Spectroscopic classification of microlensing event candidates Gaia19dmj/AT2019nkr and Gaia20cop/AT2020lqa by 2-m ShAO telescope

ATel #13907; Zielinski P., Wyrzykowski L., Lam M., Gezer I., Kruszynska K., Rybicki K. A., Ihanec N. (Warsaw University Astronomical Observatory, Poland), Zdanavicius J., Maskoliunas M., Pakstiene E. (Institute of Theoretical Physics and Astronomy, Vilnius University, Lithuania), Ismailov N. Z., Mikailov Kh. M., Khalilov O. V., Alekberov I. A., Bagirli S., Alishov S. A. (Shamakhy Astrophysical Observatory of National Academy of Sciences, Azerbaijan)
on 30 Jul 2020; 14:41 UT
Credential Certification: Pawel Zielinski (pzielinski.astro@gmail.com)

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We report on the spectroscopic observations of two transient events detected by the Gaia Science Alerts programme (http://gsaweb.ast.cam.ac.uk/alerts). Spectra were taken with 2-m Shamakhy Astrophysical Observatory (ShAO) telescope in Azerbaijan. Observations were made at the Cassegrain focus of the 2-m telescope with UAGS + objective Canon EF (f=200 mm, f/2) + CCD Andor (ikonL-936-BEX2-DD 2048x2048, px=13.5 um) spectrograph. The spectral range is 3750-7650 A. The width of the slit was 3.3”. The spectral resolution is about 6 A/px. Spectrophotometric standard stars were observed every night immediately after the object. The links provided as IAU names of the events lead to the Transient Name Server pages with detailed information and spectra.

 
Gaia Name | IAU Name   | RA (J2000)  | Dec (J2000)  | Discovery date | Discovery G mag | Spectrum date | Class  
----------|------------|-------------|--------------|----------------|-----------------|---------------|------------------  
Gaia19dmj | AT 2019nkr | 20:05:35.88 | +26:10:03.68 | 2019-08-11     |      13.86      | 2020-06-23    | star/ULENS (1)  
Gaia20cop | AT 2020lqa | 19:46:03.21 | +27:19:51.24 | 2020-06-01     |      14.06      | 2020-06-23    | Ae/Be star (2)  

Notes:
(1) We have detected the spectral lines D Na I 5893 A (combined 5889+5896 A), Si I 5780 A, some Fe I lines, with blue displacement -25, -40 km/s. There are no emission lines visible and the shape of the continuum suggests reddened late-type star. Based on MKCLASS code (Gray & Corbally 2014, AJ 147, 80) we classified the source as G8 III star, therefore Gaia19dmj is likely a microlensing event.
(2) The spectrum shows dominant Balmer series in absorption, except Halpha line which seems to be in emission. The hydrogen lines gives radial velocity 71+/-3 km/s. We have also detected spectral lines D Na I 5893 A, Si I 5780 A, Fe II 4431 A and 4387 A lines. The spectrum shows some depression in the range of 4250-5700 A, which is one of the properties of magnetic peculiar Ap stars. It could be an indicator of the strong magnetic field. This and MKCLASS code indicates this transient is a Herbig Ae/Be star outburst.

Acknowledgments. This project has received funding from the EU Horizon 2020 research and innovation programme under grant agreement No. 730890, as well as Polish NCN DAINA grant 2017/27/L/ST9/03221 and Research Council of Lithuania grant No. S-LL-19-2. We acknowledge ESA Gaia, DPAC and the Photometric Science Alerts Team (http://gsaweb.ast.cam.ac.uk/alerts).