F.E. Marshall (NASA/GSFC) for the Swift team
Yu and Goldstein (GCN Circ. 16224) reported the GRB detection. At 03:03:54.60 UT on 08 May 2014, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 140508A (trigger 421211037 / 140508128). Table 1 contains the best reported positions from Swift.
Singer et al. (GCN Circ. 16226) reported the position from iPTF for the optical afterglow of this GRB. Marshall and Amarel-Rogers (GCN Circ. 16243) reported the detection with UVOT of an optical afterglow. Malesani et al. (GCN Circ. 16229) determined a redshift of 1.03 from NOT, and Wiersema et al. (GCN Circ. 16231) determined a redshift of 1.027 from WHT. Table 2 is a summary of GCN Circulars about this GRB from observatories other than Swift.
BAT did not observe this burst.
We have analysed 17 ks of XRT data for the Fermi/GBM-detected burst: GRB 140508A, from 69.0 ks to 1020.7 ks after the Fermi/GBM trigger. The data are entirely in Photon Counting (PC) mode. An X-ray source is detected within the Fermi/GBM error circle.
The light curve (Figure 2) can be modelled with a power-law decay with a decay index of α=1.41 ± 0.10.
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.98 (+0.23, -0.22). The best-fitting absorption column is 1.4 (+1.5, -1.4) x 1
A summary of the PC-mode spectrum is thus:
Galactic foreground: 2.1 x 1
Intrinsic column: 1.4 (+1.5, -1.4) x 1
Photon index: 1.98 (+0.23, -0.22)
The results of the XRT team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00020376.
The Swift/UVOT began settled observations of the field of GRB 140508A 68965 s after the GBM trigger (Yu and Goldstein, GCN Circ. 16224)
(Marshall and Amarel-Rogers GCN Circ. 16243).
A source consistent with the optical position (Singer et al., GCN Circ. 16226) and the X-ray position (Amarel-Rogers, GCN Circ. 16232) is detected in the initial UVOT exposures.
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
Figure 1. The BAT light curve is not available.
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 |
---|---|---|---|---|
1 |
+46°46'49.5" | 0.46" | UVOT-refined | Marshall and Amarel-Rogers GCN Circ. 16243 |
1 |
+46°46'49.2" | 1.8" | XRT-final | UKSSDC |
1 |
+46°46'49.2" | 1.8" | XRT | GCN Circ. 16232 |
Band | Authors | GCN Circ. | Subject | Observatory | Notes |
---|---|---|---|---|---|
Optical | Singer et al. | 16226 | iPTF optical transient candidate | iPTF | detection |
Optical | Gorosabel et al. | 16227 | 1.23m CAHA BVRI-band observations | CAHA | detection |
Optical | Moskvitin et al. | 16228 | SAO RAS and MASTER photometric and spectroscopic observations |
MASTER | |
Optical | Malesani et al. | 16229 | NOT photometry and spectroscopy | NOT | spectroscopy |
Optical | Wiersema et al. | 16231 | WHT spectroscopy | WHT | spectroscopy |
Optical | Masi | 16235 | Optical Observations via Virtual Telescope |
Virtual Telescope | |
Optical | Butler et al. | 16236 | RATIR Optical and NIR Observations | RATIR | detection |
Optical | Bhalerao | 16244 | HCT spectroscopy | Himalayan Chandra Telescope | spectroscopy |
Optical | Butler et al. | 16246 | Continued RATIR Optical and NIR Observations |
RATIR | detection |
Optical | Fujiwara et al. | 16259 | MITSuME Akeno Optical observation | MITSuME Akeno | detection |
Optical | Volnova et al. | 16260 | Mondy upper limit | Mondy | upper limits |
Radio | Horesh et al. | 16266 | VLA detection | VLA | detection |
Gamma-ray | Yu and Goldstein | 16224 | Fermi GBM detection | Fermi GBM | Fluence=6.24±0.07x1 (96.1 percentile for long GRBs) |
Gamma-ray | Hurley et al. | 16225 | IPN triangulation | IPN | |
Gamma-ray | Golenetskii et al. | 16234 | Konus-Wind observation | Konus-Wind | Fluence=7.4(-0.7,+0.8)x1 |
Filter | Exp(s) | Mag | ||
---|---|---|---|---|
v | 68965 | 69792 | 814 | 19.38 ± 0.10 |
b | 70632 | 71427 | 782 | 19.59 ± 0.06 |
u | 69799 | 70626 | 814 | 18.81 ± 0.05 |
Table 3. UVOT observations reported by Marshall and Amarel-Rogers (GCN Circ. 16243). 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.
May 20, 2014