S. R. Oates (U. of Birmingham), N. J. Klingler (PSU), K. L. Page (U.Leicester), A. A. Breeveld (MSSL-UCL),
P. Brown (TAMU), M. De Pasquale (Istanbul U.), C. Gronwall (PSU), N. P. M. Kuin (UCL-MSSL),
F. E. Marshall (NASA/GSFC), M. J. Page (UCL-MSSL), M. H. Siegel (PSU), A. D'Ai (INAF-IASFPA),
P. D'Avanzo (INAF-OAB), S. D. Barthelmy (NASA/GSFC), A. P. Beardmore (U. Leicester),
D. N. Burrows (PSU), S. Campana (INAF-OAB), S. B. Cenko (NASA/GSFC), G. Cusumano (INAF-IASF PA),
V. D'Elia (ASDC), P. A. Evans (U. Leicester),P. Giommi (ASI), D. Hartmann (Clemson U.),
J. A. Kennea (PSU), H. A. Krimm (NSF), A. Y. Lien (GSFC/UMBC), D. B. Malesani (DTU Space),
A. Melandri (INAF-OAB), J. A. Nousek (PSU), P. T. O'Brien (U. Leicester), J. P. Osborne (U. Leicester),
C. Pagani (U. Leicester), D. M. Palmer (LANL), M. Perri (ASDC), J. L. Racusin (NASA/GSFC),
T. Sakamoto (AGU), B. Sbarufatti (INAF-OAB/PSU), G. Tagliaferri (INAF-OAB), A. Tohuvavohu (U Toronto),
and E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team:
We report continued Swift/UVOT and XRT observations of ZTF20aamvmzj (AT2020cja; Kasliwal et al.,
GCN Circ. 27051) found by Zwicky Transient Facility during the search for the EM counterpart
of the LVC event S200213t (LIGO/VIRGO Collaboration GCN Circ. 27042). This object was also
observed by Lulin (Li et al., GCN Circ. 27082) and spectroscopically by DBSP (Ho et al., GCN Circ. 27074).
The Swift/UVOT detection was reported in Oates et al., (GCN Circ. 27153).
Swift/UVOT and XRT has monitored this source from 6.7 days until 29 days after the LIGO/VIRGO trigger
(LIGO/VIRGO Collaboration GCN Circ. 27042). During this time the source was observed to decay and we
no longer detect the source in any filter. In the following we give preliminary 3 sigma upper limits,
combining images from the last two observations, using the UVOT photometric system (Breeveld et al.
2011, AIP Conf. Proc. 1358, 373):
Filter T_start(s) T_stop(s) Exp(s) 3sigUL
v 1714547 2505112 428 > 19.8
b 1713986 2504817 428 > 20.7
u 1713871 2504756 428 > 20.2
w1 1713647 2504694 857 > 20.2
m2 1714661 2505297 1238 > 20.5
w2 1714102 2505050 1717 > 20.8
The magnitudes in the table are not corrected for the Galactic extinction due to the
significant reddening of E(B-V) = 0.23 in the direction of the burst (Schlegel et al. 1998).
Combining all 14.4 ks of XRT data collected to date, no source is detected down to a count rate
of 6.7x10^-4 count s^-1. This corresponds to a 3-sigma upper limit of 2.9x10^-14 erg cm^-2 s^-1,
assuming a standard power-law spectrum with NH=3x10^20 cm^-2, and photon index (Gamma)=1.7.
This circular is an official product of the Swift team.