K2 observations of binaries PHL 457 and EQ Psc Virtual Observatory Resource

Authors
  1. Baran A.S.
  2. Telting J.H.
  3. Jeffery C.S.
  4. Ostensen R.H.
  5. Vos J.
  6. Reed M.D.,Vuckovic M.
  7. Published by
    CDS
Abstract

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 0.801d, respectively. For EQ Psc, 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 4.6d (PHL 457) and 9.4d (EQ Psc). We made spectral energy distribution (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 EQ Psc clearly shows an infrared (IR) access consistent with a secondary with a temperature of about 6800K and a radius of 0.23R_{sun}_. This is the first detection of an IR access in any sdB+dM binary.

Keywords
  1. multiple-stars
  2. orbits
  3. subdwarf-stars
  4. variable-stars
  5. radial-velocity
  6. effective-temperature
  7. visible-astronomy
  8. spectroscopy
Bibliographic source Bibcode
2019MNRAS.489.1556B
See also HTML
https://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/489/1556
IVOA Identifier IVOID
ivo://CDS.VizieR/J/MNRAS/489/1556
Document Object Identifer DOI
doi:10.26093/cds/vizier.74891556

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History

2023-02-10T12:13:41Z
Resource record created
2023-02-10T12:13:41Z
Created
2024-08-20T20:12:34Z
Updated

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