Identification of 5 Interacting Binaries in the Galactic Bulge Survey

TL;DR

This study identifies and classifies five X-ray sources in the Galactic Bulge Survey using optical lightcurves and spectroscopy, revealing their nature as various types of interacting binaries with specific variability characteristics.

Contribution

The paper provides the first optical follow-up and classification of five X-ray sources in the Galactic Bulge Survey, highlighting their variability and binary nature.

Findings

CX5 is an Intermediate Polar with a 2.1-hour period.

CX18 experienced two dwarf nova outbursts.

CX28 and CX37 are likely Intermediate Polars.

Abstract

We present optical lightcurves, spectroscopy, and classification of five X-ray sources in the Chandra Galactic Bulge Survey [CXOGBS J174009.1-284725 (CX5), CXOGBS J173935.7-272935 (CX18), CXOGBS J173946.9-271809 (CX28), CXOGBS J173729.1-292804 (CX37), CXOGBS J174607.6-261547 (CX561)]. These objects were selected based on bright optical counterparts which were quickly found to have emission lines in their optical spectra. This paper presents an illustration of GBS optical follow-up, targeting emission line objects. Of these five objects, four exhibit photometric variability in the Sloan r' band. CX5 shows a tentative period of 2.1 hours and is clearly an Intermediate Polar (IP). CX28 and CX37 both exhibit flickering with no clear period. Both are suggested to also be IPs. CX18 was observed to undergo 2 dwarf nova outbursts. Finally, CX561 shows no detectable variability, although its characteristics would be consistent with either a quiescent Low Mass X-ray Binary or Cataclysmic Variable.