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GRB 200205B

GCN Circular 26993

Subject
GRB 200205B: Swift detection of a burst with optical counterpart
Date
2020-02-05T19:46:01Z (5 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
P. A. Evans (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU),
N. J. Klingler (PSU), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), M. J. Moss (GWU), K. L. Page (U Leicester)
and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels
Swift Observatory Team:

At 19:21:43 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 200205B (trigger=954519 and 954520).  Swift slewed
to the burst after a short delay. 
The BAT on-board calculated location is 
RA, Dec 107.861, -56.506 which is 
   RA(J2000) = 07h 11m 27s
   Dec(J2000) = -56d 30' 21"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a peak about 20 
seconds long (trigger 954519) followed by a brighter more complex 
peak structure 350 s later (trigger 954520) with a peak countrate
of 3500 counts/s.  Due to the double trigger, the complete
BAT lightcurve is not immediately available. 

The XRT began observing the field at 19:27:26.3 UT, 342.7 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source with an enhanced position: RA, Dec 107.7881,
-56.4875 which is equivalent to:
   RA(J2000)  = 07h 11m 09.14s
   Dec(J2000) = -56d 29' 15.0"
with an uncertainty of 2.8 arcseconds (radius, 90% containment). This
location is 37 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 https://www.swift.ac.uk/sper.  We
cannot determine whether the source is fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 1.04
x 10^21 cm^-2 (Willingale et al. 2013). 

The initial flux in the 2.5 s image was 1.26e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 351 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	07:11:09.15 = 107.78811
  DEC(J2000) = -56:29:15.1  = -56.48753
with a 90%-confidence error radius of about 0.61 arc sec. This position is 0.8
arc sec. from the center of the XRT error circle. The estimated magnitude is
16.43 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.11. 

Burst Advocate for this burst is P. A. Evans (pae9 AT star.le.ac.uk). 
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 26995

Subject
GRB 200205B: LCO Optical Detection
Date
2020-02-05T21:37:40Z (5 years ago)
From
Robert Strausbaugh at U. of the Virgin Islands <robert.strausbaugh@uvi.edu>
R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration:

We observed Swift GRB 200205B (Evans et al., GCN 26993) with the LCO 1-m Sinistro instrument at the South African Astronomical Observatory site on February 5, from 19:38 to 20:00 UT (corresponding to 0.28 to 0.82 hours after the GRB trigger time) with the Bessel R and I filters.

We performed a series of 5x120s exposures in each band. We detect a source that is consistent with the Swift-XRT position (Evans et al., GCN 26993) and other optical detections (Lipunov et al., GCN 26991) and not present in either USNO-B1.0 or 2MASS surveys with the following  magnitudes:

R = 18.56 +/- 0.04

I = 17.15 +/- 0.03

These magnitudes are calibrated against several USNO-B1.0 objects near the GRB location and is not corrected for Galactic Extinction.

R.S. is funded by NSF AST grant #1831682

GCN Circular 26998

Subject
GRB 200205B: VLT/X-shooter redshift
Date
2020-02-06T03:17:38Z (5 years ago)
From
Daniele B Malesani at DTU Space <malesani@space.dtu.dk>
J.-B. Vielfaure (GEPI - Paris Observatory), D. Xu (NAO/CAS), J. Palmerio 
(GEPI - Paris Observatory), D. B. Malesani (DTU Space), L. Izzo 
(DARK/NBI), D. A. Kann (HETH/IAA-CSIC), A. J. Levan (Radboud Univ.), G. 
Pugliese (Univ. Amsterdam), N. R. Tanvir (Univ. Leicester) report on 
behalf of the Stargate collabaration:

We observed the optical afterglow of GRB 200205B (Evans et al., GCN 
26993) using the ESO VLT UT2 (Kueyen) equipped with the X-shooter 
spectrograph. Our spectra cover the wavelength range 3000-25000 AA, and 
consist of 4 exposures by 600 s each. The observation mid time was 2020 
Feb 6.063 UT (6.16 hr after the GRB).

In a 30 s image taken with the acquisition camera on Feb 6.041 UT, we 
detect the optical afterglow, for which we measure a magnitude r = 20.34 
+- 0.03 AB (calibrated against nearby stars from the SkyMapper catalog; 
Wolf et al. 2018, PASA, 35, 010; https:doi.org/10.4225/41/593620ad5b574).

We clearly detect continuum over the wavelength range 3100-24000 AA. 
 From detection of multiple absorption features, which we interpret as 
due to C ii, Si iv, Si ii, C iv, Fe ii, Al ii, Mg ii, we infer a 
redshift z = 1.465.
Emission lines are also detected, which we interpret as due to the [O 
ii] and [O iii] doublets, Hbeta, and Halpha, all at the above quoted 
redshift.

We acknowledge excellent support from the ESO observing staff in 
Paranal, in particular J. Corral-Santana and J. Velasquez.

