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Sample records for cepheid pulsational quantities

  1. THE PULSATION MODE OF THE CEPHEID POLARIS

    Energy Technology Data Exchange (ETDEWEB)

    Turner, D. G. [Department of Astronomy and Physics, Saint Mary' s University, Halifax NS B3H 3C3 (Canada); Kovtyukh, V. V.; Usenko, I. A. [Astronomical Observatory, Odessa National University, and Isaac Newton Institute of Chile, Odessa Branch, T. G. Shevkenko Park, 65014 Odessa (Ukraine); Gorlova, N. I., E-mail: turner@ap.smu.ca [Institute of Astronomy, Celestijnenlaan 200D, B-3001 Leuven (Belgium)

    2013-01-01

    A previously derived photometric parallax of 10.10 {+-} 0.20 mas, d = 99 {+-} 2 pc, is confirmed for Polaris by a spectroscopic parallax derived using line ratios in high dispersion spectra for the Cepheid. The resulting estimates for the mean luminosity of (M{sub V} ) = -3.07 {+-} 0.01 s.e., average effective temperature of (T{sub eff}) = 6025 {+-} 1 K s.e., and intrinsic color of ((B) - (V)){sub 0} = +0.56 {+-} 0.01 s.e., which match values obtained previously from the photometric parallax for a space reddening of E{sub B-V} = 0.02 {+-} 0.01, are consistent with fundamental mode pulsation for Polaris and a first crossing of the instability strip, as also argued by its rapid rate of period increase. The systematically smaller Hipparcos parallax for Polaris appears discrepant by comparison.

  2. The Pulsation Mode of the Cepheid Polaris

    CERN Document Server

    Turner, David G; Usenko, Igor; Gorlova, N

    2012-01-01

    A previously-derived photometric parallax of 10.10+-0.20 mas, d=99+-2 pc, is confirmed for Polaris by a spectroscopic parallax derived using line ratios in high dispersion spectra for the Cepheid. The resulting estimates for the mean luminosity of =-3.07+-0.01 s.e., average effective temperature of =6025+-1 K s.e., and intrinsic color of (-)o=0.56+-0.01 s.e., which match values obtained previously from the photometric parallax for a space reddening of E(B-V)=0.02+-0.01, are consistent with fundamental mode pulsation for Polaris and a first crossing of the instability strip, as also argued by its rapid rate of period increase. The systematically smaller Hipparcos parallax for Polaris appears discrepant by comparison.

  3. THE PULSATION MODE AND DISTANCE OF THE CEPHEID FF AQUILAE

    Energy Technology Data Exchange (ETDEWEB)

    Turner, D. G. [Department of Astronomy and Physics, Saint Mary' s University, Halifax, NS B3H 3C3 (Canada); Kovtyukh, V. V. [Astronomical Observatory, Odessa National University, and Isaac Newton Institute of Chile, Odessa Branch, T. G. Shevkenko Park, 65014 Odessa (Ukraine); Luck, R. E. [Department of Astronomy, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-7215 (United States); Berdnikov, L. N., E-mail: turner@ap.smu.ca, E-mail: val@deneb1.odessa.ua, E-mail: rel2@case.edu, E-mail: leonid.berdnikov@gmail.com [Sternberg Astronomical Institute, Moscow M. V. Lomonosov State University, Moscow 119992 (Russian Federation)

    2013-07-20

    The determination of pulsation mode and distance for field Cepheids is a complicated problem best resolved by a luminosity estimate. For illustration a technique based on spectroscopic luminosity discrimination is applied to the 4.47 day s-Cepheid FF Aql. Line ratios in high dispersion spectra of the variable yield values of (M{sub V} ) = -3.40 {+-} 0.02 s.e. ({+-}0.04 s.d.), average effective temperature T{sub eff} = 6195 {+-} 24 K, and intrinsic color ((B) - (V)){sub 0} = +0.506 {+-} 0.007, corresponding to a reddening of E{sub B-V} = 0.25 {+-} 0.01, or E{sub B-V}(B0) = 0.26 {+-} 0.01. The skewed light curve, intrinsic color, and luminosity of FF Aql are consistent with fundamental mode pulsation for a small-amplitude classical Cepheid on the blue side of the instability strip, not a sinusoidal pulsator. A distance of 413 {+-} 14 pc is estimated from the Cepheid's angular diameter in conjunction with a mean radius of (R) = 39.0 {+-} 0.7 R{sub Sun} inferred from its luminosity and effective temperature. The dust extinction toward FF Aql is described by a ratio of total-to-selective extinction of R{sub V} = A{sub V} /E(B - V) = 3.16 {+-} 0.34 according to the star's apparent distance modulus.

  4. THE PULSATION MODE AND DISTANCE OF THE CEPHEID FF AQUILAE

    International Nuclear Information System (INIS)

    The determination of pulsation mode and distance for field Cepheids is a complicated problem best resolved by a luminosity estimate. For illustration a technique based on spectroscopic luminosity discrimination is applied to the 4.47 day s-Cepheid FF Aql. Line ratios in high dispersion spectra of the variable yield values of (MV ) = –3.40 ± 0.02 s.e. (±0.04 s.d.), average effective temperature Teff = 6195 ± 24 K, and intrinsic color ((B) – (V))0 = +0.506 ± 0.007, corresponding to a reddening of EB–V = 0.25 ± 0.01, or EB–V(B0) = 0.26 ± 0.01. The skewed light curve, intrinsic color, and luminosity of FF Aql are consistent with fundamental mode pulsation for a small-amplitude classical Cepheid on the blue side of the instability strip, not a sinusoidal pulsator. A distance of 413 ± 14 pc is estimated from the Cepheid's angular diameter in conjunction with a mean radius of (R) = 39.0 ± 0.7 R☉ inferred from its luminosity and effective temperature. The dust extinction toward FF Aql is described by a ratio of total-to-selective extinction of RV = AV /E(B – V) = 3.16 ± 0.34 according to the star's apparent distance modulus

  5. Theoretical rates of pulsation period change in the Galactic Cepheids

    CERN Document Server

    Fadeyev, Yuri A

    2014-01-01

    Theoretical estimates of the rates of radial pulsation period change in Galactic Cepheids with initial masses 5.5M_\\odot <= Mzams <= 13M_\\odot, chemical composition X=0.7, Z=0.02 and periods 1.5 day <= P <= 100 day are obtained from consistent stellar evolution and nonlinear stellar pulsation computations. Pulsational instability was investigated for three crossings of the instability strip by the evolutionary track in the HR diagram. The first crossing occurs at the post-main sequence helium core gravitational contraction stage which proceeds in the Kelvin--Helmholtz timescale whereas the second and the third crossings take place at the evolutionary stage of thermonuclear core helium burning. During each crossing of the instability strip the period of radial pulsations is a quadratic function of the stellar evolution time. Theoretical rates of the pulsation period change agree with observations but the scatter of observational estimates of dP/dt noticeably exceeds the width of the band (\\delta\\lo...

  6. Classical Cepheid pulsation models --- VI. The Hertzsprung progression

    Science.gov (United States)

    Bono, G.; Marconi, M.; Stellingwerf, R. F.

    2000-08-01

    We present the results of an extensive theoretical investigation on the pulsation behavior of Bump Cepheids. We constructed several sequences of full amplitude, nonlinear, convective models by adopting a chemical composition typical of Large Magellanic Cloud (LMC) Cepheids (Y=0.25, Z=0.008) and stellar masses ranging from M/M⊙ =6.55 to 7.45. We find that theoretical light and velocity curves reproduce the HP, and indeed close to the blue edge the bump is located along the descending branch, toward longer periods it crosses at first the luminosity/velocity maximum and then it appears along the rising branch. In particular, we find that the predicted period at the HP center is PHP = 11.24∓0.46 d and that such a value is in very good agreement with the empirical value estimated by adopting the Fourier parameters of LMC Cepheid light curves i.e. PHP = 11.2 ∓ 0.8 d (Welch et al. 1997). Moreover, light and velocity amplitudes present a "double-peaked" distribution which is in good qualitative agreement with observational evidence on Bump Cepheids. It turns out that both the skewness and the acuteness typically show a well-defined minimum at the HP center and the periods range from PHP = 10.73 ∓ 0.97 d to PHP = 11.29 ∓ 0.53 d which are in good agreement with empirical estimates. We also find that the models at the HP center are located within the resonance region but not on the 2:1 resonance line (P2/P0 = 0.5), and indeed the P2/P0 ratios roughly range from 0.51 (cool models) to 0.52 (hot models). Interestingly enough, the predicted Bump Cepheid masses, based on a Mass-Luminosity (ML) relation which neglects the convective core overshooting, are in good agreement with the empirical masses of Galactic Cepheids estimated by adopting the Baade-Wesselink method (Gieren 1989). As a matter of fact, the observed mass at the HP center -P ≍ 11.2 d- is 6.9 ∓ 0.9 M⊙, while the predicted mass is 7.0 ∓ 0.45 M⊙. Even by accounting for the metallicity difference

  7. Pulsation Period Change & Classical Cepheids: Probing the Details of Stellar Evolution

    CERN Document Server

    Neilson, Hilding R; Guinan, Ed; Engle, Scott

    2014-01-01

    Measurements of secular period change probe real-time stellar evolution of classical Cepheids making these measurements powerful constraints for stellar evolution models, especially when coupled with interferometric measurements. In this work, we present stellar evolution models and measured rates of period change for two Galactic Cepheids: Polaris and l Carinae, both important Cepheids for anchoring the Cepheid Leavitt law (period-luminosity relation). The combination of previously-measured parallaxes, interferometric angular diameters and rates of period change allows for predictions of Cepheid mass loss and stellar mass. Using the stellar evolution models, We find that l Car has a mass of about 9 $M_\\odot$ consistent with stellar pulsation models, but is not undergoing enhanced stellar mass loss. Conversely, the rate of period change for Polaris requires including enhanced mass-loss rates. We discuss what these different results imply for Cepheid evolution and the mass-loss mechanism on the Cepheid instabi...

  8. The development of early pulsation theory, or, how Cepheids are like steam engines"

    Science.gov (United States)

    Stanley, Matthew

    2011-05-01

    The pulsation theory of Cepheid variable stars was a major breakthrough of early twentieth-century astrophysics. At the beginning of that century, the basic physics of normal stars was very poorly understood, and variable stars were even more mysterious. Breaking with accepted explanations in terms of eclipsing binaries, Harlow Shapley and A.S. Eddington pioneered novel theories that considered Cepheids as pulsating spheres of gas. These theoretical models relied on highly speculative physics, but nonetheless returned very impressive results despite attacks from figures such as James Jeans. Surprisingly, the pulsation theory not only depended on developments in stellar physics, but also drove many of those developments. In particular, models of stars in radiative balance and theories of stellar energy were heavily inspired and shaped by ideas about variable stars. Further, the success of the pulsation theory helped justify the new approaches to astrophysics being developed before World War II.

  9. The Development of Early Pulsation Theory, or, How Cepheids Are Like Steam Engines

    Science.gov (United States)

    Stanley, M.

    2012-06-01

    The pulsation theory of Cepheid variable stars was a major breakthrough of early twentieth-century astrophysics. At the beginning of that century, the basic physics of normal stars was very poorly understood, and variable stars were even more mysterious. Breaking with accepted explanations in terms of eclipsing binaries, Harlow Shapley and A. S. Eddington pioneered novel theories that considered Cepheids as pulsating spheres of gas. Surprisingly, the pulsation theory not only depended on novel developments in stellar physics, but the theory also drove many of those developments. In particular, models of stars in radiative balance and theories of stellar energy were heavily inspired and shaped by ideas about variable stars. Further, the success of the pulsation theory helped justify the new approaches to astrophysics being developed before World War II.

  10. EROS differential studies of Cepheids in the Magellanic Clouds : Stellar pulsation, stellar evolution and distance scale

    NARCIS (Netherlands)

    Beaulieu, J. P.; Sasselov, D. D.

    1996-01-01

    Abstract: We present a differential study of 500 Magellanic Cepheids with 3 million measurements obtained as a by-product of the EROS microlensing survey. The data-set is unbiased and provides an excellent basis for a differential analysis between LMC and SMC. We investigate the pulsational properti

  11. Cepheids at high angular resolution: circumstellar envelope and pulsation

    Science.gov (United States)

    Gallenne, Alexandre

    2011-12-01

    In 2005, interferometric observations with VLTI/VINCI and CHARA/FLUOR revealed the existence of a circumstellar envelope (CSE) around some Cepheids. This surrounding material is particularly interesting for two reasons: it could have an impact on the distance estimates and could be linked to a past or on-going mass loss. The use of Baade-Wesselink methods for independent distance determinations could be significantly biased by the presence of these envelopes. Although their observations are difficult because of the high contrast between the photosphere of the star and the CSE, several observation techniques have the potential to improve our knowledge about their physical properties. In this thesis, I discuss in particular high angular resolution techniques that I applied to the study of several bright Galactic Cepheids. First, I used adaptive optic observations with NACO of the Cepheid RS Puppis, in order to deduce the flux ratio between the CSE and the photosphere of the star. In addition, I could carry out a statistical study of the speckle noise and inspect a possible asymmetry. Secondly, I analysed VISIR data to study the spectral energy distribution of a sample of Cepheids. These diffraction-limited images enabled me to carry out an accurate photometry in the N band and to detect an IR excess linked to the presence of a circumstellar component. On the other hand, applying a Fourier analysis I showed that some components are resolved. I then explored the K' band with the recombination instrument FLUOR for some bright Cepheids. Thanks to new set of data of Y Oph, I improved the study of its circumstellar envelope, using a ring-like model for the CSE. For two other Cepheids, U Vul and S Sge, I applied the interferometric Baade-Wesselink method in order to estimate their distance.

  12. On the pulsation mode identification of short-period Galactic Cepheids

    CERN Document Server

    Bono, G; Marconi, M; Fouqué, P

    2001-01-01

    We present new theoretical Period-Radius (PR) relations for first overtone Galactic Cepheids. Current predictions are based on several sequences of nonlinear, convective pulsation models at solar chemical composition (Y=0.28, Z=0.02) and stellar masses ranging from 3.0 to 5.5 Mo. The comparison between predicted and empirical radii of four short-period Galactic Cepheids suggests that QZ Nor and EV Sct are pulsating in the fundamental mode, whereas Polaris and SZ Tau pulsate in the first overtone. This finding supports the mode identifications that rely on the comparison between direct and Period-Luminosity (PL) based distance determinations but it is somewhat at variance with the mode identification based on Fourier parameters. In fact, we find from our models that fundamental and first overtone pulsators attain, for periods ranging from 2.7 to 4 d, quite similar phi_21 values, making mode discrimination from this parameter difficult. The present mode identifications for our sample of Cepheids are strengthene...

  13. Cepheids at high angular resolution: circumstellar envelope and pulsation

    CERN Document Server

    Gallenne, Alexandre

    2011-01-01

    In 2005, interferometric observations with VLTI/VINCI and CHARA/FLUOR revealed the existence of a circumstellar envelope (CSE) around some Cepheids. This surrounding material is particularly interesting for two reasons: it could have an impact on the distance estimates and could be linked to a past or on-going mass loss. The use of Baade-Wesselink methods for independent distance determinations could be significantly biased by the presence of these envelopes. Although their observations are difficult because of the high contrast between the photosphere of the star and the CSE, several observation techniques have the potential to improve our knowledge about their physical properties. In this thesis, I discuss in particular high angular resolution techniques that I applied to the study of several bright Galactic Cepheids. First, I used adaptive optic observations with NACO of the Cepheid RS Puppis, in order to deduce the flux ratio between the CSE and the photosphere of the star. In addition, I could carry out ...

  14. Evolution and pulsation period change in the Large Magellanic Cloud Cepheids

    CERN Document Server

    Fadeyev, Yuri A

    2013-01-01

    Theoretical estimates of the pulsation period change rates in LMC Cepheids are obtained from consistent calculation of stellar evolution and nonlinear stellar pulsation for stars with initial chemical composition X=0.7, Z=0.008, initial masses 5M_\\odot = 7M_\\odot pulsate in the fundamental mode and the period change rate \\dot\\Pi varies nearly by a factor of two for both crossings of the instability strip. In the period -- period change rate diagram the values of the period and \\dot\\Pi concentrate within the strips, their slope and half--width depending on both the direction of the movement in the HR--diagram and the pulsation mode. For oscillations in the fundamental mode the half-widths of the strip are \\delta\\log\\dot\\Pi = 0.35 and \\delta\\log\\dot\\Pi = 0.2 for the first and the second crossings of the instability strip, respectively. Results of computations are compared with observations of nearly 700 LMC Cepheids. Within existing observational uncertainties of \\dot\\Pi the theoretical dependences of the perio...

  15. Non-radial pulsation in first overtone Cepheids of the Small Magellanic Cloud

    Science.gov (United States)

    Smolec, R.; Śniegowska, M.

    2016-06-01

    We analyse photometry for 138 first overtone Cepheids from the Small Magellanic Cloud, in which Optical Gravitational Lensing Experiment team discovered additional variability with period shorter than first overtone period, and period ratios in the P/P1O ∈ (0.60, 0.65) range. In the Petersen diagram, these stars form three well-separated sequences. The additional variability cannot correspond to other radial mode. This form of pulsation is still puzzling. We find that amplitude of the additional variability is small, typically 2-4 per cent of the first overtone amplitude, which corresponds to 2-5 mmag. In some stars, we find simultaneously two close periodicities corresponding to two sequences in the Petersen diagram. The most important finding is the detection of power excess at half the frequency of the additional variability (at subharmonic) in 35 per cent of the analysed stars. Interestingly, power excess at subharmonic frequency is detected mostly for stars of the middle sequence in the Petersen diagram (74 per cent), incidence rate is much lower for stars of the top sequence (31 per cent), and phenomenon is not detected for stars of the bottom sequence. The amplitude and/or phase of the additional periodicities strongly vary in time. Similar form of pulsation is observed in first overtone RR Lyrae stars. Our results indicate that the nature and cause of this form of pulsation is the same in the two groups of classical pulsators; consequently, a common model explaining this form of pulsation should be searched for. Our results favour the theory of the excitation of non-radial modes of angular degrees 7, 8 and 9, proposed recently by Dziembowski.

  16. Non-radial pulsation in first overtone Cepheids of the Small Magellanic Cloud

    CERN Document Server

    Smolec, R

    2016-01-01

    We analyse photometry for 138 first overtone Cepheids from the Small Magellanic Cloud, in which Optical Gravitational Lensing Experiment (OGLE) team discovered additional variability with period shorter than first overtone period, and period ratios in the (0.60, 0.65) range. In the Petersen diagram these stars form three well separated sequences. The additional variability cannot correspond to other radial mode. This form of pulsation is still puzzling. We find that amplitude of the additional variability is small, typically 2-4 per cent of the first overtone amplitude, which corresponds to 2-5 mmag. In some stars we find simultaneously two close periodicities corresponding to two sequences in the Petersen diagram. The most important finding is the detection of power excess at half the frequency of the additional variability (at subharmonic) in 35 per cent of the analysed stars. Interestingly, power excess at subharmonic frequency is detected mostly for stars of the middle sequence in the Petersen diagram (74...

  17. On the Effect of Rotation on Populations of Classical Cepheids II. Pulsation Analysis for Metallicities 0.014, 0.006, and 0.002

    CERN Document Server

    Anderson, Richard I; Ekström, Sylvia; Georgy, Cyril; Meynet, Georges

    2016-01-01

    Classical Cepheid variable stars are high-sensitivity probes of stellar evolution and fundamental tracers of cosmic distances. While rotational mixing significantly affects the evolution of Cepheid progenitors (intermediate-mass stars), the impact of the resulting changes in stellar structure and composition on Cepheids on their pulsational properties is hitherto unknown. Here we present the first detailed pulsational instability analysis of stellar evolution models that include the effects of rotation, for both fundamental mode and first overtone pulsation. We employ Geneva evolution models spanning a three-dimensional grid in mass (1.7 - 15 $M_\\odot$), metallicity (Z = 0.014, 0.006, 0.002), and rotation (non-rotating, average & fast rotation). We determine (1) hot and cool instability strip (IS) boundaries taking into account the coupling between convection and pulsation, (2) pulsation periods, and (3) rates of period change. We investigate relations between period and (a) luminosity, (b) age, (c) radiu...

  18. On the effect of rotation on populations of classical Cepheids. II. Pulsation analysis for metallicities 0.014, 0.006, and 0.002

    Science.gov (United States)

    Anderson, R. I.; Saio, H.; Ekström, S.; Georgy, C.; Meynet, G.

    2016-06-01

    Classical Cepheid variable stars (from hereon: Cepheids) are high-sensitivity probes of stellar evolution and fundamental tracers of cosmic distances. While rotational mixing significantly affects the evolution of Cepheid progenitors (intermediate-mass stars), the impact of the resulting changes in stellar structure and composition on Cepheids and their pulsational properties is hitherto unknown. Here we present the first detailed pulsational instability analysis of stellar evolution models that include the effects of rotation, for both fundamental mode and first overtone pulsation. We employ Geneva evolution models spanning a three-dimensional grid in mass (1.7-15 M⊙), metallicity (Z = 0.014, 0.006, 0.002), and rotation (non-rotating, average & fast rotation). We determine (1) hot and cool instability strip (IS) boundaries taking into account the coupling between convection and pulsation; (2) pulsation periods; and (3) rates of period change. We investigate relations between period and (a) luminosity; (b) age; (c) radius; (d) temperature; (e) rate of period change; (f) mass; (g) the flux-weighted gravity-luminosity relation (FWGLR). We confront all predictions aside from those for age with observations, finding generally excellent agreement. We tabulate period-luminosity relations (PLRs) for several photometric pass-bands and investigate how the finite IS width, different IS crossings, metallicity, and rotation affect PLRs. We show that a Wesenheit index based on H, V, and I photometry is expected to have the smallest intrinsic PLR dispersion. We confirm that rotation resolves the Cepheid mass discrepancy. Period-age relations depend significantly on rotation, with rotation leading to older Cepheids, offering a straightforward explanation for evolved stars in binary systems that cannot be matched by conventional isochrones assuming a single age. We further show that Cepheids obey a tight FWGLR. Rotation is a fundamental property of stars that has important

  19. Mean angular diameters, distances, and pulsation modes of the classical Cepheids FF Aquilae and T Vulpeculae. CHARA/FLUOR near-infrared interferometric observations

    Science.gov (United States)

    Gallenne, A.; Kervella, P.; Mérand, A.; McAlister, H.; ten Brummelaar, T.; Coudé du Foresto, V.; Sturmann, J.; Sturmann, L.; Turner, N.; Farrington, C.; Goldfinger, P. J.

    2012-05-01

    We report the first angular diameter measurements of two classical Cepheids, FF Aql and T Vul, that we obtain using observations with the FLUOR instrument installed at the CHARA interferometric array. We derive average limb-darkened angular diameters of θLD = 0.878 ± 0.013 mas and θLD = 0.629 ± 0.013 mas, respectively, for FF Aql and T Vul. Combining these angular diameters with the HST-FGS trigonometric parallaxes leads to linear radii R = 33.6 ± 2.2 R⊙ and R = 35.6 ± 4.4 R⊙, respectively. The comparison with empirical and theoretical period-radius relations leads to the conclusion that these Cepheids are pulsating in their fundamental mode. The knowledge of this pulsation mode is of prime importance to calibrating the period-luminosity relation with a uniform sample of fundamental mode Cepheids.

  20. Mean angular diameters, distances and pulsation modes of the classical Cepheids FF Aql and T Vul - CHARA/FLUOR near-infrared interferometric observations

    CERN Document Server

    Gallenne, A; Mérand, A; McAlister, H; Brummelaar, T ten; Foresto, V Coudé du; Sturmann, J; Sturmann, L; Turner, N; Farrington, C; Goldfinger, P J

    2012-01-01

    We report the first angular diameter measurements of two classical Cepheids, FF Aql and T Vul, that we have obtained with the FLUOR instrument installed at the CHARA interferometric array. We obtain average limb-darkened angular diameters of \\theta_LD = 0.878 +/- 0.013 mas and \\theta_LD = 0.629 +/- 0.013 mas, respectively for FF Aql and T Vul. Combining these angular diameters with the HST-FGS trigonometric parallaxes leads to linear radii R = 33.6 +/- 2.2 Rsol and R = 35.6 +/- 4.4 Rsol, respectively. The comparison with empirical and theoretical Period-Radius relations leads to the conclusion that these Cepheids are pulsating in their fundamental mode. The knowledge of the pulsation mode is of prime importance to calibrate the Period-Luminosity relation with a uniform sample of fundamental mode Cepheids.

  1. Cepheid models based on self-consistent stellar evolution and pulsation calculations : The right answer?

    NARCIS (Netherlands)

    Baraffe, [No Value; Alibert, Y; Mera, D; Charbrier, G; Beaulieu, JP

    1998-01-01

    We have computed stellar evolutionary models for stars in a mass range characteristic of Cepheid variables (3

  2. Cepheid models based on self-consistent stellar evolution and pulsation calculations the right answer?

    CERN Document Server

    Baraffe, I; Méra, D; Chabrier, G; Beaulieu, J P

    1998-01-01

    We have computed stellar evolutionary models for stars in a mass range characteristic of Cepheid variables ($3

  3. Fourier analysis of short-period SMC Cepheids: A comparison with Galactic Cepheids

    Science.gov (United States)

    Buchler, J. Robert; Moskalik, Pawel

    1994-12-01

    A Fourier analysis has been made of the Small Magellanic Cloud (SMC) classical Cepheid data of Smith et al. It is shown that the grouping into fundamental and first overtone pulsators, implied by the period-luminosity diagram, survives when the Fourier coefficients are plotted versus period. A comparison with the Galactic Cepheid data corroborates the existing evidence that the short period Galactic s-Cepheids are indeed first overtone pulsators. The only long period overtone Cepheid in the sample that is reliably covered (P = 3.49 d) also conforms with the corresponding s-Cepheids. On the other hand, the hypothesis of Gieren et al. that the long period s-Cepheids are fundamental pulsators is refuted. The data show systematic differences between the SMC Cepheids and their Galactic counterparts, differences that are of theoretical interest. The need for a further observational effort devoted to SMC and to Large Magellanic cloud (LMC) Cepheids is stressed.

  4. RCT photometry of the Hubble Classical Cepheid V19 in M33: Evidence for the Cessation of Pulsations - A Case of Stellar Evolution in Real Time

    Science.gov (United States)

    Engle, Scott G.; Guinan, Edward F.; Macri, Lucas; Pellerin, Ann

    2011-03-01

    We report on our continuing efforts to monitor the photometric behavior of Hubble's Variable Star V19 in the Triangulum Spiral Galaxy M33. B,V photometry has been carried out of this unusual 18th mag (previous) Cepheid with the 1.3-m RCT (Robotically Controlled Telescope) at KPNO. With time-series photometry, with a dedicated robotic telescope, we can hope to solve the mystery of V19 and its unprecedented evolutionary behavior. In the influential work "A Spiral Nebula as a Stellar System: Messier 33" (Hubble 1926) Edwin Hubble determined the distance to M33 by using 35 Cepheids he discovered. One of those Cepheids was designated V19. At that time observations revealed V19 to have a 54.7-day period and B-band (converted from photographic magnitudes) light amplitude of 1.1-mag. Its mean B-magnitude was 19.6 /-0.2. V19 properties were consistent with the Period-Luminosity Law for M33 derived by Hubble at that time. Follow-up observations in 1996-1997 as part of the DIRECT Program (Macri et al. 2001), however, revealed large and surprising changes in the properties of V19. Its mean B-magnitude had risen to 19.05 /-0.05 and its amplitude had decreased to less than 0.1-mag. The DIRECT study thoroughly checked for possible misclassifications of the variable or contamination by nearby objects, and found none. For all intents and purposes, V19 is no longer a Classical Cepheid, or at least varying below the detectable levels of the photometry. The only other well-documented instance of Cepheid pulsations declining over time is in the case of Polaris - whose V-band amplitude decreased from just over 0.1-mag to below 0.03-mag over the course of a century (Engle et al 2004). Also, a study of the visual magnitudes of Polaris over the past two millennia has shown a possible increase in brightness of 1-mag over the past 1000 years. The changes observed for V19 are obviously on a much more dramatic scale. We discuss the properties of this unusual (former) Cepheid and discuss

  5. On the evolutionary and pulsation mass of Classical Cepheids: III. the case of the eclipsing binary Cepheid CEP0227 in the Large Magellanic Cloud

    CERN Document Server

    Moroni, P G Prada; Bono, G; Pietrzynski, G; Gieren, W; Pilecki, B; Graczyk, D; Thompson, I B; .,

    2012-01-01

    We present a new Bayesian approach to constrain the intrinsic parameters (stellar mass, age) of the eclipsing binary system CEP0227 in the LMC. We computed evolutionary models covering a broad range in chemical compositions and in stellar mass. Independent sets of models were constructed either by neglecting or by including a moderate convective core overshooting (beta=0.2) during central H-burning phases. Models were also constructed either by neglecting or by assuming a canonical (eta=0.4,0.8) or an enhanced (eta=4) mass loss rate. The solutions were computed in three different planes: luminosity-temperature, mass-radius and gravity-temperature. By using the Bayes Factor, we found that the most probable solutions were obtained in the gravity-temperature plane with a Gaussian mass prior distribution. The evolutionary models constructed by assuming a moderate convective core overshooting (beta=0.2) and a canonical mass loss rate (eta=0.4) give stellar masses for the primary Cepheid M=4.14^{+0.04}_{-0.05} M_su...

  6. ON THE EVOLUTIONARY AND PULSATION MASS OF CLASSICAL CEPHEIDS. III. THE CASE OF THE ECLIPSING BINARY CEPHEID CEP0227 IN THE LARGE MAGELLANIC CLOUD

    Energy Technology Data Exchange (ETDEWEB)

    Prada Moroni, P. G. [Dipartimento di Fisica, Universita di Pisa, Largo B. Pontecorvo 3, 56127 Pisa (Italy); Gennaro, M. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Bono, G. [Dipartimento di Fisica, Universita di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma (Italy); Pietrzynski, G.; Gieren, W.; Pilecki, B.; Graczyk, D. [Departamento de Astronomia, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile); Thompson, I. B., E-mail: prada@df.unipi.it [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101-1292 (United States)

    2012-04-20

    We present a new Bayesian approach to constrain the intrinsic parameters (stellar mass and age) of the eclipsing binary system-CEP0227-in the Large Magellanic Cloud (LMC). We computed several sets of evolutionary models covering a broad range in chemical compositions and in stellar mass. Independent sets of models were also constructed either by neglecting or by including a moderate convective core overshooting ({beta}{sub ov} = 0.2) during central hydrogen-burning phases. Sets of models were also constructed either by neglecting or by assuming a canonical ({eta} = 0.4, 0.8) or an enhanced ({eta} = 4) mass-loss rate. The most probable solutions were computed in three different planes: luminosity-temperature, mass-radius, and gravity-temperature. By using the Bayes factor, we found that the most probable solutions were obtained in the gravity-temperature plane with a Gaussian mass prior distribution. The evolutionary models constructed by assuming a moderate convective core overshooting ({beta}{sub ov} = 0.2) and a canonical mass-loss rate ({eta} = 0.4) give stellar masses for the primary (Cepheid)-M = 4.14{sup +0.04}{sub -0.05} M{sub Sun }-and for the secondary-M = 4.15{sup +0.04}{sub -0.05} M{sub Sun }-that agree at the 1% level with dynamical measurements. Moreover, we found ages for the two components and for the combined system-t = 151{sup +4}{sub -3} Myr-that agree at the 5% level. The solutions based on evolutionary models that neglect the mass loss attain similar parameters, while those ones based on models that either account for an enhanced mass loss or neglect convective core overshooting have lower Bayes factors and larger confidence intervals. The dependence on the mass-loss rate might be the consequence of the crude approximation we use to mimic this phenomenon. By using the isochrone of the most probable solution and a Gaussian prior on the LMC distance, we found a true distance modulus-18.53{sup +0.02}{sub -0.02} mag-and a reddening value-E(B - V

  7. Ultraviolet studies of Cepheids

    Science.gov (United States)

    Boehm-Vitense, Erika

    1992-01-01

    We discuss whether with new evolutionary tracks we still have a problem fitting the Cepheids and their evolved companions on the appropriate evolutionary tracks. We find that with the Bertelli et al. tracks with convective overshoot by one pressure scale height the problem is essentially removed, though somewhat more mixing would give a better fit. By using the results of recent nonlinear hydrodynamic calculations, we find that we also have no problem matching the observed pulsation periods of the Cepheids with those expected from their new evolutionary masses, provided that Cepheids with periods less than 9 days are overtone pulsators. We investigate possible mass loss of Cepheids from UV studies of the companion spectrum of S Mus and from the ultraviolet spectra of the long period Cepheid l Carinae. For S Mus with a period of 9.6 days we derive an upper limit for the mass loss of M less than 10(exp -9) solar mass, if a standard velocity law is assumed for the wind. For l Carinae with a period of 35.5 days we find a probable mass loss of M is approximately 10(exp -5+/-2) solar mass.

  8. The Araucaria Project : the Baade-Wesselink projection factor of pulsating stars

    CERN Document Server

    Nardetto, N; Gieren, W; Pietrzynski, G; Poretti, E

    2013-01-01

    The projection factor used in the Baade-Wesselink methods of determining the distance of Cepheids makes the link between the stellar physics and the cosmological distance scale. A coherent picture of this physical quantity is now provided based on several approaches. We present the lastest news on the expected projection factor for different kinds of pulsating stars in the Hertzsprung-Russell diagram.

  9. Period-Luminosity Relations for Cepheid Variables: From Mid-Infrared to Multi-Phase

    CERN Document Server

    Ngeow, Chow-Choong; Bellinger, Earl P; Marconi, Marcella; Musella, Ilaria; Cignoni, Michele; Lin, Ya-Hong

    2012-01-01

    This paper discusses two aspects of current research on the Cepheid period-luminosity (P-L) relation: the derivation of mid-infrared (MIR) P-L relations and the investigation of multi-phase P-L relations. The MIR P-L relations for Cepheids are important in the James Webb Space Telescope era for the distance scale issue, as the relations have potential to derive the Hubble constant within ~ 2% accuracy - a critical constraint in precision cosmology. Consequently, we have derived the MIR P-L relations for Cepheids in the Large and Small Magellanic Clouds, using archival data from Spitzer Space Telescope. We also compared currently empirical P-L relations for Cepheids in the Magellanic Clouds to the synthetic MIR P-L relations derived from pulsational models. For the study of multi-phase P-L relations, we present convincing evidence that the Cepheid P-L relations in the Magellanic Clouds are highly dynamic quantities that vary significantly when considered as a function of pulsational phase. We found that there ...

  10. Binary Cepheids from optical interferometry

    CERN Document Server

    Gallenne, A; Mérand, A; Monnier, J D; Pietrzyński, J Breitfelder G; Gieren, W

    2013-01-01

    Classical Cepheid stars have been considered since more than a century as reliable tools to estimate distances in the universe thanks to their Period-Luminosity (P-L) relationship. Moreover, they are also powerful astrophysical laboratories, providing fundamental clues for studying the pulsation and evolution of intermediate-mass stars. When in binary systems, we can investigate the age and evolution of the Cepheid, estimate the mass and distance, and constrain theoretical models. However, most of the companions are located too close to the Cepheid (1-40 mas) to be spatially resolved with a 10-meter class telescope. The only way to spatially resolve such systems is to use long-baseline interferometry. Recently, we have started a unique and long-term interferometric program that aims at detecting and characterizing physical parameters of the Cepheid companions, with as main objectives the determination of accurate masses and geometric distances.

  11. Convection, granulation and period jitter in classical Cepheids

    CERN Document Server

    Neilson, Hilding R

    2014-01-01

    Analyses of recent observations of the sole classical Cepheid in the Kepler field, V1154 Cygni, found random changes of about 30 minutes in the pulsation period. These period changes challenge standard theories of pulsation and evolution because the period change is non-secular, and explaining this period jitter is necessary for understanding stellar evolution and the role of Cepheids as precise standard candles. We suggest that convection and convective hot spots can explain the observed period jitter. Convective hot spots alter the timing of flux maximum and minimum in the Cepheid light curve, hence change the measured pulsation period. We present a model of random hot spots that generate a localized flux excess that perturbs the Cepheid light curve and consequently the pulsation period which is consistent with the observed jitter. This result demonstrates how important understanding convection is for modeling Cepheid stellar structure and evolution, how convection determines the red edge of the instability...

  12. The chemical composition of Galactic beat Cepheids

    Science.gov (United States)

    Kovtyukh, V.; Lemasle, B.; Chekhonadskikh, F.; Bono, G.; Matsunaga, N.; Yushchenko, A.; Anderson, R. I.; Belik, S.; da Silva, R.; Inno, L.

    2016-08-01

    We determine the metallicity and detailed chemical abundances (α, iron-peak and neutron-capture elements) for the almost complete (18/24) sample of Galactic double mode Cepheids (also called beat Cepheids). Double mode Cepheids are Cepheids that pulsate in two modes simultaneously. We calibrate a new relation between their metallicity and their period ratio P1/P0. This linear relation allows to determine the metallicity of bimodal Cepheids with an accuracy of 0.03 dex in the range of [Fe/H] from +0.2 to -0.5 dex. By extrapolating the relation to Magellanic Clouds beat Cepheids, we provide their metallicity distribution function. Moreover, by using this relation, we also provide the first metallicity estimate for two double-mode F/1O Cepheids located in and beyond the Galactic bulge. Finally, we report the discovery of a super-Lithium rich double mode Cepheid V371 Per which has a Lithium abundance of logA(Li) = 3.54 ± 0.09 dex. Along with V1033 Cyg (which is an ordinary classical Cepheid), it is the second known Cepheid of such type in the Galaxy.

  13. Masses for Galactic Beat Cepheids

    Science.gov (United States)

    D'Cruz, Noella L.; Morgan, Siobahn M.; Böhm-Vitense, Erika

    2000-08-01

    Accurate mass determinations for Cepheids may be used to determine the degree of excess mixing in the interiors of their main-sequence progenitors: the larger the excess mixing, the larger the luminosity of the Cepheid of a given mass, or the smaller the mass of a Cepheid with given luminosity. Dynamical masses determined recently for a few Cepheid binaries indicate excess mixing somewhat stronger than that corresponding to the convective overshoot models by Schaller et al. Beat Cepheids can be used similarly to test main-sequence mixing in stellar interiors. The period ratios for beat Cepheids depend on luminosity, Teff, heavy element abundance, and mass. By comparing pulsational models and the observationally derived luminosity, Teff, metallicities, and period ratios it is possible to obtain masses for these stars, the so-called beat masses. With the old opacities masses much smaller than the evolutionary masses were obtained. With the new OPAL opacities a beat mass close to the dynamical mass was obtained for the binary beat Cepheid Y Carinae, showing that it is now possible to obtain reliable beat masses. In this paper, we determine beat masses for seven Galactic beat Cepheids for which photometric and spectroscopic data are available. We find an average mass around 4.2+/-0.3 Msolar for these stars, though the actual error limits for each star may be larger mainly because of uncertainties in E(B-V) and the heavy element abundances. (As derived spectroscopically, beat Cepheids are in general metal-poor, with -0.4relation between the derived beat masses and the luminosities again indicates excess mixing that is somewhat larger than that corresponding to the models by Schaller et al.

  14. Cepheid distances from the SpectroPhoto-Interferometry of Pulsating Stars (SPIPS) - Application to the prototypes delta Cep and eta Aql

    CERN Document Server

    Merand, Antoine; Breitfelder, Joanne; Gallenne, Alexandre; Foresto, Vincent Coude du; Brummelaar, Theo A ten; McAlister, Harold A; Ridgway, Stephen; Sturmann, Laszlo; Sturmann, Judit; Turner, Nils H

    2015-01-01

    The parallax of pulsation, and its implementations such as the Baade-Wesselink method and the infrared surface bright- ness technique, is an elegant method to determine distances of pulsating stars in a quasi-geometrical way. However, these classical implementations in general only use a subset of the available observational data. Freedman & Madore (2010) suggested a more physical approach in the implementation of the parallax of pulsation in order to treat all available data. We present a global and model-based parallax-of-pulsation method that enables including any type of observational data in a consistent model fit, the SpectroPhoto-Interferometric modeling of Pulsating Stars (SPIPS). We implemented a simple model consisting of a pulsating sphere with a varying effective temperature and a combina- tion of atmospheric model grids to globally fit radial velocities, spectroscopic data, and interferometric angular diameters. We also parametrized (and adjusted) the reddening and the contribution of the cir...

  15. High resolution spectroscopy for Cepheids distance determination. II. A period- projection factor relation

    CERN Document Server

    Nardetto, N; Mathias, Ph; Fokin, A; Gillet, D

    2008-01-01

    The projection factor is a key quantity for the interferometric Baade-Wesselink (hereafter IBW) and surface-brightness (hereafter SB) methods of determining the distance of Cepheids. Indeed, it allows a consistent combination of angular and linear diameters of the star. We aim to determine consistent projection factors that include the dynamical structure of the Cepheids' atmosphere. Methods. Hydrodynamical models of delta Cep and l Car have been used to validate a spectroscopic method of determining the projection factor. This method, based on the amplitude of the radial velocity curve, is applied to eight stars observed with the HARPS spectrometer. The projection factor is divided into three sub-concepts : (1) a geometrical effect, (2) the velocity gradient within the atmosphere, and (3) the relative motion of the "optical" pulsating photosphere compared to the corresponding mass elements (hereafter fo-g). Both, (1) and (3) are deduced from geometrical and hydrodynamical models, respectively, while (2) is d...

  16. Cepheid evolution

    International Nuclear Information System (INIS)

    A review of the phases of stellar evolution relevant to Cepheid variables of both Types I and II is presented. Type I Cepheids arise as a result of normal post-main sequence evolutionary behavior of many stars in the intermediate to massive range of stellar masses. In contrast, Type II Cepheids generally originate from low-mass stars of low metalicity which are undergoing post core helium-burning evolution. Despite great progress in the past two decades, uncertainties still remain in such areas as how to best model convective overshoot, semiconvection, stellar atmospheres, rotation, and binary evolution as well as uncertainties in important physical parameters such as the nuclear reaction rates, opacity, and mass loss rates. The potential effect of these uncertainties on stellar evolution models is discussed. Finally, comparisons between theoretical predictions and observations of Cepheid variables are presented for a number of cases. The results of these comparisons show both areas of agreement and disagreement with the latter result providing incentive for further research

  17. Discovery of the spectroscopic binary nature of the classical Cepheids FN Aql and V1344 Aql

    CERN Document Server

    Szabados, L; Kovács, J; Csák, B; Dózsa, Á; Szabó, Gy M; Simon, A E; Borkovits, T; Kiss, L L; Jankovics, I; Mező, Gy

    2014-01-01

    We present the analysis of photometric and spectroscopic data of two classical Cepheids, FN Aquilae and V1344 Aquilae. Based on the joint treatment of the new and earlier radial velocity data, both Galactic Cepheids have been found to be a member in a spectroscopic binary system. To match the phases of the earlier radial velocity data correctly with the new ones, we also determined the temporal behaviour of the pulsation period of these Cepheids based on all available photometric data. The O-C graph covering about half century shows slight changes in the pulsation period due to stellar evolution for both Cepheids.

  18. CEPHEID VARIABLES IN THE MASER-HOST GALAXY NGC 4258

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, Samantha L.; Macri, Lucas M., E-mail: lmacri@tamu.edu [George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States)

    2015-06-15

    We present results of a ground-based survey for Cepheid variables in NGC 4258. This galaxy plays a key role in the Extragalactic Distance Scale due to its very precise and accurate distance determination via very long baseline interferometry observations of water masers. We imaged two fields within this galaxy using the Gemini North telescope and the Gemini Multi-Object Spectrograph, obtaining 16 epochs of data in the Sloan Digital Sky Survey gri bands over 4 yr. We carried out point-spread function photometry and detected 94 Cepheids with periods between 7 and 127 days, as well as an additional 215 variables which may be Cepheids or Population II pulsators. We used the Cepheid sample to test the absolute calibration of theoretical gri Period–Luminosity relations and found good agreement with the maser distance to this galaxy. The expected data products from the Large Synoptic Survey Telescope should enable Cepheid searches out to at least 10 Mpc.

  19. Cepheid Variables in the Maser-Host Galaxy NGC 4258

    CERN Document Server

    Hoffmann, Samantha L

    2015-01-01

    We present results of a ground-based survey for Cepheid variables in NGC 4258. This galaxy plays a key role in the Extragalactic Distance Scale due to its very precise and accurate distance determination via VLBI observations of water masers. We imaged two fields within this galaxy using the Gemini North telescope and GMOS, obtaining 16 epochs of data in the SDSS gri bands over 4 years. We carried out PSF photometry and detected 94 Cepheids with periods between 7 and 127 days, as well as an additional 215 variables which may be Cepheids or Population II pulsators. We used the Cepheid sample to test the absolute calibration of theoretical gri Period-Luminosity relations and found good agreement with the maser distance to this galaxy. The expected data products from the Large Synoptic Survey Telescope (LSST) should enable Cepheid searches out to at least 10 Mpc.

  20. Multi-Mode Oscillations in Classical Cepheids and RR Lyrae-Type Stars

    CERN Document Server

    Moskalik, Paweł

    2014-01-01

    I review different types of multi-mode pulsations observed in classical Cepheids and in RR Lyrae-type star. The presentation concentrates on the newest results, with special emphasis on recently detected nonradial oscillations.

  1. Cepheid investigations using the Kepler space telescope

    CERN Document Server

    Szabó, R; Ngeow, C -C; Smolec, R; Derekas, A; Moskalik, P; Nuspl, J; Lehmann, H; Fűrész, G; Molenda-Zakowicz, J; Bryson, S T; Henden, A A; Kurtz, D W; Stello, D; Nemec, J M; Benkő, J M; Berdnikov, L; Bruntt, H; Evans, N R; Gorynya, N A; Pastukhova, E N; Simcoe, R J; Grindlay, J E; Los, E J; Doane, A; Laycock, S G; Mink, D J; Champine, G; Sliski, A; Handler, G; Kiss, L L; Kolláth, Z; Kovács, J; Christensen-Dalsgaard, J; Kjeldsen, H; Allen, C; Thompson, S E; Van Cleve, J

    2011-01-01

    We report results of initial work done on selected candidate Cepheids to be observed with the Kepler space telescope. Prior to the launch 40 candidates were selected from previous surveys and databases. The analysis of the first 322 days of Kepler photometry, and recent ground-based follow-up multicolour photometry and spectroscopy allowed us to confirm that one of these stars, V1154 Cyg (KIC 7548061), is indeed a 4.9-d Cepheid. Using the phase lag method we show that this star pulsates in the fundamental mode. New radial velocity data are consistent with previous measurements, suggesting that a long-period binary component is unlikely. No evidence is seen in the ultra-precise, nearly uninterrupted Kepler photometry for nonradial or stochastically excited modes at the micromagnitude level. The other candidates are not Cepheids but an interesting mix of possible spotted stars, eclipsing systems and flare stars.

  2. The strange evolution of the Large Magellanic Cloud Cepheid OGLE-LMC-CEP1812

    CERN Document Server

    Neilson, Hilding R; Langer, Norbert; Ignace, Richard

    2015-01-01

    Classical Cepheids are key probes of both stellar astrophysics and cosmology as standard candles and pulsating variable stars. It is important to understand Cepheids in unprecedented detail in preparation for upcoming GAIA, JWST and extremely-large telescope observations. Cepheid eclipsing binary stars are ideal tools for achieving this goal, however there are currently only three known systems. One of those systems, OGLE-LMC-CEP1812, raises new questions about the evolution of classical Cepheids because of an apparent age discrepancy between the Cepheid and its red giant companion. We show that the Cepheid component is actually the product of a stellar merger of two main sequence stars that has since evolved across the Hertzsprung gap of the HR diagram. This post-merger product appears younger than the companion, hence the apparent age discrepancy is resolved. We discuss this idea and consequences for understanding Cepheid evolution.

  3. The strange evolution of the Large Magellanic Cloud Cepheid OGLE-LMC-CEP1812

    Science.gov (United States)

    Neilson, Hilding R.; Izzard, Robert G.; Langer, Norbert; Ignace, Richard

    2015-09-01

    Classical Cepheids are key probes of both stellar astrophysics and cosmology as standard candles and pulsating variable stars. It is important to understand Cepheids in unprecedented detail in preparation for upcoming Gaia, James Webb Space Telescope (JWST) and extremely-large telescope observations. Cepheid eclipsing binary stars are ideal tools for achieving this goal, however there are currently only three known systems. One of those systems, OGLE-LMC-CEP1812, raises new questions about the evolution of classical Cepheids because of an apparent age discrepancy between the Cepheid and its red giant companion. We show that the Cepheid component is actually the product of a stellar merger of two main sequence stars that has since evolved across the Hertzsprung gap of the HR diagram. This post-merger product appears younger than the companion, hence the apparent age discrepancy is resolved. We discuss this idea and consequences for understanding Cepheid evolution.

  4. Anomalous Cepheid period-luminosity relationships

    International Nuclear Information System (INIS)

    The P-L relationship for anomalous Cepheids (ACs) splits into two well-defined lines in the log P - M(B) plane. One line corresponds to pulsation in the fundamental mode, and the other corresponds to the first-overtone. If these P-L relationships are universal, then they can be used to estimate distances to nearby dwarf galaxies. Knowledge of pulsation modes of the ACs in Draco suggests a mass range of 1.04 to 1.7 solar mass

  5. What masses for Cepheids

    International Nuclear Information System (INIS)

    To understand the evolution of giant stars, it is important to pin down the masses for Cepheids. The 7- to 10-day bump Cepheids imply lower than evolutionary mass (60%). Recent theoretical work, though, indicates that for Cepheids with periods of 15 to 16 days, the best understanding of the light curves results from using evolutionary masses

  6. Observational calibration of the projection factor of Cepheids. II. Application to nine Cepheids with HST/FGS parallax measurements

    CERN Document Server

    Breitfelder, Joanne; Kervella, Pierre; Gallenne, Alexandre; Szabados, Laszlo; Anderson, Richard I; Bouquin, Jean-Baptiste Le

    2016-01-01

    The distance to pulsating stars is classically estimated using the parallax-of-pulsation (PoP) method, which combines spectroscopic radial velocity measurements and angular diameter estimates to derive the distance of the star. An important application of this method is the determination of Cepheid distances, in view of the calibration of their distance scale. However, the conversion of radial to pulsational velocities in the PoP method relies on a poorly calibrated parameter, the projection factor (p-factor). We aim to measure empirically the value of the p-factors of a homogeneous sample of nine Galactic Cepheids for which trigonometric parallaxes were measured with the Hubble Space Telescope Fine Guidance Sensor. We use the SPIPS algorithm, a robust implementation of the PoP method that combines photometry, interferometry, and radial velocity measurements in a global modeling of the pulsation. We obtained new interferometric angular diameters using the PIONIER instrument at the Very Large Telescope Interfe...

  7. Cepheid Companions and the Masses of Cepheids

    Science.gov (United States)

    Bohm-Vitense, E.; Borutzki, S.; Harris, H.

    The authors have observed in the ultraviolet the hot companions of the Cepheids SV Per, RW Cam, SY Nor and KN Cen. The study of the absolute and relative intensities reveals that all, except the companion for KN Cen are evolved stars which should fit on almost the same mass track as the Cepheid. The authors find however that with generally accepted reddening values the companions of at least SV Per and RW Cam are too faint. Either the Cepheid loops are more luminous than presently calculated or the reddening is larger than presently accepted.

  8. Mode selection in pulsating stars

    CERN Document Server

    Smolec, R

    2013-01-01

    In this review we focus on non-linear phenomena in pulsating stars the mode selection and amplitude limitation. Of many linearly excited modes only a fraction is detected in pulsating stars. Which of them and why (the problem of mode selection) and to what amplitude (the problem of amplitude limitation) are intrinsically non-linear and still unsolved problems. Tools for studying these problems are briefly discussed and our understanding of mode selection and amplitude limitation in selected groups of self-excited pulsators is presented. Focus is put on classical pulsators (Cepheids and RR Lyrae stars) and main sequence variables (delta Scuti and beta Cephei stars). Directions of future studies are briefly discussed.

  9. On the pulsation and evolutionary properties of helium burning radially pulsating variables

    Science.gov (United States)

    Bono, G.; Pietrinferni, A.; Marconi, M.; Braga, V. F.; Fiorentino, G.; Stetson, P. B.; Buonanno, R.; Castellani, M.; Dall'Ora, M.; Fabrizio, M.; Ferraro, I.; Giuffrida, G.; Iannicola, G.; Marengo, M.; Magurno, D.; Martinez-Vazquez, C. E.; Matsunaga, N.; Monelli, M.; Neeley, J.; Rastello, S.; Salaris, M.; Short, L.; Stellingwerf, R. F.

    2016-05-01

    We discuss pulsation and evolutionary properties of low- (RR Lyrae, Type II Cepheids) and intermediate-mass (Anomalous Cepheids) radial variables. We focus our attention on the topology of the instability strip and the distribution of the quoted variables in the Hertzsprung-Russell diagram. We discuss their evolutionary status and the dependence on the metallicity. Moreover, we address the diagnostics (period derivative, difference in luminosity, stellar mass) that can provide solid constraints on their progenitors and on the role that binarity and environment have in shaping their current pulsation characteristics. Finally, we briefly outline their use as standard candles.

  10. The VMC Survey. XIX. Classical Cepheids in the Small Magellanic Cloud

    Science.gov (United States)

    Ripepi, V.; Marconi, M.; Moretti, M. I.; Clementini, G.; Cioni, M.-R. L.; de Grijs, R.; Emerson, J. P.; Groenewegen, M. A. T.; Ivanov, V. D.; Piatti, A. E.

    2016-06-01

    The “VISTA near-infrared YJK s survey of the Magellanic Clouds System” (VMC) is collecting deep K s-band time-series photometry of pulsating variable stars hosted by the two Magellanic Clouds and their connecting Bridge. In this paper, we present Y, J, K s light curves for a sample of 4172 Small Magellanic Cloud (SMC) Classical Cepheids (CCs). These data, complemented with literature V values, allowed us to construct a variety of period–luminosity (PL), period–luminosity–color (PLC), and period–Wesenheit (PW) relationships, which are valid for Fundamental (F), First Overtone (FO), and Second Overtone (SO) pulsators. The relations involving the V, J, K s bands are in agreement with their counterparts in the literature. As for the Y band, to our knowledge, we present the first CC PL, PW, and PLC relations ever derived using this filter. We also present the first near–infrared PL, PW, and PLC relations for SO pulsators to date. We used PW(V, K s) to estimate the relative SMC–LMC distance and, in turn, the absolute distance to the SMC. For the former quantity, we find a value of Δμ = 0.55 ± 0.04 mag, which is in rather good agreement with other evaluations based on CCs, but significantly larger than the results obtained from older population II distance indicators. This discrepancy might be due to the different geometric distributions of young and old tracers in both Clouds. As for the absolute distance to the SMC, our best estimates are μ SMC = 19.01 ± 0.05 mag and μ SMC = 19.04 ± 0.06 mag, based on two distance measurements to the LMC which rely on accurate CC and eclipsing Cepheid binary data, respectively.

  11. The VMC Survey. VI. First results for Classical Cepheids

    CERN Document Server

    Ripepi, V; Marconi, M; Clementini, G; Cioni, M R; Marquette, J B; Girardi, L; Rubele, S; Groenewegen, M A T; de Grijs, R; Gibson, B K; Oliveira, J M; van Loon, J Th

    2012-01-01

    The VISTA Magellanic Cloud (VMC, PI M.R. Cioni) survey is collecting deep Ks-band time-series photometry of the pulsating variable stars hosted by the system formed by the two Magellanic Clouds (MCs) and the "bridge" connecting them. In this paper we present the first results for Classical Cepheids, from the VMC observations of two fields in the Large Magellanic Cloud (LMC). The VMC Ks-band light curves of the Cepheids are well sampled (12-epochs) and of excellent precision. We were able to measure for the first time the Ks magnitude of the faintest Classical Cepheids in the LMC (Ks\\sim17.5 mag), which are mostly pulsating in the First Overtone (FO) mode, and to obtain FO Period-Luminosity (PL), Period-Wesenheit (PW), and Period-Luminosity-Color (PLC) relations, spanning a whole period range from 0.25 to 6 days. Saturation limits our Ks measurements of the Fundamental mode (F) Cepheids to periods shorter than 15-20 days. Therefore, we have complemented our sample with literature data for brighter F Cepheids. ...

  12. CLUSTERED CEPHEID VARIABLES 90 KILOPARSECS FROM THE GALACTIC CENTER

    Energy Technology Data Exchange (ETDEWEB)

    Chakrabarti, Sukanya [School of Physics and Astronomy, Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY 14623 (United States); Saito, Roberto [Departamento de Fisica-Universidade Federal de Sergipe, Rod. Marechal Rondon s/n-Jardim Rosa Elze, Sao Cristovao, 49.100-000, Sergipe (Brazil); Quillen, Alice [Department of Physics and Astronomy, University of Rochester, Rochester NY 14627 (United States); Gran, Felipe [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica of Chile, Av. Vicuña Mackenna 4860, Santiago (Chile); Klein, Christopher; Blitz, Leo, E-mail: chakrabarti@astro.rit.edu [Astronomy Department, UC Berkeley, Berkeley CA 94720 (United States)

    2015-03-20

    Distant regions close to the plane of our Galaxy are largely unexplored by optical surveys as they are hidden by dust. We have used near-infrared data (which minimizes dust obscuration) from the ESO Public survey VISTA Variables of the Via Lactea to search for distant stars at low latitudes. We have discovered four Cepheid variables within an angular extent of 1° centered at a Galactic longitude of l = −27.°4 and a Galactic latitude of b = −1.°08. We use the tightly constrained period–luminosity relationship that these pulsating stars obey to derive distances. We infer an average distance to these Cepheid variables of 90 kpc. The Cepheid variables are highly clustered in angle (within 1°) and in distance (the standard deviation of the distances is 12 kpc). These young (∼100 Myr old), pulsating stars are unexpected at such large distances from the Galactic disk, which terminates at ∼15 kpc. The highly clustered nature in distance and angle of the Cepheid variables suggests that the stars may be associated with a dwarf galaxy; its location and mass were earlier predicted by a dynamical analysis. The Cepheids are at an average distance of ∼2 kpc from the plane and their maximum projected separation is ∼1 kpc.

  13. Revisiting the fundamental properties of Cepheid Polaris using detailed stellar evolution models

    CERN Document Server

    Neilson, Hilding R

    2014-01-01

    Polaris the Cepheid has been observed for centuries, presenting surprises and changing our view of Cepheids and stellar astrophysics, in general. Specifically, understanding Polaris helps anchor the Cepheid Leavitt law, but the distance must be measured precisely. The recent debate regarding the distance to Polaris has raised questions about its role in calibrating the Leavitt law and even its evolutionary status. In this work, I present new stellar evolution models of Cepheids to compare with previously measured CNO abundances, period change and angular diameter. Based on the comparison, I show that Polaris cannot be evolving along the first crossing of the Cepheid instability strip and cannot have evolved from a rapidly-rotating main sequence star. As such, Polaris must also be at least 118 pc away and pulsates in the first overtone, disagreeing with the recent results of Turner et al. (2013).

  14. Pulsating Star Mystery Solved

    Science.gov (United States)

    2010-11-01

    By discovering the first double star where a pulsating Cepheid variable and another star pass in front of one another, an international team of astronomers has solved a decades-old mystery. The rare alignment of the orbits of the two stars in the double star system has allowed a measurement of the Cepheid mass with unprecedented accuracy. Up to now astronomers had two incompatible theoretical predictions of Cepheid masses. The new result shows that the prediction from stellar pulsation theory is spot on, while the prediction from stellar evolution theory is at odds with the new observations. The new results, from a team led by Grzegorz Pietrzyński (Universidad de Concepción, Chile, Obserwatorium Astronomiczne Uniwersytetu Warszawskiego, Poland), appear in the 25 November 2010 edition of the journal Nature. Grzegorz Pietrzyński introduces this remarkable result: "By using the HARPS instrument on the 3.6-metre telescope at ESO's La Silla Observatory in Chile, along with other telescopes, we have measured the mass of a Cepheid with an accuracy far greater than any earlier estimates. This new result allows us to immediately see which of the two competing theories predicting the masses of Cepheids is correct." Classical Cepheid Variables, usually called just Cepheids, are unstable stars that are larger and much brighter than the Sun [1]. They expand and contract in a regular way, taking anything from a few days to months to complete the cycle. The time taken to brighten and grow fainter again is longer for stars that are more luminous and shorter for the dimmer ones. This remarkably precise relationship makes the study of Cepheids one of the most effective ways to measure the distances to nearby galaxies and from there to map out the scale of the whole Universe [2]. Unfortunately, despite their importance, Cepheids are not fully understood. Predictions of their masses derived from the theory of pulsating stars are 20-30% less than predictions from the theory of the

  15. PR and PL (PM_V Relations for Classical Cepheids Revisited

    Directory of Open Access Journals (Sweden)

    Šegan, S.

    2009-12-01

    Full Text Available Using observational data available for a large number of Galactic Cepheids, we determine the relation between the radius and the period of pulsations, by means of a variant of the Baade-Wesselink method. Using, further, the brightness parameter according to the Barnes-Evans approach, we achieve our final goal, determination of the relation between the period and the mean luminosity. The coefficients in both relations are realistic. We indicate the need for accurate angular diameters of the Cepheids, which would be useful since the Cepheids are standard candles in the cosmic distance scale.

  16. Non-linear modelling of beat Cepheids: Resonant and non-resonant models

    CERN Document Server

    Smolec, R

    2010-01-01

    The phenomenon of double-periodic Cepheid pulsation is still poorly understood. Recently we rediscussed the problem of modelling the double-periodic pulsation with non-linear hydrocodes. We showed that the published non-resonant double-mode models are incorrect, because they exclude the negative buoyancy effects. Aims. We continue our efforts to verify whether the Kuhfuss one-equation convection model with negative buoyancy included can reproduce the double-periodic Cepheid pulsation. Methods. Using the direct time integration hydrocode, which implements the Kuhfuss convection model, we search for stable double-periodic Cepheid models. We search for models pulsating in both fundamental and first overtone modes (F+1O), as well as in the two lowest order overtones (1O+2O). In the latter case, we focus on reproducing double-overtone Cepheids of the Large Magellanic Cloud (LMC). Results. We have found full amplitude non-linear beat Cepheid models of both types, F+1O and 1O+2O. In the case of F+1O models, the beat...

  17. The Secret Lives of Cepheids: Evolution, Mass-Loss, and Ultraviolet Emission of the Long-period Classical Cepheid

    Science.gov (United States)

    Neilson, Hilding R.; Engle, Scott G.; Guinan, Edward F.; Bisol, Alexandra C.; Butterworth, Neil

    2016-06-01

    The classical Cepheid l Carinae is an essential calibrator of the Cepheid Leavitt Law as a rare long-period Galactic Cepheid. Understanding the properties of this star will also constrain the physics and evolution of massive (M ≥ 8 M ⊙) Cepheids. The challenge, however, is precisely measuring the star's pulsation period and its rate of period change. The former is important for calibrating the Leavitt Law and the latter for stellar evolution modeling. In this work, we combine previous time-series observations spanning more than a century with new observations to remeasure the pulsation period and compute the rate of period change. We compare our new rate of period change with stellar evolution models to measure the properties of l Car, but find models and observations are, at best, marginally consistent. The results imply that l Car does not have significantly enhanced mass-loss rates like that measured for δ Cephei. We find that the mass of l Car is about 8-10 M ⊙. We present Hubble Space Telescope Cosmic Origins Spectrograph observations that also differ from measurements for δ Cep and β Dor. These measurements further add to the challenge of understanding the physics of Cepheids, but do hint at the possible relation between enhanced mass-loss and ultraviolet emission, perhaps both due to the strength of shocks propagating in the atmospheres of Cepheids. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program #13019. This work is also based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and the USA (NASA), associated with program #060374.

  18. The Secret Lives of Cepheids: Evolution, Mass Loss, and Ultraviolet Emission of the Long-Period Classical Cepheid $l$ Carinae

    CERN Document Server

    Neilson, Hilding R; Guinan, Edward F; Bisol, Alexandra C; Butterworth, Neil

    2016-01-01

    The classical Cepheid $l$ Carinae is an essential calibrator of the Cepheid Leavitt Law as a rare long-period Galactic Cepheid. Understanding the properties of this star will also constrain the physics and evolution of massive ($M \\ge 8$ $M_\\odot$) Cepheids. The challenge, however, is precisely measuring the star's pulsation period and its rate of period change. The former is important for calibrating the Leavitt Law and the latter for stellar evolution modeling. In this work, we combine previous time-series observations spanning more than a century with new observations to remeasure the pulsation period and compute the rate of period change. We compare our new rate of period change with stellar evolution models to measure the properties of $l$ Car, but find models and observations are, at best, marginally consistent. The results imply that $l$ Car does not have significantly enhanced mass-loss rates like that measured for $\\delta$ Cephei. We find that the mass of $l$ Car is about 8 - 10 $M_\\odot$. We present...

  19. Double-Overtone Cepheids in the Large Magellanic Cloud

    CERN Document Server

    Dziembowski, W A

    2009-01-01

    One of the most interesting results from the OGLE-III study of the LMC Cepheids is the large number of objects that pulsate simultaneously in the first and second overtone (denoted 1O/2O). Double-mode Cepheids yield important constraint on stellar evolution models. We show that great majority of the LMC 1O/2O Cepheids have masses M=3.0+/-0.5 Msun. According to current stellar evolution calculations, these masses are lower than needed for the blue loop in the helium burning phase to reach the instability strip. On the other hand, we found most of these stars significantly overluminous if they are crossing the instability before helium ignition. A possible solution of this discrepancy is to allow for a large overshooting from the convective core in the main sequence phase. We also discuss origin of double-mode pulsation. At the short period range we find two types of resonances that are conducive to this form of pulsation. However, at longer periods, it has a different (non-resonant) origin.

  20. The Cepheid Galactic Internet

    CERN Document Server

    Learned, John G; Pakvasa, Sandip; Zee, A

    2008-01-01

    We propose that a sufficiently advanced civilization may employ Cepheid variable stars as beacons to transmit all-call information throughout the galaxy and beyond. One can construct many scenarios wherein it would be desirable for such a civilization of star ticklers to transmit data to anyone else within viewing range. The beauty of employing Cepheids is that these stars can be seen from afar(we monitor them out through the Virgo cluster), and any developing technological society would seem to be likely to closely observe them as distance markers. Records exist of Cepheids for well over one hundred years. We propose that these (and other regularly variable types of stars) be searched for signs of phase modulation (in the regime of short pulse duration) and patterns, which could be indicative of intentional signaling.

