Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 27400

LIGO/Virgo S200213t: Continued Swift UVOT and XRT observations of ZTF20aamvmzj (AT2020cja)
2020-03-17T13:54:01Z (4 years ago)
Samantha Oates at MSSL <>
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.
Looking for U.S. government information and services? Visit