Dwarf Nova in Lupus
ATel #12643; V. Kudinov, Y. Sorokin, A. Sorokina, A. Yakubova (Education Center Germes, Moscow), D. Denisenko (SAI MSU/Germes)
on 8 Apr 2019; 17:46 UT
Credential Certification: Denis Denisenko (d.v.denisenko@gmail.com)
Subjects: Optical, Cataclysmic Variable, Transient
We report the discovery of the new optical transient on the images obtained with iTelescope.Net T31 instrument (0.50-m f/6.8 reflector + CCD + f/4.5 focal reducer) on 2019 Apr. 07 at 15:02-15:05 UT. The telescope field of view (56'x56') was centered at NGC 5643 galaxy in Lupus. Comparing our image to the scanned DSS Red photographic plate we have found the new object at the following coordinates (J2000.0): R.A. = 14 31 40.82, Decl. = -43 50 35.3. The magnitude on 2019-04-07.627 UT was 16.2m (unfiltered with Red zero point). The object was named Germes V2. T31 image (sum of three 60-sec unfiltered exposures on 15:02-15:05 UT) is posted at http://scan.sai.msu.ru/~denis/GermesV2-20190407-T31.jpg (FOV cropped to 5'x5'). No object is present at this position in Vizier, AAVSO VSX and TNS. However, there is a faint star (magnitude about 22.0) on DSS Blue plate taken on 1976-05-29 from UK Schmidt telescope. Color-combined DSS finder chart is uploaded to http://scan.sai.msu.ru/~denis/GermesV2-JRIR5x5.jpg (2x zoom).
Checking the DASCH project website (Grindlay et al., 2012) has shown the historical outburst on the 10-inch Metcalf Triplet plate mf09247 taken from Arequipa on 1925-05-29.134 UT (HJD=2424299.639). The combined magnitude of the variable and the nearby star was B=14.62 (15.62 after deblending for the neighbor with B=15.17). The star is also in outburst on the next plate mf09267 on 1925-05-30 (HJD=2424300.676), but with a poor image quality.
Based on the amplitude of variability and past outburst detection, Germes V2 is a dwarf nova, most likely of SU UMa type. Time-resolved photometry is encouraged.
