Search results for "stars: binaries"
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Three X-ray Flares Near Primary Eclipse of the RS CVn Binary XY UMa
2016
We report on an archival X-ray observation of the eclipsing RS CVn binary XY UMa ($\rm P_{orb}\approx$ 0.48d). In two $\emph{Chandra}$ ACIS observations spanning 200 ks and almost five orbital periods, three flares occurred. We find no evidence for eclipses in the X-ray flux. The flares took place around times of primary eclipse, with one flare occurring shortly ($<0.125\rm P_{orb}$) after a primary eclipse, and the other two happening shortly ($<0.05\rm P_{orb}$) before a primary eclipse. Two flares occurred within roughly one orbital period ($\Delta \phi\approx1.024\rm P_{orb}$) of each other. We analyze the light curve and spectra of the system, and investigate coronal length scales both…
Correlated X-ray spectral and timing variability of the Be/X-ray binary V0332+53/BQ Camelopardalis during a type II outburst
2005
We have used INTEGRAL & RXTE data to investigate the timing properties of the source in correlation with its spectral states as defined by different positions in the colour-colour diagram. The source shows two distinct branches in the colour-colour diagram that resemble those of the Z sources. The hard branch (similar to the horizontal branch of Z sources) is characterised by a low-amplitude change of the hard colour compared to the change in the soft colour. In the soft branch (analogue to the normal branch) the amplitude of variability of the hard colour is about three times larger than that of the soft colour. As the count rate decreases the source moves up gradually through the soft…
A study of the B and Be star population in the field of the LMC open cluster NGC 2004 with VLT-FLAMES
2005
Observations of hot stars belonging to the young cluster LMC-NGC2004 and its surrounding region have been obtained with the VLT-GIRAFFE facilities in MEDUSA mode. 25 Be stars were discovered; the proportion of Be stars compared to B-type stars is found to be of the same order in the LMC and in the Galaxy fields. 23 hot stars were discovered as spectroscopic binaries (SB1 and SB2), 5 of these are found to be eclipsing systems from the MACHO database, with periods of a few days. About 75% of the spectra in our sample are polluted by hydrogen (Halpha and Hgamma), [SII] and [NII] nebular lines. These lines are typical of HII regions. They could be associated with patchy nebulosities with a bi-m…