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GRB 190311A

GCN Circular 23946

Subject
GRB 190311A: Swift detection of a burst with optical counterpart
Date
2019-03-11T14:43:26Z (6 years ago)
From
Mike Siegel at PSU/Swift MOC <siegel@swift.psu.edu>
E. Troja (NASA/GSFC/UMCP), S. D. Barthelmy (GSFC),
A. D'Ai (INAF-IASFPA), V. D'Elia (SSDC), J. A. Kennea (PSU),
N. J. Klingler (PSU), A. Y. Lien (GSFC/UMBC),
M. J. Moss (George Washington University), K. L. Page (U Leicester)
and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 14:23:33 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 190311A (trigger=892607).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 212.102, +53.519 which is 
   RA(J2000) = 14h 08m 24s
   Dec(J2000) = +53d 31' 10"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty). From the available data, the BAT light curve showed 
a single-peaked structure with duration of at least 10 sec. However, due to 
a data gap from ~T+10 s to ~ T+ 110 s, there might be additional emission
in that time interval. The peak count rate was ~1700 counts/sec (15-350 keV), 
at ~ 0 sec after the trigger. 

The XRT began observing the field at 14:24:54.0 UT, 80.3 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
212.0649, 53.5007 which is equivalent to:
   RA(J2000)  = 14h 08m 15.58s
   Dec(J2000) = +53d 30' 02.7"
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This
location is 103 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 in excess of the Galactic value (1.17 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 5.1
(+3.27/-2.92) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 5.45e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 85 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	14:08:15.65 = 212.06522
  DEC(J2000) = +53:30:03.0  =  53.50084
with a 90%-confidence error radius of about 0.60 arc sec. This position is 0.85
arc sec. from the center of the XRT error circle. The estimated magnitude is
19.47 with a 1-sigma error of about  0.12. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.01. 

Burst Advocate for this burst is E. Troja (eleonora.troja AT nasa.gov). 
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/)

GCN Circular 23947

Subject
GRB 190311A: Mondy optical observations
Date
2019-03-11T15:49:37Z (6 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
A. Pozanenko (IKI), E. Mazaeva (IKI),  E. Klunko (ISTP), A. Volnova 
(IKI), S. Belkin (IKI)  report   on behalf of IKI-GRB-FuN:

We observed the field of  GRB 190311A  (Troja et al.  GCN 23946) with 
AZT-33IK telescope of Sayan observatory (Mondy) starting on Mar. 11 (UT) 
  14:39:17.   We  clearly  detected  the candidate in optical afterglow 
(Troja et al.  GCN 23946). Coordinates of the optical transient are 
(J2000) 14:08:15.74 +53:30:03.1 with uncertainty of 0.5 arcsec in both 
coordinates, which correspond to the coordinates obtained in GCN 23946. 
  Preliminary photometry of the afterglow in R-filter is following.

t-T0_mid(d) t-T0_mid(min) R_mag err
0.01111 16.0 19.22 0.11
0.01146 16.5 19.25 0.10
0.01180 17.0 19.50 0.11
0.01215 17.5 19.23 0.10
0.01250 18.0 19.47 0.12
0.01285 18.5 19.46 0.10
0.01348 19.4 19.50 0.08
0.01417 20.4 19.62 0.08
0.01487 21.4 19.55 0.09
0.01556 22.4 19.58 0.08
0.01626 23.4 19.56 0.09
0.01695 24.4 19.62 0.09
0.01765 25.4 19.79 0.10
0.01875 27.0 19.83 0.06
0.02014 29.0 19.83 0.06

Photometry is based on the SDSS-DR12 stars (Lupton transformations)
SDSS-DR12_id	        R
J140819.68+532900.1	17.09
J140818.11+532934.7	15.19
J140809.64+533055.9	16.97
J140807.35+533116.9	16.11

The optical transient is fading and we can confirm the optical afterglow 
of  GRB 190311A.

