Swift Observations of GRB 150518A

B. Sbarufatti (INAF-OAB/PSU) and M. De Pasquale (MSSL-UCL) for the Swift team

1. Introduction

Kawamuro et al. (GCN Circ. 17825) reported the GRB detection. The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 21:42:14 UT. Table 1 contains the best reported positions from Swift.

Xu et al. (GCN Circ. 17829) reported the position from Xinglong for the optical afterglow of this GRB. Xu et al. (GCN Circ. 17832) determined a redshift of 0.256 from VLT. 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 results are not available.

4. UVOT Observations and Analysis

The Swift/UVOT began settled observations (De Pasquale and Cenko GCN Circ. 17828) of the field of GRB 150518A 10383 s after the MAXI-GSC trigger (Kawamuro et al. GCN Circ. 17825). 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 0.05 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

15^h36^m48.14^s +16°19'44.9" 3.8" XRT Sbarufatti et al. GCN Circ. 17827

Table 1. Positions from the Swift instruments.

Band Authors GCN Circ. Subject Observatory Notes

Optical Xu et al. 17829 Xinglong2.16m optical afterglow
detection Xinglong detection

Optical Mao et al. 17830 GMG observation Gao-Mei-Gu

Optical Littlejohns et al. 17831 RATIR optical observations RATIR detection

Optical Xu et al. 17832 VLT/X-shooter redshift of the likely
host galaxy VLT redshift

Optical Moskvitin 17834 SAO RAS optical observations SAO RAS

Optical Xin et al. 17835 Xinglong TNT upper limit TNT upper limits

Optical Gorbovskoy et al. 17838 MASTER-net before, early and after
optical stereoscopic observations with
possible MP discovery inside MAXI error
box MASTER

Optical Mazaeva et al. 17840 Mondy optical observations Mondy detection

Optical Harita et al. 17841 MITSuME Akeno Optical observation MITSuME Akeno detection

Optical Littlejohns et al. 17861 Continued RATIR optical observations RATIR

Radio Anderson et al. 17839 AMI 15 GHz detection of possible radio
counterpart AMI possible detection

Radio 17859 6.0 GHz VLA detection VLA detection

X-ray Kawamuro et al. 17825 MAXI/GSC detection MAXI detection

X-ray Sakamoto et al. 17860 MAXI-GSC further analysis MAXI light curve

Gamma-ray Golenetskii et al. 17837 Konus-Wind observation Konus-Wind

Other Negoro et al. 17833 Correction

Other Pozanenko et al. 17903 possible SN observations detection

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 U.L.

u 10383 20164 364 >20.3

RA (J2000)	Dec (J2000)	Error	Note	Reference
15^h36^m48.14^s	+16°19'44.9"	3.8"	XRT	Sbarufatti et al. GCN Circ. 17827

Band	Authors	GCN Circ.	Subject	Observatory	Notes
Optical	Xu et al.	17829	Xinglong2.16m optical afterglow detection	Xinglong	detection
Optical	Mao et al.	17830	GMG observation	Gao-Mei-Gu
Optical	Littlejohns et al.	17831	RATIR optical observations	RATIR	detection
Optical	Xu et al.	17832	VLT/X-shooter redshift of the likely host galaxy	VLT	redshift
Optical	Moskvitin	17834	SAO RAS optical observations	SAO RAS
Optical	Xin et al.	17835	Xinglong TNT upper limit	TNT	upper limits
Optical	Gorbovskoy et al.	17838	MASTER-net before, early and after optical stereoscopic observations with possible MP discovery inside MAXI error box	MASTER
Optical	Mazaeva et al.	17840	Mondy optical observations	Mondy	detection
Optical	Harita et al.	17841	MITSuME Akeno Optical observation	MITSuME Akeno	detection
Optical	Littlejohns et al.	17861	Continued RATIR optical observations	RATIR
Radio	Anderson et al.	17839	AMI 15 GHz detection of possible radio counterpart	AMI	possible detection
Radio		17859	6.0 GHz VLA detection	VLA	detection
X-ray	Kawamuro et al.	17825	MAXI/GSC detection	MAXI	detection
X-ray	Sakamoto et al.	17860	MAXI-GSC further analysis	MAXI	light curve
Gamma-ray	Golenetskii et al.	17837	Konus-Wind observation	Konus-Wind
Other	Negoro et al.	17833	Correction
Other	Pozanenko et al.	17903	possible SN observations		detection

Filter	T_start(s)	T_stop(s)	Exp(s)	Mag	U.L.
u	10383	20164	364	>20.3

Table 3. UVOT observation reported by De Pasquale and Cenko (GCN Circ. 17828). The start and stop time of the exposure are given in seconds since the BAT trigger. The preliminary 3-σ upper limit is given. No correction has been made for extinction in the Milky Way.

June 7, 2015