GRB 150607A

V. D'Elia (ASDC), L. Izzo (URoma/ICRA), J. A. Kennea (PSU),
K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Swift Team:

At 07:55:09 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150607A (trigger=642620).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 140.024, +68.442 which is 
   RA(J2000) = 09h 20m 06s
   Dec(J2000) = +68d 26' 33"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multiply-peaked
structure with a duration of about 50 sec.  The peak count rate
was ~3000 counts/sec (15-350 keV), at ~8 sec after the trigger. 

The XRT began observing the field at 07:57:20.5 UT, 130.9 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 139.9916, 68.4368 which is equivalent to:
   RA(J2000)  = +09h 19m 57.98s
   Dec(J2000) = +68d 26' 12.5"
with an uncertainty of 6.5 arcseconds (radius, 90% containment). This
location is 46 arcseconds from the BAT onboard position, within the BAT
error circle. 

The initial flux in the 2.5 s image was 4.64e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 136 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	09:19:57.18 = 139.98825
  DEC(J2000) = +68:26:10.2  =  68.43618
with a 90%-confidence error radius of about 0.75 arc sec. This position is 5.0
arc sec. from the center of the XRT error circle. The estimated magnitude is
18.06 with a 1-sigma error of about  0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.06. 

Burst Advocate for this burst is V. D'Elia (delia AT asdc.asi.it). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)

J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1781 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 150607A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 139.98854, +68.43599 which is equivalent
to:

RA (J2000): 09h 19m 57.25s
Dec (J2000): +68d 26' 09.6"

with an uncertainty of 1.7 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.

O.J. Roberts (UCD) reports on behalf of the Fermi GBM Team:

"At 07:55:09.85 UT on the 7th of June 2015, the Fermi
Gamma-Ray Burst Monitor triggered and located GRB 150607A
(trigger 455356512 / 150607330), which was also detected
by Swift (D'Elia  et al. 2015, GCN 17904
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 ). The GBM
on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight using this position
is about 130 degrees.

The GBM light curve shows several bright pulses over a
duration (T90) of 31.8 s (50-300 keV). The time-averaged
spectrum from T0-1.7 s to T0+30.1 s is well fit by power
law function with an exponential high-energy cutoff. The
power law index is -0.98 +/- 0.17 and the cutoff energy,
parameterized as Epeak, is 137 +/- 22 keV.

The event fluence (10-1000 keV) in this time interval is
(4.4 +/- 0.4)E-06 erg/cm^2. The 1.024-sec peak photon
flux measured starting from T0+6.8 s in the 10-1000 keV
band is 6.8 +/- 0.5 ph/s/cm^2.

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

D. M. Palmer (LANL), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), V. D'Elia (ASDC), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
 
Using the data set from T-239 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 150607A (trigger #642620)
(D'Elia, et al., GCN Circ. 17904
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 ).  The BAT ground-calculated position is
RA, Dec = 140.015, 68.436 deg, which is 
   RA(J2000)  =  09h 20m 03.6s 
   Dec(J2000) = +68d 26' 10.3" 
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 31%.
 
The mask-weighted light curve shows multiple peaks starting at ~T-2 sec,
the brightest peak at ~T+8 sec, and ending at ~T+40 sec.
T90 (15-350 keV) is 26.3 +- 0.7 sec (estimated error including systematics).
 
The time-averaged spectrum from T-0.19 to T+27.58 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.99 +- 0.41, 
and Epeak of 84.9 +- 40.1 keV (chi squared 40.9 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 2.3 +- 0.2 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+7.29 sec in the 15-150 keV band is
4.9 +- 0.5 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.59 +- 0.10 (chi squared 48.1 for 57 d.o.f.).  All the quoted errors
are at the 90% confidence level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/642620/BA/

T. Kruehler (ESO) & A. A. Djupvik (NOT) report on behalf of a larger
collaboration:

We observed the field of GRB 150607A (D'Elia et al., GCN 17904
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 ) using
the Nordic Optical Telescope equipped with the ALFOSC camera.

A short series of photometry in BVRI filters was taken starting at
2015-06-07 21:43UT. The optical afterglow (D'Elia et al., GCN 17094
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 ) of
GRB 150607A is well detected in our images. We measure R = 21.6 +/- 0.2
mag at 13.76 hours after the trigger, calibrated against magnitudes
of nearby stars from the USNO-B1 catalog.

L. M. Z. Hagen (PSU) and V. D'Elia (ASDC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150607A
137 s after the BAT trigger (D'Elia et al., GCN Circ. 17904
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 ). A source
consistent with the XRT position (Osborne et al. GCN Circ. 17905
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 ) is
detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  09:19:57.20 = 139.98833 (deg.)
    Dec (J2000) = +68:26:10.3  =  68.43619 (deg.)
with an estimated uncertainty of 0.44 arc sec. (radius, 90% confidence).