GCN Circular 23948

Subject
GRB 190311A: NEXT-0.6m optical afterglow detection
Date
2019-03-11T15:50:36Z (6 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
Z.P. Zhu, D. Xu, B.Y. Yu (NAOC) report on behalf of larger collaboration:

We observed the field of GRB 190311A (Troja et al., GCN 23946) using the 
robotic NEXT-0.6m telescope located at Nanshan, Xinjiang, China. 
Observations started at 14:25:14 UT on 2019-03-11, i.e., 101 sec after 
the BAT trigger. A series of 40 s, 60 s , 90 s, 300 s R-band frames were 
obtained, and photometry is still ongoing.

An uncatalogued optical source is detected at coordinates

R.A. (J2000) = 14:08:15.71
Dec. (J2000) = +53:30:01.7

with an uncertainty radius ~0.3 arcsec, being consistent with Swift/UVOT 
position  (Troja et al., GCN 23946). The source has m(R) ~ 19.7 mag at 
413 s post-burst, and is fading. We conclude that the source is the 
optical afterglow of the burst.

GCN Circular 23949

Subject
GRB190311A: MASTER Global Robotic Net OT optical observation
Date
2019-03-11T16:18:57Z (6 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
E. Gorbovskoy, V. Lipunov, E. Gorbovskoy, N.Tyurina, V.Kornilov, 
D.Vlasenko, V.Vladimirov,  D.Zimnukhov,
A.Kuznetsov, P.Balanutsa, A. Chasovnikov, D.Kuvshinov (Lomonosov Moscow State 
University, SAI, Physics Department),

O. Gress, N.M. Budnev, O.Ershova, Yu.Ishmuhametova (Applied Physics Institute, 
Irkutsk State University),

V. Yurkov, A. Gabovich, Yu. Sergienko, D. Kobcev (Blagoveschensk Educational 
State University),

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres (The Instituto 
de Astrofisica de Canarias),

D. Buckley (South African Astronomical Observatory),

A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov (Kislovodsk Solar Station 
of the Pulkovo Observatory),

R. Podesta, C. Lopez, C.Francile, F. Podesta (Observatorio Astronomico Felix 
Aguilar OAFA),

H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE)

MASTER-Tunka robotic telescope (Global MASTER-Net: 
http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, 
vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk 
State University) was pointed to the  GRB190311.6 (Troja et al., 
23946) 55 sec after notice time 
and 66 sec after trigger time at 2019-03-11 14:24:45 UT. On our third (30 
s  exposure)  set we  found optical transient  within SWIFT 
error-box at Swift UVOT position (Troja et al., 23946).

m ~ 17.5
RA, DEC = 14:08:15.72, +53:30:02.9
err = 1 arcsec

We obtain a following images with OT:

Tmid-T0  |          Site       |Filt.| Expt. | Limit | Comment
_________|_____________________|_____|_______|_______|________

