2-m ShAO telescope spectroscopic classification of Gaia microlensing event candidates

ATel #13992; Gezer I. (Warsaw University Astronomical Observatory, Poland), 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), Zielinski P., Wyrzykowski L., Lam M., 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)
on 7 Sep 2020; 10:43 UT
Credential Certification: Ilknur Gezer (igezer@astrouw.edu.pl)

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We report on the spectroscopic observations of five 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 arcsec. 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  
----------|-----------|-------------|--------------|----------------|-----------------|---------------|---------------  
Gaia20blb | AT2020evf | 18:44:03.09 | +00:29:25.58 |   2020-03-19   |      15.08      | 2020-07-19    | Be star?(1)  
Gaia20cxk | AT2020nko | 19:46:20.12 | +23:38:29.58 |   2020-06-23   |      16.68      | 2020-07-19    | TTauri star?(2)  
Gaia20cek | AT2020jkj | 22:52:08.12 | +60:40:08.33 |   2020-05-08   |      12.20      | 2020-07-24    | TTauri star (3)  
Gaia20bpl | AT2020fuk | 03:11:52.64 | +60:32:13.13 |   2020-04-02   |      14.56      | 2020-08-26    | Be star (4)  
Gaia20bor | AT2020fru | 02:13:25.81 | +62:32:22.74 |   2020-03-31   |      13.44      | 2020-08-23    | Be star (5)  

Notes:
(1) Halpha emission is very weak or absent. Initial spectral type is estimated as B5 Ib-II star using MKCLASS code (Gray & Corbally 2014, AJ 147, 80). The object was reported as microlensing event before based on spectra were taken with 2-m Liverpool Telescope (ATel#13742). The object might be either microlensing event or Be star.
(2) The spectra shows emission in Halpha, which gives radial velocity -50+/-10 km/s. Unfortunately, it is difficult to distinguish any other emmision/absorption lines due to low S/N ratio of the spectrum. We classified the object as K2 V type star based on MKCLASS classification code. The object could be TTauri star. (3) weak emission in Halpha. No emission is observed in the remaining hydrogen lines. Visible absorption lines of metals (Fe I, Ca I, MgII, Mn I etc.) indicate characteristic of late spectral type stars. D Na I and weak TiO bands are clearly distinguishable. Spectral class of the objects is defined as M2 III using MKCLASS code. In addition, the spectrum does not show any forbidden lines. The object shows young stars characteristic. Gaia20cek is likely a weak-line TTauri star.
(4) strong emission in Halpha line, numerous lines of neutral and ionized elements FeI, TiI, CrII, FeII etc. are observed, Be star .
(5) emission in Halpha line. Based on MKCLASS code, it is classified as B3 V type star. Be star.

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). Ismailov N.Z. acknowledges Science Development Foundation under the President of Azerbaijan Grant No EIF-BGM-4-RFTF-1/2017-21/07/1.