GRB 210704A
GCN Circular 30465
Subject
GRB 210704A: Zeiss-1000/SAO-RAS optical observations
Date
2021-07-17T14:02:10Z (5 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
A. Volnova (IKI), A. Moskvitin (SAO RAS), A. Pozanenko (IKI), N. Pankov
(IKI, HSE), S. Belkin (IKI, HSE) report on behalf of GRB IKI FuN:
We observed GRB 210704A (Ursi et al., GCN 30372; Berretta et al., GCN
30375; Prasad et al., GCN 30378; D'Ai et al., GCN 30379; Malacaria et
al., GCN 30380; Ridnaia et al., GCN 30388) with Zeiss-1000 telescope of
SAO RAS observatory on 2021-07-11 and 2021-07-13. We marginally
detect the optical afterglow (Kim et al., GCN 30384; D'Avanzo et al.,
GCN 30385; Troja et al., GCN 30390; Kann et al., GCN 30391, 30401; Sun
et al., GCN 30411; D'Avanzo et al., GCN 30432; Rastinejad et al., GCN
30433; Watson et al., GCN 30436; Pankov et al., GCN 30440; Troja et
al., GCN 30442; Kann et al., GCN 30443; Fong et al., GCN 30445; O'Connor
et al., GCN 30451).
Preliminary photometry of the afterglow is following
Date UT start t-T0 Filter Exp. OT err UL(3 sigma)
(mid, days) (s)
2021-07-11 18:38:22 6.98262 R 12*300 23.1 0.3 23.2
2021-07-13 18:16:08 8.94635 R 24*300 23.8 S/N=2 23.5
The photometry is based on nearby USNO_B-1.0 stars
USNO_B-1.0_id R2
1471-0248922 16.31
1471-0248878 17.04
GCN Circular 30452
Subject
GRB 210704A: classification as long GRB and redshift estimating
Date
2021-07-12T13:07:08Z (5 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
P. Minaev (IKI), A. Pozanenko (IKI), I. Chelovekov (IKI), S. Grebenev
(IKI) report on behalf of GRB IKI FuN:
We analyzed GRB 210704A (Ursi et al., GCN 30372; Berretta et al., GCN
30375; Prasad et al., GCN 30378; D'Ai et al., GCN 30379; Malacaria
etal., GCN 30380; Ridnaia et al., GCN 30388) using publicly available
data of GBM/Fermi. The burst consists of several episodes of emission
with duration of T_90 = 4.6 s, but the emission is visible up to 20 s
after the trigger. Energy spectrum constructed in the time interval of
(-0.2, 6.5) seconds relative to the GBM trigger time is best described
by Bandmodel with relatively low E_peak = 294 keV corroborating with
E_peak reported by GBM team (Malacaria et al., GCN 30380) and Konus-Wind
(Ridnaia et al., GCN 30388).
Based on E_peak, Fluence in 1 keV ��� 10 MeV range (2.77e-5 erg cm^-2) and
T_90 we draw a trajectory of the burst in EH - T_90 diagram varying the
unknown source redshift
(http://grb.rssi.ru/GRB210704A/GRB210704A_EH-T90_GBM.png , see [1-2] for
details). The lower 2 sigma redshift limit of the source is z=0.11,
which excludes the association of the GRB with the field galaxy at z =
0.0817, but leaves a possibility of association with the field cluster
at z = 0.203 (de Ugarte Postigo et al., GCN 30392). We also estimate
E_iso = 8.2e50 erg at z = 0.11 and E_iso = 3.7e53 erg at z = 2.34
(marginally suggested after GTC spectroscopy, de Ugarte Postigo et al.,
GCN 30392).
Based only on the trajectory at the EH - T_90 diagram we could suggest
the collapsar origin (Type II) of GRB 210704A.
