio bursts * solar flares * detrended fluctuation analysis Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 1.596, year: 2011

  12. Solar flare soft-X-ray spectra from Very Low Frequency observations of ionospheric modulations: Possibility of uninterrupted observation of non-thermal electron-plasma interaction in solar atmosphere.

    Science.gov (United States)

    Palit, Sourav; Chakrabarti, Sandip Kumar; Ray, Suman

    2016-07-01

    The hard and soft X-ray regions of a solar flare spectrum are the manifestation of interaction, namely of bremsstrahlung radiation of the non-thermal electrons moving inward in the denser part of the solar atmosphere with the plasma heated by those energetic electrons. The continuous and uninterrupted knowledge of X-ray photon spectra of flares are of great importance to derive information on the electron acceleration and hence time-evolution of energy transport and physics during solar flares. Satellite observations of solar X-ray spectrum are often limited by the restricted windows in each duty cycle to avoid the interaction of detectors and instruments with harmful energetic charge particles. In this work we have tried to tackle the problem by examining the possibility of using Earth's ionosphere and atmosphere as the detector of such transient events. Earth's lower ionosphere and upper atmosphere are the places where the X-rays and gamma-rays from such astronomical sources are absorbed. The electron-ion production rates due to the ionization of such energetic photons at different heights depend on the intensity and wavelength of the injected spectra and hence vary from one source to another. Obviously the electron and ion density vs. altitude profile has the imprint of the incident photon spectrum. As a preliminary exercise we developed a novel deconvolution method to extract the soft X-ray part of spectra of some solar flares of different classes from the electron density profiles obtained from Very Low Frequency (VLF) observation of lower ionosphere during those events. The method presented here is useful to carry out a similar exercise to infer the higher energy part of solar flare spectra and spectra of more energetic events such as the GRBs, SGRs etc. with the possibilities of probing even lower parts of the atmosphere.

  13. Early evolution of an X-ray emitting solar active region

    International Nuclear Information System (INIS)

    The birth and early evolution of a solar active region has been investigated using X-ray observations from the Lockheed Mapping X-Ray Heliometer on board the OSO-8 spacecraft. X-ray emission is observed within three hours of the first detection of Hα plage. At that time, a plasma temperature of 4 x 106 K in a region having a density of the order of 1010 cm-3 is inferred. During the fifty hours following birth almost continuous flares or flare-like X-ray bursts are superimposed on a monotonically increasing base level of X-ray emission produced by plasma with a temperature of the order 3 x 106 K. If it is assumed that the X-rays result from heating due to dissipation of current systems or magnetic field reconnection, it can be concluded that flare-like X-ray emission soon after active region birth implies that the magnetic field probably emerges in a stressed or complex configuration. (Auth.)

  14. SMALL-SCALE MICROWAVE BURSTS IN LONG-DURATION SOLAR FLARES

    International Nuclear Information System (INIS)

    Solar small-scale microwave bursts (SMBs), including microwave dot, spike, and narrow-band type III bursts, are characterized by very short timescales, narrow frequency bandwidth, and very high brightness temperatures. Based on observations of the Chinese Solar Broadband Radio Spectrometer at Huairou with superhigh cadence and frequency resolution, this work presents an intensive investigation of SMBs in several flares that occurred in active region NOAA 10720 during 2005 January 14-21. Especially for long-duration flares, the SMBs occurred not only in the early rising and impulsive phase, but also in the flare decay phase and even after the end of the flare. These SMBs are strong bursts with inferred brightness temperatures of at least 8.18 × 1011-1.92 × 1013 K, very short lifetimes of 5-18 ms, relative frequency bandwidths of 0.7%-3.5%, and superhigh frequency drifting rates. Together with their obviously different polarizations from background emission (the quiet Sun, and the underlying flaring broadband continuum), such SMBs should be individual, independent strong coherent bursts related to some non-thermal energy release and the production of energetic particles in a small-scale source region. These facts show the existence of small-scale strong non-thermal energy releasing activities after the flare maxima, which is meaningful for predicting space weather. Physical analysis indicates that a plasma mechanism may be the most favorable candidate for the formation of SMBs. From the plasma mechanism, the velocities and kinetic energy of fast electrons can be deduced and the region of electron acceleration can also be tracked

  15. Bone X-Ray (Radiography)

    Medline Plus

    Full Text Available ... clothing that might interfere with the x-ray images. Women should always inform their physician and x-ray ... small burst of radiation that passes through the body, recording an image on photographic film or a special detector. Different ...