      109 |        MASTER-Tunka |  P- |    10 | 16.82 |
      109 |        MASTER-Tunka |  P- |    80 | 18.47 |  Coadd
      109 |        MASTER-Tunka |  P| |    10 | 16.69 |
      109 |        MASTER-Tunka |  P| |    80 | 18.33 |  Coadd
      231 |        MASTER-Tunka |  P| |    30 | 17.60 |
      231 |        MASTER-Tunka |  P- |    30 | 17.74 |
      338 |        MASTER-Tunka |  P| |    40 | 17.70 |
      338 |        MASTER-Tunka |  P- |    40 | 17.87 |
      462 |         MASTER-Amur |  P/ |    60 | 13.12 |
      465 |        MASTER-Tunka |  P| |    60 | 18.12 |
      465 |        MASTER-Tunka |  P| |   250 | 19.14 |  Coadd
      465 |        MASTER-Tunka |  P- |    60 | 18.21 |
      465 |        MASTER-Tunka |  P- |   250 | 19.24 |  Coadd
      593 |         MASTER-Amur |  P/ |    60 | 12.20 |
      614 |        MASTER-Tunka |  P| |    80 | 18.50 |
      614 |        MASTER-Tunka |  P- |    80 | 18.43 |
      808 |        MASTER-Tunka |  P| |   110 | 18.65 |
      808 |        MASTER-Tunka |  P- |   110 | 18.65 |
     1032 |        MASTER-Tunka |  P| |   140 | 18.56 |
     1032 |        MASTER-Tunka |  P| |   490 | 19.35 |  Coadd
     1032 |        MASTER-Tunka |  P- |   140 | 18.55 |
     1032 |        MASTER-Tunka |  P- |   490 | 19.30 |  Coadd
     1305 |        MASTER-Tunka |  P| |   170 | 18.64 |
     1305 |        MASTER-Tunka |  P- |   170 | 18.63 |
     1622 |        MASTER-Tunka |  P| |   180 | 19.02 |
     1623 |        MASTER-Tunka |  P- |   180 | 18.89 |
     1949 |        MASTER-Tunka |  P| |   180 | 17.67 |
     1949 |        MASTER-Tunka |  P| |   540 | 19.26 |  Coadd
     1949 |        MASTER-Tunka |  P- |   180 | 17.63 |
     1949 |        MASTER-Tunka |  P- |   540 | 19.22 |  Coadd
     2284 |        MASTER-Tunka |  P| |   180 | 18.90 |
     2284 |        MASTER-Tunka |  P- |   180 | 18.98 |
     2616 |        MASTER-Tunka |  P| |   180 | 19.01 |
     2949 |        MASTER-Tunka |  P| |   180 | 19.10 |
     2949 |        MASTER-Tunka |  P| |   540 | 19.83 |  Coadd
     2949 |        MASTER-Tunka |  P- |   540 | 19.72 |  Coadd
     3959 |        MASTER-Tunka |  P- |   540 | 19.60 |  Coadd
     3959 |        MASTER-Tunka |  P| |   540 | 19.87 |  Coadd
     5650 |        MASTER-Tunka |  P| |   180 | 19.20 |
     5650 |        MASTER-Tunka |  P- |   180 | 18.89 |
     5979 |        MASTER-Tunka |  P- |   180 | 18.74 |
     5979 |        MASTER-Tunka |  P| |   180 | 19.02 |
     6312 |        MASTER-Tunka |  P| |   180 | 18.66 |
     6312 |        MASTER-Tunka |  P- |   180 | 18.79 |


The 5-sigma upper limit has been about 16.32mag
The message may be cited.


====================================================================


The galactic latitude b = 60 deg., longitude l = 99 deg.
The observations made on zenit distance = 48 deg.The moon (22 % bright 
part) is 14 deg. above the horizon. The distance between  moon and  object 
is 113
The sun  altitude  is -30.2 deg.
The object can be observed till sunrise at 2019-03-12 23:26:58.


This message can be cited.

GCN Circular 23950

Subject
GRB 190311A: Enhanced Swift-XRT position
Date
2019-03-11T16:37:34Z (6 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1682 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 190311A, 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 = 212.06539, +53.50037 which is equivalent
to:

RA (J2000): 14h 08m 15.69s
Dec (J2000): +53d 30' 01.3"

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.

GCN Circular 23951

Subject
GRB 190311A: TSHAO optical observations
Date
2019-03-11T20:28:35Z (6 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI), I. Reva (FAPHI), A. Pozanenko (IKI), E. Mazaeva (IKI), 
A. Volnova (IKI), A. Kusakin (FAPHI), M. Krugov (FAPHI)  report   on 
behalf of IKI-GRB-FuN:

We observed the afterglow of GRB 190311A (Troja et al.  GCN 23946) with 
Zeiss-1000 1-m telescope of Tien Shan Astronomical Observatory starting 
on Mar. 11 (UT) 15:54:08.   Preliminary photometry of the afterglow 
detected previously (Troja et al.  GCN 23946; Pozanenko et al.  GCN 
23947; Zhu et al.  GCN 23948; Gorbovskoy et al.  GCN 23949) is following.

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

2019-03-11 15:54:08 0.07228  R      3240 20.87 0.24  21.4

The photometry is based the stars used for calibration in GCN 23947.

