Swift XRT follow-up observation of 1E 1145.1-6141

ATel #15762; Nicola La Palombara
on 15 Nov 2022; 17:54 UT
Credential Certification: Nicola La Palombara (nicola.lapalombara@inaf.it)

Tweet

We report on a follow-up observation of the transient X-ray pulsar 1E 1145.1-6141, performed with Swift/XRT on November 12th. This source was first detected in outburst on October 31st with INTEGRAL JEM-X, which observed it at a flux level of 11+/-1 mCrab in the energy range 3-10 keV (ATel #15741). Then, on November 5th the source was observed again with JEM-X, at a lower flux level (6.6+/-1 mCrab). Moreover, at the same epoch the source was observed also with NICER, which performed a spectral characterization (ATel #15750). The source spectrum was described with an absorbed power-law, with column density Nh = (7.8+/-3)x10^22 cm^(-2) and photon index = 2.3+/-0.7. The estimated source flux was 3.8x10^(-11) erg/cm2/s. The Swift follow-up observation was performed between 2022-11-12T21:38:00 and 2022-11-12T22:08:00, for a total exposure time of 1200 s. The XRT spectrum can be described with an absorbed power-law, with a fixed interstellar column density Nh = 1.3x10^22 cm^(-2) and photon index = -0.3 (+1.9/-1.1). The estimated source flux is 4.0(+2.7/-2.1)E-12 erg/cm2/s in the energy range 03-10 keV. This value is significantly lower than the flux estimated with NICER one week before, thus implying that the decline of the source outburst has further proceeded also after the NICER observation. We thank the Swift team at PennState University for the implementation of the follow-up observation, and the UK Swift Science Data Centre for providing the XRT products.