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VLT/FORS2 spectroscopic classification of an unusual nuclear transient OGLE17aaj

ATel #9977; M. Gromadzki, A. Hamanowicz and L. Wyrzykowski (Warsaw University Astronomical Observatory, Poland)
on 19 Jan 2017; 19:49 UT
Credential Certification: Lukasz Wyrzykowski (wyrzykow@astrouw.edu.pl)

Subjects: Optical, Supernovae, Transient, Tidal Disruption Event

Referred to by ATel #: 10006, 10776

We report the spectroscopic classification of a nuclear transient discovered by OGLE-IV. The spectra were obtained using the FOcal Reducer/low dispersion Spectrograph 2 (FORS2) on the Very Large Telescope (VLT). The target was selected from OGLE-IV Real-time Transient Search (http://ogle.astrouw.edu.pl/ogle4/transients/ Wyrzykowski et al. 2014, Acta Astronomica 64, 197). Object has been slowly rising (reached I-band maximum in around 60 days) and is centrally located within its host galaxy (offset less than 260mas), thus is considered as a possible Tidal Disruption Event (TDE). Inspection of the spectrum reveals a flat continuum with apparent emission lines of HI (from alpha to delta), HeI, broad HeII, [OII], [OIII] and SII, at redshift z=0.116. Estimated absolute magnitude in the I-band, without any extinction correction is about -18.8 at the maximum brightness. Line ratios are not indicative of an AGN.

Name | RA (J2000) | Dec (J2000) | Disc. Date | Disc. Mag | Obs. Date | z | Type | Notes |
OGLE17aaj | 1:56:24.93 | -71:04:15.7 | 2017-01-01 | 19.9 | 2017-01-15 | 0.116 | TDE candidate | post-max |

Further observations are encouraged. The observations were carried under ToO programme 098.B-0768(A), PI: L. Wyrzykowski. We thank ESO/VLT staff for their support.