A search for new hot subdwarf stars by means of Virtual Observatory tools II

TL;DR

This study used Virtual Observatory tools and multi-band sky survey data to efficiently identify 65 new hot subdwarf stars, demonstrating a high success rate and potential binary nature through infrared excess detection.

Contribution

The paper introduces a novel VO-based selection method combining photometric and proper motion filters to discover uncatalogued hot subdwarfs with over 95% accuracy.

Findings

Identified 65 new hot subdwarfs with high classification accuracy.

Detected infrared excesses indicating binary companions in nearly half of the candidates.

Achieved an efficiency of at least 80% in selecting true hot subdwarfs.

Abstract

Recent massive sky surveys in different bandwidths are providing new opportunities to modern astronomy. The Virtual Observatory (VO) represents the adequate framework to handle the huge amount of information available and filter out data according to specific requirements. In this work, we applied a selection strategy to find new, uncatalogued hot subdwarfs making use of VO tools. We used large area catalogues (GALEX, SDSS, SuperCosmos, 2MASS) to retrieve photometric and astrometric information of stellar objects. To these objects, we applied colour and proper motion filters, together with an effective temperature cutoff, aimed at separating hot subdwarfs from other blue objects such as white dwarfs, cataclysmic variables or main sequence OB stars. As a result, we obtained 437 new, uncatalogued hot subdwarf candidates. Based on previous results, we expect our procedure to have an overall efficiency of at least 80 per cent. Visual inspection of the 68 candidates with SDSS spectrum showed that 65 can be classified as hot subdwarfs: 5 sdOs, 25 sdOBs and 35 sdBs. This success rate above 95 per cent proves the robustness and efficiency of our methodology. The spectral energy distribution of 45 per cent of the subdwarf candidates showed infrared excesses, a signature of their probable binary nature. The stellar companions of the binary systems so detected are expected to be late-type main sequence stars. A detailed determination of temperatures and spectral classification of the cool companions will be presented in a forthcoming work.