A systematic study of variability among OB-stars based on HIPPARCOS photometry

Lefèvre, Laure; Марченко, С. В.; Moffat, A. F. J.; Acker, A.

doi:10.1051/0004-6361/200912304

Cited by 60 publications

(108 citation statements)

References 13 publications

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“…However, when the light curve is phased to a period of 39.22 days (bottom panel), many of the outbursts are roughly aligned and binning the data traces what could be considered an 'average' outburst for this star. Lefèvre et al (2009) use Hipparcos photometry to study variability among OB stars in a study that includes HD 81654. The authors list this star as having a variable type of 'GCAS?'…”

Section: Outburstsmentioning

confidence: 99%

Photometric Variability of the Be Star Population

Labadie-Bartz

Pepper

McSwain

et al. 2017

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Be stars have generally been characterized by the emission lines in their spectra, and especially the time variability of those spectroscopic features. They are known to also exhibit photometric variability at multiple timescales, but have not been broadly compared and analyzed by that behavior. We have taken advantage of the advent of wide-field, long-baseline, and high-cadence photometric surveys that search for transiting exoplanets to perform a comprehensive analysis of brightness variations among a large number of known Be stars. The photometric data comes from the KELT transit survey, with a typical cadence of 30 minutes, baseline of up to ten years, photometric precision of about 1%, and coverage of about 60% of the sky. We analyze KELT light curves of 610 known Be stars in both the Northern and Southern hemispheres in an effort to study their variability. Consistent with other studies of Be star variability, we find most of the stars to be photometrically variable. We derive lower limits on the fraction of stars in our sample that exhibit features consistent with nonradial pulsations (25%), outbursts (36%), and long term trends in the circumstellar disk (37%), and show how these are correlated with spectral sub-type. Other types of variability, such as those owing to binarity, are also explored. Simultaneous spectroscopy for some of these systems from the Be Star Spectral Database (BeSS) allow us to better understand the physical causes for the observed variability, especially in cases of outbursts and changes in the disk.

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Section: Outburstsmentioning

confidence: 99%

Photometric Variability of the Be Star Population

Labadie-Bartz

Pepper

McSwain

et al. 2017

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“…Schuster & Guichard (1984) listed HD 45314 as a very variable star in multi-band photometry collected between 1980 and 1983. Based on Hipparcos photometry, Lefèvre et al (2009) classified HD 45314 as an irregular variable of early spectral type. Figure 9 displays the photometric data along with the EWs of the Hα line.…”

Section: Photometrymentioning

confidence: 99%

Intriguing X-ray and optical variations of the γ Cassiopeiae analog HD 45314

Rauw

Nazé

Smith

et al. 2018

A&A

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Context. A growing number of Be and Oe stars, named the γ Cas stars, are known for their unusually hard and intense X-ray emission. This emission could either trace accretion by a compact companion or magnetic interaction between the star and its decretion disk. Aims. To test these scenarios, we carried out a detailed optical monitoring of HD 45314, the hottest member of the class of γ Cas stars, along with dedicated X-ray observations on specific dates. Methods. High-resolution optical spectra were taken to monitor the emission lines formed in the disk, while X-ray spectroscopy was obtained at epochs when the optical spectrum of the Oe star was displaying peculiar properties. Results. Over the last four years, HD 45314 has entered a phase of spectacular variations. The optical emission lines have undergone important morphology and intensity changes including transitions between single-and multiple-peaked emission lines as well as shell events, and phases of (partial) disk dissipation. Photometric variations are found to be anti-correlated with the equivalent width of the Hα emission. Whilst the star preserved its hard and bright X-ray emission during the shell phase, the X-ray spectrum during the phase of (partial) disk dissipation was significantly softer and weaker. Conclusions. The observed behaviour of HD 45314 suggests a direct association between the level of X-ray emission and the amount of material simultaneously present in the Oe disk as expected in the magnetic star-disk interaction scenario.

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“…Of the five observed stars for which periods are known, three [ Lupi (pulsation periods of 0.155 days (primary) and 0.096 days (secondary); Uytterhoeven et al 2005;Telting et al 2006), 33 Eri (0.864 days;De Cat et al 2005), and HY Vel (3.102 days; Lefévre et al 2009)] were observed with subexposures of hundredths of a period. 15 CMa (0.093-0.181 days; Shobbrook et al 2006) was observed with subexposures corresponding to less than 1/80th of the longer period, but about 1/60th of the shorter period.…”

Section: Espadons and Narvalmentioning

confidence: 99%

CRITICAL EVALUATION OF MAGNETIC FIELD DETECTIONS REPORTED FOR PULSATING B-TYPE STARS IN LIGHT OF ESPaDOnS, NARVAL, AND REANALYZED FORS1/2 OBSERVATIONS

Shultz

Wade

Grunhut

et al. 2012

ApJ

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Recent spectropolarimetric studies of seven slowly pulsating B (SPB) and β Cep stars have suggested that photospheric magnetic fields are more common in B-type pulsators than in the general population of B stars, suggesting a significant connection between magnetic and pulsational phenomena. We present an analysis of new and previously published spectropolarimetric observations of these stars. New Stokes V observations obtained with the high-resolution ESPaDOnS and Narval instruments confirm the presence of a magnetic field in one of the stars ( Lup), but find no evidence of magnetism in five others. A re-analysis of the published longitudinal field measurements obtained with the low-resolution FORS1/2 spectropolarimeters finds that the measurements of all stars show more scatter from zero than can be attributed to Gaussian noise, suggesting the presence of a signal and/or systematic underestimation of error bars. Re-reduction and re-measurement of the FORS1/2 spectra from the ESO archive demonstrates that small changes in reduction procedure lead to substantial changes in the inferred longitudinal field, and substantially reduces the number of field detections at the 3σ level. Furthermore, we find that the published periods are not unique solutions to the time series of either the original or the revised FORS1/2 data. We conclude that the reported field detections, proposed periods, and field geometry models for α Pyx, 15 CMa, 33 Eri, and V1449 Aql are artifacts of the data analysis and reduction procedures, and that magnetic fields at the reported strength are no more common in SPB/β Cep stars than in the general population of B stars.

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A systematic study of variability among OB-stars based on HIPPARCOS photometry

Cited by 60 publications

References 13 publications

Photometric Variability of the Be Star Population

Photometric Variability of the Be Star Population

Intriguing X-ray and optical variations of the γ Cassiopeiae analog HD 45314

CRITICAL EVALUATION OF MAGNETIC FIELD DETECTIONS REPORTED FOR PULSATING B-TYPE STARS IN LIGHT OF ESPaDOnS, NARVAL, AND REANALYZED FORS1/2 OBSERVATIONS

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