GCN Circular 3950
Subject
GRB 050908: Optical observations
Event
Date
2005-09-08T14:59:10Z (20 years ago)
From
Arto Oksanen at Nyrola Obs., Finland <oksanen@nyrola.jklsirius.fi>
D. T. Durig, N. P. McLarty and J. R. Manning (Cordell-Lorenz
Observatory) report on behalf of the AAVSO International High Energy
Network on optical observations of GRB050908 (GCN #3942; Goad et al.):
The optical afterglow reported by K. Torii (GCN #3943) was detected and
its fading behaviour was confirmed with observations starting 14 minutes
after the Swift trigger. Full details and URL to the FITS image are below.
The AAVSO thanks the Curry Foundation for support of the AAVSO
International High Energy Network.
Report filed on Thu Sep 8 06:22:58 2005:
Name: Dr. Douglas T. Durig
email: ddurig@sewanee.edu
Observer: D. T. Durig, N. P. McLarty, J. R. Manning
Site: Cordell-Lorenz Observatory
Location: Sewanee, Tenn., USA
LatitudeLongitude: 35 12 N 85 55 W
Elevation: 600 m
Scope: SCT 0.30 m
ScopeFocalRatio: 1770 mm f/5.9
CCDVendor: SBIG ST-8E
CCDDetector: KAF 1600
CCDSize: 1530x1020, binned 3x3
CCDPixelScale: 3.15 arc sec
CCDFOV: 26.7 x 17.8 arc min/13.35x8.9 shown
Object: GRB050908
ObsDate: 2005 09 08
ObsMidPointTime: 07:59:09
TimePerFrame: 300 sec
NumberOfFrames: 48
Filters: CR
Processing: dark, flat, register, add, 1/2 frame crop
Seeing: ~5 arc sec
LimitingMag: ~21.5-22 ???
Sky: mostly clear, occasional high clouds, no wind
afterglowmag: 19th fading to 21st
afterglowerr: 0.3 mag
compstars: 310 USNO B1.0 stars in field
Report: I had to use my backup CCD because my primary is in for repair.
I started imaging at 05:56:39 ( 2453621.7477 JD ) and did 30 x 300 sec
exposures followed by an additional 18. I was analysing the first 10 and
had identified the potential candidate on my own. I was checking the
fading behaviour when GCN 3943 from Torii announced the same candidate.
I then used my first 20 frames added in sets of 5 to confirm clear
fading
behaviour:
8.25483 01 21 50.72 -12 57 17.4 19.3 R
8.27272 01 21 50.73 -12 57 17.0 19.8 R
8.29063 01 21 50.69 -12 57 17.1 20.4 R
8.30853 01 21 50.79 -12 57 17.0 21.0 R
I then used sets of 10 and 20 to get later data points for the full set
of images.
Full data set:
08.25483 01 21 50.72 -12 57 17.4 19.3 R 850
08.26378 01 21 50.72 -12 57 17.2 19.6 R 850
08.27272 01 21 50.73 -12 57 17.0 19.8 R 850
08.28168 01 21 50.71 -12 57 17.2 19.9 R 850
08.29063 01 21 50.69 -12 57 17.1 20.4 R 850
08.29958 01 21 50.67 -12 57 17.8 20.7 R 850
08.33539 01 21 50.73 -12 57 15.8 20.2 R 850
08.35454 01 21 50.69 -12 57 16.9 21.0 R 850
08.37369 01 21 50.64 -12 57 18.1 21.4 R 850
A FITS image has been uploaded to:
ftp://ftp.aavso.org/grb/Dr.DouglasT.Durig_GRB050908_2453621.93262_.fits