  16. Bone X-Ray (Radiography)

    Medline Plus

    Full Text Available ... x-ray machine produces a small burst of radiation that passes through the body, recording an image on photographic film or a special detector. Different parts of the body absorb the x- ...

  17. Compact x-ray source based on burst-mode inverse Compton scattering at 100 kHz

    OpenAIRE

    Graves, W. S.; Bessuille, J.; Brown, P.; Carbajo, S.; Dolgashev, V.; Hong, K. -H.; Ihloff, E.; Khaykovich, B.; H. Lin; Murari, K.; Nanni, E. A.; RESTA, G.; Tantawi, S.; Zapata, L. E.; Kärtner, F. X.

    2014-01-01

    A design for a compact x-ray light source (CXLS) with flux and brilliance orders of magnitude beyond existing laboratory scale sources is presented. The source is based on inverse Compton scattering of a high brightness electron bunch on a picosecond laser pulse. The accelerator is a novel high-efficiency standing-wave linac and rf photoinjector powered by a single ultrastable rf transmitter at X-band rf frequency. The high efficiency permits operation at repetition rates up to 1 kHz, which i...

  18. Prompt Ultraviolet-to-Soft-X-Ray Emission of Gamma-Ray Bursts: Application to GRB 031203?

    OpenAIRE

    Li, Zhuo; Song, Li-Ming

    2004-01-01

    We discuss the prompt emission of GRBs, allowing for $\\gamma\\gamma$ pair production and synchrotron self-absorption. The observed hard spectra suggest heavy pair-loading in GRBs. The re-emission of the generated pairs results in the energy transmission from high-energy gamma-rays to long-wavelength radiation. Due to strong self-absorption, the synchrotron radiation by pairs is in optically thick regime, showing a thermal-like spectral bump in the extreme-ultraviolet/soft X-ray band, other tha...

  19. A Test of Thick-Target Nonuniform Ionization as an Explanation for Breaks in Solar Flare Hard X-Ray Spectra

    Science.gov (United States)

    Holman, gordon; Dennis Brian R.; Tolbert, Anne K.; Schwartz, Richard

    2010-01-01

    Solar nonthermal hard X-ray (HXR) flare spectra often cannot be fitted by a single power law, but rather require a downward break in the photon spectrum. A possible explanation for this spectral break is nonuniform ionization in the emission region. We have developed a computer code to calculate the photon spectrum from electrons with a power-law distribution injected into a thick-target in which the ionization decreases linearly from 100% to zero. We use the bremsstrahlung cross-section from Haug (1997), which closely approximates the full relativistic Bethe-Heitler cross-section, and compare photon spectra computed from this model with those obtained by Kontar, Brown and McArthur (2002), who used a step-function ionization model and the Kramers approximation to the cross-section. We find that for HXR spectra from a target with nonuniform ionization, the difference (Delta-gamma) between the power-law indexes above and below the break has an upper limit between approx.0.2 and 0.7 that depends on the power-law index delta of the injected electron distribution. A broken power-law spectrum with a. higher value of Delta-gamma cannot result from nonuniform ionization alone. The model is applied to spectra obtained around the peak times of 20 flares observed by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI from 2002 to 2004 to determine whether thick-target nonuniform ionization can explain the measured spectral breaks. A Monte Carlo method is used to determine the uncertainties of the best-fit parameters, especially on Delta-gamma. We find that 15 of the 20 flare spectra require a downward spectral break and that at least 6 of these could not be explained by nonuniform ionization alone because they had values of Delta-gamma with less than a 2.5% probability of being consistent with the computed upper limits from the model. The remaining 9 flare spectra, based on this criterion, are consistent with the nonuniform ionization model.

  20. INTEGRAL and XMM-Newton observations of the low-luminosity and X-ray-rich burst GRB 040223

    International Nuclear Information System (INIS)

    GRB 040223 was observed by INTEGRAL and XMM-Newton. GRB 040223 has a peak flux of (1.6±0.13) x 10-8 ergs cm-2 s-1, a fluence of (4.4±0.4) x 10-7 ergs cm-2 and a steep photon power law index of -2.3±0.2, in the energy range 20-200 keV. The steep spectrum implies it is an X-ray-rich GRB with emission up to 200 keV and Epeak peak is x = -1.7±0.2, a temporal decay of t-0.75±0.25 and a large column density of 1.8 x 1022 cm-2. The luminosity-lag relationship was used to obtain a redshift z 0.1-0.02+0.04. The isotropic energy radiated in γ-rays and X-ray luminosity after 10 hours are factors of 1000 and 100 less than classical GRBs. GRB 040223 is consistent with the extrapolation of the Amati relation into the region that includes XRF 030723 and XRF 020903

