X-ray response to disk evolution in two gamma-Cas stars
arXiv:2202.00278 · doi:10.1093/mnras/stac314
Abstract
The Halpha emission of a set of southern gamma-Cas stars was monitored since 2019, with the aim of detecting transition events and examining how their peculiar X-ray emission would react in such cases. Two stars, HD119682 and V767Cen, were found to display slowly decreasing disk emissions. These decreases were not perfectly monotonic and several temporary and limited re-building events were observed. For HD119682, the emission component in Halpha disappeared in mid-July 2020. In X-rays, the X-ray flux was twice smaller than recorded two decades ago but of a similar level as observed a decade ago. The X-ray flux decreased over the campaign by 30%, but the hardness remained similar in datasets of all epochs. In particular, the gamma-Cas character remained as clear as before even when there was no trace of disk emission in the Halpha line. For V767Cen, the full disappearance of disk emission in Halpha never occurred. We followed closely a disk rebuilding event, but no significant change in flux or hardness was detected. These behaviours are compared to those of other gamma-Cas stars and their consequences on the X-ray generation are discussed.
arXiv commentaccepted by MNRAS
References in corpus (27)
- The chemical composition of the Sun
- The Be/X-ray transient 4U 0115+63/V635 Cas: II. Outburst mechanisms
- Catalogue of Be/X-ray binary systems in the Small Magellanic Cloud: X-ray, optical & IR properties
- The X-ray emission of the gamma Cassiopeiae stars
- X-ray emission from interacting massive binaries: a review of 15 years of progress
- X-ray and Optical Variations in the Classical Be Star gamma Cas
- Line-driven ablation of circumstellar disks: I. Optically thin decretion disks of classical Oe/Be stars
- Hot stars observed by XMM-Newton II. A survey of Oe and Be stars
- Strong outburst activity of the X-ray pulsar X Persei during 2001-2011
- Joint H-alpha and X-Ray Observations of Massive X-Ray Binaries. III. The Be X-ray Binaries HDE 245770 = A 0535+26 and X Persei
- X-Ray and Optical Observations of A 0535+26
- gamma Cas stars: Normal Be stars with disks impacted by the wind of a helium-star companion?
- Velocity monitoring of gamma-Cas stars reveals their binarity status
- A propelling neutron star in the enigmatic Be-star ~Cassiopeia
- Long-term optical variability of high-mass X-ray binaries. II. Spectroscopy
- On the relationship between circumstellar disc size and X-ray outbursts in Be/X-ray binaries
- Discovery of Rapidly Moving Partial X-ray Absorbers within gamma Cassiopeiae
- Magnetically Confined Wind Shocks in X-rays - a Review
- TESS lightcurves of gamma-Cas stars
- Surprises in the simultaneous X-ray and optical monitoring of pi Aqr
- Extraordinarily Hot X-ray Emission from the 09 Emission Line Star HD 119682
- Intriguing X-ray and optical variations of the gamma Cas analog HD45314
- Characterization of the X-ray light curve of the gamma Cas-like B1e star HD110432
- A Multi-wavelength study of 1WGA J1346.5-6255: a new Cas analog unrelated to the background supernova remnant G309.2-00.6
- Spectral observations of X Persei: Connection between H-alpha and X-ray emission
- Soft and hard X-ray dips in the light curves of gamma Cassiopeiae
- Long-term optical and X-ray variability of the Be/X-ray binary H 1145-619: discovery of an on-going retrograde density wave