Meet the family - the catalog of known hot subdwarf stars

TL;DR

This paper compiles a comprehensive catalog of 5613 hot subdwarf stars with multi-band data, enabling improved selection and analysis, including a kinematic study revealing halo subdwarfs and differences from cluster populations.

Contribution

The authors created a detailed catalog of hot subdwarfs integrating various data sources, and demonstrated its use in spectral and kinematic analysis, including halo star identification.

Findings

Identified 78 halo hot subdwarfs with Gaia data.

Compared field and cluster hot subdwarfs, noting differences in He-sdOB fractions.

Provided a basis for future homogeneous all-sky hot subdwarf catalog construction.

Abstract

In preparation for the upcoming all-sky data releases of the Gaia mission, we compiled a catalog of known hot subdwarf stars and candidates drawn from the literature and yet unpublished databases. The catalog contains 5613 unique sources and provides multi-band photometry from the ultraviolet to the far infrared, ground based proper motions, classifications based on spectroscopy and colors, published atmospheric parameters, radial velocities and light curve variability information. Using several different techniques, we removed outliers and misclassified objects. By matching this catalog with astrometric and photometric data from the Gaia mission, we will develop selection criteria to construct a homogeneous, magnitude-limited all-sky catalog of hot subdwarf stars based on Gaia data. As first application of the catalog data, we present the quantitative spectral analysis of 280 sdB and sdOB stars from the Sloan Digital Sky Survey Data Release 7. Combining our derived parameters with state-of-the-art proper motions, we performed a full kinematic analysis of our sample. This allowed us to separate the first significantly large sample of 78 sdBs and sdOBs belonging to the Galactic halo. Comparing the properties of hot subdwarfs from the disk and the halo with hot subdwarf samples from the globular clusters $\omega$ Cen and NGC 2808, we found the fraction of intermediate He-sdOBs in the field halo population to be significantly smaller than in the globular clusters.