  1. HETE-2 Observations of the X-Ray Flash XRF 040916

    CERN Document Server

    Arimoto, M; Yoshida, A; Tamagawa, T; Shirasaki, Y; Suzuki, M; Matsuoka, M; Kotoku, J; Sato, R; Shimokawabe, T; Pazmino, N V; Ishimura, T; Nakagawa, Y; Ishikawa, N; Kobayashi, A; Sugita, S; Takahashi, I; Kuwahara, M; Yamauchi, M; Takagishi, K; Hatsukade, I; Atteia, J L; Pelangeon, A; Vanderspek, R; Graziani, C; Prigozhin, G Y; Villasenor, J; Jernigan, J G; Crew, G B; Hurley, K; Sakamoto, T; Ricker, G R; Woosley, S E; Butler, N; Levine, A; Doty, J P; Donaghy, T Q; Lamb, D Q; Fenimore, E E; Galassi, M; Boër, M; Dezalay, J P; Olive, J F; Braga, J; Manchanda, R; Pizzichini, G; Arimoto, Makoto; Kawai, Nobuyuki; Yoshida, Atsumasa; Tamagawa, Toru; Shirasaki, Yuji; Suzuki, Motoko; Matsuoka, Masaru; Kotoku, Jun'ichi; Sato, Rie; Shimokawabe, Takashi; Pazmino, Nicolas Vasquez; Ishimura, Takuto; Nakagawa, Yujin; Ishikawa, Nobuyuki; Kobayashi, Akina; Sugita, Satoshi; Takahashi, Ichiro; Kuwahara, Makoto; Yamauchi, Makoto; Takagishi, Kunio; Hatsukade, Isamu; Atteia, Jean-Luc; Pelangeon, Alexandre; Vanderspek, Roland; Graziani, Carlo; Prigozhin, Gregory; Villasenor, Joel; Crew, Geoffrey B.; Hurley, Kevin; Sakamoto, Takanori; Ricker, George R.; Woosley, Stanford E.; Butler, Nat; Levine, Al; Doty, John P.; Donaghy, Timothy Q.; Lamb, Donald Q.; Fenimore, Edward E.; Galassi, Mark; Boer, Michel; Dezalay, Jean-Pascal; Olive, Jean-Francios; Braga, Joao; Manchanda, Ravi; Pizzichini, Graziella

    2007-01-01

    A long X-ray flash was detected and localized by the instruments aboard the High Energy Transient Explorer II (HETE-2) at 00:03:30 UT on 2004 September 16. The position was reported to the GRB Coordinates Network (GCN) approximately 2 hours after the burst. This burst consists of two peaks separated by 200 s, with durations of 110 s and 60 s. We have analyzed the energy spectra of the 1st and 2nd peaks observed with the Wide Field X-Ray Monitor (WXM) and the French Gamma Telescope (FREGATE). We discuss the origin of the 2nd peak in terms of flux variabilities and timescales. We find that it is most likely part of the prompt emission, and is explained by the long-acting engine model. This feature is similar to some bright X-ray flares detected in the early afterglow phase of bursts observed by the Swift satellite.

  2. Multidimensional modeling of type I X-ray bursts. II. Two-dimensional convection in a mixed H/He accretor

    Energy Technology Data Exchange (ETDEWEB)

    Malone, C. M. [Department of Astronomy and Astrophysics, The University of California Santa Cruz, Santa Cruz, CA 95064 (United States); Zingale, M. [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States); Nonaka, A.; Almgren, A. S.; Bell, J. B., E-mail: malone@ucolick.org [Center for Computational Sciences and Engineering, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2014-06-20

    Type I X-ray bursts are thermonuclear explosions of accreted material on the surface of neutron stars in low-mass X-ray binaries. Prior to the ignition of a subsonic burning front, runaway burning at the base of the accreted layer drives convection that mixes fuel and heavy-element ashes. In this paper, the second in a series, we explore the behavior of this low Mach number convection in mixed hydrogen/helium layers on the surface of a neutron star using two-dimensional simulations with the Maestro code. Maestro takes advantage of the highly subsonic flow field by filtering dynamically unimportant sound waves while retaining local compressibility effects, such as those due to stratification and energy release from nuclear reactions. In these preliminary calculations, we find that the rp-process approximate network creates a convective region that is split into two layers. While this splitting appears artificial due to the approximations of the network regarding nuclear flow out of the breakout reaction {sup 18}Ne(α, p){sup 21}Na, these calculations hint at further simplifications and improvements of the burning treatment for use in subsequent calculations in three dimensions for a future paper.

