NICER observation list: Target ID 254201

Abstract

4U 1957+11 is one of the few persistently active black hole candidates. Although we do not know its mass, distance, or inclination, the fact that it is apparently always in a thermal-dominated state with extremely high disk temperature, yet very low normalization, suggests a very rapidly rotating black hole. Furthermore, it has an extremely low column, allowing an extremely good view of the soft X-ray spectrum accessible to NICER. Its high disk temperature also places the peak of the disk spectrum in the bandpass of both NICER and NuSTAR. Thus, it becomes an ideal test bed of modern disk atmosphere models. We propose a series of joint NICER/NuSTAR observations that we will analyze as a whole, in order to measure this system's unknown black hole parameters.
Obsid RA DEC l b Start End Exposure Number of
Modules
Number of
Processing
Status of
Processing
Date of
Processing
Public
date
2542010101 299.851 11.710 51.309 -9.330 58602.6067 58602.9407 3683.0 52 3 VALIDATED 58605.6 58616
2542010102 299.851 11.712 51.311 -9.329 58602.9940 58603.3905 3395.0 52 3 VALIDATED 58606.6 58617
2542010201 299.850 11.709 51.308 -9.330 58638.8874 58638.9785 4185.1 52 2 VALIDATED 58643.0 58652
2542010202 299.850 11.708 51.307 -9.331 58639.0168 58639.2856 5721.0 52 2 VALIDATED 58643.9 58653
2542010301 299.852 11.710 51.311 -9.331 58683.3940 58683.9310 14171.0 52 2 VALIDATED 58688.7 58697
2542010401 299.852 11.709 51.309 -9.331 58736.0847 58736.5005 10060.0 52 3 VALIDATED 58740.6 58750
2542010501 299.851 11.709 51.308 -9.330 58776.5365 58776.9437 11950.0 52 2 VALIDATED 58781.7 58790