Discovery of the new X-ray transient MAXI J1807+132: a Candidate of a Neutron Star Low-mass X-ray binary

Abstract

We report on the detection and follow-up multi-wavelength observations of the new X-ray transient MAXI J1807+132 with the MAXI/GSC, Swift, and ground-based optical telescopes. The source was first recognized with the MAXI/GSC on 2017 March 13. About a week later, it reached the maximum intensity ($\sim$10 mCrab in 2-10 keV), and then gradually faded in $\sim$10 days by more than one order of magnitude. Time-averaged Swift/XRT spectra in the decaying phase can be described by a blackbody with a relatively low temperature (0.1-0.5 keV), plus a hard power-law component with a photon index of $\sim$2. These spectral properties are similar to those of neutron star low-mass X-ray binaries (LMXBs) in their dim periods. The blackbody temperature and the radius of the emission region varied in a complex manner as the source became dimmer. The source was detected in the optical wavelength on March 27-31 as well. The optical flux decreased monotonically as the X-ray flux decayed. The correlation between the X-ray and optical fluxes is found to be consistent with those of known neutron star LMXBs, supporting the idea that the source is likely to be a transient neutron star LMXB.

13 pages, 11 figures, accepted for publication in ApJ

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Cited by in corpus (4)

• The complex evolution of the X-ray binary transient MAXI J1807+132 along the decay of its discovery outburst
• Unveiling the nature of compact object in the LMXB MAXI J1957+032 using Swift-XRT
• Evolution of the Accretion Disk and Corona During the Outburst of the Neutron Star Transient MAXI J1807+132
• The Peculiar X-ray Transient Swift J0840.7-3516: an Unusual Low Mass X-ray Binary or a Tidal Disruption Event?