  3. Multidimensional Modeling of Type I X-ray Bursts. II. Two-Dimensional Convection in a Mixed H/He Accretor

    CERN Document Server

    Malone, C M; Nonaka, A; Almgren, A S; Bell, J B

    2014-01-01

    Type I X-ray Bursts (XRBs) are thermonuclear explosions of accreted material on the surfaces of a neutron stars in low mass X-ray binaries. Prior to the ignition of a subsonic burning front, runaway burning at the base of the accreted layer drives convection that mixes fuel and heavy-element ashes. In this second paper in a series, we explore the behavior of this low Mach number convection in mixed hydrogen/helium layers on the surface of a neutron star using two-dimensional simulations with the Maestro code. Maestro takes advantage of the highly subsonic flow field by filtering dynamically unimportant sound waves while retaining local compressibility effects, such as those due to stratification and energy release from nuclear reactions. In these preliminary calculations, we find that the rp-process approximate network creates a convective region that is split into two layers. While this splitting appears artificial due to the approximations of the network regarding nuclear flow out of the breakout reaction 1...

  4. Systematic Uncertainties in the Spectroscopic Measurements of Neutron-Star Masses and Radii from Thermonuclear X-ray Bursts. III. Absolute Flux Calibration

    CERN Document Server

    Guver, Tolga; Marshall, Herman; Psaltis, Dimitrios; Guainazzi, Matteo; Diaz-Trigo, Maria

    2015-01-01

    Many techniques for measuring neutron star radii rely on absolute flux measurements in the X-rays. As a result, one of the fundamental uncertainties in these spectroscopic measurements arises from the absolute flux calibrations of the detectors being used. Using the stable X-ray burster, GS 1826-238, and its simultaneous observations by Chandra HETG/ACIS-S and RXTE/PCA as well as by XMM-Newton EPIC-pn and RXTE/PCA, we quantify the degree of uncertainty in the flux calibration by assessing the differences between the measured fluxes during bursts. We find that the RXTE/PCA and the Chandra gratings measurements agree with each other within their formal uncertainties, increasing our confidence in these flux measurements. In contrast, XMM-Newton EPIC-pn measures 14.0$\\pm$0.3% less flux than the RXTE/PCA. This is consistent with the previously reported discrepancy with the flux measurements of EPIC-pn, compared to EPIC-MOS1, MOS2 and ACIS-S detectors. We also address the calibration uncertainty in the RXTE/PCA int...

  5. NuSTAR Observation Of A Type I X-Ray Burst From GRS 1741.9-2853

    DEFF Research Database (Denmark)

    Barriere, Nicolas M.; Krivonos, Roman; Tomsick, John A.;

    2015-01-01

    s-1 in a second observation on 2013 August 3. A bright, 800 s long, H-triggered mixed H/He thermonuclear Type I burst with mild photospheric radius expansion (PRE) was present during the second observation. Assuming that the luminosity during the PRE was at the Eddington level, an H mass fraction X...

  6. Coasting External Shock in Wind Medium: An Origin for the X-Ray Plateau Decay Component in Swift Gamma-Ray Burst Afterglows

    Science.gov (United States)

    Shen, Rongfeng; Matzner, Christopher D.

    2012-01-01

    The plateaus observed in about one half of the early X-ray afterglows are the most puzzling feature in gamma-ray bursts (GRBs) detected by Swift. By analyzing the temporal and spectral indices of a large X-ray plateau sample, we find that 55% can be explained by external, forward shock synchrotron emission produced by a relativistic ejecta coasting in a ρvpropr -2, wind-like medium; no energy injection into the shock is needed. After the ejecta collects enough medium and transitions to the adiabatic, decelerating blast wave phase, it produces the post-plateau decay. For those bursts consistent with this model, we find an upper limit for the initial Lorentz factor of the ejecta, Γ0 <= 46(epsilon e /0.1)-0.24(epsilon B /0.01)0.17; the isotropic equivalent total ejecta energy is E iso ~ 1053(epsilon e /0.1)-1.3(epsilon B /0.01)-0.09(tb /104 s) erg, where epsilon e and epsilon B are the fractions of the total energy at the shock downstream that are carried by electrons and the magnetic field, respectively, and tb is the end of the plateau. Our finding supports Wolf-Rayet stars as the progenitor stars of some GRBs. It raises intriguing questions about the origin of an intermediate-Γ0 ejecta, which we speculate is connected to the GRB jet emergence from its host star. For the remaining 45% of the sample, the post-plateau decline is too rapid to be explained in the coasting-in-wind model, and energy injection appears to be required.

