[vsnet-grb-info 25054] LIGO/Virgo S200213t: Swift UVOT and XRT observations of ZTF20aamvmzj (AT2020cja)

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27153
SUBJECT: LIGO/Virgo S200213t: Swift UVOT and XRT observations of ZTF20aamvmzj (AT2020cja)
DATE:    20/02/20 13:50:37 GMT
FROM:    Samantha Oates at MSSL  <sro at mssl.ucl.ac.uk>

S. R. Oates (U. of Birmingham),  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), N. J. Klingler (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 Swift/UVOT and XRT follow-up 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). 

Swift/UVOT and XRT observations began 6.7 days after the LIGO/VIRGO trigger (LIGO/VIRGO 
Collaboration GCN Circ. 27042). We detect ZTF20aamvmzj in the u and UV filters only. In the
following we give preliminary magnitudes using the UVOT photometric system (Breeveld et al. 
2011, AIP Conf. Proc. 1358, 373):

Filter   T_start(s)   T_stop(s) Exp(s)     Mag

v      577293     588978    228      >19.2
b      576882	  588576    236      >19.92
u      576797	  588492    236      19.05 +/- 0.27
w1     576633	  588408    472      19.46 +/- 0.30
m2     577377	  583756    753      19.82 +/- 0.29
w2     576967	  588902    944      19.64 +/- 0.23

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).

In XRT, no source was found at the location of ZTF20aamvmzj, down to a 3-sigma upper limit of
3.1e-3 count s^-1 in 3 ks of exposure. Assuming a power-law spectrum with NH=3x10^20 cm^-2, and
photon index (Gamma)=1.7, this equates to a upper limit of F < 1.2x10^-13 erg cm^-2 s^-1 on
the 0.3-10 keV observed flux.

This circular is an official product of the Swift team.