NICER observations of the 2018 outburst of the black hole candidate MAXI J1727-203

Abstract

MAXI J1727-203 is a new transient discovered in June, 5 2018, and due to its spectral properties at the beginning of the outburst it was identified as a black hole candidate. MAXI J1727 has been monitored with Neutron Star Interior Composition Explorer (NICER) on almost daily basis since the beginning of the outburst. In this talk we will present the spectral and timing analysis of ~4 months of observations (more than 75 observations). Preliminary results suggest a significant detection of a cool disk (~0.2 keV) and a strong hard component at the end of the outburst. We will show that MAXI J1727 might have undergone the soft-to-hard transition at 0.5-10 keV luminosities ~ 1e36 erg/sec. This source is the the 3rd system in which we have detected the soft-to-hard transition at such low X-ray luminosities