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Optical/Near-IR Counterpart of the Bright X-ray Transient XMMSL2 J053629.4-675940

ATel #11197; Peter Pessev (GRANTECAN, IAC, ULL)
on 18 Jan 2018; 14:55 UT
Credential Certification: Peter Pessev (peter.pessev@gtc.iac.es)

Subjects: Infra-Red, Optical, Transient

XMM-Newton discovered a bright X-ray transient during a slew made on 05.01.2018 (#ATel11182). The transient is positionally consistent within the uncertainty with the known X-ray source XMMSL2 J053629.4-675940. Taking into account the positional uncertainty of the catalogued source RA=05:36:30.35, Dec=-67:59:35.9 (with an error of ~2 arcsec), #ATel11185 reported the observed OGLE counterpart. In the following table the results of an extensive archival search of possible counterparts are presented. They are based on three all-sky surveys (2MASS, WISE, GAIA), Hubble Guide Star Catalog and two Magellanic Clouds surveys (MCPS and SAGE(Meixner et al. 2006)), resulting of a SED between ~ 0.37 and 22.2µm. The search was done within the error circle of the XMMSL2 J053629.4-675940 position. The distance (in degrees) of the encountered object from the search center is reported in the fourth column of the table below.

Filter....Mag........Mag.Err...Dist.[deg.]..Survey/(Source ID)........

U..........19.178.....0.093.....0.0003.......MCPS/Zaritsky et al. 2004
B..........19.785.....0.045.....0.0003.......MCPS/Zaritsky et al. 2004
V...........18.177.....0.139....0.0003.......MCPS/Zaritsky et al. 2004
G..........18.017..................0.00037......GAIA (5237407060614222336)
R..........17.35.......0.46.......0.00036.....GSC2.2 (S0132003167858)
I...........14.998.....0.040.....0.0003.......MCPS/Zaritsky et al. 2004
J...........13.452.....0.029.....0.00023......2MASS (05363020-6759371)
H..........12.878.....0.028.....0.00023......2MASS (05363020-6759371)
Ks.........12.59.......0.032.....0.00023......2MASS (05363020-6759371)
W1........12.42.......0.024.....0.00021......WISE (J053630.22-675936.6)
[3.6].....12.309......0.044.....0.0002.......SAGE (J053630.22-675936.9)
[4.5].....12.186......0.024.....0.0002.......SAGE (J053630.22-675936.9)
W2........12.261......0.023.....0.00021.....WISE (J053630.22-675936.6)
[5.8].....12.121......0.042.....0.0002.......SAGE (J053630.22-675936.9)
[8.0].....12.115......0.031.....0.0002.......SAGE (J053630.22-675936.9)
W3........13.526....................0.00021.....WISE (J053630.22-675936.6)
W4........10.09......................0.00021.....WISE (J053630.22-675936.6)

Notably the I band magnitude and V-I color reported by the Magellanic Cloud Photometric Survey (MCPS) are consistent within the errorbars with the OGLE values in #ATel11185. According to the LMC Extinction Retrieval Service (Zaritsky et al. 2004; http://djuma.as.arizona.edu/~dennis/lmcext.html ), the weighted mean of the Av values derived in a 5 arcminutes radius for cool, hot and all stars is 0.5+/-0.2 mags. Based on these the following colors are calculated (V-R)0=0.7+/-0.6; (V-I)0=2.9+/-0.3; (V-J)0=4.4+/-0.4; (V-H)0=4.9+/-0.4; (V-Ks)0=5.2+/-0.5. According to the results of Ducati et al. 2001, these colors are not consistent with any main sequence star (too red), but are in a broad agreement with the expected colors for a M spectral type giant or supergiant. This is also consistent with the shape of the SED in the Spitzer and WISE passbands. Such a conclusion is contradicting the reported relatively large proper motion of the object. A chance superposition of two objects on the sky, one of them nearby with a large proper motion is a possible explanation. Further observations and analysis of this potentially interesting object are strongly encouraged.