  1. Light Curves for Type II Cepheids in M3 and M5

    Science.gov (United States)

    Rabidoux, K.; Smith, H. A.; Wells, K.; Randall, J.; Hartley, D.; LaCluyze, A.; De Lee, N.; Ingber, M.; Ireland, M.; KInemuchi, K.; Pellegrini, E.; Purdum, L. E.; Pritzl, B. J.; Lustig, R.; Osborn, W.; Lacy, J.; Curtis, M.; Smolinski, J.

    2005-12-01

    Many of the longer period Cepheids within globular clusters do not have modern light curves in the standard B, V, and Cousins-I photometric bandpasses. As part of a larger program to secure B, V, and I band photometry for these type II Cepheids, we have obtained CCD images of the globular clusters M3 and M5. Data were obtained with the 60-cm telescope at Michigan State University and the 40-cm telescopes at Macalester College and Central Michigan University. Light curves are presented for several Cepheids in these clusters. V84 in M5 shows evidence of alternating high and low maxima, indicative of RV Tauri behavior, and may mark the dividing line between pulsations of the type II Cepheid and RV Tauri variety. Observations have also been obtained for type II Cepheids in the globular clusters M2, M10, M12, and M13. Light curves for these variables will be used to investigate the period-luminosity relation for globular cluster Cepheids and to study their pulsational properties. This work has been supported in part by the National Science Foundation.

  2. 3D Convection-pulsation Simulations with the HERACLES Code

    Science.gov (United States)

    Felix, S.; Audit, E.; Dintrans, B.

    2015-10-01

    We present 3D simulations of the coupling between surface convection and pulsations due to the κ-mechanism in classical Cepheids of the red edge of Hertzsprung-Russell diagram's instability strip. We show that 3D convection is less powerful than 2D convection and does not quench the radiative pulsations, leading to an efficient 3D κ-mechanism. Thus, the 3D instability strip is closer to the observed one than the 1D or 2D were.

  3. The ARAUCARIA project. OGLE-LMC-CEP-1718: An exotic eclipsing binary system composed of two classical overtone cepheids in a 413 day orbit

    Energy Technology Data Exchange (ETDEWEB)

    Gieren, Wolfgang; Pilecki, Bogumił; Pietrzyński, Grzegorz; Graczyk, Dariusz; Gallenne, Alexandre, E-mail: wgieren@astro-udec.cl, E-mail: pietrzyn@astrouw.edu.pl, E-mail: darek@astro-udec.cl, E-mail: dgallenne@astro-udec.cl, E-mail: bpilecki@astro-udec.cl [Departamento de Astronomia, Universidad de Concepción, Casilla 160-C, Concepción (Chile); and others

    2014-05-10

    We have obtained extensive high-quality spectroscopic observations of the OGLE-LMC-CEP-1718 eclipsing binary system in the Large Magellanic Cloud that Soszyński et al. had identified as a candidate system for containing two classical Cepheids in orbit. Our spectroscopic data clearly demonstrate binary motion of the Cepheids in a 413 day eccentric orbit, rendering this eclipsing binary system the first ever known to consist of 2 classical Cepheid variables. After disentangling the four different radial velocity variations in the system, we present the orbital solution and the individual pulsational radial velocity curves of the Cepheids. We show that both Cepheids are extremely likely to be first overtone pulsators and determine their respective dynamical masses, which turn out to be equal to within 1.5%. Since the secondary eclipse is not observed in the orbital light curve, we cannot derive the individual radii of the Cepheids, but the sum of their radii derived from the photometry is consistent with overtone pulsation for both variables. The existence of two equal-mass Cepheids in a binary system having different pulsation periods (1.96 and 2.48 days, respectively) may pose an interesting challenge to stellar evolution and pulsation theories, and a more detailed study of this system using additional data sets should yield deeper insight about the physics of stellar evolution of Cepheid variables. Future analysis of the system using additional near-infrared photometry might also lead to a better understanding of the systematic uncertainties in current Baade-Wesselink techniques of distance determinations to Cepheid variables.

  4. New Baade-Wesselink distances and radii for four metal-rich Galactic Cepheids

    NARCIS (Netherlands)

    Pedicelli, S.; Lemasle, B.; Groenewegen, M.; Romaniello, M.; Bono, G.; Laney, C. D.; Francois, P.; Buonanno, R.; Caputo, F.; Lub, J.; Pel, J. W.; Primas, F.; Pritchard, J.

    2010-01-01

    Aims. We provide accurate estimates of distances, radii, and iron abundances of four metal-rich Cepheids, namely V340 Ara, UZ Sct, AV Sgr, and VY Sgr. The main aim of this investigation is to constrain their pulsation properties and their location across the Galactic inner disk. Methods. We adopted

  5. The Cepheid galactic internet

    Science.gov (United States)

    Learned, John G.; Kudritzki, R.-P.; Pakvasa, Sandip; Zee, A.

    2012-03-01

    We propose that a sufficiently advanced civilisation may employ Cepheid variable stars as beacons to transmit all-call information throughout the galaxy and beyond. They might employ a pulsed neutrino beam to trigger the expansion of a Cepheid at an earlier than normal time, generating a binary signature of normal period or artificially shortened period. One can construct many scenarios wherein it would be desirable for such a civilisation of star ticklers to transmit data to anyone else within viewing range. The beauty of employing Cepheids is that these stars can be seen from afar (we monitor them out through the Virgo cluster), and any developing technological society would seem to be likely to closely observe them as distance markers. Records exist of Cepheids for well over 100 years. We propose that these (and other regularly variable types of stars) be searched for signs of phase modulation (in the regime of short pulse duration) and patterns, which could be indicative of intentional signalling.

  6. CoRoT space photometry of seven Cepheids

    CERN Document Server

    Poretti, Ennio; Rainer, Monica; Baglin, Annie; Benko, Jozsef; Debosscher, Jonas; Weiss, Werner W

    2015-01-01

    A few Galactic classical Cepheids were observed in the programmes of space missions as Coriolis, MOST and Kepler. An appealing opportunity was to detect additional nonradial modes, thus opening the possibility to perform asteroseismic studies and making the pulsational content of Galactic Cepheids more similar to that of Magellanic Clouds ones. However, only hints of cycle-to-cycle variations were found, without any strict periodicity. In this context the potential of the CoRoT exoplanetary data base was not fully exploited despite the wide area covered on the Galactic plane. Therefore, we investigated all the candidate Cepheids pointed out by the automatic classification of the CoRoT curves. At the end we could identify seven bona-fide Cepheids. The light curves were investigated to remove some instrumental effects. The frequency analysis was particularly delicate since these small effects can be enhanced by the large amplitude, resulting in the presence of significant, but spurious, peaks in the power spect...

  7. The period change of the Cepheid Polaris suggests enhanced mass los

    CERN Document Server

    Neilson, Hilding R; Guinan, Ed; Langer, Norbert; Wasatonic, Richard P; Williams, David B

    2012-01-01

    Polaris is one of the most observed stars in the night sky, with recorded observations spanning more than 200 years. From these observations, one can study the real-time evolution of Polaris via the secular rate of change of the pulsation period. However, the measurements of the rate of period change do not agree with predictions from state-of-the-art stellar evolution models. We show that this may imply that Polaris is currently losing mass at a rate of $\\dot{M} \\approx 10^{-6} M_\\odot$ yr$^{-1}$ based on the difference between modeled and observed rates of period change, consistent with pulsation-enhanced Cepheid mass loss. A relation between the rate of period change and mass loss has important implications for understanding stellar evolution and pulsation, and provides insight into the current Cepheid mass discrepancy.

  8. The Secret Lives of Cepheids: Searching for Evolutionary Changes Using Photoelectric Photometry

    Science.gov (United States)

    Toce, Michael; Guinan, Edward F.; Engle, Scott G.; Wasatonic, Richard P.

    2016-01-01

    Classical Cepheids are pulsating, yellow supergiants and one of the most important classes of variable stars. They have a direct linear relationship between their period and luminosity and thus serve as crucial "standard candles" for determining the cosmic distance scale and measuring the Hubble Constant. Also, Cepheids play a fundamental role in the calibration of Type Ia supernovae, indicating that the expansion of the Universe is accelerating, and also infer the existence of dark energy. Studies of changes in their pulsation periods and amplitudes reveal evolutionary changes too subtle to detect directly, and understanding these various characteristics of Cepheids is critical to their use as high-precision standard candles. To this end, the Villanova Secret Lives of Cepheids (SLiC) program was created as a comprehensive study of Cepheid behavior, evolution, pulsations, atmospheres, heating dynamics, shocks and winds. As part of the SLiC program, ground-based photometry is being carried out of small sample of bright Cepheids. The observations are being made using the 14-inch reflector telescope at Villanova Campus Observatory. Mounted on the telescope is a SBIG photoelectric photometer equipped with standard Johnson UBVRI filters. Photometry is being carried out of the following stars along with their spectral type, period, and visual mag: X Cyg (F7Ib, ~16.39d, 6.47mag), DT Cyg (F7.5Ib, ~2.5d, 5.82mag), S Sge (G5Ibv, ~8.38d, 5.36mag), FF Aql (F6Ib, ~4.47d, 5.38mag), Eta Aql (F6Iab, ~7.18d,3.80mag), and Delta Cep (F5Iab, ~5.37d, 3.75mag). The primary scientific objectives are to obtain light curves to investigate possible evolutionary changes from small variations in luminosity, light amplitude and pulsation period. Special emphasis was placed on the classical Cepheid X Cyg due to recent changes in pulsation period, shown by Szabados via a phase jump in X Cyg's O-C (observed - calculated). X Cyg holds priority in our observations as we attempt to affirm or deny

  9. Pulsating stars

    CERN Document Server

    Catelan, M?rcio

    2014-01-01

    The most recent and comprehensive book on pulsating stars which ties the observations to our present understanding of stellar pulsation and evolution theory.  Written by experienced researchers and authors in the field, this book includes the latest observational results and is valuable reading for astronomers, graduate students, nuclear physicists and high energy physicists.

  10. The angular diameter and distance of the Cepheid Zeta Geminorum

    CERN Document Server

    Kervella, P; Perrin, G; Schöller, M; Traub, W A; Lacasse, M D

    2001-01-01

    Cepheids are the primary distance indicators for extragalactic astronomy and therefore are of very high astrophysical interest. Unfortunately, they are rare stars, situated very far from Earth.Though they are supergiants, their typical angular diameter is only a few milliarcseconds, making them very challenging targets even for long-baseline interferometers. We report observations that were obtained in the K prime band (2-2.3 microns), on the Cepheid Zeta Geminorum with the FLUOR beam combiner, installed at the IOTA interferometer. The mean uniform disk angular diameter was measured to be 1.64 +0.14 -0.16 mas. Pulsational variations are not detected at a significant statistical level, but future observations with longer baselines should allow a much better estimation of their amplitude. The distance to Zeta Gem is evaluated using Baade-Wesselink diameter determinations, giving a distance of 502 +/- 88 pc.

  11. VizieR Online Data Catalog: BVI photometry of OGLE LMC Cepheids (Udalski+, 1999)

    Science.gov (United States)

    Udalski, A.; Soszynski, I.; Szymanski, M.; Kubiak, M.; Pietrzynski, G.; Wozniak, P.; Zebrun, K.

    2000-01-01

    We present the Catalog of Cepheids from the LMC. The Catalog contains 1333 objects detected in the 4.5 square degree area of central parts of the LMC. About 3.4*105 BVI measurements of these stars were collected during the OGLE-II microlensing survey. The Catalog data include period, BVI photometry, astrometry, and R21, phi21 parameters of the Fourier decomposition of I-band light curve. The vast majority of objects from the Catalog are the classical Cepheids pulsating in the fundamental or first overtone mode. The remaining objects include Population II Cepheids and red giants with pulsation-like light curves. Tests of completeness performed in overlapping parts of adjacent fields indicate that completeness of the Catalog is very high: >96%. Statistics and distributions of basic parameters of Cepheids are also presented. Finally, we show the light curves of three eclipsing systems containing Cepheid detected among objects of the Catalog. All presented data, including individual BVI observations are available from the OGLE Internet archive at URL: ftp://sirius.astrouw.edu.pl/ogle/ogle2/var_stars/lmc/cep/catalog/ (3 data files).

  12. The Baade-Becker-Wesselink technique and the fundamental astrophysical parameters of Cepheids

    CERN Document Server

    Rastorguev, Alexey S; Zabolotskikh, Marina V; Berdnikov, Leonid N; Gorynya, Natalia A

    2012-01-01

    The BBW method remains one of most demanded tool to derive full set of Cepheid astrophysical parameters. Surface brightness version of the BBW technique was preferentially used during last decades to calculate Cepheid radii and to improve PLC relations. Its implementation requires a priory knowledge of Cepheid reddening value. We propose a new version of the Baade--Becker--Wesselink technique, which allows one to independently determine the colour excess and the intrinsic colour of a radially pulsating star, in addition to its radius, luminosity, and distance. It is considered to be a generalization of the Balona light curve modelling approach. The method also allows the function F(CI_0) = BC + 10 log Teff for the class of pulsating stars considered to be calibrated. We apply this technique to a number of classical Cepheids with very accurate light and radial-velocity curves. The new technique can also be applied to other pulsating variables, e.g. RR Lyraes. We discuss also possible dependence of the projecti...

  13. V470 Cas and GSC 2901-00089, Two New Double-mode Cepheids

    CERN Document Server

    Khruslov, A V

    2016-01-01

    We present a photometric study of two new double-mode Cepheids, pulsating in the first and second overtones modes: V470 Cas and GSC 2901-00089. For the search of the double-mode variability, we used all available observations from the ROTSE-I/NSVS and SuperWASP online public archives. Our multicolour CCD observations in the B, V and R bands in Johnson's system confirm the double periodicity of these variables. We study period variations of the two stars; variations of the first overtone periods were reliably detected. In addition, we consider the Petersen diagram for the Galactic 1O/2O Cepheids.

  14. Dwarf Cepheids in the Carina Dwarf Spheroidal Galaxy

    CERN Document Server

    Mateo, M; Nemec, J; Mateo, Mario; Hurley-Keller, Denise; Nemec, James

    1998-01-01

    We have discovered 20 dwarf Cepheids (DC) in the Carina dSph galaxy from the analysis of individual CCD images obtained for a deep photometric study of the system. These short-period pulsating variable stars are by far the most distant (~100 kpc) and faintest (V ~ 23.0) DCs known. The Carina DCs obey a well-defined period-luminosity relation, allowing us to readily distinguish between overtone and fundamental pulsators in nearly every case. Unlike RR Lyr stars, the pulsation mode turns out to be uncorrelated with light-curve shape, nor do the overtone pulsators tend towards shorter periods compared to the fundamental pulsators. Using the period-luminosity (PL) relations from Nemec et al. (1994 AJ, 108, 222) and McNamara (1995, AJ, 109, 1751), we derive (m-M)_0 = 20.06 +/- 0.12, for E(B-V) = 0.025 and [Fe/H] = -2.0, in good agreement with recent, independent estimates of the distance/reddening of Carina. The error reflects the uncertainties in the DC distance scale, and in the metallicity and reddening of Cari...

  15. X-Ray, UV and Optical Observations of Classical Cepheids: New Insights into Cepheid Evolution, and the Heating and Dynamics of Their Atmospheres

    CERN Document Server

    Engle, Scott G; 10.5140/JASS.2012.29.2.181

    2012-01-01

    To broaden the understanding of classical Cepheid structure, evolution and atmospheres, we have extended our continuing secret lives of Cepheids program by obtaining XMM/Chandra X-ray observations, and Hubble space telescope (HST) / cosmic origins spectrograph (COS) FUV-UV spectra of the bright, nearby Cepheids Polaris, {\\delta} Cep and {\\beta} Dor. Previous studies made with the international ultraviolet explorer (IUE) showed a limited number of UV emission lines in Cepheids. The well-known problem presented by scattered light contamination in IUE spectra for bright stars, along with the excellent sensitivity & resolution combination offered by HST/COS, motivated this study, and the spectra obtained were much more rich and complex than we had ever anticipated. Numerous emission lines, indicating 10^4 K up to ~3 x 10^5 K plasmas, have been observed, showing Cepheids to have complex, dynamic outer atmospheres that also vary with the photospheric pulsation period. The FUV line emissions peak in the phase ra...

  16. Clustered Cepheid Variables 90 kiloparsec from the Galactic Center

    CERN Document Server

    Chakrabarti, Sukanya; Quillen, Alice; Gran, Felipe; Klein, Christopher; Blitz, Leo

    2015-01-01

    Distant regions close to the plane of our Galaxy are largely unexplored by optical surveys as they are hidden by dust. We have used near-infrared data (that minimizes dust obscuration) from the ESO Public survey VISTA Variables of the Via Lactea (VVV) (Minniti et al. 2011; Saito et al. 2012; henceforth S12) to search for distant stars at low latitudes. We have discovered four Cepheid variables within an angular extent of one degree centered at Galactic longitude of $l = -27.4^\\circ$ and Galactic latitude of $b = -1.08 ^\\circ$. We use the tightly constrained period-luminosity relationship that these pulsating stars obey (Persson et al. 2004; Matsunaga et al. 2011) to derive distances. We infer an average distance to these Cepheid variables of 90 kpc. The Cepheid variables are highly clustered in angle (within one degree) and in distance (the standard deviation of the distances is 12 kpc). They are at an average distance of $\\sim 2~\\rm kpc$ from the plane and their maximum projected separation is $\\sim 1~ \\rm k...

  17. Quantitative results of stellar evolution and pulsation theories.

    Science.gov (United States)

    Fricke, K.; Stobie, R. S.; Strittmatter, P. A.

    1971-01-01

    The discrepancy between the masses of Cepheid variables deduced from evolution theory and pulsation theory is examined. The effect of input physics on evolutionary tracks is first discussed; in particular, changes in the opacity are considered. The sensitivity of pulsation masses to opacity changes and to the ascribed values of luminosity and effective temperature are then analyzed. The Cepheid mass discrepancy is discussed in the light of the results already obtained. Other astronomical evidence, including the mass-luminosity relation for main sequence stars, the solar neutrino flux, and cluster ages are also considered in an attempt to determine the most likely source of error in the event that substantial mass loss has not occurred.

  18. The Secret XUV Lives of Cepheids: FUV/X-ray Observations of Polaris and beta Dor

    CERN Document Server

    Engle, Scott G; DePasquale, Joseph; Evans, Nancy

    2009-01-01

    We report on the surprising recent discovery of strong FUV emissions in two bright, nearby Classical Cepheids from analyses of FUSE archival observations and one of our own approved observations just prior to the failure of the satellite. Polaris and beta Dor are currently the only two Cepheids to have been observed with FUSE, and beta Dor is the only one to have multiple spectra. Both Cepheids show strong C III (977A, 1176A) and O VI (1032A, 1038A) emissions, indicative of 50,000-500,000 K plasma, well above the photospheric temperatures of the stars. More remarkably, beta Dor displays variability in the FUV emission strengths which appears to be correlated to its 9.84-d pulsation period. This phenomenon has never before been observed in Cepheids. The FUV studies are presented along with our recent Chandra/XMM X-ray observations of Polaris and beta Dor, in which X-ray detections were found for both stars (as well as for the prototype Classical Cepheid, delta Cep). Further X-ray observations have been propose...

  19. The ACS LCID Project. VIII. The short-period Cepheids of Leo A

    CERN Document Server

    Bernard, Edouard J; Gallart, Carme; Fiorentino, Giuliana; Cassisi, Santi; Aparicio, Antonio; Cole, Andrew A; Drozdovsky, Igor; Hidalgo, Sebastian L; Skillman, Evan D; Stetson, Peter B; Tolstoy, Eline

    2013-01-01

    We present the results of a new search for variable stars in the Local Group dwarf galaxy Leo A, based on deep photometry from the Advanced Camera for Surveys onboard the Hubble Space Telescope. We detected 166 bona fide variables in our field, of which about 60 percent are new discoveries, and 33 candidate variables. Of the confirmed variables, we found 156 Cepheids, but only 10 RR Lyrae stars despite nearly 100 percent completeness at the magnitude of the horizontal branch. The RR Lyrae stars include 7 fundamental and 3 first-overtone pulsators, with mean periods of 0.636 and 0.366 day, respectively. From their position on the period-luminosity (PL) diagram and light-curve morphology, we classify 91, 58, and 4 Cepheids as fundamental, first-overtone, and second-overtone mode Classical Cepheids (CC), respectively, and two as population II Cepheids. However, due to the low metallicity of Leo A, about 90 percent of the detected Cepheids have periods shorter than 1.5 days. Comparison with theoretical models ind...

  20. Nonlinear simulations of the convection-pulsation coupling

    OpenAIRE

    Gastine, T.; Dintrans, B.

    2011-01-01

    In cold Cepheids close to the red edge of the classical instability strip, a strong coupling between the stellar pulsations and the surface convective motions occurs. This coupling is by now poorly described by 1-D models of convection, the so-called "time-dependent convection models" (TDC). The intrinsic weakness of such models comes from the large number of unconstrained free parameters entering in the description of turbulent convection. A way to overcome these limits is to compute two-dim...

  1. Type II Cepheids as Extragalactic Distance Candles

    OpenAIRE

    Majaess, Daniel J.; Turner, David G.; Lane, David J.

    2009-01-01

    Extragalactic Type II Cepheids are tentatively identified in photometric surveys of IC 1613, M33, M101, M106, M31, NGC 4603, and the SMC. Preliminary results suggest that Type II Cepheids may play an important role as standard candles, in constraining the effects of metallicity on Cepheid parameters, and in mapping extinction.

  2. On the distance of the Magellanic Clouds using Cepheid NIR and optical-NIR Period Wesenheit Relations

    CERN Document Server

    Inno, L; Bono, G; Caputo, F; Buonanno, R; Genovali, K; Laney, C D; Marconi, M; Piersimoni, A M; Primas, F; Romaniello, M

    2012-01-01

    We present the largest near-infrared (NIR) data sets, $JHKs$, ever collected for classical Cepheids in the Magellanic Clouds (MCs). We selected fundamental (FU) and first overtone (FO) pulsators, and found 4150 (2571 FU, 1579 FO) Cepheids for Small Magellanic Cloud (SMC) and 3042 (1840 FU, 1202 FO) for Large Magellanic Cloud (LMC). Current sample is 2--3 times larger than any sample used in previous investigations with NIR photometry. We also discuss optical $VI$ photometry from OGLE-III. NIR and optical--NIR Period-Wesenheit (PW) relations are linear over the entire period range ($0.0<\\log P_{\\rm FU} \\le1.65 $) and their slopes are, within the intrinsic dispersions, common between the MCs. These are consistent with recent results from pulsation models and observations suggesting that the PW relations are minimally affected by the metal content. The new FU and FO PW relations were calibrated using a sample of Galactic Cepheids with distances based on trigonometric parallaxes and Cepheid pulsation models. B...

  3. On the effect of rotation on populations of classical Cepheids I. Predictions at solar metallicity

    CERN Document Server

    Anderson, R I; Georgy, C; Meynet, G; Mowlavi, N; Eyer, L

    2014-01-01

    [Abridged] We aim to improve the understanding of Cepheids from an evolutionary perspective and establish the role of rotation in the Cepheid paradigm. In particular, we are interested in the contribution of rotation to the problem of Cepheid masses, and explore testable predictions of quantities that can be confronted with observations. Evolutionary models including a homogeneous and self-consistent treatment of rotation are studied in detail during the crossings of the classical instability strip (IS). The dependence of several parameters on initial rotation is studied. These parameters include mass, luminosity, temperature, lifetimes, equatorial velocity, surface abundances, and rates of period change. Several key results are obtained: i) mass-luminosity (M-L) relations depend on rotation, particularly during the blue loop phase; ii) luminosity increases between crossings of the IS. Hence, Cepheid M-L relations at fixed initial rotation rate depend on crossing number (faster rotation yields greater luminos...

  4. ON THE DISTANCE OF THE MAGELLANIC CLOUDS USING CEPHEID NIR AND OPTICAL-NIR PERIOD-WESENHEIT RELATIONS

    International Nuclear Information System (INIS)

    We present the largest near-infrared (NIR) data sets, JHKs, ever collected for classical Cepheids in the Magellanic Clouds (MCs). We selected fundamental (FU) and first overtone (FO) pulsators, and found 4150 (2571 FU, 1579 FO) Cepheids for Small Magellanic Cloud (SMC) and 3042 (1840 FU, 1202 FO) for Large Magellanic Cloud (LMC). Current sample is 2-3 times larger than any sample used in previous investigations with NIR photometry. We also discuss optical VI photometry from OGLE-III. NIR and optical-NIR Period-Wesenheit (PW) relations are linear over the entire period range (0.0 FU ≤ 1.65) and their slopes are, within the intrinsic dispersions, common between the MCs. These are consistent with recent results from pulsation models and observations suggesting that the PW relations are minimally affected by the metal content. The new FU and FO PW relations were calibrated using a sample of Galactic Cepheids with distances based on trigonometric parallaxes and Cepheid pulsation models. By using FU Cepheids we found a true distance moduli of 18.45 ± 0.02(random) ± 0.10(systematic) mag (LMC) and 18.93 ± 0.02(random) ± 0.10(systematic) mag (SMC). These estimates are the weighted mean over 10 PW relations and the systematic errors account for uncertainties in the zero point and in the reddening law. We found similar distances using FO Cepheids (18.60 ± 0.03(random) ± 0.10(systematic) mag (LMC) and 19.12 ± 0.03(random) ± 0.10(systematic) mag (SMC)). These new MC distances lead to the relative distance, Δμ = 0.48 ± 0.03 mag (FU, log P = 1) and Δμ = 0.52 ± 0.03 mag (FO, log P = 0.5), which agrees quite well with previous estimates based on robust distance indicators.

  5. Stellar Pulsations in Beyond Horndeski Gravity Theories

    CERN Document Server

    Sakstein, Jeremy; Koyama, Kazuya

    2016-01-01

    Theories of gravity in the beyond Horndeski class recover the predictions of general relativity in the solar system whilst admitting novel cosmologies, including late-time de Sitter solutions in the absence of a cosmological constant. Deviations from Newton's law are predicted inside astrophysical bodies, which allow for falsifiable, smoking-gun tests of the theory. In this work we study the pulsations of stars by deriving and solving the wave equation governing linear adiabatic oscillations to find the modified period of pulsation. Using both semi-analytic and numerical models, we perform a preliminary survey of the stellar zoo in an attempt to identify the best candidate objects for testing the theory. Brown dwarfs and Cepheid stars are found to be particularly sensitive objects and we discuss the possibility of using both to test the theory.

  6. The Araucaria Project: the First-overtone Classical Cepheid in the Eclipsing System OGLE-LMC-CEP-2532

    Science.gov (United States)

    Pilecki, Bogumił; Graczyk, Dariusz; Gieren, Wolfgang; Pietrzyński, Grzegorz; Thompson, Ian B.; Smolec, Radosław; Udalski, Andrzej; Soszyński, Igor; Konorski, Piotr; Taormina, Mónica; Gallenne, Alexandre; Minniti, Dante; Catelan, Márcio

    2015-06-01

    We present here the first spectroscopic and photometric analysis of the double-lined eclipsing binary containing the classical, first-overtone (FO) Cepheid OGLE-LMC-CEP-2532 (MACHO 81.8997.87). The system has an orbital period of 800 days and the Cepheid is pulsating with a period of 2.035 days. Using spectroscopic data from three high-class telescopes and photometry from three surveys spanning 7500 days, we are able to derive the dynamical masses for both stars with an accuracy better than 3%. This makes the Cepheid in this system one of a few classical Cepheids with an accurate dynamical mass determination ({{M}1}=3.90+/- 0.10 {{M}⊙ }). The companion is probably slightly less massive (3.82+/- 0.10 {{M}⊙ }), but may have the same mass within errors ({{M}2}/{{M}1}=0.981+/- 0.015). The system has an age of about 185 million years and the Cepheid is in a more advanced evolutionary stage. For the first time precise parameters are derived for both stars in this system. Due to the lack of the secondary eclipse for many years, not much was known about the Cepheid’s companion. In our analysis, we used extra information from the pulsations and the orbital solution from the radial velocity curve. The best model predicts a grazing secondary eclipse shallower than 1 mmag, hence undetectable in the data, about 370 days after the primary eclipse. The dynamical mass obtained here is the most accurate known for a FO Cepheid and will contribute to the solution of the Cepheid mass discrepancy problem. The research is based on observations obtained with the ESO VLT and 3.6 m telescopes for Programmes 092.D-0295(A), 091.D-0393(A), 089.D-0330(A), 088.D-0447(A), 086.D-0103(A), and 085.D-0398(A), and with the Magellan Clay and Warsaw telescopes at Las Campanas Observatory.

  7. VEGA/CHARA interferometric observations of Cepheids. I. A resolved structure around the prototype classical Cepheid delta Cep in the visible spectral range

    CERN Document Server

    Nardetto, N; Mourard, D; Storm, J; Gieren, W; Fouqué, P; Gallenne, A; Graczyk, D; Kervella, P; Neilson, H; Pietrzynski, G; Pilecki, B; Breitfelder, J; Berio, P; Challouf, M; Clausse, J -M; Ligi, R; Mathias, P; Meilland, A; Perraut, K; Poretti, E; Rainer, M; Spang, A; Stee, P; Tallon-Bosc, I; Brummelaar, T ten

    2016-01-01

    The B-W method is used to determine the distance of Cepheids and consists in combining the angular size variations of the star, as derived from infrared surface-brightness relations or interferometry, with its linear size variation, as deduced from visible spectroscopy using the projection factor. While many Cepheids have been intensively observed by infrared beam combiners, only a few have been observed in the visible. This paper is part of a project to observe Cepheids in the visible with interferometry as a counterpart to infrared observations already in hand. Observations of delta Cep itself were secured with the VEGA/CHARA instrument over the full pulsation cycle of the star. These visible interferometric data are consistent in first approximation with a quasi-hydrostatic model of pulsation surrounded by a static circumstellar environment (CSE) with a size of theta_cse=8.9 +/- 3.0 mas and a relative flux contribution of f_cse=0.07+/-0.01. A model of visible nebula (a background source filling the field o...

  8. OXYGEN ABUNDANCES IN CEPHEIDS

    Energy Technology Data Exchange (ETDEWEB)

    Luck, R. E.; Andrievsky, S. M. [Department of Astronomy, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-7215 (United States); Korotin, S. N.; Kovtyukh, V. V., E-mail: luck@fafnir.astr.cwru.edu, E-mail: serkor@skyline.od.ua, E-mail: val@deneb1.odessa.ua, E-mail: scan@deneb1.odessa.ua [Department of Astronomy and Astronomical Observatory, Odessa National University, Isaac Newton Institute of Chile, Odessa Branch, Shevchenko Park, 65014 Odessa (Ukraine)

    2013-07-01

    Oxygen abundances in later-type stars, and intermediate-mass stars in particular, are usually determined from the [O I] line at 630.0 nm, and to a lesser extent, from the O I triplet at 615.7 nm. The near-IR triplets at 777.4 nm and 844.6 nm are strong in these stars and generally do not suffer from severe blending with other species. However, these latter two triplets suffer from strong non-local thermodynamic equilibrium (NLTE) effects and thus see limited use in abundance analyses. In this paper, we derive oxygen abundances in a large sample of Cepheids using the near-IR triplets from an NLTE analysis, and compare those abundances to values derived from a local thermodynamic equilibrium (LTE) analysis of the [O I] 630.0 nm line and the O I 615.7 nm triplet as well as LTE abundances for the 777.4 nm triplet. All of these lines suffer from line strength problems making them sensitive to either measurement complications (weak lines) or to line saturation difficulties (strong lines). Upon this realization, the LTE results for the [O I] lines and the O I 615.7 nm triplet are in adequate agreement with the abundance from the NLTE analysis of the near-IR triplets.

  9. The Secret Lives of Cepheids: The prototype Classical Cepheid δ Cephei is a Pulsed Variable X-ray and FUV Source - Implications for achieving a high precision Hubble Constant (Ho)

    Science.gov (United States)

    Guinan, Edward F.; Engle, Scott G.; Neilson, Hilding; Harper, Graham M.; Remage Evans, Nancy

    2016-06-01

    As part of our “Secret Lives of Cepheids” program, we report that the prototype Classical Cepheid – δ Cep is an X-ray source with pulsation-modulated X-ray & FUV emissions. Recent Chandra X-ray observations, when combined with our previous Chandra & XMM-Newton data, confirm a periodic sharp ~ 5 fold increase in X-ray flux at ~ 0.5φ. The X-ray emission phases with the star's pulsation P = 5.366-d, confirms that the X-ray emissions arise from the Cepheid itself and not from a companion. The X-ray variation is “spike-like” with an Lx (max) ~ 2.1 x1029 erg/s, with plasma temperatures of ~ 2 - 6 MK. The HST-COS FUV fluxes increase ~10-20 times and reach maximum strengths during ~0.88-0.97φ - prior to maximum brightness. The FUV emissions arise from ionized plasmas with T ~10 - 300 x103 K. The FUV emission lines show turbulent broadening near the maximum fluxes. The FUV emissions are best explained by pulsation-induced collisional shocks originating from the star’s pulsating atmosphere. However, the X-ray emissions occur 0.5 - 0.6 φ (~3 days) later than the FUV emission line maxima. Thus, it appears that the X-ray emissions arise further out from the star. We suggests that to produce the observed high temperature X-ray emitting plasmas, that the X-rays most likely arise from pulsation-shock induced turbulent-magnetic heated plasmas. If this behavior is extended to other Cepheids, the presence of pulsation induced X-ray and FUV emissions could play major roles in the dynamics and heating of Cepheid atmospheres and could have consequences affecting the Cepheid Period-Luminosity (P-L) law. For example, the additional energy and shock-heating could produce enhanced mass loss leading to the formation of circumstellar shells. For example, the presence of circumstellar matter could bias the P-L relation if not accounted for. Similar X-ray - UV behavior is indicated by at least one other Cepheid, β Doradus.This research is supported from grants from NASA for the

  10. Emission lines in the long period Cepheid l Carinae

    Science.gov (United States)

    Boehm-Vitense, Erika; Love, Stanley G.

    1991-01-01

    For the Cepheid (l) Carinae with a pulsation period of 35.5 days we have studied the emission line fluxes as a function of pulsational phase in order to find out whether we see chromosphere and transition layer emission or whether we see emission due to an outward moving shock. All emission lines show a steep increase in flux shortly before maximum light suggestive of a shock moving through the surface layers. The large ratio of the C IV to C II line fluxes shows that these are not transition layer lines. During maximum light the large ratio of the C IV to C II line fluxes also suggests that we see emission from a shock with velocities greater than 100 km/sec such that C IV emission can be excited. With such velocities mass outflow appears possible. The variations seen in the Mg II line profiles show that there is an internal absorption over a broad velocity band independent of the pulsational phase. We attribute this absorption to a circumstellar 'shell'. This 'shell' appears to be seen also as spatially extended emission in the O I line at 1300 angstrom, which is probably excited by resonance with Ly beta.

  11. Square root two period ratios in Cepheid and RR Lyrae variable stars

    CERN Document Server

    Hippke, Michael; Zee, A

    2014-01-01

    We document the presence of nine Cepheid and RR Lyrae variable stars with previously unrecognized characteristics. These stars exhibit the statistically unlikely property of a period ratio of main pulsation divided by secondary pulsation (P1/P2) very close to sqrt(2). Other stars of these types have period ratios which show clustering not with a close association with a single remarkable and nonharmonic number. In the way of explanation, we suggest that this indicates a previously unknown resonance of pulsations. Close examination reveals a deviation of multiples of a few times 0.06% for these stars. This deviation seems to be present in discrete steps on the order of about 0.000388(5), indicating the possible presence of a sort of fine structure in this oscillation. Physical explanation of the source of these regularities remains for 3D simulations of variable stars, and we only claim to make note of the regularities which are suggestive of physical principles.

  12. CLASSICAL CEPHEIDS REQUIRE ENHANCED MASS LOSS

    Energy Technology Data Exchange (ETDEWEB)

    Neilson, Hilding R.; Langer, Norbert; Izzard, Robert [Argelander Institute for Astronomy, University of Bonn, Auf dem Huegel 71, D-53121 Bonn (Germany); Engle, Scott G.; Guinan, Ed, E-mail: neilsonh@etsu.edu [Department of Astronomy and Astrophysics, Villanova University, 800 Lancaster Ave. Villanova, PA 19085 (United States)

    2012-11-20

    Measurements of rates of period change of Classical Cepheids probe stellar physics and evolution. Additionally, better understanding of Cepheid structure and evolution provides greater insight into their use as standard candles and tools for measuring the Hubble constant. Our recent study of the period change of the nearest Cepheid, Polaris, suggested that it is undergoing enhanced mass loss when compared to canonical stellar evolution model predictions. In this work, we expand the analysis to rates of period change measured for about 200 Galactic Cepheids and compare them to population synthesis models of Cepheids including convective core overshooting and enhanced mass loss. Rates of period change predicted from stellar evolution models without mass loss do not agree with observed rates, whereas including enhanced mass loss yields predicted rates in better agreement with observations. This is the first evidence that enhanced mass loss as suggested previously for Polaris and {delta} Cephei must be a ubiquitous property of Classical Cepheids.

  13. Period and light-curve fluctuations of the Kepler Cepheid V1154 Cygni

    Science.gov (United States)

    Derekas, A.; Szabó, Gy. M.; Berdnikov, L.; Szabó, R.; Smolec, R.; Kiss, L. L.; Szabados, L.; Chadid, M.; Evans, N. R.; Kinemuchi, K.; Nemec, J. M.; Seader, S. E.; Smith, J. C.; Tenenbaum, P.

    2012-09-01

    We present a detailed period analysis of the bright Cepheid-type variable star V1154 Cygni (V1154 Cyg; V = 9.1 mag, P ≈ 4.9 d) based on almost 600 d of continuous observations by the Kepler space telescope. The data reveal significant cycle-to-cycle fluctuations in the pulsation period, indicating that classical Cepheids may not be as accurate astrophysical clocks as commonly believed: regardless of the specific points used to determine the O - C values, the cycle lengths show a scatter of 0.015-0.02 d over 120 cycles covered by the observations. A very slight correlation between the individual Fourier parameters and the O - C values was found, suggesting that the O - C variations might be due to the instability of the light-curve shape. Random-fluctuation tests revealed a linear trend up to a cycle difference 15, but for long term, the period remains around the mean value. We compare the measurements with simulated light curves that were constructed to mimic V1154 Cyg as a perfect pulsator modulated only by the light travel time effect caused by low-mass companions. We show that the observed period jitter in V1154 Cyg represents a serious limitation in the search for binary companions. While the Kepler data are accurate enough to allow the detection of planetary bodies in close orbits around a Cepheid, the astrophysical noise can easily hide the signal of the light-time effect.

  14. Hybrid Pulsators -- Pulsating Stars with Multiple Identities

    CERN Document Server

    Zhou, A -Y

    2015-01-01

    We have carried out a statistic survey on the pulsating variable stars with multiple identities. These stars were identified to exhibit two types of pulsation or multiple light variability types in the literature, and are usually called hybrid pulsators. We extracted the hybrid information based on the Simbad database. Actually, all the variables with multiple identities are retrieved. The survey covers various pulsating stars across the Hertzsprung-Russell diagram. We aim at giving a clue in selecting interesting targets for further observation. Hybrid pulsators are excellent targets for asteroseismology. An important implication of such stars is their potential in advancing the theories of both stellar evolution and pulsation. By presenting the statistics, we address the open questions and prospects regarding current status of hybrid pulsation studies.

  15. Bayesian Nonparametric Shrinkage Applied to Cepheid Star Oscillations.

    Science.gov (United States)

    Berger, James; Jefferys, William; Müller, Peter

    2012-01-01

    Bayesian nonparametric regression with dependent wavelets has dual shrinkage properties: there is shrinkage through a dependent prior put on functional differences, and shrinkage through the setting of most of the wavelet coefficients to zero through Bayesian variable selection methods. The methodology can deal with unequally spaced data and is efficient because of the existence of fast moves in model space for the MCMC computation. The methodology is illustrated on the problem of modeling the oscillations of Cepheid variable stars; these are a class of pulsating variable stars with the useful property that their periods of variability are strongly correlated with their absolute luminosity. Once this relationship has been calibrated, knowledge of the period gives knowledge of the luminosity. This makes these stars useful as "standard candles" for estimating distances in the universe. PMID:24368873

  16. Binarity among Cepheids in the Magellanic Clouds

    OpenAIRE

    Szabados, László; Nehéz, Dóra

    2012-01-01

    Spectroscopic binarity of the Cepheid variable HV914 in the Large Magellanic Cloud is pointed out from the published radial velocity observational data. The list of known binaries among Cepheid type variable stars in the Magellanic Clouds is published in tabular form. The census indicates a serious deficiency of Cepheids with known companions as compared with their Galactic counterparts, whose implications are also discussed. A particular amplitude ratio (A_{V_{rad}}/A_B) of individual Magell...

  17. Extended envelopes around Galactic Cepheids III. Y Oph and alpha Per from near-infrared interferometry with CHARA/FLUOR

    CERN Document Server

    Mérand, A; Kervella, P; Foresto, V Coudé du; Brummelaar, T ten; McAlister, H

    2007-01-01

    Unbiased angular diameter measurements are required for accurate distances to Cepheids using the interferometric Baade Wesselink method (IBWM). The precision of this technique is currently limited by interferometric measurements at the 1.5% level. At this level, the center-to-limb darkening (CLD) and the presence of circumstellar envelopes (CSE) seem to be the two main sources of bias. The observations we performed aim at improving our knowledge of the interferometric visibility profile of Cepheids. In particular, we assess the systematic presence of CSE around Cepheids in order determine accurate distances with the IBWM free from CSE biased angular diameters. We observed a Cepheid (Y Oph) for which the pulsation is well resolved and a non-pulsating yellow supergiant (alpha Per) using long-baseline near-infrared interferometry. We interpreted these data using a simple CSE model we previously developed. We found that our observations of alpha Per do not provide evidence for a CSE. The measured CLD is explained...

  18. The Araucaria Project: The First-Overtone Classical Cepheid in the Eclipsing System OGLE-LMC-CEP-2532

    CERN Document Server

    Pilecki, B; Gieren, W; Pietrzyński, G; Thompson, I B; Smolec, R; Udalski, A; Soszyński, I; Konorski, P; Taormina, M; Gallenne, A; Minniti, D; Catelan, M

    2015-01-01

    We present here the first spectroscopic and photometric analysis of the double-lined eclipsing binary containing the classical, first-overtone Cepheid OGLE-LMC-CEP-2532 (MACHO 81.8997.87). The system has an orbital period of 800 days and the Cepheid is pulsating with a period of 2.035 days. Using spectroscopic data from three high-class telescopes and photometry from three surveys spanning 7500 days we are able to derive the dynamical masses for both stars with an accuracy better than 3%. This makes the Cepheid in this system one of a few classical Cepheids with an accurate dynamical mass determination (M_1=3.90 +/- 0.10 M_sun). The companion is probably slightly less massive (3.82 +/- 0.10 M_sun), but may have the same mass within errors (M_2/M_1= 0.981 +/- 0.015). The system has an age of about 185 million years and the Cepheid is in a more advanced evolutionary stage. For the first time precise parameters are derived for both stars in this system. Due to the lack of the secondary eclipse for many years not...

  19. Investigating Cepheid $\\ell$ Carinae's Cycle-to-cycle Variations via Contemporaneous Velocimetry and Interferometry

    CERN Document Server

    Anderson, R I; Kervella, P; Breitfelder, J; LeBouquin, J -B; Eyer, L; Gallenne, A; Palaversa, L; Semaan, T; Saesen, S; Mowlavi, N

    2015-01-01

    Baade-Wesselink-type (BW) techniques enable geometric distance measurements of Cepheid variable stars in the Galaxy and the Magellanic clouds. The leading uncertainties involved concern projection factors required to translate observed radial velocities (RVs) to pulsational velocities and recently discovered modulated variability. We carried out an unprecedented observational campaign involving long-baseline interferometry (VLTI/PIONIER) and spectroscopy (Euler/Coralie) to search for modulated variability in the long-period (P $\\sim$ 35.5 d) Cepheid Carinae. We determine highly precise angular diameters from squared visibilities and investigate possible differences between two consecutive maximal diameters, $\\Delta_{\\rm{max}} \\Theta$. We characterize the modulated variability along the line-of-sight using 360 high-precision RVs. Here we report tentative evidence for modulated angular variability and confirm cycle-to-cycle differences of $\\ell$ Carinae's RV variability. Two successive maxima yield $\\Delta_{\\rm...

  20. Period Changes in Galactic Classical Cepheids. Slow Evolution of Long-period Cepheids

    CERN Document Server

    Pietrukowicz, P

    2003-01-01

    We compared period changes derived from O-C diagrams for 63 classical Cepheids from our Galaxy with model calculations. We found that for Cepheids with log P > 1.0 the observed changes are smaller than predicted values, except variable SZ Cas. However some of the first overtone Cepheids, particularly EU Tau and Polaris, change its period much faster than it follows from theory. Summary of the known data on the period changes in Cepheids from the Galaxy and from the Magellanic Clouds (previous papers) leads to conclusion that none of the 999 Cepheid is undergoing the first crossing of the instability strip. Also the observed period changes for long-period Cepheids are a few times slower than predicted by the models. These results imply that much larger fraction of helium is burnt in the Cepheid stage than it is predicted by models.

  1. The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. VII. Classical Cepheids in the Small Magellanic Cloud

    CERN Document Server

    Soszynski, I; Udalski, A; Szymanski, M K; Kubiak, M; Pietrzynski, G; Wyrzykowski, L; Szewczyk, O; Ulaczyk, K

    2010-01-01

    The seventh part of the OGLE-III Catalog of Variable Stars (OIII-CVS) consists of 4630 classical Cepheids in the Small Magellanic Cloud (SMC). The sample includes 2626 fundamental-mode (F), 1644 first-overtone (1O), 83 second-overtone (2O), 59 double-mode F/1O, 215 double-mode 1O/2O, and 3 triple-mode classical Cepheids. For each object basic parameters, multi-epoch VI photometry collected within 8 or 13 years of observations, and finding charts are provided in the OGLE Internet archive. We present objects of particular interest: exceptionally numerous sample of single-mode second-overtone pulsators, five double Cepheids, two Cepheids with eclipsing variations superimposed on the pulsation light curves. At least 139 first-overtone Cepheids exhibit low-amplitude secondary variations with periods in the range 0.60-0.65 of the primary ones. These stars populate three distinct sequences in the Petersen diagram. The origin of this secondary modulation is still unknown. Contrary to the Large Magellanic Cloud (LMC) ...

  2. Classical Cepheids Require Enhanced Mass Loss

    CERN Document Server

    Neilson, Hilding R; Engle, Scott G; Guinan, Ed; Izzard, Robert

    2012-01-01

    Measurements of rates of period change of Classical Cepheids probe stellar physics and evolution. Additionally, better understanding of Cepheid structure and evolution provides greater insight into their use as standard candles and tools for measuring the Hubble constant. Our recent study of the period change of the nearest Cepheid, Polaris, suggested that it is undergoing enhanced mass loss when compared to canonical stellar evolution model predictions. In this work, we expand the analysis to rates of period change measured for about 200 Galactic Cepheids and compare them to population synthesis models of Cepheids including convective core overshooting and enhanced mass loss. Rates of period change predicted from stellar evolution models without mass loss do not agree with observed rates whereas including enhanced mass loss yields predicted rates in better agreement with observations. This is the first evidence that enhanced mass loss as suggested previously for Polaris and delta Cephei must be a ubiquitous ...

  3. Survey of non-linear hydrodynamic models of type-II Cepheids

    Science.gov (United States)

    Smolec, R.

    2016-03-01

    We present a grid of non-linear convective type-II Cepheid models. The dense model grids are computed for 0.6 M⊙ and a range of metallicities ([Fe/H] = -2.0, -1.5, -1.0), and for 0.8 M⊙ ([Fe/H] = -1.5). Two sets of convective parameters are considered. The models cover the full temperature extent of the classical instability strip, but are limited in luminosity; for the most luminous models, violent pulsation leads to the decoupling of the outermost model shell. Hence, our survey reaches only the shortest period RV Tau domain. In the Hertzsprung-Russell diagram, we detect two domains in which period-doubled pulsation is possible. The first extends through the BL Her domain and low-luminosity W Vir domain (pulsation periods ˜2-6.5 d). The second domain extends at higher luminosities (W Vir domain; periods >9.5 d). Some models within these domains display period-4 pulsation. We also detect very narrow domains (˜10 K wide) in which modulation of pulsation is possible. Another interesting phenomenon we detect is double-mode pulsation in the fundamental mode and in the fourth radial overtone. Fourth overtone is a surface mode, trapped in the outer model layers. Single-mode pulsation in the fourth overtone is also possible on the hot side of the classical instability strip. The origin of the above phenomena is discussed. In particular, the role of resonances in driving different pulsation dynamics as well as in shaping the morphology of the radius variation curves is analysed.

  4. The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. XIV. Classical and Type II Cepheids in the Galactic Bulge

    CERN Document Server

    Soszynski, I; Pietrukowicz, P; Szymanski, M K; Kubiak, M; Pietrzynski, G; Wyrzykowski, L; Ulaczyk, K; Poleski, R; Kozlowski, S

    2011-01-01

    The fourteenth part of the OGLE-III Catalog of Variable Stars (OIII-CVS) contains Cepheid variables detected in the OGLE-II and OGLE-III fields toward the Galactic bulge. The catalog is divided into two main categories: 32 classical Cepheids (21 single-mode fundamental-mode F, four first-overtone 1O, two double-mode F/1O, three double-mode 1O/2O and two triple-mode 1O/2O/3O pulsators) and 335 type II Cepheids (156 BL Her, 128 W Vir and 51 RV Tau stars). Six of the type II Cepheids likely belong to the Sagittarius Dwarf Spheroidal Galaxy. The catalog data include the time-series photometry collected in the course of the OGLE survey, observational parameters of the stars, finding charts, and cross-identifications with the General Catalogue of Variable Stars. We discuss some statistical properties of the sample and compare it with the OGLE catalogs of Cepheids in the Large and Small Magellanic Clouds. Multi-mode classical Cepheids in the Galactic bulge show systematically smaller period ratios than their counter...

  5. Survey of non-linear hydrodynamic models of type-II Cepheids

    CERN Document Server

    Smolec, R

    2015-01-01

    We present a grid on non-linear convective type-II Cepheid models. The dense model grids are computed for 0.6M_Sun and a range of metallicities ([Fe/H]=-2.0,-1.5,-1.0), and for 0.8M_Sun ([Fe/H]=-1.5). Two sets of convective parameters are considered. The models cover the full temperature extent of the classical instability strip, but are limited in luminosity; for the most luminous models violent pulsation leads to the decoupling of the outermost model shell. Hence, our survey reaches only the shortest period RV Tau domain. In the Hertzsprung-Russel diagram we detect two domains in which period doubled pulsation is possible. The first extends through the BL Her domain and low luminosity W Vir domain (pulsation periods ~2-6.5 d). The second domain extends at higher luminosities (W Vir domain; periods >9.5d). Some models within these domains display period-4 pulsation. We also detect very narrow domains (~10 K wide) in which modulation of pulsation is possible. Another interesting phenomenon we detect is double...

  6. Effective temperature and radial velocity of the small-amplitude Cepheid Polaris (alpha UMi) in 2015

    CERN Document Server

    Usenko, I A; Miroshnichenko, A S; Danford, S

    2016-01-01

    We present the results of an analysis of 21 spectra of alpha UMi (Polaris) obtained in September - December 2015. Frequency analysis shows an increase of the pulsation period up to 8.6 min in comparison to the 2007 observational set. The radial velocity amplitude comes to 4.16 km s^-1, and it approximately twice the one found in 2007. The average Teff = 6017 K, and it is close to the value determined for the 2001-2004 set. Therefore Polaris moves to the red edge of the Cepheid instability strip (CIS)

  7. VEGA/CHARA interferometric observations of Cepheids. I. A resolved structure around the prototype classical Cepheid δ Cep in the visible spectral range

    Science.gov (United States)

    Nardetto, N.; Mérand, A.; Mourard, D.; Storm, J.; Gieren, W.; Fouqué, P.; Gallenne, A.; Graczyk, D.; Kervella, P.; Neilson, H.; Pietrzynski, G.; Pilecki, B.; Breitfelder, J.; Berio, P.; Challouf, M.; Clausse, J.-M.; Ligi, R.; Mathias, P.; Meilland, A.; Perraut, K.; Poretti, E.; Rainer, M.; Spang, A.; Stee, P.; Tallon-Bosc, I.; ten Brummelaar, T.

    2016-09-01

    Context. The B-W method is used to determine the distance of Cepheids and consists in combining the angular size variations of the star, as derived from infrared surface-brightness relations or interferometry, with its linear size variation, as deduced from visible spectroscopy using the projection factor. The underlying assumption is that the photospheres probed in the infrared and in the visible are located at the same layer in the star whatever the pulsation phase. While many Cepheids have been intensively observed by infrared beam combiners, only a few have been observed in the visible. Aims: This paper is part of a project to observe Cepheids in the visible with interferometry as a counterpart to infrared observations already in hand. Methods: Observations of δ Cep itself were secured with the VEGA/CHARA instrument over the full pulsation cycle of the star. Results: These visible interferometric data are consistent in first approximation with a quasi-hydrostatic model of pulsation surrounded by a static circumstellar environment (CSE) with a size of θCSE = 8.9 ± 3.0 mas and a relative flux contribution of fCSE = 0.07 ± 0.01. A model of visible nebula (a background source filling the field of view of the interferometer) with the same relative flux contribution is also consistent with our data at small spatial frequencies. However, in both cases, we find discrepancies in the squared visibilities at high spatial frequencies (maximum 2σ) with two different regimes over the pulsation cycle of the star, φ = 0.0 - 0.8 and φ = 0.8-1.0. We provide several hypotheses to explain these discrepancies, but more observations and theoretical investigations are necessary before a firm conclusion can be drawn. Conclusions: For the first time we have been able to detect in the visible domain a resolved structure around δ Cep. We have also shown that a simple model cannot explain the observations, and more work will be necessary in the future, both on observations and

  8. Welcome back, Polaris the Cepheid

    CERN Document Server

    Bruntt, H; Stello, D; Evans, N R; Eaton, J A

    2008-01-01

    For about 100 years the amplitude of the 4-day pulsation in Polaris has decreased. We present new results showing a significant increase in the amplitude based on 4.5 years of continuous monitoring from the ground and with two satellite missions.

  9. The OGLE Collection of Variable Stars. Anomalous Cepheids in the Magellanic Clouds

    CERN Document Server

    Soszynski, I; Szymanski, M K; Pietrzynski, G; Wyrzykowski, L; Ulaczyk, K; Poleski, R; Pietrukowicz, P; Kozlowski, S; Skowron, J; Skowron, D; Mroz, P; Pawlak, M

    2015-01-01

    We present a collection of 250 anomalous Cepheids (ACs) discovered in the OGLE-IV fields toward the Large (LMC) and Small Magellanic Cloud (SMC). The LMC sample is an extension of the OGLE-III Catalog of ACs published in 2008, while the SMC sample contains the first known bona fide ACs in this galaxy. The total sample is composed of 141 ACs in the LMC and 109 ACs in the SMC. All these stars pulsate in single modes: fundamental (174 objects) or first overtone (76 objects). Additionally, we report the discovery of four ACs located in the foreground of the Magellanic Clouds. These are the first fundamental-mode ACs known in the Galactic field. We demonstrate that the coefficients phi_21 and phi_31 determined by the Fourier light curve decomposition are useful discriminators between classical Cepheids and ACs, at least in the LMC and in the field of the Milky Way. In the SMC, the light curve shapes and mean magnitudes of short-period classical Cepheids make them similar to ACs, which is a source of difficulties i...

  10. NO EVIDENCE FOR CLASSICAL CEPHEIDS AND A NEW DWARF GALAXY BEHIND THE GALACTIC DISK

    Energy Technology Data Exchange (ETDEWEB)

    Pietrukowicz, P.; Udalski, A.; Szymański, M. K.; Soszyński, I.; Pietrzyński, G.; Wyrzykowski, Ł.; Poleski, R.; Ulaczyk, K.; Skowron, J.; Mróz, P.; Pawlak, M.; Kozłowski, S. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland)

    2015-11-10

    Based on data from the ongoing OGLE Galaxy Variability Survey (OGLE GVS), we have verified observed properties of stars detected by the near-infrared VVV survey in a direction near the Galactic plane at longitude l ≈ −27° and recently tentatively classified as classical Cepheids belonging to, hence claimed, a dwarf galaxy at a distance of about 90 kpc from the Galactic Center. Three of four stars are detected in the OGLE GVS I-band images. We show that two of the objects are not variable at all, and the third one with a period of 5.695 days and a nearly sinusoidal light curve of an amplitude of 0.5 mag cannot be a classical Cepheid and is very likely a spotted object. These results together with a very unusual shape of the K{sub s}-band light curve of the fourth star indicate that it is very likely that none of them is a Cepheid and, thus there is no evidence for a background dwarf galaxy. Our observations show that great care must be taken when classifying objects by their low-amplitude close-to-sinusoidal near-infrared light curves, especially with a small number of measurements. We also provide a sample of high-amplitude spotted stars with periods of a few days that can mimic pulsations and even eclipses.

  11. Gaia Data Release 1 - The Cepheid & RR Lyrae star pipeline and its application to the south ecliptic pole region

    CERN Document Server

    Clementini, G; Leccia, S; Mowlavi, N; Lecoeur-Taibi, I; Marconi, M; Szabados, L; Eyer, L; Guy, L P; Rimoldini, L; de Fombelle, G Jevardat; Holl, B; Busso, G; Charnas, J; Cuypers, J; De Angeli, F; De Ridder, J; Debosscher, J; Evans, D W; Klagyivik, P; Musella, I; Nienartowicz, K; Ordonez, D; Regibo, S; Riello, M; Sarro, L M; Suveges, M

    2016-01-01

    We present an overview of the Specific Objects Study (SOS) pipeline developed within the Coordination Unit 7 (CU7) of the Gaia Data Processing and Analysis Consortium (DPAC), the coordination unit charged with the processing and analysis of variable sources observed by Gaia, to validate and fully characterise Cepheids and RR Lyrae stars observed by the spacecraft. We describe how the SOS for Cepheids and RR Lyrae stars (SOS Cep&RRL) was specifically tailored to analyse Gaia's G-band photometric time-series with a South Ecliptic Pole (SEP) footprint, which covers an external region of the Large Magellanic Cloud (LMC). G-band time-series photometry and characterization by the SOS Cep&RRL pipeline (mean magnitude and pulsation characteristics) are published in Gaia Data Release 1 (Gaia DR1) for a total sample of 3,194 variable stars, 599 Cepheids and 2,595 RR Lyrae stars, of which 386 (43 Cepheids and 343 RR Lyrae stars) are new discoveries by Gaia. All 3,194 stars are distributed over an area extending ...

  12. Structural properties of s-Cepheid velocity curves. Constraining the location of the omega4=2omega1 resonance

    CERN Document Server

    Kienzle-Focacci, M N; Bersier, D F; Pont, F

    1999-01-01

    The light curves of the first overtone classical Cepheids show a discontinuity in their phi_21 vs. P diagram, near P=3.2 days. This feature, commonly attributed to the 2:1 resonance with the fourth overtone, is not reproduced by the hydrodynamical models. With the goal of reexamining the resonance hypothesis, we have obtained new CORAVEL radial velocity curves for 13 s-Cepheids. Together with 11 objects of Krzyt et al.(1998), the combined sample covers the whole range of s-Cepheid periods. The velocity Fourier parameters display a strong characteristic resonant behavior. In striking contrast to photometric ones, they vary smoothly with the pulsation period and show no jump at 3.2 days. The existing radiative hydrodynamical models match the velocity parameters very well. The center of the omega_4 = 2 omega_1 resonance is estimated to occur at P_r = 4.58+-0.04 days, i.e. at a considerable longer period than previously assumed. We identify two new members of the s-Cepheid group: MY Pup and V440 Per.

  13. The Araucaria Project: A study of the classical Cepheid in the eclipsing binary system OGLE LMC562.05.9009 in the Large Magellanic Cloud

    CERN Document Server

    Gieren, Wolfgang; Pietrzynski, Grzegorz; Graczyk, Dariusz; Udalski, Andrzej; Soszynki, Igor; Thompson, Ian B; Moroni, Pier Giorgio Prada; Smolec, Radoslaw; Konorski, Piotr; Gorski, Marek; Karczmarek, Paulina; Suchomska, Ksenia; Taormina, Monica; Gallenne, Alexandre; Storm, Jesper; Bono, Giuseppe; Catelan, Marcio; Szymanski, Michal; Kozlowski, Szymon; Pietrukowicz, Pawel; Wyrzykowski, Lukasz; Poleski, Radoslaw; Skowron, Jan; Minniti, Dante; Ulaczyk, K; Mroz, P; Pawlak, M; Nardetto, Nicolas

    2015-01-01

    We present a detailed study of the classical Cepheid in the double-lined, highly eccentric eclipsing binary system OGLE-LMC562.05.9009. The Cepheid is a fundamental mode pulsator with a period of 2.988 days. The orbital period of the system is 1550 days. Using spectroscopic data from three 4-8-m telescopes and photometry spanning 22 years, we were able to derive the dynamical masses and radii of both stars with exquisite accuracy. Both stars in the system are very similar in mass, radius and color, but the companion is a stable, non-pulsating star. The Cepheid is slightly more massive and bigger (M_1 = 3.70 +/- 0.03M_sun, R_1 = 28.6 +/- 0.2R_sun) than its companion (M_2 = 3.60 +/- 0.03M_sun, R_2 = 26.6 +/- 0.2R_sun). Within the observational uncertainties both stars have the same effective temperature of 6030 +/- 150K. Evolutionary tracks place both stars inside the classical Cepheid instability strip, but it is likely that future improved temperature estimates will move the stable giant companion just beyond...

  14. The beat Cepheids in the Magellanic Clouds: an analysis from the EROS-2 database

    CERN Document Server

    Marquette, J B; Buchler, J R; Szabó, R; Tisserand, P; Belghith, S; Fouqué, P; Lesquoy, E; Milsztajn, A; Schwarzenberg-Czerny, A; Afonso, C; Albert, J N; Andersen, J; Ansari, R; Aubourg, E; Bareyre, P; Charlot, X; Coutures, C; Ferlet, R; Glicenstein, J F; Goldman, B; Gould, A; Graff, D; Gros, M; Haïssinski, J; Hamadache, C; De Kat, J; Guillou, L Le; Loup, C; Magneville, C; Maurice, E; Maury, A; Moniez, M; Palanque-Delabrouille, Nathalie; Perdereau, O; Rahal, Y R; Rich, J; Spiro, M; Vidal-Madjar, A

    2009-01-01

    A number of microlensing dark-matter surveys have produced tens of millions of light curves of individual background stars. These data provide an unprecedented opportunity for systematic studies of whole classes of variable stars and their host galaxies. We aim to use the EROS-2 survey of the Magellanic Clouds to detect and study the population of beat Cepheids (BCs) in both Clouds. BCs pulsating simultaneously in the first overtone and fundamental modes (FO/F) or in the second and first overtone modes (SO/FO) are of particular interest. Using special software designed to search for periodic variables, we have scanned the EROS-2 data base for variables in the typical period range of Cepheids. Metallicities of FO/F objects were then calculated from linear nonadiabatic convective stellar models. We identify 74 FO/F BCs in the LMC and 41 in the SMC, and 173 and 129 SO/FO pulsators in the LMC and SMC, respectively; 185 of these stars are new discoveries. For nearly all the FO/F objects we determine minimum, mean,...

  15. A long-period Cepheid variable in the starburst cluster VdBH222

    CERN Document Server

    Clark, J S; Lohr, M E; Dorda, R; González-Fernández, C; Lewis, F; Roche, P

    2015-01-01

    Galactic starburst clusters play a twin role in astrophysics, serving as laboratories for the study of stellar physics and also delineating the structure and recent star formation history of the Milky Way. In order to exploit these opportunities we have undertaken a multi-epoch spectroscopic survey of the red supergiant dominated young massive clusters thought to be present at both near and far ends of the Galactic Bar. Significant spectroscopic variability suggestive of radial pulsations was found for the yellow supergiant VdBH 222 #505. Follow-up photometric investigations revealed modulation with a period of ~23.325d; both timescale and pulsational profile are consistent with a Cepheid classification. As a consequence #505 may be recognised as one of the longest period Galactic cluster Cepheids identified to date and hence of considerable use in constraining the bright end of the period/luminosity relation at solar metallicities. In conjunction with extant photometry we infer a distance of ~6kpc for VdBH22...

  16. V1135 Herculis: a double-lined eclipsing binary with an Anomalous Cepheid

    CERN Document Server

    Sipahi, E; Cakirli, O; Dal, H A; Evren, S

    2013-01-01

    BVR light curves and radial velocities for the double-lined eclipsing binary V1135\\,Her were obtained. The brighter component of V1135\\,Her is a Cepheid variable with a pulsation period of 4.22433$\\pm$0.00026 days. The orbital period of the system is about 39.99782$\\pm$0.00233 days, which is the shortest value among the known Type\\,II Cepheid binaries. The observed B, V, and R magnitudes were cleaned for the intrinsic variations of the primary star. The remaining light curves, consisting of eclipses and proximity effects, are obtained. Our analyses of the multi-colour light curves and radial velocities led to the determination of fundamental stellar properties of both components of the interesting system V1135\\,Her. The system consists of two evolved stars, G1+K3 between giants and supergiants, with masses of M$_1$=1.461$\\pm$0.054 \\Msun ~and M$_2$=0.504$\\pm$0.040 {\\Msun} and radii of R$_1$=27.1$\\pm$0.4 {\\Rsun} and R$_2$=10.4$\\pm$0.2 {\\Rsun}. The pulsating star is almost filling its corresponding Roche lobe wh...

  17. Period and light curve fluctuations of the Kepler Cepheid V1154 Cyg

    CERN Document Server

    Derekas, A; Berdnikov, L; Szabo, R; Smolec, R; Kiss, L L; Szabados, L; Chadid, M; Evans, N R; Kinemuchi, K; Nemec, J M; Seader, S E; Smith, J C; Tenenbaum, P

    2012-01-01

    We present a detailed period analysis of the bright Cepheid-type variable star V1154 Cygni (V =9.1 mag, P~4.9 d) based on almost 600 days of continuous observations by the Kepler space telescope. The data reveal significant cycle-to-cycle fluctuations in the pulsation period, indicating that classical Cepheids may not be as accurate astrophysical clocks as commonly believed: regardless of the specific points used to determine the O-C values, the cycle lengths show a scatter of 0.015-0.02 days over the 120 cycles covered by the observations. A very slight correlation between the individual Fourier parameters and the O-C values was found, suggesting that the O - C variations might be due to the instability of the light curve shape. Random fluctuation tests revealed a linear trend up to a cycle difference 15, but for long term, the period remains around the mean value. We compare the measurements with simulated light curves that were constructed to mimic V1154 Cyg as a perfect pulsator modulated only by the ligh...

