Swift Observations of GRB 160816A

J.A. Kennea (PSU) and P. Kuin (UCL/MSSL) for the Swift team

1. Introduction

Racusin et al. (GCN Circ. 19802) reported the GRB detection. At 17:30:58 on August 16, 2016 Fermi-LAT detected high-energy emission from GRB 160816A, which was also detected by Fermi-GBM (trigger 493061460 / 160816730). Table 1 contains the best reported positions from Swift.

Troja et al. (GCN Circ. 19809) reported the position from RATIR for the optical afterglow of this GRB. Kuin et al. (GCN Circ. 19815) reported the detection with UVOT of an optical afterglow. Table 2 is a summary of GCN Circulars about this GRB from observatories other than Swift.

2. BAT Observations and Analysis

BAT did not observe this burst.

3. XRT Observations and Analysis

XRT refined results are not available.

4. UVOT Observations and Analysis

The Swift/UVOT began settled observations (Kuin et al. GCN Circ. 19815) of the field of the Fermi/LAT- detected GRB 160816A 25222 s after the LAT trigger (Racusin et al. GCN Circ. 19802). A source consistent with the XRT position (Kennea et al. GCN Circ. 19806) and the LCOGT Faulkes Telescope North position (Guidorzi et al., GCN Circ. 19808) is detected in the initial UVOT exposures at the same position as reported by RATIR (Troja et al. GCN. Table 3 gives preliminary magnitudes using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc., 1358, 373). No correction has been made for the expected extinction in the Milky Way corresponding to a reddening of EB-V of 0.25 mag. in the direction of the GRB (Schlegel et al. 1998).

Figure 1. The BAT light curve is not available.

XRT light curve

Figure 2. The XRT light curve. Any data from a crosshatched region are not included in the fit.

RA (J2000) Dec (J2000) Error Note Reference
21h29m38.71s +37°07'58.3" 1.6" XRT-final UKSSDC
21h29m38.59s +37°07'56.6" 3.8" XRT Kennea et al. GCN Circ. 19806

Table 1. Positions from the Swift instruments.

Band Authors GCN Circ. Subject Observatory Notes
Optical Lipunov et al. 19805 MASTER inspection MASTER upper limits
Optical Guidorzi et al. 19808 LCOGT-FTN optical candidate FTN detection
Optical Troja et al. 19809 RATIR Optical and NIR Observations RATIR
Optical Kitaoka et al. 19818 iTelescope observation iTelescope
Optical Guidorzi et al. 19819 confirmed fading with the LT Liverpool Telescope
Optical Troja et al. 19820 RATIR Optical and NIR Afterglow
Confirmation		 RATIR detection
Optical Tyurina et al. 19821 MASTER OT early detection on coaded
images		 MASTER detection
Optical Troja et al. 19824 Further RATIR Optical and NIR
Observations		 RATIR detection
Optical Mazaeva et al. 19825 ISON/UAFO optical observations ISON-Ussuriysk detection
Optical Mazaeva et al. 19829 TSHAO optical observations Zeiss-1000 detection
Radio Mooley et al. 19892 Possible radio afterglow detection at
15 GHz with AMI		 AMI possible detection
Gamma-ray Racusin et al. 19802 Fermi-LAT detection Fermi LAT Emax=9.5 GeV
Gamma-ray Mailyan and Meegan 19804 730A: Fermi GBM detection/observation Fermi GBM Epeak=235±4.29 keV
T90=11.0 seconds
Fluence=3.467±0.037x10-5erg cm-2
(92nd percentile for long GRBs)
Gamma-ray Svinkin et al. 19810 Konus-Wind observation Konus-Wind Epeak=239 (-11,+12) keV
Duration=~14 seconds
Fluence=3.16(-0.10,+0.11)x10-5erg cm-2
Gamma-ray Hurley et al. 19814 IPN annulus IPN
Other 19881 the review of the sky area in plate
archives

Table 2. Summary of GCN Circulars from other observatories sorted by band and then circular number.

Filter Tstart(s) Tstop(s) Exp(s) Mag
white 27601 43846 879 21.48 ± 0.22
v 27661 27703 41 >17.9
u 25222 37523 2287 21.37 ± 0.31

Table 3. UVOT observations reported by Kuin et al. (GCN Circ. 19815). The start and stop times of the exposures are given in seconds since the BAT trigger. The preliminary detections and 3-σ upper limits are given. No correction has been made for extinction in the Milky Way.

September 6, 2016