Multi-wavelength observation of MAXI J1348-630 during the recent outburst using ALMA/Chandra/NuSTAR


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We studied the multi-wavelength timing and spectral properties of the high mass X-ray binary MAXI J1348$-$630 during two successive outbursts of April and June 2019 using ALMA, Swift, Chandra, NuSTAR and NICER. The position of the source was measured by Chandra (RA=13h48m12.878s, Dec=$-$63$^{circ}$1628.85) with enhanced accuracy. The soft X-ray spectrum (1$-$6 keV) was intensively studied using Chandra/HETG from which multiple absorption-features corresponding to Fe XXII, Fe XXIII, Si XII, Cl XVI, S XV, Ar XVIII lines and the emission features corresponding to Fe XXI, Fe XXIII, Ar XVI lines were detected. We studied the first broadband spectrum for this black hole that included fluxes in radio, optical, ultraviolet and X-ray energy bands using data from ALMA (band 3, 4, 6 and 7; 89.56$-$351.44 GHz) and swift (UVOT and XRT). The broadband study suggested that the source was accompanied by strong blackbody radiation from the disk associated with weak synchrotron emission from the compact jets. The X-ray spectrum was also studied using NuSTAR in the range of 3$-$78 keV. We studied the evolution of spectral parameters using NuSTAR observations (from MJD 58655 to MJD 58672) when the source remained in the canonical hard state during the outburst of June 2019. We detected two type-C QPOs during the outburst of June 2019 with decreasing centroid frequencies from 0.82 Hz to 0.67 Hz and decreasing RMS amplitude from 7.6 per cent to 2.1 per cent. The hardness ratio showed significant variation during the outburst of April 2019 but remained almost constant during the outburst of June 2019. The spectral evolution in the hardness intensity diagram was studied during the outbursts.

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