Support ATel At Patreon

[ Previous | Next | ADS ]

Further Swift/UVOT Observations of AT2018cow

ATel #11767; Peter J. Brown (Texas A&M, Mitchell Institute)
on 22 Jun 2018; 23:27 UT
Credential Certification: Peter J. Brown (grbpeter@yahoo.com)

Subjects: Optical, Ultra-Violet, Gamma-Ray Burst, Supernovae, Transient

I report on continuing observations of AT2018cow (Smartt et al. 2017, ATEL#11727) with the Ultra-Violet Optical Telescope (UVOT; Roming et al. 2005) on the Neil Gehrels Swift Observatory (Gehrels et al. 2004). In the most recent observation, beginning 2018-06-22 16:36:43 I measure the following magnitudes in the UVOT/Vega-based photometric system using the pipeline for the Swift Optical Ultraviolet Supernova Archive (SOUSA; Brown et al. 2014):
uvw2=12.87 +\- 0.03
uvm2=12.83 +\- 0.04
uvw1=12.97 +\- 0.03
u=13.68 +\- 0.03
b=15.14 +\- 0.04
v=15.05 +\- 0.05
These Vega magnitudes have not been corrected for reddening or the minimal contribution from the host galaxy.

The source remains very blue in UV-optical colors. Compared to the earlier observations (e.g. Rivera Sandoval & Maccarone, ATEL#11737) the transient fades rather achromatically by about 0.3 mag/day. Accounting for a MW reddening of E(B-V)= 0.077 in the direction of the host (Schlafly & Finkbeiner 2011), the UVOT photometry spanning 1600-6000 Angstroms can be fit with a blackbody with a temperature of about 25,000 K or a power law with an index of alpha of approximately 3.

Further Swift observations are planned to monitor the X-ray and UV/optical behavior of this source.

AT2018cow light curve from Swift/UVOT