  18. A search for open cluster Cepheids in the Galactic plane

    CERN Document Server

    Chen, Xiaodian; Deng, Licai

    2014-01-01

    We analyse all potential combinations of Galactic Cepheids and open clusters (OCs) in the most up-to-date catalogues available. Isochrone fitting and proper-motion calcula- tion are applied to all potential OC{Cepheid combinations. Five selection criteria are used to select possible OC Cepheids: (i) the Cepheid of interest must be located within 60 arcmin of the OC's centre; (ii) the Cepheid's proper motion is located within the 1 sigma distribution of that of its host OC; (iii) the Cepheid is located in the instability strip of its postulated host OC; (iv) the Cepheid and OC distance moduli should differ by less than 1 mag; and (v) the Cepheid and OC ages (and, where available, their metal- licities) should be comparable: {\\Delta}log(t yr^-1) < 0.3. Nineteen possible OC Cepheids are found based on our near-infrared (NIR) analysis; eight additional OC{Cepheid associations may be genuine pairs for which we lack NIR data. Six of the Cepheids analysed at NIR wavelengths are new, high-probability OC Cepheids, ...

  19. The VMC Survey - XIII. Type II Cepheids in the Large Magellanic Cloud

    Science.gov (United States)

    Ripepi, V.; Moretti, M. I.; Marconi, M.; Clementini, G.; Cioni, M.-R. L.; de Grijs, R.; Emerson, J. P.; Groenewegen, M. A. T.; Ivanov, V. D.; Muraveva, T.; Piatti, A. E.; Subramanian, S.

    2015-01-01

    The VISTA (Visible and Infrared Survey Telescope for Astronomy) survey of the Magellanic Clouds System (VMC) is collecting deep Ks-band time-series photometry of the pulsating variable stars hosted in the system formed by the two Magellanic Clouds and the Bridge connecting them. In this paper, we have analysed a sample of 130 Large Magellanic Cloud (LMC) Type II Cepheids (T2CEPs) found in tiles with complete or near-complete VMC observations for which identification and optical magnitudes were obtained from the OGLE III (Optical Gravitational Lensing Experiment) survey. We present J and Ks light curves for all 130 pulsators, including 41 BL Her, 62 W Vir (12 pW Vir) and 27 RV Tau variables. We complement our near-infrared photometry with the V magnitudes from the OGLE III survey, allowing us to build a variety of period-luminosity (PL), period-luminosity-colour (PLC) and period-Wesenheit (PW) relationships, including any combination of the V, J, Ks filters and valid for BL Her and W Vir classes. These relationships were calibrated in terms of the LMC distance modulus, while an independent absolute calibration of the PL(Ks) and the PW(Ks, V) was derived on the basis of distances obtained from Hubble Space Telescope parallaxes and Baade-Wesselink technique. When applied to the LMC and to the Galactic globular clusters hosting T2CEPs, these relations seem to show that (1) the two Population II standard candles RR Lyrae and T2CEPs give results in excellent agreement with each other; (2) there is a discrepancy of ˜0.1 mag between Population II standard candles and classical Cepheids when the distances are gauged in a similar way for all the quoted pulsators. However, given the uncertainties, this discrepancy is within the formal 1σ uncertainties.

  20. Alessi 95 and the short period Cepheid SU Cassiopeiae

    CERN Document Server

    Turner, David G; Lane, David J; Balam, David D; Gieren, Wolfgang P; Storm, Jesper; Forbes, Doug W; Havlen, Robert J; Alessi, Bruno

    2012-01-01

    The parameters for the newly-discovered open cluster Alessi 95 are established on the basis of available photometric and spectroscopic data, in conjunction with new observations. Colour excesses for spectroscopically-observed B and A-type stars near SU Cas follow a reddening relation described by E(U-B)/E(B-V)=0.83+0.02*E(B-V), implying a value of R=Av/E(B-V)~2.8 for the associated dust. Alessi 95 has a mean reddening of E(B-V)_(B0)=0.35+-0.02 s.e., an intrinsic distance modulus of Vo-Mv=8.16+-0.04 s.e. (+-0.21 s.d.), d=429+-8 pc, and an estimated age of 10^8.2 yr from ZAMS fitting of available UBV, CCD BV, NOMAD, and 2MASS JHKs observations of cluster stars. SU Cas is a likely cluster member, with an inferred space reddening of E(B-V)=0.33+-0.02 and a luminosity of =-3.15+-0.07 s.e., consistent with overtone pulsation (P_FM=2.75 d), as also implied by the Cepheid's light curve parameters, rate of period increase, and Hipparcos parallaxes for cluster stars. There is excellent agreement of the distance estimat...

  1. Binary Properties from Cepheid Radial Velocities (CRaV)

    CERN Document Server

    Evans, Nancy Remage; Lauer, Jennifer; Morgan, Douglas; Nichols, Joy; Günther, H Moritz; Gorynya, Natalya; Rastorguev, Alexey; Moskalik, Pawel

    2015-01-01

    We have examined high accuracy radial velocities of Cepheids to determine the binary frequency. The data are largely from the CORAVEL spectrophotometer and the Moscow version, with a typical uncertainty of $\\leq1$~km~s$^{-1}$, and a time span from 1 to 20 years. A systemic velocity was obtained by removing the pulsation component using a high order Fourier series. From this data we have developed a list of stars showing no orbital velocity larger than $\\pm1$~km~s$^{-1}$. The binary fraction was analyzed as a function of magnitude, and yields an apparent decrease in this fraction for fainter stars. We interpret this as incompleteness at fainter magnitudes, and derive the preferred binary fraction of $29\\pm8$\\% ( $20\\pm6$\\% per decade of orbital period) from the brightest 40 stars. Comparison of this fraction in this period range (1-20 years) implies a large fraction for the full period range. This is reasonable in that the high accuracy velocities are sensitive to the longer periods and smaller orbital velocit...

  2. Understanding the dynamical structure of pulsating stars. HARPS spectroscopy of the delta Scuti stars rho Pup and DX Cet

    CERN Document Server

    Nardetto, N; Rainer, M; Guiglion, G; Scardia, M; Schmid, V S; Mathias, P

    2014-01-01

    High-resolution spectroscopy is a powerful tool to study the dynamical structure of pulsating stars atmosphere. We aim at comparing the line asymmetry and velocity of the two delta Sct stars rho Pup and DX Cet with previous spectroscopic data obtained on classical Cepheids and beta Cep stars. We obtained, analysed and discuss HARPS high-resolution spectra of rho Pup and DX Cet. We derived the same physical quantities as used in previous studies, which are the first-moment radial velocities and the bi-Gaussian spectral line asymmetries. The identification of f=7.098 (1/d) as a fundamental radial mode and the very accurate Hipparcos parallax promote rho Pup as the best standard candle to test the period-luminosity relations of delta Sct stars. The action of small-amplitude nonradial modes can be seen as well-defined cycle-to-cycle variations in the radial velocity measurements of rho Pup. Using the spectral-line asymmetry method, we also found the centre-of-mass velocities of rho Pup and DX Cet, V_gamma = 47.49...

  3. Calibrating the Cepheid Period-Luminosity relation from the infrared surface brightness technique I. The p-factor, the Milky Way relations, and a universal K-band relation

    CERN Document Server

    Storm, J; Fouque, P; Barnes, T G; Pietrzynski, G; Nardetto, N; Weber, M; Granzer, T; Strassmeier, K

    2011-01-01

    We determine Period-Luminosity relations for Milky Way Cepheids in the optical and near-IR bands. These relations can be used directly as reference for extra-galactic distance determination to Cepheid populations with solar metallicity, and they form the basis for a direct comparison with relations obtained in exactly the same manner for stars in the Magellanic Clouds, presented in an accompanying paper. In that paper we show that the metallicity effect is very small and consistent with a null effect, particularly in the near-IR bands, and we combine here all 111 Cepheids from the Milky Way, the LMC and SMC to form a best relation. We employ the near-IR surface brightness (IRSB) method to determine direct distances to the individual Cepheids after we have recalibrated the projection factor using the recent parallax measurements to ten Galactic Cepheids and the constraint that Cepheid distances to the LMC should be independent of pulsation period. We confirm our earlier finding that the projection factor for c...

  4. Using Galactic Cepheids to verify Gaia parallaxes

    CERN Document Server

    Windmark, Fredrik; Hobbs, David

    2011-01-01

    Context. The Gaia satellite will measure highly accurate absolute parallaxes of hundreds of millions of stars by comparing the parallactic displacements in the two fields of view of the optical instrument. The requirements on the stability of the 'basic angle' between the two fields are correspondingly strict, and possible variations (on the microarcsec level) are therefore monitored by an on-board metrology system. Nevertheless, since even very small periodic variations of the basic angle might cause a global offset of the measured parallaxes, it is important to find independent verification methods. Aims. We investigate the potential use of Galactic Cepheids as standard candles for verifying the Gaia parallax zero point. Methods. We simulate the complete population of Galactic Cepheids and their observations by Gaia. Using the simulated data, simultaneous fits are made of the parameters of the period-luminosity relation and a global parallax zero point. Results. The total number of Galactic Cepheids is esti...

  5. Cepheid distances from infrared long-baseline interferometry - I. VINCI/VLTI observations of seven Galactic Cepheids

    CERN Document Server

    Kervella, P; Bersier, D F; Mourard, D; Foresto, V C

    2003-01-01

    We report the angular diameter measurements of seven classical Cepheids (X Sgr, eta Aql, W Sgr, zeta Gem, beta Dor, Y Oph and L Car) that we have obtained with the VINCI instrument, installed at ESO's VLT Interferometer (VLTI). We also present reprocessed archive data obtained with the FLUOR/IOTA instrument on zeta Gem, in order to improve the phase coverage of our observations. We obtain average limb darkened angular diameter values of LD(X Sgr) = 1.471 +/- 0.033 mas, LD(eta Aql) = 1.839 +/- 0.028 mas, LD(W Sgr) = 1.312 +/- 0.029 mas, LD(beta Dor) = 1.891 +/- 0.024 mas, LD(zeta Gem) =1.747 +/- 0.061 mas, LD(Y Oph) = 1.437 +/- 0.040 mas and LD(L Car) = 2.988 +/- 0.012 mas. For four of these stars (eta Aql, W Sgr, beta Dor, and L Car) we detect the pulsational variation of their angular diameter. This enables us to compute directly their distances, using a modified version of the Baade-Wesselink method: d(eta Aql) = 276 [+55 -38] pc, d(W Sgr) = 379 [+216 -130] pc, d(beta Dor) = 345 [+175 -80] pc, d(L Car) = 60...

  6. Period-color and amplitude-color relations in classical Cepheid variables III: The Large Magellanic Cloud Cepheid models

    CERN Document Server

    Kanbur, S; Kanbur, Shashi; Ngeow, Chow-Choong

    2006-01-01

    Period-colour (PC) and amplitude-colour (AC) relations are studied for the Large Magellanic Cloud (LMC) Cepheids under the theoretical framework of the hydrogen ionization front (HIF) - photosphere interaction. LMC models are constructed with pulsation codes that include turbulent convection, and the properties of these models are studied at maximum, mean and minimum light. As with Galactic models, at maximum light the photosphere is located next to the HIF for the LMC models. However very different behavior is found at minimum light. The long period (P>10days) LMC models imply that the photosphere is disengaged from the HIF at minimum light, similar to the Galactic models, but there are some indications that the photosphere is located near the HIF for the short period (P<10 days) LMC models. We also use the updated LMC data to derive empirical PC and AC relations at these phases. Our numerical models are broadly consistent with our theory and the observed data, though we discuss some caveats in the paper....

  7. Statistical Tests for the Metallicity Dependency of the Synthetic Cepheid Period-Luminosity Relations in IRAC Bands

    CERN Document Server

    Ngeow, Chow-Choong; Musella, Ilaria; Cignoni, Michele; Kanbur, Shashi

    2011-01-01

    The mid-infrared (MIR) period-luminosity (P-L) relations for Cepheids will be important in the JWST era, as it holds the promise of deriving the Hubble constant within 2% accuracy. It is expected that the MIR P-L to be insensitive to metallicity. In this work, we test this assumption of metallicity independent of the IRAC band P-L relation by applying well-known statistical methods to the synthetic P-L slopes from a series of pulsating models with known metallicity. The statistical tests suggest that the P-L slopes in MIR are linearly depending on metallicity.

  8. Stellar variability in open clusters. II. Discovery of a new period-luminosity relation in a class of fast-rotating pulsating stars in NGC 3766

    CERN Document Server

    Mowlavi, N; Semaan, T; Eggenberger, P; Barblan, F; Eyer, L; Ekström, S; Georgy, C

    2016-01-01

    $Context.$ Pulsating stars are windows to the physics of stars enabling us to see glimpses of their interior. Not all stars pulsate, however. On the main sequence, pulsating stars form an almost continuous sequence in brightness, except for a magnitude range between $\\delta$ Scuti and slowly pulsating B stars. Against all expectations, 36 periodic variables were discovered in 2013 in this luminosity range in the open cluster NGC 3766, the origins of which was a mystery. $Aims.$ We investigate the properties of those new variability class candidates in relation to their stellar rotation rates and stellar multiplicity. $Methods.$ We took multi-epoch spectra over three consecutive nights using ESO's Very Large Telescope. $Results.$ We find that the majority of the new variability class candidates are fast-rotating pulsators that obey a new period-luminosity relation. We argue that the new relation discovered here has a different physical origin to the period-luminosity relations observed for Cepheids. $Conclusio...

  9. A Comprehensive, Wide-Field Study of Pulsating Stars in the Carina Dwarf Spheroidal Galaxy

    CERN Document Server

    Vivas, A Katherina

    2013-01-01

    We report the detection of 388 pulsating variable stars (and some additional miscellaneous variables) in the Carina dSph galaxy over an area covering the full visible extent of the galaxy and extending a few times beyond its photometric (King) tidal radius along the direction of its major axis. Included in this total are 340 newly discovered dwarf Cepheids which are mostly located ~2.5 magnitudes below the horizontal branch and have very short periods (<0.1 days) typical of their class and consistent with their location on the upper part of the extended main sequence of the younger populations of the galaxy. Several extra-tidal dwarf cepheids were found in our survey up to a distance of ~1 degree from the center of Carina. Our sample also includes RR Lyrae stars and anomalous Cepheids some of which were found outside the galaxy's tidal radius as well. This supports past works that suggests Carina is undergoing tidal disruption. We use the period-luminosity relationship for dwarf Cepheids to estimate a dist...

  10. The VMC Survey. XIX. Classical Cepheids in the Small Magellanic Cloud

    CERN Document Server

    Ripepi, V; Moretti, M I; Clementini, G; Cioni, M -R L; de Grijs, R; Emerson, J P; Groenewegen, M A T; Ivanov, V D; Piatti, A E

    2016-01-01

    The VISTA near infrared Y, J, Ks survey of the Magellanic System (VMC) is collecting deep Ks band time series photometry of pulsating variable stars hosted by the two Magellanic Clouds and their connecting Bridge. In this paper, we present Y, J, Ks light curves for a sample of 4172 Small Magellanic Cloud (SMC) Classical Cepheids (CCs). These data, complemented with literature V values, allowed us to construct a variety of period-luminosity (PL), period-luminosity-color (PLC), and period-wesenheit (PW) relationships, valid for Fundamental (F), First Overtone (FO) and Second Overtone (SO) pulsators. The relations involving V, J, Ks bands are in agreement with their counterparts in the literature. As for the Y band, to our knowledge we present the first CC PL, PW, and PLC relations ever derived using this filter. We also present the first near infrared PL, PW, and PLC relations for SO pulsators to date. We used PW(V,Ks) to estimate the relative SMC-LMC distance and, in turn, the absolute distance to the SMC. For...

  11. A Global Physical Model for Cepheids

    CERN Document Server

    Pejcha, Ondrej

    2011-01-01

    We perform a global fit to ~5,000 radial velocity and ~177,000 magnitude measurements in 29 photometric bands covering 0.3 to 8.0 microns distributed among 287 Galactic, LMC, and SMC Cepheids with P > 10 days. We assume that the Cepheid light curves and radial velocities are fully characterized by distance, reddening, and time-dependent radius and temperature variations. We construct phase curves of radius and temperature for periods between 10 and 100 days, which yield light curve templates for all our photometric bands and can be easily generalized to any additional band. With only 4 to 6 parameters per Cepheid, depending on the existence of velocity data and the amount of freedom in the distance, the models have typical rms light and velocity curve residuals of 0.05 mag and 3.5 km/s. The model derives the mean Cepheid spectral energy distribution and its derivative with respect to temperature, which deviate from a black body in agreement with metal-line and molecular opacity effects. We determine a mean re...

  12. The Araucaria Project: A Study of the Classical Cepheid in the Eclipsing Binary System OGLE LMC562.05.9009 in the Large Magellanic Cloud

    Science.gov (United States)

    Gieren, Wolfgang; Pilecki, Bogumił; Pietrzyński, Grzegorz; Graczyk, Dariusz; Udalski, Andrzej; Soszyński, Igor; Thompson, Ian B.; Prada Moroni, Pier Giorgio; Smolec, Radosław; Konorski, Piotr; Górski, Marek; Karczmarek, Paulina; Suchomska, Ksenia; Taormina, Mónica; Gallenne, Alexandre; Storm, Jesper; Bono, Giuseppe; Catelan, Márcio; Szymański, Michał; Kozłowski, Szymon; Pietrukowicz, Paweł; Wyrzykowski, Łukasz; Poleski, Radosław; Skowron, Jan; Minniti, Dante; Ulaczyk, K.; Mróz, P.; Pawlak, M.; Nardetto, Nicolas

    2015-12-01

    We present a detailed study of the classical Cepheid in the double-lined, highly eccentric eclipsing binary system OGLE-LMC562.05.9009. The Cepheid is a fundamental mode pulsator with a period of 2.988 days. The orbital period of the system is 1550 days. Using spectroscopic data from three 4-8-m telescopes and photometry spanning 22 years, we were able to derive the dynamical masses and radii of both stars with exquisite accuracy. Both stars in the system are very similar in mass, radius, and color, but the companion is a stable, non-pulsating star. The Cepheid is slightly more massive and bigger (M1 = 3.70 ± 0.03 M⊙, R1 = 28.6 ± 0.2 R⊙) than its companion (M2 = 3.60 ± 0.03 M⊙, R2 = 26.6 ± 0.2 R⊙). Within the observational uncertainties both stars have the same effective temperature of 6030 ± 150 K. Evolutionary tracks place both stars inside the classical Cepheid instability strip, but it is likely that future improved temperature estimates will move the stable giant companion just beyond the red edge of the instability strip. Within current observational and theoretical uncertainties, both stars fit on a 205 Myr isochrone arguing for their common age. From our model, we determine a value of the projection factor of p = 1.37 ± 0.07 for the Cepheid in the OGLE-LMC562.05.9009 system. This is the second Cepheid for which we could measure its p-factor with high precision directly from the analysis of an eclipsing binary system, which represents an important contribution toward a better calibration of Baade-Wesselink methods of distance determination for Cepheids. This research is based on observations obtained with the ESO VLT, 3.6 m and NTT telescopes for Programmes 092.D-0295(A), 091.D-0393(A), 089.D-0330(A), 088.D-0447(A), 086.D-0103(A) and 085.D-0398(A)), and with the Magellan Clay and Warsaw telescopes at Las Campanas Observatory.

  13. VI-Band Follow-Up Observations of Ultra-Long-Period Cepheid Candidates in M31

    CERN Document Server

    Ngeow, Chow-Choong; Yang, Michael Ting-Chang; Lin, Chi-Sheng; Hsiao, Hsiang-Yao; Cheng, Yu-Chi; Lin, Zhong-Yi; Lin, I-Ling; Kanbur, Shashi M; Ip, Wing-Huen

    2015-01-01

    The ultra-long period Cepheids (ULPCs) are classical Cepheids with pulsation periods exceeding $\\approx 80$ days. The intrinsic brightness of ULPCs are ~1 to ~3 mag brighter than their shorter period counterparts. This makes them attractive in future distance scale work to derive distances beyond the limit set by the shorter period Cepheids. We have initiated a program to search for ULPCs in M31, using the single-band data taken from the Palomar Transient Factory, and identified eight possible candidates. In this work, we presented the VI-band follow-up observations of these eight candidates. Based on our VI-band light curves of these candidates and their locations in the color-magnitude diagram and the Period-Wesenheit diagram, we verify two candidates as being truly ULPCs. The six other candidates are most likely other kinds of long-period variables. With the two confirmed M31 ULPCs, we tested the applicability of ULPCs in distance scale work by deriving the distance modulus of M31. It was found to be $\\mu_...

  14. Excess Mid-Infrared Flux: An Indicator of Mass Loss in Cepheids?

    Science.gov (United States)

    Schmidt, Edward G.

    2015-11-01

    Spectral energy distributions for 132 classical and type II Cepheids were searched for evidence of excess flux above the photospheric level in the mid-infrared. Eight of them were found to have unambiguously strong excess emission while a further 13 showed evidence of weak emission. The presence of emission appears to be unrelated to either the pulsational amplitude or the effective temperature while strong emission is limited to stars with periods longer than 11 days, with a single exception. For the stars with strong emission we attempted to fit the energy distribution with a stellar wind model. No acceptable fit could be found for silicate grains. With graphite or iron grains we could only obtain an acceptable fit if the maximum dust temperature was significantly lower than the condensation temperature. We conclude that the excess emission is not evidence of mass loss.

  15. Hα Line as An indicator Of Envelope Presence Around the Cepheid Polaris Aa (α UMi)

    Science.gov (United States)

    Usenko, I. A.; Miroshnichenko, A. S.; Klochkova, V. G.; Tavolzhanskaya, N. S.

    We present the results of the radial velocity (RV) measurements of metallic lines as well as Hα (Hβ ) obtained in 55 high-resolution spectra of the Cepheid α UMi (Polaris Aa) in 1994-2010. While the RV amplitudes of these lines are roughly equal, their mean RV begin to differ essentially with growth of the Polaris Aa pulsational activity. This difference is accompanied by the Hα core asymmetries on the red side mainly (so-called knifelike profiles) and reaches the value of 8-12 km/s in 2003 with subsequent decrease to 1.5-2 km/s. We interpret so unusual behaviour of the Hα line core as dynamical changes in the envelope around Polaris Aa.

  16. White dwarf pulsations

    International Nuclear Information System (INIS)

    The DA white dwarfs are those which show only the Stark-broadened lines of hydrogen in their spectra. They comprise about 80% of the total white dwarf population. A subset of the DA dwarfs, the ZZ Ceti stars, form a highly homogeneous class of nonradially pulsating variable stars. In this paper we shall review the observations from which both the physical properties of the stars and the characteristics of the pulsations have been derived. Data obtained since the last review of these variables (Robinson 1979) is stressed, as these data are forcing a somewhat revised understanding of the ZZ Ceti stars and their relationship to investigations of white dwarfs and to pulsating variable stars, in general. (orig.)

  17. The RCB star RY Sagittarii as a pulsating star

    Science.gov (United States)

    Lloyd Evans, T.

    1986-03-01

    Measurements of CN and C2 bandstrengths in the spectrum of RY Sagittarii in 1969 and 1970, when it was on the latter part of its return to maximum and during its subsequent stay at maximum light after the deep minimum of 1967-68, show that the bands vary in strength in the 38.6-day pulsation period. The variations follow the phasing of the B-V and U-B color curves rather than the V light curve, and must be determined largely by the photospheric temperature as in the case of the carbon-rich Cepheid V553 Centauri. This is supported by a comparison of the ranges in color and in bandstrength, though the bands are stronger at a given color than in typical class Ib supergiants.

  18. LARGE EDDY SIMULATION OF PULSATING TURBULENT OPEN CHANNEL FLOW

    Institute of Scientific and Technical Information of China (English)

    ZOU Li-yong; LIU Nan-sheng; LU Xi-yun

    2004-01-01

    Pulsating turbulent open channel flow has been investigated by the use of Large Eddy Simulation (LES) technique coupled with dynamic Sub-Grid-Scale (SGS) model for turbulent SGS stress to closure the governing equations. Three-dimensional filtered Navier-Stokes equations are numerically solved by a fractional-step method. The objective of this study is to deal with the behavior of the pulsating turbulent open channel flow and to examine the reliability of the LES approach for predicting the pulsating turbulent flow. In this study, the Reynolds number (Reτ ) is chosen as 180 based on the friction velocity and the channel depth. The frequency of the driving pressure gradient for the pulsating turbulent flow ranges low, medium and high value. Statistical turbulence quantities as well as the flow structures are analyzed.

  19. Convective hydrocodes for radial stellar pulsation. Physical and numerical formulation

    CERN Document Server

    Smolec, R

    2008-01-01

    In this paper we describe our convective hydrocodes for radial stellar pulsation. We adopt the Kuhfuss (1986) model of convection, reformulated for the use in stellar pulsation hydrocodes. Physical as well as numerical assumptions of the code are described in detail. Described tests show, that our models are numerically robust and reproduce basic observational constraints. We discuss the effects of different treatment of some quantities in other pulsation hydrocodes. Our most important finding concerns the treatment of the turbulent source function in convectively stable regions. In our code we allow for negative values of source function in convectively stable zones, which reflects negative buoyancy. However, some authors restrict the source term to non-negative values. We show that this assumption leads to very high turbulent energies in convectively stable regions. The effect looks like overshooting, but it is not, because turbulence is generated by pulsations. Also, turbulent elements do not carry kinetic...

  20. The Cepheids of NGC 1866: a precise benchmark for the extragalactic distance scale and stellar evolution from modern UBVI photometry

    Science.gov (United States)

    Musella, I.; Marconi, M.; Stetson, P. B.; Raimondo, G.; Brocato, E.; Molinaro, R.; Ripepi, V.; Carini, R.; Coppola, G.; Walker, A. R.; Welch, D. L.

    2016-04-01

    We present the analysis of multiband time series data for a sample of 24 Cepheids in the field of the Large Magellanic Cloud cluster NGC 1866. Very accurate BVI Very Large Telescope photometry is combined with archival UBVI data, covering a large temporal window, to obtain precise mean magnitudes and periods with typical errors of 1-2 per cent and of 1 ppm, respectively. These results represent the first accurate and homogeneous data set for a substantial sample of Cepheid variables belonging to a cluster and hence sharing common distance, age and original chemical composition. Comparisons of the resulting multiband period-luminosity and Wesenheit relations to both empirical and theoretical results for the Large Magellanic Cloud are presented and discussed to derive the distance of the cluster and to constrain the mass-luminosity relation of the Cepheids. The adopted theoretical scenario is also tested by comparison with independent calibrations of the Cepheid Wesenheit zero-point based on trigonometric parallaxes and Baade-Wesselink techniques. Our analysis suggests that a mild overshooting and/or a moderate mass-loss can affect intermediate-mass stellar evolution in this cluster and gives a distance modulus of 18.50 ± 0.01 mag. The obtained V,I colour-magnitude diagram is also analysed and compared with both synthetic models and theoretical isochrones for a range of ages and metallicities and for different efficiencies of core overshooting. As a result, we find that the age of NGC 1866 is about 140 Myr, assuming Z = 0.008 and the mild efficiency of overshooting suggested by the comparison with the pulsation models.

  1. Method of LSD profile asymmetry for estimating the center of mass velocities of pulsating stars

    Science.gov (United States)

    Britavskiy, N.; Pancino, E.; Tsymbal, V.; Romano, D.; Cacciari, C.; Clementini, C.

    2016-05-01

    We present radial velocity analysis for 20 solar neighborhood RR Lyrae and 3 Population II Cepheids. High-resolution spectra were observed with either TNG/SARG or VLT/UVES over varying phases. To estimate the center of mass (barycentric) velocities of the program stars, we utilized two independent methods. First, the 'classic' method was employed, which is based on RR Lyrae radial velocity curve templates. Second, we provide the new method that used absorption line profile asymmetry to determine both the pulsation and the barycentric velocities even with a low number of high-resolution spectra and in cases where the phase of the observations is uncertain. This new method is based on a least squares deconvolution (LSD) of the line profiles in order to an- alyze line asymmetry that occurs in the spectra of pulsating stars. By applying this method to our sample stars we attain accurate measurements (+- 2 kms^-1) of the pulsation component of the radial velocity. This results in determination of the barycentric velocity to within 5 kms^-1 even with a low number of high- resolution spectra. A detailed investigation of LSD profile asymmetry shows the variable nature of the project factor at different pulsation phases, which should be taken into account in the detailed spectroscopic analysis of pulsating stars.

  2. Interaction Between Convection and Pulsation

    Science.gov (United States)

    Houdek, Günter; Dupret, Marc-Antoine

    2015-12-01

    This article reviews our current understanding of modelling convection dynamics in stars. Several semi-analytical time-dependent convection models have been proposed for pulsating one-dimensional stellar structures with different formulations for how the convective turbulent velocity field couples with the global stellar oscillations. In this review we put emphasis on two, widely used, time-dependent convection formulations for estimating pulsation properties in one-dimensional stellar models. Applications to pulsating stars are presented with results for oscillation properties, such as the effects of convection dynamics on the oscillation frequencies, or the stability of pulsation modes, in classical pulsators and in stars supporting solar-type oscillations.

  3. New NIR light-curve templates for classical Cepheids

    NARCIS (Netherlands)

    L. Inno; N. Matsunaga; M. Romaniello; G. Bono; A. Monson; I. Ferraro; G. Iannicola; E. Persson; R. Buonanno; W. Freedman; W. Gieren; M.A.T. Groenewegen; Y. Ita; C.D. Laney; B. Lemasle; B.F. Madore; T. Nagayama; Y. Nakada; M. Nonino; G. Pietrzyński; F. Primas; V. Scowcroft; I. Soszyński; T. Tanabé; A. Udalski

    2015-01-01

    Aims. We present new near-infrared (NIR) light-curve templates for fundamental (FU, J, H, KS) and first overtone (FO, J) classical Cepheids. The new templates together with period-luminosity and period-Wesenheit (PW) relations provide Cepheid distances from single-epoch observations with a precision

  4. Enhancing Our Knowledge of Northern Cepheids through Photometric Monitoring

    CERN Document Server

    Turner, David G; Lane, David J; Szabados, L; Kovtyukh, V V; Usenko, I A; Berdnikov, Leonid N

    2009-01-01

    A selection of known and newly-discovered northern hemisphere Cepheids and related objects are being monitored regularly through CCD observations at the automated Abbey Ridge Observatory, near Halifax, and photoelectric photometry from the Saint Mary's University Burke-Gaffney Observatory. Included is Polaris, which is displaying unusual fluctuations in its growing light amplitude, and a short-period, double-mode Cepheid, HDE 344787, with an amplitude smaller than that of Polaris, along with a selection of other classical Cepheids in need of additional observations. The observations are being used to establish basic parameters for the Cepheids, for application to the Galactic calibration of the Cepheid period-luminosity relation as well as studies of Galactic structure.

  5. Kinematics of classical Cepheids in the Nuclear Stellar Disk

    CERN Document Server

    Matsunaga, N; Yamamoto, R; Kobayashi, N; Inno, L; Genovali, K; Bono, G; Baba, J; Fujii, M S; Kondo, S; Ikeda, Y; Hamano, S; Nishiyama, S; Nagata, T; Aoki, W; Tsujimoto, T

    2014-01-01

    Classical Cepheids are useful tracers of the Galactic young stellar population because their distances and ages can be determined from their period-luminosity and period-age relations. In addition, the radial velocities and chemical abundance of the Cepheids can be derived from spectroscopic observations, providing further insights into the structure and evolution of the Galaxy. Here, we report the radial velocities of classical Cepheids near the Galactic Center, three of which were reported in 2011, the other reported for the first time. The velocities of these Cepheids suggest that the stars orbit within the Nuclear Stellar Disk, a group of stars and interstellar matter occupying a region of 200 pc around the Center, although the three-dimensional velocities cannot be determined until the proper motions are known. According to our simulation, these four Cepheids formed within the Nuclear Stellar Disk like younger stars and stellar clusters therein.

  6. The Kepler Cepheid V1154 Cyg revisited: light curve modulation and detection of granulation

    CERN Document Server

    Derekas, A; Molnar, L; Sodor, A; Benko, J M; Szabados, L; Bognar, Zs; Csak, B; Szabo, Gy M; Szabo, R; Pal, A

    2016-01-01

    We present a detailed analysis of the bright Cepheid-type variable star V1154 Cygni using 4 years of continuous observations by the Kepler space telescope. We detected 28 frequencies using standard Fourier transform method.We identified modulation of the main pulsation frequency and its harmonics with a period of ~159 d. This modulation is also present in the Fourier parameters of the light curve and the O-C diagram. We detected another modulation with a period of about 1160 d. The star also shows significant power in the low-frequency region that we identified as granulation noise. The effective timescale of the granulation agrees with the extrapolated scalings of red giant stars. Non-detection of solar-like oscillations indicates that the pulsation inhibits other oscillations. We obtained new radial velocity observations which are in a perfect agreement with previous years data, suggesting that there is no high mass star companion of V1154 Cygni. Finally, we discuss the possible origin of the detected frequ...

  7. The VMC Survey. XIII. Type II Cepheids in the Large Magellanic Cloud

    CERN Document Server

    Ripepi, V; Marconi, M; Clementini, G; Cioni, M-R L; de Grijs, R; Emerson, J P; Groenewegen, M A T; Ivanov, V D; Muraveva, T; Piatti, A E; Subramanian, S

    2014-01-01

    The VISTA survey of the Magellanic Clouds System (VMC) is collecting deep $K_\\mathrm{s}$--band time--series photometry of the pulsating variable stars hosted in the system formed by the two Magellanic Clouds and the Bridge connecting them. In this paper we have analysed a sample of 130 Large Magellanic Cloud (LMC) Type II Cepheids (T2CEPs) found in tiles with complete or near complete VMC observations for which identification and optical magnitudes were obtained from the OGLE III survey. We present $J$ and $K_\\mathrm{s}$ light curves for all 130 pulsators, including 41 BL Her, 62 W Vir (12 pW Vir) and 27 RV Tau variables. We complement our near-infrared photometry with the $V$ magnitudes from the OGLE III survey, allowing us to build a variety of Period-Luminosity ($PL$), Period-Luminosity-Colour ($PLC$) and Period-Wesenheit ($PW$) relationships, including any combination of the $V, J, K_\\mathrm{s}$ filters and valid for BL Her and W Vir classes. These relationships were calibrated in terms of the LMC distanc...

  8. Gas Pulsation Control Using a Shunt Pulsation Trap

    OpenAIRE

    Huang, Paul Xiubao; Yonkers, Sean; Hokey, David

    2014-01-01

    Gas pulsations commonly exist in HVACR, energy and automotive industry. They are believed to be a major source for system inefficiency, vibrations, noises and fatigue failures. It has been widely accepted that gas pulsations mainly take place at the discharge side of a positive displacement (PD) type compressor such as a screw, scroll or internal combustion engine. The pulsation magnitudes, ranging from a fraction to a few bars, are especially significant at off-design conditions of either un...

  9. Spectroscopic studies of the classical Cepheid ζ Gem: Analysis of the velocity field in the atmosphere and manifestation of the presence of a circumstellar envelope

    Science.gov (United States)

    Usenko, I. A.

    2016-06-01

    Based on five high-resolution spectra in the range 5625-7525 ˚A taken in 1995 and covering the ascending branch of the light curve from minimum to maximum, we have performed spectroscopic studies of the classical Cepheid ζ Gem. The atmospheric parameters and chemical composition of the Cepheid have been refined. The abundances of the key elements of the evolution of yellow supergiants are typical for an object that has passed the first dredge-up: a C underabundance, N, Na, and Al overabundances, and nearly solar O and Mg abundances. We have estimated [Fe/H] = +0.01 dex; the abundances of the remaining elements are also nearly solar. The metal absorption lines in all spectra show a clear asymmetry and the formation of secondary blue (B1 and B2) and red (R1 and R2) components, just as for the Cepheid X Sgr. The Hα absorption line is also split into blue (B) and red (R) components with different depths changing with pulsation phase. To analyze the velocity field in the atmosphere of ζ Gem, we have estimated the radial velocities from specially selected (with clear signatures of the B1, B2, R1, and R2 components) absorption lines (neutral atoms and ions) of metals (38 lines) and the B and R components of the Hα line. Analysis of these estimates has shown that their scatter is from -22 to 36 km s-1 for all pulsation phases but does not exceed 35-40 km s-1 for each individual phase, while it does not exceed 22 km s-1 for the Hα line components. The radial velocity estimates for the metal lines and their B1 and B2 components have been found to depend on the depths, suggesting the presence of a velocity gradient in the atmosphere. No significant difference in velocities between the atoms and ions of the metal lines is observed, i.e., there is no significant inhomogeneity in the upper atmospheric layers of the Cepheid. Since the averaged radial velocity estimates for the cores of the metal lines and their B1 and B2 components change with pulsation phase and coincide

  10. New NIR light-curve templates for classical Cepheids

    CERN Document Server

    Inno, L; Romaniello, M; Bono, G; Monson, A; Ferraro, I; Iannicola, G; Persson, E; Buonanno, R; Freedman, W; Gieren, W; Groenewegen, M A T; Ita, Y; Laney, C D; Lemasle, B; Madore, B F; Nagayama, T; Nakada, Y; Nonino, M; Pietrzynski, G; Primas, F; Scowcroft, V; Soszynski, I; Tanabe, T; Udalski, A

    2014-01-01

    We present new near-infrared (NIR) light-curve templates for fundamental (FU, JHK) and first overtone (FO, J) Cepheids. The new templates together with PL and PW relations provide Cepheid distances from single-epoch observations with a precision only limited by the intrinsic accuracy of the method adopted. The templates rely on a very large set of Galactic and Magellanic Clouds (MCs) Cepheids (FU,~600; FO,~200) with well sampled NIR (IRSF data) and optical (V,I; OGLE data) light curves. To properly trace the change in the shape of the light curve as a function of period, we split the sample of calibrating Cepheids into 10 different period bins. The templates for the first time cover FO Cepheids and the FU short-period Cepheids (P<5 days). Moreover, the zero-point phase is anchored to the phase of the mean magnitude along the rising branch. The new approach has several advantages in sampling the light curve of bump Cepheids when compared with the phase of maximum light. We also provide new estimates of the ...

  11. KIC2569073, A second Cepheid in the Kepler FOV

    Directory of Open Access Journals (Sweden)

    Drury Jason A.

    2015-01-01

    Full Text Available One particularly interesting new variable discovered via Kepler’s 200x200 pixel superstamp images is KIC2569073. With a period of 14.66 days and 0.04mag variability it is only the second Cepheid in the Kepler field, or a rotationally modulated variable. We discuss its classification as a Type II W Virginis Class Cepheid, and present the cycle-to-cycle period variations of this star, as well as the first direct observations of granulation noise within a Cepheid.

  12. Large Variety of New Pulsating Stars in the OGLE-III Galactic Disk Fields

    CERN Document Server

    Pietrukowicz, P; Mroz, P; Soszynski, I; Udalski, A; Poleski, R; Szymanski, M K; Kubiak, M; Pietrzynski, G; Wyrzykowski, L; Ulaczyk, K; Kozlowski, S; Skowron, J

    2013-01-01

    We present the results of a search for pulsating stars in the 7.12 deg^2 OGLE-III Galactic disk area in the direction tangent to the Centaurus Arm. We report the identification of 20 Classical Cepheids, 45 RR Lyr type stars, 14 Long-Period Variables, such as Miras and Semi-Regular Variables, and 56 very likely delta Sct type stars. Based on asteroseismic models constructed for one quadruple-mode and six triple-mode delta Sct type pulsators, we estimated masses, metallicities, ages, and distance moduli to these objects. The modeled stars have masses in the range 0.9-2.5 M_sun and are located at distances between 2.5 kpc and 6.2 kpc. Two triple-mode and one double-mode pulsators seem to be Population II stars of the SX Phe type, probably from the Galactic halo. All reported pulsating variables but one object are new discoveries. They are included in the OGLE-III Catalog of Variable Stars. Finally, we introduce the on-going OGLE-IV Galactic Disk Survey, which covers half of the Galactic plane. For the purposes o...

  13. Pulsation driving and convection

    Science.gov (United States)

    Antoci, Victoria

    2015-08-01

    Convection in stellar envelopes affects not only the stellar structure, but has a strong impact on different astrophysical processes, such as dynamo-generated magnetic fields, stellar activity and transport of angular momentum. Solar and stellar observations from ground and space have shown that the turbulent convective motion can also drive global oscillations in many type of stars, allowing to study stellar interiors at different evolutionary stages. In this talk I will concentrate on the influence of convection on the driving of stochastic and coherent pulsations across the Hertzsprung-Russell diagram and give an overview of recent studies.

  14. Search for binaries among short-period southern Cepheids

    Energy Technology Data Exchange (ETDEWEB)

    Gieren, W.

    1981-12-01

    Fifteen southern Cepheids with 3-7 day periods have been subjected to simultaneous radial velocity and UBV(RI)-KC photometric observations. A comparison of the resulting radial velocity curves with earlier data confirms the binary nature of V 350 Sgr, and indicates that RTrA, AP Sgr and V 496 Aql are binary as well. The lack of significant spectroscopic distinction between the binary and nonbinary Cepheids implies that the companion stars to the binary ones are neither very luminous nor able to alter Cepheid photometric properties. Doubts are raised concerning the reliability of the U-B versus B-V diagram open loop method results obtained for the case of small loop openings. The variable-gamma velocity method is more reliable for Cepheid binary searches.

  15. Asteroseismology of Pulsating Stars

    Indian Academy of Sciences (India)

    Santosh Joshi; Yogesh C. Joshi

    2015-03-01

    The success of helioseismology is due to its capability of measuring -mode oscillations in the Sun. This allows us to extract information on the internal structure and rotation of the Sun from the surface to the core. Similarly, asteroseismology is the study of the internal structure of the stars as derived from stellar oscillations. In this review we highlight the progress in the observational asteroseismology, including some basic theoretical aspects. In particular, we discuss our contributions to asteroseismology through the study of chemically peculiar stars under the 'Nainital-Cape Survey' project being conducted at ARIES, Nainital, since 1999. This survey aims to detect new rapidly-pulsating Ap (roAp) stars in the northern hemisphere. We also discuss the contribution of ARIES towards the asteroseismic study of the compact pulsating variables. We comment on the future prospects of our project in the light of the new optical 3.6-m telescope to be installed at Devasthal (ARIES). Finally, we present a preliminary optical design of the high-speed imaging photometers for this telescope.

  16. VI-Band Follow-Up Observations of Ultra-Long-Period Cepheid Candidates in M31

    Science.gov (United States)

    Ngeow, Chow-Choong; Lee, Chien-Hsiu; Ting-Chang Yang, Michael; Lin, Chi-Sheng; Hsiao, Hsiang-Yao; Cheng, Yu-Chi; Lin, Zhong-Yi; Lin, I.-Ling; Kanbur, Shashi M.; Ip, Wing-Huen

    2015-02-01

    The ultra-long-period Cepheids (ULPCs) are classical Cepheids with pulsation periods exceeding ≈ 80 days. The intrinsic brightness of ULPCs are ˜ 1 to ˜ 3 mag brighter than their shorter period counterparts. This makes them attractive in future distance scale work to derive distances beyond the limit set by the shorter period Cepheids. We have initiated a program to search for ULPCs in M31, using the single-band data taken from the Palomar Transient Factory, and identified eight possible candidates. In this work, we presented the VI-band follow-up observations of these eight candidates. Based on our VI-band light curves of these candidates and their locations in the color-magnitude diagram and the Period-Wesenheit diagram, we verify two candidates as being truly ULPCs. The six other candidates are most likely other kinds of long-period variables. With the two confirmed M31 ULPCs, we tested the applicability of ULPCs in distance scale work by deriving the distance modulus of M31. It was found to be {{μ }M31,ULPC}=24.30+/- 0.76 mag. The large error in the derived distance modulus, together with the large intrinsic dispersion of the Period-Wesenheit (PW) relation and the small number of ULPCs in a given host galaxy, means that the question of the suitability of ULPCs as standard candles is still open. Further work is needed to enlarge the sample of calibrating ULPCs and reduce the intrinsic dispersion of the PW relation before re-considering ULPCs as suitable distance indicators.

  17. VI-band follow-up observations of ultra-long-period Cepheid candidates in M31

    Energy Technology Data Exchange (ETDEWEB)

    Ngeow, Chow-Choong; Yang, Michael Ting-Chang; Lin, Chi-Sheng; Hsiao, Hsiang-Yao; Cheng, Yu-Chi; Lin, Zhong-Yi; Lin, I-Ling; Ip, Wing-Huen [Graduate Institute of Astronomy, National Central University, Jhongli 32001, Taiwan (China); Lee, Chien-Hsiu [Max Planck Institute for Extraterrestrial Physics, D-85748 Garching (Germany); Kanbur, Shashi M. [Department of Physics, SUNY Oswego, Oswego, NY 13126 (United States)

    2015-02-01

    The ultra-long-period Cepheids (ULPCs) are classical Cepheids with pulsation periods exceeding ≈80 days. The intrinsic brightness of ULPCs are ∼1 to ∼3 mag brighter than their shorter period counterparts. This makes them attractive in future distance scale work to derive distances beyond the limit set by the shorter period Cepheids. We have initiated a program to search for ULPCs in M31, using the single-band data taken from the Palomar Transient Factory, and identified eight possible candidates. In this work, we presented the VI-band follow-up observations of these eight candidates. Based on our VI-band light curves of these candidates and their locations in the color–magnitude diagram and the Period–Wesenheit diagram, we verify two candidates as being truly ULPCs. The six other candidates are most likely other kinds of long-period variables. With the two confirmed M31 ULPCs, we tested the applicability of ULPCs in distance scale work by deriving the distance modulus of M31. It was found to be μ{sub M31,ULPC}=24.30±0.76 mag. The large error in the derived distance modulus, together with the large intrinsic dispersion of the Period–Wesenheit (PW) relation and the small number of ULPCs in a given host galaxy, means that the question of the suitability of ULPCs as standard candles is still open. Further work is needed to enlarge the sample of calibrating ULPCs and reduce the intrinsic dispersion of the PW relation before re-considering ULPCs as suitable distance indicators.

  18. Theoretical fit of Cepheid light an radial velocity curves in the Large Magellanic Cloud cluster NGC 1866

    CERN Document Server

    Marconi, Marcella; Ripepi, Vincenzo; Musella, Ilaria; Brocato, Enzo

    2012-01-01

    We present a theoretical investigation of multifilter (U,B,V, I and K) light and radial velocity curves of five Classical Cepheids in NGC 1866, a young massive cluster of the Large Magellanic Cloud. The best fit models accounting for the luminosity and radial velocity variations of the five selected variables, four pulsating in the fundamental mode and one in the first overtone, provide direct estimates of their intrinsic stellar parameters and individual distances. The resulting stellar properties indicate a slightly brighter Mass Luminosity relation than the canonical one, possibly due to mild overshooting and/or mass loss. As for the inferred distances, the individual values are consistent within the uncertainties. Moreover, their weighted mean value corresponds to a distance modulus of 18.56 + - 0.03 (stat) + - 0.1 (syst) mag, in agreement with several independent results in the literature.

  19. H$_{\\alpha}$ line as an indicator of envelope presence around the Cepheid Polaris Aa ($\\alpha~ UMi$)

    CERN Document Server

    Usenko, I A; Klochkova, V G; Tavolzhanskaya, N S

    2015-01-01

    We present the results of the radial velocity ($RV$) measurements of metallic lines as well as H$_{\\alpha}$ (H$_{\\beta}$) obtained in 55 high-resolution spectra of the Cepheid $\\alpha$ UMi (Polaris Aa) in 1994-2010. While the $RV$ amplitudes of these lines are roughly equal, their mean $RV$ begin to differ essentially with growth of the Polaris Aa pulsational activity. This difference is accompanied by the H$_{\\alpha}$ line core asymmetries on the red side mainly (so-called knife-like profiles) and reaches 8-12 km/s in 2003 with a subsequent decrease to 1.5-2 km/s. We interpret a so unusual behaviour of the H$_{\\alpha}$ line core as dynamical changes in the envelope around Polaris Aa.

  20. Galactic Cepheids with Spitzer: I. Leavitt Law and Colors

    CERN Document Server

    Marengo, M; Barmby, P; Bono, G; Welch, D L; Romaniello, M

    2009-01-01

    Classical Cepheid variable stars have been important indicators of extragalactic distance and Galactic evolution for over a century. The Spitzer Space Telescope has opened the possibility of extending the study of Cepheids into the mid- and far-infrared, where interstellar extinction is reduced. We have obtained photometry from images of a sample of Galactic Cepheids with the IRAC and MIPS instruments on Spitzer. Here we present the first mid-infrared period-luminosity relations for Classical Cepheids in the Galaxy, and the first ever Cepheid period-luminosity relations at 24 and 70 um. We compare these relations with theoretical predictions, and with period-luminosity relations obtained in recent studies of the Large Magellanic Cloud. We find a significant period-color relation for the [3.6]-[8.0] IRAC color. Other mid-infrared colors for both Cepheids and non-variable supergiants are strongly affected by variable molecular spectral features, in particular deep CO absorption bands. We do not find strong evid...

  1. Discovery of a peculiar Cepheid-like star towards the northern edge of the Small Magellanic Cloud

    CERN Document Server

    Marquette, J B; François, P; Beaulieu, J P; Doublier, V; Lesquoy, E; Milsztajn, A; Pritchard, J; Schwarzenberg-Czerny, A; Afonso, C; Albert, J N; Andersen, J; Ansari, R; Aubourg, E; Bareyre, P; Charlot, X; Coutures, C; Ferlet, R; Fouqué, P; Glicenstein, J F; Goldman, B; Gould, A; Graff, D; Gros, M; Haïssinski, J; Hamadache, C; De Kat, J; Guillou, L Le; Loup, C; Magneville, C; Maurice, E; Maury, A; Moniez, M; Palanque-Delabrouille, Nathalie; Perdereau, O; Rahal, Y R; Rich, J; Spiro, M; Vidal-Madjar, A; Zylberajch, S

    2008-01-01

    For seven years, the EROS-2 project obtained a mass of photometric data on variable stars. We present a peculiar Cepheid-like star, in the direction of the Small Magellanic Cloud, which demonstrates unusual photometric behaviour over a short time interval. We to report on data of the photometriy acquired by the MARLY telescope and spectroscopy from the EFOSC instrument for this star, called EROS2 J005135-714459(sm0060n13842), which resembles the unusual Cepheid HR 7308. The light curve of our target is analysed using the Analysis of Variance method to determine a pulsational period of 5.5675 days. A fit of time-dependent Fourier coefficients is performed and a search for proper motion is conducted. The light curve exhibits a previously unobserved and spectacular change in both mean magnitude and amplitude, which has no clear theoretical explanation. Our analysis of the spectrum implies a radial velocity of 104 km s$^{-1}$ and a metallicity of -0.4$\\pm$0.2 dex. In the direction of right ascension, we measure a...

  2. Galactic kinematics derived from classical cepheids

    Science.gov (United States)

    Zhu, Zi

    On the basis of radial velocity and Hipparcos proper motion data, we have analyzed the galactic kinematics of classical Cepheids. Using the 3-D Ogorodnikov-Milne model we have determined the rotational velocity of the Galaxy to be V0 = 240.5 ± 10.2 km/s, on assuming a glactocentric distance of the Sun of R0 = 8.5 kpc. The results clearly indicate a contracting motion in the solar neighbourhood of (∂V θ∂θ)/R = -2.60 ± 1.07 km s -1 kpc -1, along the direction of galactic rotation. Possible reason for this motion is discussed. The solar motion found here is S⊙ = 18.78 ± 0.86 km/s in the direction l⊙ = 54.4° ± 2.9° and b⊙ = +26.6° ± 2.6°.

  3. Stellar variability in open clusters . II. Discovery of a new period-luminosity relation in a class of fast-rotating pulsating stars in NGC 3766

    Science.gov (United States)

    Mowlavi, N.; Saesen, S.; Semaan, T.; Eggenberger, P.; Barblan, F.; Eyer, L.; Ekström, S.; Georgy, C.

    2016-10-01

    Context. Pulsating stars are windows to the physics of stars enabling us to see glimpses of their interior. Not all stars pulsate, however. On the main sequence, pulsating stars form an almost continuous sequence in brightness, except for a magnitude range between δ Scuti and slowly pulsating B stars. Against all expectations, 36 periodic variables were discovered in 2013 in this luminosity range in the open cluster NGC 3766, the origins of which was a mystery. Aims: We investigate the properties of those new variability class candidates in relation to their stellar rotation rates and stellar multiplicity. Methods: We took multi-epoch spectra over three consecutive nights using ESO's Very Large Telescope. Results: We find that the majority of the new variability class candidates are fast-rotating pulsators that obey a new period-luminosity relation. We argue that the new relation discovered here has a different physical origin to the period-luminosity relations observed for Cepheids. Conclusions: We anticipate that our discovery will boost the relatively new field of stellar pulsation in fast-rotating stars, will open new doors for asteroseismology, and will potentially offer a new tool to estimate stellar ages or cosmic distances. Based on observations made with the FLAMES instruments on the VLT/UT2 telescope at the Paranal Observatory, Chile, under the program ID 69.A-0123(A).

  4. V473 Lyrae, a unique second-overtone Cepheid with two modulation cycles

    CERN Document Server

    Molnár, László

    2014-01-01

    V473 Lyrae is the only Galactic Cepheid with confirmed periodic amplitude and phase variations similar to the Blazhko effect observed in RR Lyrae stars. We collected all available photometric data and some radial velocity measurements to investigate the nature of the modulation. The comparison of the photometric and radial velocity amplitudes confirmed that the star pulsates in the second overtone. The extensive data set, spanning more than 40 years, allowed us to detect a secondary modulation cycle with a period of approximately 5300 days or 14.5 years. The secondary variations can be detected in the period of the primary modulation, as well. Phenomenologically, the light variations are analogous to the Blazhko effect. To find a physical link, we calculated linear hydrodynamic models to search for potential mode resonances that could drive the modulation and found two viable half-integer (n:2) and three n:4 resonances between the second overtone and other modes. If any of these resonances will be confirmed b...

  5. Polaris the Cepheid returns: 4.5 years of monitoring from ground and space

    CERN Document Server

    Bruntt, H; Stello, D; Penny, A J; Eaton, J A; Buzasi, D L; Sasselov, D D; Preston, H L; Miller-Ricci, E

    2008-01-01

    We present the analysis of 4.5 years of nearly continuous observations of the classical Cepheid Polaris, which comprise the most precise data available for this star. We have made spectroscopic measurements from ground and photometric measurements from the WIRE star tracker and the SMEI instrument on the Coriolis satellite. Measurements of the amplitude of the dominant oscillation (P = 4 days), that go back more than a century, show a decrease from 120 mmag to 30 mmag (V magnitude) around the turn of the millennium. It has been speculated that the reason for the decrease in amplitude is the evolution of Polaris towards the edge of the instability strip. However, our new data reveal an increase in the amplitude by about 30% from 2003-2006. It now appears that the amplitude change is cyclic rather than monotonic, and most likely the result of a pulsation phenomenon. In addition, previous radial velocity campaigns have claimed the detection of long-period variation in Polaris (P > 40 days). Our radial velocity d...

  6. Period-Luminosity Relations Derived From the OGLE-III Fundamental Mode Cepheids II: The Small Magellanic Cloud Cepheids

    CERN Document Server

    Ngeow, Chow-Choong; Bhardwaj, Anupam; Singh, Harinder P

    2015-01-01

    In this paper we present multi-band period-luminosity (P-L) relations for fundamental mode Cepheids in the SMC. The optical VI-band mean magnitudes for these SMC Cepheids were taken from the third phase of the Optical Gravitational Lensing Experiment (OGLE-III) catalog. We also matched the OGLE-III SMC Cepheids to 2MASS and SAGE-SMC catalog to derive mean magnitudes in the JHK-bands and the four {\\it Spitzer} IRAC bands, respectively. All photometry was corrected for extinction by adopting the Zaritsky's extinction map. Cepheids with periods smaller than $\\sim2.5$ days were removed from the sample. In addition to the extinction corrected P-L relations in nine filters from optical to infrared, we also derived the extinction-free Wesenheit function for these Cepheids. We tested the nonlinearity of these SMC P-L relations (except the $8.0\\mu\\mathrm{m}$-band P-L relation) at 10 days: none of the P-L relations show statistically significant evidence of nonlinearity. When compared to the P-L relations in the LMC, t...

  7. PULSATION PERIOD VARIATIONS IN THE RRc LYRAE STAR KIC 5520878

    International Nuclear Information System (INIS)

    Learned et al. proposed that a sufficiently advanced extra-terrestrial civilization may tickle Cepheid and RR Lyrae variable stars with a neutrino beam at the right time, thus causing them to trigger early and jogging the otherwise very regular phase of their expansion and contraction. This would turn these stars into beacons to transmit information throughout the galaxy and beyond. The idea is to search for signs of phase modulation (in the regime of short pulse duration) and patterns, which could be indicative of intentional, omnidirectional signaling. We have performed such a search among variable stars using photometric data from the Kepler space telescope. In the RRc Lyrae star KIC 5520878, we have found two such regimes of long and short pulse durations. The sequence of period lengths, expressed as time series data, is strongly autocorrelated, with correlation coefficients of prime numbers being significantly higher (p = 99.8%). Our analysis of this candidate star shows that the prime number oddity originates from two simultaneous pulsation periods and is likely of natural origin. Simple physical models elucidate the frequency content and asymmetries of the KIC 5520878 light curve. Despite this SETI null result, we encourage testing of other archival and future time-series photometry for signs of modulated stars. This can be done as a by-product to the standard analysis, and can even be partly automated

  8. PULSATION PERIOD VARIATIONS IN THE RRc LYRAE STAR KIC 5520878

    Energy Technology Data Exchange (ETDEWEB)

    Hippke, Michael [Institute for Data Analysis, Luiter Str. 21b, D-47506 Neukirchen-Vluyn (Germany); Learned, John G. [High Energy Physics Group, Department of Physics and Astronomy, University of Hawaii, Manoa 327 Watanabe Hall, 2505 Correa Road, Honolulu, HI 96822 (United States); Zee, A. [Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States); Edmondson, William H. [School of Computer Science, University of Birmingham, Birmingham B15 2TT (United Kingdom); Lindner, John F. [Physics Department, The College of Wooster, Wooster, OH 44691 (United States); Kia, Behnam; Ditto, William L. [Department of Physics and Astronomy, University of Hawai' i at Mānoa, Honolulu, HI 96822 (United States); Stevens, Ian R., E-mail: hippke@ifda.eu, E-mail: jgl@phys.hawaii.edu, E-mail: zee@kitp.ucsb.edu, E-mail: w.h.edmondson@bham.ac.uk, E-mail: jlindner@wooster.edu, E-mail: wditto@hawaii.edu, E-mail: behnam@hawaii.edu, E-mail: irs@star.sr.bham.ac.uk [School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT (United Kingdom)

    2015-01-01

    Learned et al. proposed that a sufficiently advanced extra-terrestrial civilization may tickle Cepheid and RR Lyrae variable stars with a neutrino beam at the right time, thus causing them to trigger early and jogging the otherwise very regular phase of their expansion and contraction. This would turn these stars into beacons to transmit information throughout the galaxy and beyond. The idea is to search for signs of phase modulation (in the regime of short pulse duration) and patterns, which could be indicative of intentional, omnidirectional signaling. We have performed such a search among variable stars using photometric data from the Kepler space telescope. In the RRc Lyrae star KIC 5520878, we have found two such regimes of long and short pulse durations. The sequence of period lengths, expressed as time series data, is strongly autocorrelated, with correlation coefficients of prime numbers being significantly higher (p = 99.8%). Our analysis of this candidate star shows that the prime number oddity originates from two simultaneous pulsation periods and is likely of natural origin. Simple physical models elucidate the frequency content and asymmetries of the KIC 5520878 light curve. Despite this SETI null result, we encourage testing of other archival and future time-series photometry for signs of modulated stars. This can be done as a by-product to the standard analysis, and can even be partly automated.

  9. [Bachelard and the mathematical pulsation].

    Science.gov (United States)

    Guitart, René

    2015-01-01

    The working mathematician knows a specific gesture named « mathematical pulsation », a necessary creative moving in diagrams of thoughts and interpretations of mathematical writings. In this perspective the fact of being an object is definitely undecided, and related to the game of relations. The purpose of this paper today is to construct this pulsation, starting from the epistemology of Bachelard, concerning mathematics as well as mathematical physics. On the way, we recover links between ideas of Bachelard and more recent specific propositions by Gilles Ch-let, Charles Alunni, or René Guitart. Also are used authors like Jacques Lacan, Arthur Koestler, Alfred N. Whitehead, Charles S. Peirce. We conclude that the mathematical work consists with pulsative moving in the space of diagrams; we claim that this view is well compatible with the Bachelard's analysis of scientific knowledge: the intellectual or formal mathematical data preceeds the empirical objects, and in some sense these objects result from the pulsative gestures of the thinkers. So we finish with a categorical scheme of the pulsation. PMID:26223414

  10. [Bachelard and the mathematical pulsation].

    Science.gov (United States)

    Guitart, René

    2015-01-01

    The working mathematician knows a specific gesture named « mathematical pulsation », a necessary creative moving in diagrams of thoughts and interpretations of mathematical writings. In this perspective the fact of being an object is definitely undecided, and related to the game of relations. The purpose of this paper today is to construct this pulsation, starting from the epistemology of Bachelard, concerning mathematics as well as mathematical physics. On the way, we recover links between ideas of Bachelard and more recent specific propositions by Gilles Ch-let, Charles Alunni, or René Guitart. Also are used authors like Jacques Lacan, Arthur Koestler, Alfred N. Whitehead, Charles S. Peirce. We conclude that the mathematical work consists with pulsative moving in the space of diagrams; we claim that this view is well compatible with the Bachelard's analysis of scientific knowledge: the intellectual or formal mathematical data preceeds the empirical objects, and in some sense these objects result from the pulsative gestures of the thinkers. So we finish with a categorical scheme of the pulsation.

  11. Nonlinear pulsations of luminous He stars

    International Nuclear Information System (INIS)

    Radial pulsations in models of R Cor Bor stars and BD + 104381 have been studied with a nonlinear hydrodynamic pulsation code. Comparisons are made with previous calculations and with observed light and velocity curves. 13 refs., 2 tabs

  12. Pulsations of delta Scuti stars

    International Nuclear Information System (INIS)

    A general review of the pulsating δ Scuti variables is given including the observed light curves and positions of the stars in the Hertzsprung-Russell diagram. Theoretical interpretations from evolution and pulsation calculations give their masses, radii, luminosities, and even their approximate internal compositions. Three models of these stars are discussed and used to study the nonlinear hydrodynamic behavior of these stars. The hydrodynamic equations and the Stellingwerf method for obtaining strictly periodic solutions are outlined. Problems of allowing for time-dependent convection and its great sensitivity to temperature and density are presented. Tentative results to date do not show any tendency for amplitudes to grow to large unobserved amplitudes, in disagreement with an earlier suggestion by Stellingwerf. It is found that the very small growth rates of the pulsations may even be too small to be useful in seeking a periodic solution. 15 refs., 8 figs., 3 tabs

  13. Line-profile variations in pulsating subdwarf-B stars as a pulsation mode diagnostic

    OpenAIRE

    Schoenaers, C.; Lynas-Gray, A. E.

    2005-01-01

    In previous attempts to perform seismic modelling of pulsating subdwarf-B stars, various mode identification techniques are used with uncertain results. We investigated a method so far neglected in sdB stars, but very successful for Main Sequence pulsators, that is, mode identification from the line-profile variations caused by stellar pulsation. We report the calculation of time-resolved synthetic spectra for sdB stars pulsating with various combinations of pulsation modes; these calculation...

  14. New Pulsating DB White Dwarf Stars from the Sloan Digital Sky Survey

    CERN Document Server

    Nitta, A; Krzesínski, J; Kepler, S O; Metcalfe, T S; Mukadam, Anjum S; Mullally, Fergal; Nather, R E; Sullivan, Denis J; Thompson, Susan E; Winget, D E

    2008-01-01

    We are searching for new He atmosphere white dwarf pulsators (DBVs) based on the newly found white dwarf stars from the spectra obtained by the Sloan Digital Sky Survey. DBVs pulsate at hotter temperature ranges than their better known cousins, the H atmosphere white dwarf pulsators (DAVs or ZZ Ceti stars). Since the evolution of white dwarf stars is characterized by cooling, asteroseismological studies of DBVs give us opportunities to study white dwarf structure at a different evolutionary stage than the DAVs. The hottest DBVs are thought to have neutrino luminosities exceeding their photon luminosities (Winget et al. 2004), a quantity measurable through asteroseismology. Therefore, they can also be used to study neutrino physics in the stellar interior. So far we have discovered nine new DBVs, doubling the number of previously known DBVs. Here we report the new pulsators' lightcurves and power spectra.

  15. The Effective Temperatures, Radii and Masses of Dwarf Cepheids

    Science.gov (United States)

    Kim, Chulhee

    1996-02-01

    Using the flux values determined with the infrared flux method (IRFM) developed by Blackwell and Lynas-Gray (1993), we derived the empirical relationship between flux (F v ) and (V — K) colour appropriate to Dwarf Cepheids. For three Dwarf Cepheids CY Aqr, YZ Boo and SZ Lyn where both VK photometry and radial velocities were available from the literature, effective temperatures were determined using the intrinsic Strömgren indices, model atmosphere grids for (V — K) and the relation between temperature and (V — K) colour. Then, by applying the infrared surface brightness method, radii and distances and hence masses and absolute magnitudes were estimated with effective temperatures determined by three different methods. It was found that the average mass of these variables is about 0.5 solar mass and this result supports the hypothesis that Dwarf Cepheids are pre-white dwarf objects. It was also confirmed that the temperatures determined with the IRFM are most successful in the application of the surface brightness method to the radius estimation of Dwarf Cepheids.

  16. The period distribution of Cepheids: a test of stellar evolution

    Directory of Open Access Journals (Sweden)

    Groenewegen M.A.T.

    2015-01-01

    Full Text Available The period distributions of classical Cepheids in the Small and Large Magellanic Cloud are quite different. Using the TRILEGAL population synthesis code and a theoretical instability strip the ultimate aim is to understand these differences quantitatively. First results are presented for one area in the LMC using VMC NIR data.