Preliminary detections and 3-sigma upper limits 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              137          286          146         18.10 +/- 0.07
white              628         1204          205         20.04 +/- 0.31
white             1358         7668          412        >20.55
v                  118          128            9         16.71 +/- 0.35
v                  678         7955          446        >19.02
b                  604         7463          367        >19.65
u                  348          598          245         18.88 +/- 0.27
u                  753         7258          352        >19.37
uvw1               728         7053          352        >19.60
uvm2              1084         6848          313        >19.74
uvw2               654         7874          568        >20.30

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.07 in the direction of the burst
(Schlegel et al. 1998).

D.N. Burrows (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU),
A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), A.
Amaral-Rogers (U. Leicester), A. D'ai (INAF-IASFPA), A. Maselli 
(INAF-IASFPA) and V. D'Elia report on behalf of the Swift-XRT team:

We have analysed 7.7 ks of XRT data for GRB 150607A (D'Elia et al. GCN
Circ. 17904
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 ), from 118 s to 47.9 ks after the  BAT trigger. The data
comprise 44 s in Windowed Timing (WT) mode (the first 8 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Osborne et
al. (GCN Circ. 17905
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 ).

The light curve can be modelled with an initial power-law decay with an
index of alpha=0.77 (+/-0.06), followed by a break at T+4216 s to an
alpha of 1.11 (+0.26, -0.09).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.82 (+0.11, -0.10). The
best-fitting absorption column is  2.2 (+/-0.4) x 10^21 cm^-2, in
excess of the Galactic value of 5.7 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 4.0 x 10^-11 (5.1 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     2.2 (+/-0.4) x 10^21 cm^-2
Galactic foreground: 5.7 x 10^20 cm^-2
Excess significance: 6.5 sigma
Photon index:	     1.82 (+0.11, -0.10)

If the light curve continues to decay with a power-law decay index of
1.11, the count rate at T+24 hours will be 0.020 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.8 x
10^-13 (1.0 x 10^-12) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00642620.

This circular is an official product of the Swift-XRT 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 150607A (Swift-BAT trigger #642620:
D'Elia, et al., GCN 17904
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 ; Palmer, et al., GCN 17907
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 ;
Fermi GBM detection: Roberts, GCN 17906
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 ) triggered Konus-Wind at 
T0=28509.211 s UT (07:55:09.211).

The burst light curve shows a multipeak structure
with a total duration of ~30 s.
The emission is seen up to ~1 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150607_T28509/

As observed by Konus-Wind, the burst
had a fluence of 4.2(-0.8,+1.3)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0-0.222 s,
of 1.2(-0.5,+0.6)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+33.024 s)
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -1.4(-0.3,+0.4)
and Ep = 173(-57,+183) keV (chi2 = 61/62 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2
(chi2 = 60/61 dof)

The spectrum near the maximum count rate
(measured from T0+0.000 to T0+8.448 s)
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -1.4(-0.3,+0.4)
and Ep = 152(-42,+108) keV (chi2 = 46/62 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2
(chi2 = 46/61 dof)

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

V. Toy (UMD), J. Capone (UMD), S.B. Cenko (NASA-GSFC), S. Veilleux (UMD),
A. Cucchiara (NASA-GSFC), E. Troja (NASA-GSFC),  and A. Kutyrev (NASA-GSFC)
report on behalf of a larger collaboration:

We observed the field of GRB150607A (Swift trigger 642620, D'Elia et al.,
GCN 17904
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 ) with the Large Monolithic Imager (LMI) on the 4.3m Discovery
Channel Telescope (DCT) at Happy Jack, AZ from 2015/06/08 03:42 to
2015/06/08 04:35 UTC (starting 19.8 hours after the trigger). A source is
clearly detected at the location of the optical afterglow in r', i', and
z'.  Using nearby point sources from USNO-B1.0 for calibration, we measure
r' = 22.03 +/- 0.03.

This magnitude is reported in AB magnitude and is not corrected for
Galactic extinction in the direction of the GRB.

Compared to NOT observations on 06/07 (Kruehler & Djupvik, GCN 17908
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 ) the
afterglow has a decay index of ~ t^-1.1.

We thank the staff of the Discovery Channel Telescope for assistance with
these observations.

E. Mazaeva (IKI), R. Inasaridze (AAO), S. Nazarov (CrAO), Sh. 
Makandarashvili (AAO), A. Volnova (IKI), I. Molotov (KIAM), A. Pozanenko 
(IKI) report on behalf of larger GRB follow-up collaboration:

We observed the field of GRB 150607A (Swift trigger 642620, D'Elia et 
al., GCN 17904
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 ) with the AS-32 (0.7m) telescope of Abastumani 
Observatory (AAO) starting on June, 07 17:54:22, and with AZT-8 
telescope of CrAO starting on June, 07 19:43:21.  The afterglow of GRB 
150607A (Kruehler et al., GCN 17908
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 ; Hagen et al., GCN 17909
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 ) is clearly 
detected in early observation in AAO. Preliminary photometry is following.

telescope  UT start   t-T0     Filter   Exp.     OT    Err.
                       (mid, days)       (s)

AS-32      17:54:22   0.45669  None     44*120   21.20 0.1
AZT-8      19:43:21   0.49864  R         6*180  >19.4 (3sigma)

Photometry is based on nearby USNO-B1.0 stars.