INTEGRAL follow-up of the 4U 1730-22 outburst
ATel #14896; . Ferrigno, V. Savchenko, E. Bozzo (ISDC/University of Geneva, CH), S. A. Grebenev (IKI, RU), J. Wilms (Remeis-Observatory and ECAP, FAU Erlangen-Nuernberg, D), L. Ducci (IAAT, De) E. Kuulkers (ESTEC/ESA, NL) on behalf of the Galactic bulge monitoring team
on 6 Sep 2021; 16:23 UT
Credential Certification: Carlo Ferrigno (Carlo.Ferrigno@unige.ch)
Subjects: X-ray, Gamma Ray, Neutron Star, Transient
After the report of renewed activity from the low mass X-ray binary 4U 1730-22 (CXOU J173357.5-220156) using MAXI, Swift/XRT, NICER, and INTEGRAL data (ATels #14683, #14686, #14757, #14769, #14870), we followed its evolution during the repeated observation of the Galactic Centre under the programs led by PIs Wilms, Kuulkers, & Grebenev.
We extracted preliminary ISGRI and JEM-X1 spectra selecting pointings with off-axis angles of at most 12 degrees for ISGRI and 4 degrees for JEM-X. We combined the spectra from each 2.7-days-long satellite revolutions between 2021-08-07 16:49:02 and 2021-08-31 13:16:45 and fitted each spectrum with a powerlaw, which described the data satisfactorily a (at 99% confidence level) whenever the spectra had enough signal to noise ratio. The power-law photon index does not show any trend and has a weighted mean value of 2.14±0.04. The hard X-ray flux shows a linear decay that can be described as flux (20-100keV) = 340±7 + ( -7.9±0.7) (t - MJD 59434.3061 ) 10-12 erg/s/cm2.
Further observations of the Galactic centre region are scheduled for the coming weeks.