  17. The Scale of Reddening for Classical Cepheid Variables

    CERN Document Server

    Turner, David G

    2016-01-01

    Field reddenings are summarized for 68 Cepheids from published studies and updated results presented here. The compilation forms the basis for a comparison with other published reddening scales of Cepheids, including those established from reddening-independent indices, photometry on the Lick six-color system, Str\\"{o}mgren system, Walraven system, Washington system, Cape $BVI$ system, DDO system, and Geneva system, IRSB studies, and Cepheid spectroscopy, both old and new. Reddenings tied to period-color relations are the least reliable, as expected, while photometric color excesses vary in precision, their accuracy depending on the methodology and calibration sample. The tests provide insights into the accuracy and precision of published Cepheid reddening scales, and lead to a new system of standardized reddenings comprising a sample of 198 variables with an average uncertainty of $\\pm0.028$ in E$_{B-V}$, the precision being less than $\\pm0.01$ for many. The collected color excesses are used to map the dispe...

  18. Pulsational-Pair Instability Supernovae

    CERN Document Server

    Woosley, S E

    2016-01-01

    The final evolution of stars in the mass range 60 - 150 solar masses is explored. Depending upon their mass loss and rotation rates, many of these stars will end their lives as pulsational pair-instability supernovae. Even a non-rotating 70 solar mass star is pulsationally unstable during oxygen shell burning and can power a sub-luminous supernova. Rotation decreases the limit further. For more massive stars, the pulsations are less frequent, span a longer time, and are more powerful. Violent pulsations eject not only any residual low density envelope, but also that fraction of the helium core mass outside about 35 - 50 solar masses. The remaining core of helium and heavy elements continues to evolve, ultimately forming an iron core of about 2.5 solar masses that probably collapses to a black hole. A variety of observational transients result with total durations ranging from days to 10,000 years, and luminosities from 10$^{41}$ to 10$^{44}$ erg s$^{-1}$. Many transients resemble ordinary Type IIp supernovae,...

  19. Galactic abundance gradients from Cepheids : On the iron abundance gradient around 10-12 kpc

    OpenAIRE

    Lemasle, B.; Francois, P.; Piersimoni, A.; Pedicelli, S.; Bono, G.; Laney, C. D.; Primas, F.; Romaniello, M.

    2008-01-01

    Context: Classical Cepheids can be adopted to trace the chemical evolution of the Galactic disk since their distances can be estimated with very high accuracy. Aims: Homogeneous iron abundance measurements for 33 Galactic Cepheids located in the outer disk together with accurate distance determinations based on near-infrared photometry are adopted to constrain the Galactic iron gradient beyond 10 kpc. Methods: Iron abundances were determined using high resolution Cepheid spectra collected wit...

  20. Study of the cepheid distribution in the LMC by the Meads method

    International Nuclear Information System (INIS)

    The distribution of the cepheids in the LMC was studied by the Meads analysis. All cepheids and the group of stars with lgP=0.4-0.69 have the scale of non-uniformity about 700-1400 pk. The cepheids in the regions of the bar have the scale of non-uniformity ≅200pk. This scale was also obtained by the correlation analysis

  1. Vetting Galactic Leavitt Law Calibrators using Radial Velocities: On the Variability, Binarity, and Possible Parallax Error of 19 Long-period Cepheids

    CERN Document Server

    Anderson, R I; Riess, A G; Melis, C; Holl, B; Semaan, T; Papics, P I; Blanco-Cuaresma, S; Eyer, L; Mowlavi, N; Palaversa, L; Roelens, M

    2016-01-01

    We investigate the radial velocity (RV) variability and spectroscopic binarity of 19 Galactic long-period ($P_{\\rm{puls}} \\gtrsim 10$ d) classical Cepheid variable stars whose trigonometric parallaxes are being measured using the Hubble Space Telescope and Gaia. Our primary objective is to constrain possible parallax error due to undetected orbital motion. Using $>1600$ high-precision RVs measured between 2011 and 2016, we find no indication of orbital motion on $\\lesssim 5$ yr timescales for 18 Cepheids and determine upper limits on allowed configurations for a range of input orbital periods. The results constrain the unsigned parallax error due to orbital motion to $ 10$ yr) variations in pulsation-averaged velocity $v_\\gamma$ via a template fitting approach using both new and literature RVs. We discover the spectroscopic binarity of XZ Car and CD Cyg, find first tentative evidence for AQ Car, and reveal KN Cen's orbital signature. Further (mostly tentative) evidence of time-variable $v_\\gamma$ is found for...

  2. Pulsating Helium Atmosphere White Dwarfs

    Science.gov (United States)

    Provencal, Judith; Montgomery, Michael H.; Bischoff-Kim, Agnes; Shipman, Harry; Nitta, Atsuko; Whole Earth Telescope Collaboration

    2015-08-01

    The overwhelming majority of all stars currently on the main sequence as well as those from earlier generations will or have ended their stellar lives as white dwarf stars. White dwarfs are rich forensic laboratories linking the history and future evolution of our Galaxy. Their structure and atmospheric composition provide evidence of how the progenitors lived, how they evolved, and how they died. This information reveals details of processes governing the behavior of contemporary main sequence stars. Combined with their distribution in luminosity/temperature, white dwarfs strongly constrain models of galactic and cosmological evolution.GD358 is among the brightest (mv =13.7) and best studied of the pulsating white dwarfs. This helium atmoshere pulsator (DBV) has an extensive photometric database spanning 30 years, including nine multisite Whole Earth Telescope campaigns. GD358 exhibits a range of behaviors, from drastic changes in excited pulsation modes to variable multiplet splittings. We use GD358 as a template for an examination of the DBV class, combining photometric results with recent COS spectroscopy. The results present new questions concerning DB formation and evolution.

  3. Why do hot subdwarf stars pulsate?

    CERN Document Server

    Geier, S

    2015-01-01

    Hot subdwarf B stars (sdBs) are the stripped cores of red giants located at the bluest extension of the horizontal branch. Several different kinds of pulsators are found among those stars. The mechanism that drives those pulsations is well known and the theoretically predicted instability regions for both the short-period p-mode and the long-period g-mode pulsators match the observed distributions fairly well. However, it remains unclear why only a fraction of the sdB stars pulsate, while stars with otherwise very similar parameters do not show pulsations. From an observers perspective I review possible candidates for the missing parameter that makes sdB stars pulsate or not.

  4. Pulsating variable stars in the Magellanic Clouds

    OpenAIRE

    Clementini, Gisella

    2009-01-01

    Pulsating variable stars can be powerful tools to study the structure, formation and evolution of galaxies. I discuss the role that the Magellanic Clouds' pulsating variables play in our understanding of the whole Magellanic System, in light of results on pulsating variables produced by extensive observing campaigns like the MACHO and OGLE microlensing surveys. In this context, I also briefly outline the promise of new surveys and astrometric missions which will target the Clouds in the near ...

  5. Line-profile variations in pulsating subdwarf-B stars as a pulsation mode diagnostic

    CERN Document Server

    Schoenaers, C

    2005-01-01

    In previous attempts to perform seismic modelling of pulsating subdwarf-B stars, various mode identification techniques are used with uncertain results. We investigated a method so far neglected in sdB stars, but very successful for Main Sequence pulsators, that is, mode identification from the line-profile variations caused by stellar pulsation. We report the calculation of time-resolved synthetic spectra for sdB stars pulsating with various combinations of pulsation modes; these calculations were carried out over appropriate ranges of effective temperature, surface gravity and helium abundances. Preliminary tests using these synthetic line-profile variations demonstrated their potential for mode identification by comparison with observation.

  6. First Kepler results on compact pulsators - I. Survey target selection and the first pulsators

    DEFF Research Database (Denmark)

    Østensen, Roy H.; Silvotti, Roberto; Charpinet, S.;

    2010-01-01

    We present results from the first two quarters of a survey to search for pulsations in compact stellar objects with the Kepler spacecraft. The survey sample and the various methods applied in its compilation are described, and spectroscopic observations are presented to separate the objects into...... accurate classes. From the Kepler photometry we clearly identify nine compact pulsators and a number of interesting binary stars. Of the pulsators, one shows the strong, rapid pulsations typical of a V361 Hya-type sdB variable (sdBV); seven show long-period pulsation characteristics of V1093 Her-type sd...

  7. Population I Cepheids and understanding star formation history of the Small Magellanic Cloud

    International Nuclear Information System (INIS)

    In this paper, we study the age and spatial distributions of Cepheids in the Small Magellanic Cloud (SMC) as a function of their ages using data from the OGLE III photometric catalogue. A period - age relation derived for Classical Cepheids in the Large Magellanic Cloud (LMC) has been used to find the ages of Cepheids. The age distribution of the SMC Classical Cepheids is found to have a peak at log(Age) = 8.40 ± 0.10 which suggests that a major star formation event might have occurred in the SMC about 250 ± 50 Myr ago. It is believed that this star forming burst had been triggered by close interactions of the SMC with the LMC and/or the Milky Way. A comparison of the observed spatial distributions of the Cepheids and open star clusters has also been carried out to study the star formation scenario in the SMC. (paper)

  8. Comparison of multi-band period-luminosity relations for classical Cepheids in the Magellanic Clouds

    Science.gov (United States)

    Ngeow, Chow-Choong; Kanbur, Shashi M.

    2016-07-01

    The period-luminosity (PL) relation for classical fundamental mode Cepheids (hereafter Cepheids) is an important astrophysical tool in distance scale applications. Because of this, we initiated a program to derive multi-band PL relations with Cepheids in the Large and Small Magellanic Cloud (hereafter LMC and SMC, respectively), as there are ∼⃒ 103 Cepheids found in these two nearby galaxies. When compared the slopes of the multi-band PL relations for Cepheids in the LMC and SMC, we found that these PL slopes agree with each others except in the V and J band. We also found an excellent agreement of the PL slopes in Wesenheit function, hence we calibrated the Period-Wesenheit (PW) relation by combining the data from both Clouds, together with an accurate LMC distance based on measurement from late-type eclipsing binaries. Our calibrated Wesenheit function is MW = — 3.314 log(P) — 2.601.

  9. C, N, O, and Na Abundances of Cepheid Variables: Implications on the Mixing Process in the Envelope

    CERN Document Server

    Takeda, Y; Han, I; Lee, B -C; Kim, K -M

    2013-01-01

    With an aim of investigating the nature of evolution-induced mixing in the envelope of evolved intermediate-mass stars, we carried out an extensive spectroscopic study for 12 Cepheid variables of various pulsation periods (~2-16 days) to determine the photospheric abundances of C, N, O, and Na, which are the key elements for investigating how the H-burning products are salvaged from the interior, based on 122 high-dispersion echelle spectra (~10 per target) of wide wavelength coverage collected at Bohyunsan Astronomical Observatory. Having established the relevant atmospheric parameters corresponding to each phase spectroscopically from the equivalent widths of Fe I and Fe II lines, we derived C, N, O, and Na abundances from C I, O I, N I, and Na I lines by using the spectrum-synthesis fitting technique, while taking into account the non-LTE effect. The resulting abundances of these elements for 12 program stars turned out to show remarkably small star-to-star dispersions (<~0.1-0.2dex) without any signifi...

  10. Discovery of Cycle-to-cycle Modulated Spectral Line Variability and Velocity Gradients in Long-period Cepheids

    CERN Document Server

    Anderson, Richard I

    2016-01-01

    This work reports the discovery of cycle-to-cycle modulated spectral line and atmospheric velocity gradient variability in long-period Cepheids based on 925 high-resolution optical spectra of $\\ell$ Carinae (P $\\sim$ 35.5 d) recorded during three heavy duty-cycle monitoring campaigns (in 2014, 2015, and 2016). Spectral line variability is investigated via cross-correlation functions (CCFs) computed using three sets of spectral lines (weak, solar, strong). A metallic line velocity gradient, {\\delta}v$_r$ (t), is computed as the difference between weak and strong-line RVs. CCF shape indicators BIS (asymmetry), FWHM, and depth all exhibit clear phase-dependent variability patterns that differ from one pulsation cycle to the next. Weak-line CCFs exhibit these effects more clearly than strong-line CCFs. BIS exhibits the most peculiar modulated variability and can be used to identify the presence of cycle-to-cycle modulated line profile variations. {\\delta}v$_r$ (t) clearly exhibits cycle-to-cycle differences that ...

  11. Enhancements of Impinging Flame by Pulsation

    Institute of Scientific and Technical Information of China (English)

    AySu; Ying-ChiehLiu

    2000-01-01

    Experimental investigations on the pulsating jet-impinging diffusion flame were executed.A soleoid valve was aligned upstream of the jet orifice and the methane fuel was controlled in open-closed cycles from 0 Hz to 20Hz.Results show that the open-closed cycles,indeed increase the fluctuations of the methane fuel obviously.The evolutions of pulsating flame therefore develop faster than the continuous impinging flame.The optimized pulating frequencies are near 9 to 11 hz from the Re=170 to 283.The temperature differences between that under optimized pulsating rate and full open condition(no pulsation)are ranging from 100 to 150 degree.The pulsating effect is more singnificant at low Reynolds number.The cross section of continuous impinging flame behaves as elliptic shape with axial ratio equals to 2/3.The tip of the impinging flame obviously crosses at 42mm above the impinging point.ecause of the phenomenon of pulsation flame,the flame sheet or flame front may not be identified clearly in the averaged temperature contours.Results shows that the averaged end-contour of pulsation flame rears at 38mm above the impinging point.By observation and experiment,the pulsating flame behaves more stable and efficient than the continuous impinging flame.

  12. Self-pulsation in Raman fiber amplifiers

    DEFF Research Database (Denmark)

    Pedersen, Martin Erland Vestergaard; Ott, Johan Raunkjær; Rottwitt, Karsten

    2009-01-01

    Dynamic behavior caused by Brillouin scattering in Raman fiber amplifiers is studied. Modes of self-pulsation steady state oscillations are found. Their dependence on amplification scheme is demonstrated.......Dynamic behavior caused by Brillouin scattering in Raman fiber amplifiers is studied. Modes of self-pulsation steady state oscillations are found. Their dependence on amplification scheme is demonstrated....

  13. A Planet Found by Pulsations

    Science.gov (United States)

    Kohler, Susanna

    2016-10-01

    Searching for planets around very hot stars is much more challenging than looking around cool stars. For this reason, the recent discovery of a planet around a main-sequence A star is an important find both because of its unique position near the stars habitable zone, and because of the way in which the planet was discovered.Challenges in VariabilityIn the past three decades, weve discovered thousands of exoplanets yet most of them have been found around cool stars (like M dwarfs) or moderate stars (like G stars like our Sun). Very few of the planets that weve found orbit hot stars; in fact, weve only discovered ~20 planets orbiting the very hot, main-sequence A stars.The instability strip, indicated on an H-R diagram. Stellar classification types are listed across the bottom of the diagram. Many main-sequence A stars reside in the instability strip. [Rursus]Why is this? We dont expect that main-sequence A stars host fewer planets than cooler stars. Instead, its primarily because the two main techniques that we use to find planets namely, transits and radial velocity cant be used as effectively on the main-sequence A stars that are most likely to host planets, because the luminosities of these stars are often variable.These stars can lie on whats known as the classical instability strip in the Herzsprung-Russell diagram. Such variable stars pulsate due to changes in the ionization state of atoms deep in their interiors, which causes the stars to puff up and then collapse back inward. For variable main-sequence A stars, the periods for these pulsations can be several to several tens of times per day.These very pulsations that make transits and radial-velocity measurements so difficult, however, can potentially be used to detect planets in a different way. Led by Simon Murphy (University of Sydney, Australia and Aarhus University, Denmark), a team of scientists has recently detected the first planet ever to be discovered around a main-sequence A star from the timing

  14. A study of the pulsation driving mechanism in pulsating combustors

    Science.gov (United States)

    Goldman, Y.; Timnat, Y. M.

    Experiments performed in a facility consisting of a Schmidt-type pulsating combustor, in which high-speed photographs were taken and pressure, temperature and gas composition measured, showed that the air supply conditions at the inlet and the volume of the combustor strongly influence the oscillation frequency. From the measurements, the existence of two separate regions, one containing cold air and the other containing fuel-rich gas, was found, and a pressure-volume diagram was drawn, showing the effect of chemical energy release and heat supply during the compression stroke and differentiating it from the expansion. A model of the interaction between the cyclic combustion process and the acoustic oscillations of the gas volume within the chamber and the tail-pipe is presented. The conditions for chemical energy release that result in high-pressure amplitude are described.

  15. Empirical Period-Color and Amplitude-Color Relations for Classical Cepheids and RR Lyrae Variables

    CERN Document Server

    Bhardwaj, Anupam; Singh, Harinder P; Ngeow, Chow-Choong

    2014-01-01

    We analyze Galactic, Large Magellanic Cloud and Small Magellanic Cloud Cepheids and RR Lyrae variables in terms of period-color (PC) and amplitude-color (AC) diagrams at the phases of maximum and minimum light. We compiled Galactic Cepheids $V$- and $I$-band data from the literature. We make use of optical bands light curve data from OGLE-III survey for Cepheids and RR Lyrae variables in the Magellanic Clouds. We apply the $F$-statistical test to check the significance of any variation in the slope of PC and AC relations for Cepheid variables. The PC relation at maximum light for Galactic Cepheids with periods longer than about 7 days is shallow and the corresponding AC relation is flat for the entire period range. For the fundamental mode Cepheids in the Magellanic Clouds, we find significant breaks in the PC and AC relations at both maximum and minimum light for periods around 10 days. The PC relation at maximum light for the Magellanic Clouds is flat for Cepheids with periods greater than 10 days. First ov...

  16. Assessing potential cluster Cepheids from a new distance and reddening parameterization and 2MASS photometry

    CERN Document Server

    Majaess, Daniel J; Lane, David J

    2008-01-01

    A framework is outlined to assess Cepheids as potential cluster members from readily available photometric observations. A relationship is derived to estimate colour excess and distance for individual Cepheids through a calibration involving recently published HST parallaxes and a cleaned sample of established cluster Cepheids. Photometric (V-J) colour is found to be a viable parameter for approximating a Cepheid's reddening. The non-universal nature of the slope of the Cepheid PL relation for BV photometry is confirmed. By comparison, the slopes of the VJ and VI relations seem relatively unaffected by metallicity. A new Galactic Cepheid confirmed here, GSC 03729-01127 (F6-G1 Ib), is sufficiently coincident with the coronal regions of Tombaugh 5 to warrant follow-up radial velocity measures to assess membership. CCD photometry and O--C diagrams are presented for GSC 03729-01127 and the suspected cluster Cepheids AB Cam and BD Cas. Fourier analysis of the photometry for BD Cas and recent estimates of its metal...

  17. Resolved Companions of Cepheids: Testing the Candidates with X-Ray Observations

    Science.gov (United States)

    Evans, Nancy Remage; Pillitteri, Ignazio; Wolk, Scott; Karovska, Margarita; Tingle, Evan; Guinan, Edward; Engle, Scott; Bond, Howard E.; Schaefer, Gail H.; Mason, Brian D.

    2016-04-01

    We have made XMM-Newton observations of 14 Galactic Cepheids that have candidate resolved (≥5″) companion stars based on our earlier HST Wide Field Camera 3 (WFC3) imaging survey. Main-sequence stars that are young enough to be physical companions of Cepheids are expected to be strong X-ray producers in contrast to field stars. XMM-Newton exposures were set to detect essentially all companions hotter than spectral type M0 (corresponding to 0.5 M⊙). The large majority of our candidate companions were not detected in X-rays, and hence are not confirmed as young companions. One resolved candidate (S Nor #4) was unambiguously detected, but the Cepheid is a member of a populous cluster. For this reason, it is likely that S Nor #4 is a cluster member rather than a gravitationally bound companion. Two further Cepheids (S Mus and R Cru) have X-ray emission that might be produced by either the Cepheid or the candidate resolved companion. A subsequent Chandra observation of S Mus shows that the X-rays are at the location of the Cepheid/spectroscopic binary. R Cru and also V659 Cen (also X-ray bright) have possible companions closer than 5″ (the limit for this study) which are the likely sources of X-rays. One final X-ray detection (V473 Lyr) has no known optical companion, so the prime suspect is the Cepheid itself. It is a unique Cepheid with a variable amplitude. The 14 stars that we observed with XMM constitute 36% of the 39 Cepheids found to have candidate companions in our HST/WFC3 optical survey. No young probable binary companions were found with separations of ≥5″ or 4000 au. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).

  18. RESOLVED COMPANIONS OF CEPHEIDS: TESTING THE CANDIDATES WITH X-RAY OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Evans, Nancy Remage; Pillitteri, Ignazio; Wolk, Scott; Karovska, Margarita; Tingle, Evan [Smithsonian Astrophysical Observatory, MS 4, 60 Garden St., Cambridge, MA 02138 (United States); Guinan, Edward; Engle, Scott [Department of Astronomy and Astrophysics, Villanova University, 800 Lancaster Ave., Villanova, PA 19085 (United States); Bond, Howard E. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Schaefer, Gail H. [The CHARA Array of Georgia State University, Mount Wilson, California 91023 (United States); Mason, Brian D., E-mail: nevans@cfa.harvard.edu, E-mail: heb11@psu.edu, E-mail: schaefer@chara-array.org [US Naval Observatory, 3450 Massachusetts Ave., NW, Washington, DC 20392-5420 (United States)

    2016-04-15

    We have made XMM-Newton observations of 14 Galactic Cepheids that have candidate resolved (≥5″) companion stars based on our earlier HST Wide Field Camera 3 (WFC3) imaging survey. Main-sequence stars that are young enough to be physical companions of Cepheids are expected to be strong X-ray producers in contrast to field stars. XMM-Newton exposures were set to detect essentially all companions hotter than spectral type M0 (corresponding to 0.5 M{sub ⊙}). The large majority of our candidate companions were not detected in X-rays, and hence are not confirmed as young companions. One resolved candidate (S Nor #4) was unambiguously detected, but the Cepheid is a member of a populous cluster. For this reason, it is likely that S Nor #4 is a cluster member rather than a gravitationally bound companion. Two further Cepheids (S Mus and R Cru) have X-ray emission that might be produced by either the Cepheid or the candidate resolved companion. A subsequent Chandra observation of S Mus shows that the X-rays are at the location of the Cepheid/spectroscopic binary. R Cru and also V659 Cen (also X-ray bright) have possible companions closer than 5″ (the limit for this study) which are the likely sources of X-rays. One final X-ray detection (V473 Lyr) has no known optical companion, so the prime suspect is the Cepheid itself. It is a unique Cepheid with a variable amplitude. The 14 stars that we observed with XMM constitute 36% of the 39 Cepheids found to have candidate companions in our HST/WFC3 optical survey. No young probable binary companions were found with separations of ≥5″ or 4000 au.

  19. Pulsations in close binaries: challenges and opportunities

    Directory of Open Access Journals (Sweden)

    Maceroni C.

    2015-01-01

    Full Text Available CoRoT and Kepler provided a precious by-product: a number of eclipsing binaries containing variable stars and, among these, non-radial pulsators. This providential occurrence allows combining independent information from two different phenomena whose synergy yields scientific results well beyond those from the single sources. In particular, the analysis of pulsations in eclipsing binary components throws light on the internal structure of the pulsating star, on the system evolution, and on the role of tidal forces in exciting the oscillations. The case study of the Kepler target KIC 3858884 is illustrative of the difficulties of analysis and of the achievements in this rapidly developing field.

  20. Relativistic stellar pulsations in the Cowling approximation

    International Nuclear Information System (INIS)

    Much that is known about the general pulsational properties of non-rotating Newtonian stars is traceable to the fact that in the Cowling approximation, the stellar pulsation equations can be cast in a nearly Sturm-Liouville form. In this paper, the relativistic Cowling approximation is investigated, and it is shown that in this approximation the equations for non-radial relativistic stellar pulsations are also of nearly Sturm-Liouville character. The consequences of this are discussed as a series of theorems regarding the eigenfrequencies and eigenfunctions of g-, f- and p-modes in relativistic stars. (author)

  1. Relations of pulsatility index and particle residence time to the wall-shear-stress properties in pulsating flows with reverse flow phase

    CERN Document Server

    Kersh, Dikla

    2013-01-01

    Pulsating flows with a \\emph{total reverse flow} phase are ubiquitous in physiological systems in normal and pathological conditions. Irregularity of hemodynamic parameters in such flows is correlated with the appearance and development of several arterial pathologies. We study the relations between flow waveform parameters and the wall shear stress (WSS) related quantities such as mean, root-mean-square, gradient of WSS and the oscillating shear index. The phase-averaged velocity profiles measured by the digital particle image velocimetry are used to estimate WSS utilizing the Womersley pulsating flow model. In addition to the Reynolds and Womersley numbers, another dimensionless parameter, pulsating index (PI) which is the ratio of forward flow rate to the reverse flow rate is required. PI is essential for the complete description of the flow patterns with the total flow reversal. We demonstrate significant effects on the WSS quantities due to the pulsating frequency and PI. Furthermore, the particle reside...

  2. A Test of the Calibration of the Tully-Fisher Relation Using Cepheid and SNIa Distances

    OpenAIRE

    Shanks, T.

    1997-01-01

    We make a direct test of Tully-Fisher distance estimates to eleven spiral galaxies with HST Cepheid distances and to twelve spiral galaxies with SNIa distances. The HST Cepheid distances come from the work of Freedman (1997), Sandage et al (1996) and Tanvir et al (1995). The SNIa distances come from Pierce (1994), calibrated using the Cepheid results of Sandage et al (1996). The Tully-Fisher distances mostly come from the work of Pierce (1994). The results show that the Tully-Fisher distance ...

  3. Cepheid Period-Luminosity Relation from the AKARI Observations

    CERN Document Server

    Ngeow, Chow-Choong; Kanbur, Shashi M; Neilson, Hilding; Onaka, Takashi; Kato, Daisuke

    2010-01-01

    In this paper, we derive the period-luminosity (P-L) relation for Large Magellanic Cloud (LMC) Cepheids based on mid-infrared AKARI observations. AKARI's IRC sources were matched to the OGLE-III LMC Cepheid catalog. Together with the available I band light curves from the OGLE-III catalog, potential false matches were removed from the sample. This procedure excluded most of the sources in the S7 and S11 bands: hence only the P-L relation in the N3 band was derived in this paper. Random-phase corrections were included in deriving the P-L relation for the single epoch AKARI data, even though the derived P-L relation is consistent with the P-L relation without random-phase correction, though there is a \\sim 7 per-cent improvement in the dispersion of the P-L relation. The final adopted N3 band P-L relation is N3 = -3.246 log(P) + 15.844, with a dispersion of 0.149.

  4. Cepheid period-luminosity relation from the AKARI observations

    Science.gov (United States)

    Ngeow, Chow-Choong; Ita, Yoshifusa; Kanbur, Shashi M.; Neilson, Hilding; Onaka, Takashi; Kato, Daisuke

    2010-10-01

    In this paper, we derive the period-luminosity (P-L) relation for Large Magellanic Cloud (LMC) Cepheids based on mid-infrared AKARI observations. AKARI's Infrared Camera sources were matched to the Optical Gravitational Lensing Experiment-III (OGLE-III) LMC Cepheid catalogue. Together with the available I-band light curves from the OGLE-III catalogue, potential false matches were removed from the sample. This procedure excluded most of the sources in the S7 and S11 bands; hence, only the P-L relation in the N3 band is derived in this paper. Random-phase corrections were included in deriving the P-L relation for the single-epoch AKARI data; even though the derived P-L relation is consistent with the P-L relation without random-phase correction, however there is an ~7 per cent improvement in the dispersion of the P-L relation. The final adopted N3-band P-L relation is N3 = -3.246 log(P) + 15.844, with a dispersion of 0.149.

  5. THE DISTANCE MEASUREMENT OF NGC 1313 WITH CEPHEIDS

    Energy Technology Data Exchange (ETDEWEB)

    Qing, Gao; Wang, Wei; Liu, Ji-Feng [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Yoachim, Peter [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States)

    2015-01-20

    We present the detection of Cepheids in the barred spiral galaxy NGC 1313, using the Wide Field and Planetary Camera 2 on the Hubble Space Telescope. Twenty B(F450W) and V(F555W) epochs of observations spanning over three weeks were obtained, on which the profile-fitting photometry of all stars in the monitored field was performed using the package HSTphot. A sample of 26 variable stars have been identified to be Cepheids, with periods between 3 and 14 days. Based on the derived period-luminosity relations in B- and V-bands, we obtain an extinction-corrected distance modulus of μ{sub NGC} {sub 1313} = 28.32 ± 0.08 (random) ± 0.06 (systematic), employing the Large Magellanic Cloud as the distance zero point calibrator. The above moduli correspond to a distance of 4.61 ± 0.17 (random) ±0.13 (systematic) Mpc, consistent with previous measurements reported in the literature within uncertainties. In addition, the reddening to NGC 1313 is found to be small.

  6. The Distance Measurement of NGC 1313 With Cepheids

    CERN Document Server

    Gao, Qing; Liu, Ji-Feng; Yoachim, Peter

    2016-01-01

    We present the detection of Cepheids in the barred spiral galaxy NGC 1313, using the Wide Field and Planetary Camera 2 on the Hubble Space Telescpoe. Twenty B (F450W) and V (F555W) epochs of observations spanning over three weeks were obtained, on which the profile-fitting photometry of all stars in the monitored field was performed using the package HSTphot. A sample of 26 variable stars have been identified to be Cepheids, with periods between 3 and 14 days. Based on the derived period-luminosity relations in B and V bands, we obtain an extinction-corrected distance modulus of mu = 28.32 +- 0.08 (random) +- 0.06 (systematic), employing the Large Magellanic Cloud as the distance zero point calibrator. The above moduli correspond to a distance of 4.61 +- 0.17 (random) +- 0.13 (systematic) Mpc, consistent with previous measurements reported in the literature with uncertainties. In addition, the reddening to NGC 1313 is found to be small.

  7. Pulsating hot subdwarfs with MS companions or: EO Ceti is an sdO pulsator!

    CERN Document Server

    Østensen, Roy H

    2011-01-01

    About half of the hot subdwarfs are found to have spectra of composite types, indicating a main sequence companion of spectral type F-K, and the pulsators are no exception to this rule. The spectroscopic contamination from the main sequence stars makes it hard to reliably establish physical parameters for the hot component, and also makes pulsations harder to detect as the amplitudes are depressed. The binary fraction of the observed sample of hot subdwarf pulsators is discussed, as are the biases that are affecting it. Spectroscopic evidence is presented that clearly demonstrates that the well known sdB pulsator, EOCeti, is misclassified, and is actually an sdOV star.

  8. Connections between whistlers and pulsation activity

    OpenAIRE

    Verö, J.; Zieger, B.; Szendröi, J.; Vellante, M.; Střesğtik, J.; Lühr, H.; A. Best; Körmendi, A.; Lichtenberger, J.; Ménesi, T.; P. Bencze; Märcz, F.; V. Wesztergom

    2000-01-01

    Simultaneous whistler records of one station and geomagnetic pulsation (Pc3) records at three stations were compared. In a previous study correlation was found between occurrence and L value of propagation/excitation for the two phenomena. The recently investigated simultaneous records have shown that the correlation is better on longer time scales (days) than on shorter ones (minutes), but the L values of the propagation of whistlers/excitation of pulsat...

  9. A motion picture presentation of magnetic pulsations

    Science.gov (United States)

    Suzuki, A.; Kim, J. S.; Sugura, M.; Nagano, H.

    1981-01-01

    Using the data obtained from the IMS North American magnetometer network stations at high latitudes, a motion picture was made by a computer technique, describing time changes of Pc5 and Pi3 magnetic pulsation vectors. Examples of pulsation characteristics derived from this presentation are regional polarization changes including shifts of polarization demarcation lines, changes in the extent of an active region and its movement with time.

  10. The Secret Lives of Cepheids: A Multi-Wavelength Study of the Atmospheres and Real-Time Evolution of Classical Cepheids

    CERN Document Server

    Engle, Scott G

    2015-01-01

    The primary goal of this study is to observe how complex the behaviors of Cepheids can be, and to show how the continued monitoring of Cepheids at multiple wavelengths can begin to reveal their "secret lives." We aim to achieve this through optical photometry, UV spectroscopy and X-ray imaging. Through Villanova's guaranteed access to ground-based telescopes, we have secured well-covered light curves as regularly as possible. Amplitudes and times of max brightness were obtained and compared to previous literature results. At UV wavelengths, we have secured hi-res spectra of 2 nearby Cepheids - delta Cep and beta Dor - with HST-COS. Also, we have obtained X-ray images of 5 Cepheids with XMM-Newton and the Chandra X-ray Observatory, and further observations with both satellites have been proposed for (XMM) and approved (Chandra). Optical photometry has shown that 8 of the 10 observed Cepheids have amplitude variability, or hints thereof, and all 10 show period variability (recent, long-term or possibly periodic...

  11. Anchors for the Cosmic Distance Scale: the Cepheids U Sgr, CF Cas and CEab Cas

    CERN Document Server

    Majaess, D; Bidin, C Moni; Bonatto, C; Berdnikov, L; Balam, D; Moyano, M; Gallo, L; Turner, D; Lane, D; Gieren, W; Borissova, J; Kovtyukh, V; Beletsky, Y

    2013-01-01

    New and existing X-ray, UBVJHKsW(1-4), and spectroscopic observations were analyzed to constrain fundamental parameters for M25, NGC 7790, and dust along their sight-lines. The star clusters are of particular importance given they host the classical Cepheids U Sgr, CF Cas, and the visual binary Cepheids CEa and CEb Cas. Precise results from the multiband analysis, in tandem with a comprehensive determination of the Cepheids' period evolution (dP/dt) from ~140 years of observations, helped resolve concerns raised regarding the clusters and their key Cepheid constituents. Specifically, distances derived for members of M25 and NGC 7790 are 630+-25 pc and 3.40+-0.15 kpc, respectively.

  12. Period-Luminosity Relations For Magellanic Clouds Cepheids Based on OGLE-III Data: A Comparison

    CERN Document Server

    Ngeow, Chow-Choong

    2011-01-01

    The period-luminosity (P-L) relation for Cepheid variables is important in modern astrophysics. In this work, we present the multi-band P-L relations derived from the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) Cepheids, based on the latest release of OGLE-III catalogs. In addition to the V I band mean magnitudes adopted from OGLE-III catalogs, we also cross-matched the LMC and SMC Cepheids to the 2MASS point source catalogs and publicly available Spitzer catalogs from SAGE program. Mean magnitudes for these Cepheids were corrected for extinction using available extinction maps. When comparing the P-L slopes, we found that the P-L slopes in these two galaxies are consistent with each others within ~2.5sigma level.

  13. Hubble Space Telescope: Snapshot Survey for Resolved Companions of Galactic Cepheids

    CERN Document Server

    Evans, Nancy Remage; Schaefer, Gail H; Mason, Brian D; Tingle, Evan; Karovska, Margarita; Pillitteri, Ignazio

    2016-01-01

    We have conducted an imaging survey with the Hubble Space Telescope Wide Field Camera~3 (WFC3) of 70 Galactic Cepheids, typically within 1~kpc, with the aim of finding resolved physical companions. The WFC3 field typically covers the 0.1 pc area where companions are expected. In this paper, we identify 39 Cepheids having candidate companions, based on their positions in color--magnitude diagrams, and having separations $\\geq$5$"$ from the Cepheids. We use follow-up observations of 14 of these candidates with XMM-Newton, and of one of them with ROSAT, to separate X-ray-active young stars (probable physical companions) from field stars (chance alignments). Our preliminary estimate, based on the optical and X-ray observations, is that only 3\\% of the Cepheids in the sample have wide companions. Our survey easily detects resolved main-sequence companions as faint as spectral type K\

  14. MACHO observations of Type II cepheids and RV Tauri Stars in the LMC

    Energy Technology Data Exchange (ETDEWEB)

    Alcock, C.; Pollard, K.A.; Alisman, R.A. [and others

    1996-07-01

    We report the of the existence of RV Tauri stars in the Large Magellanic Cloud (LMC). This class of variable star has hitherto been unidentified in the Magellanic Clouds. In light and color curve behavior the RV Tauri stars appear to be an extension of the Type II Cepheids to longer periods. A single period-luminosity-color relationship is seen to describe both the Type II Cepheids and the RV Tauri stars in the LMC.

  15. The PL calibration for Milky Way Cepheids and its implications for the distance scale

    CERN Document Server

    Turner, David G

    2009-01-01

    The rationale behind recent calibrations of the Cepheid PL relation using the Wesenheit formulation is reviewed and reanalyzed, and it is shown that recent conclusions regarding a possible change in slope of the PL relation for short-period and long-period Cepheids are tied to a pathological distribution of HST calibrators within the instability strip. A recalibration of the period-luminosity relation is obtained using Galactic Cepheids in open clusters and groups, the resulting relationship, described by log L/L_sun = 2.415(+-0.035) + 1.148(+-0.044)log P, exhibiting only the moderate scatter expected from color spread within the instability strip. The relationship is confirmed by Cepheids with HST parallaxes, although without the need for Lutz-Kelker corrections, and in general by Cepheids with revised Hipparcos parallaxes, albeit with concerns about the cited precisions of the latter. A Wesenheit formulation of Wv = -2.259(+-0.083) - 4.185(+-0.103)log P for Galactic Cepheids is tested successfully using Cep...

  16. Nonradial Oscillations in Classical Pulsating Stars. Predictions and Discoveries

    CERN Document Server

    Dziembowski, W A

    2015-01-01

    After a brief historical introduction and recalling basic concepts of stellar oscillation theory, I focus my review on interpretation of secondary periodicities found in RR Lyrae stars and Cepheids as a manifestation of nonradial mode excitation.

  17. Objective detection of retinal vessel pulsation.

    Directory of Open Access Journals (Sweden)

    William H Morgan

    Full Text Available PURPOSE: Retinal venous pulsation detection is a subjective sign, which varies in elevated intracranial pressure, venous obstruction and glaucoma. To date no method can objectively measure and identify pulsating regions. METHOD: Using high resolution video-recordings of the optic disk and retina we measured fluctuating light absorption by haemoglobin during pulsation. Pulsation amplitude was calculated from all regions of the retinal image video-frames in a raster pattern. Segmented retinal images were formed by objectively selecting regions with amplitudes above a range of threshold values. These were compared to two observers manually drawing an outline of the pulsating areas while viewing video-clips in order to generate receiver operator characteristics. RESULTS: 216,515 image segments were analysed from 26 eyes in 18 research participants. Using data from each eye, the median area under the receiver operator curve (AU-ROC was 0.95. With all data analysed together the AU-ROC was 0.89. We defined the ideal threshold amplitude for detection of any pulsating segment being that with maximal sensitivity and specificity. This was 5 units (95% confidence interval 4.3 to 6.0 compared to 12 units before any regions were missed. A multivariate model demonstrated that ideal threshold amplitude increased with increased variation in video-sequence illumination (p = 0.0119, but between the two observers (p = 0.0919 or other variables. CONCLUSION: This technique demonstrates accurate identification of retinal vessel pulsating regions with no areas identified manually being missed with the objective technique. The amplitude values are derived objectively and may be a significant advance upon subjective ophthalmodynamometric threshold techniques.

  18. Kepler photometry of RRc stars: peculiar double-mode pulsations and period doubling

    CERN Document Server

    Moskalik, P; Kolenberg, K; Molnár, L; Kurtz, D W; Szabó, R; Benkő, J M; Nemec, J M; Chadid, M; Guggenberger, E; Ngeow, C -C; Jeon, Y -B; Kopacki, G; Kanbur, S M

    2014-01-01

    We present the analysis of four first overtone RR Lyrae stars observed with the Kepler space telescope, based on data obtained over nearly 2.5yr. All four stars are found to be multiperiodic. The strongest secondary mode with frequency f_2 has an amplitude of a few mmag, 20 - 45 times lower than the main radial mode with frequency f_1. The two oscillations have a period ratio of P_2/P_1 = 0.612 - 0.632 that cannot be reproduced by any two radial modes. Thus, the secondary mode is nonradial. Modes yielding similar period ratios have also recently been discovered in other variables of the RRc and RRd types. These objects form a homogenous group and constitute a new class of multimode RR Lyrae pulsators, analogous to a similar class of multimode classical Cepheids in the Magellanic Clouds. Because a secondary mode with P_2/P_1 ~ 0.61 is found in almost every RRc and RRd star observed from space, this form of multiperiodicity must be common. In all four Kepler RRc stars studied, we find subharmonics of f_2 at ~1/...

  19. Long Period Variables: questioning the pulsation paradigm

    CERN Document Server

    Berlioz-Arthaud, Paul

    2016-01-01

    Long period variables, among them Miras, are thought to be pulsating. Under this approach the whole star inflates and deflates along a period that can vary from 100 to 900 days; that pulsation is assumed to produce shock waves on the outer layers of the star that propagate into the atmosphere and could account for the increase in luminosity and the presence of emission lines in the spectra of these stars. However, this paradigm can seriously be questioned from a theoretical point of view. First, in order to maintain a radial pulsation, the spherical symmetry of the star must be preserved: how can it be reconciled with the large convective cells present in these stars? or when close companions are detected? Secondly, how different radial and non-radial pulsation modes of a sphere could be all damped except one radial mode? These problems have no solution and significantly weigh on the pulsation paradigm. Acknowledging this inconsistency, we show that a close companion around these stars could account for the s...

  20. Modeling of pulsating heat pipes.

    Energy Technology Data Exchange (ETDEWEB)

    Givler, Richard C.; Martinez, Mario J.

    2009-08-01

    This report summarizes the results of a computer model that describes the behavior of pulsating heat pipes (PHP). The purpose of the project was to develop a highly efficient (as compared to the heat transfer capability of solid copper) thermal groundplane (TGP) using silicon carbide (SiC) as the substrate material and water as the working fluid. The objective of this project is to develop a multi-physics model for this complex phenomenon to assist with an understanding of how PHPs operate and to be able to understand how various parameters (geometry, fill ratio, materials, working fluid, etc.) affect its performance. The physical processes describing a PHP are highly coupled. Understanding its operation is further complicated by the non-equilibrium nature of the interplay between evaporation/condensation, bubble growth and collapse or coalescence, and the coupled response of the multiphase fluid dynamics among the different channels. A comprehensive theory of operation and design tools for PHPs is still an unrealized task. In the following we first analyze, in some detail, a simple model that has been proposed to describe PHP behavior. Although it includes fundamental features of a PHP, it also makes some assumptions to keep the model tractable. In an effort to improve on current modeling practice, we constructed a model for a PHP using some unique features available in FLOW-3D, version 9.2-3 (Flow Science, 2007). We believe that this flow modeling software retains more of the salient features of a PHP and thus, provides a closer representation of its behavior.

  1. Experimental Identification of the Transmittance Matrix for any Element of the Pulsating Gas Manifold

    Science.gov (United States)

    CYKLIS, P.

    2001-07-01

    In positive-displacement compressor manifolds there are pressure pulsations due to their cyclic operation. The analysis of pressure pulsations in the compressor manifolds is important for various reasons: they directly affect the quantity of energy required for medium compression due to dynamic pressure charging, or inversely, dynamic suppression of suction and discharge processes; they cause mechanical vibrations of compressed gas piping network, they cause aerodynamic and mechanical noise; they affect the dynamics of working valves in valve compressors, they intensify the process of heat convection in heat exchangers in the gas network. The Helmholtz model used so far, which is the basis for users, who deal with pressure pulsation damping, contains many simplifying assumptions. This is because; a straight pipe segment substitutes each element of the piping system. In many cases this model is insufficient. An attempt of the analysis of other shapes was presented in references [1-3] but only simple geometry elements were considered. In other papers [4-8] the influence of the mean flow velocity caused problems. In the presented method, on the basis of pressure pulsation measurement results, firstly a division into the forward and backward going wave is determined, then the elements of the scattering (transmittance) matrix are calculated defining the installation element. This allows introducing the correction for gas mean velocity. The results of the method using correction for the gas mean velocity have been compared with the results without correction and Helmholtz model showing better accuracy.

  2. An Adaptive Code For Radial Stellar Pulsations

    CERN Document Server

    Buchler, J R; Marom, A; Kollath, Zoltan; Marom, Ariel

    1997-01-01

    We describe an implicit 1--D adaptive mesh hydrodynamics code that is specially tailored for radial stellar pulsations. In the Lagrangean limit the code reduces to the well tested Fraley scheme. The code has the useful feature that unwanted, long lasting transients can be avoided by smoothly switching on the adaptive mesh features starting from the Lagrangean code. Thus, a limit cycle pulsation that can readily be computed with the relaxation method of Stellingwerf will converge in a few tens of pulsation cycles when put into the adaptive mesh code. The code has been checked with two shock problems, viz Noh and Sedov, for which analytical solutions are known, and it has been found to be both accurate and stable. Superior results were obtained through the solution of the total energy (gravitational + kinetic + internal) equation rather than that of the internal energy only.

  3. Connections between whistlers and pulsation activity

    Directory of Open Access Journals (Sweden)

    J. Verö

    Full Text Available Simultaneous whistler records of one station and geomagnetic pulsation (Pc3 records at three stations were compared. In a previous study correlation was found between occurrence and L value of propagation/excitation for the two phenomena. The recently investigated simultaneous records have shown that the correlation is better on longer time scales (days than on shorter ones (minutes, but the L values of the propagation of whistlers/excitation of pulsations are correlated, i.e. if whistlers propagate in higher latitude ducts, pulsations have periods longer than in the case when whistlers propagate in lower latitude ducts.

    Key words: Electromagnetics (wave propagation - Magnetospheric physics (magnetospheric configuration and dynamics; MHD waves and instabilities

  4. Recent developments in pulsating aurora studies

    International Nuclear Information System (INIS)

    The field of pulsating aurora studies is reviewed. The paper begins with a short description of the characteristics of pulsating auroras and the theoretical ideas which, in view of existing experimental results, seem most important. A selection of new theoretical results and experimental results from both ground based instruments and instruments on rockets and satellites is then presented. There is now convincing evidence that the luminosity modulation is caused by a modulated flux of electron. The electron flux modulation seems to arise from a modulated resonant interaction between electrons and whistler mode waves in the equatorial plane, but the reason for the modulation is not known. Measurements concerning the drift and location of patches and the creation of Pi1 micropulsations are also deiscussed. Finally some suggestions for future research work are outlined. Optical measurements, especially with low light level TV, have proven to be of great importance in experimental studies of pulsating auroras. (author)

  5. OGLE-ing the Magellanic System: Three-Dimensional Structure of the Clouds and the Bridge Using Classical Cepheids

    Science.gov (United States)

    Jacyszyn-Dobrzeniecka, A. M.; Skowron, D. M.; Mróz, P.; Skowron, J.; Soszyński, I.; Udalski, A.; Pietrukowicz, P.; Kozłowski, S.; Wyrzykowski, Ł.; Poleski, R.; Pawlak, M.; Szymański, M. K.; Ulaczyk, K.

    2016-06-01

    We analyzed a sample of 9418 fundamental-mode and first-overtone classical Cepheids from the OGLE-IV Collection of Classical Cepheids. The distance to each Cepheid was calculated using the period-luminosity relation for the Wesenheit magnitude, fitted to our data. The classical Cepheids in the LMC are situated mainly in the bar and in the northern arm. The eastern part of the LMC is closer to us and the plane fit to the whole LMC sample yields the inclination i=24.°2 ±0.°7 and position angle P.A.=151.°4±1.°7. We redefined the LMC bar by extending it in the western direction and found no offset from the plane of the LMC contrary to previous studies. On the other hand, we found that the northern arm is offset from a plane by about -0.5 kpc, which was not observed before. The age distribution of the LMC Cepheids shows one maximum at about 100 Myr. We demonstrate that the SMC has a non-planar structure and can be described as an extended ellipsoid. We identified two large ellipsoidal off-axis structures in the SMC. The northern one is located closer to us and is younger, while the south-western is farther and older. The age distribution of the SMC Cepheids is bimodal with one maximum at 110 Myr, and another one at 220 Myr. Younger stars are located in the closer part of this galaxy while older ones are more distant. We classified nine Cepheids from our sample as Magellanic Bridge objects. These Cepheids show a large spread in three-dimensions although five of them form a connection between the Clouds. The closest one is closer than any of the LMC Cepheids, while the farthest one - farther than any SMC Cepheid. All but one Cepheids in the Magellanic Bridge are younger than 300 Myr. The oldest one can be associated with the SMC Wing.

  6. Pulsations of blue supergiants before and after helium core ignition

    OpenAIRE

    Ostrowski, Jakub; Daszyńska-Daszkiewicz

    2013-01-01

    We present results of pulsation analyses of B-type supergiant models with masses of $14 - 18 M_\\odot$, considering evolutionary stages before and after helium core ignition. Using a non-adiabatic pulsation code, we compute instability domains for low degree modes. For selected models in these two evolutionary phases, we compare properties of pulsation modes. Significant differences are found in oscillation spectra and the kinetic energy density of pulsation modes.

  7. CEPHEID CALIBRATIONS OF MODERN TYPE Ia SUPERNOVAE: IMPLICATIONS FOR THE HUBBLE CONSTANT

    International Nuclear Information System (INIS)

    This is the first of two papers reporting measurements from a program to determine the Hubble constant to ∼5% precision from a refurbished distance ladder. We present new observations of 110 Cepheid variables in the host galaxies of two recent Type Ia supernovae (SNe Ia), NGC 1309 and NGC 3021, using the Advanced Camera for Surveys on the Hubble Space Telescope (HST). We also present new observations of the hosts previously observed with HST whose SNe Ia provide the most precise luminosity calibrations: SN 1994ae in NGC 3370, SN 1998aq in NGC 3982, SN 1990N in NGC 4639, and SN 1981B in NGC 4536, as well as the maser host, NGC 4258. Increasing the interval between observations enabled the discovery of new, longer-period Cepheids, including 57 with P>60 days, which extend these period-luminosity (P-L) relations. We present 93 measurements of the metallicity parameter, 12 + log[O/H], measured from H II regions in the vicinity of the Cepheids and show these are consistent with solar metallicity. We find the slope of the seven dereddened P-L relations to be consistent with that of the Large Magellanic Cloud Cepheids and with parallax measurements of Galactic Cepheids, and we address the implications for the Hubble constant. We also present multi-band light curves of SN 2002fk (in NGC 1309) and SN 1995al (in NGC 3021) which may be used to calibrate their luminosities. In the second paper, we present observations of the Cepheids in the H band obtained with the Near-Infrared Camera and Multi-Object Spectrometer on HST, further mitigating systematic errors along the distance ladder resulting from dust and chemical variations. The quality and homogeneity of these SN and Cepheid data provide the basis for a more precise determination of the Hubble constant.

  8. Benefit of pulsation in soft corals.

    Science.gov (United States)

    Kremien, Maya; Shavit, Uri; Mass, Tali; Genin, Amatzia

    2013-05-28

    Soft corals of the family Xeniidae exhibit a unique, rhythmic pulsation of their tentacles (Movie S1), first noted by Lamarck nearly 200 y ago. However, the adaptive benefit of this perpetual, energetically costly motion is poorly understood. Using in situ underwater particle image velocimetry, we found that the pulsation motions thrust water upward and enhance mixing across the coral-water boundary layer. The induced upward motion effectively prevents refiltration of water by neighboring polyps, while the intensification of mixing, together with the upward flow, greatly enhances the coral's photosynthesis. A series of controlled laboratory experiments with the common xeniid coral Heteroxenia fuscescens showed that the net photosynthesis rate during pulsation was up to an order of magnitude higher than during the coral's resting, nonpulsating state. This enhancement diminished when the concentration of oxygen in the ambient water was artificially raised, indicating that the enhancement of photosynthesis was due to a greater efflux of oxygen from the coral tissues. By lowering the internal oxygen concentration, pulsation alleviates the problem of reduced affinity of ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO) to CO2 under conditions of high oxygen concentrations. The photosynthesis-respiration ratio of the pulsating H. fuscescens was markedly higher than the ratios reported for nonpulsating soft and stony corals. Although pulsation is commonly used for locomotion and filtration in marine mobile animals, its occurrence in sessile (bottom-attached) species is limited to members of the ancient phylum Cnidaria, where it is used to accelerate water and enhance physiological processes.

  9. Pulsating Strings in Lunin-Maldacena Backgrounds

    OpenAIRE

    Giardino, Sergio; Rivelles, Victor

    2011-01-01

    We consider pulsating strings in Lunin-Maldacena backgrounds, specifically in deformed Minkowski spacetime and deformed AdS_5xS^5. We find the relation between the energy and the oscillation number of the pulsating string when the deformation is small. Since the oscillation number is an adiabatic invariant it can be used to explore the regime of highly excited string states. We then quantize the string and look for such a sector. For the deformed Minkowski background we find a precise match w...

  10. A lack of classical Cepheids in the inner part of the Galactic disk

    CERN Document Server

    Matsunaga, Noriyuki; Bono, Giuseppe; Kobayashi, Naoto; Inno, Laura; Nagayama, Takahiro; Nishiyama, Shogo; Matsuoka, Yoshiki; Nagata, Tetsuya

    2016-01-01

    Recent large-scale infrared surveys have been revealing stellar populations in the inner Galaxy seen through strong interstellar extinction in the disk. In particular, classical Cepheids with their period-luminosity and period-age relations are useful tracers of Galactic structure and evolution. Interesting groups of Cepheids reported recently include four Cepheids in the Nuclear Stellar Disk (NSD), about 200 pc around the Galactic Centre, found by Matsunaga et al. and those spread across the inner part of the disk reported by Dekany and collaborators. We here report our discovery of nearly thirty classical Cepheids towards the bulge region, some of which are common with Dekany et al., and discuss the large impact of the reddening correction on distance estimates for these objects. Assuming that the four Cepheids in the NSD are located at the distance of the Galactic Centre and that the near-infrared extinction law, i.e. wavelength dependency of the interstellar extinction, is not systematically different bet...

  11. A Test of the Calibration of the Tully-Fisher Relation Using Cepheid and SNIa Distances

    CERN Document Server

    Shanks, T

    1997-01-01

    We make a direct test of Tully-Fisher distance estimates to eleven spiral galaxies with HST Cepheid distances and to twelve spiral galaxies with SNIa distances. The HST Cepheid distances come from the work of Freedman (1997), Sandage et al (1996) and Tanvir et al (1995). The SNIa distances come from Pierce (1994), calibrated using the Cepheid results of Sandage et al (1996). The Tully-Fisher distances mostly come from the work of Pierce (1994). The results show that the Tully-Fisher distance moduli are too short with respect to the Cepheid distances by 0.46+-0.14mag and too short with respect to the SNIa distances by 0.46+-0.19mag. Combining the HST Cepheid and SNIa data suggests that, overall, previous Tully-Fisher distances were too short by 0.46+-0.11mag, a result which is significant at the 4sigma level. These data therefore indicate that previous Tully-Fisher distances should be revised upwards by 24+-6% implying, for example, a Virgo distance of 19.3+-1.9Mpc. The value of Ho from Tully-Fisher estimates ...

  12. The Cepheids of Centaurus A (NGC 5128) and Implications for H0

    CERN Document Server

    Majaess, Daniel J

    2010-01-01

    An analysis based on new OGLE observations reaffirms Ferrarese et al.2007 discovery of 5 Type II Cepheids in NGC 5128. The distance to that comparatively unreddened population is d=3.8+-0.4(se)+-0.8(sd) Mpc. The classical Cepheids in NGC 5128 are the most obscured in the extragalactic sample (n=30) surveyed, whereas groups of Cepheids tied to several SNe host galaxies feature negative reddenings. Adopting an anomalous extinction law for Cepheids in NGC 5128 owing to observations of SN 1986G (Rv~2.4) is not favoured, granted SNe Ia may follow small Rv. The distances to classical Cepheids in NGC 5128 exhibit a dependence on colour and CCD chip, which may arise in part from photometric contamination. The mean for the entire sample is d~3.1 Mpc, while applying a colour cut yields d~3.5 Mpc. The distance was established via the latest VI Galactic Wesenheit functions that include the 10 HST calibrators, and which imply a shorter distance scale than Sandage et al.2004 by 15% at P~25 d. HST monitored classical Cephei...

  13. Updated 24 $\\mu\\mathrm{m}$ Period-Luminosity Relation Derived from Galactic Cepheids

    CERN Document Server

    Ngeow, Chow-Choong; Bhardwaj, Anupam; Kanbur, Shashi M; Singh, Harinder P

    2015-01-01

    In this work, we updated the catalog of Galactic Cepheids with $24\\mu\\mathrm{m}$ photometry by cross-matching the positions of known Galactic Cepheids to the recently released MIPSGAL point source catalog. We have added 36 new sources featuring MIPSGAL photometry in our analysis, thus increasing the existing sample to 65. Six different sources of compiled Cepheid distances were used to establish a $24\\mu\\mathrm{m}$ period-luminosity (P-L) relation. Our recommended $24\\mu\\mathrm{m}$ P-L relation is $M_{24\\mu\\mathrm{m}}=-3.18(\\pm0.10)\\log P - 2.46(\\pm0.10)$, with an estimated intrinsic dispersion of 0.20 mag, and is derived from 58 Cepheids exhibiting distances based on a calibrated Wesenheit function. The slopes of the P-L relations were steepest when tied solely to the 10 Cepheids exhibiting trigonometric parallaxes from the Hubble Space Telescope and Hipparcos. Statistical tests suggest that these P-L relations are significantly different from those associated with other methods of distance determination, an...

  14. Resolved Companions of Cepheids: Testing the Candidates with X-Ray Observations

    CERN Document Server

    Evans, Nancy Remage; Wolk, Scott; Karovska, Margarita; Tingle, Evan; Guinan, Edward; Engle, Scott; Bond, Howard E; Schaefer, Gail H; Mason, Brian D

    2016-01-01

    We have made {\\it XMM-Newton\\/} observations of 14 Galactic Cepheids that have candidate resolved ($\\geq$5$\\arcsec$) companion stars based on our earlier {\\it HST\\/} WFC3 imaging survey. Main-sequence stars that are young enough to be physical companions of Cepheids are expected to be strong X-ray producers in contrast to field stars. {\\it XMM-Newton\\/} exposures were set to detect essentially all companions hotter than spectral type M0 (corresponding to 0.5 $ M_\\odot$.) The large majority of our candidate companions were not detected in X-rays, and hence are not confirmed as young companions. One resolved candidate (S~Nor \\#4) was unambiguously detected, but the Cepheid is a member of a populous cluster. For this reason, it is likely that S~Nor \\#4 is a cluster member rather than a gravitationally bound companion. Two further Cepheids (S~Mus and R~Cru) have X-ray emission that might be produced by either the Cepheid or the candidate resolved companion. A subsequent {\\it Chandra} observation of S Mus shows th...

  15. Emission sources and quantities

    International Nuclear Information System (INIS)

    The paper examines emission sources and quantities for SO2 and NOx. Natural SO2 is released from volcanic sources and to a much lower extent from marsh gases. In nature NOx is mainly produced in the course of the chemical and bacterial denitrification processes going on in the soil. Manmade pollutants are produced in combustion processes. The paper concentrates on manmade pollution. Aspects discussed include: mechanism of pollution development; manmade emission sources (e.g. industry, traffic, power plants and domestic sources); and emission quantities and forecasts. 11 refs., 2 figs., 5 tabs

  16. Predicting phase shift effects for vibrating fluid-conveying pipes due to Coriolis forces and fluid pulsation

    Science.gov (United States)

    Enz, Stephanie; Thomsen, Jon Juel

    2011-10-01

    Knowing the influence of fluid flow perturbations on the dynamic behavior of fluid-conveying pipes is of relevance, e.g., when exploiting flow-induced oscillations of pipes to determine the fluids mass flow or density, as done with Coriolis flow meters (CFM). This could be used in the attempts to improve accuracy, precision, and robustness of CFMs. A simple mathematical model of a fluid-conveying pipe is formulated and the effect of pulsating fluid flow is analyzed using a multiple time scaling perturbation analysis. The results are simple analytical predictions for the transverse pipe displacement and approximate axial shift in vibration phase. The analytical predictions are tested against pure numerical solution using representative examples, showing good agreement. Fluid pulsations are predicted not to influence CFM accuracy, since proper signal filtering is seen to allow the determination of the correct mean phase shift. Large amplitude motions, which could influence CFM robustness, do not appear to be induced by the investigated fluid pulsation. Pulsating fluid of the combination resonance type could, however, influence CFMs robustness, if induced pipe motions go unnoticed and uncontrolled during CFM operation by feedback control. The analytical predictions offer an immediate insight into how fluid pulsation affects phase shift, which is a quantity measured by CFMs to estimate the mass flow, and lead to hypotheses for more complex geometries, i.e. industrial CFMs. The validity of these hypotheses is suggested to be tested using laboratory experiments, or detailed computational models taking fluid-structure interaction into account.

  17. Evaluation of Pump Pulsation in Respirable Size-Selective Sampling: Part I. Pulsation Measurements

    OpenAIRE

    Lee, Eun Gyung; Lee, Larry; Möhlmann, Carsten; Flemmer, Michael M.; Kashon, Michael; Harper, Martin

    2013-01-01

    Pulsations generated by personal sampling pumps modulate the airflow through the sampling trains, thereby varying sampling efficiencies, and possibly invalidating collection or monitoring. The purpose of this study was to characterize pulsations generated by personal sampling pumps relative to a nominal flow rate at the inlet of different respirable cyclones. Experiments were conducted using a factorial combination of 13 widely used sampling pumps (11 medium and 2 high volumetric flow rate pu...

  18. Panchromatic Hubble Andromeda Treasury. XIV. The Period-Age Relationship of Cepheid Variables in M31 Star Clusters

    CERN Document Server

    Senchyna, Peter; Dalcanton, Julianne J; Beerman, Lori C; Fouesneau, Morgan; Dolphin, Andrew; Williams, Benjamin F; Rosenfield, Philip; Larsen, Søren S

    2015-01-01

    We present a sample of 11 M31 Cepheids in stellar clusters, derived from the overlap of the Panchromatic Hubble Andromeda Treasury (PHAT) cluster catalog and the Pan-STARRS1 (PS1) disk Cepheid catalog. After identifying the PS1 Cepheids in the HST catalog, we calibrate the PS1 mean magnitudes using the higher resolution HST photometry, revealing up to 1 magnitude offsets due to crowding effects in the ground-based catalog. We measure ages of the clusters by performing single stellar population fits to their color-magnitude diagrams (CMDs) excluding their Cepheids. From these cluster age measurements, we derive an empirical period-age relation which agrees well with the existing literature values. By confirming this relation for M31 Cepheids, we justify its application in high-precision pointwise age estimation across M31.

  19. Panchromatic Hubble Andromeda Treasury. XIV. The Period-Age Relationship of Cepheid Variables in M31 Star Clusters

    Science.gov (United States)

    Senchyna, Peter; Johnson, L. Clifton; Dalcanton, Julianne J.; Beerman, Lori C.; Fouesneau, Morgan; Dolphin, Andrew; Williams, Benjamin F.; Rosenfield, Philip; Larsen, Søren S.

    2015-11-01

    We present a sample of 11 M31 Cepheids in stellar clusters, derived from the overlap of the Panchromatic Hubble Andromeda Treasury cluster catalog and the Pan-STARRS1 (PS1) disk Cepheid catalog. After identifying the PS1 Cepheids in the Hubble Space Telescope (HST) catalog, we calibrate the PS1 mean magnitudes using the higher resolution HST photometry, revealing up to 1 mag offsets due to crowding effects in the ground-based catalog. We measure ages of the clusters by performing single-age stellar population fits to their color-magnitude diagrams excluding their Cepheids. From these cluster age measurements, we derive an empirical period-age relation which agrees well with the existing literature values. By confirming this relation for M31 Cepheids, we justify its application in high-precision pointwise age estimation across M31.

  20. Auroral pulsations and accompanying VLF emissions

    Directory of Open Access Journals (Sweden)

    V. R. Tagirov

    Full Text Available Results of simultaneous TV observations of pulsating auroral patches and ELF-VLF-emissions in the morning sector carried out in Sodankylä (Finland on February 15, 1991 are presented. Auroral pulsating activity was typical having pulsating patches with characteristic periods of about 7 s. Narrow-band hiss emissions and chorus elements at intervals of 0.3–0.4 s formed the main ELF-VLF activity in the frequency range 1.0–2.5 kHz at the same time. The analysis of auroral images with time resolution of 0.04 s allowed perfectly separate analysis of spatial and temporal variations in the auroral luminosity. Mutual correspondence between the behaviour of the luminous auroral patches and the appearance of ELF noise type hiss emissions and VLF chorus trains was found in two intervals chosen for analysis. While the hiss emissions were associated with the appearance of luminosity inside a limited area close to the zenith, the structured VLF emissions were accompanied by rapid motion of luminosity inside the area. The spatial dimension of the pulsating area was about 45–50 km and luminosity propagated inside it with velocity of about 10–12 kms. We discuss a new approach to explain the 5–15 s auroral pulsation based on the theory of flowing cyclotron maser and relaxation characteristics of ionosphere.

    Key words. Magnetospheric physics (auroral phenomena; magnetosphere-ionosphere interactions · Space plasma physics (wave-particle interactions

  1. Digital filter technology and its application to geomagnetic pulsations in Antarctica

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Digital filter technology is an important method in study of geomagnetic pulsations in Antarctica. The signals received by pulsation magnetometer on the ground include various types of magnetic pulsations. Some types of pulsations or some frequency hands of pulsations can be extracted from the signals by means of digital filter technology because types of pulsations are defined according to their frequency range. In this paper usual digital filter technology is provided for study of magnetic pulsations in Antarctica and some examples are introduced.

  2. Trajectories of Cepheid variable stars in the Galactic nuclear bulge

    Science.gov (United States)

    Matsunaga, Noriyuki

    2012-06-01

    The central region of our Galaxy provides us with a good opportunity to study the evolution of galactic nuclei and bulges because we can observe various phenomena in detail at the proximity of 8 kpc. There is a hierarchical alignment of stellar systems with different sizes; from the extended bulge, the nuclear bulge, down to the compact cluster around the central supermassive blackhole. The nuclear bulge contains stars as young as a few Myr, and even hosts the ongoing star formation. These are in contrast to the more extended bulge which are dominated by old stars, ~10Gyr. It is considered that the star formation in the nuclear bulge is caused by fresh gas provided from the inner disk. In this picture, the nuclear bulge plays an important role as the interface between the gas supplier, the inner disk, and the galactic nucleus. Kinematics of young stars in the nuclear bulge is important to discuss the star forming process and the gas circulation in the Galactic Center. We here propose spectroscopic observations of Cepheid variable stars, ~25 Myr, which we recently discovered in the nuclear bulge. The spectra taken in this proposal will allow timely estimates of the systemic velocities of the variable stars.