[1] - Minaev et al., MNRAS, 492, 1919, 2020
[2] - Minaev et al., Astronomy Letters, 46, 9, 573, 2020
GCN Circular 30451
Subject
GRB 210704A: Lowell Discovery Telescope Optical Observations
Date
2021-07-12T13:02:36Z (5 years ago)
From
Brendan O'Connor at UMD <oconnorb@umd.edu>
B. O'Connor (GWU, UMD), E. Troja (UMD, NASA-GSFC), E. Zack (UMD),
S.Dichiara (UMD, NASA-GSFC), P. Gatkine (Caltech), J.M. Durbak (UMD),
S.B. Cenko (NASA-GSFC), A. Kutyrev (UMD, NASA-GSFC), S. Veilleux (UMD)
report:
We observed the field of GRB 210704A (Ursi et al., GCN 30372;
Berretta et al., GCN 30375; Prasad et al., GCN 30378; D'Ai et al.,
GCN 30379; Malacaria et al., GCN 30380; Ridnaia et al., GCN 30388)
with the Large Monolithic Imager (LMI) on the 4.3m Lowell Discovery
Telescope (LDT) at Happy Jack, AZ. Observations started on July 11, 2021
at 3:57:51 UT (about 6.4 days after the GRB trigger) in the SDSS r filter.
The observations were taken at airmass 1.8 and seeing 2.0" for 1500 s.
We detect the optical afterglow (Kim et al., GCN 30384)
with magnitude r ~ 23.4 +/- 0.2 AB mag. This indicates a
negligible decay of the transient between 4.1 and 6.4 days
(Watson et al., GCN 30436).
Magnitudes are calibrated against the SDSS catalog and are not
corrected for Galactic extinction.
We thank the staff of the Lowell Discovery Telescope for assistance
with these observations.
GCN Circular 30445
Subject
GRB 210704A: Continued Gemini-North NIR K-band Detections
Date
2021-07-12T02:16:53Z (5 years ago)
From
Wen-fai Fong at Northwestern U <wfong@northwestern.edu>
W. Fong and J. Rastinejad (Northwestern) report on behalf of a larger collaboration:
We continue to observe GRB 210704A (Kunzweiler et al., GCN 30369; Ursi et al., GCN 30372; Berretta et al., GCN 30375; Prasad et al., GCN 30378; D'Ai et al., GCN 30379) with the Near-Infrared Imager (NIRI) mounted on Gemini-North under Program GN-2021A-Q-109. We obtained two additional epochs of K-band imaging on 2021-07-10 and 2021-07-11 UT at mid-times of 5.47 days and 6.45 days for 34x60-sec and 43x60-sec, respectively. The infrared source (Rastinejad et al., GCN 30433) is still detected in both epochs, with a brightness of K_AB = 23.2 +/- 0.2 mag at 6.45 days. Performing digital image subtraction between these epochs and our initial imaging at 4.5 days, we find no clear evidence for any significant changes in brightness.
In addition, the source is clearly point-like in our most recent imaging, indicating that there is not a significant contribution from a host galaxy to the NIR flux at this time (consistent with the same conclusion reached in the optical bands, Watson et al., GCN 30436; Kann et al., GCN 30443). The fairly flat temporal evolution of the NIR source over ~4.5-6.5 days is consistent with the contemporaneous optical behavior (D'Avanzo et al., GCN 30432; Kann et al., GCN 30443), and is also at odds with a pure, fading afterglow origin, as previously noted (Watson et al., GCN 30436; Kann et al., GCN 30443).
We thank the Gemini staff for the rapid scheduling and execution of these observations.
GCN Circular 30444
Subject
GRB 210704A: INTEGRAL observations
Date
2021-07-11T22:27:18Z (5 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
Minaev, P., Pozanenko, A., Chelovekov, I., Grebenev, S. report on
behalf of GRB IKI FuN:
We report results of analysis of INTEGRAL observations of GRB 210704A.
