Follow up observations of GX 339-4 with AstroSat
ATel #14400; Nazma Husain(Jamia Millia Islamia), Sneha Prakash Mudambi(CHRIST (Deemed to be University)), Akash Garg(Jamia Millia Islamia), Ranjeev Misra(IUCAA), Somasri Sen(Jamia Millia Islamia), Bari Maqbool (Islamic University of Science and Technology)
on 18 Feb 2021; 10:12 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Bari Maqbool (bari@iucaa.in)
Subjects: X-ray, Binary, Black Hole, Transient
A ToO observation was undertaken of the low mass black hole X-ray binary GX 339-4 with AstroSat on 2021-02-13(MJD59258) starting from 00:54:22 to 20:06:01 for about 30 ksecs. This was a follow up to the reports by NICER(Atel#14384), SWIFT(ATel #14351, #14352), MAXI(ATel #14351,#14367), NuSTAR(ATel #14352), INTEGRAL(ATel #14354) and MeerKAT(ATel #14336) indicating an onset of an outburst.
The spectra were modeled with disk and Comptonization components along with Gaussian Iron line emission in the energy range 0.5-50.0 keV. The unabsorbed flux was found to vary within 5.64e-9 to 6.52e-9 erg s-1cm-2, while the power-law index changed from 1.53 to 1.59. The inner disc temperature was found to be around KTin ~ 0.25 keV and the absorption column density was estimated to be ~ 0.46e22cm-2.
We carried out timing analysis in the energy range 3.0-80.0 keV. The power spectrum showed the presence of a low frequency QPO with r.m.s ~ 6.4% and having a centroid frequency 0.11+0.01-0.01 Hz with width 0.063+0.022-0.033 Hz.
Further follow up observations are encouraged. We thank the AstroSat Time Allocation team and operations team for the quick response to the ToO proposal.
