[show abstract][hide abstract] ABSTRACT: The sky region including the Chandra position of SGR 1806-20 was monitored in the IR band during 2004, following its increased high energy bursting activity. Observations were performed using NAOS-CONICA, the adaptive optics IR camera mounted on Yepun VLT, which provided images of unprecedented quality (FWHM better than 0.1"). After the 2004 December 27th giant flare, the source position has been nailed by VLA observations of its radio counterpart, reducing the positional uncertainty to 0.04". Using IR data from our monitoring campaign, we discovered the likely IR counterpart to SGR 1806-20 based on positional coincidence with the Chandra and VLA uncertainty regions and flux variability of a factor of about 2 correlated with that at higher energies. We compare our findings with other isolated neutron star classes thought to be related, at some level, with SGRs. Comment: 4 pages, 2 figures. Accepted for publication on A&A Letters
[show abstract][hide abstract] ABSTRACT: We report on IR VLT adaptive optics (2003 October 7th; H and Ks band) and Chandra (2003 November 1st; HRC-I) ToO observations of the field of the new candidate Anomalous X--ray Pulsar (AXP) XTE J1810-197 (also known as CXOU J180951.1-194351; IAUC 8168 , IAUC 8190, ATEL #193, ATEL #195, Ibrahim et al. 2003, astro-ph/0310665, and Gotthelf et al. 2003, astro-ph/0309745). Images in the H and Ks band were obtained (effective exposure time of 42 minutes) with NAOS-CONICA (1024x1024 pixels, 0.027" pixel scale; 28"x28" Field of View) under very good sky and seeing condition (about 0.5"), resulting in an on-axis FWHM of about 0.15" for a point-like source.