Prediscovery detection of AT 2021aaxp, the galactic dwarf nova in the field of M31
ATel #14963; A. Horti-David, K. Sarneczky, J. Vinko (Konkoly Obs.)
on 10 Oct 2021; 18:46 UT
Credential Certification: Jozsef Vinko (vinko@astro.as.utexas.edu)
Subjects: Optical, Cataclysmic Variable
We report a prediscovery detection of AT 2021aaxp, aka PNV J00444033+4113068 discovered by K. Itagaki on 2021-10-09.4579 then independently by D. Balam (DAO/NRC), C. E. Spratt (Ret), P. Langill (U of Calgary) and D. Green (CBAT) on 2021-10-09.6125. It was classified as a galactic dwarf nova in the direction of M31 by K. Taguchi and H. Maehara (ATel #14962). Our data were taken by the 0.6/0.9m Schmidt telescope equipped with a 10560x10560 STA 1600LN CCD at Piszkesteto Station of Konkoly Observatory, Hungary on 2021-10-08.85 UT and 2021-10-09.77 UT. The total exposure time was 900 seconds. Each night 15 unfiltered frames covering the 9 deg^2 field-of-view were collected and median-combined to get the final image.
AT 2021aaxp was found as a bright source on the difference image taken on 2021-10-09.77 UT using the combined frame taken on 2021-07-28 with the same telescope and setup, as a template. We estimate its brightness as 15.72 +/- 0.02 mag (unfiltered) tied to r-band photometry of local PS1 stars. The transient was also detected on the previous night, 2021-10-08.85 UT at 20.26 +/- 0.10 mag. Its rapid rise, 4.5 mag in ~1 day, is consistent with the classification as a dwarf nova.
