X-ray observations of two candidate symbiotic binaries in the galactic bulge

Joshua Wetuski, R. I. Hynes, T. J. Maccarone, C. Heinke, M. A.P. Torres, P. G. Jonker, Christopher T. Britt, D. Steeghs, G. Nelemans

Research output: Contribution to journalArticlepeer-review


This paper analyses X-ray observations by the Chandra X-ray Observatory of CXOGBS J174614.3-321949 (CXB3) and CXOGBS J173620.2-293338 (CX332), two symbiotic binary star candidates identified by the Galactic Bulge Survey. Using new Chandra observations, we improved their X-ray positional uncertainties to 0.24 and 0.92 arcsec, respectively, confidently associating them with single optical counterparts. In particular, new observations of symbiotic X-ray candidate CX332 further solidify confidence in its coincidence with a carbon star. We demonstrate X-ray variability in both targets with a more recent observation of CX332 showing a decrease in brightness by a factor of 30, while CXB3 observations show it usually in a quiescent state with a factor-of-6 flare-like event in the final observations. In a combined spectral fit for CXB3, we find an NH value of ∼ (2-3) × 1022cm-2 >with a Γ value of 1.5+0.2-0.2 for a power-law fit and 10.6-2.9}+5.7 keV for an apec fit and an estimated luminosity of ∼8.4 × 1032 erg s-1. Spectra of CXB3 would be consistent with thermal emission as seen in white dwarf symbiotic systems, but the high X-ray luminosity in the light curve is more typically seen in symbiotic X-ray binary systems. Optical spectra of both objects taken with Gemini GMOS indicate CXB3 as containing an M-type star and CX332 having a carbon star counterpart. Both targets show at most marginal evidence of H α emission favouring a symbiotic X-ray binary interpretation for both sources, though we cannot rule out a white dwarf for either case.

Original languageEnglish
Pages (from-to)5619-5628
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - Oct 1 2021


  • Binaries: Spectroscopic
  • Binaries: Symbiotic
  • X-rays: Binaries


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