GRB 240419A

M. H. Siegel (PSU), S. Dichiara (PSU), R. Gupta (NASA/GSFC),
J. A. Kennea (PSU), S. Laha (GSFC/UMBC), D. M. Palmer (LANL) and
M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 01:48:01 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 240419A (trigger=1222955).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 94.568, -45.011 which is 
   RA(J2000) = 06h 18m 16s
   Dec(J2000) = -45d 00' 40"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of about 4 sec.  The peak count rate
was ~1500 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 01:49:51.1 UT, 110.1 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 94.53468, -45.00073 which
is equivalent to:
   RA(J2000)  = 06h 18m 08.32s
   Dec(J2000) = -45d 00' 02.6"
with an uncertainty of 3.5 arcseconds (radius, 90% containment). This
location is 92 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. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 6.63
x 10^20 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 113 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. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.069. 

Burst Advocate for this burst is M. H. Siegel (siegel AT swift.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/)

P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:

Using  promptly downlinked XRT event data for GRB 240419A, we find an
enhanced XRT position of the afterglow: RA, Dec: 94.53358, -44.99999
which is equivalent to:
   RA (J2000)  = 06 18 08.06
   Dec (J2000) = -44 59 60.0
with an uncertainty of 1.9 arcseconds (radius, 90% confidence).
Analysis of the promptly available data is online at
http://www.swift.ac.uk/sper/1222955.

Position enhancement is is described by Goad et al. (2007, A&A, 476,
1401) and Evans et al. (2009, MNRAS, 397, 1177).

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

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

Using 977 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 240419A, 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 = 94.53406, -44.99952 which is equivalent
to:

RA (J2000): 06h 18m 8.17s
Dec (J2000): -44d 59' 58.3"

with an uncertainty of 2.2 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.

B. Schneider (MIT), N. Gaspari (Radboud Univ.), N. R. Tanvir (Univ. Leicester), S. Covino (INAF/Brera), D. B. Malesani (DAWN/NBI and Radboud Univ.), L. Izzo (INAF/Napoli and DARK/NBI), A. Saccardi (GEPI/Obs. Paris), report on behalf of the Stargate collaboration.

We observed the field of GRB 240419A (Siegel et al., GCN 36169
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 ) using the ESO VLT UT1 equipped with the FORS2 camera. Observations were commenced automatically in rapid-response mode (RRM). The first image was acquired on April 19.0895 UT, that is, 20.9 min after the GRB, and consisted of a 20 s image in the R filter. At a relatively high airmass of 2.1, the delivered PSF was 1.4".

A source, not present in archival images, is detected within the UVOT-enhanced XRT error circle (Goad et al., GCN 36174
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 ), at coordinates (J2000):

RA = 06:18:08.17
Dec = -44:59:57.3

Using FORS2 zeropoints, we measure for the source a magnitude R = 19.88 +- 0.05 (Vega), in excellent agreement with photometry calibrated against nearby stars from the SkyMapper catalog.

Further observations have been secured and will be reported at a later time. We acknowledge excellent support from the ESO observing staff in Paranal.

B. Schneider (MIT), L. Izzo (INAF-Napoli & DARK/NBI), A. Saccardi (GEPI/Obs. de Paris), D. B. Malesani (DAWN/NBI and Radboud Univ.),  J. T. Palmerio (GEPI, Obs. de Paris), A. de Ugarte Postigo (CNRS, OCA, LAM), V. D'Elia (ASI/SSDC & INAF-OAR), N. Gaspari (Radboud Univ.), P. Schady (Univ. of Bath), S. Covino (INAF/Brera), N. R. Tanvir (Univ. Leicester), A. J. Levan (Radboud Univ.), B. P. Gompertz (Birmingham), report on behalf of the Stargate collaboration:

We observed the optical afterglow of GRB 240419A (Siegel et al., GCN 36169
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 ; Schneider et al., GCN 36175
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 ) using the ESO VLT UT2 (Kueyen) equipped with the UVES high-resolution spectrograph. Observations were automatically performed via the rapid-response mode (RRM) system. The observations consisted of a series of spectra taken on April 19 with the first one starting at 02:15:42 UT (27.7 min after the GRB). The spectra cover a wavelength range from 3700 to 9300 AA and were obtained at a relatively high airmass of 2.4.