We used publicly available data. GRB 210704A was initially reported by
X-/gamma-ray experiments (Ursi et al., GCN 30372; Berretta et al., GCN
30375; Prasad et al., GCN 30378; D'Ai et al., GCN 30379; Malacaria et
al., GCN 30380; Ridnaia et al., GCN 30388). The burst was detected by
SPI-ACS at (UTC) 2021-07-04T19:33:24.5. Its duration in the SPI-ACS
energy band (> 80 keV) is T_90 = 3.5 +/- 0.7 s. Comparing fluences of
long-duration GRBs simultaneously recorded by SPI-ACS and Fermi/GBM
(Chelovekov et al., in preparation) we estimated the GRB 210704A fluence
to be 1.8e-5 erg/cm^2 in the 10-1000 keV band (the 95% confidence region
which includes systematics was 5.2e-6 ��� 6.3e-5 erg/cm^2). We did not
detect any signature of an extended emission in the SPI-ACS energy band
(> 80 keV). GRB 210704A was also detected by ISGRI detector as 106
degrees off-axis event. The light curve of both SPI-ACS and ISGRI can
be found at
http://grb.rssi.ru/GRB210704A/GRB20210704A_ISGRI_ACS.png
GCN Circular 30443
Subject
GRB 210704A: NOT optical observations and color change
Date
2021-07-11T20:07:25Z (5 years ago)
From
Luca Izzo at DARK/NBI <luca.izzo@gmail.com>
D. A. Kann (HETH/IAA-CSIC), L. Izzo (DARK/NBI), F. J. Galindo Guil, and A. Kasikov (NOT) report:
We observed the optical afterglow (Kim et al., GCN #30384; D'Avanzo et al., GCN #30385; Kann et al., GCN #30391; de Ugarte Postigo et al., GCN #30392; Kann et al., GCN #30401; Sun et al., GCN #30411; D'Avanzo et al., GCN #30432; Rastinejad et al., GCN #30433; Watson et al., GCN #30436; Pankov et al., GCN #30440; Troja et al., GCN #30442) of GRB 210704A (Kunzweiler et al., GCN #30369; Ursi et al., GCN #30372; Berretta et al., GCN #30375; Prasad et al., GCN #30378; D'Ai et al., GCN #30379; Malacaria et al. GCN #30380; Ridnaia et al., GCN #30388) with the AlFOSC imager mounted on the Nordic Optical Telescope (NOT) located in La Palma, Spain.
We have obtained 3x300s images in the g' and r' filters, at a mean epoch of 6.085 days and 6.096 days after the GRB, respectively. The optical afterglow is still detected in each stacked image, and we measure g' = 23.78 +/- 0.11 mag, r' = 23.27 +/- 0.09 mag against Pan-STARRS comparison stars (AB system).
This suggests that the optical transient has hardly changed in brightness for several days compared to earlier measurements (D'Avanzo et al., GCN #30432; Watson et al., GCN #30346), while remaining two magnitudes brighter than the potential host galaxy (Watson et al., GCN #30436).
On the other hand, the g' - r' color has increased compared to the measurement of Kann et al., GCN #30401, a behavior expected both for a SN component and a KN component, but not an afterglow. As the temporal evolution is also peculiar for a fast-evolving KN, the interpretation as a rising SN gains credence (Watson et al., GCN #30436). The magnitude, however, may be indicative of a redshift exceeding those indicated by a nearby galaxy and somewhat more distant galaxy cluster (Levan et al., GCN #30381).
GCN Circular 30442
Subject
GRB210704A: Gemini near-infrared upper limits
Date
2021-07-11T17:24:24Z (5 years ago)
From
Eleonora Troja at NASA/GSFC/UMD <eleonora@umd.edu>
E. Troja (UMD/GSFC), A. Watson (UNAM), B. O'Connor (UMD/GSFC/GWU) report on
behalf of a larger collaboration:
We observed the field of GRB 210704A (Ursi et al., GCN 30372; Berretta et
al., GCN 30375; Malacaria et al. GCN 30380) with the Near-Infrared Imager
(NIRI) mounted on the 8.1m Gemini North telescope. We obtained 24x60 s
imaging in J-band starting on 2021 July 10 at 06:00 UT (~5.5 days after the
GRB) at an average airmass of 2.0.
At the location of the optical afterglow (Kim et al., GCN 30384) we detect
no source. Preliminary calibration against nearby 2MASS objects yields a
3-sigma upper limit of J>23.5 AB mag. With respect to the earlier
observations reported by Rastinejad et al. (GCN 30433), our data show a
marginal evidence of fading.
We note that nearly simultaneous Swift/XRT observations still detect the
X-ray afterglow at a flux level of ~4.4E-14 erg/cm2/s at 4.5 d after the
burst. By using a spectral index of about 0.85, consistent with the
Swift/XRT spectrum (https://www.swift.ac.uk/xrt_spectra/00021454/) and the
observed temporal decay with slope ~1.3, we estimate an
afterglow contribution of ~23.1 AB mag to the nIR emission. This suggests
that the non-thermal afterglow component could have significantly
contributed to the nIR detection reported in Rastinejad et al. (GCN 30433).
