K2 observations of the sdBV plus dM/bd binaries PHL457 and EQPsc
- We present an analysis of two pulsating subdwarf B stars PHL 457 and EQ Psc observed during the K2 mission. The K2 light curves of both stars show variation consistent with irradiation of a cooler companion by the hot subdwarf. They also show higher frequency oscillations consistent with pulsation. Using new spectroscopic data, we measured the radial velocity, effective temperature, surface gravity, and helium abundance of both hot subdwarfs as a function of orbital phase. We confirm the previously published spectroscopic orbit of PHL 457, and present the first spectroscopic orbit of EQ Psc. The orbital periods are 0.313 and 0.801 d, respectively. For EQPsc, we find a strong correlation between T-eff and orbital phase, due to contribution of light from the irradiated companion. We calculated amplitude spectra, identified significant pulsation frequencies, and searched for multiplets and asymptotic period spacings. By means of multiplets and period spacing, we identified the degrees of several pulsation modes in each star. The g-modeWe present an analysis of two pulsating subdwarf B stars PHL 457 and EQ Psc observed during the K2 mission. The K2 light curves of both stars show variation consistent with irradiation of a cooler companion by the hot subdwarf. They also show higher frequency oscillations consistent with pulsation. Using new spectroscopic data, we measured the radial velocity, effective temperature, surface gravity, and helium abundance of both hot subdwarfs as a function of orbital phase. We confirm the previously published spectroscopic orbit of PHL 457, and present the first spectroscopic orbit of EQ Psc. The orbital periods are 0.313 and 0.801 d, respectively. For EQPsc, we find a strong correlation between T-eff and orbital phase, due to contribution of light from the irradiated companion. We calculated amplitude spectra, identified significant pulsation frequencies, and searched for multiplets and asymptotic period spacings. By means of multiplets and period spacing, we identified the degrees of several pulsation modes in each star. The g-mode multiplets indicate subsynchronous core rotation with periods of 4.6 d (PHL 457) and 9.4 d (EQ Psc). We made spectral energy disctribution (SED) fits of PHL 457 and EQ Psc using available broad-band photometry and Gaia data. While the SED of PHL 457 shows no evidence of a cool companion, the SED for EQPsc clearly shows an infrared (IR) access consistent with a secondary with a temperature of about 6800K and a radius of 0.23 R-circle dot. This is the first detection of an IR access in any sdB + dM binary.…
Author details: | Andrzej S. BaranORCiD, J. H. Telting, C. Simon JefferyORCiD, R. H. Ostensen, Joris VosORCiD, M. D. Reed, Maja Vŭcković |
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DOI: | https://doi.org/10.1093/mnras/stz2209 |
ISSN: | 0035-8711 |
ISSN: | 1365-2966 |
Title of parent work (English): | Monthly notices of the Royal Astronomical Society |
Publisher: | Oxford Univ. Press |
Place of publishing: | Oxford |
Publication type: | Article |
Language: | English |
Date of first publication: | 2019/08/12 |
Publication year: | 2019 |
Release date: | 2020/11/23 |
Tag: | binaries: general; stars: individual (PHL 457, EQ Psc); stars: oscillations (including pulsations) |
Volume: | 489 |
Issue: | 2 |
Number of pages: | 16 |
First page: | 1556 |
Last Page: | 1571 |
Funding institution: | Polish National Science Center [UMO-2017/26/E/ST9/00703, UMO-2017/25/B/ST9/02218]; Northern Ireland Department for Communities; Robert Martin Ayers Sciences Fund; National Aeronautics and Space AdministrationNational Aeronautics & Space Administration (NASA); National Science FoundationNational Science Foundation (NSF) |
Organizational units: | Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie |
DDC classification: | 5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik |
Peer review: | Referiert |