VLT/X-Shooter spectroscopic classification of candidates for microlensing events from Gaia

ATel #12103; K. Kruszynska, M. Gromadzki, L. Wyrzykowski, P. Zielinski, M. Zielinski, K. A. Rybicki (Warsaw University Astronomical Observatory), S. T. Hodgkin (IoA Cambridge)
on 11 Oct 2018; 09:58 UT
Credential Certification: Lukasz Wyrzykowski (wyrzykow@astrouw.edu.pl)

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We report on spectroscopic observations of 6 bright candidates for microlensing events detected primarily by the Gaia Science Alerts programme (http://gsaweb.ast.cam.ac.uk/alerts). Spectra were taken with ESO/VLT/X-Shooter instrument with slit widths 1.0'', 0.7'', 0.6'' yielding resolutions of 6000, 10500, 8000 in UBV, VIS and NIR, respectively.

Survey Name | IAU Name | RA (J2000) | Dec (J2000) | Discovery date | Discovery G mag | Spectrum date | Class | Notes
------------|-------------|-------------|--------------|----------------|-----------------|------------------|------------| ------
Gaia18bcb | AT2018bdp | 19:05:20.47 | 08:36:10.15 | 2018-04-28.04 | 17.28 | 2018-08-14 | VSTAR | (1)
Gaia18ces | AT2018fct | 17:57:03.78 | -33:56:09.89 | 2018-08-13.24 | 14.93 | 2018-09-16 | star/ULENS | (2)
Gaia18cjk | AT2018fmx | 18:55:09.13 | -06:39:48.71 | 2018-08-23.14 | 16.08 | 2018-09-01 | star/ULENS | (3)
Gaia18cmn | AT2018fux | 17:12:19.01 | -40:02:51.47 | 2018-09-02.69 | 15.51 | 2018-09-16 | Be star |
Gaia18cre | AT2018glo | 08:14:10.25 | -33:28:38.78 | 2018-09-11.05 | 12.49 | 2018-09-20 | Ae/Be star | (4)
Gaia18cnm | AT2018gcs | 18:23:30.92 | -07:19:57.76 | 2018-09-05.89 | 17.89 | 2018-09-28 | star/ULENS | (5)

(1) TiO absorption bands, late M star, most likely an AGB star showing long-period variability
(2) Event coinciding with OGLE-2018-BLG-0988. Spectral features of a late G giant.
(3) Early K giant.
(4) Spectrum shows A-type continuum. Halpha and other hydrogen lines of Paschen and Brackett series show disk-like emission profiles, but rest of the lines of Balmer series are in absorption.
(5) G8 giant (G8II) or supergiant (G8I).

We acknowledge ESA Gaia, DPAC and the Photometric Science Alerts Team (http://gsaweb.ast.cam.ac.uk/alerts). We thank ESO/VLT staff for support. Observations were carried out under ESO programme 0101.D-0035(A), PI: Wyrzykowski.