GCN Circular 26999

Subject
GRB 200205B: Enhanced Swift-XRT position
Date
2020-02-06T03:52:10Z (5 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1822 s of XRT Photon Counting mode data and 5 UVOT
images for GRB 200205B, 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 = 107.78760, -56.48741 which is equivalent
to:

RA (J2000): 07h 11m 9.03s
Dec (J2000): -56d 29' 14.7"

with an uncertainty of 1.6 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 27001

Subject
GRB 200205B: Swift-XRT refined Analysis
Date
2020-02-06T16:39:26Z (5 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
J.P. Osborne (U. Leicester), M. Capalbi (INAF-IASFPA), M. Perri (ASDC),
V. D'Elia (ASDC), J. D. Gropp (PSU), J.A. Kennea (PSU), A. Tohuvavohu
(U. Toronto), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester)
and P.A. Evans report on behalf of the Swift-XRT team:

We have analysed 6.5 ks of XRT data for GRB 200205B (Evans et al. GCN
Circ. 26993), from 332 s to 46.4 ks after the  BAT trigger. The data
comprise 360 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 Beardmore
et al. (GCN Circ. 26999).

The late-time light curve (from T0+5.3 ks) can be modelled with a
power-law decay with a decay index of alpha=0.76 (+0.14, -0.13).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.129 (+0.027, -0.026). The
best-fitting absorption column is  4.9 (+1.2, -1.1) x 10^21 cm^-2, at a
redshift of 1.465, in addition to the Galactic value of 1.0 x 10^21
cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index
of 1.93 (+0.19, -0.13) and a best-fitting absorption column of 1 (+35,
-1) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum  is 3.5 x 10^-11 (4.2 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Galactic foreground: 1.0 x 10^21 cm^-2
Intrinsic column:    1 (+35, -1) x 10^20 cm^-2 at z=1.465
Photon index:	     1.93 (+0.19, -0.13)

If the light curve continues to decay with a power-law decay index of
0.76, the count rate at T+24 hours will be 0.018 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.1 x
10^-13 (7.4 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/00954519.

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

GCN Circular 27004

Subject
GRB 200205B: ESO/NTT near-infrared imaging
Date
2020-02-06T22:22:43Z (5 years ago)
From
Daniele B Malesani at DTU Space <malesani@space.dtu.dk>
D. B. Malesani (DTU Space), D. M. Russell, P. Saikia, M. C. Baglio (NYU 
Abu Dhabi), report:

The optical counterpart of GRB 200205B (Evans et al., GCN 26993; 
Strausbaugh & Cucchiara, GCN 26995; Vielfaure et al., GCN 26998) was 
observed with the ESO New Technology Telescope equipped with the SofI 
imager on two different epochs during the night of 2020 Feb 5-6. 
Observations were carried out under ESO program 0104.D-0945(A) (PI Russell).

The afterglow is well detected in the first epoch in the J and Ks 
filters, and is marginally detected in the second observation. 
Calibrated to the 2MASS survey, we obtain the following magnitudes (Vega):

K = 18.07 +- 0.10�� on Feb 6.164 UT�� (0.356 days after the GRB)
J = 19.43 +- 0.10�� on Feb 6.145 UT�� (0.338 days after the GRB)
J = 20.57 +- 0.33�� on Feb 6.368 UT�� (0.561 days after the GRB)

GCN Circular 27006

Subject
GRB 200205B: Swift/UVOT Detection
Date
2020-02-07T02:46:45Z (5 years ago)
From
Kira Simpson at PSU <kira.simpson1984@gmail.com>
GRB 200205B: Swift/UVOT Detection

K. K. Simpson (PSU) and P. A. Evans (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 200205B
352 s after the BAT trigger (Evans et al., GCN Circ. 26993).
A source consistent with the XRT position
(Evans et al. GCN Circ. 26993)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  07:11:09.15 = 107.78812 (deg.)
    Dec (J2000) = -56:29:15.3  = -56.48759 (deg.)
with an estimated uncertainty of 0.42 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           6386           6586          196          18.92+-0.10
white           383            1042           478          16.81+-0.03
v                  540             733          38             16.88 +/-
0.17
b                  638            833           38             17.74 +/-
0.15
u                  614            808           38             17.25 +/-
0.16
w1                 589           783           38            16.88+-0.20
m2                 564          758           38             17.12 +/- 0.28
w2                 689          1056         46              >17.77

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.11 in the direction of the burst
(Schlegel et al. 1998).

GCN Circular 27012

Subject
GRB 200205B: Swift-BAT refined analysis
Date
2020-02-08T02:03:36Z (5 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), P. A. Evans (U Leicester),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU) (i.e. the Swift-BAT team):

Using the data set from T-239 to T+1361 sec from the recent telemetry
downlink,
we report further analysis of BAT GRB 200205B (trigger #954519 and #954520)
(Evans et al., GCN Circ. 26993). We have combined the data from two
triggers (#954519 and #954520) for the analysis. All the times in this
circular
are relative to the trigger time from #954519.

