Swift observations of the Neutron Star binary candidate 2MASS J15274848+3536572
ATel #15736; Sandro Mereghetti (INAF/ IASF-Milano), Boris Sbarufatti (INAF/OAB), Aldo Treves (Università dellâInsubria)
on 2 Nov 2022; 16:37 UT
Credential Certification: Boris Sbarufatti (boris.sbarufatti@inaf.it)
Swift has observed the nearby (d~118 pc) single-line spectroscopic binary 2MASS J15274848+3536572, which, according to Lin et al. 2022 (arXiv:2210.11360), might consist of a main-sequence K type star with a radio-quiet and X-ray dim neutron star companion.
The XRT data have been taken from 2022-10-30T10:56:29 to 2022-10-31T00:01:52 UT in Photon Counting mode (total exposure 3.2 ks). Inside the error circle of the ROSAT source 1RXS J152748.8+353658 (error radius 19â) only one X-ray source is detected, with a count rate of 8.8e-3 counts/s in the 0.3 - 10 keV energy range.
The coordinates of the XRT source, (R.A=15h 27m 48.52s, DEC.=+35º 36' 58.8", with uncertainty of 3.6") are at 1.6" from the position of 2MASS J15274848+3536572, confirming that the X-ray emission previously detected by ROSAT is associated with this binary system.
Due to the small number of detected counts the spectrum is poorly constrained. With the interstellar absorption fixed to NH=1e19 cm^-2 and using the Cash statistics, we obtained a good fit with a power law of photon index 2.0+/-0.5 and flux 3.4(+1.6,-1.1)e -13 ergs/cm^2/s (29.9 cstat using 25 bins).
A slightly worse, but still acceptable fit, was obtained with a thermal plasma model (Mekal) with kT = 2.1(+5.4,-0.8) keV and flux 2.7(+1.2,-0.9) ergs/cm^2/s (31.2 cstat, 25 bins).
All the fluxes given above refer to the 0.3 - 10 keV energy range. All quote errors are at a 90% confidence level.
We note that the flux of the Swift/XRT source is consistent with coronal emission from the K type star present in the system, however, also in view of the rather hard X-ray spectrum, the presence of emission from the putative compact companion cannot be excluded.
