GRB170921_142848_SWIFT at TAROT Calern observatory

TAROT Calern observatory log of images

AL_20170921_182326108_000000_86581701     0 star  filter C [13892.5s - 14072.5s] expo=180s elev=12.0deg humid=  0% sunelev=-9.7deg (moon at 151.0deg phase=0.10 elev= +0.0 )
AL_20170921_182636624_000000_86581701     0 star  filter C [14083.1s - 14263.1s] expo=180s elev=12.5deg humid=  0% sunelev=-10.3deg (moon at 151.0deg phase=0.10 elev= +0.0 )
AL_20170921_182947139_000000_86581701     6 stars filter C [14273.6s - 14453.6s] expo=180s elev=13.0deg humid=  0% sunelev=-10.8deg (moon at 151.0deg phase=0.10 elev= +0.0 )
AL_20170921_183319677_000000_86581801     7 stars filter C [14486.1s - 14666.1s] expo=180s elev=13.5deg humid=  0% sunelev=-11.5deg (moon at 151.0deg phase=0.10 elev= -1.0 )
AL_20170921_183629990_000000_86581801    13 stars filter C [14676.4s - 14856.4s] expo=180s elev=14.0deg humid=  0% sunelev=-12.0deg (moon at 151.0deg phase=0.10 elev= -2.0 )
AL_20170921_183939818_000000_86581801    12 stars filter C [14866.2s - 15046.2s] expo=180s elev=14.5deg humid=  0% sunelev=-12.6deg (moon at 151.0deg phase=0.10 elev= -2.0 )
AL_20170921_184303060_000000_86581901    14 stars filter C [15069.5s - 15249.5s] expo=180s elev=15.1deg humid=  0% sunelev=-13.2deg (moon at 151.0deg phase=0.10 elev= -3.0 )
AL_20170921_184613591_000000_86581901    14 stars filter C [15260.0s - 15440.0s] expo=180s elev=15.6deg humid=  0% sunelev=-13.7deg (moon at 151.0deg phase=0.10 elev= -3.0 )
AL_20170921_184923888_000000_86581901    11 stars filter C [15450.3s - 15630.3s] expo=180s elev=16.1deg humid=  0% sunelev=-14.3deg (moon at 151.0deg phase=0.10 elev= -4.0 )
AL_20170921_190351226_000000_86582001    13 stars filter C [16317.6s - 16497.6s] expo=180s elev=18.4deg humid=  0% sunelev=-16.8deg (moon at 151.0deg phase=0.10 elev= -6.0 )
AL_20170921_190701195_000000_86582001    14 stars filter C [16507.7s - 16687.7s] expo=180s elev=18.9deg humid=  0% sunelev=-17.3deg (moon at 151.0deg phase=0.11 elev= -7.0 )
AL_20170921_191011336_000000_86582001    14 stars filter C [16697.7s - 16877.7s] expo=180s elev=19.4deg humid=  0% sunelev=-17.9deg (moon at 151.0deg phase=0.11 elev= -8.0 )
AL_20170921_192818194_000000_86582101    12 stars filter C [17784.6s - 17964.6s] expo=180s elev=22.4deg humid=  0% sunelev=-21.0deg (moon at 151.0deg phase=0.11 elev=-11.0 )
AL_20170921_193128272_000000_86582101    14 stars filter C [17974.7s - 18154.7s] expo=180s elev=23.0deg humid=  0% sunelev=-21.5deg (moon at 151.0deg phase=0.11 elev=-11.0 )
AL_20170921_193438758_000000_86582101    14 stars filter C [18165.2s - 18345.2s] expo=180s elev=23.5deg humid=  0% sunelev=-22.0deg (moon at 151.0deg phase=0.11 elev=-12.0 )
AL_20170921_195251323_000000_86582201    13 stars filter C [19257.7s - 19437.7s] expo=180s elev=26.6deg humid=  0% sunelev=-25.0deg (moon at 151.0deg phase=0.11 elev=-15.0 )
AL_20170921_195601838_000000_86582201    16 stars filter C [19448.2s - 19628.2s] expo=180s elev=27.2deg humid=  0% sunelev=-25.5deg (moon at 151.0deg phase=0.11 elev=-16.0 )
AL_20170921_195912338_000000_86582201    14 stars filter C [19638.7s - 19818.7s] expo=180s elev=27.7deg humid=  0% sunelev=-26.0deg (moon at 151.0deg phase=0.11 elev=-16.0 )
AL_20170921_201730120_000000_86582301    15 stars filter C [20736.5s - 20916.5s] expo=180s elev=30.9deg humid=  0% sunelev=-28.8deg (moon at 151.0deg phase=0.11 elev=-19.0 )
AL_20170921_202040120_000000_86582301    15 stars filter C [20926.6s - 21106.6s] expo=180s elev=31.4deg humid=  0% sunelev=-29.3deg (moon at 151.0deg phase=0.11 elev=-20.0 )
AL_20170921_202350210_000000_86582301    16 stars filter C [21116.6s - 21296.6s] expo=180s elev=32.0deg humid=  0% sunelev=-29.8deg (moon at 151.0deg phase=0.11 elev=-20.0 )
AL_20170921_210617205_000000_86582501    16 stars filter C [23663.6s - 23843.6s] expo=180s elev=39.5deg humid=  0% sunelev=-35.7deg (moon at 152.0deg phase=0.11 elev=-27.0 )
AL_20170921_210927517_000000_86582501    15 stars filter C [23853.9s - 24033.9s] expo=180s elev=40.1deg humid=  0% sunelev=-36.1deg (moon at 152.0deg phase=0.11 elev=-28.0 )
AL_20170921_211237799_000000_86582501    14 stars filter C [24044.2s - 24224.2s] expo=180s elev=40.7deg humid=  0% sunelev=-36.5deg (moon at 152.0deg phase=0.11 elev=-28.0 )
AL_20170921_215524826_000000_86582701    16 stars filter C [26611.2s - 26791.2s] expo=180s elev=48.4deg humid=  0% sunelev=-41.3deg (moon at 152.0deg phase=0.11 elev=-35.0 )
AL_20170921_215834841_000000_86582701    16 stars filter C [26801.3s - 26981.3s] expo=180s elev=49.0deg humid=  0% sunelev=-41.6deg (moon at 152.0deg phase=0.11 elev=-35.0 )
AL_20170921_220144935_000000_86582701    16 stars filter C [26991.3s - 27171.3s] expo=180s elev=49.5deg humid=  0% sunelev=-41.8deg (moon at 152.0deg phase=0.11 elev=-36.0 )
Informations from GCN notice:
This is a GRB
Date of the alert : 2458018.10333912 2017-09-21T14:28:48.500
Decoded useful notice informations.
RA(J2000.0) : 26.8495 01h47m23s8
DEC(J2000.0) : 30.8742 +30d52m27s11
Error radius : 3.0 arcmin

