Fundamental stellar and accretion disc parameters of the eclipsing binary DQ Velorum

Abstract

Context. To add to the growing collection of well-studied double periodic variables (DPVs) we have carried out the first spectroscopic and photometric analysis of the eclipsing binary DQ Velorum to obtain its main physical stellar and orbital parameters. Aims. Combining spectroscopic and photometric observations that cover several orbital cycles allows us to estimate the stellar properties of the binary components and the orbital parameters. We also searched for circumstellar material around the more massive star. Methods. We separated DQ Velorum composite spectra and measured radial velocities with an iterative method for double spectroscopic binaries. We obtained the radial velocity curves and calculated the spectroscopic mass ratio. We compared our single-lined spectra with a grid of synthetic spectra and estimated the temperature of the stars. We modeled the V-band light curve with a fitting method based on the simplex algorithm, which includes an accretion disc. To constrain the main stellar parameters we fixed the mass ratio and donor temperature to the values obtained by our spectroscopic analysis. Results. We obtain a spectroscopic mass ratio q = 0.31 ± 0.03 together with donor and gainer masses M d = 2.2 ± 0.2 M , M g = 7.3 ± 0.3 M , the radii R d = 8.4 ± 0.2 R , R g = 3.6 ± 0.2 R and temperatures T d = 9400 ± 100 K, T g = 18 500 ± 500 K for the stellar components. We find that DQ Vel is a semi-detached system consisting of a B3V gainer and an A1III donor star plus an extended accretion disc around the gainer. The disc is filling 89% of the gainer Roche lobe with a temperature of 6580 ± 300 K at the outer radius. It has a concave shape that is thicker at its edge (d e = 0.6 ± 0.1 R ) than at its centre (d c = 0.3 ± 0.1 R ). We find a significant sub-orbital frequency of 0.19 d −1 in the residuals of the V-band light curve, which we interpret as a pulsation of an slowly pulsating B-type (SPB) of a gainer star. We also estimate the distance to the binary (d ∼ 3.1 kpc) using the absolute radii, apparent magnitudes, and effective temperatures of the components found in our study.

Fundamental parameters of the close interacting binary HD 170582 and its luminous accretion disc

“…We find that HD 170882 shows spectroscopic properties similar to other DPVs like AU Monocerotis, V 393 Scorpii, DQ Velorum and OGLE 05155332-6925581 (Mennickent et al, 2008, 2012a, 2012b, Barría et al 2013, Garrido et al 2013. These properties include the existence of an optically thick disc surrounding a B-type star and evidence for stream-disc interaction.…”

“…More than 200 DPVs have been found in the Galaxy and the Magellanic Clouds (Mennickent 2013), but very few of them have been studied spectroscopically (e.g. Barría et al 2013, Garrido et al 2013. The study of HD 170852 is important to characterize DPVs in terms of their fundamental physical parameters and also to help to understand the still unknown cause for the long photometric cycle.…”

Exploring the long-term variability and evolutionary stage of the interacting binary DQ Velorum

“…To compute the donor RVs, we used a donor template spectrum and apply a cross correlation process (CCR) using the IRAF fxcor task in the 4350-5000 Å wavelength range where we find more lines coming from the donor. We selected from a grid of synthetic spectra, a donor template spectrum with T d = 9400 K, log g d = 2.9, v r sin i = 75 km s −1 , and solar metallicity, according to the donor parameters found by Barría et al (2013). The grid of synthetic spectra was computed using atmospheric models with the line-blanketed LTE ATLAS9 code (Kurucz 1993), which treats line opacity with opacity distribution functions (ODFs).…”

“…6, Barría et al 2013). This can be related to the extra-emission component coming from the interaction region between the gas stream and the accretion disc.…”

“…Using the data obtained after a photometric and spectroscopic campaign carried out during 2008-2011, Barría et al (2013 determined the fundamental stellar and orbital parameters of this binary. Their techniques involved the separation of the DQ Vel composite spectra, radial velocity (RV) measurements, and a multicomponent fit to the V-band ASAS light curve.…”