Faint but not forgotten. I. First results from a search for astrospheres around AGB stars in the far-ultraviolet

Abstract

Using the GALEX archive, we have discovered extended structures around ten asymptotic giant branch (AGB) stars (out of a total 92 searched) emitting in the far-ultraviolet (FUV) band. In all but one, we find the typical morphology expected for a spherical wind moving relative to, and interacting with the ISM to produce an astrosphere. The exception is V\,Hya whose mass-ejection is known to be highly aspherical, where we find evidence of its large parabolic outflows interacting with the ISM, and its collimated, extreme velocity outflows interacting with the circumstellar medium. For 8 objects with relatively large proper motions, we find (as expected) that the termination-shock region lies in a hemisphere that contains the proper motion vector. Radial intensity cuts for each source have been used to locate the termination shock and the astropause's outer edge. In a few objects, the cuts also reveal faint emission just outside the astropause that likely arises in shocked ISM material. We have used these data, together with published mass-loss rates and wind expansion velocities, to determine the total mass lost and duration for each source -- we find that the duration of and total mass in the shocked wind are significantly larger than their corresponding values for the unshocked wind. The combination of FUV and far-IR data on AGB astrospheres, provides a unique database for theoretical studies (numerical simulations) of wind-ISM interactions. We show that a Cyclical Spatial Heterodyne Spectrometer on a small space-based telescope, can provide high-resolution spectra of astrospheres to confirm the emission mechanism.

References in corpus (43)

• Validation of the new Hipparcos reduction
• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• Mass Loss: Its Effect on the Evolution and Fate of High-Mass Stars
• New models for the evolution of Post-Asymptotic Giant Branch stars and Central Stars of Planetary Nebulae
• Post-Asymptotic Giant Branch Evolution of Low- and Intermediate-Mass Stars. Preliminary Results
• The On-Orbit Performance of the Galaxy Evolution Explorer
• The Vertical Structure of Warm Ionised Gas in the Milky Way
• Nonlinear Instabilities in Shock-Bounded Slabs
• 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
• Mass loss rates of a sample of irregular and semiregular M-type AGB-variables
• Imaging the circumstellar envelopes of AGB stars
• Local Stellar Kinematics from RAVE Data: I. Local Standard of Rest
• Mass loss in main-sequence B stars
• The enigmatic nature of the circumstellar envelope and bow shock surrounding Betelgeuse as revealed by Herschel. I. Evidence of clumps, multiple arcs, and a linear bar-like structure
• New observations and models of circumstellar CO line emission of AGB stars in the Herschel SUCCESS programme
• Distance estimates for AGB stars from parallax measurements
• 3D Simulations of Betelgeuse's Bow Shock
• E-BOSS: An Extensive stellar BOw Shock Survey. II. Catalogue second release
• Detection of a Far-Infrared Bow-Shock Nebula Around R Hya: the First MIRIAD Results
• The Astrosphere of the Asymptotic Giant Branch Star Irc+10216
• AKARI/FIS Mapping of the ISM-Wind Bow Shock around Alpha Ori
• High-resolution HST/ACS images of detached shells around carbon stars
• Vortices in the wakes of AGB stars
• High-Speed Bullet Ejections during the AGB to Planetary Nebula Transition: HST Observations of the Carbon Star, V Hydrae
• Discovery of an HI Counterpart to the Extended Tail of Mira
• GALExtin: An alternative online tool to determine the interstellar extinction in the Milky Way
• The detached dust shells of AQ And, U Ant, and TT Cyg
• The Interaction of Asymptotic Giant Branch Stars with the Interstellar Medium
• To see or not to see a Bow Shock: Identifying Bow Shocks with H-Alpha Allsky Surveys
• Photodissociation of CO in the outflow of evolved stars
• Infrared Photometric Properties of 709 Candidate Stellar Bowshock Nebulae
• Rings and filaments: The remarkable detached CO shell of U Antliae
• Cometary Astropause of Mira Revealed in the Far-Infrared
• Deep optical imaging of AGB circumstellar envelopes
• An HI Imaging Survey of Asymptotic Giant Branch Stars
• The interface between the stellar wind and interstellar medium around R Cassiopeiae revealed by far-infrared imaging
• Discovery of a Shell of Neutral Atomic Hydrogen Surrounding the Carbon Star IRC+10216
• The Rapidly Evolving AGB Star, V Hya: ALMA finds a Multi-Ring Circus with High-Velocity Outflows
• The astrosphere of the Asymptotic Giant Branch star CIT 6
• Dust in AGB wind-ISM interaction regions
• Circumstellar envelopes of semi-regular long-period variables: mass-loss rate estimates and general model-fitting of the molecular gas
• High-Velocity Bullets from V Hydrae, an AGB Star in Transition: Ejection History and Spatio-Kinematic Modeling

Cited by in corpus (1)

• Extended far-UV emission surrounding asymptotic giant branch stars as seen by GALEX