The BAT ground-calculated position is
RA, Dec = 107.760, -56.488 deg which is
   RA(J2000)  =  07h 11m 02.3s
   Dec(J2000) = -56d 29' 18.1"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 47%.

The mask-weighted light curve shows several pulses that start from
~T+20 s and end at ~T+550 s. The first prominent pulse occurs at ~T+60 s,
followed by another significant structure with several overlapping pulses
from ~T+380 s to ~T+520 s. There is a data gap from T+63 s to T+160 s,
likely due to problems of saving data because of the double triggers.
T90 (15-350 keV) is 458.0 +- 5.4 sec (estimated error including
systematics).

Because of the data gap for part of the first pulse, we performed
the time-averaged spectrum for the interval of the second multi-pulse
structure
from T+387.008 to T+520.396 sec. This interval is best fit by a power law
with
an exponential cutoff. This fit gives a photon index 1.36 +- 0.22,
and Epeak of 65.6 +- 10.8 keV (chi squared 41.92 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 5.4 +- 0.2 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+438 sec in the 15-150 keV band is
2.0 +- 0.2 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.84 +- 0.05 (chi squared 58.00 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/954519/BA/

GCN Circular 27027

Subject
GRB 200205B: Chilescope optical observations
Date
2020-02-09T13:51:47Z (5 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
E. Mazaeva (IKI), A. Pozanenko (IKI), M. Krugov (AFIF),  A. Volnova 
(IKI), S. Belkin (IKI) report on behalf of IKI-FuN follow-up collaboration:

We observed  the Swift GRB 200205B (Evans et al., GCN 26993)  with 
Chilescope RC-1000 started on Feb. 7 (UT) 03:04:55 in r'-filter. We 
marginally detect optical afterglow (Lipunov et al., GCN 26991; Evans et 
al., GCN 26993;   Strausbaugh  et al., GCN 26995; Vielfaure et al., GCN 
26998; Malesani et al., GCN 27004; Simpson et al., GCN 27006).

Preliminary photometry is following.

Date       UT start MJD_mid     Filter Exp.   OT(AB) S/N UL
                     (mid, days)    (s)

2020-02-07 03:04:55 1.33613     r'     2*1200 22.2   2.0 22.0

The photometry is based on nearby stars from the SkyMapper catalog
SkyMapper_id    r
293365688    17.550
293359963    16.213
293359881    15.816
293365677    17.659

GCN Circular 27034

Subject
Konus-Wind observation of GRB 200205B
Date
2020-02-11T13:05:44Z (5 years ago)
From
Anastasia Tsvetkova at Ioffe Institute <tsvetkova@mail.ioffe.ru>
A. Tsvetkova, S. Golenetskii, R.Aptekar, D. Frederiks,
M. Ulanov, D. Svinkin, A. Lysenko, A. Ridnaia and T. Cline
on behalf of the Konus-Wind team, report:

The long GRB 200205B which triggered Swift/BAT
at T0=T0(BAT)=19:21:43 UT
(Swift/BAT detection: Evans et al., GCN 26993;
Ukwatta et al., GCN 27012;)
was detected by Konus-Wind in the waiting mode.

The burst light curve shows two emission episodes:
the first pulse lasts from ~T0+48.6 s to ~T0+89.8 s,
and the second pulse lasts from ~T0+390.1 s to ~T0+525.5 s.
The total duration of the burst is ~477 s.

As observed by Konus-Wind, the burst had a fluence of
1.12(-0.05,0.26)x10^-5 erg/cm2 and a 2.944-s peak flux,
measured from ~T0(BAT)+437.202 s, of 1.55(-0.09,+0.44)x10^-7 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

Fitting the K-W 3-channel spectrum o the initial pulse
(from ~T0(BAT)+48.594 s to ~T0(BAT)+89.810 s)
in the 20 keV - 1.5 MeV range
by a simple power law model yields
the PL index = 2.34(-0.06,+0.17),
chi2 = 2.95 / 1 dof.

Modelling the K-W 3-channel spectrum of the second pulse
(from ~T0(BAT)+390.098 s to ~T0(BAT)+446.034 s)
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) yields
alpha = -1.32(-0.59,+2.70),
and Ep =87(-17,+13) keV.

Assuming the redshift z=1.465 (Vielfaure et al., GCN 26998)
and a standard cosmology model with H_0 = 67.3 km/s/Mpc,
Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~6.5x10^52 erg,
the peak luminosity L_iso is ~2.2x10^51 erg/s,
and the rest-frame peak energy of the initial pulse spectrum,
Ep,z, is ~ 214 keV.

All the quoted errors are estimated at the 1 sigma confidence level.
All the presented results are preliminary.

The K-W light curve of this burst is available at
http://www.ioffe.rssi.ru/LEA/GRBs/GRB200205B/

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