A New, Bright, Short-Period, Emission Line Binary in Ophiuchus

TL;DR

This paper reports the discovery and detailed analysis of a new short-period emission line binary star in Ophiuchus, classified as a UX UMa subtype of cataclysmic variable, with spectroscopic and photometric evidence of accretion processes.

Contribution

It presents the first detailed spectroscopic and photometric characterization of LS IV -08 3, establishing it as a new short-period CV in the UX UMa subclass with evidence of accretion disk and donor star irradiation.

Findings

Orbital period of 0.1952894 days determined from radial velocity variations.

Presence of emission lines indicating accretion disk and irradiated donor star.

Likely association with a weak X-ray source, supporting CV classification.

Abstract

The 11th magnitude star LS IV -08 3 has been classified previously as an OB star in the Luminous Stars survey, or alternatively as a hot subdwarf. It is actually a binary star. We present spectroscopy, spectroscopic orbital elements, and time series photometry, from observations made at the Kitt Peak National Observatory 2.1m, Steward Observatory 2.3m, MDM Observatory 1.3m and 2.4m, Hobby-Eberly 9.2m, and Michigan State University 0.6m telescopes. The star exhibits emission of varying strength in the cores of H and He I absorption lines. Emission is also present at 4686 Angstroms (He II) and near 4640/4650 Angstroms (N III/C III). Time-series spectroscopy collected from 2005 July to 2007 June shows coherent, periodic radial velocity variations of the H-alpha line, which we interpret as orbital motion with a period of 0.1952894(10) days. High-resolution spectra show that there are two emission components, one broad and one narrow, moving in antiphase, as might arise from an accretion disk and the irradiated face of the mass donor star. Less coherent, low-amplitude photometric variability is also present on a timescale similar to the orbital period. Diffuse interstellar bands indicate considerable reddening, which however is consistent with a distance of ~100-200 pc. The star is the likely counterpart of a weak ROSAT X-ray source, whose properties are consistent with accretion in a cataclysmic variable (CV) binary system. We classify LS IV -08 3 as a new member of the UX UMa subclass of CV stars.