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VVV near-infrared observations of the MAXI J1543-564 field

ATel #3372; A. F. Rojas (PUC, Santiago), N. Masetti (INAF/IASF, Bologna) and D. Minniti (PUC, Santiago)
on 23 May 2011; 11:57 UT
Credential Certification: Nicola Masetti (masetti@iasfbo.inaf.it)

Subjects: Infra-Red, X-ray, Transient

Referred to by ATel #: 3407

In order to explore the arcsec-sized soft X-ray (ATel #3331) and radio (ATel #3364) error boxes of the X-ray transient source MAXI J1543-564 (ATel #3330) and to look for a possible quiescent near-infrared (NIR) counterpart, we searched the archival frames of the NIR VVV survey (vvvsurvey.org; Minniti et al. 2010, New Astron., 15, 433) of the Galactic Bulge and inner arms, which is being obtained with the 4.1m VISTA telescope at Cerro Paranal (Chile).

JHKs images were acquired on 17 February 2010 between 07:59 and 08:33 UT under an average seeing of 0.90 arcsec; two further Ks images were secured on 5 March 2010 between 09:12 and 09:20 UT with an average seeing of 0.78 arcsec. YZ photometry was moreover obtained on 2 August 2010 between 02:35 and 02:58 UT (average seeing: 0.94 arcsec).

Exposure times were 10 s for the images acquired on 17 February 2010, 4 s for those of 5 March 2010 and 20 s for those of 2 August 2010. The image scale is 0.34 arcsec/pixel for all images.

Within the Swift/XRT X-ray error circle of MAXI J1543-564 (ATel #3331) we find a single source, with coordinates (J2000) RA = 15 43 17.35, Dec = -56 24 49.1 (+-0.1 arcsec at 1 sigma confidence level). This is consistent with source 'A' reported in ATel #3365 (see also ATel #3359) and has the following magnitudes:

 
 Band      mag    err       date     start time      
------------------------------------------------ 
 
  Y       17.16   0.03   02/08/2010   02:35:24 
  Y       17.09   0.04   02/08/2010   02:49:46 
 
  Z       17.92   0.03   02/08/2010   02:42:50 
  Z       17.81   0.04   02/08/2010   02:57:58 
 
  J       16.38   0.03   16/02/2010   08:12:49 
  J       16.46   0.04   16/02/2010   08:33:01 
 
  H       15.73   0.04   16/02/2010   07:59:11 
  H       15.72   0.04   16/02/2010   08:19:10 
 
  Ks      15.40   0.05   16/02/2010   08:06:03 
  Ks      15.37   0.05   16/02/2010   08:26:08 
  Ks      15.43   0.09   05/03/2010   09:12:41 
  Ks      15.41   0.08   05/03/2010   09:19:57 

The object appears to be constant within errors among the observation epochs.

Unfortunately the image resolution of our VVV images and the crowdedness of the field do not allow us to discern the fainter sources 'B' and 'C' of ATel #3365.

It can be noticed that the ZJHKs magnitudes we obtain for object 'A' are substantially brighter than those reported in Atel #3365. This may be partially due to the fact that we cannot resolve objects 'B' and 'C' in our VVV images. However, we understand that the NIR images described in ATel #3365 apparently suffer from this same problem, so we actually have no straightforward explanation for this discrepancy.

Besides, we do not detect any NIR source within the ATCA radio error ellipse (ATel #3364) down to the VVV survey limits (J ~ 19.5; H ~ 18.0; K ~ 18.0).