MAXI J1733-222 / 4U 1730-22: Updated Swift localization
ATel #14688; J. A. Kennea (PSU), P. A. Evans (U Leicester), A. Bahramian (ICRAR), A. P. Beardmore (U Leicester), H. A. Krimm (CRESST/GSFC/USRA), P. Romano (INAF-IASFPA), K. Yamaoka (Nagoya U.), M. Serino (RIKEN), H. Negoro (Nihon U.)
on 9 Jun 2021; 09:56 UT
Credential Certification: Jamie A. Kennea (kennea@astro.psu.edu)
Subjects: X-ray, Neutron Star, Transient
Swift performed a second target of opportunity observation of the transient MAXI J1733-222 (ATEL #14683), which is likely a new outburst from the transient source 4U 1730-22 (ATEL #14687), the first detected since its discovery in 1972 (Cominsky et al. 1978). Starting at 23:16UT on Jun 8th, 2021 Swift observed for a total of 2ks, utilizing a broader range of UVOT filters in order to obtain a higher quality localization of the source.
Utilizing UVOT data in order to correct for systematic errors in astrometry (Goad et al., 2007, A&A, 476, 1401; Evans et al., 2009, MNRAS, 2009, 397, 1177), we find an updated position for the transient of RA/Dec (J2000) = 263.48976, -22.03266, which is equivalent to:
RA(J2000) = 17h 33m 57.54s,
Dec(J2000) = -22d 01m 57.6s,
with an estimated uncertainty of 2.1 arcseconds radius (90% confidence). This position lies 0.8 arc-seconds from CXOU J173357.5-220156, the purported quiescent X-ray counterpart of 4U 1730-22 suggested by Tomsick et al (2007), unambiguously showing that the outburst from MAXI J1733-222 came from CXOU J173357.5-220156. That CXOU J173357.5-220156 showed such a bright transient outburst makes its association with 4U 1730-22 more likely.
We note that the flux and spectrum of this source does not show any significant changes from the values reported in ATEL #14686.
This work is supported by funding from the NASA Swift Guest Investigator Program.
