Spectroscopic and Photometric Observations of Unidentified Ultraviolate Variable Objects in GUVV-2 Catalog

TL;DR

This study uses NUV-optical color diagrams and spectroscopic observations to classify unidentified ultraviolet variable sources from the GUVV-2 catalog, confirming the method's effectiveness in initial classification.

Contribution

It introduces a spectroscopic follow-up approach to validate a NUV-optical classification method for UV variable sources in the GUVV-2 catalog.

Findings

37 sources spectroscopically identified, including stars and an AGN.

RR Lyrae candidates confirmed through light curves and color analysis.

NUV/optical color-color diagrams effectively classify UV variable sources.

Abstract

An NUV-optical diagram made for sources from the secend Galaxy Evolution Explorer (GALEX) Ultraviolet Variability (GUVV-2) Catalog provide us a method to tentatively classify the unknown GUVV2 sources by their NUV-optical magnitudes. On the purpose of testing the correctness and generality of the method, we carry out a program on the spectroscopic observations of the unidentified GUVV2 sources. The spectroscopic identification for these 37 sources are 19 type -A to -F stars, 10 type -G to -K stars and 7 M dwarf stars together with an AGN. We also present the light curves in R-band for two RR Lyrae star candidates selected from the NUV-optical diagram, both of which perform cyclic variations. Combining there light curves and colors, we classify them as RR Lyrae stars. To confirm the results, we shows a color-color diagram for the 37 newly spectroscopically identified objects compared with the previously identified ones, which manifests good consistence with our former results, indicating that the ultroviolet variable sources can be initially classified by their NUV/optical color-color diagram.