[vsnet-grb-info 16324] GRB 150318A: Skynet PROMPT-CTIO Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17605
SUBJECT: GRB 150318A: Skynet PROMPT-CTIO Observations
DATE:    15/03/18 18:23:19 GMT
FROM:    Adam S. Trotter at UNC-Chapel Hill/PROMPT/Skynet  <atrotter at physics.unc.edu>

A. Trotter, D. Reichart, J. Haislip, A. Aji, R. Beauchemin, T. Berger, A. Dow, A. Foster,
N. Frank, M. Hinckle, K. Ivarsen, A. LaCluyze, M. Maples, J. Moore, M. Nysewander, C. Salemi,
L. Zbinden, and J. A. Crain report:

Skynet observed the Swift BAT/XRT localization of GRB 150318A (Pagani et al., GCN 17599, Swift
trigger=635289) with with one 24" telescope (PROMPT 8; I band) and four 16" telescopes 
(PROMPT 1,3,4,5; V,B,R,I bands) of the PROMPT array at CTIO, Chile. 
Starting at 2015-03-18 06:06:54 UT and continuing until 09:52 UT (t=2m-2.8h post-trigger), 
Skynet took a total of 376 exposures ranging from 10-160s. We stacked subsets of these images 
to maximize the S/N ratio, and detected no optical source in any band at the XRT position.  
Our 3-sigma limiting magnitudes are:

==============================================
tmid    scope   band    exposures   lim mag
----------------------------------------------
104m    PROMPT8  I      69 x 80s     >20.9
104m    PROMPT5  I      43 x 160s    >20.9
78m     PROMPT4  R      37 x 80s     >20.9
104m    PROMPT1  V      42 x 160s    >21.6
125m    PROMPT3  B      18 x 160s    >21.1

Limiting magnitudes are in the Vega System, calibrated to 3 APASS stars in the field.  Magnitudes
have not been corrected for line-of-sight Milky Way dust extinction, with expected E(B-V)=0.03
(Schlafly & Finkbeiner 2011).

No further Skynet observations are scheduled.