Preliminary Result on MAXI J1348-630 using Swift data: Detection of 0.56 Hz QPO and Mass Estimation

ATel #12505; Arghajit Jana, Dipak Debnath, Debjit Chatterjee, Sandip K. Chakrabarti, Kaushik Chatterjee, Riya Bhowmick (Indian Centre for Space Physics, 43 Chalantika, Garia St. Rd., Kolkata, 700084, India)
on 15 Feb 2019; 10:29 UT
Credential Certification: Dipak Debnath (dipakcsp@gmail.com)

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MAXI/GSC discovered a new X-ray transient MAXI J1348-630 on 26th Jan., 2019 at (R.A., Dec) = (207.053 deg, -63.068 deg) = (13 48 12, -63 04 04) (J2000) (Yatabe et al., Atel #12425). Follow up multi-wavelength observations are made by Swift, INTEGRAL, NICER, ATCA, optical and radio telescopes (e.g., ATels #12430, #12434, #12439, #12441,, #12447, #12457, #12497). Optical counterpart of the source was identified by Denisenko et al. (ATel #12430). Based on NICER observation, Sanna et al. (ATel #12447) reported the source as a probable black hole candidate. We make temporal and spectral study of MAXI J1348-630 using Swift XRT and BAT data during its initial phase of the outburst from 2019 Jan. 26 to Jan. 29. On 2019 Jan. 29, we detect a prominent type-C QPO of frequency 0.56 +/- 0.02 Hz in Swift/XRT data. Our spectral analysis with Two Component Advective Flow (TCAF) solution based fits file in XSPEC (Debnath et al. 2014, 2015) suggests that during this phase of the outburst source was in low-hard state. There was dominance of the sub-Keplerian halo rate over the Keplerian disk rate and presence of strong shock at a location far away from the black hole (>190 Schwarzschild radius). From spectral analysis, we also estimate normalization independent probable mass of the source to be in the range of 8.5-11 M-Sun.