GCN Circular 23952

Subject
GRB 190311A: Swift-XRT refined Analysis
Date
2019-03-12T01:18:35Z (6 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
A. Tohuvavohu (PSU), S. J. LaPorte (PSU), K.L. Page (U. Leicester),
A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), V. D'Elia
(ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), J.A. Kennea
(PSU) and E. Troja report on behalf of the Swift-XRT team:

We have analysed 7.6 ks of XRT data for GRB 190311A (Troja et al. GCN
Circ. 23946), from 86 s to 19.1 ks after the  BAT trigger. The data
comprise 80 s in Windowed Timing (WT) mode with the remainder in Photon
Counting (PC) mode. The enhanced XRT position for this burst was given
by Goad et al. (GCN Circ. 23950).

The light curve can be modelled with an initial power-law decay with an
index of alpha=2.27 (+0.38, -0.19), followed by a break at T+386 s to
an alpha of 0.56 (+0.12, -0.08).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.79 (+0.25, -0.24). The
best-fitting absorption column is  2.1 (+1.2, -1.1) x 10^21 cm^-2, in
excess of the Galactic value of 1.2 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.04 (+0.19, -0.18)
and a best-fitting absorption column of 3.8 (+0.9, -0.8) 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 (5.9 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     3.8 (+0.9, -0.8) x 10^21 cm^-2
Galactic foreground: 1.2 x 10^20 cm^-2
Excess significance: 7.3 sigma
Photon index:	     2.04 (+0.19, -0.18)

If the light curve continues to decay with a power-law decay index of
0.56, the count rate at T+24 hours will be 0.022 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.2 x
10^-13 (1.3 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/00892607.

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

GCN Circular 23953

Subject
GRB 190311A: Fermi GBM observation
Date
2019-03-12T02:09:13Z (6 years ago)
From
Peter Veres at UAH <veresp@gmail.com>
P. Veres and C. Meegan (both UAH)
report on behalf of the Fermi GBM Team:

"At 14:23:37.601 UT on 11 March 2019, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 190311A (trigger 574007022 / 190311600),
which was also detected by the Swift/BAT
(Troja et al., GCN 23946). The GBM on-ground location is consistent with
the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 128
degrees.

The GBM light curve consists of a single peak
with a duration (T90) of about 12.5 s (50-300 keV).
The time-averaged spectrum from T0-4.1 s to T0+3.1 s is
adequately fit by a simple power law function with index 1.86 +/- 0.08.

The event fluence (10-1000 keV) in this time interval is
(1.40 +/- 0.18)E-6 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-2.75 s in the 10-1000 keV band
is 3.00 +/- 0.35 ph/s/cm^2.

A power law function with an exponential
high-energy cutoff fits the spectrum equally well
with Epeak= 89 +/- 34 keV and alpha = -1.51 +/- 0.25.


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

GCN Circular 23954

Subject
GRB 190311A: GMG observation
Date
2019-03-12T05:10:29Z (6 years ago)
From
Jirong Mao at Yunnan Obs <jirongmao_obs@ynao.ac.cn>
J. Mao, X.-L. Zhang, and J.-M. Bai (YNAO) report: 


We observed the field of GRB 190311A (Troja et al. GCN Circ. 23946) with the 2.4-meter optical telescope at Gao-Mei-Gu (GMG) station of Yunnan Observatories. The observation began at UT 16:15:07, 11, March, 2019, about 2 hours after the trigger. We clearly detected the afterglow (Pozanenko et al. GCN Circ. 23947; Zhu et al. GCN Circ 23948; Belkin et al. GCN Circ. 23951) , and the preliminary magnitude is measured to be R~20.6.

GCN Circular 23958

Subject
GRB 190311A: Mondy optical observations
Date
2019-03-12T14:34:41Z (6 years ago)
From
Elena Mazaeva at IKI, Moscow <30.v@mail.ru>
E. Mazaeva (IKI), E. Klunko (ISTP), A. Pozanenko (IKI), S. Belkin (IKI), A. Volnova (IKI) report on behalf of IKI-GRB-FuN:

We continue to observe optical afterglow of GRB 190311A (Troja et al. GCN 23946; Pozanenko et al. GCN 23947; Zhu et al. GCN 23948; Gorbovskoy et al. GCN 23949; Belkin et al. GCN 23951; Mao et al. GCN 23954) with AZT-33IK telescope of Sayan observatory (Mondy) starting on Mar. 11 (UT) 15:11:33 (31 minutes after GRB trigger).

Light curve of the afterglow in R-filter (of the full set of the observations incl. reported earlier in GCNs 23947, 23951) can be found at:
http://grb.rssi.ru/GRB190311A/GRB190311A_LC.png

Photometry is based on the SDSS-DR12 stars (Lupton transformations)
SDSS-DR12_id R
J140819.68 +532900.1 17.09
J140818.11 +532934.7 15.19
J140809.64 +533055.9 16.97

GCN Circular 23959

Subject
GRB190311A: OAO observations
Date
2019-03-12T15:13:24Z (6 years ago)
From
Alberto Fernandez-Soto at IFCA (CSIC/UC,Santander) <fsoto@ifca.unican.es>
V. Peris (OAUV-Valencia) and A. Fernandez-Soto (IFCA-Santander) report:

We have observed the field of GRB190311A (Troja et al., GCN 23946) with
the OAUV-0.5m telescope at the Observatorio de Aras de los Olmos (OAO)
in Aras de los Olmos (Valencia, Spain). Observations began after local
midnight on March 12 (UT 01:03, (t-t0) ~ 10.7 hours ~ 0.444 days).

We took 23 ten-minute exposures using a Johnson R filter, out of which 
15 have been selected based on best quality. The afterglow reported in 
GCN23946 and confirmed by Pozanenko et al. (GCN 23947) is
clearly detected in our combined image, with the following magnitude 
and timestamp:

UT(middle)    (t-t0)  Exposure    R    Error
----------   -------  --------  -----  -----
  03:41:46   0.4443d  15x10min  21.45   0.15

The image has been calibrated using 100 stars in the field, the
APASS catalog (r and i mags) and the conversion equations in Lupton 
(2005) as given in the SDSS pages. The calibration zeropoint error is
not significant in comparison with the flux uncertainty (Delta(ZP)~0.03).

Our results confirm the fading of the afterglow and extend the time 
baseline from previous observations. We cannot at the present stage
measure the fading rate within our observations.

OAO is operated by the Observatori Astronomic de la Universitat de
Valencia (OAUV).

GCN Circular 23961

Subject
GRB 190311A: Swift-BAT refined analysis
Date
2019-03-12T16:23:39Z (6 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
J. R. Cummings (CPI), S. D. Barthelmy (GSFC),
H. A. Krimm (NSF/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-60 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 190311A (trigger #892607)
(Troja et al., GCN Circ. 23946).  The BAT ground-calculated position is
RA, Dec = 212.067, 53.486 deg which is
  RA(J2000)  =  14h 08m 16.1s
  Dec(J2000) = +53d 29' 09.2"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 79%.

The mask-weighted light curve shows a single-pulse structure that starts
at ~T-2 s, peaks at ~T+1 s, and ends at ~T+20 s. T90 (15-350 keV) is
17.0 +- 6.8 sec (estimated error including systematics).

The time-averaged spectrum from T-2.22 to T+20.78 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.80 +- 0.17.  The fluence in the 15-150 keV band is 9.1 +- 0.9 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.78 sec in the 15-150 keV band
is 1.8 +- 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/892607/BA/

GCN Circular 23962

Subject
GRB 190311A: NOT optical counterpart
Date
2019-03-12T21:47:13Z (6 years ago)
From
Jonatan Selsing at DARK/NBI <jselsing@dark-cosmology.dk>
J. Selsing (DAWN/NBI), Z.P. Zhu (NAOC), D. Xu (NAOC), D. Malesani��
(DAWN/NBI, DARK/NBI), D. Nespral (IAC), D. Gandolfi (Univ. Turin), and��
J. Telting (NOT), report on behalf of a larger collaboration:

We have observed the optical afterglow of GRB 190311A (Troja et al.,��
GCN 23946; Goad et al., GCN 23950; Veres & Meegan, GCN 23953) with the��
2.5-m Nordic Optical Telescope (NOT). We have obtained an r+z imaging��
sequence using the ALFOSC instrument, with 4x300 and 5x300 s exposure in��
the r and z band, respectively. Imaging observations began 9.4 hr after��
the BAT trigger.

