English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Binarity is believed to dramatically affect the history and geometry of massloss in AGB and post-AGB stars, but observational evidence of binarity issorely lacking. As part of a project to search for hot binary companions tocool AGB stars using the GALEX archive, we discovered a late-M star, Y Gem, tobe a source of strong and variable UV and X-ray emission. Here we report UVspectroscopic observations of Y Gem obtained with the Hubble Space Telescopethat show strong flickering in the UV continuum on time-scales of <~20 s,characteristic of an active accretion disk. Several UV lines with P-Cygni-typeprofiles from species such as Si IV and C IV are also observed, with emissionand absorption features that are red- and blue- shifted by velocities of ~500km/s from the systemic velocity. Our model for these (and previous)observations is that material from the primary star is gravitationally capturedby a companion, producing a hot accretion disk. The latter powers a fastoutflow that produces blue-shifted features due to absorption of UV continuumemitted by the disk, whereas the red-shifted emission features arise in heatedinfalling material from the primary. The outflow velocities support a previousinference by Sahai et al. (2015) that Y Gem's companion is a low-massmain-sequence star. Blackbody fitting of the UV continuum implies an accretionluminosity of about 13 Lsun and thus a mass-accretion rate >5e-7 Msun/yr; weinfer that Roche lobe overflow is the most likely binary accretion mode for YGem.

Binarity and Accretion in AGB Stars: HST/STIS Observations of UV Flickering in Y Gem