GRB 160417A

P. D'Avanzo (INAF-OAB), A. Melandri (INAF-OAB), D. M. Palmer (LANL),
B. Sbarufatti (INAF-OAB/PSU) and M. H. Siegel (PSU) report on behalf
of the Swift Team:

At 04:23:41 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160417A (trigger=683076).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 120.240, +7.671 which is 
   RA(J2000) = 08h 00m 58s
   Dec(J2000) = +07d 40' 15"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex peak
structure with a duration of about 30 sec.  The peak count rate
was ~1100 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 04:25:53.1 UT, 132.2 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 120.25774, 7.66265 which
is equivalent to:
   RA(J2000)  = 08h 01m 01.86s
   Dec(J2000) = +07d 39' 45.5"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 70 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 2.92
x 10^20 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 135 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	08:01:01.64 = 120.25682
  DEC(J2000) = +07:39:46.4  =	7.66290
with a 90%-confidence error radius of about 0.64 arc sec. This position is 4.4
arc sec. from the center of the XRT error circle. The estimated magnitude is
19.15 with a 1-sigma error of about  0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.02. 

Burst Advocate for this burst is P. D'Avanzo (paolo.davanzo AT brera.inaf.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.)

WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report
on behalf of the KAIT GRB team:

The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to Swift GRB 160417A (D'Avanzo et al.,
GCN 19316
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 ) about 10 minutes after the trigger. Observations were
performed with an automatic sequence in the clear (roughly R), V,
and I filters, and the exposure time was 20 s per image.
Inside the XRT error circle we detected an un-cataloged 
source with coordinates of :

RA =  08:01:01.64 (J2000)
DEC= +07:39:46.60 (J2000)

The object location is consistent with the position reported
from UVOT (D'Avanzo et al., GCN 19316
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 ). The object has clear band mag
of ~17.9 about 10 minutes after the burst.

Follow-up observations are encouraged.

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

Using 1095 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 160417A, 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 = 120.25686, +7.66288 which is equivalent
to:

RA (J2000): 08h 01m 1.65s
Dec (J2000): +07d 39' 46.4"

with an uncertainty of 1.8 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.

D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ),
S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto)
and N. Kawai(Tokyo Tech)
report on behalf of MITSuME and OISTER collaboration:

We observed the field of GRB 160417A (D'Avanzo et al., GCNC 19316)
with the optical three color (g', Rc and Ic) CCD camera attached
to the MITSuME 50cm telescope of Okayama Astrophysical Observatory.

The observation started on 2016-04-17 11:06:00 UT (~6.7 h after
the burst). We could not detect the previously reported afterglow
(D'Avanzo et al., GCNC 19316; Zheng et al., GCNC 19317)
in all the three bands.

Three sigma upper limits of the OT are listed below.
We used SDSS-DR8 catalog for flux calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'    Rc     Ic
-----------------------------------------------------
0.32136    12:06:26    5640.0   >19.7  >19.7  >18.9
-----------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]

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

We have analysed 8.0 ks of XRT data for GRB 160417A (D'Avanzo et al.
GCN Circ. 19316
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 ), from 117 s to 23.2 ks after the  BAT trigger. The
data comprise 41 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. 19318
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 ).

The light curve can be modelled with an initial power-law decay with an
index of alpha=4.4 (+0.4, -0.3), followed by a break at T+305 s to an
alpha of 0.59 (+/-0.06).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.05 (+0.15, -0.08). The
best-fitting absorption column is  consistent with the Galactic value
of 2.9 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 3.1 x 10^-11 (3.4 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     2.9 (+/-1.9) x 10^20 cm^-2
Galactic foreground: 2.9 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     2.05 (+0.15, -0.08)

If the light curve continues to decay with a power-law decay index of
0.59, the count rate at T+24 hours will be 0.013 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.9 x
10^-13 (4.3 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00683076.

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

Veli-Pekka Hentunen, Markku Nissinen and Tuomo Salmi (Taurus Hill
Observatory, Varkaus, Finland) report:

We have detected GRB 160417A optical afterglow at iTelescope observatory
T11 (Mayhill, New Mexico) using 0.50-m f/6.8 astrograph and FLI
PL11002M CCD. The observations were started at 2016-04-17
05:08:31 (UT). Two unfiltered images with 300 sec exposure time were taken.

The afterglow was detected at the position RA 08:01:01.65 and DEC
+07:39:47.6.

The following magnitude was obtained from the observations using
USNO-B1.0 0976-0191477 (R2=16.67) as a comparison star:

Tmid(s)+T0       Filter         Exp. time         Mag              Mag. Err.
2996                 Clear         2x300s           18.6CR          0.3

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A. A. Breeveld (UCL-MSSL) and P. D'Avanzo (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160417A
136 s after the BAT trigger (D'Avanzo et al., GCN Circ. 19316
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 ).
The source reported for the UVOT in the initial GCN and also by Zheng 
and Filippenko (GCN Circ. 19317
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 ) is found to be fading.

