Velocity monitoring of gamma-Cas stars reveals their binarity status

Abstract

The binary status of gamma-Cas stars has been discussed while theoretically examining the origin of their peculiar X-ray emission. However, except in two cases, no systematic radial velocity monitoring of these stars had been undertaken yet to clarify their status. We now fill this gap using TIGRE, CARMENES, and UVES high-resolution spectroscopy. Velocities were determined for 16 stars, revealing shifts and/or changes in line profiles. The orbit of six new binaries could be determined: the long periods (80-120d) and small velocity amplitudes (5-7km/s) suggest low mass companions (0.6-1 M${}_{\odot }$). The properties of the known gamma-Cas binaries appear similar to those of other Be systems, with no clear-cut separation between them. One of the new systems is a candidate for a rare case of quadruple system involving a Be star. Five additional gamma-Cas stars display velocity variations compatible with the presence of companions, but no orbital solution could yet be formally established for them hence they only receive the status of "binary candidate".

arXiv commentaccepted by MNRAS

References in corpus (54)

• Binary interaction dominates the evolution of massive stars
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• Southern Massive Stars at High Angular Resolution: Observational Campaign and Companion Detection
• Classical Be Stars: Rapidly Rotating B Stars with Viscous Keplerian Decretion Disks
• The High Angular Resolution Multiplicity of Massive Stars
• Sub-surface convection zones in hot massive stars and their observable consequences
• Effects of gravitational darkening on the determination of fundamental parameters in fast rotating B-type stars
• Evidence for a maximum mass cut-off in the neutron star mass distribution and constraints on the equation of state
• High-Mass X-ray Binaries in the Milky Way: A closer look with INTEGRAL
• Evolution towards the critical limit and the origin of Be stars
• Extracting Radial Velocities of A- and B-type Stars from Echelle Spectrograph Calibration Spectra
• On the formation of Be stars through binary interaction
• The 'hidden' companion in LB-1 unveiled by spectral disentangling
• A highly magnetised and rapidly rotating white dwarf as small as the Moon
• Detection of additional Be+sdO systems from IUE spectroscopy
• A naked-eye triple system with a nonaccreting black hole in the inner binary
• The Detection and Characterization of Be+sdO Binaries from HST/STIS FUV Spectroscopy
• Interacting Binaries with Eccentric Orbits II. Secular Orbital Evolution Due To Non-Conservative Mass Transfer
• Investigating the lack of main-sequence companions to massive Be stars
• Orbital evolution of mass-transferring eccentric binary systems. II. Secular Evolution
• The X-ray emission of the gamma Cassiopeiae stars
• FUV Detection of the Suspected Subdwarf Companion to the Be Star 59 Cygni
• The life cycles of Be viscous decretion discs: time-dependent modelling of infrared continuum observations
• Spectral and spatial imaging of the Be+sdO binary phi Persei
• Detection of a Hot Subdwarf Companion to the Be Star FY Canis Majoris
• A Study of Pi Aquarii During a Quasi-normal Star Phase: Refined Fundamental Parameters and Evidence for Binarity
• Prevalence of SED turndown among classical Be stars: Are all Be stars close binaries?
• Photometric Variability of the Be Star Population
• Using conditional entropy to identify periodicity
• On the kinematics of a runaway Be star population
• The Hot Companion and Circumbinary Disk of the Be Star HR 2142
• Hot stars observed by XMM-Newton II. A survey of Oe and Be stars
• High-resolution imaging of Galactic massive stars with AstraLux. I. 138 fields with delta > -25 degrees
• The relationship between gamma Cassiopeiae's X-ray emission and its circumstellar environment
• gamma Cas stars: Normal Be stars with disks impacted by the wind of a helium-star companion?
• A propelling neutron star in the enigmatic Be-star $\gamma$~Cassiopeia
• The Remarkable Be+sdOB Binary HD 55606 I: Orbital and Stellar Parameters
• Population Synthesis of Galactic Be-star Binaries with A Helium-star Companion
• Three discoveries of gamma Cas analogs from dedicated XMM-Newton observations of Be stars
• Gaia Reveals Evidence for Merged White Dwarfs
• Observations of Binary Stars with the Differential Speckle Survey Instrument. IX. Observations of Known and Suspected Binaries, and a Partial Survey of Be Stars
• TESS lightcurves of gamma-Cas stars
• Properties and nature of Be stars 30. Reliable physical properties of a semi-detached B9.5e+G8III binary BR CMi = HD 61273 compared to those of other well studied semi-detached emission-line binaries
• Is there a propeller neutron star in $\gamma$ Cas?
• Surprises in the simultaneous X-ray and optical monitoring of pi Aqr
• Intriguing X-ray and optical variations of the gamma Cas analog HD45314
• $\nu$ Gem: a hierarchical triple system with an outer Be star
• The 2011 Periastron Passage of the Be Binary delta Scorpii
• Evidence of an asymmetrical Keplerian disk in the Brγ and He I emission lines around the Be star HD 110432
• ARMADA I: Triple Companions Detected in B-Type Binaries alpha Del and nu Gem
• Apsidal motion in the massive binary HD152248
• The H-alpha Emission Line Variations of HR 6819
• Supersoft X-ray sources identified with Be binaries in the Magellanic Clouds
• Variations on a theme -- the puzzling behaviour of Schulte 12

Cited by in corpus (19)

• A catalogue of high-mass X-ray binaries in the Galaxy: from the INTEGRAL to the Gaia era
• The effects of stellar rotation along the main sequence of the 100 Myr old massive cluster NGC 1850
• The orbital and physical properties of five southern Be+sdO binary systems
• The X-ray emission of Be+stripped star binaries
• Gamma Cas Stars as Be + White Dwarf Binary Systems
• Ultraviolet Spectropolarimetry: on the origin of rapidly rotating B stars
• The X-ray emission of gamma Cassiopeiae during the 2020-2021 disc eruption
• Binarity at Low Metallicity (BLOeM) -- Multiplicity properties of Oe and Be stars
• X-ray and optical spectroscopic study of a gamma Cassiopeiae analog source pi Aquarii
• X-ray response to disk evolution in two gamma-Cas stars
• Fluorescent Fe K line emission of gamma Cas stars I. Do gamma Cas stars host propelling neutron stars?
• Newborn Be star systems observed shortly after mass transfer
• Reaching the boundary between stellar kinematic groups and very wide binaries. IV. The widest Washington double star systems with rho > 1000 arcsec in Gaia DR3
• X-ray emission of massive stars and their winds
• Classical Be stars
• Optical And X-ray Variability Of γ Cas Stars: Sao 49725
• Identifying and characterising the population of hot sub-luminous stars with multi-colour MeerLICHT data
• Fluorescent Fe K line emission of gamma Cas stars II. Predictions for magnetic interactions and white-dwarf accretion scenarios
• On Neutron Star Natal Kicks in High-Mass X-Ray Binaries: Insights from Population Synthesis