TY - JOUR
T1 - X-ray observations of two candidate symbiotic binaries in the galactic bulge
AU - Wetuski, Joshua
AU - Hynes, R. I.
AU - Maccarone, T. J.
AU - Heinke, C.
AU - Torres, M. A.P.
AU - Jonker, P. G.
AU - Britt, Christopher T.
AU - Steeghs, D.
AU - Nelemans, G.
N1 - Publisher Copyright:
© 2021 The Author(s).
PY - 2021/10/1
Y1 - 2021/10/1
N2 - 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.
AB - 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.
KW - Binaries: Spectroscopic
KW - Binaries: Symbiotic
KW - X-rays: Binaries
UR - http://www.scopus.com/inward/record.url?scp=85118187920&partnerID=8YFLogxK
U2 - 10.1093/mnras/stab2139
DO - 10.1093/mnras/stab2139
M3 - Article
AN - SCOPUS:85118187920
SN - 0035-8711
VL - 506
SP - 5619
EP - 5628
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 4
ER -