Swift X-Ray and UV Observations of six Gaia Binaries supposedly containing a Neutron Star

TL;DR

This study used Swift Observatory to observe six Gaia binaries suspected of containing neutron stars, detecting X-ray and UV emissions in some, supporting the neutron star hypothesis in these systems.

Contribution

First X-ray and UV observational campaign targeting Gaia binaries with potential neutron star components, providing evidence supporting their nature.

Findings

Detection of X-ray emission from one source with possible accretion signatures.

X-ray flux upper limits established for the remaining targets.

Results support the presence of neutron stars in these systems.

Abstract

Recent observations have led to the discovery of numerous optically selected binaries containing an undetected component with mass consistent with a compact object (neutron star or white dwarf). Using the the Neil Gehrels Swift Observatory we have carried out X-ray and UV observations of a small sample of these binaries. Four systems are wide (with orbital period P>300 d), and they were chosen because of their small distance (d<250 pc) and the mass of the collapsed component favoring a neutron star. Two other are compact systems (P<0.9 d), with convincing evidence of containing a neutron star. The source 2MASS J15274848$+$3536572 was detected in the X-ray band, with a flux of 5E-13 erg/cm2/s and a spectrum well fitted by a power law or a thermal plasma emission model. This source also showed an UV (2200 Angstrom) excess, which might indicate the presence of mass accretion. For the other targets we derived X-ray flux upper limits of the order of 1E-13}$ erg/cm2/s . These results are consistent with the hypothesis that the collapsed component in these six systems are neutron stars.