  7. COASTING EXTERNAL SHOCK IN WIND MEDIUM: AN ORIGIN FOR THE X-RAY PLATEAU DECAY COMPONENT IN SWIFT GAMMA-RAY BURST AFTERGLOWS

    International Nuclear Information System (INIS)

    The plateaus observed in about one half of the early X-ray afterglows are the most puzzling feature in gamma-ray bursts (GRBs) detected by Swift. By analyzing the temporal and spectral indices of a large X-ray plateau sample, we find that 55% can be explained by external, forward shock synchrotron emission produced by a relativistic ejecta coasting in a ρ∝r–2, wind-like medium; no energy injection into the shock is needed. After the ejecta collects enough medium and transitions to the adiabatic, decelerating blast wave phase, it produces the post-plateau decay. For those bursts consistent with this model, we find an upper limit for the initial Lorentz factor of the ejecta, Γ0 ≤ 46(εe/0.1)–0.24(εB/0.01)0.17; the isotropic equivalent total ejecta energy is Eiso ∼ 1053(εe/0.1)–1.3(εB/0.01)–0.09(tb /104 s) erg, where εe and εB are the fractions of the total energy at the shock downstream that are carried by electrons and the magnetic field, respectively, and tb is the end of the plateau. Our finding supports Wolf-Rayet stars as the progenitor stars of some GRBs. It raises intriguing questions about the origin of an intermediate-Γ0 ejecta, which we speculate is connected to the GRB jet emergence from its host star. For the remaining 45% of the sample, the post-plateau decline is too rapid to be explained in the coasting-in-wind model, and energy injection appears to be required.

  8. COASTING EXTERNAL SHOCK IN WIND MEDIUM: AN ORIGIN FOR THE X-RAY PLATEAU DECAY COMPONENT IN SWIFT GAMMA-RAY BURST AFTERGLOWS

    Energy Technology Data Exchange (ETDEWEB)

    Shen Rongfeng; Matzner, Christopher D., E-mail: rfshen@astro.utoronto.ca, E-mail: matzner@astro.utoronto.ca [Department of Astronomy and Astrophysics, University of Toronto, Ontario M5S 3H4 (Canada)

    2012-01-01

    The plateaus observed in about one half of the early X-ray afterglows are the most puzzling feature in gamma-ray bursts (GRBs) detected by Swift. By analyzing the temporal and spectral indices of a large X-ray plateau sample, we find that 55% can be explained by external, forward shock synchrotron emission produced by a relativistic ejecta coasting in a {rho}{proportional_to}r{sup -2}, wind-like medium; no energy injection into the shock is needed. After the ejecta collects enough medium and transitions to the adiabatic, decelerating blast wave phase, it produces the post-plateau decay. For those bursts consistent with this model, we find an upper limit for the initial Lorentz factor of the ejecta, {Gamma}{sub 0} {<=} 46({epsilon}{sub e}/0.1){sup -0.24}({epsilon}{sub B}/0.01){sup 0.17}; the isotropic equivalent total ejecta energy is E{sub iso} {approx} 10{sup 53}({epsilon}{sub e}/0.1){sup -1.3}({epsilon}{sub B}/0.01){sup -0.09}(t{sub b} /10{sup 4} s) erg, where {epsilon}{sub e} and {epsilon}{sub B} are the fractions of the total energy at the shock downstream that are carried by electrons and the magnetic field, respectively, and t{sub b} is the end of the plateau. Our finding supports Wolf-Rayet stars as the progenitor stars of some GRBs. It raises intriguing questions about the origin of an intermediate-{Gamma}{sub 0} ejecta, which we speculate is connected to the GRB jet emergence from its host star. For the remaining 45% of the sample, the post-plateau decline is too rapid to be explained in the coasting-in-wind model, and energy injection appears to be required.

  9. Diagnostics of electron beam properties from the simultaneous hard X-ray and microwave emission in the 10 March 2001 flare

    CERN Document Server

    Zharkova, V V; Kashapova, L K; Kuznetsov, A A; Altyntsev, A T

    2011-01-01

    Simultaneous simulation of HXR and MW emission with the same populations of electrons is still a great challenge for interpretation of observations in real events. In this paper we apply the FP kinetic model of precipitation of electron beam with energy range from 12 keV to 1.2 MeV to the interpretation of X-ray and microwave emissions observed in the flare of 10 March 2001. Methods. The theoretical HXR and MW emissions were calculated by using the distribution functions of electron beams found by solving time-dependent Fokker-Planck approach in a converging magnetic field (Zharkova at al., 2010; Kuznetsov and Zharkova, 2010) for anisotropic scattering of beam electrons on the ambient particles in Coloumb collisions and Ohmic losses. The simultaneous observed HXR photon spectra and frequency distribution of MW emission and polarization were fit by those simulated from FP models which include the effects of electric field induced by beam electrons and precipitation into a converging magnetic loop. Magnetic fie...

