GCN Circular 34215

W.Iwakiri (Chiba Univ.), M.Serino (AGU),  K. Gendreau, Z. Arzoumanian (NASA/GSFC):

We report the non-detection of MAXI/GSC of the neutrino event IceCube-230707A (Lincetto et al., GCN Circ 34163) and the upper limits of the X-ray flux of Swift J1753.5-0127 located in the error region of the neutrino event by NICER.
At 16:25:43 UT on 2023-07-07 (about 33 min before the event trigger)) and 17:58:40 UT on 2023-07-07 (about 60 min after the event trigger),  MAXI/GSC scanned the error region of the event. No significant excess emission was detected from the region. A typical 1-sigma averaged upper limit in one scan observation is 20 mCrab at 2-20 keV. 

We have also observed Swift J1753.5-0127, located in the 90% uncertainty region of IceCube-230707A, by NICER. Swift J1753.5-0127 is a candidate of a black hole in X-ray binary system, discovered in an outburst in 2005(ATel #546). The outburst lasted in 2017 (ATel #10562), and after that no significant activity has been reported. To search for any reactivity of Swift J1753.5-0127 associated with the high-energy neutrino signal, NICER observed the source from July 9th 19:34 UT to July 10th 02:01 UT with 3.9 ksec exposure. There was no significant X-ray signal. The estimated 3-sigma flux upper limit of Swift J1753.5-0127 in the 0.6-10 keV band is about 1.8 x 10^-12 erg/sec/cm^2 using an absorbed power-law model with photon index 1.7 and a column density nH of 2 x 10^21 cm^-2 (Plotkin et al., 2017). Assuming the distance of 8 kpc, the X-ray luminosity corresponds to 1.5 x 10^34 erg/s. The result indicates that Swift J1753.5-0127 is in quiescence.

NICER is a 0.2–12 keV X-ray telescope operating on the International Space Station. The NICER mission and portions of the NICER science team activities are funded by NASA.

(Reference: Plotkin et al., 2017, ApJ, 848, 92)