We thank the Gemini staff for scheduling and executing these observations.
GCN Circular 30440
Subject
GRB 210704A: Assy optical afterglow upper limit
Date
2021-07-10T23:24:16Z (5 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
N. Pankov (HSE, IKI), S. Belkin (IKI), V. Kim (FAI, Pulkovo
Observatory), A. Pozanenko (IKI), M. Krugov (FAI) report on behalf of
GRB IKI FuN:
We observed GRB 210704A (Ursi et al., GCN 30372; Berretta et al., GCN
30375; Prasad et al., GCN 30378; D'Ai et al., GCN 30379; Malacaria et
al., GCN 30380; Ridnaia et al., GCN 30388) with AZT-20 telescope of
Assy-Turgen observatory starting on 2021-07-08 (UT) 16:59:54. We do not
detect the optical afterglow (Kim et al., GCN 30384; D'Avanzo et al.,
GCN 30385; Troja et al., GCN 30390; Kann et al., GCN 30391, 30401; Sun
et al., GCN 30411; D'Avanzo et al., GCN 30432; Rastinejad et al., GCN
30433; Watson et al., GCN 30436).
Preliminary photometry of the filed is following
Date UT start t-T0 Exp. Filter OT Err. UL(3sigma)
(mid, days) (s)
2021-07-08 16:59:54 3.92014 77*60 r' n/d n/d 23.1
The photometry is based on the nearby PS1 stars.
Our photometry is consistent with observations of (D'Avanzo et al., GCN
30432; Watson et al., GCN 30436).
GCN Circular 30436
Subject
GRB 210704A: OSIRIS/GTC Observations and Archival Detection of the Possible Host Galaxy
Date
2021-07-10T07:23:45Z (5 years ago)
From
Alan M Watson at UNAM <alan@astro.unam.mx>
Alan M. Watson (UNAM), Eleonora Troja (GSFC/UMD), Rosa L. Becerra (UNAM), Rub��n
S��nchez (INAF), Aishwarya Thakur (INAF), Simone Dichiara (GSFC/UMD), Nat Butler
(ASU), William H. Lee (UNAM), Oc��lotl Lopez (UNAM), Margarita Pereyra (UNAM),
and Srihari Ravi (ASU) report:
We observed the field of GRB 210704A (Berretta et al., GCN Circ. 30375; D'Ai et
al., GCN Circ. 30379; Malacaria & Meegan, GCN Circ. 30380; Kim et al., GCN Circ.
30384) with the OSIRIS instrument on the 10.4 meter GTC telescope.
We observed at two epochs. The first epoch was at 2.10 days after burst and the
second at 5.10 days after burst. At both epochs, we detect a source at the
position of the candidate optical afterglow (Kim et al., GCN Circ. 30384) at a
magnitude consistent with the TNG observations of r~23.3 at 4.1 days (D'Avanzo
et al., GCN Circ. 30432). We also resolve a second fainter (r~24.5 AB mag)
source (S2) located 0.7 arcsec E and 2.4 arcsec S of the OT position.
Our observations indicate only a marginal fading of about 0.2 magnitudes in the
r-band between our two epochs, which is unusually shallow for a GRB afterglow or
for a kilonova.
Archival pre-explosion images of the field reveal the presence of an underlying
faint source (S1), which might be the host galaxy. Based on a deep exposure
obtained in 2012 with the MegaPrime/MegaCam, we estimate a magnitude of r~25.3
+/- 0.2 AB mag for S1. The source S2 is also detected in archival images at a
magnitude consistent with our GTC observations.
Assuming no intrinsic variability, S1 would only partially contribute to the
observed optical light (~25%) and this by itself is not sufficient to explain
the slow fading of the optical emission. Given the ambiguous classification of
the gamma-ray emission, whose duration lies at the intersection between short
and long GRBs, we cannot exclude that the observed flattening marks the onset of
an associated supernova.
Further observations to monitor the evolution of this source are encouraged.
We thank David Garcia and Antonio Cabrera for assistance with these
observations.