  3. Estimation of the Galactic Spiral Pattern Speed from Cepheids

    CERN Document Server

    Bobylev, V V; 10.1134/S1063773712100015

    2012-01-01

    To study the peculiarities of the Galactic spiral density wave, we have analyzed the space velocities of Galactic Cepheids with proper motions from the Hipparcos catalog and line-of-sight velocities from various sources. First, based on the entire sample of 185 stars and taking $R_0 = 8$ kpc, we have found the components of the peculiar solar velocity $(u_\\odot,v_\\odot,w_\\odot)=(7.6,11.6,6.1)\\pm(0.8,1.1,0.6)$ km s$^{-1}$, the angular velocity of Galactic rotation $\\Omega_0 = -27.4\\pm0.6$ km s$^{-1}$ kpc$^{-1}$ and its derivatives $\\Omega^{'}_0 = +4.07\\pm0.21,$ km s$^{-1}$ kpc$^{-2}$ and $\\Omega^{"}_0 = -0.83\\pm0.17,$ km s$^{-1}$ kpc$^{-3}$, the amplitudes of the velocity perturbations in the spiral density wave $f_R=-6.7\\pm0.7$ and $f_\\theta= 3.5\\pm0.5$ km s$^{-1}$, the pitch angle of a two-armed spiral pattern (m = 2) $i=-4.5\\pm0.1^\\circ$ (which corresponds to a wavelength $\\lambda=2.0\\pm0.1$ kpc), and the phase of the Sun in the spiral density wave $\\chi_\\odot=-191\\pm5^\\circ$. The phase $\\chi_\\odot$ has bee...

  4. A new Cepheid distance measurement and method for NGC 6822

    Energy Technology Data Exchange (ETDEWEB)

    Rich, Jeffrey A.; Persson, S. E.; Freedman, Wendy L.; Madore, Barry F.; Monson, Andrew J.; Scowcroft, Victoria; Seibert, Mark, E-mail: jrich@obs.carnegiescience.edu [Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

    2014-10-20

    We present a revised distance to the nearby galaxy NGC 6822 using a new multi-band fit to both previously published and new optical, near-, and mid-infrared data for Cepheid variables. The new data presented in this study include multi-epoch observations obtained in 3.6 μm and 4.5 μm with the Spitzer Space Telescope taken for the Carnegie Hubble Program. We also present new observations in J, H, and K{sub s} with FourStar on the Magellan Baade Telescope at Las Campanas Observatory. We determine mean magnitudes and present new period-luminosity relations in V, I, J, H, K{sub s} , Infrared Array Camera 3.6 μm, and 4.5 μm. In addition to using the multi-band distance moduli to calculate extinction and a true distance, we present a new method for determining an extinction-corrected distance modulus from multi-band data with varying sample sizes. We combine the distance moduli and extinction for individual stars to determine E(B – V) = 0.35 ± 0.04 and a true distance modulus μ {sub o} = 23.38 ± 0.02{sub stat} ± 0.04{sub sys}.

  5. The VMC survey - XX. Identification of new Cepheids in the Small Magellanic Cloud

    Science.gov (United States)

    Moretti, M. I.; Clementini, G.; Ripepi, V.; Marconi, M.; Rubele, S.; Cioni, M.-R. L.; Muraveva, T.; Groenewegen, M. A. T.; Cross, N. J. G.; Ivanov, V. D.; Piatti, A. E.; de Grijs, R.

    2016-06-01

    We present Ks-band light curves for 299 Cepheids in the Small Magellanic Cloud (SMC) of which 288 are new discoveries that we have identified using multi-epoch near-infrared photometry obtained by the VISTA survey of the Magellanic Clouds system (VMC). The new Cepheids have periods in the range from 0.34 to 9.1 d and cover the magnitude interval 12.9 ≤ ≤ 17.6 mag. Our method was developed using variable stars previously identified by the optical microlensing survey OGLE. We focus on searching new Cepheids in external regions of the SMC for which complete VMC Ks-band observations are available and no comprehensive identification of different types of variable stars from other surveys exists yet.

  6. The VMC Survey - XIX. Identification of new Cepheids in the Small Magellanic Cloud

    CERN Document Server

    Moretti, M I; Ripepi, V; Marconi, M; Rubele, S; Cioni, M -R L; Muraveva, T; Groenewegen, M A T; Cross, N J G; Ivanov, V D; Piatti, A E; de Grijs, R

    2015-01-01

    We present Ks-band light curves for 299 new Cepheids in the Small Magellanic Cloud (SMC) that were identified using multi-epoch near-infrared photometry obtained by the VISTA survey of the Magellanic Clouds system (VMC). The new Cepheids have periods in the range from 0.38 to 13.15 days and cover the magnitude interval 12.35 < Ks < 17.6 mag. Our method was developed using variable stars previously identified by the optical microlensing survey OGLE. We focus on searching new Cepheids in external regions of the SMC for which complete VMC Ks-band observations are available and no comprehensive identification of different types of variable stars from other surveys exists yet.

  7. Hubble Space Telescope Snapshot Survey for Resolved Companions of Galactic Cepheids

    Science.gov (United States)

    Evans, Nancy Remage; Bond, Howard E.; Schaefer, Gail H.; Mason, Brian D.; Tingle, Evan; Karovska, Margarita; Pillitteri, Ignazio

    2016-05-01

    We have conducted an imaging survey with the Hubble Space Telescope Wide Field Camera 3 (WFC3) of 70 Galactic Cepheids, typically within 1 kpc, with the aim of finding resolved physical companions. The WFC3 field typically covers the 0.1 pc area where companions are expected. In this paper, we identify 39 Cepheids having candidate companions, based on their positions in color-magnitude diagrams, and having separations ⩾ 5'' from the Cepheids. We use follow-up observations of 14 of these candidates with XMM-Newton, and of one of them with ROSAT, to separate X-ray-active young stars (probable physical companions) from field stars (chance alignments). Our preliminary estimate, based on the optical and X-ray observations, is that only 3% of the Cepheids in the sample have wide companions. Our survey easily detects resolved main-sequence companions as faint as spectral type K. Thus the fact that the two most probable companions (those of FF Aql and RV Sco) are earlier than type K is not simply a function of the detection limit. We find no physical companions having separations larger than 4000 au in the X-ray survey. Two Cepheids are exceptions in that they do have young companions at significantly larger separations (δ Cep and S Nor), but both belong to a cluster or a loose association, so our working model is that they are not gravitationally bound binary members, but rather cluster/association members. All of these properties provide constraints on both star formation and subsequent dynamical evolution. The low frequency of true physical companions at separations > 5'' is confirmed by examination of the subset of the nearest Cepheids and also the density of the fields. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

  8. New open cluster Cepheids in the VVV survey tightly constrain near-infrared period--luminosity relations

    CERN Document Server

    Chen, Xiaodian; Deng, Licai

    2016-01-01

    Classical Cepheids are among the most useful Galactic and nearby extragalactic distance tracers because of their well-defined period--luminosity relations (PLRs). Open cluster (OC) Cepheids are important objects to independently calibrate these PLRs. Based on Data Release 1 of the {\\sl VISTA} Variables in the V\\'ia L\\'actea survey, we have discovered four new, faint and heavily reddened OC Cepheids, including the longest-period OC Cepheid known, ASAS J180342$-$2211.0 in Teutsch 14a. The other OC--Cepheid pairs include NGC 6334 and V0470 Sco, Majaess 170 and ASAS J160125$-$5150.3, and Teutsch 77 and BB Cen. ASAS J180342$-$2211.0, with a period of $\\log P = 1.623$ [days] is important to constrain the slope of the PLR. The currently most complete $JHK_{\\rm s}$ Galactic Cepheid PLRs are obtained based on a significantly increased sample of 31 OC Cepheids, with associated uncertainties that are improved by 40 per cent compared with previous determinations (in the $J$ band). The NIR PLRs are in good agreement with ...

  9. The pulsating extreme helium star BD + 1303224

    International Nuclear Information System (INIS)

    Ultraviolet flux variations are reported for the pulsating extreme helium star BD + 1303224 (V652 Her). Effective temperature and angular radius variations over a cycle are determined from static plane-parallel LTE model atmospheres. When compared with radius changes derived from ground-based spectroscopy, the angular radius variations indicate radial pulsations and correspond to a distance of 1.5 +- 0.1 kpc. BD + 1303224 is thought to be a helium-burning star of 0.7 Msolar masses, which has an envelope contracting as the helium-burning core grows; it is similar to HD 144941 and these two stars may constitute a new sub-class of the hydrogen-deficient stars. (author)

  10. Flow induced pulsations in pipe systems

    Science.gov (United States)

    Bruggeman, Jan Cornelis

    1987-12-01

    The aeroacoustic behavior of a low Mach number, high Reynolds number flow through a pipe with closed side branches was investigated. Sound is generated by coherent structures of concentrated vorticity formed periodically in the separated flow in the T-shaped junctions of side branches and the main pipe. The case of moderate pulsation amplitudes was investigated. It appears that the vortical flow in a T-joint is an aeroacoustic source of constant strength when acoustic energy losses due to radiation and friction are small but not negligible. When acoustic energy losses due to radiation and friction are negligible, the nonlinear character of vortex damping is the amplitude limiting mechanism. It is stressed that aeroacoustic sources should not be neglected in studies of the response of a piping lay-out with flow to, e.g., the pulsating output of a compressor.

  11. Pulsating White Dwarf Stars and Precision Asteroseismology

    CERN Document Server

    Winget, D E

    2008-01-01

    Galactic history is written in the white dwarf stars. Their surface properties hint at interiors composed of matter under extreme conditions. In the forty years since their discovery, pulsating white dwarf stars have moved from side-show curiosities to center stage as important tools for unraveling the deep mysteries of the Universe. Innovative observational techniques and theoretical modeling tools have breathed life into precision asteroseismology. We are just learning to use this powerful tool, confronting theoretical models with observed frequencies and their time rate-of-change. With this tool, we calibrate white dwarf cosmochronology; we explore equations of state; we measure stellar masses, rotation rates, and nuclear reaction rates; we explore the physics of interior crystallization; we study the structure of the progenitors of Type Ia supernovae, and we test models of dark matter. The white dwarf pulsations are at once the heartbeat of galactic history and a window into unexplored and exotic physics.

  12. Gas Pulsations: A Shock Tube Mechanism

    OpenAIRE

    Huang, Paul Xiubao

    2012-01-01

    Gas pulsations are defined presently as a macro flow rate and/or pressure fluctuation with relatively low frequency and high amplitude. They commonly exist in HVACR, energy and other processing industries, and are widely accepted to be mainly caused by PD type gas machinery such as reciprocating or rotary compressors, expanders and Roots type blowers. Moreover, they are believed to be responsible for system vibrations, noises and fatigue failures. Naturally, as important a matter as gas pulsa...

  13. Erosion of metals by pulsating water jet

    OpenAIRE

    Foldyna, J.; Klich, J. (Jiří); Hlaváček, P.; M. Zeleňák; Ščučka, J. (Jiří)

    2012-01-01

    The aim of the paper was to determine erosion effects of pulsating water jet impinging the surface of metal sample. The influence of repeated impacts of water pulses and impact velocity (operating pressure) on the erosion of metal surface was investigated. The development of erosion pattern with respect to number of impacts was analysed and discussed. It was found that erosion caused by repeated impacts of water pulses occurs in three stages. The stage of erosion of the surface can be determi...

  14. Research on Order Quantity Simulation

    Institute of Scientific and Technical Information of China (English)

    ZHOU Hong; LI Zhi-cheng

    2003-01-01

    The order quantity is often affected by various factors, so it is more valuable to research the problem of evaluating the order quantity based on a less premise. In this paper, a complicated order quantity problem is studied and an order quantity simulation system is established with the simulation software of ARENA. Finally, an example is given.

  15. Nonradial pulsations of hot evolved stars

    International Nuclear Information System (INIS)

    There are three classes of faint blue variable stars: the ZZ Ceti variables (DAV degenerate dwarfs), the DBV variables (DB degenerate dwarfs), and the GW Vir variables (DOV degenerate dwarfs). None of these classes of variable stars were known at the time of the last blue star meeting. Observational and theoretical studies of the ZZ Ceti variables, the DBV variables, and the GW Vir variables have shown them to be pulsating in nonradial g-modes. The cause of the pulsation has been determined for each class of variable star and, in all cases, also involves predictions of the stars envelope composition. The predictions are that the ZZ Ceti variables must have pure hydrogen surface layers, the DBV stars must have pure helium surface layers, and the GW Vir stars must have carbon and oxygen rich surface layers with less than 30% (by mass) of helium. Given these compositions, it is found that pulsation driving occurs as a result of the kappa and gamma effects operating in the partial ionization zones of either hydrogen or helium. In addition, a new driving mechanism, called convection blocking, also occurs in these variables. For the GW Vir variables, it is the kappa and gamma effects in the partial ionization regions of carbon and oxygen. 45 refs

  16. Location of Decimetric Pulsations in Solar Flares

    Science.gov (United States)

    Benz, Arnold O.; Battaglia, Marina; Vilmer, Nicole

    This work investigates the spatial relation between coronal X-ray sources and coherent radio emissions, both generally thought to be signatures of particle acceleration. Two limb events were selected during which the radio emission was well correlated in time with hard X-rays. The radio emissions were of the type of decimetric pulsations as determined from the spectrogram observed by Phoenix-2 of ETH Zurich. The radio positions were measured from observations with the Nançay Radioheliograph between 236 and 432 MHz and compared to the position of the coronal X-ray source imaged with RHESSI. The radio pulsations originated at least 30 - 240 Mm above the coronal hard X-ray source. The altitude of the radio emission increases generally with lower frequency. The average positions at different frequencies are on a line pointing approximately to the coronal hard X-ray source. Thus, the pulsations cannot be caused by electrons trapped in the flare loops, but are consistent with emission from a current sheet above the coronal source.

  17. Location of Decimetric Pulsations in Solar Flares

    CERN Document Server

    Benz, Arnold O; Vilmer, Nicole

    2011-01-01

    This work investigates the spatial relation between coronal X-ray sources and coherent radio emissions, both generally thought to be signatures of particle acceleration. Two limb events were selected during which the radio emission was well correlated in time with hard X-rays. The radio emissions were of the type of decimetric pulsations as determined from the spectrogram observed by Phoenix-2 of ETH Zurich. The radio positions were measured from observations with the Nancay Radioheliograph between 236 and 432 MHz and compared to the position of the coronal X-ray source imaged with RHESSI. The radio pulsations originated at least 30 - 240 Mm above the coronal hard X-ray source. The altitude of the radio emission increases generally with lower frequency. The average positions at different frequencies are on a line pointing approximately to the coronal hard X-ray source. Thus, the pulsations cannot be caused by electrons trapped in the flare loops, but are consistent with emission from a current sheet above the...

  18. SuperWASP observations of pulsating Am stars

    CERN Document Server

    Smalley, B; Smith, A M S; Fossati, L; Anderson, D R; Barros, S C C; Butters, O W; Cameron, A Collier; Christian, D J; Enoch, B; Faedi, F; Haswell, C A; Hellier, C; Holmes, S; Horne, K; Kane, S R; Lister, T A; Maxted, P F L; Norton, A J; Parley, N; Pollacco, D; Simpson, E K; Skillen, I; Southworth, J; Street, R A; West, R G; Wheatley, P J; Wood, P L

    2011-01-01

    We have studied over 1600 Am stars at a photometric precision of 1 mmag with SuperWASP photometric data. Contrary to previous belief, we find that around 200 Am stars are pulsating delta Sct and gamma Dor stars, with low amplitudes that have been missed in previous, less extensive studies. While the amplitudes are generally low, the presence of pulsation in Am stars places a strong constraint on atmospheric convection, and may require the pulsation to be laminar. While some pulsating Am stars have been previously found to be delta Sct stars, the vast majority of Am stars known to pulsate are presented in this paper. They will form the basis of future statistical studies of pulsation in the presence of atomic diffusion.

  19. Metallicity effect on the cepheid period-luminosity relation and H-0

    NARCIS (Netherlands)

    Beaulieu, JP

    1998-01-01

    in the first article, we presented a review on the Cepheid PL relation as a tool for measuring distances, and showed the sensitivity of the method to metallicity. Accounting for it brings the recent differing estimates of H-0 into agreement. (C) Academie des Sciences/Elsevier, Paris.

  20. PHAT XIII: The Cepheid Period-Luminosity Relation in M31 Based on the PHAT Survey

    CERN Document Server

    Wagner-Kaiser, R; Dalcanton, J J; Williams, B F; Dolphin, A

    2015-01-01

    Using Hubble Space Telescope Advanced Camera for Surveys (HST/ACS) and Wide Field Camera 3 (WFC3) observations from the Panchromatic Hubble Andromeda Treasury (PHAT), we present new period-luminosity relations for Cepheid variables in M31. Cepheid from several ground-based studies are identified in the PHAT pho- tometry to derive new Period-Luminosity and Wesenheit Period-Luminosity relations in the NIR and visual filters. We derive a distance modulus to M31 of 24.51+/-0.08 in the IR bands and 24.32+/-0.09 in the visual bands, including the first PL relations in the F475W and F814W filters for M31. Our derived visual and IR distance moduli dis- agree at slightly more than a 1-{\\sigma} level. Differences in the Period-Luminosity relations between ground-based and HST observations are investigated for a subset of Cepheids. We find a significant discrepancy between ground-based and HST Period-Luminosity relations with the same Cepheids, suggesting adverse effects from photometric contam- ination in ground-based ...

  1. Galactic abundance gradients from Cepheids. α and heavy elements in the outer disk

    NARCIS (Netherlands)

    B. Lemasle; P. François; K. Genovali; V.V. Kovtyukh; G. Bono; L. Inno; C.D. Laney; L. Kaper; M. Bergemann; M. Fabrizio; N. Matsunaga; S. Pedicelli; F. Primas; M. Romaniello

    2013-01-01

    Context. Galactic abundance gradients set strong constraints to chemo-dynamical evolutionary models of the Milky Way. Given the period-luminosity relations that provide accurate distances and the large number of spectral lines, Cepheids are excellent tracers of the present-day abundance gradients. A

  2. Galactic abundance gradients from Cepheids : α and heavy elements in the outer disk

    NARCIS (Netherlands)

    Lemasle, B.; Francois, P.; Genovali, K.; Kovtyukh, V. V.; Bono, G.; Inno, L.; Laney, C. D.; Kaper, L.; Bergemann, M.; Fabrizio, M.; Matsunaga, N.; Pedicelli, S.; Primas, F.; Romaniello, M.

    2013-01-01

    Context. Galactic abundance gradients set strong constraints to chemo-dynamical evolutionary models of the Milky Way. Given the period-luminosity relations that provide accurate distances and the large number of spectral lines, Cepheids are excellent tracers of the present-day abundance gradients. A

  3. DISCOVERY OF A PAIR OF CLASSICAL CEPHEIDS IN AN INVISIBLE CLUSTER BEYOND THE GALACTIC BULGE

    Energy Technology Data Exchange (ETDEWEB)

    Dékány, I.; Palma, T. [Millennium Institute of Astrophysics, Santiago (Chile); Minniti, D. [Departamento de Ciencias Físicas, Universidad Andres Bello, República 220, Santiago (Chile); Hajdu, G.; Alonso-García, J.; Hempel, M.; Catelan, M. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Santiago (Chile); Gieren, W. [Departamento de Astronomía, Universidad de Concepción, Casilla 160 C, Concepción (Chile); Majaess, D. [Department of Astronomy and Physics, Saint Mary’s University, Halifax, NS B3H 3C3 (Canada)

    2015-01-20

    We report the discovery of a pair of extremely reddened classical Cepheid variable stars located in the Galactic plane behind the bulge, using near-infrared (NIR) time-series photometry from the VISTA Variables in the Vía Láctea Survey. This is the first time that such objects have ever been found in the opposite side of the Galactic plane. The Cepheids have almost identical periods, apparent brightnesses, and colors. From the NIR Leavitt law, we determine their distances with ∼1.5% precision and ∼8% accuracy. We find that they have a same total extinction of A(V)≃32 mag, and are located at the same heliocentric distance of 〈d〉=11.4±0.9 kpc, and less than 1 pc from the true Galactic plane. Their similar periods indicate that the Cepheids are also coeval, with an age of ∼48±3 Myr, according to theoretical models. They are separated by an angular distance of only 18.″3, corresponding to a projected separation of ∼1 pc. Their position coincides with the expected location of the Far 3 kpc Arm behind the bulge. Such a tight pair of similar classical Cepheids indicates the presence of an underlying young open cluster that is both hidden behind heavy extinction and disguised by the dense stellar field of the bulge. All our attempts to directly detect this “invisible cluster” have failed, and deeper observations are needed. (letters)

  4. Discovery of blue companions to two southern Cepheids: WW Car and FN Vel

    CERN Document Server

    Kovtyukh, V; Chekhonadskikh, F; Lemasle, B; Belik, S

    2015-01-01

    A large number of high-dispersion spectra of classical Cepheids were obtained in the region of the CaII H+K spectral lines. The analysis of these spectra allowed us to detect the presence of a strong Balmer line, H$\\epsilon$, for several Cepheids, interpreted as the signature of a blue companion: the presence of a sufficiently bright blue companion to the Cepheid results in a discernible strengthening of the CaII H + Hepsilon line relative to the CaII K line. We investigated 103 Cepheids, including those with known hot companions (B5-B6 main-sequence stars) in order to test the method. We could confirm the presence of a companion to WW Car and FN Vel (the existence of the former was only suspected before) and we found that these companions are blue hot stars. The method remains efficient when the orbital velocity changes in a binary system cannot be revealed and other methods of binarity detection are not efficient.

  5. On the neutron-capture elements across the Galactic thin disk using Cepheids

    CERN Document Server

    da Silva, R; Bono, G; Genovali, K; McWilliam, A; Cristallo, S; Bergemann, M; Buonanno, R; Fabrizio, M; Ferraro, I; Francois, P; Iannicola, G; Inno, L; Laney, C D; Kudritzki, R -P; Matsunaga, N; Nonino, M; Primas, F; Przybilla, N; Romaniello, M; Thevenin, F; Urbaneja, M A

    2015-01-01

    We present new accurate abundances for five neutron-capture (Y, La, Ce, Nd, Eu) elements in 73 classical Cepheids located across the Galactic thin disk. Individual abundances are based on high spectral resolution (R ~ 38,000) and high signal-to-noise ratio (S/N ~ 50-300) spectra collected with UVES at ESO VLT for the DIONYSOS project. Taking account for similar Cepheid abundances provided either by our group (111 stars) or available in the literature, we end up with a sample of 435 Cepheids covering a broad range in iron abundances (-1.6 < [Fe/H] < 0.6). We found, using homogeneous individual distances and abundance scales, well defined gradients for the above elements. However, the slope of the light s-process element (Y) is at least a factor of two steeper than the slopes of heavy s- (La, Ce, Nd) and r- (Eu) process elements. The s to r abundance ratio ([La/Eu]) of Cepheids shows a well defined anticorrelation with of both Eu and Fe. On the other hand, Galactic field stars attain an almost constant va...

  6. RR Lyrae and Type II Cepheid Variables Adhere to a Common Distance Relation

    CERN Document Server

    Majaess, Daniel J

    2009-01-01

    Preliminary evidence is presented reaffirming that SX Phe, RR Lyrae, and Type II Cepheid variables may be characterized by a common Wesenheit period-magnitude relation, to first order. Reliable distance estimates to RR Lyrae variables and Type II Cepheids are ascertained from a single VI-based reddening-free relation derived recently from OGLE photometry of LMC Type II Cepheids. Distances are computed to RR Lyrae (d~260 pc), and variables of its class in the galaxies IC 1613, M33, Fornax dSph, LMC, SMC, and the globular clusters M3, M15, M54, omega Cen, NGC 6441, and M92. The results are consistent with literature estimates, and in the particular cases of the SMC, M33, and IC 1613, the distances agree with that inferred from classical Cepheids to within the uncertainties: no corrections were applied to account for differences in metallicity. Moreover, no significant correlation was observed between the distances computed to RR Lyrae variables in omega Cen and their metallicity, despite a considerable spread i...

  7. MOND rotation curves for spiral galaxies with Cepheid-based distances

    NARCIS (Netherlands)

    Bottema, R; Pestana, JLG; Rothberg, B; Sanders, RH

    2002-01-01

    Rotation curves for four spiral galaxies with recently determined Cepheid-based distances are reconsidered in terms of modified Newtonian dynamics (MOND). For two of the objects, NGC 2403 and NGC 7331, the rotation curves predicted by MOND are compatible with the observed curves when these galaxies

  8. Spectroscopic Mode Identification in Slowly Pulsating Subdwarf-B Stars

    CERN Document Server

    Schoenaers, C

    2008-01-01

    Mode identification is crucial for an asteroseismological study of any significance. Contrarily to spectroscopic techniques, methods such as period-fitting and multi-colour photometry do not provide a full reconstruction of non-radial pulsations. We present a new method of spectroscopic mode identification and test it on time-series of synthetic spectra appropriate for pulsating subdwarf-B stars. We then apply it to the newly discovered slowly pulsating subdwarf-B star HD 4539.

  9. Prices versus Quantities

    DEFF Research Database (Denmark)

    Hansen, Lars Gårn; Jensen, Frank

    uncertainty. We find that the gain from eliminating compliance uncertainty may be up to 5% of gross profit while the gain from eliminating ecological uncertainty is minimal. Under landing fee regulation, the entire gain from eliminating both types of uncertainty is captured, even if the regulator’s stock......Weitzman (2002) studies the regulation of a fishery characterised by constant marginal harvest costs and shows that price regulation performs better than quantity regulation when the regulator is uncertain about the biological reproduction function (ecological uncertainty). Here, we initially...... illustrate that this result does not generalise to a search fishery, where marginal costs are allowed to depend on harvest. Hansen et al (2008) study a fishery where non-compliance with regulations is a problem. When the regulator is uncertain about non-compliance (compliance uncertainty), then landing fees...

  10. The Cepheids of NGC1866: A Precise Benchmark for the Extragalactic Distance Scale and Stellar Evolution from Modern UBVI Photometry

    CERN Document Server

    Musella, I; Stetson, P B; Raimondo, G; Brocato, E; Molinaro, R; Ripepi, V; Carini, R; Coppola, G; Walker, A R; Welch, D L

    2016-01-01

    We present the analysis of multiband time-series data for a sample of 24 Cepheids in the field of the Large Magellanic Cloud cluster NGC1866. Very accurate BVI VLT photometry is combined with archival UBVI data, covering a large temporal window, to obtain precise mean magnitudes and periods with typical errors of 1-2% and of 1 ppm, respectively. These results represent the first accurate and homogeneous dataset for a substantial sample of Cepheid variables belonging to a cluster and hence sharing common distance, age and original chemical composition. Comparisons of the resulting multiband Period-Luminosity and Wesenheit relations to both empirical and theoretical results for the Large Magellanic Cloud are presented and discussed to derive the distance of the cluster and to constrain the mass-luminosity relation of the Cepheids. The adopted theoretical scenario is also tested by comparison with independent calibrations of the Cepheid Wesenheit zero point based on trigonometric parallaxes and Baade-Wesselink t...

  11. Convective heat transfer characteristics of laminar pulsating pipe air flow

    Science.gov (United States)

    Habib, M. A.; Attya, A. M.; Eid, A. I.; Aly, A. Z.

    Heat transfer characteristics to laminar pulsating pipe flow under different conditions of Reynolds number and pulsation frequency were experimentally investigated. The tube wall of uniform heat flux condition was considered. Reynolds number was varied from 780 to 1987 while the frequency of pulsation ranged from 1 to 29.5Hz. The results showed that the relative mean Nusselt number is strongly affected by pulsation frequency while it is slightly affected by Reynolds number. The results showed enhancements in the relative mean Nusselt number. In the frequency range of 1-4Hz, an enhancement up to 30% (at Reynolds number of 1366 and pulsation frequency of 1.4Hz) was obtained. In the frequency range of 17-25Hz, an enhancement up to 9% (at Reynolds number of 1366 and pulsation frequency of 17.5Hz) was indicated. The rate of enhancement of the relative mean Nusselt number decreased as pulsation frequency increased or as Reynolds number increased. A reduction in relative mean Nusselt number occurred outside these ranges of pulsation frequencies. A reduction in relative mean Nusselt number up to 40% for pulsation frequency range of 4.1-17Hz and a reduction up to 20% for pulsation frequency range of 25-29.5Hz for Reynolds numbers range of 780-1987 were considered. This reduction is directly proportional to the pulsation frequency. Empirical dimensionless equations have been developed for the relative mean Nusselt number that related to Reynolds number (750

  12. Convective heat transfer characteristics of laminar pulsating pipe air flow

    Energy Technology Data Exchange (ETDEWEB)

    Habib, M.A. [King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia); Attya, A.M.; Eid, A.I.; Aly, A.Z. [Department of Mechanical Engineering, Cairo Univ. (Egypt)

    2002-02-01

    Heat transfer characteristics to laminar pulsating pipe flow under different conditions of Reynolds number and pulsation frequency were experimentally investigated. The tube wall of uniform heat flux condition was considered. Reynolds number was varied from 780 to 1987 while the frequency of pulsation ranged from 1 to 29.5 Hz. The results showed that the relative mean Nusselt number is strongly affected by pulsation frequency while it is slightly affected by Reynolds number. The results showed enhancements in the relative mean Nusselt number. In the frequency range of 1-4 Hz, an enhancement up to 30% (at Reynolds number of 1366 and pulsation frequency of 1.4 Hz) was obtained. In the frequency range of 17-25 Hz, an enhancement up to 9% (at Reynolds number of 1366 and pulsation frequency of 17.5 Hz) was indicated. The rate of enhancement of the relative mean Nusselt number decreased as pulsation frequency increased or as Reynolds number increased. A reduction in relative mean Nusselt number occurred outside these ranges of pulsation frequencies. A reduction in relative mean Nusselt number up to 40% for pulsation frequency range of 4.1-17 Hz and a reduction up to 20% for pulsation frequency range of 25-29.5 Hz for Reynolds numbers range of 780-1987 were considered. This reduction is directly proportional to the pulsation frequency. Empirical dimensionless equations have been developed for the relative mean Nusselt number that related to Reynolds number (750

  13. Period-Luminosity relations derived from the OGLE-III first-overtone mode Cepheids in the Magellanic Clouds

    Science.gov (United States)

    Bhardwaj, Anupam; Ngeow, Chow-Choong; Kanbur, Shashi M.; Singh, Harinder P.

    2016-06-01

    We present multiband Period-Luminosity (PL) relations for first-overtone mode Cepheids in the Small Magellanic Cloud (SMC). We derive optical band PL relations and the Wesenheit function using VI mean magnitudes from the Optical Gravitational Lensing Experiment (OGLE-III) survey. We cross-match OGLE-III first-overtone mode Cepheids to the 2MASS and SAGE-SMC catalogues to derive PL relations at near-infrared (JHKs) and mid-infrared (3.6 and 4.5 μm) wavelengths. We test for possible non-linearities in these PL relations using robust statistical tests and find a significant break only in the optical band PL relations at 2.5 d for first-overtone mode Cepheids. We do not find statistical evidence for a non-linearity in these PL relations at 1 d. The multiband PL relations for fundamental-mode Cepheids in the SMC also exhibit a break at 2.5 d. We suggest that the period break around 2.5 d is related to sharp changes in the light-curve parameters for SMC Cepheids. We also derive new optical and mid-infrared band PL relations for first-overtone mode Cepheids in the Large Magellanic Cloud (LMC). We compare multiband PL relations for first-overtone mode Cepheids in the Magellanic Clouds and find a significant difference in the slope of the V-band PL relations but not for I-band PL relations. The slope of PL relations are found to be consistent in most of the infrared bands. A relative distance modulus of Δμ = 0.49 ± 0.02 mag between the two clouds is estimated using multiband PL relations for the first-overtone mode Cepheids in the SMC and LMC.

  14. RY Sgr: pulsation period variations reinterpreted

    Energy Technology Data Exchange (ETDEWEB)

    Lawson, W.A.; Cottrell, P.L.

    1988-04-01

    An analysis of recent observations of RY Sgr has shown that the times of light maxima can no longer be represented by a quadratic solution where the pulsation period decreases linearly with time. A cubic solution gives a better fit to the data, but a series of linear piecewise solutions satisfy the O-C residuals to within the observational uncertainty. We believe that the latter interpretation provides a more astrophysical explanation. Finally, a likely mass for the RCB stars of approx. 0.7 of the solar mass has been derived from observations of the RCB stars in the Large Magellanic Cloud.

  15. Design of a Hydrogen Pulsating Heat Pipe

    Science.gov (United States)

    Liu, Yumeng; Deng, Haoren; Pfotenhauer, John; Gan, Zhihua

    In order to enhance the application of a cryocooler that provides cooling capacity at the cold head location, and effectively spread that cooling over an extended region, one requires an efficient heat transfer method. The pulsating heat pipe affords a highly effective heat transfer component that has been extensively researched at room temperature, but is recently being investigated for cryogenic applications. This paper describes the design. The experimental setup is designed to characterize the thermal performance of the PHP as a function of the applied heat, number of turns, filling ratio, inclination angle, and length of adiabatic section.

  16. Measurement and evaluation of pulsating water jet peening intensity

    OpenAIRE

    Hlaváček, Petr

    2013-01-01

    Pulsating water jet peening is a promising method in surface treatment. It has the potential to induce compressive residual stresses that benefit the fatigue life of components similar to the other peening process. In this paper experimental results obtained by action of pulsating water jet on Almen strips are presented.

  17. Effect of pulsating water jet peening on stainless steel

    OpenAIRE

    Hlaváček, Petr

    2015-01-01

    Effects of action of pulsating water jet on polished surface of the stainless steel AISI 316L are presented. Surface slip bands appeared after this treatment. In the most severe conditions, microcracks were formed. Hardness measurement showed that the affected layer was thinner than 60 μm. Application of the pulsating water jet has beneficial effect on the fatigue life of the material.

  18. Pulsating laminar fully developed channel and pipe flows.

    Science.gov (United States)

    Haddad, Kais; Ertunç, Ozgür; Mishra, Manoranjan; Delgado, Antonio

    2010-01-01

    Analytical investigations are carried out on pulsating laminar incompressible fully developed channel and pipe flows. An analytical solution of the velocity profile for arbitrary time-periodic pulsations is derived by approximating the pulsating flow variables by a Fourier series. The explicit interdependence between pulsations of velocity, mass-flow rate, pressure gradient, and wall shear stress are shown by using the proper dimensionless parameters that govern the flow. Utilizing the analytical results, the scaling laws for dimensionless pulsation amplitudes of the velocity, mass-flow rate, pressure gradient, and wall shear stress are analyzed as functions of the dimensionless pulsation frequency. Special attention has been given to the scaling laws describing the flow reversal phenomenon occurring in pulsating flows, such as the condition for flow reversal, the dependency of the reversal duration, and the amplitude. It is shown that two reversal locations away from the wall can occur in pulsating flows in pipes and channels and the reversed amount of mass per period reaches a maximum at a certain dimensionless frequency for a given amplitude of mass-flow rate fluctuations. These analyses are numerically conducted for pipe and channel flows over a large frequency range in a comparative manner. PMID:20365456

  19. Analysis of low-frequency pulsations in Francis turbines

    Energy Technology Data Exchange (ETDEWEB)

    Fay, A A, E-mail: arpad.fay@t-online.h [Department of Fluid and Heat Engineering, University of Miskolc, Miskolc, H - 3515 (Hungary)

    2010-08-15

    The power pulsations of Francis turbines are discussed which occur regularly at part load but sometimes even at full load. The main tool of the analysis is the torque equation of Francis runners which has been derived from basic mechanics neglecting only very small effects. The various potential pulsation sources are grouped according to their places of origin, namely those occurring (i) in the inlet flow path (rotor-stator interaction) (ii) at the runner (interblade vortices, rotating stall) and (iii) in the draft tube (spiraling vortex flow). Their effects are discussed assuming certain ideal symmetrical velocity distributions. The main theoretical conclusions are: (1) The shaft torque pulsations may be determined from the turbulent velocity field. (2) In case of steady quasi-axisymmetric inflow the main pulsation source does not belong to group (i). (3) Of the pulsation sources (ii) and (iii) one is self-excited while the other is forced. (4) If the discharge is constant and the draft tube vortex rotates uniformly, then (iii) cannot affect the shaft torque. (5) If (iii) is the main source of the torque pulsations then discharge fluctuation must appear. (6) If the discharge pulsation is too small then either (ii) is the main source, or essential interactions of (ii) and (iii) may be expected. Thus, the torque equation is seen as a powerful tool of the analysis, and for future research attention is focused to the discharge pulsation.

  20. Heat transfer characteristics of pulsated turbulent pipe flow

    Science.gov (United States)

    Habib, M. A.; Said, S. A. M.; Al-Farayedhi, A. A.; Al-Dini, S. A.; Asghar, A.; Gbadebo, S. A.

    Heat Transfer characteristics of pulsated turbulent pipe flow under different conditions of pulsation frequency, amplitude and Reynolds number were experimentally investigated. The pipe wall was kept at uniform heat flux. Reynolds number was varied from 5000 to 29 000 while frequency of pulsation ranged from 1 to 8 Hz. The results show an enhancement in the local Nusselt number at the entrance region. The rate of enhancement decreased as Re increased. Reduction of heat transfer coefficient was observed at higher frequencies and the effect of pulsation is found to be significant at high Reynolds number. It can be concluded that the effect of pulsation on the mean Nusselt numbers is insignificant at low values of Reynolds number.

  1. SABRE observations of Pi2 pulsations: case studies

    Directory of Open Access Journals (Sweden)

    E. G. Bradshaw

    Full Text Available The characteristics of substorm-associated Pi2 pulsations observed by the SABRE coherent radar system during three separate case studies are presented. The SABRE field of view is well positioned to observe the differences between the auroral zone pulsation signature and that observed at mid-latitudes. During the first case study the SABRE field of view is initially in the eastward electrojet, equatorward and to the west of the substorm-enhanced electrojet current. As the interval progresses, the western, upward field-aligned current of the substorm current wedge moves westward across the longitudes of the radar field of view. The westward motion of the wedge is apparent in the spatial and temporal signatures of the associated Pi2 pulsation spectra and polarisation sense. During the second case study, the complex field-aligned and ionospheric currents associated with the pulsation generation region move equatorward into the SABRE field of view and then poleward out of it again after the third pulsation in the series. The spectral content of the four pulsations during the interval indicate different auroral zone and mid-latitude signatures. The final case study is from a period of low magnetic activity when SABRE observes a Pi2 pulsation signature from regions equatorward of the enhanced substorm currents. There is an apparent mode change between the signature observed by SABRE in the ionosphere and that on the ground by magnetometers at latitudes slightly equatorward of the radar field of view. The observations are discussed in terms of published theories of the generation mechanisms for this type of pulsation. Different signatures are observed by SABRE depending on the level of magnetic activity and the position of the SABRE field of view relative to the pulsation generation region. A twin source model for Pi2 pulsation generation provides the clearest explanation of the signatures observed.

  2. Computational model of miniature pulsating heat pipes.

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, Mario J.; Givler, Richard C.

    2013-01-01

    The modeling work described herein represents Sandia National Laboratories (SNL) portion of a collaborative three-year project with Northrop Grumman Electronic Systems (NGES) and the University of Missouri to develop an advanced, thermal ground-plane (TGP), which is a device, of planar configuration, that delivers heat from a source to an ambient environment with high efficiency. Work at all three institutions was funded by DARPA/MTO; Sandia was funded under DARPA/MTO project number 015070924. This is the final report on this project for SNL. This report presents a numerical model of a pulsating heat pipe, a device employing a two phase (liquid and its vapor) working fluid confined in a closed loop channel etched/milled into a serpentine configuration in a solid metal plate. The device delivers heat from an evaporator (hot zone) to a condenser (cold zone). This new model includes key physical processes important to the operation of flat plate pulsating heat pipes (e.g. dynamic bubble nucleation, evaporation and condensation), together with conjugate heat transfer with the solid portion of the device. The model qualitatively and quantitatively predicts performance characteristics and metrics, which was demonstrated by favorable comparisons with experimental results on similar configurations. Application of the model also corroborated many previous performance observations with respect to key parameters such as heat load, fill ratio and orientation.

  3. Secular Evolution in Mira Variable Pulsations

    CERN Document Server

    Templeton, M R; Willson, L A

    2005-01-01

    Stellar evolution theory predicts that asymptotic giant branch stars undergo a series of short thermal pulses that significantly change their luminosity and mass on timescales of hundreds to thousands of years. Secular changes in these stars resulting from thermal pulses can be detected as measurable changes in period if the star is undergoing Mira pulsations. The American Association of Variable Star Observers (AAVSO) International Database currently contains visual data for over 1500 Mira variables. Light curves for these stars span nearly a century in some cases, making it possible to study the secular evolution of the pulsation behavior on these timescales. In this paper, we present the results of our study of period change in 547 Mira variables using data from the AAVSO. We find non-zero rates of period change, dlnP/dt, at the 2-sigma significance level in 57 of the 547 stars, at the 3-sigma level in 21 stars, and at the level of 6-sigma or greater in eight of the 547. The latter eight stars have been pr...

  4. Determination of discharge during pulsating flow

    Science.gov (United States)

    Thompson, T.H.

    1968-01-01

    Pulsating flow in an open channel is a manifestation of unstable-flow conditions in which a series of translatory waves of perceptible magnitude develops and moves rapidly downstream. Pulsating flow is a matter of concern in the design and operation of steep-gradient channels. If it should occur at high stages in a channel designed for stable flow, the capacity of the channel may be inadequate at a discharge that is much smaller than that for which the channel was designed. If the overriding translatory wave carries an appreciable part of the total flow, conventional stream-gaging procedures cannot be used to determine the discharge; neither the conventional instrumentation nor conventional methodology is adequate. A method of determining the discharge during pulsating flow was tested in the Santa Anita Wash flood control channel in Arcadia, Calif., April 16, 1965. Observations of the dimensions and velocities of translatory waves were made during a period of controlled reservoir releases of about 100, 200, and 300 cfs (cubic feet per second). The method of computing discharge was based on (1) computation of the discharge in the overriding waves and (2) computation of the discharge in the shallow-depth, or overrun, part of the flow. Satisfactory results were obtained by this method. However, the procedure used-separating the flow into two components and then treating the shallow-depth component as though it were steady--has no theoretical basis. It is simply an expedient for use until laboratory investigation can provide a satisfactory analytical solution to the problem of computing discharge during pulsating flow. Sixteen months prior to the test in Santa Anita Wash, a robot camera had been designed .and programmed to obtain the data needed to compute discharge by the method described above. The photographic equipment had been installed in Haines Creek flood control channel in Los Angeles, Calif., but it had not been completely tested because of the infrequency of

  5. VizieR Online Data Catalog: OGLE LC classification of MC Cepheids (Garcia-Varela+, 2016)

    Science.gov (United States)

    Garcia-Varela, A.; Munoz, J. R.; Sabogal, B. E.; Vargas Dominguez, S.; Martinez, J.

    2016-08-01

    OGLE-II and OGLE-IV observations of Cepheid variables in the LMC and SMC galaxies were collected with the 1.3m Warsaw telescope, at Las Campanas Observatory, Chile (Udalski et al. 1999, J/AcA/49/223; 1999, J/AcA/49/437; 2015AcA....65....1U). While Cepheid catalogs for the OGLE-II fundamental mode contain 771 and 1319 stars for the LMC and SMC, respectively, OGLE-IV has a nearly complete collection (2429 and 2739 for the LMC and SMC, respectively), covering practically the whole Magellanic System with a time baseline of a little more than five years (Soszynski et al. 2015AcA....65..329S). (1 data file).

  6. X-ray Detection of the Cluster Containing the Cepheid S Mus

    CERN Document Server

    Evans, Nancy Remage; Wolk, Scott J; Guinan, Edward; Engle, Scott; Bond, Howard E; Schaefer, Gail H; Karovska, Margarita; DePasquale, Joseph; Tingle, Evan

    2014-01-01

    The galactic Cepheid S Muscae has recently been added to the important list of Cepheids linked to open clusters, in this case the sparse young cluster ASCC 69. Low-mass members of a young cluster are expected to have rapid rotation and X-ray activity, making X-ray emission an excellent way to discriminate them from old field stars. We have made an XMM-Newton observation centered on S Mus and identified (Table 1) a population of X-ray sources whose near-IR 2MASS counterparts lie at locations in the J, (J-K) color-magnitude diagram consistent with cluster membership at the distance of S Mus. Their median energy and X-ray luminosity are consistent with young cluster members as distinct from field stars. These strengthen the association of S Mus with the young cluster, making it a potential Leavitt Law (Period-Luminosity relation) calibrator.

  7. The Detailed Forms of the LMC Cepheid PL and PLC Relations

    OpenAIRE

    Koen, C.; Kanbur, S.; Ngeow, C.

    2007-01-01

    Possible deviations from linearity of the LMC Cepheid PL and PLC relations are investigated. Two datasets are studied, respectively from the OGLE and MACHO projects. A nonparametric test, based on linear regression residuals, suggests that neither PL relation is linear. If colour dependence is allowed for then the MACHO PL relation is found to deviate more significantly from the linear, while the OGLE PL relation is consistent with linearity. These finding are confirmed by fitting "Generalise...

  8. Neutron-capture elements across the Galactic thin disk using Cepheids

    Science.gov (United States)

    da Silva, R.; Lemasle, B.; Bono, G.; Genovali, K.; McWilliam, A.; Cristallo, S.; Bergemann, M.; Buonanno, R.; Fabrizio, M.; Ferraro, I.; François, P.; Iannicola, G.; Inno, L.; Laney, C. D.; Kudritzki, R.-P.; Matsunaga, N.; Nonino, M.; Primas, F.; Przybilla, N.; Romaniello, M.; Thévenin, F.; Urbaneja, M. A.

    2016-02-01

    We present new accurate abundances for five neutron-capture elements (Y, La, Ce, Nd, Eu) in 73 classical Cepheids located across the Galactic thin disk. Individual abundances are based on high spectral resolution (R ~ 38 000) and high signal-to-noise ratio (S/N ~ 50-300) spectra collected with UVES at ESO VLT for the DIONYSOS project. Taking into account similar Cepheid abundances provided by our group (111 stars) and available in the literature, we end up with a sample of 435 Cepheids covering a broad range in iron abundances (-1.6 mild enhancement in La only when they approach solar iron abundance. The [Y/Eu] ratio shows slight evidence of a correlation with Eu and, in particular, with iron abundance for field Galactic stars. We also investigated the s-process index ([hs/ls]) and we found a well-defined anticorrelation, as expected, between [La/Y] and iron abundance. Moreover, we found a strong correlation between [La/Y] and [La/Fe] and, in particular, a clear separation between Galactic and Sagittarius red giants. Finally, the comparison between predictions for low-mass asymptotic giant branch stars and the observed[La/Y] ratio indicate a very good agreement over the entire metallicity range covered by Cepheids. However, the observed spread at fixed iron content is larger than predicted by current models. Based on spectra collected with the UVES spectrograph available at the ESO Very Large Telescope (VLT), Cerro Paranal, Chile (ESO Proposals: 081.D-0928(A), PI: S. Pedicelli; 082.D-0901(A), PI: S. Pedicelli; 089.D-0767(C), PI: K. Genovali).Tables 2, 3, 4, and 7 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/586/A125

  9. Pulsating hydraulic fracturing technology in low permeability coal seams

    Institute of Scientific and Technical Information of China (English)

    Wang Wenchao; Li Xianzhong; Lin Baiquan; Zhai Cheng

    2015-01-01

    Based on the difficult situation of gas drainage in a single coal bed of high gas content and low perme-ability, we investigate the technology of pulsating hydraulic pressure relief, the process of crank plunger movement and the mechanism of pulsating pressure formation using theoretical research, mathematical modeling and field testing. We analyze the effect of pulsating pressure on the formation and growth of fractures in coal by using the pulsating hydraulic theory in hydraulics. The research results show that the amplitude of fluctuating pressure tends to increase in the case where the exit is blocked, caused by pulsating pressure reflection and frictional resistance superposition, and it contributes to the growth of fractures in coal. The crack initiation pressure of pulsating hydraulic fracturing is 8 MPa, which is half than that of normal hydraulic fracturing;the pulsating hydraulic fracturing influence radius reaches 8 m. The total amount of gas extraction is increased by 3.6 times, and reaches 50 L/min at the highest point. The extraction flow increases greatly, and is 4 times larger than that of drilling without fracturing and 1.2 times larger than that of normal hydraulic fracturing. The technology provides a technical measure for gas drainage of high gas content and low permeability in the single coal bed.

  10. DISCOVERY OF THE HOST CLUSTER FOR THE FUNDAMENTAL CEPHEID CALIBRATOR ZETA GEMINORUM

    International Nuclear Information System (INIS)

    New and existing CORAVEL, UBVJHKs , HST, HIP/Tycho, ARO, KPNO, and DAO observations imply that the fundamental Cepheid calibrator ζ Gem is a cluster member. The following parameters were inferred for ζ Gem from cluster membership and are tied to new spectral classifications (DAO) established for 26 nearby stars (e.g., HD53588/B7.5IV, HD54692/B9.5IV): EB–V = 0.02 ± 0.02, log τ = 7.85 ± 0.15, and d = 355 ± 15 pc. The mean distance to ζ Gem from cluster membership and six recent estimates (e.g., IRSB) is d=363±9(σx-bar )±26 (σ) pc. The results presented here support the color-excess and HST parallax derived for the Cepheid by Benedict et al. Forthcoming precise proper motions (DASCH) and Chandra/XMM-Newton observations of the broader field may be employed to identify cluster members, bolster the cluster's existence, and provide stronger constraints on the Cepheid's fundamental parameters.

  11. Galactic abundance gradients from Cepheids: alpha and heavy elements in the outer disk

    CERN Document Server

    Lemasle, B; Genovali, K; Kovtyukh, V V; Bono, G; Inno, L; Laney, C D; Kaper, L; Bergemann, M; Fabrizio, M; Matsunaga, N; Pedicelli, S; Primas, F; Romaniello, M

    2013-01-01

    Context: Galactic abundance gradients set strong constraints to chemo-dynamical evolutionary models of the Milky Way. Given the PL relations that provide accurate distances and the large number of spectral lines, Cepheids are excellent tracers of the present-day abundance gradients. Aims: We want to measure the Galactic abundance gradient of several chemical elements. While the slope of the Cepheid iron gradient did not vary much from the very first studies, the gradients of the other elements are not that well constrained. In this paper we focus on the inner and outer regions of the Galactic thin disk. Methods: We use HR spectra (FEROS, ESPADONS, NARVAL) to measure the abundances of several light (Na, Al), alpha (Mg, Si, S, Ca), and heavy elements (Y, Zr, La, Ce, Nd, Eu) in a sample of 65 Milky Way Cepheids. Combining these results with accurate distances from period-Wesenheit relations in the NIR enables us to determine the abundance gradients in the Milky Way. Results: Our results are in good agreement wit...

  12. A Search for Mass Loss on the Cepheid Instability Strip using HI 21-cm Line Observations

    CERN Document Server

    Matthews, L D; Evans, N R

    2016-01-01

    We present the results of a search for HI 21-cm line emission from the circumstellar environments of four Galactic Cepheids (RS Pup, X Cyg, $\\zeta$ Gem, and T Mon) based on observations with the Karl G. Jansky Very Large Array. The observations were aimed at detecting gas associated with previous or ongoing mass loss. Near the long-period Cepheid T Mon, we report the detection of a partial shell-like structure whose properties appear consistent with originating from an earlier epoch of Cepheid mass loss. At the distance of T Mon, the nebula would have a mass (HI+He) of $\\sim0.5M_{\\odot}$, or $\\sim$6\\% of the stellar mass. Assuming that one-third of the nebular mass comprises swept-up interstellar gas, we estimate an implied mass-loss rate of ${\\dot M}\\sim (0.6-2)\\times10^{-5} M_{\\odot}$ yr$^{-1}$. No clear signatures of circumstellar emission were found toward $\\zeta$ Gem, RS Pup, or X Cyg, although in each case, line-of-sight confusion compromised portions of the spectral band. For the undetected stars, we d...

  13. The influential effect of blending, bump, changing period and eclipsing Cepheids on the Leavitt law

    CERN Document Server

    García-Varela, A; Sabogal, B E; Domínguez, S Vargas; Martínez, J

    2016-01-01

    The investigation of the non-linearity of the Leavitt law is a topic that began more than seven decades ago, when some of the studies in this field found that the Leavitt law has a break at about ten days. The goal of this work is to investigate a possible statistical cause of this non-linearity. By applying linear regressions to OGLE-II and OGLE-IV data, we find that, in order to obtain the Leavitt law by using linear regression, robust techniques to deal with influential points and/or outliers are needed instead of the ordinary least-squares regression traditionally used. In particular, by using $M$- and $MM$-regressions we establish firmly and without doubts the linearity of the Leavitt law in the Large Magellanic Cloud, without rejecting or excluding Cepheid data from the analysis. This implies that light curves of Cepheids suggesting blending, bumps, eclipses or period changes, do not affect the Leavitt law for this galaxy. For the SMC, including this kind of Cepheids, it is not possible to find an adequ...

  14. Constraining the Thin Disc Initial Mass Function using Galactic Classical Cepheids

    CERN Document Server

    Mor, R; Figueras, F; Lemasle, B

    2016-01-01

    Context: The Initial Mass Function (IMF) plays a crucial role on galaxy evolution and its implications on star formation theory make it a milestone for the next decade. It is in the intermediate and high mass ranges where the uncertainties of the IMF are larger. This is a major subject of debate and analysis both for Galactic and extragalactic science. Aims: Our goal is to constrain the IMF of the Galactic thin disc population using both Galactic Classical Cepheids and Tycho-2 data. Methods: For the first time the Besan\\c{c}on Galaxy Model (BGM) has been used to characterise the Galactic population of the Classical Cepheids. We have modified the age configuration in the youngest populations of the BGM thin disc model to avoid artificial discontinuities in the age distribution of the simulated Cepheids. Three statistical methods, optimized for different mass ranges, have been developed and applied to search for the best IMF that fits the observations. This strategy allows us to quantify variations in the Star ...

  15. Hubble Space Telescope Fine Guidance Sensor Parallaxes of Galactic Cepheid Variable Stars: Period-Luminosity Relations

    CERN Document Server

    Benedict, G F; Feast, M W; Barnes, T G; Harrison, T E; Patterson, R J; Menzies, J W; Bean, J L; Freedman, W L; Arthur, Barbara E. Mc; Feast, Michael W.; Barnes, Thomas G.; Harrison, Thomas E.; Patterson, Richard J.; Menzies, John W.; Bean, Jacob L.; Freedman, Wendy L.

    2006-01-01

    (abridged) We present new absolute trigonometric parallaxes and relative proper motions for nine Galactic Cepheid variable stars: l Car, zeta Gem, beta Dor, W Sgr, X Sgr, Y Sgr, FF Aql, T Vul, and RT Aur. We obtain these results with astrometric data from Fine Guidance Sensor 1r, a white-light interferometer on Hubble Space Telescope. We find absolute parallaxes with an average sigma_pi/pi = 8%. Two stars (FF Aql and W Sgr) required the inclusion of binary astrometric perturbations, providing Cepheid mass estimates. With these parallaxes we compute absolute magnitudes in V, I, K, and Wesenheit W_{VI} bandpasses corrected for interstellar extinction and Lutz-Kelker-Hanson bias. Adding our previous absolute magnitude determination for delta Cep, we construct Period-Luminosity relations for ten Galactic Cepheids. We compare our new Period-Luminosity relations with those adopted by several recent investigations, including the Freedman and Sandage H_0 projects. Adopting our Period-Luminosity relationship would ten...

  16. Towards a Determination of Definitive Parameters for the Long Period Cepheid S Vulpeculae

    CERN Document Server

    Turner, David G

    2014-01-01

    A new compilation of UBV data for stars near the Cepheid S Vul incorporates BV observations from APASS and NOMAD to augment UBV observations published previously. A reddening analysis yields mean colour excesses and distance moduli for two main groups of stars in the field: the sparse cluster Turner 1 and an anonymous background group of BA stars. The former appears to be 1.07+-0.12 kpc distant and reddened by E(B-V)=0.45+-0.05, with an age of 10^9 yrs. The previously overlooked latter group is 3.48+-0.19 kpc distant and reddened by E(B-V)=0.78+-0.02, with an age of 1.3x10^7 yrs. Parameters inferred for S Vul under the assumption that it belongs to the distant group, as also argued by 2MASS data, are all consistent with similar results for other cluster Cepheids and Cepheid-like supergiants.

  17. The Influential Effect of Blending, Bump, Changing Period, and Eclipsing Cepheids on the Leavitt Law

    Science.gov (United States)

    García-Varela, A.; Muñoz, J. R.; Sabogal, B. E.; Vargas Domínguez, S.; Martínez, J.

    2016-06-01

    The investigation of the nonlinearity of the Leavitt law (LL) is a topic that began more than seven decades ago, when some of the studies in this field found that the LL has a break at about 10 days. The goal of this work is to investigate a possible statistical cause of this nonlinearity. By applying linear regressions to OGLE-II and OGLE-IV data, we find that to obtain the LL by using linear regression, robust techniques to deal with influential points and/or outliers are needed instead of the ordinary least-squares regression traditionally used. In particular, by using M- and MM-regressions we establish firmly and without doubt the linearity of the LL in the Large Magellanic Cloud, without rejecting or excluding Cepheid data from the analysis. This implies that light curves of Cepheids suggesting blending, bumps, eclipses, or period changes do not affect the LL for this galaxy. For the Small Magellanic Cloud, when including Cepheids of this kind, it is not possible to find an adequate model, probably because of the geometry of the galaxy. In that case, a possible influence of these stars could exist.

  18. White dwarf evolution - Cradle-to-grave constraints via pulsation

    Science.gov (United States)

    Kawaler, Steven D.

    1990-01-01

    White dwarf evolution, particularly in the early phases, is not very strongly constrained by observation. Fortunately, white dwarfs undergo nonradial pulsation in three distinct regions of the H-R diagram. These pulsations provide accurate masses, surface compositional structure and rotation velocities, and help constrain other important physical properties. We demonstrate the application of the tools of stellar seismology to white dwarf evolution using the hot white dwarf star PG 1159-035 and the cool DAV (or ZZ Ceti) stars as examples. From pulsation studies, significant challenges to the theory of white dwarf evolution emerge.

  19. Pc3 pulsations during variable IMF conditions

    Directory of Open Access Journals (Sweden)

    U. Villante

    Full Text Available Pc3 geomagnetic field fluctuations detected at low latitude (L'Aquila, Italy during the passage of a high velocity solar wind stream, characterized by variable interplanetary magnetic field conditions, are analyzed. Higher frequency resonant fluctuations and lower frequency phenomena are simultaneously observed; the intermittent appearance and the variable frequency of the longer period modes can be well interpreted in terms of the variable IMF elements; moreover their polarization characteristics are consistent with an origin related to external waves propagating in antisunward direction. A comparison with simultaneous observations performed at Terra Nova Bay (Antarctica provides additional evidence for a clear relationship between the IMF and Pc3 pulsations also at very high latitudes.

    Key words. Magnetospheric physics (MHD waves and instabilities; solar wind · magnetosphere interactions

  20. Quantity Stickiness versus Stackelberg Leadership

    Science.gov (United States)

    Ferreira, F. A.

    2008-10-01

    We study the endogenous Stackelberg relations in a dynamic market. We analyze a twice-repeated duopoly where, in the beginning, each firm chooses either a quantity-sticky production mode or a quantity-flexible production mode. The size of the market becomes observable after the first period. In the second period, a firm can adjust its quantity if, and only if, it has adopted the flexible mode. Hence, if one firm chooses the sticky mode whilst the other chooses the flexible mode, then they respectively play the roles of a Stackelberg leader and a Stackelberg follower in the second marketing period. We compute the supply quantities at equilibrium and the corresponding expected profits of the firms. We also analyze the effect of the slope parameter of the demand curve on the expected supply quantities and on the profits.

  1. Quantity Stickiness versus Stackelberg Leadership

    International Nuclear Information System (INIS)

    We study the endogenous Stackelberg relations in a dynamic market. We analyze a twice-repeated duopoly where, in the beginning, each firm chooses either a quantity-sticky production mode or a quantity-flexible production mode. The size of the market becomes observable after the first period. In the second period, a firm can adjust its quantity if, and only if, it has adopted the flexible mode. Hence, if one firm chooses the sticky mode whilst the other chooses the flexible mode, then they respectively play the roles of a Stackelberg leader and a Stackelberg follower in the second marketing period. We compute the supply quantities at equilibrium and the corresponding expected profits of the firms. We also analyze the effect of the slope parameter of the demand curve on the expected supply quantities and on the profits.

  2. OGLE-ing the Magellanic System: Three-dimensional structure of the Clouds and the Bridge using classical Cepheids

    CERN Document Server

    Jacyszyn-Dobrzeniecka, Anna M; Mróz, P; Skowron, J; Soszyński, I; Udalski, A; Pietrukowicz, P; Kozłowski, S; Wyrzykowski, Ł; Poleski, R; Pawlak, M; Szymański, M K; Ulaczyk, K

    2016-01-01

    We analyzed a sample of 9418 fundamental-mode and first-overtone classical Cepheids from the OGLE-IV Collection of Classical Cepheids. The distance to each Cepheid was calculated using the period-luminosity relation for the Wesenheit magnitude, fitted to our data. The classical Cepheids in the LMC are situated mainly in the bar and in the northern arm. The eastern part of the LMC is closer to us and the plane fit to the whole LMC sample yields the inclination i=24.2+-0.6 deg and position angle P.A.=151.4+-1.5 deg. We redefined the LMC bar by extending it in the western direction and found no offset from the plane of the LMC contrary to previous studies. On the other hand, we found that the northern arm is offset from a plane by about -0.5 kpc, which was not observed before. The age distribution of the LMC Cepheids shows one maximum at about 100 Myr. We demonstrate that the SMC has a non-planar structure and can be described as an extended ellipsoid. We identified two large ellipsoidal off-axis structures in t...

  3. Period-Luminosity relations derived from the OGLE-III First-overtone mode Cepheids in the Magellanic Clouds

    CERN Document Server

    Bhardwaj, Anupam; Kanbur, Shashi M; Singh, Harinder P

    2016-01-01

    We present multi-band Period-Luminosity (PL) relations for first-overtone mode Cepheids in the Small Magellanic Cloud (SMC). We derive optical band PL relations and the Wesenheit function using $VI$ mean magnitudes from the Optical Gravitational Lensing Experiment (OGLE-III) survey. We cross-match OGLE-III first-overtone mode Cepheids to the 2MASS and SAGE-SMC catalogs to derive PL relations at near-infrared ($JHK_s$) and mid-infrared ($3.6~\\&~4.5\\mu\\mathrm{m}$) wavelengths. We test for possible non-linearities in these PL relations using robust statistical tests and find a significant break only in the optical-band PL relations at 2.5 days for first-overtone mode Cepheids. We do not find statistical evidence for a non-linearity in these PL relations at 1 day. The multi-band PL relations for fundamental-mode Cepheids in the SMC also exhibit a break at 2.5 days. We suggest that the period break around 2.5 days is related to sharp changes in the light curve parameters for SMC Cepheids. We also derive new op...

  4. Micro-Channel Embedded Pulsating Heat Pipes Project

    Data.gov (United States)

    National Aeronautics and Space Administration — As the need for thermal control technology becomes more demanding Micro-Channel Embedded Pulsating Heat Pipes (ME-PHPs) represents a sophisticated and enabling...

  5. Canards in a rheodynamic model of cardiac pressure pulsations

    Institute of Scientific and Technical Information of China (English)

    Xie Feng; Chen Xian-Feng

    2007-01-01

    This paper reports on the canard phenomenon occurring in a rheodynamic model of cardiac pressure pulsations. By singular perturbation techniques the corresponding parameter value at which canards exist is obtained. The physiological significance of canards in this model is given.

  6. Search of Secondary Pulsation Modes: Globular cluster (NGC 6496)

    CERN Document Server

    Joshi, Gireesh C

    2016-01-01

    The Fourier-discrete-peridogram are used to identify pulsation modes in variables. We have found two pulsation modes in V1 and V2 among 13 new variables as described by Abbas et al.. The five variables V9 to V13 are not shown close to periodic values by analysis of the frequency distribution of multi-band data and also create difficulty to describe their varied nature. The multi-band periodic values of V1 and V6 are matched with known literature values. The scattering of the varied nature of secondary pulsation modes is eliminated by moving average methodology. The phase curve of secondary mode is found to be more smooth compared to a prominent mode of pulsation.

  7. Return of Pulsations in SDSS 0745+4538

    Science.gov (United States)

    Mukadam, Anjum S.; Townsley, D. M.; Szkody, P.; Gänsicke, B. T.; Winget, D. E.; Hermes, J. J.; Howell, Steve B.; Teske, J.; Patterson, Joseph; Kemp, Jonathan; Armstrong, Eve

    2010-11-01

    Nonradial pulsations had ceased in the accreting white dwarf SDSS J074531.92+453829.6 subsequent to its October 2006 outburst. We recently acquired optical high-speed time-series photometry on this cataclysmic variable more than three years after its outburst to find that pulsations have now returned to the primary white dwarf. Moreover, the observed pulsation periods agree with pre-outburst periods within the uncertainties of 1-2 s. This discovery is both remarkable and significant because it indicates that the outburst did not affect the interior stellar structure, which dictates the observed pulsation frequencies. Using this discovery in addition to an HST ultra-violet temperature measurement obtained one year after outburst, we have also been able to constrain the matter accreted during the 2006 outburst.

  8. Atomic diffusion and observations of pulsating A stars

    Science.gov (United States)

    Kurtz, D. W.

    2013-12-01

    Atomic diffusion - important in many contexts in stellar astrophysics and an important thread running through this meeting - is most spectacularly observable in the atmospheres of some A stars. The magnetic Ap stars and the non-magnetic Am stars show directly abundance anomalies caused by gravitational settling and radiative levitation. Over the last decade spectroscopic studies have begun to provide maps of abundance distributions in the magnetic Ap stars in three dimensions. Interestingly, high radial overtone p-mode pulsations in roAp stars have also given three-dimensional views of the stellar atmospheres with studies of rotational and line profile variations of pulsation amplitudes and phases. These detailed looks at the effects of microscopic atmospheric changes in the strongly non-LTE and magnetic upper atmospheric layers of Ap stars provide perhaps the most exciting challenge to atomic diffusion theory in terms of detailed explanation and prediction. Am stars were at one time thought not to pulsate because of gravitational settling of He from the He ii ionization zone that provides the κ-mechanism driving for δ Sct pulsations in A stars. In the last few years we have found with SuperWASP and Kepler observations that many Am stars do pulsate. More than half of all A stars pulsate at Kepler micromagnitude precision, yet there is a subset of A stars that truly do not pulsate at that level. Are these Am stars with the strongest signature of atomic diffusion? Is atomic diffusion the reason for the pulsational stability of these stars? The answers are not yet known.

  9. Disintegration of Bone Cement by Continuous and Pulsating Water Jet

    OpenAIRE

    S. Hloch; Foldyna, J.; Sitek, L. (Libor); M. Zeleňák; Hlaváček, P.; Hvizdoš, P.; Kloc, J.; Monka, P.; Monková, K.; Kozak, D.; Magurová, D.

    2013-01-01

    The paper deals with the study of using continuous water jet and ultrasonic pulsating water jet for bone cement disintegration. Bone-cement Pallacos R+G (manually mixed) was disintegrated ex-vivo. Mechanical properties of the bone cement were determined by nano-indentation. Factors employed in evaluation were pressure (40, 80, 120) MPa and traverse speed for continuous water jet, pressure (8, 10, 12, 14, 16, 20) MPa and orifice type (flat, circular) for ultrasonic pulsating water jet. Depth p...

  10. Ultrasonic pulsations of pressure in a water jet cutting tool

    OpenAIRE

    Říha, Z. (Zdeněk); Foldyna, J.

    2012-01-01

    Water flow in a tool for water jet cleaning and cutting is evaluated in this paper. There are ultrasonic pulsations of high pressure in the given domain. The efficiency of the amplification of high pressure pulsations in the transitional space between larger and smaller pipes is analysed. Three types of transitional spaces are compared in the paper: step change, conical and radius change of pipe diameters.

  11. Observation and modeling of compressional Pi 3 magnetic pulsations

    Science.gov (United States)

    Matsuoka, Hitoshi; Takahashi, K.; Yumoto, K.; Anderson, B. J.; Sibeck, D. G.

    1995-01-01

    Compressional magnetic pulsations with irregular waveforms and periods longer than 150 s (here termed Pi 3) have been studied by using data from Active Magnetospheric Particle Tracer Explorers Charge Composition Explorer (AMPTE/CCE) and GOES 5 and 6 in the dayside magnetosphere and compared with signatures on the ground at low latitudes by using data from Kakioka station (L = 1.25). On the ground, the pulsations appear in the horizontal component. A study of 17 such concurrent events during a 2-month period in 1986 reveals the following pulsation characteristics. (1) The peak-to-peak amplitudes in space (delta B(sub T)) and on the ground (delta H) are comparable and are in the range of 0.5-7 nT. (2) On the ground the pulsations can be seen at all local times, even at midnight, while at geostationary orbit they are observed only on the dayside with a clear amplitude maximum at noon. (3) The pulsations on the ground lag those observed by CCE near local noon, and the lag increases as the local time separation between CCE and the ground station increases. The time lag is 1-2 min longer when the ground station is on the nightside than when it is on the dayside. (4) The time lag between pulsations observed at geostationary orbit and near noon by CCE varies systematically with local time and is about 2 min per 6 hours of local time separation. These observations indicate that some nightside pulsations in the Pi 3 band have dayside origins. The position dependence of the pulsation amplitude can be explained well by changes in the magnetopause current, which are in turn presumably caused by changes in the solar wind dynamic pressure. The time lags observed in space are consistent with signal propagation in the MHD fast mode, but the variation in space-ground time lags with ground station local time must be attributed to another mechanism.

  12. First Kepler results on compact pulsators - II. KIC 010139564, a new pulsating subdwarf B (V361 Hya) star with an additional low-frequency mode

    DEFF Research Database (Denmark)

    Kawaler, Stephen; Reed, M.D.; Quint, A.C.;

    2010-01-01

    We present the discovery of non-radial pulsations in a hot subdwarf B star based on 30.5 d of nearly continuous time series photometry using the Kepler spacecraft. KIC 010139564 is found to be a short-period pulsator of the V361 Hya (EC 14026) class with more than 10 independent pulsation modes...

  13. Thermal quantities of 46Ti

    Science.gov (United States)

    Rahmatinejad, A.; Razavi, R.; Kakavand, T.

    2015-07-01

    Thermodynamic quantities of 46Ti have been calculated in the framework of the BCS model with inclusion of modified nuclear pairing gap (MPBCS) that was proposed in our previous publication. Using modified paring gap results in an S-shaped heat capacity curve at critical temperature with a smooth behavior instead of singular behavior of the same curve in the BCS calculations. In addition the thermal quantities have been extracted within the framework of a canonical ensemble according to the new experimental data on nuclear level densities measured by the Oslo group. Comparison shows a good agreement between our calculations in MPBCS and the extracted quantities in the canonical ensemble framework.

  14. First Kepler results on compact pulsators - III. Subdwarf B stars with V1093 Her and hybrid (DW Lyn) type pulsations

    DEFF Research Database (Denmark)

    Reed, M.D.; Kawaler, Stephen D.; Østensen, Roy H.;

    2010-01-01

    -modes with periods of 2-5 min and in addition, these stars exhibit periodicities between both classes from 15 to 45 min. We detect the coolest and longest-period V1093 Her-type pulsator to date, KIC010670103 (Teff≈ 20 900 K, Pmax≈ 4.5 h) as well as a suspected hybrid pulsator, KIC002697388, which is extremely cool...... (Teff≈ 23 900 K) and for the first time hybrid pulsators which have larger g-mode amplitudes than p-mode ones. All of these pulsators are quite rich with many frequencies and we are able to apply asymptotic relationships to associate periodicities with modes for KIC010670103. Kepler data...

  15. Tuning in on Cepheids: Radial velocity amplitude modulations. A source of systematic uncertainty for Baade-Wesselink distances

    CERN Document Server

    Anderson, Richard I

    2014-01-01

    [Abridged] I report the discovery of modulations in radial velocity (RV) curves of four Galactic classical Cepheids and investigate their impact as a systematic uncertainty for Baade-Wesselink distances. Highly precise Doppler measurements were obtained using the Coralie high-resolution spectrograph since 2011. Particular care was taken to sample all phase points in order to very accurately trace the RV curve during multiple epochs and to search for differences in linear radius variations derived from observations obtained at different epochs. Different timescales are sampled, ranging from cycle-to-cycle to months and years. The unprecedented combination of excellent phase coverage obtained during multiple epochs and high precision enabled the discovery of significant modulation in the RV curves of the short-period s-Cepheids QZ Normae and V335 Puppis, as well as the long-period fundamental mode Cepheids l Carinae and RS Puppis. The modulations manifest as shape and amplitude variations that vary smoothly on ...

  16. PULSATION FREQUENCIES AND MODES OF GIANT EXOPLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Le Bihan, Bastien [Ecole Polytechnique, Palaiseau, France. (France); Burrows, Adam, E-mail: bastien.le-bihan@polytechnique.edu, E-mail: burrows@astro.princeton.edu [Department of Astrophysical Science, Peyton Hall Princeton University, Princeton, NJ 08544 (United States)

    2013-02-10

    We calculate the eigenfrequencies and eigenfunctions of the acoustic oscillations of giant exoplanets and explore the dependence of the characteristic frequency {nu}{sub 0} and the eigenfrequencies on several parameters: the planet mass, the planet radius, the core mass, and the heavy element mass fraction in the envelope. We provide the eigenvalues for degree l up to 8 and radial order n up to 12. For the selected values of l and n, we find that the pulsation eigenfrequencies depend strongly on the planet mass and radius, especially at high frequency. We quantify this dependence through the calculation of the characteristic frequency {nu}{sub 0} which gives us an estimate of the scale of the eigenvalue spectrum at high frequency. For the mass range 0.5 M{sub J} {<=} M{sub P} {<=} 15 M{sub J} , and fixing the planet radius to the Jovian value, we find that {nu}{sub 0} {approx} 164.0 Multiplication-Sign (M{sub P} /M{sub J} ){sup 0.48}{mu}Hz, where M{sub P} is the planet mass and M{sub J} is Jupiter's mass. For the radius range from 0.9 to 2.0 R{sub J} , and fixing the planet's mass to the Jovian value, we find that {nu}{sub 0} {approx} 164.0 Multiplication-Sign (R{sub P} /R{sub J} ){sup -2.09}{mu}Hz, where R{sub P} is the planet radius and R{sub J} is Jupiter's radius. We explore the influence of the presence of a dense core on the pulsation frequencies and on the characteristic frequency of giant exoplanets. We find that the presence of heavy elements in the envelope affects the eigenvalue distribution in ways similar to the presence of a dense core. Additionally, we apply our formalism to Jupiter and Saturn and find results consistent with both the observational data of Gaulme et al. and previous theoretical work.

  17. Intrinsic B-V color for galactic cepheids and some comments on the Sandage-Tammann relationship

    Science.gov (United States)

    Kelsall, T.

    1972-01-01

    Transformations are found for converting the b-y color excesses for Cepheids given by Williams (1966) and Kelsall (1971) into B-V excesses. The combination of these results with the E(B-V)'s determined by Sandage and Tammann (1971) gives precise data for eighty-eight galactic Cepheids. The period-color and period-color-(amplitude defect) relationships, that are germane to the LogP intervals 0.4 to 1.4 and 0.4 to 1.3, respectively, are found.

  18. The VVV Survey reveals classical Cepheids tracing a young and thin stellar disk across the Galaxy's bulge

    CERN Document Server

    Dékány, I; Majaess, D; Zoccali, M; Hajdu, G; Alonso-García, J; Catelan, M; Gieren, W; Borissova, J

    2015-01-01

    Solid insight into the physics of the inner Milky Way is key to understanding our Galaxy's evolution, but extreme dust obscuration has historically hindered efforts to map the area along the Galactic mid-plane. New comprehensive near-infrared time-series photometry from the VVV Survey has revealed 35 classical Cepheids, tracing a previously unobserved component of the inner Galaxy, namely a ubiquitous inner thin disk of young stars along the Galactic mid-plane, traversing across the bulge. The discovered period (age) spread of these classical Cepheids implies a continuous supply of newly formed stars in the central region of the Galaxy over the last 100 million years.

  19. The VVV Survey Reveals Classical Cepheids Tracing a Young and Thin Stellar Disk across the Galaxy’s Bulge

    Science.gov (United States)

    Dékány, I.; Minniti, D.; Majaess, D.; Zoccali, M.; Hajdu, G.; Alonso-García, J.; Catelan, M.; Gieren, W.; Borissova, J.

    2015-10-01

    Solid insight into the physics of the inner Milky Way is key to understanding our Galaxy’s evolution, but extreme dust obscuration has historically hindered efforts to map the area along the Galactic mid-plane. New comprehensive near-infrared time-series photometry from the VVV Survey has revealed 35 classical Cepheids, tracing a previously unobserved component of the inner Galaxy, namely a ubiquitous inner thin disk of young stars along the Galactic mid-plane, traversing across the bulge. The discovered period (age) spread of these classical Cepheids implies a continuous supply of newly formed stars in the central region of the Galaxy over the last 100 million years.

  20. THE VVV SURVEY REVEALS CLASSICAL CEPHEIDS TRACING A YOUNG AND THIN STELLAR DISK ACROSS THE GALAXY’S BULGE

    Energy Technology Data Exchange (ETDEWEB)

    Dékány, I. [Instituto Milenio de Astrofísica, Santiago (Chile); Minniti, D. [Departamento de Física, Facultad de Ciencias Exactas, Universidad Andres Bello, República 220, Santiago (Chile); Majaess, D. [Saint Mary’s University, Halifax, Nova Scotia (Canada); Zoccali, M.; Hajdu, G.; Catelan, M. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Santiago (Chile); Alonso-García, J. [Unidad de Astronomía, Fac. Cs. Básicas, Universidad de Antofagasta, Avda. U. de Antofagasta 02800, Antofagasta (Chile); Gieren, W. [Departamento de Astronomía, Universidad de Concepción, Casilla 160-C, Concepción (Chile); Borissova, J., E-mail: idekany@astro.puc.cl [Instituto de Física y Astronomía, Universidad de Valparaíso, Av. Gran Bretaña 1111, Valparaso (Chile)

    2015-10-20

    Solid insight into the physics of the inner Milky Way is key to understanding our Galaxy’s evolution, but extreme dust obscuration has historically hindered efforts to map the area along the Galactic mid-plane. New comprehensive near-infrared time-series photometry from the VVV Survey has revealed 35 classical Cepheids, tracing a previously unobserved component of the inner Galaxy, namely a ubiquitous inner thin disk of young stars along the Galactic mid-plane, traversing across the bulge. The discovered period (age) spread of these classical Cepheids implies a continuous supply of newly formed stars in the central region of the Galaxy over the last 100 million years.

  1. Galactic abundance gradients from Cepheids. α and heavy elements in the outer disk

    Science.gov (United States)

    Lemasle, B.; François, P.; Genovali, K.; Kovtyukh, V. V.; Bono, G.; Inno, L.; Laney, C. D.; Kaper, L.; Bergemann, M.; Fabrizio, M.; Matsunaga, N.; Pedicelli, S.; Primas, F.; Romaniello, M.

    2013-10-01

    Context. Galactic abundance gradients set strong constraints to chemo-dynamical evolutionary models of the Milky Way. Given the period-luminosity relations that provide accurate distances and the large number of spectral lines, Cepheids are excellent tracers of the present-day abundance gradients. Aims: We want to measure the Galactic abundance gradient of several chemical elements. While the slope of the Cepheid iron gradient did not vary much from the very first studies, the gradients of the other elements are not that well constrained. In this paper we focus on the inner and outer regions of the Galactic thin disk. Methods: We use high-resolution spectra (FEROS, ESPADONS, NARVAL) to measure the abundances of several light (Na, Al), α (Mg, Si, S, Ca), and heavy elements (Y, Zr, La, Ce, Nd, Eu) in a sample of 65 Milky Way Cepheids. Combining these results with accurate distances from period-Wesenheit relations in the near-infrared enables us to determine the abundance gradients in the Milky Way. Results: Our results are in good agreement with previous studies on either Cepheids or other tracers. In particular, we confirm an upward shift of ≈0.2 dex for the Mg abundances, as has recently been reported. We also confirm the existence of a gradient for all the heavy elements studied in the context of a local thermodynamic equilibrium analysis. However, for Y, Nd, and especially La, we find lower abundances for Cepheids in the outer disk than reported in previous studies, leading to steeper gradients. This effect can be explained by the differences in the line lists used by different groups. Conclusions: Our data do not support a flattening of the gradients in the outer disk, in agreement with recent Cepheid studies and chemo-dynamical simulations. This is in contrast to the open cluster observations but remains compatible with a picture where the transition zone between the inner disk and the outer disk would move outward with time. Based on observations obtained

  2. The evolved pulsating CEMP star HD112869

    CERN Document Server

    Začs, L; Grankina, A; Deveikis, V; Kaminskyi, B; Pavlenko, Y; Musaev, F

    2015-01-01

    Radial velocity measurements, $BVR_C$ photometry, and high-resolution spectroscopy in the wavelength region from blue to near infrared are employed in order to clarify the evolutionary status of the carbon-enhanced metal-poor star HD112869 with unique ratio of carbon isotopes in the atmosphere. An LTE abundance analysis was carried out using the method of spectral synthesis and new self consistent 1D atmospheric models. The radial velocity monitoring confirmed semiregular variations with a peak-to-peak amplitude of about 10 km $s^{-1}$ and a dominating period of about 115 days. The light, color and radial velocity variations are typical of the evolved pulsating stars. The atmosphere of HD112869 appears to be less metal-poor than reported before, [Fe/H] = -2.3 $\\pm$0.2 dex. Carbon to oxygen and carbon isotope ratios are found to be extremely high, C/O $\\simeq$ 12.6 and $^{12}C/^{13}C \\gtrsim$ 1500, respectively. The s-process elements yttrium and barium are not enhanced, but neodymium appears to be overabundan...

  3. Fine droplet generation using tunable electrohydrodynamic pulsation

    International Nuclear Information System (INIS)

    High-efficiency generation of fine droplets is significant for many microfluidic chips and sensor applications. To produce fine droplets, nozzles with small diameters are needed, which results in a high cost for nozzles and low efficiency of droplet generation. In this paper, a tunable electrohydrodynamic pulsation method which can generate fine droplets with high frequency and controllable size is presented using low conductivity liquids. The effects of flow rates and voltage parameters with respect to deposition frequency and droplet size are investigated. The influence of these parameters on Taylor cone formation time are also discussed and simple scaling laws are proposed to reveal and guide the droplet generation process. Experimental results show that single cycle deposition frequency decreases with increasing voltage frequency, but is only slightly influenced by the flow rates. The droplet size also decreases with voltage frequency, while large flow rates can make this decline gradual allowing better control. Moreover, the Taylor cone formation time may greatly affect the stability of the deposition frequency when the voltage frequency is larger than 30 Hz. Due to the short cycle time of high voltage frequencies, the hydrodynamic behavior in the emission process may be considerably affected by the increase of volume, which is also related to the flow rates. Tunable micropatterns consisting of fine droplets can be achieved by using this method in combination with motion stages. (paper)

  4. Constraining the neutrino magnetic dipole moment from white dwarf pulsations

    Energy Technology Data Exchange (ETDEWEB)

    Córsico, A.H.; Althaus, L.G. [Grupo de Evolución Estelar y Pulsaciones, Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque s/n, (1900) La Plata (Argentina); Bertolami, M.M. Miller [Instituto de Astrofísica La Plata, CONICET-UNLP, Paseo del Bosque s/n, (1900) La Plata (Argentina); Kepler, S.O. [Departamento de Astronomia, Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, Porto Alegre 91501-970, RS (Brazil); García-Berro, E., E-mail: acorsico@fcaglp.unlp.edu.ar, E-mail: althaus@fcaglp.unlp.edu.ar, E-mail: marcelo@MPA-Garching.MPG.DE, E-mail: kepler@if.ufrgs.br, E-mail: enrique.garcia-berro@upc.edu [Departament de Física Aplicada, Universitat Politècnica de Catalunya, c/Esteve Terrades 5, 08860, Castelldefels (Spain)

    2014-08-01

    Pulsating white dwarf stars can be used as astrophysical laboratories to constrain the properties of weakly interacting particles. Comparing the cooling rates of these stars with the expected values from theoretical models allows us to search for additional sources of cooling due to the emission of axions, neutralinos, or neutrinos with magnetic dipole moment. In this work, we derive an upper bound to the neutrino magnetic dipole moment (μ{sub ν}) using an estimate of the rate of period change of the pulsating DB white dwarf star PG 1351+489. We employ state-of-the-art evolutionary and pulsational codes which allow us to perform a detailed asteroseismological period fit based on fully DB white dwarf evolutionary sequences. Plasmon neutrino emission is the dominant cooling mechanism for this class of hot pulsating white dwarfs, and so it is the main contributor to the rate of change of period with time (Pidot) for the DBV class. Thus, the inclusion of an anomalous neutrino emission through a non-vanishing magnetic dipole moment in these sequences notably influences the evolutionary timescales, and also the expected pulsational properties of the DBV stars. By comparing the theoretical Pidot value with the rate of change of period with time of PG 1351+489, we assess the possible existence of additional cooling by neutrinos with magnetic dipole moment. Our models suggest the existence of some additional cooling in this pulsating DB white dwarf, consistent with a non-zero magnetic dipole moment with an upper limit of μ{sub ν} ∼< 10{sup -11} μ{sub B}. This bound is somewhat less restrictive than, but still compatible with, other limits inferred from the white dwarf luminosity function or from the color-magnitude diagram of the Globular cluster M5. Further improvements of the measurement of the rate of period change of the dominant pulsation mode of PG 1351+489 will be necessary to confirm our bound.

  5. Analysis of the possible Blazhko-effect Cepheid V473 Lyrae

    CERN Document Server

    Molnár, L; Dukes,, R J; Győrffy, Á; Szabó, R

    2013-01-01

    V473 Lyrae is a peculiar Galactic Cepheid, showing strong amplitude modulation that resembles the Blazhko-effect observed in RR Lyrae stars. We collected data spanning several modulation cycles and started a detailed analysis. The first results indicate that the star shows both amplitude and phase modulations with an average period of 1204 days, but both the cycle length and the strength of the modulation are subjected to considerable variations. A possible quintuplet component in the Fourier spectrum and additional period changes were also detected.

  6. VizieR Online Data Catalog: Timing data for the classical Cepheid l Car (Neilson+, 2016)

    Science.gov (United States)

    Neilson, H. R.; Engle, S. G.; Guinan, E. F.; Bisol, A. C.; Butterworth, N.

    2016-08-01

    To measure the period and rate of period change for l Car, we use published photometric data spanning from 1871 to 1990 which we complement with new observations for the year 2012 taken by one of us (Butterworth). See table 1. Six UV observations of l Car were carried out in 2012-2013 with the HST-COS. Also as part of "The Secret Lives of Cepheids" program, an X-ray observation of l Car was carried out with XMM-Newton in 2010 February. See section 4 for further details. (1 data file).

  7. VizieR Online Data Catalog: Pulsation model data for delta Cep and eta Aql (Merand+, 2015)

    Science.gov (United States)

    Merand, A.; Kervella, P.; Breitfelder, J.; Gallenne, A.; Coude du Foresto, V.; ten Brummelaar, T. A.; McAlister, H. A.; Ridgway, S.; Sturmann, L.; Sturmann, J.; Turner, N. H.

    2015-09-01

    FITS files containing the stars' (delta Cep and eta Aql) data and model presented in the paper. Each fits file has 3 HDU: 1- primary HDU: contains no data apart from the header. The header has the parameters of the model (keywords 'HIERARCH PARAM') as well as some other quantities derived from the modeling (keywords 'HIERARCH MODEL'). These quantities are aimed at people who would like to reproduce or compare their results with us. 2- 'DATA' HDU: this contains the data used for the fit. Each line is a scalar measurement described as follow: col1='MJD' (E) modified Julian date of the observations col2='OBS' (A50) description of the data point: the string before ";" defines the type, after ";" is the source. after | are anciliary data: for diam, UDdiam: [wavelengthum, interfbaseline_m] for mag: photometric band for color: photometric band1 - photometric band2 col3='MEAS' (E) the actual measurements. units are km/s for Vpuls or Vrad (which includes the p-factor correction), and mas (milli-arcseconds) for diameters (diam of UDdiam). col4='ERR' (E) the uncertainty on the measurement. col5='MODEL' (E) corresponding value predicted by the model col6='PHASE' (E) pulsation phase computed from the model ranges from 0 to 1. col7='PERIOD' (E) pulsation period computed from the model in days 3- 'MODEL' HDU: a tabulation of the pulsation model, as a function of pulsation phase. col1='PHASE' (E) phase from 0 to 1. col2='Vpuls' (E) pulsation velocity, in km/s. col3='Vrad' (E) radial velocity, in km/s. It is Vpuls/p-factor + Vgamma. col4='diam' (E) Rosseland angular diameter, in milliarcseconds (mas). col5='Teff' (E) effective temperature, in Kelvin. col6='Lum' (E) Luminosity in solar luminosities. col7='logg' (E) surface gravity, in log_10(cm/s2). col8,9,10='diamK xxxm' (E) biased angular diameters measured by an interferometer at baselines xxx (in m), for xxx=[100, 200, 300]. In milliarcseconds col>=11= 'MAG ...' or 'COLOR ...' (E) reddenned magnitudes or colors in various bands

  8. Type II Cepheids in the Milky Way disc. Chemical composition of two new W Vir stars: DD Vel and HQ Car

    CERN Document Server

    Lemasle, B; Bono, G; François, P; Saviane, I; Yegorova, I; Genovali, K; Inno, L; Galazutdinov, G; da Silva, R

    2015-01-01

    A robust classification of Cepheids into their different sub-classes and, in particular, between classical and Type II Cepheids, is necessary to properly calibrate the period-luminosity relations and for populations studies in the Galactic disc. Type II Cepheids are, however, very diverse, and classifications based either on intrinsic (period, light curve) or external parameters (e.g., [Fe/H], |z|) do not provide a unique classification. We want to ascertain the classification of two Cepheids, HQ Car and DD Vel, that are sometimes classified as classical Cepheids and sometimes as Type II Cepheids. To achieve this goal, we examine both their chemical composition and the presence of specific features in their spectra. We find emission features in the H{\\alpha} and in the 5875.64 {\\AA} He I lines that are typical of W Vir stars. The [Na/Fe] (or [Na/Zn]) abundances are typical of thick-disc stars, while BL Her stars are Na-overabundant ([Na/Fe]>+0.5 dex). Finally, the two Cepheids show a possible (HQ Car) or prob...

  9. Photometric Survey to Search for Field sdO Pulsators

    CERN Document Server

    Johnson, Christopher B; Wallace, S; O'Malley, C J; Amaya, H; Biddle, L; Fontaine, G

    2013-01-01

    We present the results of a campaign to search for subdwarf O (sdO) star pulsators among bright field stars. The motivation for this project is the recent discovery by Randall et al. (2011), of four rapidly pulsating sdO stars in the globular cluster Omega Cen, with Teff near 50,000 K, 5.4 -0.1 and similar temperatures and gravities. To date, we have found no detectable pulsations at amplitudes above 0.08% (4 times the mean noise level) in any of the 36 field sdO stars that we observed. The presence of pulsations in Omega Cen sdO stars and their apparent absence in seemingly comparable field sdO stars is perplexing. While very suggestive, the significance of this result is difficult to assess more completely right now due to remaining uncertainties about the temperature width and purity of the Omega Cen instability strip and the existence of any sdO pulsators with weaker amplitudes than the current detection limit in globular clusters.

  10. Effects of inflow pulsation on a turbulent coaxial jet

    International Nuclear Information System (INIS)

    The effects of inflow pulsation on the flow characteristics and mixing properties of turbulent confined coaxial jet flows have been studied. Large eddy simulations were performed at Re = 9000 and the mean velocity ratio of the central to annular jet, Ui/Uo, was 0.6. Pulsation was generated in the inflow jet by varying the flow rates. First, inflow pulsation was applied at frequencies in the range 0.1 < St < 0.9 while other parameters were fixed. The pulsation frequency responses were scrutinized by examining the phase- and time-averaged turbulence statistics. The pulsation frequencies St = 0.180 and 0.327 were found to produce the largest enhancement in mixing and the largest reduction in the reattachment length, respectively. The effects of the phase difference between the two inflow jets at these two optimal frequencies were then investigated. The optimal phase difference conditions for mixing enhancement and the reduction in the reattachment length were obtained when the strength of the outer vortices was high. Further, we found that the strength of the inner vortices was reduced by varying the phase difference, and the reattachment length was minimized, and that if the strength of the inner vortices was increased, mixing was enhanced.

  11. Heartbeat Stars and the Ringing of Tidal Pulsations

    Directory of Open Access Journals (Sweden)

    Hambleton Kelly

    2015-01-01

    Full Text Available With the advent of high precision photometry from satellites such as Kepler and CoRoT, a whole new layer of interesting and astounding astronomical objects has been revealed: heartbeat stars are an example of such objects. Heartbeat stars are eccentric ellipsoidal variables that undergo strong tidal interactions when the stars are almost in contact at the time of closest approach. These interactions deform of the stars and cause a notable light curve variation in the form of a tidal pulse. A subset of these objects (~20% show prominent tidally induced pulsations: pulsations forced by the binary orbit. We now have a fully functional code that models binary star features (using PHOEBE and stellar pulsations simultaneously, enabling a complete and accurate heartbeat star model to be determined. In this paper we show the results of our new code, which uses emcee, a variant of mcmc, to generate a full set of stellar parameters. We further highlight the interesting features of KIC 8164262, including its tidally induced pulsations and resonantly locked pulsations.

  12. On the polarization properties of magnetar giant flare pulsating tails

    CERN Document Server

    Yang, Yuan-Pei

    2015-01-01

    Three giant flares have been detected so far from soft gamma-ray repeaters, each characterized by an initial short hard spike and a pulsating tail. The observed pulsating tails are characterized by a duration of $\\sim100\\,\\rm{s}$, an isotropic energy of $\\sim 10^{44}\\,\\rm{erg}$, and a pulse period of a few seconds. The pulsating tail emission likely originates from the residual energy after the intense energy release during the initial spike, which forms a trapped fireball composed of a photon-pair plasma in a closed field line region of the magnetars. Observationally the spectra of pulsating tails can be fitted by the superposition of a thermal component and a power-law component, with the thermal component dominating the emission in the early and late stages of the pulsating tail observations. In this paper, assuming that the trapped fireball is from a closed field line region in the magnetosphere, we calculate the atmosphere structure of the optically-thick trapped fireball and the polarization properties ...

  13. Finding the Instability Strip for Accreting Pulsating White Dwarfs from HST and Optical Observations

    CERN Document Server

    Szkody, Paula; Gansicke, Boris T; Henden, Arne; Templeton, Matthew; Holtzman, Jon; Montgomery, Michael H; Howell, Steve B; Nitta, Atsuko; Sion, Edward M; Schwartz, Richard D; Dillon, William

    2010-01-01

    Time-resolved low resolution Hubble Space Telescope ultraviolet spectra together with ground-based optical photometry and spectra are used to constrain the temperatures and pulsation properties of six cataclysmic variables containing pulsating white dwarfs. Combining our temperature determinations for the five pulsating white dwarfs that are several years past outburst with past results on six other systems shows that the instability strip for accreting pulsating white dwarfs ranges from 10,500-15,000K, a wider range than evident for ZZ Ceti pulsators. Analysis of the UV/optical pulsation properties reveals some puzzling aspects. While half the systems show high pulsation amplitudes in the UV compared to their optical counterparts, others show UV/optical amplitude ratios that are less than one or no pulsations at either wavelength region.

  14. The VMC Survey - X. Cepheids, RR Lyrae stars and binaries as probes of the Magellanic System's structure

    CERN Document Server

    Moretti, M I; Muraveva, T; Ripepi, V; Marquette, J B; Cioni, M -R L; Marconi, M; Girardi, L; Rubele, S; Tisserand, P; de Grijs, R; Groenewegen, M A T; Guandalini, R; Ivanov, V D; van Loon, J Th

    2013-01-01

    The VMC survey is obtaining multi-epoch photometry in the Ks band of the Magellanic System down to a limiting magnitude of Ks ~ 19.3 for individual epoch data. The observations are spaced in time such as to provide optimal sampling of the light curves for RR Lyrae stars and for Cepheids with periods up to 20-30 days. We present examples of the Ks-band light curves of Classical Cepheids and RR Lyrae stars we are obtaining from the VMC data and outline the strategy we put in place to measure distances and infer the System three-dimensional geometry from the variable stars. For this purpose the near-infrared Period-Luminosity, Period-Wesenheit, and Period-Luminosity-Colour relations of the system RR Lyrae stars and Cepheids are used. We extensively exploit the catalogues of the Magellanic Clouds' variable stars provided by the EROS-2 and OGLE III/IV microlensing surveys. By combining these surveys we present the currently widest-area view of the Large Magellanic Cloud as captured by the galaxy Cepheids, RR Lyrae...

  15. The Cepheid Period-Luminosity Relation at Mid-Infrared Wavelengths: I. First-Epoch LMC Data

    CERN Document Server

    Freedman, Wendy L; Rigby, Jane; Persson, S E; Sturch, Laura

    2008-01-01

    We present the first mid-infrared Period-Luminosity (PL) relations for Large Magellanic Cloud (LMC) Cepheids. Single-epoch observations of 70 Cepheids were extracted from Spitzer IRAC observations at 3.6, 4.5, 5.8 and 8.0 microns, serendipitously obtained during the SAGE (Surveying the Agents of a Galaxy's Evolution) imaging survey of the LMC. All four mid-infrared PL relations have nearly identical slopes over the period range 6 - 88 days, with a small scatter of only +/-0.16 mag independent of period for all four of these wavelengths. We emphasize that differential reddening is not contributing significantly to the observed scatter, given the nearly two orders of magnitude reduced sensitivity of the mid-IR to extinction compared to the optical. Future observations, filling in the light curves for these Cepheids, should noticeably reduce the residual scatter. These attributes alone suggest that mid-infrared PL relations will provide a practical means of significantly improving the accuracy of Cepheid distanc...

  16. Three dimensional maps of the Magellanic Clouds using RR~Lyrae stars and Cepheids - I. The Large Magellanic Cloud

    CERN Document Server

    Haschke, Raoul; Duffau, Sonia

    2012-01-01

    The new data for Cepheids and RR Lyrae stars of the Optical Gravitational Lensing Experiment (OGLE-III) survey allow us to study the three-dimensional distribution of stars corresponding to young (a few tens to a few hundreds of millions of years) and old (typically older than ~9 Gyr) populations of the Large Magellanic Cloud (LMC) traced by these variable stars. We estimate the distance to 16949 RR Lyrae stars by using their photometrically estimated metallicities. Furthermore the periods of 1849 Cepheids are used to determine their distances. Three-dimensional maps are obtained by using individual reddening estimates derived from the intrinsic color of these stars. The resulting median distances of the RR Lyrae stars and Cepheids appear to resolve the long and short distance scale problem for our sample. With median distances of 53.1 \\pm 3.2 kpc for the RR Lyrae stars and 53.9 \\pm 1.8 kpc for the Cepheids, these two distance indicators are in very good agreement with each other in contrast to a number of ea...

  17. Period-luminosity relations for Small Magellanic Cloud Cepheid based on AKARI archival data

    Science.gov (United States)

    Ngeow, Chow-Choong; Citro, Danielle M.; Kanbur, Shashi M.

    2012-02-01

    In this work we matched the AKARI archival data to the Optical Gravitational Lensing Experiment III (OGLE-III) catalogue to derive the mid-infrared period-luminosity (PL) relations for Small Magellanic Cloud (SMC) Cepheids. Mismatched AKARI sources were eliminated using random-phase colours obtained from the full I-band light curves from OGLE-III. It was possible to derive PL relations in the N3 and N4 bands only, although the S7-, S11-, L15- and L24-band data were also tested. Random-phase correction was included when deriving the PL relation in the N3 and N4 bands using the available time of observations from AKARI data. The final adopted PL relations were N3 =-3.370 log P + 16.527 and N4 =-3.402 log P + 16.556. However, these PL relations may be biased due to the small number of Cepheids in the sample.

  18. Period-Luminosity Relations for Small Magellanic Cloud Cepheid Based on AKARI Archival Data

    CERN Document Server

    Ngeow, Chow-Choong; Kanbur, Shashi M

    2011-01-01

    In this work we matched the AKARI archival data to the Optical Gravitational Lensing Experiment-III (OGLE-III) catalog to derive the mid-infrared period luminosity (PL) relations for Small Magellanic Cloud (SMC) Cepheids. Mismatched AKARI sources were eliminated using random-phase colors obtained from the full I-band light curves from OGLE-III. It was possible to derive PL relations in the N3 and N4 bands only, although the S7, S11, L15, and L24 band data were also tested. Random-phase correction was included when deriving the PL relation in the N3 and N4 bands using the available time of observations from AKARI data. The final adopted PL relations were: N3 = -3.370 logP + 16.527 and N4 = -3.402 logP + 16.556. However, these PL relations may be biased due to the small number of Cepheids in the sample.

  19. Bimodal chemical evolution of the Galactic disk and the Barium abundance of Cepheids

    CERN Document Server

    Lepine, Jacques R D; Barros, Douglas A; Junqueira, Thiago C; Scarano, Sergio

    2013-01-01

    In order to understand the Barium abundance distribution in the Galactic disk based on Cepheids, one must first be aware of important effects of the corotation resonance, situated a little beyond the solar orbit. The thin disk of the Galaxy is divided in two regions that are separated by a barrier situated at that radius. Since the gas cannot get across that barrier, the chemical evolution is independent on the two sides of it. The barrier is caused by the opposite directions of flows of gas, on the two sides, in addition to a Cassini-like ring void of HI (caused itself by the flows). A step in the metallicity gradient developed at corotation, due to the difference in the average star formation rate on the two sides, and to this lack of communication between them. In connection with this, a proof that the spiral arms of our Galaxy are long-lived (a few billion years) is the existence of this step. When one studies the abundance gradients by means of stars which span a range of ages, like the Cepheids, one has...

  20. Prediction of gas pulsation of an industrial compressor

    Institute of Scientific and Technical Information of China (English)

    Heuicheol; Kim; Mi-Gyung; Cho; Jaehong; Park; Cheolho; Bai; Jaesool; Shim

    2013-01-01

    The measurement and prediction of gas pulsations are performed along the discharge pipeline of a reciprocating compressor for a refrigerator. A regression based experimental model of the one-dimensional acoustic field is developed. First, the conventional method for gas pulsation measurement and prediction, which separates the incident and reflected wave of acoustic waves traveling in the frequency domain, is discussed. Then, regression based on our proposed simple model, which is able to predict gas pulsation compared to the conventional method, is introduced for the analysis of a reciprocating compressor(The conventional method requires the value of sound speed in the piping line for the reciprocating compressor). A numerical prediction is made for the regression method. Three power spectrum values along the discharge pipeline are used for analysis, and two values are used for verification. Our results are in a good agreement with the conventional method.

  1. An Adaptive Code for Radial Stellar Model Pulsations

    Science.gov (United States)

    Buchler, J. Robert; Kolláth, Zoltán; Marom, Ariel

    1997-09-01

    We describe an implicit 1-D adaptive mesh hydrodynamics code that is specially tailored for radial stellar pulsations. In the Lagrangian limit the code reduces to the well tested Fraley scheme. The code has the useful feature that unwanted, long lasting transients can be avoided by smoothly switching on the adaptive mesh features starting from the Lagrangean code. Thus, a limit cycle pulsation that can readily be computed with the relaxation method of Stellingwerf will converge in a few tens of pulsation cycles when put into the adaptive mesh code. The code has been checked with two shock problems, viz. Noh and Sedov, for which analytical solutions are known, and it has been found to be both accurate and stable. Superior results were obtained through the solution of the total energy (gravitational + kinetic + internal) equation rather than that of the internal energy only.

  2. Outbursts in two new cool pulsating DA white dwarfs

    CERN Document Server

    Bell, Keaton J; Montgomery, M H; Fusillo, N P Gentile; Raddi, R; Gaensicke, B T; Winget, D E; Dennihy, E; Gianninas, A; Tremblay, P -E; Chote, P; Winget, K I

    2016-01-01

    The unprecedented extent of coverage provided by Kepler observations recently revealed outbursts in two hydrogen-atmosphere pulsating white dwarfs (DAVs) that cause hours-long increases in the overall mean flux of up to 14%. We have identified two new outbursting pulsating white dwarfs in K2, bringing the total number of known outbursting white dwarfs to four. EPIC 211629697, with T_eff = 10,780 +/- 140 K and log(g) = 7.94 +/- 0.08, shows outbursts recurring on average every 5.0 d, increasing the overall flux by up to 15%. EPIC 229227292, with T_eff = 11,190 +/- 170 K and log(g) = 8.02 +/- 0.05, has outbursts that recur roughly every 2.4 d with amplitudes up to 9%. We establish that only the coolest pulsating white dwarfs within a small temperature range near the cool, red edge of the DAV instability strip exhibit these outbursts.

  3. Ultra-low-frequency magnetic pulsations in the earth's magnetosphere

    Science.gov (United States)

    Anderson, Brian J.

    1990-01-01

    Spacecraft observations have shown that geomagnetic pulsations originating in magnetospheric processes, in spite of their small amplitude on the ground, have amplitudes in space relative to the local magnetic field of 5-10 percent and occasionally up to about 50 percent. It is noted that by studying geomagnetic pulsations, a detailed comparison can be made between plasma physics theory and observations that are not possible in laboratory experiments. Also geomagnetic pulsations play a role in magnetospheric dynamics and energy transport, and their study forms an integral part of enhancing the knowledge of the magnetosphere. The importance of spacecraft observations are discussed and attention is given to such topics as waves in the magnetosphere, field-line resonances, the quantitative analysis of a dipole field, plasma instabilities, and energy flow.

  4. Finding the First Cosmic Explosions. III. Pair-Pulsational Supernovae

    CERN Document Server

    Whalen, Daniel J; Even, Wesley; Woosley, S E; Heger, Alexander; Stiavelli, Massimo; Fryer, Chris L

    2013-01-01

    Population III supernovae have been the focus of growing attention because of their potential to directly probe the properties of the first stars, particularly the most energetic events that can be seen at the edge of the observable universe. But until now pair-pulsation supernovae, in which explosive thermonuclear burning in massive stars fails to unbind them but can eject their outer layers into space, have been overlooked as cosmic beacons at the earliest redshifts. These shells can later collide and, like Type IIn supernovae, produce superluminous events in the UV at high redshifts that could be detected in the near infrared today. We present numerical simulations of a 110 M$_{\\odot}$ pair-pulsation explosion done with the Los Alamos radiation hydrodynamics code RAGE. We find that collisions between consecutive pair pulsations are visible in the near infrared out to z $\\sim$ 15 - 20 and can probe the earliest stellar populations at cosmic dawn.

  5. On the pulsation modes and masses of RGB OSARGs

    Directory of Open Access Journals (Sweden)

    Saio H.

    2013-03-01

    Full Text Available OSARG (OGLE Small Amplitude Red Giants variables are RGB or AGB stars that show multi-periodic light variations with periods of about 10-100 days. Comparing linear nonadiabatic pulsation periods and period ratios with observed ones, we determined pulsation modes and masses of the RGB OSARG variables in the LMC. We found that pulsations of OSARGs involve radial 1st to 3rd overtones, p4 of l = 1, and p2 of l = 2 modes. The range of mass isfound to be 0.9-1.4M⊙ for RGB OSARGs and their mass-luminosity relation is logL/L⊙ = 0.79 M/M⊙ + 2.2.

  6. Behaviour of Pulsations in Hydrodynamic Models of Massive Stars

    CERN Document Server

    Lovekin, C C

    2014-01-01

    We have calculated the pulsations of massive stars using a nonlinear hydrodynamic code including time-dependent convection. The basic structure models are based on a standard grid published by Meynet et al. (1994). Using the basic structure, we calculated envelope models, which include the outer few percent of the star. These models go down to depths of at least 2 million K. These models, which range from 40 to 85 solar masses, show a range of pulsation behaviours. We find models with very long period pulsations ( $>$ 100 d), resulting in high amplitude changes in the surface properties. We also find a few models that show outburst-like behaviour. The details of this behaviour are discussed, including calculations of the resulting wind mass-loss rates.

  7. Outbursts in Two New Cool Pulsating DA White Dwarfs

    Science.gov (United States)

    Bell, Keaton J.; Hermes, J. J.; Montgomery, M. H.; Gentile Fusillo, N. P.; Raddi, R.; Gänsicke, B. T.; Winget, D. E.; Dennihy, E.; Gianninas, A.; Tremblay, P.-E.; Chote, P.; Winget, K. I.

    2016-10-01

    The unprecedented extent of coverage provided by Kepler observations recently revealed outbursts in two hydrogen-atmosphere pulsating white dwarfs (DAVs) that cause hours-long increases in the overall mean flux of up to 14%. We have identified two new outbursting pulsating white dwarfs in K2, bringing the total number of known outbursting white dwarfs to four. EPIC 211629697, with {T}{eff} = 10,780 ± 140 K and {log} g = 7.94 ± 0.08, shows outbursts recurring on average every 5.0 days, increasing the overall flux by up to 15%. EPIC 229227292, with {T}{eff} = 11,190 ± 170 K and {log} g = 8.02 ± 0.05, has outbursts that recur roughly every 2.4 days with amplitudes up to 9%. We establish that only the coolest pulsating white dwarfs within a small temperature range near the cool, red edge of the DAV instability strip exhibit these outbursts.

  8. THREE-DIMENSIONAL MAPS OF THE MAGELLANIC CLOUDS USING RR LYRAE STARS AND CEPHEIDS. II. THE SMALL MAGELLANIC CLOUD

    International Nuclear Information System (INIS)

    We use data on variable stars from the Optical Gravitational Lensing Experiment survey to determine the three-dimensional structure of the Small Magellanic Cloud (SMC). Deriving individual distances to RR Lyrae stars and Cepheids, we investigate the distribution of these tracers of the old and young populations in the SMC. Photometrically estimated metallicities are used to determine the distances to 1494 RR Lyrae stars, which have typical ages greater than 9 Gyr. For 2522 Cepheids, with ages of a few tens to a few hundred Myr, distances are calculated using their period-luminosity relation. Individual reddening estimates from the intrinsic color of each star are used to obtain high precision three-dimensional maps. The distances of RR Lyrae stars and Cepheids are in very good agreement with each other. The median distance of the RR Lyrae stars is found to be 61.5 ± 3.4 kpc. For the Cepheids, a median distance of 63.1 ± 3.0 kpc is obtained. Both populations show an extended scale height, with 2.0 ± 0.4 kpc for the RR Lyrae stars and 2.7 ± 0.3 kpc for the Cepheids. This confirms the large depth of the SMC suggested by a number of earlier studies. The young population is very differently oriented than the old stars. While we find an inclination angle of 7° ± 15° and a position angle of 83° ± 21° for the RR Lyrae stars, for the Cepheids an inclination of 74° ± 9° and a position angle of 66° ± 15° is obtained. The RR Lyrae stars show a fairly homogeneous distribution, while the Cepheids roughly follow the distribution of the bar, with their northeastern part being closer to us than the southwestern part of the bar. Interactions between the SMC, Large Magellanic Cloud, and Milky Way are presumably responsible for the tilted, elongated structure of the young population of the SMC.

  9. Influence of Cylinder Bore Volume on Pressure Pulsations in a Hermetic Reciprocating Compressor

    OpenAIRE

    Novak, Keith Adam

    2014-01-01

    Suction pressure pulsations created when the suction valve opens are caused by unsteady mass flow through the valve exciting acoustic resonances in the suction plenum. These pressure pulsations influence valve dynamics, compressor performance and compressor noise. This paper will show the importance of including the cylinder bore volume in the flow path analysis in order to accurately calculate pressure pulsations. Pressure pulsations will be calculated using Finite Element Method (FEM) calcu...

  10. Generation of traveling atmospheric disturbances during pulsating geomagnetic storms

    Science.gov (United States)

    Gardner, L. C.; Schunk, R. W.

    2010-08-01

    Traveling atmospheric disturbances (TADs) are effective in transporting momentum and energy deposited at high latitudes to the midlatitude and low-latitude regions of the thermosphere. They also act to transport momentum and energy from the lower thermosphere into the upper thermosphere. Previously, model studies have been conducted to determine the characteristics of isolated, single-pulse TADs, but the generation of multiple TADs excited during pulsating storms have not been considered before. Here a high-resolution global thermosphere-ionosphere model was used to study the basic characteristics of multiple TADs excited during pulsating storms, including idealized weak and strong pulsating storms, and an approximation of the 4 May 1998 pulsating storm. For all three pulsating storm simulations, multiple TADs that propagated away from the auroral oval toward both the poles and the equator at all longitudes, with the maximum amplitudes between midnight and dawn, were excited. The TAD amplitudes were at maximum near the poles and diminished toward the equator and were larger on the nightside than on the dayside. The TADs propagated at a slightly upward angle to the horizontal, with the result that the lower boundary of the TADs increased with decreasing latitude. The TADs crossed the equator and propagated to midlatitudes in the opposite hemisphere, where wave interference occurred for the strong pulsating storm cases. The TAD wavelengths vary from 2500 to 3000 km and the phase speeds vary from 800 to 1000 m/s. The maximum TAD perturbations are 20% for the mass density, 14% for the neutral temperature, and 100 m/s for the winds.

  11. Connections between Quasi-periodicity and Modulation in Pulsating Stars

    CERN Document Server

    Benkő, J M

    2013-01-01

    The observations of the photometric space telescopes CoRoT and Kepler show numerous Blazhko RR Lyrae stars which have non-repetitive modulation cycles. The phenomenon can be explained by multi-periodic, stochastic or chaotic processes. From a mathematical point of view, almost periodic functions describe all of them. We assumed band-limited almost periodic functions either for the light curves of the main pulsation or for the modulation functions. The resulting light curves can generally be described analytically and it can also be examined by numerical simulations. This presentation is a part of our systematic study on the modulation of pulsating stars (Benko et al. 2009, 2011, 2012).

  12. Statistical characteristics of temperature pulsations within post-burnout region

    International Nuclear Information System (INIS)

    The experimental results of studies of statistical characteristics of temperature pulsations in a two-phase flow after dryout in post-burnout region are reported. The following statistical characteristics were investigated: intensity, probability distribution density, auto-correlation function and spectral density. Flow temperature pulsations were measured with microthermocouples. The tube was 10 mm in inner diameter; the pressure used was 137.3 bar for mass velocities of 350,000 and 700 kg/m2s. The maximum of relative flow enthalpy in the experiments did not exceed ΔH/r = 2. (U.S.)

  13. Flame fronts in Supernovae Ia and their pulsational stability

    CERN Document Server

    Glazyrin, S I; Dolgov, A D

    2013-01-01

    The structure of the deflagration burning front in type Ia supernovae is considered. The parameters of the flame are obtained: its normal velocity and thickness. The results are in good agreement with previous work of different authors. After that the question of pulsational instability of the flame subject to plane perturbations is considered. The flame can be unstable if hydrodynamics can be ignored, e.g. in solid-body propellants. However, with account of hydrodynamics we find that the flame in type Ia supernovae is pulsationally stable with realistic parameters of reactions and thermal conduction.

  14. Transformerless photovoltaic inverters with leakage current and pulsating power elimination

    DEFF Research Database (Denmark)

    Tang, Yi; Yao, Wenli; Wang, H.;

    2015-01-01

    This paper presents a transformerless inverter topology, which is capable of simultaneously solving leakage current and pulsating power issues in grid-connected photovoltaic (PV) systems. Without adding any additional components to the system, the leakage current caused by the PV...... that is inherent in single-phase PV systems. By properly injecting CM voltages to the output filter capacitors, the pulsating power can be decoupled from the dc-link. Therefore, it is possible to use long lifetime film capacitors instead of electrolytic capacitors to improve the reliability of the PV system...

  15. Cycles of self-pulsations in a photonic integrated circuit.

    Science.gov (United States)

    Karsaklian Dal Bosco, Andreas; Kanno, Kazutaka; Uchida, Atsushi; Sciamanna, Marc; Harayama, Takahisa; Yoshimura, Kazuyuki

    2015-12-01

    We report experimentally on the bifurcation cascade leading to the appearance of self-pulsation in a photonic integrated circuit in which a laser diode is subjected to delayed optical feedback. We study the evolution of the self-pulsing frequency with the increase of both the feedback strength and the injection current. Experimental observations show good qualitative accordance with numerical results carried out with the Lang-Kobayashi rate equation model. We explain the mechanism underlying the self-pulsations by a phenomenon of beating between successive pairs of external cavity modes and antimodes.

  16. Latitude distribution of nonradial pulsations in rapidly rotating B stars

    Science.gov (United States)

    Jankov, S.; Mathias, P.; Domiciano de Souza, A., Jr.; Uytterhoeven, K.; Aerts, C.

    2004-05-01

    We present a method for the analysis of latitude distribution associated with temperature and/or velocity perturbations of the stellar surface due to non-radial pulsation (NRP) modes in rapidly rotating B stars. The technique is applied together with Fourier Doppler Imaging (FDI) to high resolution and high signal-to-noise ratio spectroscopic observations of ɛ Per. The main advantage of this approach is that it decomposed complex multi-periodic line profile variations into single components, allowing the detailed analysis of each mode seperately. We study the 10.6-d-1 frequency that is particularly important for modal analysis of non-radial pulsations in the star.

  17. Interactions of adjacent pulsating, erupting and creeping solitons

    Institute of Scientific and Technical Information of China (English)

    Song Li-Jun; Li Lu; Zhou Guo-Sheng

    2007-01-01

    This paper investigates the adjacent interactions of three novel solitons for the quintic complex Ginzburg-Landau equation, which are plain pulsating, erupting and creeping solitons. It is found that different performances are presented for different solitons due to isolated regions of the parameter space where they exist. For example, plain pulsating and erupting solitons exhibit mutual annihilation during collisions with the decrease of total energy, but for creeping soliton,the two adjacent pulses present soliton fusion without any loss of energy. Otherwise, the method for restraining the interactions is also found and it can suppress interacions between these two adjacent pulses effectively.

  18. Search for Optical Pulsations in PSR J0337+1715

    CERN Document Server

    Strader, M J; Meeker, S R; Szypryt, P; Walter, A B; van Eyken, J C; Ulbricht, G; Stoughton, C; Bumble, B; Kaplan, D L; Mazin, B A

    2016-01-01

    We report on a search for optical pulsations from PSR J0337+1715 at its observed radio pulse period. PSR J0337+1715 is a millisecond pulsar (2.7 ms spin period) in a triple hierarchical system with two white dwarfs, and has a known optical counterpart with g-band magnitude 18. The observations were done with the Array Camera for Optical to Near-IR Spectrophotometry (ARCONS) at the 200" Hale telescope at Palomar Observatory. No significant pulsations were found in the range 4000-11000 angstroms, and we can limit pulsed emission in g-band to be fainter than 25 mag.

  19. X-ray Pulsations in the Supersoft X-ray Binary CAL 83

    OpenAIRE

    Schmidtke, P. C.; Cowley, A. P.

    2005-01-01

    X-ray data reveal that the supersoft X-ray binary CAL 83 exhibits 38.4 minute pulsations at some epochs. These X-ray variations are similar to those found in some novae and are likely to be caused by nonradial pulsations the white dwarf. This is the first detection of pulsations in a classical supersoft X-ray binary.

  20. Recognizing Prefixes in Scientific Quantities

    Science.gov (United States)

    Sokolowski, Andrzej

    2015-09-01

    Although recognizing prefixes in physical quantities is inherent for practitioners, it might not be inherent for students, who do not use prefixes in their everyday life experiences. This deficiency surfaces in AP Physics exams. For example, readers of an AP Physics exam reported "a common mistake of incorrectly converting nanometers to meters." Similar students' mistakes were reported also by AP Chemistry readers "as in previous years, students still had difficulty converting kJ to J." While traditional teaching focuses on memorizing the symbols of prefixes, little attention is given to helping learners recognize a prefix in a given quantity. I noticed in my teaching practice that by making the processes of identifying prefixes more explicit, students make fewer mistakes on unit conversion. Thus, this paper presents an outline of a lesson that focuses on prefix recognition. It is designed for a first-year college physics class; however, its key points can be addressed to any group of physics students.

  1. Radial velocities of southern stars obtained with the photoelectric scanner Coravel. VII. Radial velocity variations of eleven Cepheids in the Large and Small Magellanic clouds

    International Nuclear Information System (INIS)

    We present a second list of systematic radial-velocity measurements of Magellanic-Cloud Cepheids. For five Cepheids in the Large Magellanic Cloud and six in the Small, we give 615 radial-velocity measurements, covering their complete periods. The B magnitudes range from 12.5 to 15.0, and the periods from 42.7 to 134.7 days. All measurements were made with the Coravel photoelectric scanner attached to the Cassegrain focus of the 1.54 m Danish telescope at La Silla, ESO, in Chile, from January 1981 to November 1987. The number of observations for each star varies from 40 to 92. Among the Cepheids, we have identified three long-period spectroscopic binaries. For the remaining Cepheids, radial velocity versus phase diagrams have been fitted by an analytic relation, and the stellar radius variation has been derived by integration of this relation over the whole period

  2. Architecture from quantity to quality

    OpenAIRE

    Luca Gibello

    2015-01-01

    Having surpassed the problem of quantity, it is necessary to now address the problem of widespread quality where we have ensured, that all land surface areas be defined by an architecture project, or rather in a holistic, integrated and multidisciplinary approach. The objective then, is know how to intervene in the scope of transformation, revitalization, reconversion and reuse in urban design. Architecture must know the ‘catalogs’ that provide best practice for design processes and products,...

  3. Quantity discrimination tests with macaques

    OpenAIRE

    sprotocols

    2015-01-01

    Authors: Vanessa Schmitt & Julia Fischer ### Abstract Here we describe the methods used for a two-choice quantity discrimination task, including different control conditions that test for changes in associative strength of the stimuli as well as potential experimenter bias. The experiments revealed that the choices of the monkeys were mainly driven by the fact whether or not they obtained the choice stimuli as food rewards. They did significantly better when tested with inedible i...

  4. Quantities used in radiological protection

    International Nuclear Information System (INIS)

    The application of ICRP recommendations requires knowledge of a variety of concepts and magnitudes. Many of them are employed in other fields of science and precision in its definition reflects this wide application. In this regard, information on quantities and basic units of radiation, which exists in numerous publications, are subjects of great interest. The characteristics and radiation effects are studied by physicists, biologists and chemists mainly. However, there are basics that must be known and to be recognized by general practitioners and specialists from all branches of medicine. The information on quantities and units are used only in radiation protection, have been obtained from the reports listed on the attached bibliography. Such quantities and units contain weighting factors used to provide for different types of radiation and energies that affect the body and thus take into account the relative radio-sensitivity of different tissues. Additionally, they have added a series of data for a better understanding of the units: for example, multiples and sub-multiples, and some examples of converting the units used in radiation protection. (author)

  5. First Kepler results on compact pulsators VI. Targets in the final half of the survey phase

    DEFF Research Database (Denmark)

    H. Østensen, R.; Silvotti, R.; Charpinet, S.;

    2011-01-01

    We present results from the final six months of a survey to search for pulsations in white dwarfs and hot subdwarf stars with the Kepler spacecraft. Spectroscopic observations are used to separate the objects into accurate classes, and we explore the physical parameters of the subdwarf B (sd....... No V361 Hya type of short-period pulsating sdB stars were found in this half, leaving us with a total of one single multiperiodic V361 Hya and 13 V1093 Her pulsators for the full survey. Except for the sdB pulsators, no other clearly pulsating hot subdwarfs or white dwarfs were found, although a few...

  6. Pulsating Water Jet - A Tool for the Future?

    OpenAIRE

    Foldyna, J.

    2013-01-01

    Phenomenon arising during the impact of a droplet on the solid surface and its utilization to enhance effects of water jetting is described in the paper. Some examples of superior performance of pulsating water jets over the continuous ones are presented.

  7. Copper and Copper Alloys Disintegration Using Pulsating Water Jet

    OpenAIRE

    Lehocká, D.; Klich, J. (Jiří); Foldyna, J.; S. Hloch; M. Zeleňák; Cárach, J.

    2015-01-01

    Description of the surface topography of copper and coppeer alloys - brass and bronze is the object of investigation. The material was disintegrated using multiple transition of pulsating water jet with changing speed of feed. It is assumed that this ew way of metal eroding can be used in the automotive and engineering industries in the future.

  8. M dwarf search for pulsations within Kepler GO program

    CERN Document Server

    Rodríguez-López, C; MacDonald, J; Amado, P J; Carosso, A

    2014-01-01

    We present the analysis of four M dwarf stars -plus one M giant that seeped past our selection criteria- observed in Cycle 3 of Kepler Guest Observer program (GO3) in a search for intrinsic pulsations. Stellar oscillations in M dwarfs were theoretically predicted by Rodr\\'iguez-L\\'opez et al. (2012) to be in the range ~20-40 min and ~4-8 h, depending on the age and the excitation mechanism. We requested Kepler short cadence observations to have an adequate sampling of the oscillations. The targets were chosen on the basis of detectable rotation in the initial Kepler results, biasing towards youth.The analysis reveals no oscillations attributable to pulsations at a detection limit of several parts per million, showing that either the driving mechanisms are not efficient in developing the oscillations to observable amplitudes, or that if pulsations are driven, the amplitudes are very low. The size of the sample, and the possibility that the instability strip is not pure, allowing the coexistence of pulsators an...

  9. EXOTIME: searching for planets around pulsating subdwarf B stars

    CERN Document Server

    Schuh, Sonja; Lutz, Ronny; Loeptien, Bjoern; Green, Elizabeth M; Ostensen, Roy H; Leccia, Silvio; Kim, Seung-Lee; Fontaine, Gilles; Charpinet, Stephane; Francoeur, Myriam; Randall, Suzanna; Rodriguez-Lopez, Cristina; van Grootel, Valerie; Odell, Andrew P; Paparo, Margit; Bognar, Zsofia; Papics, Peter; Nagel, Thorsten; Beeck, Benjamin; Hundertmark, Markus; Stahn, Thorsten; Dreizler, Stefan; Hessman, Frederic V; Dall'Ora, Massimo; Mancini, Dario; Cortecchia, Fausto; Benatti, Serena; Claudi, Riccardo; Janulis, Rimvydas; 10.1007/s10509-010-0356-4

    2010-01-01

    In 2007, a companion with planetary mass was found around the pulsating subdwarf B star V391 Pegasi with the timing method, indicating that a previously undiscovered population of substellar companions to apparently single subdwarf B stars might exist. Following this serendipitous discovery, the EXOTIME (http://www.na.astro.it/~silvotti/exotime/) monitoring program has been set up to follow the pulsations of a number of selected rapidly pulsating subdwarf B stars on time-scales of several years with two immediate observational goals: 1) determine Pdot of the pulsational periods P 2) search for signatures of substellar companions in O-C residuals due to periodic light travel time variations, which would be tracking the central star's companion-induced wobble around the center of mass. These sets of data should therefore at the same time: on the one hand be useful to provide extra constraints for classical asteroseismological exercises from the Pdot (comparison with "local" evolutionary models), and on the othe...

  10. A statistical method for draft tube pressure pulsation analysis

    Science.gov (United States)

    Doerfler, P. K.; Ruchonnet, N.

    2012-11-01

    Draft tube pressure pulsation (DTPP) in Francis turbines is composed of various components originating from different physical phenomena. These components may be separated because they differ by their spatial relationships and by their propagation mechanism. The first step for such an analysis was to distinguish between so-called synchronous and asynchronous pulsations; only approximately periodic phenomena could be described in this manner. However, less regular pulsations are always present, and these become important when turbines have to operate in the far off-design range, in particular at very low load. The statistical method described here permits to separate the stochastic (random) component from the two traditional 'regular' components. It works in connection with the standard technique of model testing with several pressure signals measured in draft tube cone. The difference between the individual signals and the averaged pressure signal, together with the coherence between the individual pressure signals is used for analysis. An example reveals that a generalized, non-periodic version of the asynchronous pulsation is important at low load.

  11. Articulated pipes conveying fluid pulsating with high frequency

    DEFF Research Database (Denmark)

    Jensen, Jakob Søndergaard

    1999-01-01

    Stability and nonlinear dynamics of two articulated pipes conveying fluid with a high-frequency pulsating component is investigated. The non-autonomous model equations are converted into autonomous equations by approximating the fast excitation terms with slowly varying terms. The downward hanging...

  12. Pressure pulsations in reciprocating pump piping systems Part 1: Modelling

    CERN Document Server

    Shu, Jian-Jun; Edge, Kevin A

    2014-01-01

    A distributed parameter model of pipeline transmission line behaviour is presented, based on a Galerkin method incorporating frequency-dependent friction. This is readily interfaced to an existing model of the pumping dynamics of a plunger pump to allow time-domain simulations of pipeline pressure pulsations in both suction and delivery lines. A new model for the pump inlet manifold is also proposed.

  13. ON THE POLARIZATION PROPERTIES OF MAGNETAR GIANT FLARE PULSATING TAILS

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yuan-Pei [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China); Zhang, Bing, E-mail: yypspore@gmail.com, E-mail: zhang@physics.unlv.edu [Department of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154 (United States)

    2015-12-10

    Three giant flares have been detected so far from soft gamma-ray repeaters, each characterized by an initial short hard spike and a pulsating tail. The observed pulsating tails are characterized by a duration of ∼100 s, an isotropic energy of ∼10{sup 44} erg, and a pulse period of a few seconds. The pulsating tail emission likely originates from the residual energy after the intense energy release during the initial spike, which forms a trapped fireball composed of a photon-pair plasma in a closed-field-line region of the magnetars. Observationally the spectra of pulsating tails can be fitted by the superposition of a thermal component and a power-law component, with the thermal component dominating the emission in the early and late stages of the pulsating-tail observations. In this paper, assuming that the trapped fireball is from a closed-field-line region in the magnetosphere, we calculate the atmospheric structure of the optically thick trapped fireball and the polarization properties of the trapped fireball. By properly treating the photon propagation in a hot, highly magnetized, electron–positron pair plasma, we tally photons in two modes (O mode and E mode) at a certain observational angle through Monte Carlo simulations. Our results suggest that the polarization degree depends on the viewing angle with respect to the magnetic axis of the magnetar, and can be as high as Π ≃ 30% in the 1–30 keV band, and Π ≃ 10% in the 30–100 keV band, if the line of sight is perpendicular to the magnetic axis.

  14. How necessary are the new quantities

    International Nuclear Information System (INIS)

    The necessity of the ICRU operational quantities is discussed from the point of view of practical, opertional radiation protection, on the basis of ICRU report 43. It is clear that, although the new quantities have some advantages over previous systems of operational quantities, there are some disadvantages as well. The decision to adopt these quantities is, therefore, not clear cut. (orig.)

  15. VizieR Online Data Catalog: AKARI observations of SMC Cepheids (Ngeow+, 2012)

    Science.gov (United States)

    Ngeow, C.-C.; Citro, D. M.; Kanbur, S. M.

    2012-07-01

    The AKARI data used in this work is based on the SMC bright point source catalogue presented in Ita et al. (2010, Cat. J/PASJ/62/273). Photometry in 3.2um (N3, 12899 sources), 4.1um (N4, 9748 sources), 7um (S7, 1838 sources), 11um (S11, 1045 sources), 15um (L15, 479 sources) and 24um (L24, 356 sources) bands provided from the AKARI catalogue. This catalogue was matched to the Optical Gravitational Lensing Experiment III (OGLE-III) SMC fundamental mode (FU) Cepheid catalogue from Soszynski et al. (2010, Cat. J/AcA/60/17). (1 data file).

  16. Cepheids and other variable stars and the distance to the Galactic Centre

    Science.gov (United States)

    Matsunaga, Noriyuki

    2013-02-01

    We review and discuss results of our survey of variable stars towards the Galactic Centre and their distances. In our near-infrared monitoring survey using IRSF/SIRIUS, we detected a number of Miras and Cepheids (both classical and type II) within 20 arcmin of the Galactic Centre. These distance indicators yield a distance to the Galactic Centre of between 7.5 and 8.5 kpc. A new calibration of the red clump also leads to a distance of ~ 8 kpc. For these indicators, which are luminosity-based, a large uncertainty resides in the correction for the foreground extinction, which depends on the reddening law. Nevertheless, our estimates are consistent with previous estimates based the kinematics of stars near the Galactic Centre, and this supports the reddening law we use.

  17. Determination of Cepheid parameters by light-curve template-fitting

    CERN Document Server

    Tanvir, N R; Watkins, A; Kanbur, S M; Berdnikov, L N; Ngeow, C C

    2005-01-01

    Determining the parameters (periods, mean magnitudes etc.) of periodic variable stars is a frequently met problem in astronomy. Here we describe techniques to characterise the light-curves of regular variables by applying principal component analysis (PCA) to a training set of high quality data, and to fit the resulting light-curve templates to sparse and noisy photometry. The PCA approach allows us to efficiently represent the multi-band light-curve shapes of each variable, and hence quantitatively describe the average behaviour of the sample as a smoothly varying function of period, and also the range of variation around this average. In this paper we focus particularly on the utility of such methods for analysing HST Cepheid photometry, and present simulations which illustrate the advantages of our PCA template-fitting approach. These are: accurate parameter determination, including light-curve shape information; simultaneous fitting to multiple passbands; quantitative error analysis; objective rejection o...

  18. First Kepler results on compact pulsators - V. Slowly pulsating subdwarf B stars in short-period binaries

    DEFF Research Database (Denmark)

    Kawaler, Stephen D.; Reed, Michael D.; Østensen, Roy H.;

    2010-01-01

    of sdB stars with a close M-dwarf companion with orbital periods of less than half a day. Because the orbital period is so short, the stars should be in synchronous rotation, and if so, the rotation period should imprint itself on the multiplet structure of the pulsations. However, we do not find clear...

  19. Effects of self-pulsation on the spray characteristics of gas-liquid swirl coaxial injector

    Science.gov (United States)

    Kang, Zhongtao; Li, Qinglian; Cheng, Peng; Zhang, Xinqiao; Wang, Zhen-guo

    2016-10-01

    To understand the influence of self-pulsation on the spray characteristics of gas-liquid swirl coaxial injector, a back-lighting photography technique has been employed to capture the instantaneous self-pulsated spray and stable spray images with a high speed camera. The diameter and velocity of the droplets in the spray have been characterized with a Dantec Phase Doppler Anemometry (PDA) system. The effects of self-pulsation on the spray pattern, primary breakup, spray angle, diameter and velocity distribution and mass flow rate distribution are analyzed and discussed. The results show that the spray morphology is greatly influenced by self-pulsation. The stable spray has a cone shape, while the self-pulsated spray looks like a Christmas tree. The main difference of these two sprays is the primary breakup. The liquid film of stable spray keeps stable while that of self-pulsated spray oscillates periodically. The film width of self-pulsated spray varies in a large range with 'neck' and 'shoulder' features existing. The liquid film of self-pulsated spray breaks up at the second neck, and then the second shoulder begins to breakup into ligaments. The self-pulsated spray produces droplet clusters periodically, varies horizontal spray width and mass flux periodically. From the point of spatial distribution, self-pulsation is good for the spray, it uniformizes the mass flux along radius and increases the spray angle. However, when self-pulsation occurs, the SMD distribution varies from an inverted V shape to a hollow cone shape, and SMD increases at all the measuring points. Namely, from the point of atomization performance, self-pulsation has negative effects even when the breakup length is smaller. The effects of self-pulsation on the diameter and velocity distributions of the spray are mainly in the center part of the spray. The periphery of stable and self-pulsated spray has similar diameter and velocity distribution.

  20. BINARY CEPHEIDS: SEPARATIONS AND MASS RATIOS IN 5 M {sub ☉} BINARIES

    Energy Technology Data Exchange (ETDEWEB)

    Evans, Nancy Remage; Karovska, Margarita; Tingle, Evan [Smithsonian Astrophysical Observatory, MS 4, 60 Garden Street, Cambridge, MA 02138 (United States); Bond, Howard E. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Schaefer, Gail H. [The CHARA Array, Georgia State University, P.O. Box 3965, Atlanta, GA 30302-3965 (United States); Mason, Brian D., E-mail: nevans@cfa.harvard.edu, E-mail: heb11@psu.edu, E-mail: schaefer@chara-array.org [US Naval Observatory, 3450 Massachusetts Avenue, NW, Washington, DC 20392-5420 (United States)

    2013-10-01

    Deriving the distribution of binary parameters for a particular class of stars over the full range of orbital separations usually requires the combination of results from many different observing techniques (radial velocities, interferometry, astrometry, photometry, direct imaging), each with selection biases. However, Cepheids—cool, evolved stars of ∼5 M {sub ☉}—are a special case because ultraviolet (UV) spectra will immediately reveal any companion star hotter than early type A, regardless of the orbital separation. We have used International Ultraviolet Explorer UV spectra of a complete sample of all 76 Cepheids brighter than V = 8 to create a list of all 18 Cepheids with companions more massive than 2.0 M {sub ☉}. Orbital periods of many of these binaries are available from radial-velocity studies, or can be estimated for longer-period systems from detected velocity variability. In an imaging survey with the Hubble Space Telescope Wide Field Camera 3, we resolved three of the companions (those of η Aql, S Nor, and V659 Cen), allowing us to make estimates of the periods out to the long-period end of the distribution. Combining these separations with orbital data in the literature, we derive an unbiased distribution of binary separations, orbital periods, and mass ratios. The distribution of orbital periods shows that the 5 M {sub ☉} binaries have systematically shorter periods than do 1 M {sub ☉} stars. Our data also suggest that the distribution of mass ratios depends on both binary separation and system multiplicity. The distribution of mass ratios as a function of orbital separation, however, does not depend on whether a system is a binary or a triple.

  1. Modern Observations of Hubble's First-discovered Cepheid in M31

    Science.gov (United States)

    Templeton, M.; Henden, A.; Goff, W.; Smith, S.; Sabo, R.; Walker, G.; Buchheim, R.; Belcheva, G.; Crawford, T.; Cook, M.; Dvorak, S.; Harris, B.

    2011-12-01

    We present a modern ephemeris and modern light curve of the first-discovered Cepheid variable in M31, Edwin Hubble's M31-V1. Observers of the American Association of Variable Star Observers (AAVSO) undertook these observations during the latter half of 2010. The observations were in support of an outreach program by the Space Telescope Science Institute's Hubble Heritage project, but the resulting data are the first concentrated observations of M31-V1 made in modern times. AAVSO observers obtained 214 V-band, Rc-band, and unfiltered observations from which a current ephemeris was derived. The ephemeris derived from these observations is JDMax = 2,455,430.5( ± 0.5) + 31.4( ± 0.1)E. The period derived from the 2010 data is in agreement with the historic values of the period, but the single season of data precludes a more precise determination of the period or measurement of the period change using these data alone. However, using an ephemeris based upon the period derived by Baade and Swope, we are able to fit all of the observed data acceptably well. Continued observations in the modern era will be very valuable in linking these modern data with data from the 1920s-1930s and 1950s and will enable us to measure period change in this historic Cepheid. In particular, we strongly encourage intensive observations of this star around predicted times of maximum to constrain the date of maximum to better than 0.5 days.

  2. Optical Identification of Cepheids in 19 Host Galaxies of Type Ia Supernovae and NGC 4258 with the Hubble Space Telescope

    CERN Document Server

    Hoffmann, Samantha L; Riess, Adam G; Yuan, Wenlong; Casertano, Stefano; Filippenko, Alexei V; Tucker, Brad E; Chornock, Ryan; Silverman, Jeffrey M; Welch, Douglas L; Goobar, Ariel; Amanullah, Rahman

    2016-01-01

    We present results of an optical search for Cepheid variable stars using the Hubble Space Telescope (HST) in 19 hosts of Type Ia supernovae (SNe Ia) and the maser-host galaxy NGC 4258, conducted as part of the SH0ES project (Supernovae and H0 for the Equation of State of dark energy). The targets include 9 newly imaged SN Ia hosts using a novel strategy based on a long-pass filter that minimizes the number of HST orbits required to detect and accurately determine Cepheid properties. We carried out a homogeneous reduction and analysis of all observations, including new universal variability searches in all SN Ia hosts, that yielded a total of 2200 variables with well-defined selection criteria -- the largest such sample identified outside the Local Group. These objects are used in a companion paper to determine the local value of H0 with a total uncertainty of 2.4%.

  3. Pulsating combustion - Combustion characteristics and reduction of emissions

    Energy Technology Data Exchange (ETDEWEB)

    Lindholm, Annika

    1999-11-01

    In the search for high efficiency combustion systems pulsating combustion has been identified as one of the technologies that potentially can meet the objectives of clean combustion and good fuel economy. Pulsating combustion offers low emissions of pollutants, high heat transfer and efficient combustion. Although it is an old technology, the interest in pulsating combustion has been renewed in recent years, due to its unique features. Various applications of pulsating combustion can be found, mainly as drying and heating devices, of which the latter also have had commercial success. It is, however, in the design process of a pulse combustor, difficult to predict the operating frequency, the heat release etc., due to the lack of a well founded theory of the phenomenon. Research concerning control over the combustion process is essential for developing high efficiency pulse combustors with low emissions. Natural gas fired Helmholtz type pulse combustors have been the experimental objects of this study. In order to investigate the interaction between the fluid dynamics and the chemistry in pulse combustors, laser based measuring techniques as well as other conventional measuring techniques have been used. The experimental results shows the possibilities to control the combustion characteristics of pulsating combustion. It is shown that the time scales in the large vortices created at the inlet to the combustion chamber are very important for the operation of the pulse combustor. By increasing/decreasing the time scale for the large scale mixing the timing of the heat release is changed and the operating characteristics of the pulse combustor changes. Three different means for NO{sub x} reduction in Helmholtz type pulse combustors have been investigated. These include exhaust gas recirculation, alteration of air/fuel ratio and changed inlet geometry in the combustion chamber. All used methods achieved less than 10 ppm NO{sub x} emitted (referred to stoichiometric

  4. Quantity Discrimination in Domestic Rats, Rattus norvegicus

    Science.gov (United States)

    Cox, Laura; Montrose, V. Tamara

    2016-01-01

    Simple Summary Quantity discrimination involves distinguishing which of two quantities is greater. This discrimination between larger and smaller quantities has only been demonstrated in rats post extensive training. We tested whether domestic rats could perform quantity discrimination without explicit training. We found that rats could distinguish the greater amount in comparisons of 1 vs. 2, 2 vs. 3, 3 vs. 5, 3 vs. 8, 4 vs. 6, and 4 vs. 8. Rats could not distinguish between 3 vs. 4, 4 vs. 5 and 5 vs. 6. We also found that as the ratio between quantities became finer the choice of the larger quantity decreased. We conclude that rats can perform quantity discrimination without extensive training and that their quantity discrimination ability is influenced by the ratio between quantities. Abstract Quantity discrimination is a basic form of numerical competence where an animal distinguishes which of two amounts is greater in size. Whilst quantity discrimination in rats has been investigated via training paradigms, rats’ natural quantity discrimination abilities without explicit training for a desired response have not been explored. This study investigated domestic rats’ ability to perform quantity discrimination. Domestic rats (n = 12) were examined for their ability to distinguish the larger amount under nine quantity comparisons. One-sample t-tests identified a significant preference for the larger quantity in comparisons of 1 vs. 2, 2 vs. 3, 3 vs. 5, 3 vs. 8, 4 vs. 6, and 4 vs. 8. No preference between quantities was found for comparisons of 3 vs. 4, 4 vs. 5 and 5 vs. 6. Overall, this study drew two key conclusions. Firstly, that domestic rats are capable of performing quantity discrimination without extensive training. Secondly, as subjects adhered to Weber’s law, it was concluded that the approximate number system underpins domestic rats’ ability to perform spontaneous quantity discrimination. PMID:27527223

  5. THE MID-INFRARED PERIOD-LUMINOSITY RELATIONS FOR THE SMALL MAGELLANIC CLOUD CEPHEIDS DERIVED FROM SPITZER ARCHIVAL DATA

    International Nuclear Information System (INIS)

    In this paper, we derive the Spitzer IRAC band period-luminosity (P-L) relations for the Small Magellanic Cloud (SMC) Cepheids, by matching the Spitzer archival SAGE-SMC data with the OGLE-III SMC Cepheids. We find that the 3.6 μm and 4.5 μm band P-L relations can be better described using two P-L relations with a break period at log(P) = 0.4: this is consistent with similar results at optical wavelengths for SMC P-L relations. The 5.8 μm and 8.0 μm band P-L relations do not extend to sufficiently short periods to enable a similar detection of a slope change at log(P) = 0.4. The slopes of the SMC P-L relations, for log(P) > 0.4, are consistent with their Large Magellanic Cloud counterparts that were derived from a similar data set. They are also in agreement with those obtained from a small sample of Galactic Cepheids with parallax measurements.

  6. Experimental investigation on a pulsating heat pipe with hydrogen

    Science.gov (United States)

    Deng, H. R.; Liu, Y. M.; Ma, R. F.; Han, D. Y.; Gan, Z. H.; Pfotenhauer, J. M.

    2015-12-01

    The pulsating heat pipe (PHP) has been increasingly studied in cryogenic application, for its high transfer coefficient and quick response. Compared with Nb3Sn and NbTi, MgB2 whose critical transformation temperature is 39 K, is expected to replace some high-temperature superconducting materials at 25 K. In order to cool MgB2, this paper designs a Hydrogen Pulsating Heat Pipe, which allows a study of applied heat, filling ratio, turn number, inclination angle and length of adiabatic section on the thermal performance of the PHP. The thermal performance of the hydrogen PHP is investigated for filling ratios of 35%, 51%, 70% at different heat inputs, and provides information regarding the starting process is received at three filling ratios.

  7. Experimental research on heat transfer of pulsating heat pipe

    Science.gov (United States)

    Li, Jia; Yan, Li

    2008-06-01

    Experimental research was conducted to understand heat transfer characteristic of pulsating heat pipe in this paper, and the PHP is made of high quality glass capillary tube. Under different fill ratio, heat transfer rate and many other influence factors, the flow patterns were observed in the start-up, transition and stable stage. The effects of heating position on heat transfer were discussed. The experimental results indicate that no annular flow appears in top heating condition. Under different fill ratios and heat transfer rate, the flow pattern in PHP is transferred from bulk flow to semi-annular flow and annular flow, and the performance of heat transfer is improved for down heating case. The experimental results indicate that the total heat resistant of PHP is increased with fill ratio, and heat transfer rate achieves optimum at filling rate 50%. But for pulsating heat pipe with changing diameters the thermal resistance is higher than that with uniform diameters.

  8. Pulsations and outbursts in Be stars: Small differences - big impacts

    CERN Document Server

    Baade, D; Pigulski, A; Carciofi, A; Handler, G; Kuschnig, R; Martayan, Ch; Mehner, A; Moffat, A F J; Pablo, H; Popowicz, A; Rucinski, S M; Wade, G A; Weiss, W W; Zwintz, K

    2016-01-01

    New high-cadence observations with BRITE covering many months confirm that coupled pairs of nonradial pulsation modes are widespread among early-type Be stars. With the difference frequency between the parental variations they may form a roughly sinusoidal variability or the amplitude may cyclicly vary. A first - amplified - beat pattern is also found. In all three cases the amplitudes of difference frequencies can exceed the amplitude sum of the base frequencies, and modulations of the star-to-circumstellar-disk mass-transfer rate may be associated with these slow variations. This suggests more strongly than any earlier observations that significant dissipation of pulsational energy in the atmosphere may be a cause of mass ejections from Be stars. A unifying interpretative concept is presented.

  9. Study of the Thermal Pulsation of AGB Stars

    CERN Document Server

    Halabi, Ghina M

    2014-01-01

    A systematic investigation on the third dredge up in a 3M$_{\\odot}$, solar metallicity AGB star will be presented. The model evolves from the main sequence up to the Asymptotic Giant Branch (AGB). Intermediate mass stars are important because they contribute significantly via the slow neutron capture nucleosynthesis. The aim of this work is to gain insight on the behaviour of the AGB star during thermal pulsation. This investigation is based on an extended numerical simulation of the evolutionary phases and full, consistent AGB model calculations. In particular, the convective structure during pulsation will be studied, giving particular emphasis to the analysis of the stability of the Schwarzschild boundary that will eventually determine the occurrence of Third Dredge Up (hereafter referred to as TDUP). We provide a brief description of our updated evolutionary code and focus primarily on the obtaining the TDUP after 14 thermal pulses. We elaborate on the non-standard treatment of convection known as "oversh...

  10. The unique dynamical system underlying RR Lyrae pulsations

    CERN Document Server

    Kolláth, Zoltán

    2016-01-01

    Hydrodynamic models of RR Lyrae pulsation display a very rich behaviour. Contrary to earlier expectations, high order resonances play a crucial role in the nonlinear dynamics representing the interacting modes. Chaotic attractors can be found at different time scales: both in the pulsation itself and in the amplitude equations shaping the possible modulation of the oscillations. Although there is no one-to-one connection between the nonlinear features found in the numerical models and the observed behaviour, the richness of the found phenomena suggests that the interaction of modes should be taken seriously in the study of the still unsolved puzzle of Blazhko effect. One of the main lessons of this complex system is that we should rethink the simple interpretation of the observed effect of resonances.

  11. Experimental research on heat transfer of pulsating heat pipe

    Institute of Scientific and Technical Information of China (English)

    LI Jia; Yan Li

    2008-01-01

    Experimental research was conducted to understand heat transfer characteristic of pulsating heat pipe in this paper,and the PHP is made of high quality glass capillary tube. Under different fill ratio, heat transfer rate and many other influence factors, the flow patterns were observed in the start-up, transition and stable stage. The effects of heating position on heat transfer were discussed. The experimental results indicate that no annular flow appears in top heating condition. Under different fill ratios and heat transfer rate, the flow pattern in PHP is transferred from bulk flow to semi-annular flow and annular flow, and the performance of heat transfer is improved for down heating case. The experimental results indicate that the total heat resistant of PHP is increased with fill ratio, and heat transfer rate achieves optimum at filling rate 50%. But for pulsating heat pipe with changing diameters the thermal resistance is higher than that with uniform diameters.

  12. Modelling the effects of cardiac pulsations in arterial spin labelling

    International Nuclear Information System (INIS)

    It has recently been demonstrated experimentally that cardiac pulsations seem significantly to affect the arterial spin labelling (ASL) signal. In this paper, we introduce a new theoretical model to examine this effect. Existing models of ASL do not take such effects into account since they model the transit of the ASL signal assuming uniform plug flow with a single transit delay. In this study, we model cardiac pulsations through the coupling of the Navier-Stokes equations with the three-dimensional mass transport equation. Our results complement the experimental findings and suggest that the ASL signal does depend on the timing of the onset of the cardiac cycle relative to the tagging and imaging locations. However, cardiac pulsatility only appears to have a small effect on the quantification of perfusion estimates.

  13. Pulsating aurora induced by upper atmospheric barium releases

    Science.gov (United States)

    Deehr, C.; Romick, G.

    1977-01-01

    The paper reports the apparent generation of pulsating aurora by explosive releases of barium vapor near 250 km altitude. This effect occurred only when the explosions were in the path of precipitating electrons associated with the visible aurora. Each explosive charge was a standard 1.5 kg thermite mixture of Ba and CuO with an excess of Ba metal which was vaporized and dispersed by the thermite explosion. Traces of Sr, Na, and Li were added to some of the charges, and monitoring was achieved by ground-based spectrophotometric observations. On March 28, 1976, an increase in emission at 5577 A and at 4278 A was observed in association with the first two bursts, these emissions pulsating with roughly a 10 sec period for approximately 60 to 100 sec after the burst.

  14. The First Six Outbursting Cool DA White Dwarf Pulsators

    CERN Document Server

    Bell, Keaton J; Montgomery, M H; Winget, D E; Fusillo, N P Gentile; Raddi, R; Gänsicke, B T

    2016-01-01

    Extensive observations from the Kepler spacecraft have recently revealed a new outburst phenomenon operating in cool pulsating DA (hydrogen atmosphere) white dwarfs (DAVs). With the introduction of two new outbursting DAVs from K2 Fields 7 (EPIC 229228364) and 8 (EPIC 220453225) in these proceedings, we presently know of six total members of this class of object. We present the observational commonalities of the outbursting DAVs: (1) outbursts that increase the mean stellar flux by up to 15%, last many hours, and recur irregularly on timescales of days; (2) effective temperatures that locate them near the cool edge of the DAV instability strip; and (3) rich pulsation spectra with modes that are observed to wander in amplitude/frequency.

  15. Preliminary study using pulsating water jet for bone cement demolition

    OpenAIRE

    S. Hloch; Kloc, J.; Foldyna, J.; Pude, F.; Smolko, I.; M. Zeleňák; Sitek, L. (Libor); Hvizdoš, P.; Monka, P.; Monková, K.; Kozak, D.; A. Stoić; A. Sedmak; Milosevic, M; Lehocká, D.

    2015-01-01

    The paper deals with the study of using the selective property of ultrasonic pulsating water jet for the disintegration of bone cement which creates the interface between femoral stem and trabecular bone tissue. For investigation, commercial bone cements were used. Bone cements were tested by nanoindentation in order to review their mechanical properties. A representative sample Palacos R+G was selected for disintegration of bone cement. Bone cements samples fixed between two plexiglass...

  16. Mathematical Modelling and Parameter Optimization of Pulsating Heat Pipes

    OpenAIRE

    Yang, Xin-She; Karamanoglu, Mehmet; Luan, Tao; Koziel, Slawomir

    2014-01-01

    Proper heat transfer management is important to key electronic components in microelectronic applications. Pulsating heat pipes (PHP) can be an efficient solution to such heat transfer problems. However, mathematical modelling of a PHP system is still very challenging, due to the complexity and multiphysics nature of the system. In this work, we present a simplified, two-phase heat transfer model, and our analysis shows that it can make good predictions about startup characteristics. Furtherm...

  17. Noise Radiation Of A Strongly Pulsating Tailpipe Exhaust

    Science.gov (United States)

    Peizi, Li; Genhua, Dai; Zhichi, Zhu

    1993-11-01

    The method of characteristics is used to solve the problem of the propagation of a strongly pulsating flow in an exhaust system tailpipe. For a strongly pulsating exhaust, the flow may shock at the pipe's open end at some point in a pulsating where the flow pressure exceeds its critical value. The method fails if one insists on setting the flow pressure equal to the atmospheric pressure as the pipe end boundary condition. To solve the problem, we set the Mach number equal to 1 as the boundary condition when the flow pressure exceeds its critical value. For a strongly pulsating flow, the fluctuations of flow variables may be much higher than their respective time averages. Therefore, the acoustic radiation method would fail in the computation of the noise radiation from the pipe's open end. We simulate the exhaust flow out of the open end as a simple sound source to compute the noise radiation, which has been successfully applied in reference [1]. The simple sound source strength is proportional to the volume acceleration of exhaust gas. Also computed is the noise radiation from the turbulence of the exhaust flow, as was done in reference [1]. Noise from a reciprocating valve simulator has been treated in detail. The radiation efficiency is very low for the pressure range considered and is about 10 -5. The radiation efficiency coefficient increases with the square of the frequency. Computation of the pipe length dependence of the noise radiation and mass flux allows us to design a suitable length for an aerodynamic noise generator or a reciprocating internal combustion engine. For the former, powerful noise radiation is preferable. For the latter, maximum mass flux is desired because a freer exhaust is preferable.

  18. Nonstationary pearl pulsations as a signature of magnetospheric disturbances

    OpenAIRE

    Feygin, F. Z.; Kleimenova, N. G.; O. A. Pokhotelov; M. Parrot; K. Prikner; K. Mursula; J. Kangas; Pikkarainen, T.

    2000-01-01

    We analyse long-lasting (several hours) Pc1 pearl pulsations with decreasing, increasing or constant central frequencies. We show that nonstationary pearl events (those with either decreasing or increasing central frequency) are observed simultaneously with increasing auroral magnetic activity at the nightside magnetosphere while the stationary events (constant central frequency) correspond to quiet magnetic conditions. Events with decreasing central frequency are observed mostly in the late ...

  19. Self-pulsation threshold of Raman amplified Brillouin fiber cavities

    DEFF Research Database (Denmark)

    Ott, Johan Raunkjær; Pedersen, Martin Erland Vestergaard; Rottwitt, Karsten

    2009-01-01

    An implicit equation for the oscillation threshold of stimulated Brillouin scattering from Raman amplified signals in fibers with external feedback is derived under the assumption of no depletion. This is compared to numerical investigations of Raman amplification schemes showing good agreement...... for high reflectivities. For low reflectivities and high attenuation or long fibers, the assumption of no depletion is shown not to be valid. In these cases the effects of the depletion on the self-pulsation is examined....

  20. Pressure Pulsation Signal Analysis for Centrifugal Compressor Blade Crack Determination

    OpenAIRE

    Hongkun Li; Xuefeng Zhang; Xiaowen Zhang; Shuhua Yang; Fujian Xu

    2014-01-01

    Blade is a key piece of component for centrifugal compressor. But blade crack could usually occur as blade suffers from the effect of centrifugal forces, gas pressure, friction force, and so on. It could lead to blade failure and centrifugal compressor closing down. Therefore, it is important for blade crack early warning. It is difficult to determine blade crack as the information is weak. In this research, a pressure pulsation (PP) sensor installed in vicinity to the crack area is used to d...

  1. Decreasing of pulsation intensity levels in X-ray receivers

    CERN Document Server

    Dvoryankin, V F; Kudryashov, A A; Petrov, A G

    2002-01-01

    The low frequency filter is applied in the multichannel receiver on the basis of the GaAs epitaxial structures for decreasing the pulsations level at the signals amplifier outlet. The optimal band of the filter is determined by the transition processes by the detector scanning in the roentgen beams. The X-ray source of radiation with the medium-frequency feeding generator is used for verifying the quality of the obtained X-ray image

  2. Damping Pressure Pulsations in a Wave-Powered Desalination System

    OpenAIRE

    Padhye, Nikhil; Torres, James, Ph. D. Massachusetts Institute of Technology.; Thomas, Levon; Ljubicic, Dean M.; Kassner, Mortiz P.; Slocum, Alexander H.; Hopkins, Brandon James; Greenlee, Alison S.

    2014-01-01

    Wave-driven reverse osmosis desalination systems can be a cost-effective option for providing a safe and reliable source of drinking water for large coastal communities. Such systems usually require the stabilization of pulsating pressures for desalination purposes. The key challenge is to convert a fluctuating pressure flow into a constant pressure flow. To address this task, stub-filters, accumulators, and radially elastic-pipes are considered for smoothing the pressure fluctuations in the ...

  3. Numerical Calculation on Cavitation Pressure Pulsation in Centrifugal Pump

    OpenAIRE

    Weidong Shi; Chuan Wang; Wei Wang; Bing Pei

    2014-01-01

    In order to study the internal flow in centrifugal pump when cavitation occurs, numerical calculation of the unsteady flow field in the WP7 automobile centrifugal pump is conducted based on the Navier-Stokes equations with the RNG k-ε turbulence model and Zwart-Gerber-Belamri cavitation model. The distributions of bubble volume fraction and pressure pulsation laws in the pump are analyzed when cavitation occurs. The conclusions are as follows: the bubble volume fraction is larger on the sucti...

  4. Asteroseismology of hybrid $\\delta$ Scuti--$\\gamma$ Doradus pulsating stars

    CERN Document Server

    Arias, J P Sánchez; Althaus, L G

    2016-01-01

    Hybrid $\\delta$ Scuti-$\\gamma$ Doradus pulsating stars show acoustic ($p$) oscillation modes typical of $\\delta$ Scuti variable stars, and gravity ($g$) pulsation modes characteristic of $\\gamma$ Doradus variable stars simultaneously excited. Observations from space missions like MOST, CoRoT, and \\emph{Kepler} have revealed a large number of hybrid $\\delta$ Scuti-$\\gamma$ Doradus pulsators, thus paving the way for a exciting new channel for asteroseismic studies. We perform a detailed asteroseismological modeling of five hybrid $\\delta$ Scuti-$\\gamma$ Doradus stars. We employ a grid-based modeling approach to sound the internal structure of the target stars by employing a huge grid of stellar models from the zero-age main sequence to the terminal-age main sequence, varying parameters like stellar mass, effective temperature, metallicity and core overshooting. We compute their adiabatic radial ($\\ell= 0$) and non-radial ($\\ell= 1, 2, 3$) $p$ and $g$ mode periods. We employ two model-fitting procedures to searc...

  5. Pulsations powered by hydrogen shell burning in white dwarfs

    CERN Document Server

    Camisassa, María E; Althaus, Leandro G; Shibahashi, Hiromoto

    2016-01-01

    In the absence of a third dredge-up episode during the asymptotic giant branch phase, white dwarf models evolved from low-metallicity progenitors have a thick hydrogen envelope, which makes hydrogen shell burning be the most important energy source. We investigate the pulsational stability of white dwarf models with thick envelopes to see whether nonradial $g$-mode pulsations are triggered by hydrogen burning, with the aim of placing constraints on hydrogen shell burning in cool white dwarfs and on a third dredge-up during the asymptotic giant branch evolution of their progenitor stars. We construct white-dwarf sequences from low-metallicity progenitors by means of full evolutionary calculations, and analyze their pulsation stability for the models in the range of effective temperatures $T_{\\rm eff} \\sim 15\\,000\\,-\\, 8\\,000$ K. We demonstrate that, for white dwarf models with masses $M_{\\star} \\lesssim 0.71\\,\\rm M_{\\sun}$ and effective temperatures $8\\,500 \\lesssim T_{\\rm eff} \\lesssim 11\\,600$ K that evolved...

  6. Dark Stars: Improved Models and First Pulsation Results

    Science.gov (United States)

    Rindler-Daller, T.; Montgomery, M. H.; Freese, K.; Winget, D. E.; Paxton, B.

    2015-02-01

    We use the stellar evolution code MESA to study dark stars (DSs). DSs, which are powered by dark matter (DM) self-annihilation rather than by nuclear fusion, may be the first stars to form in the universe. We compute stellar models for accreting DSs with masses up to 106 M ⊙. The heating due to DM annihilation is self-consistently included, assuming extended adiabatic contraction of DM within the minihalos in which DSs form. We find remarkably good overall agreement with previous models, which assumed polytropic interiors. There are some differences in the details, with positive implications for observability. We found that, in the mass range of 104-105 M ⊙, our DSs are hotter by a factor of 1.5 than those in Freese et al., are smaller in radius by a factor of 0.6, denser by a factor of three to four, and more luminous by a factor of two. Our models also confirm previous results, according to which supermassive DSs are very well approximated by (n = 3)-polytropes. We also perform a first study of DS pulsations. Our DS models have pulsation modes with timescales ranging from less than a day to more than two years in their rest frames, at z ~ 15, depending on DM particle mass and overtone number. Such pulsations may someday be used to identify bright, cool objects uniquely as DSs; if properly calibrated, they might, in principle, also supply novel standard candles for cosmological studies.

  7. Constraining the neutrino magnetic dipole moment from white dwarf pulsations

    CERN Document Server

    Córsico, Alejandro H; Bertolami, Marcelo M Miller; Kepler, S O; García-Berro, Enrique

    2014-01-01

    Pulsating white dwarf stars can be used as astrophysical laboratories to constrain the properties of weakly interacting particles. Comparing the cooling rates of these stars with the expected values from theoretical models allows us to search for additional sources of cooling due to the emission of axions, neutralinos, or neutrinos with magnetic dipole moment. In this work, we derive an upper bound to the neutrino magnetic dipole moment using an estimate of the rate of period change of the pulsating DB white dwarf star PG 1351+489. By comparing the theoretical rate of change of period expected for this star with the rate of change of period with time of PG 1351+489, we assess the possible existence of additional cooling by neutrinos with magnetic dipole moment. Our models suggest the existence of some additional cooling in this pulsating DB white dwarf, consistent with a non-zero magnetic dipole moment. Our upper limit for the neutrino magnetic dipole moment is somewhat less restrictive than, but still compat...

  8. Quantity Cognition: Numbers, Numerosity, Zero and Mathematics.

    Science.gov (United States)

    Harvey, Ben M

    2016-05-23

    Physical quantities differ from abstract numbers and mathematics, but recent results are revealing the neural representation of both: a new study demonstrates how an absence of quantity is transformed into a representation of zero as a number.

  9. GW Librae: A unique laboratory for pulsations in an accreting white dwarf

    CERN Document Server

    Toloza, O; Hermes, J J; Townsley, D M; Schreiber, M R; Szkody, P; Pala, A; Beuermann, K; Bildsten, L; Breedt, E; Cook, M; Godon, P; Henden, A A; Hubeny, I; Knigge, C; Long, K S; Marsh, T R; de Martino, D; Mukadam, A S; Myers, G; Nelson, P; Oksanen, A; Patterson, J; Sion, E M; Zorotovic, M

    2016-01-01

    Non-radial pulsations have been identified in a number of accreting white dwarfs in cataclysmic variables. These stars offer insight into the excitation of pulsation modes in atmospheres with mixed compositions of hydrogen, helium, and metals, and the response of these modes to changes in the white dwarf temperature. Among all pulsating cataclysmic variable white dwarfs, GW Librae stands out by having a well-established observational record of three independent pulsation modes that disappeared when the white dwarf temperature rose dramatically following its 2007 accretion outburst. Our analysis of HST ultraviolet spectroscopy taken in 2002, 2010 and 2011, showed that pulsations produce variations in the white dwarf effective temperature as predicted by theory. Additionally in May~2013, we obtained new HST/COS ultraviolet observations that displayed unexpected behaviour: besides showing variability at ~275s, which is close to the post-outburst pulsations detected with HST in 2010 and 2011, the white dwarf exhi...

  10. An In-Depth Spectroscopic Analysis of RR Lyr Variations over the Pulsation Cycle

    CERN Document Server

    Fossati, L; Shulyak, D V; Elmasli, A; Tsymbal, V; Barnes, T G; Guggenberger, E; Kochukhov, O

    2014-01-01

    The stellar parameters of RR Lyrae stars vary considerably over a pulsation cycle, and their determination is crucial for stellar modelling. We present a detailed spectroscopic analysis of the pulsating star RR Lyr, the prototype of its class, over a complete pulsation cycle, based on high-resolution spectra collected at the 2.7-m telescope of McDonald Observatory. We used simultaneous photometry to determine the accurate pulsation phase of each spectrum and determined the effective temperature, the shape of the depth-dependent microturbulent velocity, and the abundance of several elements, for each phase. The surface gravity was fixed to 2.4. Element abundances resulting from our analysis are stable over the pulsation cycle. However, a variation in ionisation equilibrium is observed around minimum radius. We attribute this mostly to a dynamical acceleration contributing to the surface gravity. Variable turbulent convection on time scales longer than the pulsation cycle has been proposed as a cause for the Bl...

  11. An experimental investigation of heat transfer to pulsating pipe air flow with different amplitudes

    Science.gov (United States)

    Zohir, A. E.; Habib, M. A.; Attya, A. M.; Eid, A. I.

    2006-05-01

    Heat transfer characteristics to both laminar and turbulent pulsating pipe flows under different conditions of Reynolds number, pulsation frequency, pulsator location and tube diameter were experimentally investigated. The tube wall of uniform heat flux condition was considered for both cases. Reynolds number varied from 750 to 12,320 while the frequency of pulsation ranged from 1 to 10 Hz. With locating the pulsator upstream of the inlet of the test section tube, results showed an increase in heat transfer rate due to pulsation by as much as 30% with flow Reynolds number of 1,643 and pulsation frequency of 1 Hz, depending on the upstream location of the pulsator valve. Closer the valve to the tested section inlet, the better improvement in the heat transfer coefficient is achieved. Upon comparing the heat transfer results of the upstream and the downstream pulsation, at Reynolds number of 1,366 and 1,643, low values of the relative mean Nusselt number were obtained with the upstream pulsation. Comparing the heat transfer results of the two studied test sections tubes for Reynolds number range from 8,000 to 12,000 and pulsation frequency range from 1.0 to 10 Hz showed that more improvement in heat transfer rate was observed with a larger tube diameter. For Reynolds number ranging from 8,000 to 12,000 and pulsation frequency of 10 Hz, an improvement in the relative mean Nusselt number of about 50% was obtained at Reynolds number of 8,000 for the large test section diameter of 50 mm. While, for the small test section diameter of 15 mm, at same conditions of Reynolds number and frequency, a reduction in the relative mean Nusselt number of up to 10% was obtained.

  12. An experimental investigation of heat transfer to pulsating pipe air flow with different amplitudes

    Energy Technology Data Exchange (ETDEWEB)

    Zohir, A.E.; Eid, A.I. [Tabbin Institute for Metallurgical Studies-Eltabbin, Helwan (Egypt); Habib, M.A. [King Fahd University of Petroleum and Minerals, Mechanical Engineering Department, Dhahran (Saudi Arabia); Cairo University, Mechanical Engineering Department, Cairo (Egypt); Attya, A.M. [Cairo University, Mechanical Engineering Department, Cairo (Egypt)

    2006-05-15

    Heat transfer characteristics to both laminar and turbulent pulsating pipe flows under different conditions of Reynolds number, pulsation frequency, pulsator location and tube diameter were experimentally investigated. The tube wall of uniform heat flux condition was considered for both cases. Reynolds number varied from 750 to 12,320 while the frequency of pulsation ranged from 1 to 10 Hz. With locating the pulsator upstream of the inlet of the test section tube, results showed an increase in heat transfer rate due to pulsation by as much as 30% with flow Reynolds number of 1,643 and pulsation frequency of 1 Hz, depending on the upstream location of the pulsator valve. Closer the valve to the tested section inlet, the better improvement in the heat transfer coefficient is achieved. Upon comparing the heat transfer results of the upstream and the downstream pulsation, at Reynolds number of 1,366 and 1,643, low values of the relative mean Nusselt number were obtained with the upstream pulsation. Comparing the heat transfer results of the two studied test sections tubes for Reynolds number range from 8,000 to 12,000 and pulsation frequency range from 1.0 to 10 Hz showed that more improvement in heat transfer rate was observed with a larger tube diameter. For Reynolds number ranging from 8,000 to 12,000 and pulsation frequency of 10 Hz, an improvement in the relative mean Nusselt number of about 50% was obtained at Reynolds number of 8,000 for the large test section diameter of 50 mm. While, for the small test section diameter of 15 mm, at same conditions of Reynolds number and frequency, a reduction in the relative mean Nusselt number of up to 10% was obtained. (orig.)

  13. A revised ephemeris for the pulsating hydrogen-deficient star BD + 130 3224 (V652 Her)

    International Nuclear Information System (INIS)

    Additional observations of maxima of the pulsating hydrogen-deficient star, BD + 130 3224 (V652 Her), give an improved ephemeris for the decreasing period of pulsation. A simple quadratic no longer appears sufficient and a cubic solution may be preferable, indicating that the pulsation decrease rate is slowing down as the star contracts. An alternative hypotheses, that the star is a binary is also discussed. (author)

  14. The Separation Performance of the Pulsating High–Gradient Magnetic Separator

    OpenAIRE

    Peng, Yang; Shuyi, Liu; Jin, Chen

    1993-01-01

    In order to develop the pulsating high–gradient magnetic separation technology, a laboratory pulsating high–gradient magnetic separator (PHGMS) has been manufactured.. Experiments on its separation performance were carried out. The results show that PHGMS can significantly increase the grade of the magnetic product and it can eliminate the matrix clogging. The characteristic curve of the pulsating fluid was measured and a formula for estimating the grade of the magnetic product from PHGMS was...

  15. Investigation on the Possible Relationship between Magnetic Pulsations and Earthquakes

    Science.gov (United States)

    Jusoh, M.; Liu, H.; Yumoto, K.; Uozumi, T.; Takla, E. M.; Yousif Suliman, M. E.; Kawano, H.; Yoshikawa, A.; Asillam, M.; Hashim, M.

    2012-12-01

    The sun is the main source of energy to the solar system, and it plays a major role in affecting the ionosphere, atmosphere and the earth surface. The connection between solar wind and the ground magnetic pulsations has been proven empirically by several researchers previously (H. J. Singer et al., 1977, E. W. Greenstadt, 1979, I. A. Ansari 2006 to name a few). In our preliminary statistical analysis on relationship between solar and seismic activities (Jusoh and Yumoto, 2011, Jusoh et al., 2012), we observed a high possibility of solar-terrestrial coupling. We observed high tendency of earthquakes to occur during lower phase solar cycles which significantly related with solar wind parameters (i.e solar wind dynamic pressure, speed and input energy). However a clear coupling mechanism was not established yet. To connect the solar impact on seismicity, we investigate the possibility of ground magnetic pulsations as one of the connecting agent. In our analysis, the recorded ground magnetic pulsations are analyzed at different ranges of ultra low frequency; Pc3 (22-100 mHz), Pc4 (6.7-22 mHz) and Pc5 (1.7-6.7 mHz) with the occurrence of local earthquake events at certain time periods. This analysis focuses at 2 different major seismic regions; north Japan (mid latitude) and north Sumatera, Indonesia (low latitude). Solar wind parameters were obtained from the Goddard Space Flight Center, NASA via the OMNIWeb Data Explorer and the Space Physics Data Facility. Earthquake events were extracted from the Advanced National Seismic System (ANSS) database. The localized Pc3-Pc5 magnetic pulsations data were extracted from Magnetic Data Acquisition System (MAGDAS)/Circum Pan Magnetic Network (CPMN) located at Ashibetsu (Japan); for earthquakes monitored at north Japan and Langkawi (Malaysia); for earthquakes observed at north Sumatera. This magnetometer arrays has established by International Center for Space Weather Science and Education, Kyushu University, Japan. From the

  16. Heat transfer characteristics and Nusselt number correlation of turbulent pulsating pipe air flows

    Energy Technology Data Exchange (ETDEWEB)

    Habib, M.A.; Said, S.A.M. [Mechanical Engineering Department, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Attya, A.M.; Eid, A.I.; Aly, A.Z. [Mechanical Engineering Department, Faculty of Engineering, Cairo University (Egypt)

    2004-02-01

    Heat transfer characteristics to turbulent pulsating pipe flows under a wide range of Reynolds number and pulsation frequency were experimentally investigated under uniform heat flux condition. Reynolds number was varied from 8462 to 48540 while the frequency of pulsation ranged from 1 to 29.5 Hz. The results showed that the relative mean Nusselt number is strongly affected by both pulsation frequency and Reynolds number. Enhancements in mean Nusselt number of up to 50% were obtained at medium pulsation frequency between 4.1 and 13.9 Hz for Reynolds number range of 8462 to 14581. An enhancement of up to 50% in mean Nusselt number was obtained at high pulsation frequency range between 13.9 and 29.5 Hz, specially as Reynolds number is close to 15000, while a reduction was observed at higher Reynolds number more than 21200. This reduction, at high Reynolds number, increased as pulsation frequency increased. Also, there was a reduction in mean Nusselt number of up to 20% that obtained at low pulsation frequency range between 1 and 4.1 Hz for Reynolds number range of 8462 to 48543. A significant reduction in mean Nusselt number of up to 40% was obtained at medium pulsation frequency between 4.1 and 13.9 Hz for Reynolds number range of 21208 to 48543. Empirical equations have been developed for the relative mean Nusselt number that related to Reynolds number and dimensionless frequency with about uncertainty of 10% rms. (orig.)

  17. White Dwarf Period Tables - I. Pulsators with hydrogen-dominated atmospheres

    CERN Document Server

    Bognár, Zs

    2016-01-01

    We aimed at collecting all known white dwarf pulsators with hydrogen-dominated atmospheres and list their main photometric and atmospheric parameters together with their pulsation periods and amplitudes observed at different epochs. For this purpose, we explored the pulsating white dwarf related literature with the systematic use of the SIMBAD and the NASA's Astrophysics Data System (ADS) databases. We summarized our results in four tables listing seven ZZ Ceti stars in detached white dwarf plus main-sequence binaries, seven extremely low-mass DA pulsators, three hot DAVs and 180 ZZ Ceti stars.

  18. On the periodic variations of secondary cosmic rays and the geomagnetic Pc4 pulsations in BMAr

    Directory of Open Access Journals (Sweden)

    I. M. Martin

    Full Text Available In a set of balloon flights in the Brazilian magnetic anomaly region (BMAr short time periodic variations were observed, i.e. pulsation, of secondary charged and neutral particle fluxes, X- and -ray fluxes with amplitudes of about 2–4%. The pulsations are accompanied by the geomagnetic Pc4 pulsations and have similar periodicity. The phenomenon was observed over various local times and in quiet and disturbed magnetospheric conditions. One of the explanations of this effect, i.e. periodic variation of local cut-off rigidity, and following pulsations of primary and secondary cosmic ray intensity is suggested.

  19. Anchors for the Cosmic Distance Scale: the Cepheid QZ Normae in the Open Cluster NGC 6067

    CERN Document Server

    Majaess, D; Bidin, C Moni; Soto, M; Gieren, W; Cohen, R; Mauro, F; Geisler, D; Bonatto, C; Borissova, J; Minniti, D; Turner, D; Lane, D; Madore, B; Carraro, G; Berdnikov, L

    2013-01-01

    Cepheids are key to establishing the cosmic distance scale. Therefore it's important to assess the viability of QZ Nor, V340 Nor, and GU Nor as calibrators for Leavitt's law via their purported membership in the open cluster NGC 6067. The following suite of evidence confirms that QZ Nor and V340 Nor are members of NGC 6067, whereas GU Nor likely lies in the foreground: (i) existing radial velocities for QZ Nor and V340 Nor agree with that established for the cluster (-39.4+-1.2 km/s) to within 1 km/s, whereas GU Nor exhibits a markedly smaller value; (ii) a steep velocity-distance gradient characterizes the sight-line toward NGC 6067, thus implying that objects sharing common velocities are nearly equidistant; (iii) a radial profile constructed for NGC 6067 indicates that QZ Nor is within the cluster bounds, despite being 20' from the cluster center; (iv) new BVJH photometry for NGC 6067 confirms the cluster lies d=1.75+-0.10 kpc distant, a result that matches Wesenheit distances computed for QZ Nor/V340 Nor ...

  20. The CoRoT discovery of a unique triple-mode cepheid in the galaxy

    CERN Document Server

    Poretti, Ennio; Weiss, Werner W

    2014-01-01

    The exploitation of the CoRoT treasure of stars observed in the exoplanetary field allowed the detection of a unusual triple-mode Cepheid in the Milky Way, CoRoT 0223989566. The two modes with the largest amplitudes and period ratio of 0.80 are identified with the first (P1=1.29 d) and second (P2=1.03 d) radial overtones. The third period, which has the smallest amplitude but able to produce combination terms with the other two, is the longest one (P3=1.89 d). The ratio of 0.68 between the first-overtone period and the third period is the unusual feature. Its identification with the fundamental radial or a nonradial mode is discussed with respect to similar cases in the Magellanic Clouds. In both cases the period triplet and the respective ratios make the star unique in our Galaxy. The distance derived from the period-luminosity relation and the galactic coordinates put CoRoT~0223989566 in the metal-rich environment of the "outer arm" of the Milky Way.

  1. THE CoRoT DISCOVERY OF A UNIQUE TRIPLE-MODE CEPHEID IN THE GALAXY

    Energy Technology Data Exchange (ETDEWEB)

    Poretti, E. [INAF-Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate (Italy); Baglin, A. [LESIA, Université Pierre et Marie Curie, Université Denis Diderot, Observatoire de Paris, F-92195 Meudon Cedex (France); Weiss, W. W., E-mail: ennio.poretti@brera.inaf.it [Institute of Astronomy, University of Vienna, Türkenschanzstrasse 17, A-1180 Vienna (Austria)

    2014-11-10

    The exploitation of the CoRoT treasure of stars observed in the exoplanetary field allowed the detection of a unusual triple-mode Cepheid in the Milky Way, CoRoT 0223989566. The two modes with the largest amplitudes and a period ratio of 0.80 are identified with the first (P {sub 1} = 1.29 days) and second (P {sub 2} = 1.03 days) radial overtones. The third period, which has the smallest amplitude but is able to produce combination terms with the other two, is the longest one (P {sub 3} = 1.89 days). The ratio of 0.68 between the first-overtone period and the third period is the unusual feature. Its identification with the fundamental radial or a nonradial mode is discussed with respect to similar cases in the Magellanic Clouds. In both cases, the period triplet and the respective ratios make the star unique in our Galaxy. The distance derived from the period-luminosity relation and the galactic coordinates put CoRoT 0223989566 in the metal-rich environment of the ''outer arm'' of the Milky Way.

  2. VizieR Online Data Catalog: The VMC survey. XIX. Classical Cepheids in SMC (Ripepi+, 2016)

    Science.gov (United States)

    Ripepi, V.; Marconi, M.; Moretti, M. I.; Clementini, G.; Cioni, M.-R.; de Grijs, R.; Emerson, J. P.; Groenewegen, M. A. T.; Ivanov, V. D.; Piatti, A. E.

    2016-07-01

    In this paper, we present results for the Classical Cepheids (CCs) included in 11 tiles (each tile is 1.5deg2 on the sky) completely or nearly completely observed, processed, and cataloged by the "VISTA near-infrared YJKs survey of the Magellanic Clouds System" (VMC) survey as of 2015 March 9 (including observations obtained until 2014 September). See Figure 1. VMC is a European Southern Observatory (ESO) public survey that is carried out with VIRCAM (VISTA InfraRed Camera) on the ESO/VISTA telescope. The scope of this paper is to present the results for the CCs in the SMC after four years of VMC observations. The SMC is known to host more than 4500 CCs, according to the OGLE III (Soszynski et al. 2010, J/AcA/60/17) and EROS 2 (Tisserand et al. 2007A&A...469..387T; Kim et al. 2014, J/A+A/566/A43) surveys. (2 data files).

  3. Modern observations of Hubble's first-discovered Cepheid in M31

    CERN Document Server

    Templeton, M; Goff, W; Smith, S; Sabo, R; Walker, G; Buchheim, R; Belcheva, G; Crawford, T; Cook, M; Dvorak, S; Harris, B

    2011-01-01

    We present a modern ephemeris and modern light curve of the first-discovered Cepheid variable in M31, Edwin Hubble's M31-V1. Observers of the American Association of Variable Star Observers undertook these observations during the latter half of 2010. The observations were in support of an outreach program by the Space Telescope Science Institute's Hubble Heritage project, but the resulting data are the first concentrated observations of M31-V1 made in modern times. AAVSO observers obtained 214 V-band, Rc-band, and unfiltered observations from which a current ephemeris was derived. The ephemeris derived from these observations is JD(Max) = 2455430.5(+/-0.5) + 31.4 (+/-0.1) E. The period derived from the 2010 data are in agreement with the historic values of the period, but the single season of data precludes a more precise determination of the period or measurement of the period change using these data alone. However, using an ephemeris based upon the period derived by Baade and Swope we are able to fit all of...

  4. DARK STARS: IMPROVED MODELS AND FIRST PULSATION RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    Rindler-Daller, T.; Freese, K. [Department of Physics and Michigan Center for Theoretical Physics, University of Michigan, Ann Arbor, MI 48109 (United States); Montgomery, M. H.; Winget, D. E. [Department of Astronomy, McDonald Observatory and Texas Cosmology Center, University of Texas, Austin, TX 78712 (United States); Paxton, B. [Kavli Insitute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States)

    2015-02-01

    We use the stellar evolution code MESA to study dark stars (DSs). DSs, which are powered by dark matter (DM) self-annihilation rather than by nuclear fusion, may be the first stars to form in the universe. We compute stellar models for accreting DSs with masses up to 10{sup 6} M {sub ☉}. The heating due to DM annihilation is self-consistently included, assuming extended adiabatic contraction of DM within the minihalos in which DSs form. We find remarkably good overall agreement with previous models, which assumed polytropic interiors. There are some differences in the details, with positive implications for observability. We found that, in the mass range of 10{sup 4}-10{sup 5} M {sub ☉}, our DSs are hotter by a factor of 1.5 than those in Freese et al., are smaller in radius by a factor of 0.6, denser by a factor of three to four, and more luminous by a factor of two. Our models also confirm previous results, according to which supermassive DSs are very well approximated by (n = 3)-polytropes. We also perform a first study of DS pulsations. Our DS models have pulsation modes with timescales ranging from less than a day to more than two years in their rest frames, at z ∼ 15, depending on DM particle mass and overtone number. Such pulsations may someday be used to identify bright, cool objects uniquely as DSs; if properly calibrated, they might, in principle, also supply novel standard candles for cosmological studies.

  5. Appraisal of electromagnetic induction effects on magnetic pulsation studies

    Directory of Open Access Journals (Sweden)

    B. R. Arora

    Full Text Available The quantification of wave polarization characteristics of ULF waves from the geomagnetic field variations is done under ‘a priori’ assumption that fields of internal induced currents are in-phase with the external inducing fields. Such approximation is invalidated in the regions marked by large lateral conductivity variations that perturb the flow pattern of induced currents. The amplitude and phase changes that these perturbations produce, in the resultant fields at the Earth’s surface, make determination of polarization and phase of the oscillating external signals problematic. In this paper, with the help of a classical Pc5 magnetic pulsation event of 24 March 1991, recorded by dense network of magnetometers in the equatorial belt of Brazil, we document the nature and extent of the possible influence of anomalous induction effects in the wave polarization of ULF waves. The presence of anomalous induction effects at selected sites lead to an over estimation of the equatorial enhancement at pulsation period and also suggest changes in the azimuth of ULF waves as they propagate through the equatorial electrojet. Through numerical calculations, it is shown that anomalous horizontal fields, that result from induction in the lateral conductivity distribution in the study region, vary in magnitude and phase with the polarization of external source field. Essentially, the induction response is also a function of the period of external inducing source field. It is further shown that when anomalous induction fields corresponding to the magnitude and polarization of the 24 March 1991 pulsation event are eliminated from observed fields, corrected amplitude in the X and Y horizontal components allows for true characterisation of ULF wave parameters.

    Key words. Geomagnetism and paleomagnetism (geomagnetic induction – Ionosphere (equatorial ionosphere – Magnetospheric physics (magnetosphere-ionosphere interactions

  6. Pi2 pulsations and substorm onsets: A review

    Science.gov (United States)

    Olson, John V.

    1999-08-01

    Pi2 pulsations have been the subject of continuous study since they were recognized to be an integral part of the magnetospheric substorm. With the advent of arrays of ground instruments the nature of the Pi2 has begun to be understood. As adopted by the 13th General Assembly of the International Union of Geodesy and Geophysics in 1963, Pi2 is a designation that includes impulsive pulsations in the period range from 40 to 150 s. The Pi2 signal encompasses a class of pulsations that represents two fundamental processes. The first process is the sudden generation of field-aligned currents in association with the disruption of cross-tail currents in the plasma sheet and their subsequent effects on the ionosphere. The ionosphere appears to be something more than a passive load for this electrodynamic impulse. It responds, sending currents back into a magnetosphere whose topology is changing and, perhaps producing the feedback necessary to cause the explosive growth of the substorm current system. Oscillations of these currents are detected across the nightside of the Earth at onset as the midlatitude and high-latitude portions of Pi2. The second process is the impulse response of the inner magnetosphere to the compressional waves that are generated at substorm onset. Traveling inward, they stimulate field line resonances and surface waves at the plasmapause and excite global oscillations in the inner magnetosphere. The two processes produce wave modes that couple and cross-couple threading energy into the inner magnetosphere and ultimately to the ground. The purpose of this review is to construct a phenomenological overview of the Pi2.

  7. The domains of instability for the pulsating PG1159 stars.

    Energy Technology Data Exchange (ETDEWEB)

    Quirion, P.-O.; Fontaine, Gilles.; Brassard, Pierre; Herwig, F. H. (Falk H.)

    2004-01-01

    The fact that we find pulsating and nonpulsating stars mixed together in the PG 1159 region of the log g - T{sub eff} diagram has been a long standing puzzle. The poor understanding of the driving mechanism in those stars has been the reason why it has taken so long to address properly this problem. Following the work of Saio (1996) and Gautschy (1997) based on the OPAL opacities, Quirion, Fontaine, & Brassard (2004) recently showed that we are now able to understand and reproduce the ranges of observed periods in the pulsating PG 1159 stars in terms of the original {kappa}-mechanism associated with the partial ionization of the K-shell electrons of C and O which, along with He, make up the composition of the envelope of those stars. Contrary to others, those three studies agree in that no composition gradients are needed between the atmospheric layers and the driving region. Furthermore, the cohabitation of pulsating and nonpulsating PG 1159 stars is naturally explained in terms of a dispersion in atmospheric parameters and in terms of a variation in surface composition from star to star. In particular, the most He-rich stars tend to be stable. We go beyond the findings discussed by Quirion et al. (2004) in this paper, and present the results of additional calculations aimed at describing better the role of the chemical composition (in particular the role of metallicity) as well as that of the stellar mass on the boundaries of the instability domain in the log g - T{sub eff} plane.

  8. Multiplicity of Galactic Cepheids from long-baseline interferometry~III. Sub-percent limits on the relative brightness of a close companion of $\\delta$~Cephei

    CERN Document Server

    Gallenne, A; Kervella, P; Monnier, J D; Schaefer, G H; Roettenbacher, R M; Gieren, W; Pietrzynski, G; McAlister, H; Brummelaar, T ten; Sturmann, J; Sturmann, L; Turner, N; Anderson, R I

    2016-01-01

    We report new CHARA/MIRC interferometric observations of the Cepheid archetype $\\delta$ Cep, which aimed at detecting the newly discovered spectroscopic companion. We reached a maximum dynamic range $\\Delta H $ = 6.4, 5.8, and 5.2 mag, respectively within the relative distance to the Cepheid $r 9.15, 8.31$ and 7.77 mag, respectively for $r < 25$ mas, $25 < r < 50$ mas and $50 < r < 100$ mas. We also found that to be consistent with the predicted orbital period, the companion has to be located at a projected separation $< 24$ mas with a spectral type later than a F0V star.

  9. An Experimental Investigation of Micro Pulsating Heat Pipes

    OpenAIRE

    Kai-Shing Yang; Yu-Chi Cheng; Ming-Shan Jeng; Kuo-Hsiang Chien; Jin-Cherng Shyu

    2014-01-01

    Two Si-based micro pulsating heat pipes (µPHPs) charged using HFE-7100 were either horizontally or vertically oriented and were tested using several heating powers. The width of each channel was 0.8 mm in one µPHP containing uniform channels, and the channel width was 1.0 mm or 0.6 mm in the other µPHP, which did not contain uniform channels. The depth of each channel was 0.25 mm. The overall size of each µPHP was 60 × 10 × 1.25 mm. Visual observation and temperature measurement of the µPHPs ...

  10. Study of sdO models. Pulsation Analysis

    OpenAIRE

    Rodríguez-López, C.; Moya, A.; Garrido, R.; MacDonald, J; Oreiro, R.; Ulla, A.

    2009-01-01

    We have explored the possibility of driving pulsation modes in models of sdO stars in which the effects of element diffusion, gravitational settling and radiative levitation have been neglected so that the distribution of iron-peak elements remains uniform throughout the evolution. The stability of these models was determined using a non-adiabatic oscillations code. We analysed 27 sdO models from 16 different evolutionary sequences and discovered the first ever sdO models capable of driving h...

  11. Stellar Pulsations and Stellar Evolution: Conflict, Cohabitation, or Symbiosis?

    Science.gov (United States)

    Weiss, Achim

    While the analysis of stellar pulsations allows the determination of current properties of a star, stellar evolution models connect it with its previous history. In many cases results from both methods do not agree. In this review some classical and current cases of disagreement are presented. In some cases these conflicts led to an improvement of the theory of stellar evolution, while in others they still remain unsolved. Some well-known problems of stellar physics are pointed out as well, for which it is hoped that seismology—or in general the analysis of stellar pulsations—will help to resolve them. The limits of this symbiosis will be discussed as well.

  12. DYNAMIC STABILITY OF AXIALLY MOVING VISCOELASTIC BEAMS WITH PULSATING SPEED

    Institute of Scientific and Technical Information of China (English)

    YANG Xiao-dong; CHEN Li-qun

    2005-01-01

    Parametric vibration of an axially moving, elastic, tensioned beam with pulsating speed was investigated in the vicinity of subharmonic and combination resonance. The method of averaging was used to yield a set of autonomous equations when the parametric excitation frequency is twice or the combination of the natural frequencies. Instability boundaries were presented in the plane of parametric frequency and amplitude. The analytical results were numerically verified. The effects of the viscoelastic damping, steady speed and tension on the instability boundaries were numerically demonstrated. It is found that the viscoelastic damping decreases the instability regions and the steady speed and the tension make the instability region drift along the frequency axis.

  13. Modeling KIC10684673 and KIC12216817 as Single Pulsating Variables

    CERN Document Server

    Turner, Garrison

    2016-01-01

    The raw light curves of both KIC 10684673 and KIC 12216817 show variability. Both are listed in the Kepler Eclipsing Binary Catalog (hereafter KEBC), however both are flagged as uncertain in nature. In the present study we show their light curves can be modeled by considering each target as a single, multi-modal delta Scuti pulsator. While this does not exclude the possibility of eclipsing systems, we argue, while spectroscopy on the systems is still lacking, the delta Scuti model is a simpler explanation and therefore more probable.

  14. Carbon Footprint and Order Quantity in Logistics

    Directory of Open Access Journals (Sweden)

    Tian Zhiyong

    2014-05-01

    Full Text Available Purpose: Even without economic factors and government regulations, the pressure and motivation of corporation to reduce emission are still increasing. This is because the key factors for corporation to reduce emissions have become corporate social responsibility and identification of low-carbon value by consumer and society from economic trade-off and government regulations. So, the purpose of this paper is to provide quantity methods for the logistics organizations with wish of voluntary reduction and social responsibility.Design/methodology/approach: Being difference from the traditional research that takes economic value as object, this paper takes carbon footprint as object directly, order quantity as decision variable. By referring to the traditional economic order quantity model, the paper creates logistics carbon footprint model which takes transport and inventory into account. Then it solves the model by calculating the values of order quantity, carbon footprint and revenue using the method of optimization.Findings and Originality/value: By solving and comparing the two models of economic order quantity model and carbon footprint model, it gets some results, such as carbon optimization order quantity, the effects order quantity deviating from economic order quantity or carbon order quantity having on economic or carbon footprint values, which can give some meaningful insight for corporation to search out reduction opportunities by operations adjustment.Originality/value: The study takes carbon footprint as object directly and creates the corresponding quantity model. By comparing with the traditional economic order quantity model, the paper provides quantity methods and obtains some meaningful insights for the logistics organizations with wish of voluntary reduction and social responsibility to reduce emissions by operations adjustment.

  15. Observation of quasi-periodic pulsations in the solar flare SF 900610

    DEFF Research Database (Denmark)

    Terekhov, O.V.; Shevchenko, A.V.; Kuz'min, A.G.;

    2002-01-01

    A quasi-periodic component was found at the maximum of the X-ray light curve for the June 10, 1990 solar flare detected by the Granat observatory. The pulsation period was 143.2 +/- 0.8 s. The intensity of the pulsing component is not constant; the maximum amplitude of the pulsations is similar t...

  16. Single mode rate equations for two sections self-pulsating DFB laser

    Institute of Scientific and Technical Information of China (English)

    王春林; 伍剑; 林金桐

    2003-01-01

    We propose a set of single mode rate equations for multi-section distributed feedback (DFB) lasers. On the basis of the rate equations, the self-pulsation in the two-section DFB lasers with asymmetrical injection current was explained.It was found that the dynamic distribution of the power in two sections play key role in the self-pulsation running.

  17. Time series and correlation of pulsations observed simultaneously by two aircraft

    International Nuclear Information System (INIS)

    Geomagnetic pulsations are an interesting and ubiquitous component of the geomagnetic field and they have been studied extensively for several decades. Numerous comparisons have been made of pulsations at a variety of sites for various objectives. However, conductivity anomalies introduce a number of complexities into the interpretations of pulsations at ground sites through the action of the primary fields on the electrical properties of the local geologic structure. To avoid the difficulties associated with conductivity irregularities, Ochadlick et al. [1985] described an aeromagnetic approach using two aircraft for studying the relationship between pulsations observed over a deep ocean area. Relative to land regions, a deep sea is presumably a more uniform conductor. Using the dual aeromagnetic results, Ochadlick found that the correlation coefficient of pulsations remained relatively constant for observation points spaced apart from a few to about 150 km. Beyond 150 km the correlation coefficient was found to decrease. This letter summarizes the time series records of pulsations, totaling about 9 h, acquired during several dual aircraft flights performed between 20 May and 15 Aug 1985 and presents the associated correlation coefficient between the dual aircraft data sets. Apparently, those measurements show for the first time that a strong similarity of pulsations weakens quickly at a distance of ∼150 km which is remarkably close to the ionospheric height and is thus suggestive of a strong ionospheric control on the spatial coherence of pulsations

  18. Pulsation period variations in the RRc Lyrae star KIC 5520878

    CERN Document Server

    Hippke, Michael; Zee, A; Edmondson, William H; Steven, Ian R; Lindner, John F; Kia, Benham; Ditto, William L

    2014-01-01

    Learned et. al. proposed that a sufficiently advanced extra-terrestrial civilization may tickle Cepheid and RR Lyrae variable stars with a neutrino beam at the right time, thus causing them to trigger early and jogging the otherwise very regular phase of their expansion and contraction. This would turn these stars into beacons to transmit information throughout the galaxy and beyond. The idea is to search for signs of phase modulation (in the regime of short pulse duration) and patterns, which could be indicative of intentional, omnidirectional signaling. We have performed such a search among variable stars using photometric data from the Kepler space telescope. In the RRc Lyrae star KIC 5520878, we have found two such regimes of long and short pulse durations. The sequence of period lengths, expressed as time series data, is strongly auto correlated, with correlation coefficients of prime numbers being significantly higher ($p=99.8$\\%). Our analysis of this candidate star shows that the prime number oddity o...

  19. A SEARCH FOR OB ASSOCIATIONS NEAR SOUTHERN LONG-PERIOD CEPHEIDS. V. AQ PUPPIS AND V620 PUPPIS

    International Nuclear Information System (INIS)

    A photometric UBV survey is presented for 610 stars in a region surrounding the Cepheid AQ Puppis and centered southwest of the variable, based upon photoelectric measures for 14 stars and calibrated iris photometry of photographic plates of the field for 596 stars. An analysis of reddening and distance for program stars indicates that the major dust complex in this direction is ∼1.8 kpc distant, producing differential extinction described by a ratio of total-to-selective extinction of R = AV /EB–V = 3.10 ± 0.20. Zero-age main-sequence fitting for the main group of B-type stars along the line of sight yields a distance of 3.21 ± 0.19 kpc (V0 – MV = 12.53 ± 0.13 s.e.). The 29fd97 Cepheid AQ Pup, of field reddening EB–V = 0.47 ± 0.07 (EB–V(B0) = 0.51 ± 0.07), appears to be associated with B-type stars lying within 5' of it as well as with a sparse group of stars, designated Turner 14, centered south of it at J2000.0 = 07:58:37, –29:25:00, with a mean reddening of EB–V = 0.81 ± 0.01. AQ Pup has an inferred luminosity as a cluster member of (MV ) = –5.40 ± 0.25 and an evolutionary age of 3 × 107 yr. Its observed rate of period increase of +300.1 ± 1.2 s yr–1 is an order of magnitude larger than what is observed for Cepheids of comparable period in the third crossing of the instability strip, and may be indicative of a high rate of mass loss or a putative fifth crossing. Another sparse cluster, designated Turner 13, surrounds the newly recognized 2fd59 Cepheid V620 Pup, of space reddening EB–V = 0.64 ± 0.02 (EB–V(B0) = 0.68 ± 0.02), distance 2.88 ± 0.11 kpc (V0 – MV 12.30 ± 0.08 s.e.), evolutionary age 108 yr, and an inferred luminosity as a likely cluster member of (MV) = –2.74 ± 0.11. V620 Pup is tentatively identified as a first crosser, pending additional observations.

  20. Continuous vs. pulsating flow boiling. Part 2: Statistical comparison using response surface methodology

    DEFF Research Database (Denmark)

    Kærn, Martin Ryhl; Elmegaard, Brian; Meyer, Knud Erik;

    2016-01-01

    -motor expansion valve. Two experimental designs (data point sets) are generated using a modified Central Composite Design for each valve and their response surfaces are compared using the quadratic model. Statistical information on the significant model terms are used to clarify whether the effect of fluid flow......Response surface methodology is used to investigate an active method for flow boiling heat transfer enhancement by means of fluid flow pulsation. The flow pulsations are introduced by a flow modulating expansion device and compared with the baseline continuous flow provided by a stepper...... pulsations is statistically significant in terms of the time-averaged flow boiling heat transfer coefficient. The cycle time range from 1 s to 9 s for the pulsations. The results show that the effect of fluid flow pulsations is statistically significant, disregarding the lowest heat flux measurements...

  1. Nature of Pi1B pulsations as inferred from ground and satellite observations

    Science.gov (United States)

    Lessard, M. R.; Lund, E. J.; Jones, S. L.; Arnoldy, R. L.; Posch, J. L.; Engebretson, M. J.; Hayashi, K.

    2006-07-01

    The occurrence of Pi1B pulsations is well-documented, including the fact that these pulsations can be observed both on the ground and at geosynchronous orbit at substorm onset, although information about their propagation characteristics has been lacking. In this paper, data are presented from FAST, GOES 9 and various ground stations that show the simultaneous observations of Pi1B pulsations in association with an onset. While the data at GOES 9 show that the pulsations are compressional in nature, data from FAST show the presence of shear mode waves, implying that Pi1B mode conversion of some type must take place in the region between geosynchronous orbit and FAST altitudes. An additional point is that Pi1B pulsations apparently propagate through auroral phenomena routinely, begging the question of what role they may play.

  2. High frequency A-type pulsators discovered using SuperWASP

    CERN Document Server

    Holdsworth, Daniel L; Gillon, M; Clubb, K I; Southworth, J; Maxted, P F L; Anderson, D R; Barros, S C C; Cameron, A Collier; Delrez, L; Faedi, F; Haswell, C A; Hellier, C; Horne, K; Jehin, E; Norton, A J; Pollacco, D; Skillen, I; Smith, A M S; West, R G; Wheatley, P J

    2014-01-01

    We present the results of a survey using the WASP archive to search for high frequency pulsations in F-, A- and B-type stars. Over 1.5 million targets have been searched for pulsations with amplitudes greater than 0.5 millimagnitude. We identify over 350 stars which pulsate with periods less than 30 min. Spectroscopic follow-up of selected targets has enabled us to confirm 10 new rapidly oscillating Ap stars, 13 pulsating Am stars and the fastest known $\\delta$ Scuti star. We also observe stars which show pulsations in both the high-frequency domain and in the low-frequency $\\delta$ Scuti range. This work shows the power of the WASP photometric survey to find variable stars with amplitudes well below the nominal photometric precision per observation.

  3. V2653 Ophiuchii with a pulsating component and Ppuls - Porb, Ppuls - g correlations for γ Dor type pulsators

    Science.gov (United States)

    Çakırlı, Ö.; Ibanoglu, C.

    2016-05-01

    We present new spectroscopic observations of the double-lined eclipsing binary V2653 Ophiuchii. The photometric observations obtained by ASAS were analyzed and combined with the analysis of radial velocities for deriving the absolute parameters of the components. Masses and radii were determined for the first time as Mp = 1.537 ± 0.021 M⊙ and Rp = 2.215 ± 0.055 R⊙, Ms = 1.273 ± 0.019 M⊙ and Rs = 2.000 ± 0.056 R⊙ for the components of V2653 Oph. We estimate an interstellar reddening of 0.15 ± 0.08 mag and a distance of 300 ± 50 pc for the system, both supporting the membership of the open cluster Collinder 359. Using the out-of-eclipse photometric data we have made frequency analysis and detected a periodic signal at 1.0029 ± 0.0019 c/d. This frequency and the location of the more massive star on the HR diagram lead to classification of a γ Dor type variable. Up to date only eleven γ Dor type pulsators in the eclipsing binaries have been discovered. For six out of 11 systems, the physical parameters were determined. Although a small sample, we find empirical relations that Ppuls ∝ Porb0.43 and Ppuls ∝ g-0.83. While the pulsation periods increase with longer orbital periods, they decrease with increasing surface gravities of pulsating components and gravitational pull exerted by the companions. We present, briefly, the underlying physics behind the correlations we derived.

  4. 16 CFR 500.19 - Conversion of SI metric quantities to inch/pound quantities and inch/pound quantities to SI...

    Science.gov (United States)

    2010-01-01

    ... 16 Commercial Practices 1 2010-01-01 2010-01-01 false Conversion of SI metric quantities to inch/pound quantities and inch/pound quantities to SI metric quantities. 500.19 Section 500.19 Commercial... LABELING ACT § 500.19 Conversion of SI metric quantities to inch/pound quantities and inch/pound...

  5. Ventricular dilation and elevated aqueductal pulsations in a new experimental model of communicating hydrocephalus

    Energy Technology Data Exchange (ETDEWEB)

    Wagshul, M.; Smith, S.; Wagshul, M.; McAllister, J.P.; Rashid, S.; Li, J.; Egnor, M.R.; Walker, M.L.; Yu, M.; Smith, S.D.; Zhang, G.; Chen, J.J.; Beneveniste, H.

    2009-03-01

    In communicating hydrocephalus (CH), explanations for the symptoms and clear-cut effective treatments remain elusive. Pulsatile flow through the cerebral aqueduct is often significantly elevated, but a clear link between abnormal pulsations and ventriculomegaly has yet to be identified. We sought to demonstrate measurement of pulsatile aqueductal flow of CSF in the rat, and to characterize the temporal changes in CSF pulsations in a new model of CH. Hydrocephalus was induced by injection of kaolin into the basal cisterns of adult rats (n = 18). Ventricular volume and aqueductal pulsations were measured on a 9.4 T MRI over a one month period. Half of the animals developed ventricular dilation, with increased ventricular volume and pulsations as early as one day post-induction, and marked chronic elevations compared to intact controls (volume: 130.15 {+-} 83.21 {mu}l vs. 15.52 {+-} 2.00 {mu}l; pulsations: 114.51 nl {+-} 106.29 vs. 0.72 {+-} 0.13 nl). Similar to the clinical presentation, the relationship between ventricular size and pulsations was quite variable. However, the pulsation time-course revealed two distinct sub-types of hydrocephalic animals: those with markedly elevated pulsations which persisted over time, and those with mildly elevated pulsations which returned to near normal levels after one week. These groups were associated with severe and mild ventriculomegaly respectively. Thus, aqueductal flow can be measured in the rat using high-field MRI and basal cistern-induced CH is associated with an immediate change in CSF pulsatility. At the same time, our results highlight the complex nature of aqueductal pulsation and its relationship to ventricular dilation.

  6. $\\gamma$ Doradus Pulsations in the Eclipsing Binary Star KIC 6048106

    CERN Document Server

    Lee, Jae Woo

    2016-01-01

    We present the ${\\it Kepler}$ photometry of KIC 6048106 exhibiting O'Connell effect and multiperiodic pulsations. Including a starspot on either of the components, light-curve synthesis indicates that this system is a semi-detached Algol with a mass ratio of 0.211, an orbital inclination of 73.9 deg, and a large temperature difference of 2,534 K. To examine in detail both spot variations and pulsations, we separately analyzed the {\\it Kepler} time-series data at the interval of an orbital period by an iterative way. The results reveal that the variable asymmetries of the light maxima can be interpreted as the changes of a magnetic cool spot on the secondary component with time. Multiple frequency analyses were performed in the outside-eclipse light residuals after removal of the binarity effects from the observed {\\it Kepler} data. We detected 30 frequencies with signal to noise amplitude ratios larger than 4.0, of which six ($f_2$--$f_6$ and $f_{10}$) can be identified as high-order (17 $\\le n \\le$ 25) low-d...

  7. Tidally Induced Pulsations in Kepler Eclipsing Binary KIC 3230227

    CERN Document Server

    Guo, Zhao; Fuller, Jim

    2016-01-01

    KIC 3230227 is a short period ($P\\approx 7.0$ days) eclipsing binary with a very eccentric orbit ($e=0.6$). From combined analysis of radial velocities and {\\it Kepler} light curves, this system is found to be composed of two A-type stars, with masses of $M_1=1.84\\pm 0.18M_{\\odot}$, $M_2=1.73\\pm 0.17M_{\\odot}$ and radii of $R_1=2.01\\pm 0.09R_{\\odot}$, $R_2=1.68\\pm 0.08 R_{\\odot}$ for the primary and secondary, respectively. In addition to an eclipse, the binary light curve shows a brightening and dimming near periastron, making this a somewhat rare eclipsing heartbeat star system. After removing the binary light curve model, more than ten pulsational frequencies are present in the Fourier spectrum of the residuals, and most of them are integer multiples of the orbital frequency. These pulsations are tidally driven, and both the amplitudes and phases are in agreement with predictions from linear tidal theory for $l=2, m=-2$ prograde modes.

  8. An Experimental Investigation of Micro Pulsating Heat Pipes

    Directory of Open Access Journals (Sweden)

    Kai-Shing Yang

    2014-06-01

    Full Text Available Two Si-based micro pulsating heat pipes (µPHPs charged using HFE-7100 were either horizontally or vertically oriented and were tested using several heating powers. The width of each channel was 0.8 mm in one µPHP containing uniform channels, and the channel width was 1.0 mm or 0.6 mm in the other µPHP, which did not contain uniform channels. The depth of each channel was 0.25 mm. The overall size of each µPHP was 60 × 10 × 1.25 mm. Visual observation and temperature measurement of the µPHPs under various conditions were performed and the results were analyzed. The results indicated that when the µPHPs were operated horizontally at a heating power ranging from 1 to 7 W, the pulsating two-phase flow in the channels of the µPHPs could not begin, except when the µPHP containing nonuniform channels was tested at a heating power of 7 W. With a heating power less than 5 W, the frequency of the sine-like oscillating displacement of the vapor slug increased and the displacement of the vapor slug reduced in either vertically oriented μPHP, as the heating power increased With a heating power higher than 5 W, periodic “start-stop” behaviors were observed in the vertical μPHP containing nonuniform channels.

  9. Closed loop pulsating heat pipes. Part A: parametric experimental investigations

    Energy Technology Data Exchange (ETDEWEB)

    Charoensawan, P.; Terdtoon, P. [Chiang Mai University (Thailand). Department of Mechanical Engineering; Khandekar, S.; Groll, M. [Universitat Stuttgart (Germany). Institut fur Kernenergetik und Energiesysteme

    2003-11-01

    Closed loop pulsating heat pipes (CLPHPs) are complex heat transfer devices having a strong thermo-hydrodynamic coupling governing the thermal performance. In this paper, a wide range of pulsating heat pipes is experimentally studied thereby providing vital information on the parameter dependency of their thermal performance. The influence characterization has been done for the variation of internal diameters, number of turns, working fluid and inclination angle (from vertical bottom heat mode to horizontal orientation mode) of the device. CLPHPs are made of copper tubes of internal diameters 2.0 and 1.0 mm, heated by constant temperature water bath and cooled by constant temperature water-ethylene glycol mixture (50% each by volume). The number of turns in the evaporator is varied from 5 to 23. The working fluids employed are water, ethanol and R-123. The results indicate a strong influence of gravity and number of turns on the performance. The thermophysical properties of working fluids affect the performance which also strongly depends on the boundary conditions of PHP operation. Part B of this paper, which deals with development of semi-empirical correlations to fit the data reported here coupled with some critical visualization results, will appear separately. (author)

  10. Studies of the Long Secondary Periods in Pulsating Red Giants

    CERN Document Server

    Percy, John R

    2016-01-01

    We have used systematic, sustained visual observations from the AAVSO International Database, and the AAVSO time-series analysis package VSTAR to study the unexplained "long secondary periods" (LSPs) in 27 pulsating red giants. In our sample, the LSPs range from 479 to 2967 days, and are on average 8.1 +/- 1.3 times the pulsation period. There is no evidence for more than one LSP in each star. In stars with both the fundamental and first overtone radial period present, the LSP is more often about 10 times the latter. The visual amplitudes of the LSPs are typically 0.1 magnitude and do not correlate with the LSP. The phase curves tend to be sinusoidal, but at least two are sawtooth. The LSPs are stable, within their errors, over the timespan of our data, which is typically 25,000 days. The amplitudes, however, vary by up to a factor of two or more on a timescale of roughly 20-30 LSPs. There is no obvious difference between the behavior of the carbon (C) stars and the normal oxygen (M) stars. Previous multicolo...

  11. Pulsations in Hydrogen Burning Low Mass Helium White Dwarfs

    CERN Document Server

    Steinfadt, Justin D R; Arras, Phil

    2010-01-01

    Helium core white dwarfs (WDs) with mass M < 0.20 M_sun undergo several Gyrs of stable hydrogen burning as they evolve. We show that in a certain range of WD and hydrogen envelope masses, these WDs may exhibit g-mode pulsations similar to their passively cooling, more massive carbon/oxygen core counterparts, the ZZ Cetis. Our models with stably burning hydrogen envelopes on helium cores yield g-mode periods and period spacings longer than the canonical ZZ Cetis by nearly a factor of two. We show that core composition and structure can be probed using seismology since the g-mode eigenfunctions predominantly reside in the helium core. Though we have not carried out a fully nonadiabatic stability analysis, the scaling of the thermal time in the convective zone with surface gravity highlights several low mass helium WDs that should be observed in search of pulsations: NLTT 11748, SDSS J0822+2753, and the companion to PSR J1012+5307. Seismological studies of these He core WDs may prove especially fruitful, as t...

  12. Axions and the pulsation periods of variable white dwarfs revisited

    CERN Document Server

    Isern, J; Althaus, L G; Córsico, A H

    2010-01-01

    Axions are the natural consequence of the introduction of the Peccei-Quinn symmetry to solve the strong CP problem. All the efforts to detect such elusive particles have failed up to now. Nevertheless, it has been recently shown that the luminosity function of white dwarfs is best fitted if axions with a mass of a few meV are included in the evolutionary calculations. Our aim is to show that variable white dwarfs can provide additional and independent evidence about the existence of axions. The evolution of a white dwarf is a slow cooling process that translates into a secular increase of the pulsation periods of some variable white dwarfs, the so-called DAV and DBV types. Since axions can freely escape from such stars, their existence would increase the cooling rate and, consequently, the rate of change of the periods as compared with the standard ones. The present values of the rate of change of the pulsation period of G117-B15A are compatible with the existence of axions with the masses suggested by the lu...

  13. Eclipsing binaries with pulsating components: CoRoT 102918586

    CERN Document Server

    Maceroni, C; Damiani, C; Gandolfi, D; Debosscher, J; Hatzes, A; Guenther, E W; Aerts, C

    2010-01-01

    We present the preliminary results of the study of an interesting target in the first CoRoT exo-planet field (IRa1): CoRoT 102918586. Its light curve presents additional variability on the top of the eclipses, whose pattern suggests multi- frequency pulsations. The high accuracy CoRoT light curve was analyzed by applying an iterative scheme, devised to disentangle the effect of eclipses from the oscillatory pattern. In addition to the CoRoT photometry we obtained low resolution spectroscopy with the AAOmega multi-fiber facility at the Anglo Australian Observatory, which yielded a spectral classification as F0 V and allowed us to infer a value of the primary star effective temperature. The Fourier analysis of the residuals, after subtraction of the binary light curve, gave 35 clear frequencies. The highest amplitude frequency, of 1.22 c/d, is in the expected range for both \\gamma Dor and SPB pulsators, but the spectral classification favors the first hypothesis. Apart from a few multiples of the orbital period...

  14. Numerical simulation of pressure pulsations in Francis turbines

    Science.gov (United States)

    Magnoli, M. V.; Schilling, R.

    2012-11-01

    In the last decades, hydraulic turbines have experienced the increase of their power density and the extension of their operating range, leading the fluid and mechanical dynamic effects to become significantly more pronounced. The understanding of the transient fluid flow and of the associated unsteady effects is essential for the reduction of the pressure pulsation level and improvement of the machine dynamic behaviour. In this study, the instationary fluid flow through the complete turbine was numerically calculated for an existing Francis machine with high specific speed. The hybrid turbulence models DES (detached eddy simulation) and SAS (scale adaptive simulation) allowed the accurate simulation of complex dynamic flow effects, such as the rotor-stator-interaction and the draft tube instabilities. Different operating conditions, as full load, part load, higher part load and deep part load, were successfully simulated and showed very tight agreement with the experimental results from the model tests. The transient pressure field history, obtained from the CFD (computational fluid dynamics) simulation and stored for each time step, was used as input for the full instationary FEA (finite element analysis) of turbine components. The assessment of the machine dynamic motion also offered the possibility to contribute to the understanding of the pressure pulsation effects and to further increase the turbine stability. This research project was developed at the Institute of Fluid Mechanics of the TU München.

  15. Pressure pulsation in roller pumps: a validated lumped parameter model.

    Science.gov (United States)

    Moscato, Francesco; Colacino, Francesco M; Arabia, Maurizio; Danieli, Guido A

    2008-11-01

    During open-heart surgery roller pumps are often used to keep the circulation of blood through the patient body. They present numerous key features, but they suffer from several limitations: (a) they normally deliver uncontrolled pulsatile inlet and outlet pressure; (b) blood damage appears to be more than that encountered with centrifugal pumps. A lumped parameter mathematical model of a roller pump (Sarns 7000, Terumo CVS, Ann Arbor, MI, USA) was developed to dynamically simulate pressures at the pump inlet and outlet in order to clarify the uncontrolled pulsation mechanism. Inlet and outlet pressures obtained by the mathematical model have been compared with those measured in various operating conditions: different rollers' rotating speed, different tube occlusion rates, and different clamping degree at the pump inlet and outlet. Model results agree with measured pressure waveforms, whose oscillations are generated by the tube compression/release mechanism during the rollers' engaging and disengaging phases. Average Euclidean Error (AEE) was 20mmHg and 33mmHg for inlet and outlet pressure estimates, respectively. The normalized AEE never exceeded 0.16. The developed model can be exploited for designing roller pumps with improved performances aimed at reducing the undesired pressure pulsation.

  16. New conserved quantity for the Kerr solution

    International Nuclear Information System (INIS)

    A conformal Killing vector field on the manifold S of trajectories of the timelike Killing vector in the Kerr solution is presented. It is shown that the new field leads to a conserved quantity along certain null geodesics. The nature of the conserved quantity is discussed

  17. Pressure pulsation characteristics and its impact on flow-induced noise in mixed-flow pump%混流泵压力脉动特性及其对流动诱导噪声的影响

    Institute of Scientific and Technical Information of China (English)

    郑源; 陈宇杰; 毛秀丽; 王惠芝; 施伟; 阚阚; 张玉全

    2015-01-01

    As a kind of pump with low head and large capacity, the mixed-flow pump is widely used in large quantities of fields including water conservancy and sewage system of municipal works and so on. The pressure pulsation and flow-induced noise of pump have become two of the most important issues which have negative effect on reliability. The pressure pulsation is the interior performance of the unsteady flow in the pump and the flow-induced noise and vibration are the exterior performance of the unsteady flow in the pump. In order to study the rules of pressure pulsation and flow-induced noise change under different flow rate conditions in a mixed-flow pump and to find the relationship between pressure pulsation and flow-induced noise, the flow field and sound field were numerical simulated. This paper used the PRO/E software to build the pump model and to use the ICEM CFD to conduct the mesh division of the calculated domain. The mixed-flow pump mainly consisted of inlet pipe, impeller, volute and discharge pipe. The unsteady flow was numerical simulated based on RANS solver and SST turbulence model. During the unsteady simulation, the mixed-flow pump rotated for 18 cycles so as to improve the simulation stability. The simulation results of the last 2 periods were used to analyze the time domain characteristics and frequency domain characteristics of pressure pulsation in the pump. And by using the pressure pulsation on the blade as noise source, acoustic Boundary Element Method (BEM) was applied to simulate the flow-induced noise of the mixed-flow pump. The simulation results show that the pressure pulsation amplitude decreases from shroud to hub both at the inlet and outlet of the impeller, and the maximum pressure pulsation appears at the inlet of impeller. So it is crucial to conduct some optimal design for the shroud location in order to weaken the pressure pulsation. Along the circumferential direction in the volute, the pressure pulsation amplitude appears to be

  18. The panchromatic view of the Magellanic Clouds from Classical Cepheids. I. Distance, Reddening and Geometry of the Large Magellanic Cloud disk

    CERN Document Server

    Inno, L; Matsunaga, N; Fiorentino, G; Marconi, M; Lemasle, B; da Silva, R; Soszyński, I; Udalski, A; Romaniello, M; Rix, H -W

    2016-01-01

    We present a detailed investigation of the Large Magellanic Cloud (LMC) disk using classical Cepheids. Our analysis is based on optical (I,V; OGLE-IV), near-infrared (NIR: J,H,Ks) and mid-infrared (MIR: w1; WISE) mean magnitudes. By adopting new templates to estimate the NIR mean magnitudes from single-epoch measurements, we build the currently most accurate, largest and homogeneous multi-band dataset of LMC Cepheids. We determine Cepheid individual distances using optical and NIR Period-Wesenheit relations (PWRs), to measure the geometry of the LMC disk and its viewing angles. Cepheid distances based on optical PWRs are precise at 3%, but accurate to 7, while the ones based on NIR PWRs are more accurate (to 3%), but less precise (2%-15%), given the higher photometric error on the observed magnitudes. We found an inclination i=25.05 $\\pm$ 0.02 (stat.) $\\pm$ 0.55 (syst.) deg, and a position angle of the lines of nodes P.A.=150.76 $\\pm$ 0.02(stat.) $\\pm$ 0.07(syst.) deg. These values agree well with estimates b...

  19. The Extragalactic Distance Scale Key Project VIII. The Discovery of Cepheids and a New Distance to NGC 3621 Using the Hubble Space Telescope

    Science.gov (United States)

    Rawson, D. M.; Mould, J. R.; Macri, L. M.; Huchra, J. P.; Kennicutt, R. C.; Harding, P.; Freedman, W. L.; Hill, R. J.; Phelps, R. L.; Madore, B. F.; Silbermann, N. A.; Graham, J. A.; Ferrarese, L.; Ford, H. C.; Illingworth, G. D.; Hoessel, J. G.; Han, M.; Hughes, S. M.; Saha, A.; Stetson, P. B.

    1996-01-01

    We report on the discovery of Cepheids in the field spiral galaxy NGC3621, based on observations made with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope (HST). NGC 3621 is one of 18 galaxies observed as part of the HST Key Project on the Extragalctic Distance Scale, which aims to measure the Hubble Constant to 10 percent accuracy.

  20. Optical Identification of Cepheids in 19 Host Galaxies of Type Ia Supernovae and NGC 4258 with the Hubble Space Telescope

    Science.gov (United States)

    Hoffmann, Samantha L.; Macri, Lucas M.; Riess, Adam G.; Yuan, Wenlong; Casertano, Stefano; Foley, Ryan J.; Filippenko, Alexei V.; Tucker, Brad E.; Chornock, Ryan; Silverman, Jeffrey M.; Welch, Douglas L.; Goobar, Ariel; Amanullah, Rahman

    2016-10-01

    We present results of an optical search conducted as part of the SH0ES project (Supernovae and H0 for the Equation of State of dark energy) for Cepheid variable stars using the Hubble Space Telescope (HST) in 19 hosts of Type Ia supernovae (SNe Ia) and the maser-host galaxy NGC 4258. The targets include nine newly imaged SN Ia hosts using a novel strategy based on a long-pass filter that minimizes the number of HST orbits required to detect and accurately determine Cepheid properties. We carried out a homogeneous reduction and analysis of all observations, including new universal variability searches in all SN Ia hosts, which yielded a total of 2200 variables with well-defined selection criteria, the largest such sample identified outside the Local Group. These objects are used in a companion paper to determine the local value of H0 with a total uncertainty of 2.4%. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

  1. The Araucaria Project. The Distance to the Local Group Galaxy IC 1613 from Near-Infrared Photometry of Cepheid Variables

    CERN Document Server

    Pietrzynski, G; Bresolin, F; Dall'Ora, M; Gieren, W; Kudritzki, R P; Soszynski, I; Storm, J

    2006-01-01

    We have measured accurate near-infrared magnitudes in the J and K bands of 39 Cepheid variables in IC 1613 with well-determined periods and optical VI light curves. Using the template light curve approach of Soszy{\\'n}ski, Gieren and Pietrzy{\\'n}ski, accurate mean magnitudes were obtained from these data which allowed to determine the distance to IC 1613 relative to the LMC from a multiwavelength period-luminosity solution in the optical VI and near-IR JK bands, with an unprecedented accuracy. Our result for the IC 1613 distance is $(m-M)_{0} = 24.291 \\pm 0.014$ (random error) mag, with an additional systematic uncertainty smaller than 2%. From our multiwavelength approach, we find for the total (average) reddening to the IC 1613 Cepheids $E(B-V) = 0.090 \\pm 0.007$ mag,which is significantly higher than the foreground reddening of about 0.03 mag,showing the presence of appreciable dust extinction inside the galaxy. Our data suggest that the extinction law in IC 1613 is very similar to the galactic one.Our dis...

  2. Thermal quantities of {sup 46}Ti

    Energy Technology Data Exchange (ETDEWEB)

    Rahmatinejad, A. [Department of Physics, Faculty of Science, University of Zanjan, Zanjan (Iran, Islamic Republic of); Razavi, R., E-mail: rrazavin@ihu.ac.ir [Physics Department, Faculty of Science, Imam Hossein Comprehensive University, Tehran (Iran, Islamic Republic of); Kakavand, T. [Department of Physics, Faculty of Science, Imam Khomeini International University, Qazvin (Iran, Islamic Republic of)

    2015-07-15

    Thermodynamic quantities of {sup 46}Ti have been calculated in the framework of the BCS model with inclusion of modified nuclear pairing gap (MPBCS) that was proposed in our previous publication. Using modified paring gap results in an S-shaped heat capacity curve at critical temperature with a smooth behavior instead of singular behavior of the same curve in the BCS calculations. In addition the thermal quantities have been extracted within the framework of a canonical ensemble according to the new experimental data on nuclear level densities measured by the Oslo group. Comparison shows a good agreement between our calculations in MPBCS and the extracted quantities in the canonical ensemble framework.

  3. Coupled pulsating and cellular structure in the propagation of globally planar detonations in free space

    Energy Technology Data Exchange (ETDEWEB)

    Han, Wenhu [Center for Combustion Energy, Tsinghua University, Beijing 100084 (China); Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084 (China); Gao, Yang, E-mail: gaoyang-00@mails.tsinghua.edu.cn [Center for Combustion Energy, Tsinghua University, Beijing 100084 (China); Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084 (China); Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Wang, Cheng [Beijing Institute of Technology, Beijing 100081 (China); Law, Chung K. [Center for Combustion Energy, Tsinghua University, Beijing 100084 (China); Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 (United States)

    2015-10-15

    The globally planar detonation in free space is numerically simulated, with particular interest to understand and quantify the emergence and evolution of the one-dimensional pulsating instability and the two-dimensional cellular structure which is inherently also affected by pulsating instability. It is found that the pulsation includes three stages: rapid decay of the overdrive, approach to the Chapman-Jouguet state and emergence of weak pulsations, and the formation of strong pulsations; while evolution of the cellular structure also exhibits distinct behavior at these three stages: no cell formation, formation of small-scale, irregular cells, and formation of regular cells of a larger scale. Furthermore, the average shock pressure in the detonation front consists of fine-scale oscillations reflecting the collision dynamics of the triple-shock structure and large-scale oscillations affected by the global pulsation. The common stages of evolution between the cellular structure and the pulsating behavior, as well as the existence of shock-front pressure oscillation, suggest highly correlated mechanisms between them. Detonations with period doubling, period quadrupling, and chaotic amplitudes were also observed and studied for progressively increasing activation energies.

  4. 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...

  5. Coupled pulsating and cellular structure in the propagation of globally planar detonations in free space

    International Nuclear Information System (INIS)

    The globally planar detonation in free space is numerically simulated, with particular interest to understand and quantify the emergence and evolution of the one-dimensional pulsating instability and the two-dimensional cellular structure which is inherently also affected by pulsating instability. It is found that the pulsation includes three stages: rapid decay of the overdrive, approach to the Chapman-Jouguet state and emergence of weak pulsations, and the formation of strong pulsations; while evolution of the cellular structure also exhibits distinct behavior at these three stages: no cell formation, formation of small-scale, irregular cells, and formation of regular cells of a larger scale. Furthermore, the average shock pressure in the detonation front consists of fine-scale oscillations reflecting the collision dynamics of the triple-shock structure and large-scale oscillations affected by the global pulsation. The common stages of evolution between the cellular structure and the pulsating behavior, as well as the existence of shock-front pressure oscillation, suggest highly correlated mechanisms between them. Detonations with period doubling, period quadrupling, and chaotic amplitudes were also observed and studied for progressively increasing activation energies

  6. GW Librae: a unique laboratory for pulsations in an accreting white dwarf

    Science.gov (United States)

    Toloza, O.; Gänsicke, B. T.; Hermes, J. J.; Townsley, D. M.; Schreiber, M. R.; Szkody, P.; Pala, A.; Beuermann, K.; Bildsten, L.; Breedt, E.; Cook, M.; Godon, P.; Henden, A. A.; Hubeny, I.; Knigge, C.; Long, K. S.; Marsh, T. R.; de Martino, D.; Mukadam, A. S.; Myers, G.; Nelson, P.; Oksanen, A.; Patterson, J.; Sion, E. M.; Zorotovic, M.

    2016-07-01

    Non-radial pulsations have been identified in a number of accreting white dwarfs in cataclysmic variables. These stars offer insight into the excitation of pulsation modes in atmospheres with mixed compositions of hydrogen, helium, and metals, and the response of these modes to changes in the white dwarf temperature. Among all pulsating cataclysmic variable white dwarfs, GW Librae stands out by having a well-established observational record of three independent pulsation modes that disappeared when the white dwarf temperature rose dramatically following its 2007 accretion outburst. Our analysis of Hubble Space Telescope (HST) ultraviolet spectroscopy taken in 2002, 2010, and 2011, showed that pulsations produce variations in the white dwarf effective temperature as predicted by theory. Additionally in 2013 May, we obtained new HST/Cosmic Origin Spectrograph ultraviolet observations that displayed unexpected behaviour: besides showing variability at ≃275 s, which is close to the post-outburst pulsations detected with HST in 2010 and 2011, the white dwarf exhibits high-amplitude variability on an ≃4.4 h time-scale. We demonstrate that this variability is produced by an increase of the temperature of a region on white dwarf covering up to ≃30 per cent of the visible white dwarf surface. We argue against a short-lived accretion episode as the explanation of such heating, and discuss this event in the context of non-radial pulsations on a rapidly rotating star.

  7. Ultra-fast magnetic resonance encephalography of physiological brain activity - Glymphatic pulsation mechanisms?

    Science.gov (United States)

    Kiviniemi, Vesa; Wang, Xindi; Korhonen, Vesa; Keinänen, Tuija; Tuovinen, Timo; Autio, Joonas; LeVan, Pierre; Keilholz, Shella; Zang, Yu-Feng; Hennig, Jürgen; Nedergaard, Maiken

    2016-06-01

    The theory on the glymphatic convection mechanism of cerebrospinal fluid holds that cardiac pulsations in part pump cerebrospinal fluid from the peri-arterial spaces through the extracellular tissue into the peri-venous spaces facilitated by aquaporin water channels. Since cardiac pulses cannot be the sole mechanism of glymphatic propulsion, we searched for additional cerebrospinal fluid pulsations in the human brain with ultra-fast magnetic resonance encephalography. We detected three types of physiological mechanisms affecting cerebral cerebrospinal fluid pulsations: cardiac, respiratory, and very low frequency pulsations. The cardiac pulsations induce a negative magnetic resonance encephalography signal change in peri-arterial regions that extends centrifugally and covers the brain in ≈1 Hz cycles. The respiratory ≈0.3 Hz pulsations are centripetal periodical pulses that occur dominantly in peri-venous areas. The third type of pulsation was very low frequency (VLF 0.001-0.023 Hz) and low frequency (LF 0.023-0.73 Hz) waves that both propagate with unique spatiotemporal patterns. Our findings using critically sampled magnetic resonance encephalography open a new view into cerebral fluid dynamics. Since glymphatic system failure may precede protein accumulations in diseases such as Alzheimer's dementia, this methodological advance offers a novel approach to image brain fluid dynamics that potentially can enable early detection and intervention in neurodegenerative diseases. PMID:26690495

  8. Propagation and source of Pc5 frequency range pulsation at cusp latitude

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Two induction magnetometers have been installed at Chinese Zhongshan Station and Australia Davis Station, Antarctica respectively. We adopt the cross-spectral analysis technique to analyze the data of the two induction magnetometers, in June, September, December 1996 and March 1997, and to investigate Pc5 frequency range pulsation (150 600 s) occurrence and propagation in cusp latitude. The results are summarized as follows: At Zhongshan-Davis Station, the magnetic pulsations in Pc5 frequency band can occurs over a wide time, but more frequently at pre local magnetic noon and pre local magnetic midnight. The Pc5 pulsations have no significant seasonal variation in the amplitude, occurrence and propagation. The amplitude has a small peak at pre local magnetic noon and large value sometimes at pre local magnetic midnight. In daytime, the Pc5 pulsations propagate westward in morning and eastward in afternoon, and reversal at local magnetic noon. In nighttime, the Pc5 pulsations propagate westward before 20:00 MLT and eastward after 20:00 MLT. Near dusk time, the Pc5 pulsations propagate irregularly. These characteristics indicate that the Pc5 pulsations have different source at different local magnetic time.

  9. Coupled pulsating and cellular structure in the propagation of globally planar detonations in free space

    Science.gov (United States)

    Han, Wenhu; Gao, Yang; Wang, Cheng; Law, Chung K.

    2015-10-01

    The globally planar detonation in free space is numerically simulated, with particular interest to understand and quantify the emergence and evolution of the one-dimensional pulsating instability and the two-dimensional cellular structure which is inherently also affected by pulsating instability. It is found that the pulsation includes three stages: rapid decay of the overdrive, approach to the Chapman-Jouguet state and emergence of weak pulsations, and the formation of strong pulsations; while evolution of the cellular structure also exhibits distinct behavior at these three stages: no cell formation, formation of small-scale, irregular cells, and formation of regular cells of a larger scale. Furthermore, the average shock pressure in the detonation front consists of fine-scale oscillations reflecting the collision dynamics of the triple-shock structure and large-scale oscillations affected by the global pulsation. The common stages of evolution between the cellular structure and the pulsating behavior, as well as the existence of shock-front pressure oscillation, suggest highly correlated mechanisms between them. Detonations with period doubling, period quadrupling, and chaotic amplitudes were also observed and studied for progressively increasing activation energies.

  10. Discovery of new roAp pulsators in the UVES survey of cool magnetic Ap stars

    CERN Document Server

    Kochukhov, O; Ryabchikova, T; Boyko, S; Cunha, M; Tsymbal, V; Weiss, W

    2013-01-01

    We have carried out a survey of short-period pulsations among a sample of carefully chosen cool Ap stars using time-resolved observations with the UVES spectrometer at the ESO 8-m VLT telescope. Here we report the discovery of pulsations with amplitudes 50-100 m/s and periods 7-12 min in HD132205, HD148593 and HD151860. These objects are therefore established as new rapidly oscillating Ap (roAp) stars. In addition, we independently confirm the presence of pulsations in HD69013, HD96237 and HD143487 and detect, for the first time, radial velocity oscillations in two previously known photometric roAp stars HD119027 and HD185256. At the same time, no pulsation variability is found for HD5823, HD178892 and HD185204. All of the newly discovered roAp stars were previously classified as non-pulsating based on the low-precision ground-based photometric surveys. This shows that such observations cannot be used to reliably distinguish between pulsating and non-pulsating stars and that all cool Ap stars may harbor p-mod...

  11. Peculiar variations of white dwarf pulsation frequencies and maestro

    Science.gov (United States)

    Dalessio, James Ruland

    In Part I we report on variations of the normal mode frequencies of the pulsating DB white dwarfs EC 20058-5234 and KIC 8626021 and the pulsating DA white dwarf GD 66. The observations of EC 20058-5234 and KIC 8626021 were motivated by the possibility of measuring the plasmon neutrino production rate of a white dwarf, while the observations of GD 66 were part of a white dwarf pulsation timing based planet search. We announce the discovery of periodic and quasi-periodic variations of multiple normal mode frequencies that cannot be due to the presence of planetary companions. We note the possible signature of a planetary companion to EC 20058-5234 and show that GD 66 cannot have a planet in a several AU orbit down to half a Jupiter mass. We also announce the discovery of secular variations of the normal mode frequencies of all three stars that are inconsistent with cooling alone. Importantly, the rates of period change of several modes of KIC 8626021 are consistent with evolutionary cooling, but are not yet statistically significant. These modes offer the best possibility of measuring the neutrino production rate in a white dwarf. We also observe periodic and secular variations in the frequency of a combination mode that exactly matches the variations predicted by the parent modes, strong observational evidence that combination modes are created by the convection zone and are not normal modes. Periodic variations in the amplitudes of many of these modes is also noted. We hypothesize that these frequency variations are caused by complex variations of the magnetic field strength and geometry, analogous to behavior observed in the Sun. In Part II we describe the MAESTRO software framework and the MAESTRO REDUCE algorithm. MAESTRO is a collection of astronomy specific MatLab software developed by the Whole Earth Telescope. REDUCE is an an algorithm that can extract the brightness of stars on a set of CCD images with minimal configuration and human interaction. The key to

  12. Pulsating flow performance of a turbocharger compressor for automotive application

    International Nuclear Information System (INIS)

    Highlights: • The behavior of a turbocharger for automotive application was studied. • A broad experimental activity was developed under steady and unsteady flow. • Compressor performance was analyzed under unsteady flow. • Compressor unsteady flow performance deviates from the corresponding steady state. • The surge line position proved to be affected by unsteady flow operation. -- Abstract: Downsizing with turbocharging is the most promising way, especially in terms of cost, to get reduced fuel consumption and CO2 emissions particularly in the case of Spark Ignition engines. In automotive applications the turbocharger turbine usually operates under heavy unsteady flow conditions due to the opening and closing of engine valves. However, in the case of extremely downsized engines with a reduced number of cylinders and a small intake circuit volume also the compressor performance can be affected by the unsteady flow generated by the engine intake valves. To make simulation models able to accurately predict engine performance, a better understanding of compressor and turbine pulsating flow performance can be accomplished through measurements performed on specialized test facilities, using suitable measuring equipment. As regards the turbocharger compressor, the surge line position under pulsating flow conditions is another important aspect to be considered. In the paper the results of a broad experimental investigation performed on a small turbocharger compressor matched to a downsized gasoline engine are presented. Measurements were developed on the test facility operating at the University of Genoa, which allows investigations on automotive turbochargers both under steady and unsteady flow conditions. Tested turbocharger compressor was coupled to the automotive engine intake circuit and the pulsating flow was generated by a motor-driven cylinder head fitted with a variable valve actuation system. Different levels of turbocharger rotational speed and

  13. KIC 6220497: a new Algol-type eclipsing binary with multiperiodic pulsations

    Science.gov (United States)

    Lee, Jae Woo; Hong, Kyeongsoo; Kim, Seung-Lee; Koo, Jae-Rim

    2016-08-01

    We present both binarity and pulsation of KIC 6220497 from the Kepler observations. The light curve synthesis shows that the eclipsing system is a semidetached Algol with parameters of q = 0.243 ± 0.001, i = 77.3 ± 0.3 deg, and ΔT = 3372 ± 58 K, in which the detached primary component fills its Roche lobe by ˜87 per cent. A multiple frequency analysis of the eclipse-subtracted light residuals reveals 33 frequencies in the range of 0.75-20.22 d-1 with amplitudes between 0.27 and 4.56 mmag. Among these, four are pulsation frequencies in fundamental (f1, f5) and p (f2, f7) modes, and six are orbital frequency (f8, f31) and its harmonics (f6, f11, f20, f24), which can be attributed to tidally excited modes. For the pulsation frequencies, the pulsation constants of 0.16-0.33 d and the period ratios of Ppul/Porb = 0.042-0.089 indicate that the primary component is a δ Sct pulsating star and, thus, KIC 6220497 is an oscillating eclipsing Algol (oEA) star. The dominant pulsation period of 0.117 4051 ± 0.000 0004 d is significantly longer than that expected from empirical relations that link the pulsation period with the orbital period. The surface gravity of log g1 = 3.78 ± 0.03 is clearly smaller than those of the other oEA stars with similar orbital periods. The pulsation period and the surface gravity of the pulsating primary demonstrate that KIC 6220497 would be the more evolved eclipsing binary, compared with normal oEA stars.

  14. Average transverse momentum quantities approaching the lightfront

    CERN Document Server

    Boer, Daniel

    2014-01-01

    In this contribution to Light Cone 2014, three average transverse momentum quantities are discussed: the Sivers shift, the dijet imbalance, and the $p_T$ broadening. The definitions of these quantities involve integrals over all transverse momenta that are overly sensitive to the region of large transverse momenta, which conveys little information about the transverse momentum distributions of quarks and gluons inside hadrons. TMD factorization naturally suggests alternative definitions of such integrated quantities, using Bessel-weighting and rapidity cut-offs, with the conventional definitions as limiting cases. The regularized quantities are given in terms of integrals over the TMDs of interest that are well-defined and moreover have the advantage of being amenable to lattice evaluations.

  15. A Novel Pre-cooling System for a Cryogenic Pulsating Heat Pipe

    Science.gov (United States)

    Xu, Dong; Liu, Huiming; Gong, Linghui; Xu, Xiangdong; Li, Laifeng

    To reduce the influence of the pipe material on the measurement of effective thermal conductivity, the pipe of a cryogenic pulsating heat pipe is generally made of stainless steel. Because of the low thermal conductivity of stainless steel, the pre-cooling of the evaporator in cryogenic pulsating heat pipe using helium as working fluid at 4.2 K is a problem. We designed a mechanical-thermal switch between the cryocooler and the evaporator, which was on during the pre-cooling process and off during the test process. By using the pre-cooling system, the cool down time of the cryogenic pulsating heat pipe was reduced significantly.

  16. A 'one in a million' case of pulsating thoracoabdominal mass.

    LENUS (Irish Health Repository)

    Tan, Lay Ong

    2012-11-01

    Ectopia cordis is a rare congenital malformation in which the heart is located partially or totally outside the thoracic cavity. It comprises 0.1% of congenital heart diseases. The authors present a case of a male baby born at term by emergency caesarean section due to prolonged fetal bradycardia, who was noted to have a large pulsating mass in the thoracoabdominal area. In view of lower thoracolumbar abdominal defect, ectopic placement of the umbilicus, deficiency of the diaphragmatic pericardium, deficiency of anterior diaphragm and intracardiac abnormalities, a diagnosis of ectopia cordis-Pentalogy of Cantrell was made. He was transferred to a tertiary centre and required oxygen supplement initially. He was sent home after 1 week, on propanolol, with weekly oxygen saturation checks. He is awaiting further surgical intervention pending the required weight gain.

  17. Pulsating instability and self-acceleration of fast turbulent flames

    CERN Document Server

    Poludnenko, A Y

    2015-01-01

    (Abridged) A series of three-dimensional numerical simulations is used to study the intrinsic stability of high-speed turbulent flames. Calculations model the interaction of a fully-resolved premixed flame with a highly subsonic, statistically steady, homogeneous, isotropic turbulence. We consider a wide range of turbulent intensities and system sizes, corresponding to the Damk\\"ohler numbers Da = 0.1-6.0. These calculations show that turbulent flames in the regimes considered are intrinsically unstable. In particular, we find three effects. 1) Turbulent flame speed develops pulsations with the observed peak-to-peak amplitude > 10 and a characteristic time scale close to a large-scale eddy turnover time. Such variability is caused by the interplay between turbulence, which continuously creates the flame surface, and highly intermittent flame collisions, which consume the flame surface. 2) Unstable burning results in the periodic pressure build-up and the formation of pressure waves or shocks, when the flame s...

  18. Improving Sensitivity to Weak Pulsations with Photon Probability Weighting

    CERN Document Server

    Kerr, Matthew

    2011-01-01

    All gamma-ray telescopes suffer from source confusion due to their inability to focus incident high-energy radiation, and the resulting background contamination can obscure the periodic emission from faint pulsars. In the context of the Fermi Large Area Telescope, we outline enhanced statistical tests for pulsation in which each photon is weighted by its probability to have originated from the candidate pulsar. The probabilities are calculated using the instrument response function and a full spectral model, enabling powerful background rejection. With Monte Carlo methods, we demonstrate that the new tests increase the sensitivity to pulsars by more than 50% under a wide range of conditions. This improvement may appreciably increase the completeness of the sample of radio-loud gamma-ray pulsars. Finally, we derive the asymptotic null distribution for the H-test, expanding its domain of validity to arbitrarily complex light curves.

  19. Asteroseismology of pulsating DA white dwarfs with fully evolutionary models

    Directory of Open Access Journals (Sweden)

    Althaus L.G.

    2013-03-01

    Full Text Available We present a new approach for asteroseismology of DA white dwarfs that consists in the employment of a large set of non-static, physically sound, fully evolutionary models representative of these stars. We already have applied this approach with success to pulsating PG1159 stars (GW Vir variables. Our white dwarf models, which cover a wide range of stellar masses, effective temperatures, and envelope thicknesses, are the result of fully evolutionary computations that take into account the complete history of the progenitor stars from the ZAMS. In particular, the models are characterized by self-consistent chemical structures from the centre to the surface, a crucial aspect of white dwarf asteroseismology. We apply this approach to an ensemble of 44 bright DAV (ZZ Ceti stars.

  20. Dynamic response of nuclear fuel assembly excited by pressure pulsations

    Directory of Open Access Journals (Sweden)

    Zeman V.

    2012-12-01

    Full Text Available The paper deals with dynamic load calculation of the hexagonal type nuclear fuel assembly caused by spatial motion of the support plates in the reactor core. The support plate motion is excited by pressure pulsations generated by main circulation pumps in the coolant loops of the primary circuit of the nuclear power plant. Slightly different pumps revolutions generate the beat vibrations which causes an amplification of fuel assembly component dynamic deformations and fuel rods coating abrasion. The cyclic and central symmetry of the fuel assembly makes it possible the system decomposition into six identical revolved fuel rod segments which are linked with central tube and skeleton by several spacer grids in horizontal planes.The modal synthesis method with condensation of the fuel rod segments is used for calculation of the normal and friction forces transmitted between fuel rods and spacer grids cells.

  1. A dynamic film model of the pulsating heat pipe

    International Nuclear Information System (INIS)

    This article deals with the numerical modeling of the pulsating heat pipe (PHP) and is based on the film evaporation/condensation model recently applied to the single-bubble PHP (Das et al., 2010, 'Thermally Induced Two-Phase Oscillating Flow Inside a Capillary Tube', Int. J. Heat Mass Transfer, 53(19-20), pp. 3905-3913). The described numerical code can treat the PHP of an arbitrary number of bubbles and branches. Several phenomena that occur inside the PHP are taken into account: coalescence of liquid plugs, film junction or rupture, etc. The model reproduces some of the experimentally observed regimes of functioning of the PHP such as chaotic or intermittent oscillations of large amplitudes. Some results on the PHP heat transfer are discussed. (author)

  2. Pulsating jet-like structures in magnetized plasma

    Science.gov (United States)

    Goncharov, V. P.; Pavlov, V. I.

    2016-08-01

    The formation of pulsating jet-like structures has been studied in the scope of the nonhydrostatic model of a magnetized plasma with horizontally nonuniform density. We discuss two mechanisms which are capable of stopping the gravitational spreading appearing to grace the Rayleigh-Taylor instability and to lead to the formation of stationary or oscillating localized structures. One of them is caused by the Coriolis effect in the rotating frames, and another is connected with the Lorentz effect for magnetized fluids. Magnetized jets/drops with a positive buoyancy must oscillate in transversal size and can manifest themselves as "radio pulsars." The estimates of their frequencies are made for conditions typical for the neutron star's ocean.

  3. Non-radial Pulsations in the Open Cluster NGC 3766

    CERN Document Server

    Roettenbacher, Rachael M; McSwain, M Virginia

    2009-01-01

    Non-radial pulsations (NRPs) are a proposed mechanism for the formation of decretion disks around Be stars and are important tools to study the internal structure of stars. NGC 3766 has an unusually large fraction of transient Be stars, so it is an excellent location to study the formation mechanism of Be star disks. High resolution spectroscopy can reveal line profile variations from NRPs, allowing measurements of both the degree, l, and azimuthal order, m. However, spectroscopic studies require large amounts of time with large telescopes to achieve the necessary high S/N and time domain coverage. On the other hand, multi-color photometry can be performed more easily with small telescopes to measure l only. Here, we present representative light curves of Be stars and non-emitting B stars in NGC 3766 from the CTIO 0.9m telescope in an effort to study NRPs in this cluster.

  4. Mathematical Modelling and Parameter Optimization of Pulsating Heat Pipes

    CERN Document Server

    Yang, Xin-She; Luan, Tao; Koziel, Slawomir

    2014-01-01

    Proper heat transfer management is important to key electronic components in microelectronic applications. Pulsating heat pipes (PHP) can be an efficient solution to such heat transfer problems. However, mathematical modelling of a PHP system is still very challenging, due to the complexity and multiphysics nature of the system. In this work, we present a simplified, two-phase heat transfer model, and our analysis shows that it can make good predictions about startup characteristics. Furthermore, by considering parameter estimation as a nonlinear constrained optimization problem, we have used the firefly algorithm to find parameter estimates efficiently. We have also demonstrated that it is possible to obtain good estimates of key parameters using very limited experimental data.

  5. Depression of the ULF geomagnetic pulsation related to ionospheric irregularities

    Directory of Open Access Journals (Sweden)

    O. A. Molchanov

    2004-06-01

    Full Text Available We consider a depression in intensity of ULF magnetic pulsations, which is observed on the ground surface due to appearance of the irregularities in the ionosphere. It is supposed that oblique Alfven waves in the ULF frequency range are downgoing from the magnetosphere and the horizontal irregularities of ionospheric conductivity are created by upgoing atmospheric gravity waves from seismic source. Unlike the companion paper by Molchanov et al. (2003, we used a simple model of the ionospheric layer but took into consideration the lateral inhomogeneity of the perturbation region in the ionosphere. It is shown that ULF intensity could be essentially decreased for frequencies f = 0.001-0.1 Hz at nighttime but the change is negligible at daytime in coincidence with observational results.

  6. An application of Bayesian inference for solar-like pulsators

    Science.gov (United States)

    Benomar, O.

    2008-12-01

    As the amount of data collected by space-borne asteroseismic instruments (such as CoRoT and Kepler) increases drastically, it will be useful to have automated processes to extract a maximum of information from these data. The use of a Bayesian approach could be very help- ful for this goal. Only a few attempts have been made in this way (e.g. Brewer et al. 2007). We propose to use Markov Chain Monte Carlo simulations (MCMC) with Metropolis-Hasting (MH) based algorithms to infer the main stellar oscillation parameters from the power spec- trum, in the case of solar-like pulsators. Given a number of modes to be fitted, the algorithm is able to give the best set of parameters (frequency, linewidth, amplitude, rotational split- ting) corresponding to a chosen input model. We illustrate this algorithm with one of the first CoRoT targets: HD 49933.

  7. Zinc electrodeposition from alkaline zincate solution by pulsating overpotentials

    Directory of Open Access Journals (Sweden)

    MILOS V. SIMICIC

    2000-09-01

    Full Text Available It is well known that smooth zinc deposits cannot be obtained from alkaline zincate using constant overpotential and current rate. During prolonged metal deposition, spongy and dendritic deposits are formed. It has been shown that the deposits are less agglomerated in the case of square-wave pulsating overpotentials regime than the ones obtained in case of constant overpotential regime. This is explained in a semiquantitative way by two phenomena: selective anodic dissolution during overpotentials “off” period and decreasing diffusion control. These effects is more pronounced at higher pause-to-pulse ratio. Increasing the pause-to-pulse ratio causes a reduction of the ratio between diffusion and activation overpotential, resulting in a more compact deposit. Confirmation of the proposed semiquantitative mathematical model was obtained by zinc electrodeposition onto a copper wire from a 0.1 M zincate solution in 1.0 M KOH at room temperature.

  8. Uncertainty propagation with functionally correlated quantities

    CERN Document Server

    Giordano, Mosè

    2016-01-01

    Many uncertainty propagation software exist, written in different programming languages, but not all of them are able to handle functional correlation between quantities. In this paper we review one strategy to deal with uncertainty propagation of quantities that are functionally correlated, and introduce a new software offering this feature: the Julia package Measurements.jl. It supports real and complex numbers with uncertainty, arbitrary-precision calculations, mathematical and linear algebra operations with matrices and arrays.

  9. Rice Consumption Patterns and Quantity Demand Elasticities

    OpenAIRE

    Isavilanonda Somporn; Kongrithi Weerasak

    2006-01-01

    This paper explores rice consumption patterns of Thai households and estimates income and price elasticities of quantity demand. The study found that the average annual consumption of rice for Thai households was 101 kilogram per person. The income elasticity of quantity demand is positive and inelastic (close to zero). The households in urban areas tend to have less income elasticity than those in rural areas. The households in the highest income rank of 25% had negative income elasticity. T...

  10. Pulsation, Mass Loss and the Upper Mass Limit

    Science.gov (United States)

    Klapp, J.; Corona-Galindo, M. G.

    1990-11-01

    RESUMEN. La existencia de estrellas con masas en exceso de 100 M0 ha sido cuestionada por mucho tiempo. Lfmites superiores para la masa de 100 M0 han sido obtenidos de teorfas de pulsaci6n y formaci6n estelar. En este trabajo nosotros primero investigamos la estabilidad radial de estrellas masivas utilizando la aproximaci6n clasica cuasiadiabatica de Ledoux, la aproximaci6n cuasiadiabatica de Castor y un calculo completamente no-adiabatico. Hemos encontrado que los tres metodos de calculo dan resultados similares siempre y cuando una pequefia regi6n de las capas externas de la estrella sea despreciada para la aproximaci6n clasica. La masa crftica para estabilidad de estrellas masivas ha sido encontrada en acuerdo a trabajos anteriores. Explicamos Ia discrepancia entre este y trabajos anteriores por uno de los autores. Discunmos calculos no-lineales y perdida de masa con respecto a) lfmite superior de masa. The existence of stars with masses in excess of 100 M0 has been questioned for a very long time. Upper mass limits of 100 Me have been obtained from pulsation and star formation theories. In this work we first investigate the radial stability of massive stars using the classical Ledoux's quasiadiabatic approximation. the Castor quasiadiabatic approximation and a fully nonadiabatic calculation. We have found that the three methods of calculation give similar results provided that a small region in outer layers of the star be neglected for the classical approximation. The critical mass for stability of massive stars is found to be in agreement with previous work. We explain the reason for the discrepancy between this and previous work by one of the authors. We discuss non-linear calculations and mass loss with regard to the upper mass limit. Key words: STARS-MASS FUNCTION - STARS-MASS LOSS - STARS-PULSATION

  11. Relationship of spontaneous retinal vein pulsation with ocular circulatory cycle.

    Directory of Open Access Journals (Sweden)

    Mijin Kim

    Full Text Available PURPOSE: To determine the timing of spontaneous venous pulsation (SVP relative to the ocular circulatory cycle by using the movie tool of confocal scanning laser ophthalmoloscope. METHODS: A video recording of the fundus was obtained using a confocal scanning laser ophthalmoscope (Spectralis HRA, Heidelberg Engineering, Heidelberg, Germany at 8 frames/s in 47 eyes (15 glaucoma patients and 32 glaucoma suspects with visible pulsation of both the central retinal artery (CRA and vein (CRV. The timing of the maximum and minimum diameters of the CRA (CRA(max and CRAmin, respectively and CRV (CRV(max and CRV(min, respectively was identified during four pulse cycles. The interval between CRV(min and CRA(min, and between CRV(max and CRA(max was expressed as the number of frames and as a percentage of the ocular circulatory cycle. RESULTS: The ocular circulatory cycle (from one CRA(max to the next lasted 7.7 ± 1.0 frames (958.8 ± 127.2 ms, mean ± SD, with a mean pulse rate of 62.6 beats/min. The diameter of the CRA was increased for 2.4 ± 0.5 frames (301.9 ± 58.8 ms and decreased for 5.3 ± 0.9 frames (656.9 ± 113.5 ms. CRV(max occurred 1.0 ± 0.2 frames after CRA(max (equivalent to 13.0% of the ocular circulatory cycle, while CRV(min occurred 1.1 ± 0.4 frames after CRA(min (equivalent to 14.6% of the ocular circulatory cycle. CONCLUSIONS: During SVP, the diameter of the CRV began to decrease at early diastole, and the reduction persisted until early systole. This finding supports that CRV collapse occurs during ocular diastole.

  12. Flow and mixing characteristics of an elevated pulsating transverse jet

    Science.gov (United States)

    Huang, Rong F.; Hsu, Ching M.

    2012-01-01

    Flow-evolution processes as well as the penetration, spread, and dispersion characteristics of elevated pulsating transverse jets were studied experimentally in a wind tunnel. Jet pulsations were induced by means of acoustic excitation. Streak pictures of the smoke-flow patterns, illuminated by a laser-light sheet in the median plane, were recorded by a high-speed digital camera. A hot-wire anemometer was used to digitize instantaneous velocities of instabilities in the flow. Penetration height and spread width were obtained through a binary edge identification technique. Tracer-gas concentrations were measured to provide information on jet dispersions and trajectories. Three characteristic flow modes (synchronized flapping jet, transition, and synchronized shear-layer vortices) were identified in the domain of the jet-to-crossflow momentum-flux ratio and the excitation Strouhal number. At low excitation Strouhal numbers, the jet column near the tube exit flapped back-and-forth periodically at the excitation frequency and induced large up-down motions of the deflected jet. The penetration, spread, and dispersion of the jet increased drastically compared with the non-excited jet because the up-down oscillating motions of the deflected jet transformed the axial momentum into oscillating lateral momentum. Forcing the jet into the transition and synchronized shear-layer vortices regimes caused the vortices to appear along the upwind shear layer of the deflected jet. Under these conditions, the penetration, spread, and dispersion of the jet presented insignificant increases because the entrainment effect induced by the shear-layer vortices was not as large as that produced by the jet oscillating motions in the synchronized flapping jet regime.

  13. The Effect of Flow Pulsations on Coriolis Mass Flow Meters

    Science.gov (United States)

    Cheesewright, R.; Clark, C.

    1998-11-01

    It has been reported that the accuracy of Coriolis mass flow meters can be adversely affected by the presence of pulsations (at particular frequencies) in the flow. A full analysis of the transient performance of a commercial Coriolis meter is only possible using finite element techniques. However, this is a transient, nonlinear problem in which the space and time variables are not (strictly) separable and the finite element techniques for tackling such problems make it desirable to have an analytical solution for a simplified meter, against which the finite element solution can be compared. This paper reports such a solution. The solution will also provide guidance for experiments. Existing analytical solutions for the performance of Coriolis meters in steady flow (a complex eigenvalue problem) are not easily extended to the transient flow case. The paper thus begins with the presentation of an alternative solution for steady flow through a simple, straight tube, Coriolis meter and it is notable that this solution gives a simple analytical expression for the experimentally observed small change in the resonant frequency of the meter, with flow rate, as well as an analytical expression for the meter sensitivity. The analysis is extended to the transient case, using classical, forced vibration, modal decomposition techniques. The solution shows that, unlike the steady flow case where the detector signals contain components at the drive frequency and the second mode frequency (Coriolis frequency), for pulsatile flow the detector signals will in general contain components involving at least four frequencies. It is demonstrated that the meter error depends on the algorithm used to estimate the phase difference from the detector signals. The particular flow pulsation frequencies which could possibly lead to large meter errors are identified.

  14. Time Domain Astronomy with the Harvard Plates: from Cepheids to DASCH

    Science.gov (United States)

    Grindlay, Jonathan E.

    2014-06-01

    The ~500,000 Harvard glass plate photographic negatives are the world’s largest and most complete (full sky; 107y time span) database for Time Domain Astronomy (TDA) on days-months-decades to century timescales. With plate fields of view ranging from 3o - 30o exposed quasi-randomly full sky from 1885 - 1992, any object is observed ~1000 - 3000 times, with limiting magnitudes ranging from B =12-18. I briefly review some of the colorful history of this massive plate-taking project and a few of the pivotal discoveries (e.g. the “Leavitt Law” for the Cepheid Period-Luminosity relation) made by visual studies of the plates by the true TDA pioneers, the likely Harvard (DASCH) project to fully digitize and reduce this wealth of data 1 Pb) and provide it on spinning disk to the full astronomical community and public. Using the full-sky APASS catalog giving BVR magnitudes (for V ~9-17) as well as GSC2.3.2 for both fainter and brighter stars, DASCH does spatially resolved (0.25o -0.6o bins) photometric calibrations to derive B magnitudes with rm 0.1mag over the full plate and over the (typically) ~6-8 different principal plate series (telescopes and plate scales) covering any given object, along with ~0.3-1 arcsec astrometry (depending on plate scale) for each stellar object averaged over ~1year. The high speed/precision scanner, plate processing, and analysis pipeline have now enabled the first data releases (DR1-DR3) of 12 to cover full sky and already enabled a wealth of new discoveries. I describe a few examples, such as: K2III giants with decadal variations; a new class of Symbiotic novae; ~50-100y recurrence times for black hole X-ray binary outbursts; and QPOs from 3C273. The DASCH data are increasingly available 15% now; 100% in 3.5y) for TDA on largely unexplored timescales. We are grateful to NSF for support with grants AST-0407380, AST-0909073 and AST-1313370.

  15. Numerical analysis of heat transfer in pulsating turbulent flow in a pipe

    Energy Technology Data Exchange (ETDEWEB)

    Xuefang Wang [Nebraska Univ., Lincoln, NE (United States). Dept. of Mechanical Engineering; Nengli Zhang [NASA Glenn Research Center at Lewis Field, Cleveland, OH (United States)

    2005-09-01

    Convection heat transfer in pulsating turbulent flow with large velocity oscillating amplitudes in a pipe at constant wall temperature is numerically studied. A low-Reynolds-number (LRN) k-{epsilon} turbulent model is used in the turbulence modeling. The model analysis indicates that Womersley number is a very important parameter in the study of pulsating flow and heat transfer. Flow and heat transfer in a wide range of process parameters are investigated to reveal the velocity and temperature characteristics of the flow. The numerical calculation results show that in a pulsating turbulent flow there is an optimum Womersley number at which heat transfer is maximally enhanced. Both larger amplitude of velocity oscillation and flow reversal in the pulsating turbulent flow also greatly promote the heat transfer enhancement. (author)

  16. NUMERICAL SIMULATION AND ANALYSIS OF PRESSURE PULSATION IN FRANCIS HYDRAULIC TURBINE WITH AIR ADMISSION

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this article, the three-dimensional unsteady multiphase flow is simulated in the whole passage of Francis hydraulic turbine. The pressure pulsation is predicted and compared with experimental data at positions in the draft tube, in front of runner, guide vanes and at the inlet of the spiral case. The relationship between pressure pulsation in the whole passage and air admission is analyzed. The computational results show: air admission from spindle hole decreases the pressure difference in the horizontal section of draft tube, which in turn decreases the amplitude of low-frequency pressure pulsation in the draft tube; the rotor-stator interaction between the air inlet and the runner increases the blade-frequency pressure pulsation in front of the runner.

  17. Relations of field line resonances and upstream waves and the winter attenuation of pulsations

    Directory of Open Access Journals (Sweden)

    J. VerH{o}

    Full Text Available Using data on the occurrence frequency of geomagnetic pulsations of different periods from three observatories in Central Europe, conclusions are drawn about the occurrence of field line resonances and pulsations directly driven by upstream waves at L-values below 3. It was found that both types occur during the interval studied (first 6 months of the year 1991, but both the occurrence frequency of the two types and the characteristic period of the field line resonance change significantly as compared to other intervals. During Northern winter, pulsation activity is severely damped in solar maximum years, including the year 1991. The decrease in the activity of the pulsations is more significant at shorter periods.

  18. Discovery of non-radial pulsations in the spectroscopic binary Herbig Ae star RS Cha

    CERN Document Server

    Böhm, T; Catala, C; Alecian, E; Pollard, K; Wright, D

    2008-01-01

    In this article we present a first discovery of non radial pulsations in both components of the Herbig Ae spectroscopic binary star RS Cha. The binary was monitored in quasi-continuous observations during 14 observing nights (Jan 2006) at the 1m Mt John (New Zealand) telescope with the Hercules high-resolution echelle spectrograph. The cumulated exposure time on the star was 44 hrs, corresponding to 255 individual high-resolution echelle spectra with $R = 45000$. Least square deconvolved spectra (LSD) were obtained for each spectrum representing the effective photospheric absorption profile modified by pulsations. Difference spectra were calculated by subtracting rotationally broadened artificial profiles; these residual spectra were analysed and non-radial pulsations were detected. A subsequent analysis with two complementary methods, namely Fourier Parameter Fit (FPF) and Fourier 2D (F2D) has been performed and first constraints on the pulsation modes have been derived. In fact, both components of the spect...

  19. The rapidly pulsating sdO star, SDSS J160043.6+074802.9

    CERN Document Server

    Rodríguez-López, C; Kilkenny, D; MacDonald, J; Moya, A; Koen, C; Woudt, P A; Wium, D J; Oruru, B; Zietsman, E

    2009-01-01

    A spectroscopic analysis of SDSS J160043.6+074802.9, a binary system containing a pulsating subdwarf-O (sdO) star with a late-type companion, yields Teff = 70 000 +/- 5000 K and log g = 5.25 +/- 0.30, together with a most likely type of K3V for the secondary star. We compare our results with atmospheric parameters derived by Fontaine et al. (2008) and in the context of existing evolution models for sdO stars. New and more extensive photometry is also presented which recovers most, but not all, frequencies found in an earlier paper. It therefore seems probable that some pulsation modes have variable amplitudes. A non-adiabatic pulsation analysis of uniform metallicity sdO models show those having log g > 5.3 to be more likely to be unstable and capable of driving pulsation in the observed frequency range.

  20. Recent advances in the theoretical modeling of pulsating low-mass He-core white dwarfs

    CERN Document Server

    Córsico, A H; Calcaferro, L M; Serenelli, A M; Kepler, S O; Jeffery, C S

    2016-01-01

    Many extremely low-mass (ELM) white-dwarf (WD) stars are currently being found in the field of the Milky Way. Some of these stars exhibit long-period nonradial $g$-mode pulsations, and constitute the class of ELMV pulsating WDs. In addition, several low-mass pre-WDs, which could be precursors of ELM WDs, have been observed to show short-period photometric variations likely due to nonradial $p$ modes and radial modes. They could constitute a new class of pulsating low-mass pre-WD stars, the pre-ELMV stars. Here, we present the recent results of a thorough theoretical study of the nonadiabatic pulsation properties of low-mass He-core WDs and pre-WDs on the basis of fully evolutionary models representative of these stars.