The binary properties of the pulsating subdwarf B eclipsing binary PG 1336-018 (NY Virginis)

Abstract

Aims. We present an unbiased orbit solution and mass determination of the components of the eclipsing binary PG 1336−018 as a critical test for the formation scenarios of subdwarf B stars. Methods. We obtained high-resolution time series VLT/UVES spectra and high-speed multicolour VLT/ULTRACAM photometric observations of PG 1336−018, a rapidly pulsating subdwarf B star in a short period eclipsing binary. Results. Combining the radial velocity curve obtained from the VLT/UVES spectra with the VLT/ULTRACAM multicolour lightcurves, we determined numerical orbital solutions for this eclipsing binary. Due to the large number of free parameters and their strong correlations, no unique solution could be found, only families of solutions. We present three solutions of equal statistical significance, two of which are compatible with the primary having gone through a core He-flash and a common-envelope phase described by the α-formalism. These two models have an sdB primary of 0.466 M and 0.389 M , respectively. Finally, we report the detection of the Rossiter-McLaughlin effect for PG 1336−018.

Impact of helium diffusion and helium-flash-induced carbon production on gravity-mode pulsations in subdwarf B stars

“…Asteroseismology provides an alternative method, since it allows a detailed study of the interior of non-radially pulsating stars. The consistency of both approaches has been achieved for PG 1336−018 (see Vučković et al 2007;Hu et al 2007;Charpinet et al 2008).…”

A preliminary look at the empirical mass distribution of hot B subdwarf stars

“…The latter is a rather remarkable (and very rare) system consisting of a sdB+dM binary star undergoing spectacular eclipses, while the sdB component pulsates in p-modes of the V361 Hya type. A detailed study of the light curve of the system -suitably cleansed of the "annoying" short-period oscillations due to pulsations -was carried out by Vuckovic et al (2007), leading to three possible solutions that could not be formally discriminated between themselves. Model I of Vuckovic et al (2007) led to the following estimates of the mass and radius of the sdB star, M = 0.389 ± 0.005 M and R = 0.14 ± 0.01 R , Model II led to M = 0.466±0.006 M and R = 0.15±0.01 R , and Model III led to M = 0.530 ± 0.007 M and R = 0.15 ± 0.01 R .…”

“…A detailed study of the light curve of the system -suitably cleansed of the "annoying" short-period oscillations due to pulsations -was carried out by Vuckovic et al (2007), leading to three possible solutions that could not be formally discriminated between themselves. Model I of Vuckovic et al (2007) led to the following estimates of the mass and radius of the sdB star, M = 0.389 ± 0.005 M and R = 0.14 ± 0.01 R , Model II led to M = 0.466±0.006 M and R = 0.15±0.01 R , and Model III led to M = 0.530 ± 0.007 M and R = 0.15 ± 0.01 R . In a parallel and independent effort, Charpinet et al (2008) rather exploited the pulsation data for PG 1336−018, ignoring completely the other characteristics of the light curve, and obtained a unique seismic solution characterized by M = 0.459 ± 0.005 M and R = 0.151 ± 0.001 R , along with other derived parameters on the sdB component.…”

Ground‐based follow‐up in relation to Kepler asteroseismic investigation

“…First, through the spectra it is possible to derive constraints on the component masses (e.g. Tango et al 2006;Vučkovic et al 2007;Creevey et al 2009;Desmet et al 2010), which is valuable information for seismic models and models on stellar structure and (binary) evolution. Second, in the case of doublelined spectroscopic binaries it is possible to disentangle the component spectra (Harmanec et al 2004) and to study the line-profile variability of the disentangled components in full detail .…”