GCN Circular 30433
Subject
GRB 210704A: Gemini-North Infrared Source Detection
Date
2021-07-09T21:48:13Z (5 years ago)
From
Jillian Rastinejad at Northwestern Univ. <jillianrastinejad2024@u.northwestern.edu>
J. Rastinejad (Northwestern), A. Levan (Radboud U.), W. Fong (Northwestern), N. R. Tanvir (U. Leicester) and A. Rouco Escorial (Northwestern) report on behalf of a larger collaboration:
We observed the location of GRB 210704A (Kunzweiler et al., GCN 30369; Ursi et al., GCN 30372; Berretta et al., GCN 30375; Prasad et al., GCN 30378; D'Ai et al., GCN 30379) with the Near-Infrared Imager (NIRI) mounted on Gemini-North under Program GN-2021A-Q-109. We obtained 14x60-sec imaging in K-band at a mid-time of 2021 July 9.265 UT (4.45 days post-burst) at an average airmass of 2.1. We detect a faint source consistent with the location of the optical afterglow (Kim et al., GCN 30384; D'Avanzo et al., GCN 30385; Troja et al., GCN 30390; Kann et al., GCN 30391, 30401; Sun et al., GCN 30411). Calibrated to 2MASS and applying the standard AB conversion, we measure a brightness of K_AB = 22.9 +/- 0.3 mag. At present, it is not possible to discern whether the source is point-like or extended, and the degree to which any underlying host galaxy may be contributing (c.f., D'Avanzo et al., GCN 30432).
For comparison, we note that the expected approximate brightness for a kilonova of the same luminosity as GW170817/AT2017gfo at z~0.08 (Levan et al., GCN 30381) is K_AB ~ 22.5 mag at this epoch. Scaled to the nearby galaxy cluster redshift of z~0.2 (Levan et al., GCN 30381; Dichiara et al. GCN 30383), the expected magnitude for such a kilonova becomes K_AB ~ 24.6 mag, considerably fainter than the source detected here. On the other hand, it is plausible that the detected NIR source is a background galaxy at higher redshift (de Ugarte Postigo et al., GCN 30392; D'Avanzo et al., GCN 30432). Concurrent and continued multi-band follow-up is encouraged to discern the nature of this source.
Further NIR observations are planned to assess any variability of the source. We thank the Gemini staff for the rapid scheduling and execution of these observations.
GCN Circular 30432
Subject
GRB 210704A: further TNG optical observations
Date
2021-07-09T20:36:50Z (5 years ago)
From
Paolo D'Avanzo at INAF-OAB <pda.davanzo@gmail.com>
P. D'Avanzo (INAF-OAB), V. D'Elia (ASI-SSDC), S. Campana (INAF-OAB), M. De Pasquale (Istanbul Univ.), A. Melandri (INAF-OAB),
A. Rossi (INAF-OAS), R. Salvaterra (INAF-IASF Mi), G. Tagliaferri (INAF-OAB), M. Cecconi, A. Garcia de Gurtubai Escudero (INAF-TNG)
on behalf of the CIBO collaboration report:
We carried out further observations of the optical afterglow of GRB 210704A (Kim et al. GCN Circ. 30384; D'Avanzo et al. GCN Circ. 30385)
with the Italian 3.6m TNG telescope equipped with the optical camera DOLORES. A series of images were obtained with the i-sdss and r-sdss
filters on 2021-07-08 from 21:22:44 UT to 22:36:58 UT (i.e. about 4.1 days after the burst) under non optimal seeing conditions (2").
A faint source, possibly extended, is detected at the optical afterglow position. With preliminary photometry we derive the following magnitudes:
r = 23.35 +/- 0.16
i = 23.39 +/- 0.14
(AB; calibrated against the SDSS catalogue).
Because of the seeing conditions and the source faintness we cannot definitely confirm if the source is extended or point-like.
Further deep optical observations are encouraged to monitor the light curve evolution and to check if there is any contribution
from an underlying host galaxy.
GCN Circular 30411
Subject
GRB 210704A: CAHA 2.2m telescope optical limit
Date
2021-07-07T22:53:14Z (5 years ago)
From
Youdong HU at IAA-CSIC <huyoudong072@hotmail.com>
T.-R. Sun, Y.-D. