Discovery of the New X-Ray Transient MAXI J1807+132: A Candidate of a Neutron Star Low-mass X-Ray Binary

Megumi Shidatsu, Yutaro Tachibana, Taketoshi Yoshii, Hitoshi Negoro, Taiki Kawamuro, Wataru Iwakiri, Satoshi Nakahira, Kazuo Makishima, Yoshihiro Ueda, Nobuyuki Kawai, Motoko Serino, Jamie Kennea

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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 maximum intensity (∼10 mCrab in 2-10 keV), and then gradually faded in ∼10 days by more than one order of magnitude. Time-averaged Swift/X-ray Telescope 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 ∼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.

Original languageEnglish (US)
Article number155
JournalAstrophysical Journal
Volume850
Issue number2
DOIs
StatePublished - Dec 1 2017

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Shidatsu, M., Tachibana, Y., Yoshii, T., Negoro, H., Kawamuro, T., Iwakiri, W., Nakahira, S., Makishima, K., Ueda, Y., Kawai, N., Serino, M., & Kennea, J. (2017). Discovery of the New X-Ray Transient MAXI J1807+132: A Candidate of a Neutron Star Low-mass X-Ray Binary. Astrophysical Journal, 850(2), [155]. https://doi.org/10.3847/1538-4357/aa93f0