  10. Narrowband Gyrosynchrotron Bursts: Probing Electron Acceleration in Solar Flares

    CERN Document Server

    Fleishman, Gregory D; Kontar, Eduard P; Gary, Dale E

    2016-01-01

    Recently, in a few case studies we demonstrated that gyrosynchrotron microwave emission can be detected directly from the acceleration region when the trapped electron component is insignificant. For the statistical study reported here, we have identified events with steep (narrowband) microwave spectra that do not show a significant trapped component and at the same time show evidence of source uniformity, which simplifies the data analysis greatly. Initially, we identified a subset of more than 20 radio bursts with such narrow spectra, having low- and high-frequency spectral indices larger than 3 in absolute value. A steep low-frequency spectrum implies that the emission is nonthermal (for optically-thick thermal emission, the spectral index cannot be steeper than 2), and the source is reasonably dense and uniform. A steep high-frequency spectrum implies that no significant electron trapping occurs; otherwise a progressive spectral flattening would be observed. Roughly half of these radio bursts have RHESSI...

  11. A Multi-Wavelength Study of Sgr A*: The Role of Near-IR Flares in Production of X-ray, Soft $\\gamma$-ray and Sub-millimeter Emission

    CERN Document Server

    Yusef-Zadeh, F; Wardle, M; Roberts, D; Heinke, C; Bower, G C; Vilaro, B V; Shapiro, S; Goldwurm, A; Bélanger, G

    2005-01-01

    Although Sgr A* is known to be variable in radio, millimeter, near-IR and X-rays, the correlation of the variability across its spectrum has not been fully studied. Here we describe highlights of the results of two observing campaigns in 2004 to investigate the correlation of flare activity in different wavelength regimes, using a total of nine ground and space-based telescopes. We report the detection of several new near-IR flares during the campaign based on {\\it HST} observations. The level of near-IR flare activity based on {\\it HST} data can be as low as $\\sim0.15$ mJy at 1.6 $\\mu$m and continuous up to $\\sim$40% of the total observing time, thus placing better limits than ground-based near-IR observations. We also show the detection of a simultaneous bright X-ray and near-IR flare in which we observe for the first time correlated substructures as well as a submillimeter and near-IR flare using the NICMOS instrument on the {\\it HST}, the {\\it XMM-Newton} and {\\it Caltech Submillimeter} observatories. X-r...

  12. Observation of solar high energy gamma and X-ray emission and solar energetic particles

    CERN Document Server

    Struminsky, Alexei

    2015-01-01

    We considered 18 solar flares observed between June 2010 and July 2012, in which high energy >100 MeV {\\gamma}-emission was registered by the Large Area Telescope (LAT) aboard FermiGRO. We examined for these {\\gamma}-events soft X-ray observations by GOES, hard X-ray observations by the Anti-Coincidence Shield of the SPectrometer aboard INTEGRAL (ACS SPI) and the Gamma-Ray burst Monitor (GBM) aboard FermiGRO. Hard X-ray and {\\pi}0-decay {\\gamma}-ray emissions are used as tracers of electron and proton acceleration, respectively. Bursts of hard X-ray were observed by ACS SPI during impulsive phase of 13 events. Bursts of hard X-ray >100 keV were not found during time intervals, when prolonged hard {\\gamma}-emission was registered by LAT/FermiGRO. Those events showing prolonged high-energy gamma-ray emission not accompanied by >100 keV hard X-ray emission are interpreted as an indication of either different acceleration processes for protons and electrons or as the presence of a proton population accelerated du...

  13. Observational Signatures of High-Energy Emission during the Shallow Decay Phase of Gamma-Ray Burst X-Ray Afterglows

    Science.gov (United States)

    Yu, Y. W.; Liu, X. W.; Dai, Z. G.

