Decline in UV and non-detection in X-ray of the transient event OGLE15aaa
ATel #8644; Wenda Zhang (MPA), Wenfei Yu (SHAO), Zhen Yan (SHAO)
on 6 Feb 2016; 15:11 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Wenfei Yu (email@example.com)
Subjects: X-ray, Black Hole, Transient
OGLE16aaa was an optical transient discovered by OGLE on Jan 2, 2016 (ATel
#8577). Located at the center of an inactive galaxy and having blue optical-IR
continuum (ATel #8559, #8577, #8579), it was considered as candidate of tidal
disruption event; however an Swift/XRT observation did not detect the source, making
the TDE scenario less likely (ATel #8579). The light curve was found to reach a
maximum in I-band on Jan 20, 2016 (ATel #8577).
We report on three recent Swift ToO observations of OGLE16aaa, on Jan 28, Feb 1,
and Feb 2, respectively. Three UV filters, namely UVW1, UVW2, and UVM2, were used
during these observations, and the source was detected in these bands. Its UV flux
has declined, from 17.36+/-0.06 mag to 17.58+/-0.06 mag in UVW2, 17.07+/-0.06 mag to
17.32+/-0.06 mag in UVM2, and 17.08+/-0.05 mag to 17.24+/-0.04 mag in UVM1,
respectively, from Jan 28 to Feb 2. The source was undetected in the X-ray with the
Swift/XRT observations, which is expected since it was undetected on Jan 19, only ~1
day before I-band maximum and the UV flux was declining.
We thank the Swift team for rapidly arranging the observations.