GRB 210509A

K. L. Page (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU),
F. E. Marshall (NASA/GSFC) and D. M. Palmer (LANL) report on behalf of
the Neil Gehrels Swift Observatory Team:

At 14:32:20 UT, the Swift Burst Alert Telescope (BAT) triggered and
located a GRB 210509A (trigger= 1047531).  Swift did not slew immediately
due to an observing constraint. 
The BAT on-board calculated location is 
RA, Dec 350.352, +6.675 which is 
  RA(J2000) = 23h 21m 25s
  Dec(J2000) = +06d 40' 31"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  Due to telemetry limitations, no further
BAT data will be available until the ground-station pass data
has been processed. 

Due to an observing constraint, Swift will not slew until T0+50
minutes. There will be no XRT or UVOT data until this time. 

Burst Advocate for this burst is K. L. Page (klp5 AT leicester.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/)

P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), D.N. Burrows
(PSU), J.A. Kennea (PSU), M. Perri (SSDC & INAF-OAR) and G. Tagliaferri
(INAF-OAB) report on behalf of the Swift-XRT team:

The XRT began observing the field of GRB 210509A at 15:45:53.0 UT,
4412.6 seconds after the BAT trigger. Using promptly downlinked data we
find an uncatalogued X-ray source located at RA, Dec 350.37430, 6.67134
which is equivalent to:
   RA(J2000)  = 23h 21m 29.83s
   Dec(J2000) = +06d 40' 16.8"
with an uncertainty of 4.4 arcseconds (radius, 90% containment). This
location is 80 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 7.11
x 10^20 cm^-2 (Willingale et al. 2013).

T.-R. Sun, Y.-D. Hu, E. Fernandez-Garcia, A. J. Castro-Tirado, M.D. Caballero-Garcia, M. A. Castro Tirado (IAA-CSIC), C. Perez del Pulgar, A. Castellon, I. Carrasco (Univ. de Malaga), S. Guziy (Univ. of Nikolaev) and D. R. Xiong, Y. F. Fan, J. M. Bai, C. J. Wang, Y. X. Xin, X. H. Zhao (Yunnan Observatories of CAS) on behalf of a larger collaboration, report:

Following the detection of GRB 210509A by Swift (Page et al. GCNC 29970), we triggered the 0.6m BOOTES-4/MET robotic telescope at Lijiang Astronomical Observatory (China) starting on May 9 at 19:32 UT (~5 hr after trigger) with non-optimal conditions (passing clouds and the target being at high airmass). No optical source is detected at the position reported by Swift-XRT (Evans et al. GCNC 29971) down to 17.2 mag in the co-added image (clear filter). Additional observations are ongoing.

We thank the staff at Lijiang observatory for their excellent support.

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

Using 1722 s of XRT Photon Counting mode data and 5 UVOT
images for GRB 210509A, 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 = 350.37564, +6.67126 which is equivalent
to:

RA (J2000): 23h 21m 30.15s
Dec (J2000): +06d 40' 16.5"

with an uncertainty of 2.5 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.

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),

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 210509A ( K. L. Page et al., GCN 29970
Loading...
 
 ) errorbox  41751 sec after notice time and 41820 sec after trigger time at 2021-05-10 02:09:20 UT, with upper limit up to  16.0 mag. The observations began at zenith distance = 77 deg. The sun  altitude  is -39.8 deg. 

The galactic latitude b = -50 deg., longitude l = 88 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1610042

We obtain a following upper limits.  

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

   41910 |         MASTER-SAAO |   C |   180 | 16.0 |        
Filter C is a clear (unfiltred) band. 


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

A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), C. B. Markwardt (GSFC),
K. L. Page (U Leicester), 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 210509A (trigger #1047531)
(Page et al., GCN Circ. 29970
Loading...
 
 ).  The BAT ground-calculated position is
RA, Dec = 350.363, 6.650 deg which is
   RA(J2000)  =  23h 21m 27.2s
   Dec(J2000) = +06d 39' 01.1"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 95%.

