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Follow-up photometry of transients Gaia16asm, Gaia17cao, and Gaia17cuh

ATel #11006; V. Reshetnyk (Taras Shevchenko National University of Kyiv, Ukraine), Y. Bufan (ICAMER Observatory & Ivan Franko National University of Lviv, Ukraine), V. Kozlov (ICAMER Observatory, Ukraine), I. Sokolov (INASAN RAS, Russia), A. Simon (Taras Shevchenko National University of Kyiv, Ukraine), V. Godunova (ICAMER Observatory, Ukraine), O. Sergeev (ICAMER Observatory, Ukraine)
on 24 Nov 2017; 19:05 UT
Credential Certification: Andrew Simon (skazhenijandrew@gmail.com)

Subjects: Optical, Transient

We report optical observations of transients Gaia17cuh, Gaia17cao, and Gaia16asm, which are assumed to be CVs. Their photometry was performed at the Terskol Observatory (the Northern Caucasus) in July-November 2017.

A bright blue transient Gaia17cuh on faint red Gaia source near Galactic plane was discovered on 2017-11-02 at magnitude G = 15.48; its previous observations by Gaia in 2015-2017 showed the mean magnitude G = 18.92 ± 0.23. We detected the source on the images taken on 2017-11-18 with the 2-m RCC telescope. The following magnitudes of the object were measured (calibrated against NOMAD field stars; not corrected for the Galactic foreground extinction):
MJDfiltermagerrstat
58076.1949B19.350.04
58076.1926V19.080.04
58076.1934R18.490.05

A long-term increase in brightness of Gaia source Gaia17cao was announced on 2017-08-11 after its G magnitude reached 18.62 on 2017-08-08 08:33:06 (and 18.31 two hours later). We had begun to observe this object on 2017-08-28 using the 0.6-m Zeiss telescope. Gaia17cao was detected at magnitudes V = 19.6 ± 0.1, R = 18.8 ± 0.1 (MJD 57993.71) that indicated a fading trend in brightness of the source. Results of further observations in September and November 2017 are as follows:
MJDVeVReR
57999.7820.10.119.40.1
58000.7720.0 0.119.50.1
58066.6520.10.119.30.1
58070.6420.20.119.40.2
The magnitudes were calibrated against AAVSO field stars; they are not corrected for the Galactic foreground extinction.

An almost 2 mag dip in brightness of Gaia16asm was detected by Gaia twice over the last three years. Our photometry which was performed in July and November 2017 with the 0.6-m telescope did not show any signs of significant variability in brightness of this star. The following magnitudes of the object were derived:
MJDBeBVeVReR
57936.9414.660.0114.560.0215.100.02
57937.9614.670.0214.570.0115.100.01
57939.9814.680.0614.590.0115.130.03
58066.7114.710.0114.570.0115.100.01
58070.6914.720.0114.570.0115.100.01
58072.7414.660.0514.560.0315.100.02
58074.7914.730.0614.540.0215.080.05
The magnitudes were calibrated against NOMAD field stars; they are not corrected for the Galactic foreground extinction.

We acknowledge ESA Gaia, DPAC and the Photometric Science Alerts Team (http://gsaweb.ast.cam.ac.uk/alerts).