In the images we clearly detect the optical counterpart of GRB 190311A,��
as previously reported (Zhu et al., GCN 23948; Pozanenko et al., GCN��
23947; Gorbovskoy et al., GCN 23949; Belkin et al., GCN 23951; Mao et��
al., GCN 23954; Peris & Fernandez-Soto, GCN 23959).

We calibrate the photometric zeropoints against the Pan-STARRS catalog
and derive the following magnitudes for the optical counterpart:

r = 21.88 +- 0.03 AB mag
z = 21.26 +- 0.04 AB mag

The source is centred at the position:

RA (J2000.0) = 14:08:15.726
DEC (J2000.0) = +53:30:02.74

with the astrometric solution calibrated against the 2MASS catalog.

GCN Circular 23963

Subject
GRB 190311A: Liverpool Telescope observations
Date
2019-03-13T09:20:05Z (6 years ago)
From
Martin Blazek at HETH/IAA-CSIC <alf@iaa.es>
M. Blazek, L. Izzo. D. A. Kann (all HETH/IAA-CSIC), A. de Ugarte-Postigo (HETH/IAA-CSIC, DARK/NBI) and C. C. Thoene (HETH/IAA-CSIC) report:

We observed the Swift GRB 190311A (Troja et al, GCN 23946) with the 2-m Liverpool Telescope located in La Palma, Spain. The observation started 
at 02:19:56 UT on March 12, 2019 (t-t0 =  11.94 hours). We obtained 5x60 seconds exposures each in g', r', and i'. We clearly detected the 
optical afterglow inside the Swift-XRT error circle given of Goad et al. (GCN 23950). We measure the following magnitudes

g' = 22.18 +- 0.24 mag,
r' = 21.70 +- 0.13 mag,
i' = 21.54 +- 0.18 mag.

Magnitudes were derived against 9 nearby stars from the SDSS catalogue and are in the AB system.

GCN Circular 23964

Subject
GRB 190311A: Mondy optical observations
Date
2019-03-13T15:51:30Z (6 years ago)
From
Elena Mazaeva at IKI, Moscow <30.v@mail.ru>
E. Mazaeva (IKI), E. Klunko (ISTP), A. Pozanenko (IKI), S. Belkin (IKI), A. Volnova (IKI) report on behalf of IKI-GRB-FuN:

We continue observations the afterglow of GRB 190311A��(Troja et al. GCN 23946) with AZT-33IK telescope of Sayan observatory (Mondy) starting on Mar. 12 (UT) 16:23:42. Preliminary photometry of the afterglow detected previously (Troja et al. GCN 23946; Pozanenko et al. GCN 23947; Zhu et al. GCN 23948; Gorbovskoy et al. GCN 23949; Belkin et al. GCN 23951; Mao et al. GCN 23954; Mazaeva et al. GCN 23958; Selsing et al. GCN 23962; Blazek et al. GCN 23963) is following.

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

2019-03-12 16:23:42 1.11471�� R�� 5400 22.16 0.09�� 23.5

The photometry is based on several nearby SDSS-DR12 stars used in GCN 23958.