The mask-weighted light curve shows several overlapping pulses that
start at ~T-2 s and end at ~T+8 s. The burst went out of the BAT FOV
at ~T+77 s. T90 (15-350 keV) is 8.22 +- 0.75 sec (estimated error
including systematics).

The time-averaged spectrum from T-1.65 to T+7.63 sec is best fit by
a power law with an exponential cutoff.  This fit gives a photon
index 0.76 +- 1.00, and Epeak of 33.0 +- 8.3 keV (chi squared 70.16
for 56 d.o.f.).  For this model the total fluence in the 15-150 keV band
is 3.1 +- 0.4 x 10^-7 erg/cm2 and the 1-sec peak flux measured from
T+3.24 sec in the 15-150 keV band is 1.2 +- 0.2 ph/cm2/sec.  A fit to
a simple power law gives a photon index of 2.18 +- 0.17 (chi squared
78.23 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/1047531/BA/

J.A. Kennea (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U.
Leicester), J.P. Osborne (U. Leicester), P. D'Avanzo (INAF-OAB), M.G.
Bernardini (INAF-OAB), E. Ambrosi  (INAF-IASFPA) , A. Tohuvavohu (U.
Toronto), B. Sbarufatti (PSU) and K.L. Page report on behalf of the
Swift-XRT team:

We have analysed 7.2 ks of XRT data for GRB 210509A (Page et al. GCN
Circ. 29970
Loading...
 
 ), from 3.2 ks to 56.6 ks after the	BAT trigger. The data
are entirely in Photon Counting (PC) mode. The enhanced XRT position
for this burst was given by Goad et al. (GCN Circ. 29973
Loading...
 
 ).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.11 (+0.20, -0.17).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.63 (+0.36, -0.16). The
best-fitting absorption column is  consistent with the Galactic value
of 7.1 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 4.0 x 10^-11 (4.4 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     7.1 (+/-8.9) x 10^20 cm^-2
Galactic foreground: 7.1 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.63 (+0.36, -0.16)

If the light curve continues to decay with a power-law decay index of
1.11, the count rate at T+24 hours will be 2.2 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.7 x
10^-14 (9.6 x 10^-14) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01047531.

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

N. P. M. Kuin (UCL-MSSL) and K. L. Page (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210509A
3202 s after the BAT trigger (Page et al., GCN Circ. 29970
Loading...
 
 ).
No optical afterglow consistent with the XRT position (Evans et al.
GCN Circ. 29971
Loading...
 
 ) is detected in the initial UVOT exposures.
Preliminary 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          3202         3352          147         >20.8
white             3202         4585          344         >21.0
v                 3358         4934          332         >19.0
b                 4180         4380          197         >19.5
u                 3974         4174          197         >19.6
w1                3769         3969          197         >19.5
m2                3563         3763          197         >20.3
w2                4592         4792          197         >19.6

The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.074 in the direction of
the burst (Schlegel et al. 1998).

Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H.
Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska
(UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora Troja (GSFC), Owen
Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jes��s Gonz��lez (UNAM), Carlos
Rom��n-Z����iga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou
(U. Wash.), and Vicki Toy (UMD) report:

We observed the field of GRB 210509A (Page et al., GCN Circ. 29970
Loading...
 
 ) with the
Reionization and Transients Infrared Camera (RATIR) on the 1.5m Harold Johnson
Telescope at the Observatorio Astron��mico Nacional on Sierra San Pedro M��rtir
from 2021/05 10.47 to 2021/05 10.48 UTC (19.34 to 19.70 hours after the BAT
trigger), obtaining a total of 0.21 hours exposure in the r and i bands and 0.08
hours exposure in the Z, Y, J, and H bands.

For a source within the Swift-XRT error circle, in comparison with the SDSS DR9
and 2MASS catalogs, we obtain the following upper limits (3-sigma):

  r	> 21.28
  i	> 21.09
  Z	> 18.17
  Y	> 19.19
  J	> 19.57
  H	> 17.30

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.