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OGLE-IV Transient Search report 22 January 2016 and follow-up of OGLE16aaa TDE candidate

ATel #8577; L. Wyrzykowski, Z. Kostrzewa-Rutkowska, A. Udalski, S. Kozlowski, M. Pawlak, M. Szymanski, M. Sitek, J. Klencki (Warsaw University Astronomical Observatory, Poland) on behalf of the OGLE team, I. Arcavi (LCOGT)
on 22 Jan 2016; 12:11 UT
Credential Certification: Lukasz Wyrzykowski (wyrzykow@astrouw.edu.pl)

Subjects: Optical, Black Hole, Supernovae, Transient

Referred to by ATel #: 8579, 8608, 8644

The OGLE-IV Transient Detection System (Wyrzykowski et al. 2014, AcA,64,197; Kozlowski et al. 2013, Klencki et al. 2016, AcA submitted) reports the discovery of 20 new on-going transients.

They appeared near or on top of apparent galaxies and their light curves resemble those of supernovae near or after their peak brightness. Most of the candidates were detected with our Rapid Transient Detection System within less than 15 mins from observation and were made immediately available on the Rapid webpages: http://ogle.astrouw.edu.pl/ogle4/transients/rapid/rapid.html

Name RA(J2000.0) Dec(J2000.0) discovery_JD discovery_Imag Notes
OGLE16aaa 1:07:20.88 -64:16:20.7 2457389.55822 20.031 (1)
OGLE16aab 1:48:31.43 -72:06:35.9 2457389.59105 19.465
OGLE16aac 5:25:24.20 -62:33:35.0 2457388.77872 19.465
OGLE16aad 0:25:44.25 -62:43:06.1 2457390.57910 19.438
OGLE16aah 1:18:57.11 -66:10:18.8 2457389.56459 21.164
OGLE16aai 0:55:35.63 -69:11:45.9 2457390.54086 20.143
OGLE16aaj 3:52:21.19 -72:56:31.6 2457385.62371 18.908
OGLE16aak 2:49:16.50 -65:13:56.5 2457387.67346 19.427
OGLE16afb 3:24:47.85 -72:39:42.0 2457399.62089 19.953
OGLE16agc 6:08:03.49 -71:54:49.1 2457401.75930 20.265
OGLE16afl 2:58:36.85 -76:35:56.5 2457401.59495 20.027
OGLE16ahk 5:31:57.25 -65:06:07.9 2457402.74487 20.531
OGLE16ahz 6:15:07.11 -64:30:04.7 2457402.80368 19.619
OGLE16ajk 1:41:24.05 -69:02:43.1 2457404.57412 20.093
OGLE16akk 3:31:37.71 -70:46:30.6 2457404.62941 20.476
OGLE16alt 5:55:10.83 -62:15:59.1 2457404.79591 19.400
OGLE16amc 4:04:02.35 -62:45:26.3 2457405.65343 19.060
OGLE16amx 6:12:58.92 -74:22:50.1 2457407.69524 20.359
OGLE16anh 0:29:14.56 -67:48:08.6 2457408.54047 19.930
OGLE16anr 5:39:45.57 -67:22:39.0 2457408.73502 17.476

(1) Candidate for a tidal disruption event (TDE). PESSTO spectrum (Firth et al. ATEL #8559) found a blue featureless continuum. Our detailed analysis of the spectrum (via WiseREP, Ofer&Gal-Yam 2012, http://wiserep.weizmann.ac.il/ ) indicates possible redshift of z=0.167 based on H, OII and CaII lines. OGLE-IV follow-up in I- and V-band, after calibrations:
HJD I[mag] errI[mag] V[mag] errV[mag] V-I[mag]
2457394.54 19.51 0.08 19.45 0.04 -0.06
2457402.53 19.27 0.11 19.32 0.05 +0.05

The light curve seems to have reached its maximum brightness in I-band at
2457407.53784 18.98 0.05
what for z=0.167 indicates absolute brightness of about -20.6 mag, supporting a TDE hypothesis.

Photometric and spectroscopic follow-up is strongly encouraged.

Finding charts and light curves are available here