GRB 180510A

J.D. Gropp (PSU), A. Deich (PSU), J. A. Kennea (PSU),
S. J. LaPorte (PSU), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),
B. Sbarufatti (PSU), M. H. Siegel (PSU) and A. Tohuvavohu (PSU) report
on behalf of the Neil Gehrels Swift Observatory Team:

At 19:24:34 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 180510A (trigger=831810).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 276.318, -31.911 which is 
   RA(J2000) = 18h 25m 16s
   Dec(J2000) = -31d 54' 38"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multi-peaked
structure with a duration of about 70 sec.  The peak count rate
was ~8000 counts/sec (15-350 keV), at ~5 sec after the trigger. 

The XRT began observing the field at 19:26:02.5 UT, 88.3 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 276.3303, -31.9069 which is equivalent to:
   RA(J2000)  = +18h 25m 19.27s
   Dec(J2000) = -31d 54' 24.8"
with an uncertainty of 5.5 arcseconds (radius, 90% containment). This
location is 40 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy. 

The initial flux in the 2.5 s image was 1.09e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 96 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. Because of the density of catalogued stars, further
analysis is required to report an upper limit for any afterglow in the
sub-image. Results from the list of sources generated on-board are not
available at this time. No correction has been made for the expected extinction
corresponding to E(B-V) of 0.26. 

Burst Advocate for this burst is J.D. Gropp (jdg44 AT psu.edu). 
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.)

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

We have analysed 4.9 ks of XRT data for GRB 180510A (Gropp et al. GCN
Circ. 22695
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 ), from 77 s to 40.5 ks after the  BAT trigger. The data
comprise 228 s in Windowed Timing (WT) mode (the first 9 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The refined XRT position is RA, Dec = 276.3314, -31.9081 which is
equivalent to:

RA (J2000): 18 25 19.54
Dec(J2000): -31 54 29.1

with an uncertainty of 3.6 arcsec (radius, 90% confidence).

The late-time light curve (from T0+15.8 ks) can be modelled with a
power-law decay with a decay index of alpha=1.2 (+/-0.4).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.94 (+0.08, -0.07). The
best-fitting absorption column is  5.2 (+/-0.5) x 10^21 cm^-2, in
excess of the Galactic value of 2.1 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.01 (+0.30, -0.28)
and a best-fitting absorption column of 3.5 (+1.4, -1.2) x 10^21 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.8 x 10^-11 (5.8 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     3.5 (+1.4, -1.2) x 10^21 cm^-2
Galactic foreground: 2.1 x 10^21 cm^-2
Excess significance: 1.9 sigma
Photon index:	     2.01 (+0.30, -0.28)

If the light curve continues to decay with a power-law decay index of
1.2, the count rate at T+24 hours will be 0.016 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.2 x
10^-13 (9.4 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/00831810.

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

A. A. Breeveld (UCL-MSSL), S. R. Oates (U.Warwick) and J. D. Gropp (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180510A 97 
s after the BAT trigger (Gropp et al., GCN Circ. 22695
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 ).
A source is detected at the edge of the refined XRT position (D���Ai et 
al. GCN Circ. 22707
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 ) but this is consistent with the position of a 
USNO-B1.0 source (at 276.332, -31.908), and it is not clear if we see 
any fading. Preliminary detections and 3-sigma upper limits using the 
UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 
373) for the first finding chart (FC) exposure and subsequent exposures are:

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

white_FC            97          247          147         20.0 �� 0.3
white            28989        29010          21          >19.2
v		 22961        23272         301          >19.4
b                28076        28983         885          20.2 �� 0.2
u                  310          322          12          >17.6
uvw1             15854        16753         886          >20.6
uvw2             22055        22955         886          >20.5

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.26 in the direction of the 
burst (Schlegel et al. 1998).

A. Tsvetkova, S. Golenetskii, R.Aptekar, D. Frederiks,
M. Ulanov, D. Svinkin, A. Lysenko, A. Kozlova and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration GRB 180510A
(Swift detection of a burst: Gropp et al., GCN 22695
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 ;
Ukwatta et al., GCN 22704
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 )
triggered Konus-Wind at T0=69881.488 s UT (19:24:41.488).

The burst light curve shows a single pulse
which starts at ~T0-6.4 s and has a total duration of ~23.5 s.
The emission is seen up to ~1 MeV.

As observed by Konus-Wind, the burst
had a fluence of 1.07(-0.14,+0.21)x10^-5 erg/cm2,
and a 64-ms peak energy flux, measured from T0-0.064 s,
of 3.53(-1.13,+1.18)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 to T0+16.640 s)
is best fit in the 20 keV - 1.5 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with�� alpha = -1.14(-0.31,+0.38),
and Ep = 237(-56,+126) keV (chi2 = 93/60 dof).
Fitting by the GRB (Band) model yields
alpha = -0.62(-0.66,+1.24),
Ep = 150(-54,+131) keV,
and an upper limit on the high energy photon index:
beta < -1.90 (chi2 = 91/59 dof).

The spectrum near the peak count rate
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 1 MeV range
by a power law with exponential cutoff model
with�� alpha = -0.97(-0.30,+0.35),
and Ep = 202(-34,+54) keV (chi2 = 75/50 dof).
Fitting by the GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -2.37 (chi2 = 75/49 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB180510_T69881/

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

T. Horiuchi,  H. Hanayama, M. Honma (IAO, NAOJ),
R. Itoh, K. L. Murata and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME and OISTER collaboration:

We observed the field of GRB 180510A (Gropp et al.,GCN 22695)
with the optical three color (g', Rc and Ic) CCD camera attached
to the Murikabushi 1m telescope of Ishigakijima Astronomical
Observatory.

The observation started on 2018-05-10 19:29:21 UT, (287 seconds after
the burst).
No new or fading source is detected within the Swift-XRT error circle.

We note that there is faint (~20mag) source detected in DSS images within
XRT error circle (at 18:25:19.2, -31:54:22.7) but the source did not
shows temporal variability during observation (~45 min).

we derive the following upper limits using
UCAC-4 catalog for flux calibration.

#T0+[sec]  MID-UT    T-EXP[sec] g'   Rc   Ic
-------------------------------------------------------------------
287 19:55:17 2700.0 >19.4 >20.4 >20.2
-------------------------------------------------------------------
T0+ : Elapsed time after the burst [hour]
T-EXP: Total Exposure time [sec]