Ultraviolet emission from main-sequence companions of AGB stars

Abstract

Although the majority of known binary Asymptotic Giant Branch (AGB) stars are symbiotic systems (i.e. with a WD as a secondary star), main-sequence companions of AGB stars can be more numerous, even though they are more difficult to find because the primary high luminosity hampers the detection of the companion at visual wavelengths. However, in the ultraviolet the flux emitted by a secondary with T eff > 5500 ~ 6000 K may prevail over that of the primary, and then it can be used to search for candidates to binary AGB stars. In this work, theoretical atmosphere models are used to calculate the UV excess in the GALEX near- and far-UV bands due to a main-sequence companion. After analysing a sample of confirmed binary AGB stars, we propose as a criterium for binarity: (1) the detection of the AGB star in the GALEX far-UV band and/or (2) a GALEX near-UV observed-to-predicted flux ratio > 20. These criteria have been applied to a volume-limited sample of AGB stars within 500 pc of the Sun; 34 out of the sample of 58 AGB stars ( ~ 60%) fulfill them, implying to have a MS companion of spectral type earlier than K0. The excess in the GALEX near- and far-UV bands cannot be attributed to a single temperature companion star, thus suggesting that the UV emission of the secondary might be absorbed by the extended atmosphere and circumstellar envelope of the primary or that UV emission is produced in accretion flows.

Accepted for publication in MNRAS, 12 pages, 4 figures

References in corpus (32)

• Validation of the new Hipparcos reduction
• The Galaxy Evolution Explorer: A Space Ultraviolet Survey Mission
• Common Envelope Evolution: Where we stand and how we can move forward
• A standard stellar library for evolutionary synthesis: I. Calibration of theoretical spectra
• Modelling the Galactic Interstellar Extinction Distribution in Three Dimensions
• SB9: The Ninth Catalogue of Spectroscopic Binary Orbits
• The Second-Generation Guide Star Catalog: Description and Properties
• A catalogue of symbiotic stars
• Empirical extinction coefficients for the GALEX, SDSS, 2MASS and WISE passbands
• The On-Orbit Performance of the Galaxy Evolution Explorer
• Fundamental parameters and infrared excesses of Hipparcos stars
• Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles - II. CO line survey of evolved stars: derivation of mass-loss rate formulae
• A far-infrared survey of bow shocks and detached shells around AGB stars and red supergiants
• A recalibration of optical photometry: Tycho-2, Strömgren, and Johnson systems
• The "Tip" of the Red Giant Branch as a distance indicator: results from evolutionary models
• Proper-motion binaries in the Hipparcos Catalogue. Comparison with radial velocity data
• The binary fraction of planetary nebula central stars I. A high-precision, I-band excess search
• Statistical Properties of the GALEX/SDSS matched source catalogs, and classification of the UV sources
• Hydrodynamic Simulations of the Interaction between an AGB Star and a Main Sequence Companion in Eccentric Orbits
• Binarity in Cool Asymptotic Giant Branch Stars: A Galex Search for Ultraviolet Excesse
• The dust disk and companion of the nearby AGB star L2 Puppis - SPHERE/ZIMPOL polarimetric imaging at visible wavelengths
• How many Hipparcos Variability-Induced Movers are genuine binaries?
• Large-scale environments of binary AGB stars probed by Herschel - I. Morphology statistics and case studies of R Aquarii and W Aquilae
• Old Star Clusters in the FSR catalogue
• Spectroscopic binaries among Hipparcos M giants I. Data, orbits, and intrinsic variations
• A Pilot Deep Survey for X-Ray Emission from fuvAGB Stars
• AKARI's infrared view on nearby stars : Using AKARI Infrared Camera All-Sky Survey, 2MASS, and Hipparcos catalog
• AKARI's infrared view on nearby stars : Using AKARI Infrared Camera All-Sky Survey, 2MASS, and Hipparcos catalog
• Strong Variable Ultraviolet Emission from Y Gem: Accretion Activity in an AGB Star with a Binary Companion?
• Classifying the secondary component of the binary star W Aquilae
• First Detection of UV emission from a Detached Dust Shell: GALEX Observations of the Carbon AGB Star U Hya
• On the central symmetry of the circumstellar envelope of RS Cnc

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• Impact of a companion and of chromospheric emission on the shape of chromosome maps for globular clusters
• The Role of Ultraviolet Photons in Circumstellar Astrochemistry
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