Swift observations of the X-ray brightening of U Sco
ATel #15465; K. L. Page and J. P. Osborne (U. Leicester)
on 24 Jun 2022; 08:11 UT
Credential Certification: Kim Page (kpa@star.le.ac.uk)
The Neil Gehrels Swift Observatory has been monitoring U Scorpii since
the discovery of the most recent eruption by M. Moriyama on 2022 June
6.720 (vsnet alert 26798). The supersoft emission was first seen by
Swift on 2022 June 16 (9.1 days after optical peak; ATel #15423), at a
count rate of 0.022 +/- 0.004 count s-1 (ATel #15438).
Following this first detection, the supersoft emission plateaued
around this count rate (in the range 0.01-0.05 count s-1)
between days 9.1 and 14.6. On June 22 (day 15.1), the count rate was
found to brighten to a level of 0.10 +/- 0.01 count s-1,
further increasing to 0.31 +/- 0.03 s-1 by day 15.3, and
remaining around this level until the most recent observation on day 16.4.
Mean spectra for days 9.1-14.6 and 15.3-16.4 are entirely consistent
with each other, with blackbody temperatures of 26 +/- 4 eV, and
NH = 4.7 x 1021 cm-2, above the
interstellar medium column density in this direction (1.2 x
1021 cm-2).
Swift observations continue, and we thank the Swift PI and his
deputies for approving these ongoing observations, as well as the
science operations team for their work in scheduling them.
