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MAXI J1807+132: archival optical variability of Swift counterpart

ATel #10217; D. Denisenko (Sternberg Astronomical Institute, Lomonosov Moscow State University)
on 27 Mar 2017; 20:31 UT
Credential Certification: Denis Denisenko (d.v.denisenko@gmail.com)

Subjects: Optical, Transient

Referred to by ATel #: 10221, 10223, 10224

Following the detection of X-ray source inside MAXI J1807+132 error ellipse (Negoro et al., ATel #10208) I have inspected the digitized Palomar plates via DSS Plate Finder centered at the coordinates from ATel #10215 (Kennea et al.). The object with V magnitude 17.8 is clearly present at the position of Swift source on Quick-V plate taken on 1982-05-20. Color-combined (BRIR and OVR) images are available at http://scan.sai.msu.ru/~denis/MAXIJ1807+132-BRIR-OVR.jpg (4'x4' FOV).

The object at quiescence is detected in PanSTARRS-1 archival images (Chambers et al., arxiv:1612.05560) with the following J2000.0 coordinates (rounded to 0.1"): R.A. = 18 08 07.55, Decl. = +13 15 05.4 which perfectly match the UVOT position reported by Kennea et al., ATel #10216. Mean magnitudes from multi-epoch Pan-STARRS observations are as follows:

g=21.04+/-0.18 (9 detections)
r=21.19+/-0.09 (11 detections)
i=21.38+/-0.04 (5 detections)
z=21.04+/-0.24 (5 detections)
y=20.65+/-0.20 (1 detection)

Animation of 1982 Quick-V plate, 1993-09-13 POSS-II Red plate and Pan-STARRS g and r images is uploaded to http://scan.sai.msu.ru/~denis/MAXIJ1807+132-DSS-PS1-anim.gif (FOV is 2'x2').

Time-resolved photometry is strongly encouraged, as well as checking the optical observations of the field, especially in 1988, 1993, 1999 and 2005 (assuming the event is recurrent with the period of 5.8 years).