In the spectrum of 700 s, we only detect a continuum in the upper chip of the red arm (7770 to 9300 AA). From the detection of multiple absorption features, which we interpret as being due to SII, OI, Si II, Si II*, CII, CII*, Si IV, we infer a common redshift of z = 5.178. We conclude this is the redshift of the burst. This is consistent with the absence of flux in the blue dichroic, which covers the wavelength range from 3300 to 5000 AA, and which is entirely blue-ward of the Lyman break at z = 5.178. We also note the presence of additional absorption features likely due multiple intervening systems.

We acknowledge expert support from the ESO staff in Paranal, in particular Jonathan Smoker and Diego Parraguez.

A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), M. Perri
(SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti
(INAF-OAB), D.N. Burrows (PSU), J. D. Gropp (PSU), S. Dichiara (PSU)
and P.A. Evans report on behalf of the Swift-XRT team:

We have analysed 7.8 ks of XRT data for GRB 240419A, from 117 s to 33.6
ks after the  BAT trigger. The data are entirely in Photon Counting
(PC) mode. 

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=5.3 (+2.7, -0.8). At T+249 s  the decay
flattens to an alpha of -0.2 (+0.7, -0.6) before breaking again at
T+1406 s to a final decay with index alpha=1.20 (+0.32, -0.25).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.30 (+0.30, -0.27). The
best-fitting absorption column is  2.4 (+1.1, -0.9) x 10^21 cm^-2, in
excess of the Galactic value of 6.6 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 3.1 x 10^-11 (5.1 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     2.4 (+1.1, -0.9) x 10^21 cm^-2
Galactic foreground: 6.6 x 10^20 cm^-2
Excess significance: 3.1 sigma
Photon index:	     2.30 (+0.30, -0.27)

If the light curve continues to decay with a power-law decay index of
1.20, the count rate at T+24 hours will be 2.8 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.7 x
10^-14 (1.4 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/01222955.

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

M. Ferro, Y.-D. Hu, P. D’Avanzo, R. Brivio, S. Covino, D. Fugazza (INAF-OAB) on behalf of the REM team, report:

We observed for the field of GRB 240419A (Siegel et al., GCN 36169
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 ) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, K bands, starting on 2024 April 19 at 01:49:38 UT (i.e. 1.6 minutes after the event), and lasting for about 3 hours.
From preliminary photometry we detect the  NIR afterglow at a position consistent with the optical afterglow position (Schneider et al., GCN 36175
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 ), at the following AB magnitude in the H band:

H = 15.7 +- 0.1 (calibrated against 2MASS catalogue)
at a mid time of t-t0 ~ 4 minutes after the GRB trigger.

The afterglow is not detected in our optical observations, at the following AB magnitude limit in the r band:

r > 19.2 (calibrated against SkyMapper catalogue)
at a mid time of t-t0 ~ 6.3 minutes after the GRB trigger.

V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik,  D. Vlasenko,
G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij
(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. Gress, N.M. Budnev, O.Ershova
(Irkutsk State University, API),

L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez
(INAOE, Guillermo Haro Astrophysics Observatory),

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

V. Yurkov, A. Gabovich
(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 240419A ( M. H. Siegel et al., GCN 36169
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 ) errorbox  54337 sec after notice time and 54397 sec after trigger time at 2024-04-19 16:54:39 UT, with upper limit up to  17.8 mag. Observations started at twilight.  The observations began at zenith distance = 25 deg. The sun  altitude  is -9.6 deg. 

The galactic latitude b = -24 deg., longitude l = 253 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2427118

We obtain a following upper limits.  

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

   54488 |         MASTER-SAAO |   C |   180 | 17.8 |        
Filter C is a clear (unfiltred) band. 


