We present the discovery of long-period, low-amplitude, g-mode pulsations in the intermediate He-rich hot subdwarf (sdOB) star Feige 46. So far, only one other He-enriched sdOB star (LS IV-14? °? 116) was known to exhibit such pulsations. From our ground-based light curves of Feige 46, we extracted five independent periodicities ranging from 2294 s to 3400 s. We fit our optical spectrum of the star with our grid of non-local thermodynamic equilibrium (NLTE) model atmospheres and derived the following atmospheric parameters: Teff? =? 36120? ±? 230 K, log g? =? 5.93? ±? 0.04, and log N(He)/N(H) = -0.32 ± 0.03 (formal fitting errors only). These parameters are very similar to those of LS IV-14? °? 116 and place Feige 46 well outside of the instability strip where the hydrogen-rich g-mode sdB pulsators are found. We used the Gaia parallax and proper motion of Feige 46 to perform a kinematic analysis of this star and found that it likely belongs to the Galactic halo population. This is most certainly an intriguing and interesting result given that LS IV-14? °? 116 is also a halo object. The mechanism responsible for the pulsations in these two peculiar objects remains unclear, but a possible scenario involves the ? -mechanism. Although they are the only two members in their class of variable stars, these pulsators appear to have more in common than just their pulsation properties.
|Original language||English (US)|
|Journal||Astronomy and astrophysics|
|State||Published - Mar 1 2019|
- Stars: individual: Feige 46
- Stars: oscillations
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science
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sdOB star Feige 46 spectrum
Latour, M. (Creator), Green, E. M. (Creator) & Fontaine, G. (Creator), Centre de Donnees Strasbourg (CDS), 2019
DOI: 10.26093/cds/vizier.36239012, https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/623/L12