Other pages about TAROT Calern observatory observations

Sum of images.
Differential photometry.

Galactic coordinates

Galactic coordinates : lon=136.863681943 lat=-30.4791554445
NASA/IPAC-Extragalactic-Database tool for calculate an extinction

Extinction from Schlegel et al. (1998, ApJ 500, 525): E(B-V)=0.046
Assuming Rv=3.1: Av=0.153 Ar=0.123 Ai=0.090 Extinction map E(B-V) from Schlegel:

Field of View is about 78 arcmin (north is NOT up !)

Bibliography (Last GCNC circulars and status of satellites)

GCN infos of this burst
GCN notice of this burst
Sloan Digital Sky Survey Observations of Gamma Ray Burst Fields
GCN info bursts
Gamma-ray burst real-time sky map
ROTSE last GRB images

Example of a GCNC email for this burst
GRB 170921: TAROT Calern observatory optical observations
Klotz A., Turpin D., Atteia J.L. (CNRS-OMP-IRAP),
Boer, M., Laugier, R. (CNRS-ARTEMIS),
Gendre B. (UVI - Etelman Obs.) report:

We imaged the field of GRB 170921 detected by SWIFT
(trigger 773509) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.

The observations started 3.86h after the GRB trigger.
The elevation of the field increased from
12 degrees above horizon and weather conditions
were XXX.

---- NO
The date of trigger : t0 = 2017-09-21T14:28:48.500

The first image is trailed with a duration of 180.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
We do not detect any OT with a limiting magnitude of:
t0+13892.5s to t0+14072.5s : R > 15.1

The second image is 180.0s exposure in tracking mode:
t0+14083.1s to t0+14263.1s : R > 16.2

We co-added a series of exposures:
t0+14083.1s to t0+15249.5s : R > 17.7
---- YES
We detect a new fading source in the error box given by SWIFT
We detected the candidate couterpart mentioned by XXX et al. (GCNC XXXX)
at the following position (+/- 3 arcsec):

RA(J2000.0) = XXh XXm XX.XXs
DEC(J2000.0) +XXd XX' XX.X"

OT was R~XX.X at 3.86h after GRB.

Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.

N.B. Galactic coordinates are lon=136.8637 lat=-30.4792
and the galactic extinction in R band is 0.1 magnitudes
estimated from D. Schlegel et al. 1998ApJ...500..525S.

This message may be cited.