Swift Observations of GRB 150204A

J.R. Cummings (CPI.com), A. Melandri (INAF-OAB) and A. Breeveld (MSSL-UCL) for the Swift team

1. Introduction

At 06:31:08, a GRB occurred during a preplanned Swift slew (Cummings GCN Circ. 17404). This was the same event as Fermi GBM trigger 444724270. Table 1 contains the best reported positions from Swift.

Table 2 is a summary of GCN Circulars about this GRB from observatories other than Swift.

2. BAT Observations and Analysis

The burst was a single symmetric cusp. T₉₀ was 12 ± 2 seconds.

3. XRT Observations and Analysis

XRT results are not available.

4. UVOT Observations and Analysis

The Swift/UVOT observed the field of GRB 150204A during follow-up observations, 51182 s after the BAT trigger (Breeveld et al. GCN Circ. 17411). No optical afterglow consistent with the possible XRT counterpart (A. 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 E_B-V of 0.824 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

10^h40^m57.04^s -64°02'19.2" 4.9" XRT-final UKSSDC

10^h40^m56.95^s -64°02'19.3" 4.8" XRT GCN Circ. 17409

10^h40^m57.8^s -64°02'34" 1.5' BAT-refined Stamatikos et al. GCN Circ. 17406

Table 1. Positions from the Swift instruments.

Band Authors GCN Circ. Subject Observatory Notes

Optical Dichiara et al. 17412 LCOGT-Sutherland and Siding Springs
observations LCO

Optical Kann et al. 17430 GROND observations GROND detection

Gamma-ray Burns and Yu 17408 Fermi GBM detection Fermi GBM E_peak=350±143 keV
T₉₀=10 seconds
Fluence=2.2±0.2x10^-6erg cm^-2
(31^st percentile for long GRBs)

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

Filter T_start(s) T_stop(s) Exp(s) Mag

v 57368 58276 885 >19.5

u 52088 52670 568 >19.5

w1 51182 63642 1495 >20.3

m2 58281 63016 1027 >20.1

w2 56461 57361 886 >19.9

RA (J2000)	Dec (J2000)	Error	Note	Reference
10^h40^m57.04^s	-64°02'19.2"	4.9"	XRT-final	UKSSDC
10^h40^m56.95^s	-64°02'19.3"	4.8"	XRT	GCN Circ. 17409
10^h40^m57.8^s	-64°02'34"	1.5'	BAT-refined	Stamatikos et al. GCN Circ. 17406

Band	Authors	GCN Circ.	Subject	Observatory	Notes
Optical	Dichiara et al.	17412	LCOGT-Sutherland and Siding Springs observations	LCO
Optical	Kann et al.	17430	GROND observations	GROND	detection
Gamma-ray	Burns and Yu	17408	Fermi GBM detection	Fermi GBM	E_peak=350±143 keV T₉₀=10 seconds Fluence=2.2±0.2x10^-6erg cm^-2 (31^st percentile for long GRBs)

Filter	T_start(s)	T_stop(s)	Exp(s)	Mag
v	57368	58276	885	>19.5
u	52088	52670	568	>19.5
w1	51182	63642	1495	>20.3
m2	58281	63016	1027	>20.1
w2	56461	57361	886	>19.9

Table 3. UVOT observations reported by Breeveld et al. (GCN Circ. 17411). The start and stop times of the exposures are given in seconds since the BAT trigger. The preliminary 3-σ upper limits are given. No correction has been made for extinction in the Milky Way.

February 11, 2015