    2007-12-01

    The widely existing shallow decay phase of the X-ray afterglows of gamma-ray bursts (GRBs) is generally accepted to be due to long-lasting energy injection. The outflows carrying the injecting energy, based on the component that is dominant in energy, fall into two possible types: baryon-dominated and lepton-dominated ones. The former type of outflow could be ejecta that is ejected during the prompt phase of a GRB and consists of a series of baryonic shells with a distribution of Lorentz factors, and the latter type could be an electron-positron pair wind that is driven by the postburst central engine. We here provide a unified description for the dynamics of fireballs based on these two types of energy injection and calculate the corresponding high-energy photon emission by considering synchrotron radiation and inverse Compton scattering (including synchrotron self-Compton and combined inverse Compton) of electrons. We find that, in the two energy-injection models, there is a plateau (even a hump) in high-energy light curves during the X-ray shallow decay phase. In particular, a considerable fraction of the injecting energy in the lepton-dominated model can be shared by the long-lasting reverse shock since it is relativistic. Furthermore, almost all of the energy of the reverse shock is carried by leptons, and thus, the inverse Compton emission is enhanced dramatically. Therefore, this model predicts more significant high-energy afterglow emission than the baryon-dominated model. We argue that these observational signatures would be used to discriminate between different energy-injection models in the upcoming Gamma-Ray Large Area Space Telescope (GLAST) era.

  14. THE LACK OF DIFFUSE, NON-THERMAL HARD X-RAY EMISSION IN THE COMA CLUSTER: THE SWIFT BURST ALERT TELESCOPE'S EYE VIEW

    International Nuclear Information System (INIS)

    The Coma Cluster of galaxies hosts the brightest radio halo known and has therefore been the target of numerous searches for associated inverse Compton (IC) emission, particularly at hard X-ray energies where the IC signal must eventually dominate over thermal emission. The most recent search with the Suzaku Hard X-ray Detector failed to confirm previous IC detections with RXTE and BeppoSAX, instead setting an upper limit 2.5 times below their non-thermal flux. However, this discrepancy can be resolved if the IC emission is very extended, beyond the scale of the cluster radio halo. Using reconstructed sky images from the 58-month Swift Burst Alert Telescope (BAT) all-sky survey, the feasibility of such a solution is investigated. Building on Renaud et al., we test and implement a method for extracting the fluxes of extended sources, assuming specified spatial distributions. BAT spectra are jointly fit with an XMM-Newton EPIC-pn spectrum derived from mosaic observations. We find no evidence for large-scale IC emission at the level expected from the previously detected non-thermal fluxes. For all non-thermal spatial distributions considered, which span the gamut of physically reasonable IC models, we determine upper limits for which the largest (most conservative) limit is ∼-12 erg s-1 cm-2 (20-80 keV), which corresponds to a lower limit on the magnetic field B > 0.2 μ G. A nominal flux upper limit of -12 erg s-1 cm-2, with corresponding B > 0.25 μ G, is derived for the most probable IC distribution given the size of the radio halo and likely magnetic field radial profile.

  15. Soft X-ray extended emissions of short gamma-ray bursts as electromagnetic counterparts of compact binary mergers: possible origin and detectability

    International Nuclear Information System (INIS)

    We investigate the possible origin of extended emissions (EEs) of short gamma-ray bursts with an isotropic energy of ∼1050-51 erg and a duration of a few 10 s to ∼100 s, based on a compact binary (neutron star (NS)-NS or NS-black hole (BH)) merger scenario. We analyze the evolution of magnetized neutrino-dominated accretion disks of mass ∼0.1 M ☉ around BHs formed after the mergers and estimate the power of relativistic outflows via the Blandford-Znajek (BZ) process. We show that a rotation energy of the BH up to ≳ 1052 erg can be extracted with an observed timescale of ≳ 30(1 + z) s with a relatively small disk viscosity parameter of α < 0.01. Such a BZ power dissipates by clashing with non-relativistic pre-ejected matter of mass M ∼ 10–(2-4) M ☉, and forms a mildly relativistic fireball. We show that the dissipative photospheric emissions from such fireballs are likely in the soft X-ray band (1-10 keV) for M ∼ 10–2 M ☉, possibly in NS-NS mergers, and in the BAT band (15-150 keV) for M ∼ 10–4 M ☉, possibly in NS-BH mergers. In the former case, such soft EEs can provide a good chance of ∼6 yr−1 (ΔΩsoftEE/4π) (RGW/40 yr−1) for simultaneous detections of the gravitational waves with a ∼0.°1 angular resolution by soft X-ray survey facilities like the Wide-Field MAXI. Here, ΔΩsoftEE is the beaming factor of the soft EEs and RGW is the NS-NS merger rate detectable by the advanced LIGO, the advanced Virgo, and KAGRA.

