BAT/Scorpio-2 spectroscopic classification of Gaia microlensing event candidates

ATel #15195; Zielinski P. (Institute of Astronomy, Nicolaus Copernicus University in Torun, Poland), Grokhovskaya A., (Special Astrophysical Observatory & Institute of Applied Astronomy, Russian Academy of Sciences, Russia), Shablovinskaya E., Moiseev A. (Special Astrophysical Observatory, Russian Academy of Sciences, Russia), Gromadzki M., Wyrzykowski L., Ihanec N., Gezer I., Jablonska, M., Kruszynska K., Rybicki K. A., Mikolajczyk P. (Warsaw University Astronomical Observatory, Poland), Maskoliunas M., Pakstiene E., Zdanavicius J. (Institute of Theoretical Physics and Astronomy, Vilnius University, Lithuania)
on 1 Feb 2022; 18:01 UT
Credential Certification: Pawel Zielinski (pzielinski.astro@gmail.com)

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We report on spectroscopic observations of 4 candidates for microlensing events detected by the Gaia Science Alerts program (http://gsaweb.ast.cam.ac.uk/alerts). The spectroscopic data were collected by 6-m BAT telescope (https://relay.sao.ru/Doc-en/Telescopes/bta/descrip.html) equipped with Scorpio-2 and E2V261-84 CCD detector (Afanasiev & Moiseev, 2011). The observations were carried out in long-slit mode with diffraction grating VPHG940 at 600 nm and LP425 filter (wavelength range 425 – 850 nm for Gaia18arn, Gaia19flk, Gaia21eob) and VPHG1200 at 540 nm (spectral range 365 – 725 nm for Gaia19dqe) which provides resolution power of R~800-1000. Based on that, none of these targets was classified as microlensing event. The spectra are available on IAU's Transient Name Server.

 
Gaia Name | IAU Name    | RA (J2000)  | Dec (J2000)  | Discovery date | Discovery G mag | Spectrum date | Class 
----------|-------------|-------------|--------------|----------------|-----------------|---------------|--------------- 
Gaia18arn | AT 2018ake  | 21:35:15.41 | 50:28:50.41  |   2018-03-19   |   16.88         | 2021-12-07    | Be star (1) 
Gaia19flk | AT 2019wem  | 22:09:05.64 | 57:44:53.92  |   2019-12-06   |   14.32         | 2021-12-07    | Be star? (2) 
Gaia19dqe | AT 2019ocq  | 06:39:25.52 | -00:22:11.53 |   2019-08-18   |   12.80         | 2022-01-25    | Be star (3) 
Gaia21eob | AT 2021aayr| 00:59:09.05 | 65:07:38.39  |   2021-10-03   |   17.44         | 2021-11-25    | Be star or YSO (4) 

Notes:
(1) strong Halpha emission, reddened Be star.
(2) core emission in Halpha visible, probably Be star.
(3) Balmer series in absorption, but Halpha line exhibits core emission, early-type continuum shape, Be star.
(4) emission in the cores of Balmer lines visible, reddened Be star or YSO.

Acknowledgments. Observations with the SAO RAS telescopes are supported by the Ministry of Science and Higher Education of the Russian Federation (including agreement No05.619.21.0016, project ID RFMEFI61919X0016). This project has received funding from the EU Horizon 2020 research and innovation programme under grant agreement No. 101004719, 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).