Detection of MAXI J0637-430 by the Regolith X-Ray Imaging Spectrometer (REXIS) Onboard OSIRIS-REx

ATel #13594; B. Allen, J. Grindlay, D. Hoak, J. Hong, D. Guevel (Center for Astrophysics / Harvard & Smithsonian), M. Lambert, R. P. Binzel, R. Masterson, A. Cummings (MIT), L. Lim (GSFC), D. Lauretta, B. Boynton (University of Arizona)
on 28 Mar 2020; 07:41 UT
Credential Certification: Branden Allen (ballen@cfa.harvard.edu)

Tweet

At 11:00 UT on November 11, 2019 MAXI J0637-430 (Negoro et al., ATEL #13256) was serendipitously detected by the REgolith X-Ray Imaging Spectrometer (REXIS) onboard the Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) asteroid sample return mission while conducting observations of the near earth asteroid (101995) Bennu. The REXIS instrument is a coded aperture X-Ray telescope with a detector plane consisting of 2 × 2 array of CCDID-41 CCDs (modified Suzaku CCDs) sensitive between 0.3 and 10 keV (further instrument details may be found in Masterson et al. 2018 and Allen et al. 2013).

The REXIS observations were carried out between November 11, 2019 and November 25, 2019 while in orbit around Bennu with a mean orbital radius and period of 1.5 km and 30 hours, respectively. Between these dates MAXI J0637-430 was visible for approximately 4 hours per orbit off the limb of the asteroid within the partially coded field of view.

• Integration over all REXIS observations following the outburst yields a detection with a SNR of 14.
• During the course of observation, the source flux reduced by a factor of 2 in the 0.5 - 4 keV energy band.
• The calculated centroid is (J2000): (RA / DEC)= (06:36:12.46 / -42:52:56.29)
  with an estimated 95% error circle of 5'. The Swift-XRT reported 90% error circle (Kennea, et al. ATEL #13257) is coincident with this detection region and the position derived from the Swift-UVOT lies 2.34' away from REXIS centroid.

This material is based upon work supported by the National Aeronautics and Space Administration under Contract NNM10AA11C issued through the New Frontiers Program. The computations in this ATEL were run on the FASRC Cannon cluster supported by the FAS Division of Science Research Computing Group at Harvard University.