GRB 150514A

P.A. Evans (U. Leicester), M. de Pasquale (MSSL/UCL) and J. K. Cannizzo
(GSFC/UMBC) report on behalf of the Swift team

Swift has performed further observations of GRB 150514A (Kocevski and
Arimoto, GCN Circ. 17816
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 ), collecting a further 2 ks of data, from
T0+120.9 ks to T0+122.9 ks. The object previously detected in the XRT
(Kennea et al. GCN Circ. 17818
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 ) and UVOT (Marshall & Cannizzo, GCN Circ.
17820
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 ) has faded in both instruments.

The UVOT counterpart was detected with a white magnitude of 20.51
+/-0.15, which gives a power-law decay index of 1.63 +/- 0.15.
The X-ray counterpart was detected with a count-rate of
(1.04 +/- 0.03) x 10^-2 ct/sec, which gives a power-law decay index of
1.4 +/- 0.5, consistent with the slope measured from the UVOT data.

This circular is an official result of the Swift team.

S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration GRB 150514A
(Fermi-LAT detection:  Kocevski & Arimoto , GCN 17816
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 ;
Fermi-GBM detection:  Roberts, Zhang & Meegan GCN 17819
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 )
triggered Konus-Wind at 66905.130 s UT (18:35:05.130).

The KW light curve shows a single pulse with a duration of ~10 s.
The emission is visible up to ~5 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150514_T66905/

As observed by Konus-Wind, the burst had a fluence
of 3.7(-0.7,+0.7)x10^-6 erg/cm2, and a 64-ms peak flux,
measured from T0+0.448 s, of 3.4(-0.6,+0.6)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 15 MeV range
by the cutoff power law with the following model parameters:
the photon index alpha = -1.44(-0.29,+0.33),
and the peak energy Ep = 60(-14,+10) keV,
chi2 = 87/89 dof.
Fitting this spectrum with the GRB (Band) function yields
the following model parameters:
the low-energy photon index alpha = -1.25 (-0.23,+0.26),
the high energy photon index beta < -2.52 (upper limit),
the peak energy Ep = 58 (-9, +9) keV,
chi2 = 85/88 dof.

Assuming the redshift z=0.807 (de Ugarte Postigo et al., GCN 17822
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 )
and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.27, and Omega_Lambda = 0.73,
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~6.3x10^51 erg,
the peak luminosity L_iso is ~1.0x10^52 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,i, is ~108 keV.

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.

A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), D. Xu (NAOC/CAS), 
D. Malesani (DARK/NBI), N. R. Tanvir (U. Leicester) report on behalf of 
the X-shooter GRB collaboration:

We observed the optical afterglow of GRB 150514A (Kocevski et al. 
GCN 17816
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 , Kennea et al. GCN 17818
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 , Roberts et al. GCN 17819
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 , 
Marshall et al. GCN 17820
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 , Yates et al. GCN 17821
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 ) with X-shooter 
at the Very Large Telescope (Paranal Observatory, Chile). Observations 
started at 23:04 UT on 15 May 2015 (28.4 hr after the burst) and 
consisted of 4 x 600 s exposures covering the range between 3000 and 
24800 AA.

The afterglow is well detected in the acquisition image at R(Vega) = 
19.5 mag, calibrated with two nearby USNO B1 stars. The spectrum 
shows a clear continuum over the entire range and absorptions of FeII, 
MgII and MgI at a common redshift of 0.807, which we consider to be 
the redshift of the GRB.

We acknowledge the excellent support provided by Paranal staff, and in
particular John Pritchard and Dimitri Gadotti.

R. Yates, F. Knust (both MPE Garching), D. A. Kann (TLS Tautenburg), and
J. Greiner (MPE Garching) report on behalf of the GROND team:

We observed the field of GRB 150514A (Fermi trigger 453321308; LAT
detection: Kocevski et al., GCN # 17816; GBM detection: Roberts et al.,
GCN # 17819) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla
Observatory (Chile).

Observations started at 23:36 UT on 2015-05-15, 29.0 hrs after the GRB
trigger. They were performed at an average seeing of 1".5 and at an
average airmass of 2.1.

Coincident with the UVOT source reported by Marshall & Cannizzo (GCN #
17820), we detect a bright source.

Based on 7.7 min of total exposure time in g'r'i'z' and 8 min in JHK
centered 29.15 hrs after the GRB, we estimate the following preliminary
magnitudes (all in the AB system):

g' = 20.5 +/- 0.1 mag,
r' = 20.1 +/- 0.1 mag,
i' = 19.9 +/- 0.1 mag,
z' = 19.6 +/- 0.1 mag,
J = 19.2 +/- 0.2 mag, and
H = 18.6 +/- 0.2 mag.

Compared with the UVOT detections reported by Marshall & Cannizzo (GCN #
17820; 18th magnitude), the source has clearly faded, establishing it as
the afterglow of GRB 150514A.

We note that similar to other LAT-detected GRBs, this is a very bright
afterglow. Spectral follow-up is encouraged.