GCN Circular 23965

Subject
GRB 190311A: Swift/UVOT Detection
Date
2019-03-13T16:33:25Z (6 years ago)
From
Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>
M. H. Siegel (PSU) and E. Troja (NASA/GSFC/UMCP)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 190311A
88 s after the BAT trigger (Troja et al., GCN Circ. 23946).
A source consistent with the XRT position (Goad et al., GCN Circ. 23950)
is detected in the initial UVOT exposures. This source is consistent
with the initial transient reported by UVOT, Mondy (Pozanenko et al., GCN
Circ. 23947), Next (Zhu et al., GCN Circ. 23948), MASTER (Gorbovskoy, GCN
Circ. 23949), TSHAO (Belkin et al., 23951), GMG (Mao et al., GCN Circ. 23954)
and OAO (Peris et al., GCN Circ. 23959). The source faded below detection by the second
orbit.

The preliminary UVOT position is:
    RA  (J2000) =  14:08:15.71 = 212.06546 (deg.)
    Dec (J2000) = +53:30:02.9  =  53.50080 (deg.)
with an estimated uncertainty of 0.49 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               88          238          147         19.59 +/- 0.10
white             5678         7314          393            >21.42
white            51260        58205         2454            >22.45
u                  301          550          246         19.85 +/- 0.20
u                 6704        18770         1081            >21.08
b                 6910        19082          493            >20.89
v                 6089        12525         1164            >20.42
uvw1              6500        28478         1676            >20.98
uvm2              6294        23285         1557            >20.87
uvw2              5884         7521          393            >20.16

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.01 in the direction of the burst
(Schlegel et al. 1998).

GCN Circular 23966

Subject
GRB 190311A: OSN optical afterglow detection
Date
2019-03-13T17:51:06Z (6 years ago)
From
Martin Blazek at HETH/IAA-CSIC <alf@iaa.es>
M. Blazek, D. A. Kann, L. Izzo, C. C. Thoene (all HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), and A. Sota (IAA-CSIC) report:

We observed the Swift GRB 190311A (Troja et al, GCN 23946) with the 1.5-m telescope of the Sierra Nevada Observatory (OSN), Spain. The 
observation started at 22:54:30 on March 11, 2019 (t-t0 = 8.5158 hours). We obtained 9x360 seconds exposures each in V, Rc and Ic band. We 
clearly detect the optical afterglow inside the Swift-XRT error circle given by Goad et al. (GCN 23950). We measure the following AB magnitudes:

V  = 21.94 +- 0.17 mag     (23:31:10 - 1:54:18 UT)
Rc = 21.7  +- 0.09 mag     (23:12:50 - 1:35:58 UT)
Ic = 21.27 +- 0.15 mag     (22:54:30 - 1:16:14 UT)

Magnitudes were derived against 11 nearby stars from the SDSS catalogue, using the transformation equations of Lupton (2005), and transformed 
back into AB mags.

GCN Circular 23968

Subject
GRB190311A: MITSuME Akeno optical observation
Date
2019-03-15T12:11:13Z (6 years ago)
From
Kota Iida at Tokyo Inst. of Tech. <kota0722iida@gmail.com>
K. Iida, R. Itoh, K. L. Murata, Y. Tachibana, S. Harita, K. Morita,
K. Shiraishi, M. Oeda, M. Niwano, R. Adachi, Y. Yatsu,
and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration

We searched for the optical counterpart of GRB 190311A (Troja et
al., GCN
Circular #23946) with the optical three color (g', Rc, and Ic) CCD cameras
attached to the MITSuME 50cm telescope of Akeno Observatory, Yamanashi,
Japan.

The observation started on 14:24:43.64 UT which corresponds to
70 sec after the trigger.
We detected the point source at the position consistent with the
afterglow detected previously (Troja et al. GCN #23946; Pozanenko et
al. GCN #23947; Zhu et al. GCN #23948; Gorbovskoy et al. GCN #23949,
Belkin et al. GCN #23951).
The measured magnitudes are listed as follows.

T0+[sec]    MID-UT      T-EXP[sec]        g'       Rc        Ic
-------------------------------------------------------------------------------------------------------
~70      14:24:46.22          540              18.9+/-0.2
18.6+/-0.2     18.2+/-0.2
-------------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used GSC2.3 catalog for flux calibration.
The magnitudes are expressed in the Vega system.

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