Abstract
Context.The Small Magellanic Cloud (SMC) hosts many known high-mass X-ray binaries (HMXBs), and all but one (SMC X-1) have a Be companion star. Through the calibration and verification phase of eROSITA on board the Spektrum-Roentgen-Gamma (SRG) spacecraft, the Be/X-ray binary XMMU J010429.4-723136 was in the field of view during observations of the supernova remnant, 1E0102.2-7219, used as a calibration standard.Aims.We report timing and spectral analyses of XMMU J010429.4-723136 based on three eROSITA observations of the field, two of which were performed on 2019 November 7-9, with the third on 2020 June 18-19. We also reanalyse the OGLE-IV light curve for that source in order to determine the orbital period.Methods.We performed a Lomb-Scargle periodogram analysis to search for pulsations (from the X-ray data) and for the orbital period (from the OGLE data). X-ray spectral parameters and fluxes were retrieved from the best-fit model.Results.We detect, for the first time, the pulsations of XMMU J010429.4-723136 at a period of -164 s, and therefore designate the source as SXP 164. From the spectral fitting, we derive a source flux of ~1 × 10−12erg s−1cm−2for all three observations, corresponding to a luminosity of ~4 × 1035erg s−1at the distance of the SMC. Furthermore, reanalysing the OGLE light curve, including the latest observations, we find a significant periodic signal that we believe is likely be the orbital period; at 22.3 days, this is shorter than the previously reported values. TheSwift/XRTlight curve, extracted from two long monitorings of the field and folded at the same period, suggests that a modulation is also present in the X-ray data.
Highlights
High-mass X-ray binaries (HMXBs) are binary systems composed of an early-type star and a compact object that is either a neutron star or a black hole
We report the discovery of X-ray pulsations for XMMU J010429.4−723136 with a period of 164 s and rename the source SXP 164 following the terminology first proposed by Coe et al (2005)
We report the discovery of the pulse period (164 s) and possibly the orbital period (22 d) of a known Be/X-ray binary in the Small Magellanic Cloud (SMC)
Summary
High-mass X-ray binaries (HMXBs) are binary systems composed of an early-type star and a compact object that is either a neutron star or a black hole (occasionally a white dwarf). Be or B[e]-type stars are a subset of B-type stars where one or more Balmer emission lines are found in the optical spectrum They are believed to possess an equatorial decretion disc, possibly causing regular X-ray outbursts at periastron passage of the compact object due to enhanced mass accretion A period of 29.75 d was found in the data covering the short time interval MJD 55650–56100 (and after some detrending) This is somewhat lower than the strong modulation of 37.15±0.02 d claimed by Rajoelimanana et al (2011a) and associated later by Schmidtke. We report the discovery of X-ray pulsations for XMMU J010429.4−723136 with a period of 164 s and rename the source SXP 164 following the terminology first proposed by Coe et al (2005) (where SXP stands for Small Magellanic Cloud X-ray Pulsar, followed by the pulse period in seconds to three significant figures). We report the detection of a strong signal at 22.3 d in the OGLE-IV light curve that we interpret as the possible orbital period
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
