Bibcode
Kupfer, T.; Ramsay, G.; van Roestel, J.; Brooks, J.; MacFarlane, S. A.; Toma, R.; Groot, P. J.; Woudt, P. A.; Bildsten, L.; Marsh, T. R.; Green, M. J.; Breedt, E.; Kilkenny, D.; Freudenthal, J.; Geier, S.; Heber, U.; Bagnulo, S.; Blagorodnova, N.; Buckley, D. A. H.; Dhillon, V. S.; Kulkarni, S. R.; Lunnan, R.; Prince, T. A.
Bibliographical reference
The Astrophysical Journal, Volume 851, Issue 1, article id. 28, 10 pp. (2017).
Advertised on:
12
2017
Journal
Citations
25
Refereed citations
24
Description
We report the discovery of the ultracompact hot subdwarf (sdOB) binary
OW J074106.0–294811.0 with an orbital period of
{P}{orb}=44.66279+/- 1.16× {10}-4 minutes,
making it the most compact hot subdwarf binary known. Spectroscopic
observations using the VLT, Gemini and Keck telescopes revealed a
He-sdOB primary with an intermediate helium abundance,
{T}{eff} = 39 400+/- 500 K and {log}g = 5.74 ± 0.09.
High signal-to-noise ratio light curves show strong ellipsoidal
modulation resulting in a derived sdOB mass {M}{sdOB}=0.23+/-
0.12 {M}ȯ with a WD companion
({M}{WD}=0.72+/- 0.17 {M}ȯ ). The mass ratio
was found to be q={M}{sdOB}/{M}{WD}=0.32+/- 0.10.
The derived mass for the He-sdOB is inconsistent with the canonical mass
for hot subdwarfs of ≈ 0.47 {M}ȯ . To put
constraints on the structure and evolutionary history of the sdOB star
we compared the derived {T}{eff}, {log}g, and sdOB mass to
evolutionary tracks of helium stars and helium white dwarfs calculated
with Modules for Experiments in Stellar Astrophysics (MESA). We find
that the best-fitting model is a helium white dwarf with a mass of 0.320
{M}ȯ , which left the common envelope ≈ 1.1 {Myr}
ago, which is consistent with the observations. As a helium white dwarf
with a massive white dwarf companion, the object will reach contact in
17.6 Myr at an orbital period of 5 minutes. Depending on the
spin–orbit synchronization timescale the object will either merge
to form an R CrB star or end up as a stably accreting AM CVn-type system
with a helium white dwarf donor.
Related projects
Binary Stars
The study of binary stars is essential to stellar astrophysics. A large number of stars form and evolve within binary systems. Therefore, their study is fundamental to understand stellar and galactic evolution. Particularly relevant is that binary systems are still the best source of precise stellar mass and radius measurements. Research lines
Pablo
Rodríguez Gil
Black holes, neutron stars, white dwarfs and their local environment
Accreting black-holes and neutron stars in X-ray binaries provide an ideal laboratory for exploring the physics of compact objects, yielding not only confirmation of the existence of stellar mass black holes via dynamical mass measurements, but also the best opportunity for probing high-gravity environments and the physics of accretion; the most
Montserrat
Armas Padilla