An X-ray Flare from eta Carinae as seen by NICER

ATel #13327; Michael F. Corcoran (CUA & NASA/GSFC), Kenji Hamaguchi (UMBC & NASA/GSFC), Keith Gendreau (NASA/GSFC), Zaven Arzoumanian (NASA/GSFC), David Espinoza (CUA), A. F. J. Moffat (U. Montreal)
on 3 Dec 2019; 12:39 UT
Credential Certification: Michael Corcoran (michael.f.corcoran@nasa.gov)

Subjects: X-ray, Binary

Referred to by ATel #: 13329

Monitoring of the 2-10 keV colliding emission X-ray spectrum of the extremely massive colliding wind binary eta Carinae by the Neutron Star Interior Composition Explorer (NICER) shows that the system is undergoing an X-ray flare, similar to those strong X-ray variations seen in other orbital cycles near this orbital phase (Moffat & Corcoran 2009, ApJ 707, 693). The flare began near 2019 November 15 at a 2-10 keV flux of 2e-10 ergs/cm2/s, reaching a flux of 2.58e-10 ergs/cm2/s on 2019 November 28. An observation on 2019 November 29 showed that the flux did not significantly increase, suggesting that the flare may have reached its peak. Additional photometric and/or spectrometric observations of eta Car are encouraged. The NICER monitoring will last at least until 2020 March 1. Eta Car's X-ray minimum is expected to begin on 2020 February 13, according to the ephemeris of Corcoran et al. (2017, ApJ 838, 45). This is about four days before periastron passage, using the ephemeris of Teodoro et al. (2016, ApJ 819, 131).