  16. Interpretation of rapid rises in hard x rays and microwaves with the thermal conduction front model

    International Nuclear Information System (INIS)

    Impulsive hard x ray and microwave bursts with rise times from 0.1 to 10 seconds are discussed. Source areas calculated by the method of Crannell, et al., (1978) were compared with source areas determined from Hinotori and the Hard x ray Imaging Spectrometer (HXIS) images. The agreement strongly suggests that the method is valid. If the thermal conduction front model for the hard x ray and microwave source is adopted, then the method enables derivation of area, density, magnetic field, and rise time from hard x ray and microwave spectral observations. This approach was used to derive these parameters for several rapid impulsive rises in the flares of July 1, 1980, and May 21, 1984. It is shown that the model provides a consistent interpretation of the observations of these impulsive increases. Indeed, the model provides a way to calculate rise times from spectra alone (to within a factor of about three) over more than two orders of magnitude

  17. Remote planetary geochemical exploration with the NEAR X-ray/gamma-ray spectrometer

    International Nuclear Information System (INIS)

    The X-ray/gamma-ray spectrometer (XGRS) instrument onboard the Near Earth Asteroid Rendezvous (NEAR) spacecraft will map asteroid 433 Eros in the 0.2 keV to 10 MeV energy region. Measurements of the discrete line X-ray and gamma-ray emissions in this energy domain can be used to obtain both qualitative and quantitative elemental composition maps of the asteroid surface. The NEAR X-ray/gamma-ray spectrometer (XGRS) was turned on for the first time during the week of 7 April 1996. Rendezvous with Eros 433 is expected during December 1998. Observations of solar X-ray spectra during both quiescent and active periods have been made. A gamma-ray transient detection system has been implemented and about three gamma-ray transient events a week have been observed which are associated with either gamma-ray bursts or solar flares

  18. Shallow Decay of X-ray Afterglows in Short GRBs: Energy Injection from a Millisecond Magnetar?

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    With the successful launch of Swift satellite, more and more data of early X-ray afterglows from short gamma-ray bursts have been collected. Some interesting features such as unusual afterglow light curves and unexpected X-ray flares are revealed. Especially, in some cases, there is a flat segment in the X-ray afterglow light curve. Here we present a simplified model in which we believe that the flattening part is due to energy injection from the central engine. We assume that this energy injection arises from the magnetic dipole radiation of a millisecond pulsar formed after the merger of two neutron stars. We check this model with the short GRB 060313. Our numerical results suggest that energy injection from a millisecond magnetar could make part of the X-ray afterglow light curve flat.

  19. Magnetic Reconnection of Solar Flare Detected by Solar Radio Burst Type III

    International Nuclear Information System (INIS)

    The Sun is an ideal object of a blackbody with a large and complex magnetic field. In solar activity specifically solar flare phenomenon, the magnetic reconnection is one of the most significant factors of the Sun that can simplify a better understanding of our nearest star. This factor is due to the motion of the plasma and other particles through the convection mechanism inside the Sun. In our work, we will highlight one of the solar burst events that associated with solar flares. This event occurred on 13th November 2012 from 2:00:03 UT till 2:00:06 UT. It peaked with M2.0 solar flare at 2.04 UT. Within short time intervals of about l02 ∼ 103s, large quantities of energy of 1022 ∼ 1026J are emancipated. The changing magnetic field converts magnetic potential energy into kinetic energy by accelerating plasmas in the solar corona. It is believed that the plasma is channelled by the magnetic field up and away from the Sun. It is also accelerated back down along the magnetic field into the chromosphere. In conclusion, we showed that the structure of the solar radio burst type III is an indicator of a starting point of magnetic reconnection

  20. The unusual X-ray light-curve of GRB 080307: the onset of the afterglow?

    CERN Document Server

    Page, K L; O'Brien, P T; Tanvir, N R; Osborne, J P; Zhang, B; Holland, S T; Levan, A J; Melandri, A; Starling, R L C; Bersier, D; Burrows, D N; Geach, J E; Maxted, P

    2009-01-01

    Swift-detected GRB 080307 showed an unusual smooth rise in its X-ray light-curve around 100 seconds after the burst, at the start of which the emission briefly softened. This `hump' has a longer duration than is normal for a flare at early times and does not demonstrate a typical flare profile. Using a two component power-law-to-exponential model, the rising emission can be modelled as the onset of the afterglow, something which is very rarely seen in Swift-X-ray light-curves. We cannot, however, rule out that the hump is a particularly slow early-time flare, or that it is caused by upscattered reverse shock electrons.