Decreasing Flux of LS V +44 17 from 25 March 2023 through 3 April 2023
ATel #16014; Anna Gaishin, McKinley Brumback, Elise Kesler, Nathan Morrow, Matthew Wanink (University of Michigan)
on 27 Apr 2023; 14:08 UT
Credential Certification: McKinley Brumback (brumback@umich.edu)
Subjects: X-ray, Binary, Neutron Star
LS V +44 17 (also called RX J0440d9+4431) is a high mass Be X-ray binary pulsar, residing 3.3 +/- 0.5 kpc away (Reig et al. 2005). It last outburst in 2010 (Usui el al. 2012), but has recently outburst again, starting in late 2022. We report on four Neil Gehrels Swift Observatory XRT exposures to monitor the fading of this outburst.
All observations assumed an absorbed power law model constrained to the 0.7-8 keV range, as this was where the data was above the background and of good quality. Finally, we decided to neglect the intermediate observation 00089583027, taken 28 March 2023, as the source was located far off-axis.
Observation 00089583026, dated 25 March 2023, yielded 21697 net photons over an exposure of 726.31 seconds. The best fit model had a photon index of 0.70 +/- 0.06 and an N_H of (0.83 +/- 0.09)x10^22 cm^2. And finally, we calculated a flux of (1.69 +/- 0.03)x10^-9 erg/cm^2/s, which indicates a luminosity of (2.20 +/- 0.04)x10^36 erg/s.
Observation 00089583028, dated 31 March 2023, yielded 9243 net photons over an exposure of 861.13 seconds. The best fit model had a photon index of 0.81 +/- 0.06 and an N_H of (0.91 +/- 0.09)x10^22 cm^2. And finally, we calculated a flux of (1.48 +/- 0.02)x10^-9 erg/cm^2/s, which indicates a luminosity of (1.92 +/- 0.03)x10^36 erg/s.
Observation 00089583029, dated 03 April 2023, yielded 20589 net photons over an exposure of 926.10 seconds. The best fit model had a photon index of 0.82 +/- 0.06 and an N_H of (0.87 +/- 0.09)x10^22 cm^2. And finally, we calculated a flux of (1.29 +/- 0.02)x10^-9 erg/cm^2/s, which indicates a luminosity of (1.68 +/- 0.03)x10^36 erg/s.
Overall, we can see that LS V +44 17 is dimming substantially as it leaves an outburst, which we expect as the source continues to fade.
References
Reig, P., Negueruela, I., Fabregat, J., Chato, R., & Coe, M. J. 2005, A&A, 440, 1079
Usui, R., Morii, M., Kawai, N., et al. 2012, Publications of the Astronomical Society of Japan, 64, 79