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

S. P. R. Shilling (Lancaster U.), S. R. Oates (Lancaster U.), A. A. Breeveld (UCL-MSSL), M. De Pasquale (Univ. of Messina) and M. H. Siegel (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 240419A
113 s after the BAT trigger (Siegel et al., GCN Circ. 36169
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 ).
No optical afterglow consistent with the enhanced XRT position (Goad et al., GCN Circ. 36174
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 ) 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) exposures and subsequent exposures are:

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

white_FC           113          263          147         >20.7
u_FC               271          521          246         >20.0
white              113         1025          334         >21.3
v                  602         1075           58         >18.6
b                  527          721           39         >19.3
u                  271          869          285         >20.1
w1                 652          845           39         >18.2
m2                 627         1099           58         >18.3
w2                 578         1050           58         >18.6

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.070 in the direction of the burst
(Schlegel et al. 1998).

Megan Dubay, Donovan Schlekat, Dylan Dutton, Daniel Reichart, Joshua Haislip, and Vladimir Kouprianov report on behalf of the Skynet Robotic Telescope Network at the University of North Carolina at Chapel Hill.

We observed the field of GRB 240419A with one of Skynet’s 16”-diameter PROMPT telescopes at CTIO. The first detection occurred in the I band approximately 1 hour after the trigger reported by Swift (Siegel et al., GCN 36169
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 ).

We detect the afterglow with coordinates consistent with those reported by VLT (B. Schneider et al., GCN 36175
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 ) and REM (Ferro et al., GCN 36183
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 ).

The coordinates are:	
R.A. (J2000):  06:18:08.18
Dec. (J2000): -44:59:57.60

We report the photometry below.

ExpLen | Filter | Mag   | Mag Error  | MJD (Center)   
------------------------------------------------
45x8   | I      | 19.06 | 0.199      | 60419.119
60x8   | R      | ----- | -----      | 60419.119

We report non-detection in the R-band from the reported time with an upper magnitude limit of 20.39.
 
We note that the large R-I color is consistent with the presence of the Lyman-alpha forest in the R band, given its large redshift (Schneider et al., GCN 36176
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 , Lamb & Reichart 2000).

Our images have been calibrated using stars from the APASS catalog.

S. Chastain (UNM), G. E. Anderson (Curtin University), J. K. Leung (U. Toronto/HUJI), L. Rhodes (U. Oxford), S. D. Ryder (Macquarie), A. Gulati (U. Sydney), A. J. van der Horst (GWU), on behalf of the PanRadio GRB collaboration

The Australia Telescope Compact Array (ATCA) performed rapid follow-up observations of GRB 240419A (Siegel et al., GCN 36169
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 ) at 5.5, 9, and 18 GHz as part of the Long-term ATCA "PanRadio GRB" follow-up programme C3542 (PI. Anderson). ATCA began observing at 2024-04-19 04:00 UT (2.2 hours post-burst) up until 12:30 UT. In our preliminary analysis, we have a marginal detect of 63 +/- 18 microJy/beam at 18 GHz that is coincident with the enhanced XRT position (Goad et al., GCN 36174
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 ). We obtain 3 sigma upper limits of 39 and 42 microJy/beam at 5.5 and 9.0, respectively. Further observations are planned.

We thank the CSIRO Space and Astronomy staff for supporting these observations. We acknowledge the Gomeroi people as the traditional owners of the Observatory site. The Australia Telescope Compact Array is part of the Australia Telescope National Facility
(https://ror.org/05qajvd42) which is funded by the Australian Government for operation as a National Facility managed by CSIRO.

T. Parsotan (GSFC), S. D. Barthelmy (GSFC),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
M. J. Moss (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. H. Siegel (PSU)
(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 240419A (trigger #1222955)
(Siegel, et al., GCN Circ. 36169
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 ).  The BAT ground-calculated position is
RA, Dec = 94.505, -44.964 deg which is
   RA(J2000)  =  06h 18m 01.3s
   Dec(J2000) = -44d 57' 50.2"
with an uncertainty of 3.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 89%.
 
The mask-weighted light curve shows two dim pulses at T0-7 s and T0+0 s,
respectively.
The T90 (15-350 keV) is 3.00 +- 1.41 sec (estimated error including systematics).
 
The time-averaged spectrum from T-0.43 to T+2.57 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.71 +- 0.38.  The fluence in the 15-150 keV band is 8.4 +- 2.1 x 10^-08 erg/cm2.
The 1-sec peak photon flux measured from T+0.57 sec in the 15-150 keV band
is 0.6 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.
 
The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1222955