The preliminary UVOT position is:
     RA  (J2000) =  08:01:01.64 = 120.25685 (deg.)
     Dec (J2000) = +07:39:46.4  =   7.66289 (deg.)
with an estimated uncertainty of 0.46 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              136          285          147         18.92 �� 0.07
white              870         1020          147         19.14 0.10
v                  623         1070           58         18.54 �� 0.31
b                  549         1169           58         19.07 �� 0.21
u                  294          543          246         18.08 �� 0.08
w1                 672         1280           64        >18.9
m2                 647         1268           78        >19.1
w2                 599         1220           78        >18.8

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).

S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
P. D'Avanzo (INAF-OAB), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
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 the recent
telemetry downlink, we report further analysis of BAT
GRB 160417A (trigger #683076) (D'Avanzo, et al.,
GCN Circ. 19316
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 ).  The BAT ground-calculated position is
RA, Dec = 120.260, 7.646 deg which is
   RA(J2000)  =  08h 01m 02.4s
   Dec(J2000) = +07d 38' 45.6"
with an uncertainty of 1.9 arcmin, (radius, sys+stat,
90% containment). The partial coding was 41%.

The mask-weighted light curve shows a multi-peak episode
starting ~T-4 sec, and ending around ~T+20 sec.
T90 (15-350 keV) is 15 +- 2 sec (estimated error including
systematics).

The time-averaged spectrum from T-2.14 to T+13.89 sec
is best fit by a simple power-law model.  The power law index
of the time-averaged spectrum is 1.93 +- 0.24.  The fluence
in the 15-150 keV band is 5.9 +- 0.8 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T+1.51 sec in the
15-150 keV band is 1.0 +- 0.3 ph/cm2/sec.  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/683076/BA/

J.-J. Zhang, J. Mao, and J.-M. Bai (YNAO) report:


We observed the field of GRB 160417A (D'Avanzo et al., GCN 19316
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 ) with the 2.4-meter optical telescope at Gao-Mei-Gu (GMG)
station of Yunnan Observatories. Observations began from 12:30:03 UT, Apr. 17th, 2016, about 8.2 hours after the trigger. 
We obtained the following results at the afterglow position: r~21.1+/- 0.3 mag, i>20.9 mag, and g>21.8 mag.

V. V. Golovnia (Main Astro Obs., Kyiv)
report:
We have undertaken the review of the sky area of GRB 160417A (J.P. Osborne
et al. GCN Circ. 19318
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 ) on astronegatives, collected in Ukrainian plate
archive (1976-1996). All the plates with the possible object appearance are
digitized using Epson Expression 10000XL flatbed scanner and the images
have been placed into Golosiiv Plate Archive database DBGPA with open
access to them. The list of plates is given in the table:

yyyymmdd/TstartUT- ---Plates--- -Exp. Mag --USNO-A2--
19930202/21:16:48 GUA040C002102 18.9 14.8 0975-05657018
19930216/20:33:08 GUA040C002131 19.5 16.0 0975-05654878
19930312/18:39:20 GUA040C002146 22.5 15.3 0975-05651231

Plates -the plates archive identifier of DWA D/F=400/2000, M=103"/mm
(Marsden's number - 083) the plate number [1].
Exp. - Duration of the maximum exposures (minutes).
Mag - Limited Bmag, derived in the 9 minutes area around the location
given in J.P. Osborne et al.(GCN Circ. 19318
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 ):
RA(J2000): 08h 01m 01.64s, Dec(J2000): +07d 39' 46.1".
USNO-A2 - Comparison star.
The preview images of 3 areas together with the 9 min. of arc area
from Aladin can be found in
http://gua.db.ukr-vo.org/img/grb/160417A/index.html.
The images with full resolution are available via e-mail on demand.

References:
1.L.Pakuliak DATABASE of GOLOSIIV PLATE ARCHIVE (DBGPA V2.0),
http://gua.db.ukr-vo.org.

K. P. Mooley, T. D. Staley, R. P. Fender (Oxford), G. E. Anderson 
(Curtin), T. Cantwell (Manchester), C. Rumsey, D. Titterington, S. 
Carey, J. Hickish, Y. C. Perrott, N. Razavi-Ghods, P. Scott (Cambridge), 
K. Grainge, A. Scaife (Manchester)

The AMI Large Array robotically triggered on the Swift alert for GRB 
160417A (D'Avanzo et al., GCN 19316
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 ) as part of the 4pisky program, and 
subsequent follow up observations were obtained up to 10 days 
post-burst. Our observations at 15 GHz on 2016 Apr 17.58, Apr 18.81, Apr 
20.66, Apr 24.68, and Apr 28.77 (UT) do not reveal any radio source at 
the XRT location (Osborne et al., GCN 19318
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 ), with 3sigma upper limits 
of 225 uJy, 105 uJy, 123 uJy, 72 uJy, and 96 uJy respectively.

We thank the AMI staff for scheduling these observations. The AMI-GRB 
database is a log of all GRB follow up observations with the AMI, and is 
available at http://4pisky.org/ami-grb/.