GRB 200409A

Dougal Dobie (USYD/CSIRO), Tara Murphy (USYD), David Kaplan (UWM)

While performing follow-up of GRB 200405B (GCN 27497
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 , 27516
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 ) we received
notification of the detection of GRB 200409A and the associated optical
and X-ray candidate counterpart (GCN 27509
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 ). We added it to our schedule
and carried out observations of it from 2020-04-09 07:00-09:30 UTC,
approximately 5 hours post-burst.

We make no detection of radio emission at 5.5 or 9 GHz with 3-sigma upper
limits of 90 uJy and 81 uJy respectively.

Thank you to CSIRO staff for supporting these observations during these
especially difficult times.

S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
H. A. Krimm (NSF), J.D. Gropp (PSU),
S. Laha (GSFC/UMBC), 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-240 to T+963 sec from the recent telemetry
downlink,
we report further analysis of BAT GRB 200409A (trigger #965484)
(Gropp et al., GCN Circ. 27509
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 ).  The BAT ground-calculated position is
RA, Dec = 60.555, -50.243 deg which is
   RA(J2000)  =  04h 02m 13.3s
   Dec(J2000) = -50d 14' 36.4"
with an uncertainty of 2.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 75%.

The mask-weighted light curve shows several overlapping pulses that start
at ~T0 and ends at~T+19 s. The main peak occurs at ~T0. T90 (15-350 keV)
is 17.91 +- 5.20 sec (estimated error including systematics).

The time-averaged spectrum from T+0.01 to T+19.01 sec is best fit by a
simple
power-law model.  The power law index of the time-averaged spectrum is
2.14 +- 0.44.  The fluence in the 15-150 keV band is 2.3 +- 0.6 x 10^-7
erg/cm2.
The 1-sec peak photon flux measured from T+0.01 sec in the 15-150 keV band
is 1.2 +- 0.2 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/965484/BA/

E. Burns (GSFC), M. S. Briggs (UAH), C. M. Hui (MSFC), C. Malacaria (MSFC),
and P. Veres (UAH) reports on behalf of the Fermi-GBM Team

Swift-BAT detected GRB 200409A at 03:19:59 UT (GCN 27509
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 ). There was no
Fermi-GBM onboard trigger around the event.

An automated, blind search for short gamma-ray bursts below the onboard
triggering threshold in Fermi-GBM identified GRB 200904A with high
reliability [1], with a localization consistent with the Swift-BAT
location, and a discovery timescale of 0.703 s.

The GBM targeted search [2], the most sensitive, coherent search for
GRB-like signals, was run from +/-30 s around BAT trigger time. A transient
source was identified whose most significant timescale according to the
search is 1.024 s, with a log likelihood ratio of 62, with a consistent
location, and is consistent with a soft spectrum for a GRB.

Preliminary spectral analysis statistically prefers a power-law fit over
models that constrain Epeak. Using T0-0.320 to T0+0.320 as the source
interval gives an alpha of -1.84 +/- 0.06, a photon flux of 3.3 +/- 0.4
ph/s/cm^2, and a fluence of (2.0+/-0.2)E-7 erg/s/cm^2.

[1] https://gcn.gsfc.nasa.gov/notices_gbm_sub/608095205.fermi
[2] Goldstein et al. 2019 arXiv:1903.12597
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V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

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

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

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

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

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




MASTER-SAAO robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 200409A ( J.D. Gropp et al., GCN 27509
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 ) errorbox  49717 sec after notice time and 49742 sec after trigger time at 2020-04-09 17:09:01 UT, with upper limit up to  19.1 mag. Observations started at twilight.  The observations began at zenith distance = 44 deg. The sun  altitude  is -10.2 deg. 

The galactic latitude b = -47 deg., longitude l = 259 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1333122

We obtain a following upper limits.  

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

   49832 |         MASTER-SAAO |   C |   180 | 19.1 |        
   49834 |         MASTER-SAAO |   C |   180 | 19.0 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.

D.N. Burrows (PSU), J. D. Gropp (PSU), A.P. Beardmore (U. Leicester),
P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), T. Sbarrato
(INAF-OAB), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), J.A.
Kennea (PSU) and J.D. Gropp report on behalf of the Swift-XRT team:

We have analysed 7.6 ks of XRT data for GRB 200409A (Gropp et al. GCN
Circ. 27509
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 ), from 59 s to 18.1 ks after the  BAT trigger. The data
comprise 7 s in Windowed Timing (WT) mode (taken while Swift was
slewing), with the remainder in Photon Counting (PC) mode. The enhanced
XRT position for this burst was given by Evans et al. (GCN Circ.
27510
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 ).

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=2.8 (+5.2, -0.8). At T+123 s  the decay
flattens to an alpha of -0.2 (+0.4, -0.7) before breaking again at
T+441 s to a final decay with index alpha=0.80 (+0.34, -0.07).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.94 (+0.17, -0.16). The
best-fitting absorption column is  3.2 (+3.7, -1.9) x 10^20 cm^-2,
consistent with the Galactic value of 1.3 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 3.3 x 10^-11 (3.6 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     3.2 (+3.7, -1.9) x 10^20 cm^-2
Galactic foreground: 1.3 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.94 (+0.17, -0.16)

If the light curve continues to decay with a power-law decay index of
0.80, the count rate at T+24 hours will be 9.0 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.0 x
10^-13 (3.2 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/00965484.

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

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

Using 2685 s of XRT Photon Counting mode data and 6 UVOT
images for GRB 200409A, 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 = 60.53633, -50.22498 which is equivalent
to:

RA (J2000): 04h 02m 8.72s
Dec (J2000): -50d 13' 29.9"

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.

J.D. Gropp (PSU), S. D. Barthelmy (GSFC), J. A. Kennea (PSU),
N. J. Klingler (PSU), S. Laha (GSFC/UMBC/CRESST),
A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), M. J. Moss (GWU),
D. M. Palmer (LANL), M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 03:19:59 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 200409A (trigger=965484).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 60.553, -50.247, which is 
   RA(J2000)  =  04h 02m 13s
   Dec(J2000) = -50d 14' 49"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows multiple peaks
with a total duration of about 20 sec.  The peak count rate
was ~2000 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 03:21:13.1 UT, 73.4 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 60.53820, -50.22509 which is equivalent
to:
   RA(J2000)  = 04h 02m 09.17s
   Dec(J2000) = -50d 13' 30.3"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 85 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 in excess of the Galactic value (1.27 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 5
(+4.06/-3.42) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 77 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	04:02:08.75 =  60.53646
  DEC(J2000) = -50:13:28.4  = -50.22455
with a 90%-confidence error radius of about 0.77 arc sec. This position is 4.6
arc sec. from the center of the XRT error circle. The estimated magnitude is
19.14 with a 1-sigma error of about  0.16. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.01. 

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/)