Given magnitudes are calibrated against GROND zero points (g'r'i'z') as
well as 2MASS field stars (JHK) and are not corrected for the expected
Galactic foreground extinction corresponding to a reddening of E_(B-V) =
0.02 mag in the direction of the burst (Schlegel et al. 1998).

F. E. Marshall (NASA/GSFC) and J. K. Cannizzo (GSFC/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150514A
40750 s after the LAT trigger (Kocevski and Arimoto, GCN Circ. 17816
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 ).
A source consistent with the XRT position (Kennea et al. GCN Circ. 17818
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 )
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  04:59:30.30 =  74.87623 (deg.)
    Dec (J2000) = -60:58:06.3  = -60.96841 (deg.)
with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence).

Preliminary detections using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: 

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

white            41402        41850          440         18.60 +/- 0.04
v                42049        42222          170         18.71 +/- 0.20
u                40750        41396          636         18.20 +/- 0.05

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).

O.J. Roberts (UCD), Bin-Bin Zhang (UAH) and
C.Meegan (UAH) report on behalf of the Fermi GBM Team:

"At 18:35:05.35 UT on the 14th of May 2015, the Fermi
Gamma-Ray Burst Monitor triggered and located GRB 150514A
(trigger 453321308 / 150514774), which was also detected
by Fermi-LAT (Kocevski et al. 2015, GCN 17816
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 ). An
afterglow likely to be from this event was also found by
Swift (Kennea et al. 2015, GCN 17818
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 ). The GBM on-ground
location is consistent with the LAT and Swift XRT positions.

The angle from the Fermi LAT boresight is about 38 degrees.

The GBM light curve consists of a single bright, FRED-like
pulse over a duration (T90) of 10.8 s (50-300 keV). The
time-averaged spectrum from T0+0.0 s to T0+11.3 s is well
fit by a Band function, with an Epeak = 73 +/- 6 keV,
alpha = -1.34 +/- 0.07, and beta = -2.51 +/- 0.17.

The event fluence (10-1000 keV) in this time interval is
(4.9 +/- 0.2)E-06 erg/cm^2. The 1.024-sec peak photon
flux measured starting from T0+0.5 s in the 10-1000 keV
band is 19.9 +/- 0.4 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."

J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), K.L. Page (U.
Leicester), C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester), A.
Maselli  (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB),
D.N. Burrows (PSU) and P.A. Evans (U. Leicester) report on behalf of
the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Fermi/LAT-detected burst GRB 150514A (Kocevski et al. GCN Circ. 17816
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 ),
collecting 1.3 ks of Photon Counting (PC) mode data between T0+40.8 ks
and T0+42.2 ks. 

Three uncatalogued X-ray sources are detected, of which one ("Source
1") is above the RASS limit, and is therefore likely the GRB afterglow.
 The position of this source is RA, Dec=74.8750, -60.9691 which is
equivalent to:

RA (J2000): 04:59:30.00
Dec(J2000): -60:58:08.8

with an uncertainty of 3.9 arcsec (radius, 90% confidence).  This
position is 3.6 arcmin from the Fermi/LAT position.  The light curve is
consistent with a constant source of mean count rate 5.4e-02 ct/sec. A
power-law fit gives an index of 3.17 (+0.05, -4.47).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.2 (+0.7, -0.4). The
best-fitting absorption column is  3 (+11, -1) x 10^20 cm^-2,
consistent with the Galactic value of 2.0 x 10^20 cm^-2 (Willingale et
al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum  is 2.9 x 10^-11 (3.3 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     3 (+11, -1) x 10^20 cm^-2
Galactic foreground: 2.0 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     2.2 (+0.7, -0.4)

The results of the XRT-team automatic analysis of the likely afterglow
are at http://www.swift.ac.uk/ToO_GRBs/00020510/index_1.php.
The results of the full analysis of the XRT observations are available
at http://www.swift.ac.uk/ToO_GRBs/00020510.

This circular is an official product of the Swift-XRT team.

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a ToO observation of the Fermi/LAT GRB 150514A. 
Automated analysis of the XRT data will be presented online at
http://www.swift.ac.uk/ToO_GRBs/00020510

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Fermi/LAT event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a 
GCN Circular after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.

D. Kocevski (NASA/GSFC) and M. Arimoto (Tokyo Tech),
report on behalf of the Fermi-LAT team:

At 18:35:05.35 on May 14, 2015, Fermi-LAT detected high-energy emission from GRB 150514A, which was also detected by Fermi-GBM (trigger 453321308).

The best LAT on-ground location is found to be

RA, Dec = 74.85, -60.91 (J2000)

with an error radius of 0.12 deg (90% containment, statistical error only). This position was 40 deg from the LAT boresight at the time of the trigger.

The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the GBM emission with high significance. The LAT localization relies heavily on the detection of a single 6.5 GeV event at T0 + 400s, roughly 2.2 deg from the final GBM position. The GRB was observable from T0 to T0 + 600 s, before the spacecraft entered the South Atlantic Anomaly, where data gathering is disabled.

The Fermi-LAT point of contact for this burst is Makoto Arimoto (arimoto@hp.phys.titech.ac.jp<mailto:arimoto@hp.phys.titech.ac.jp>).

The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.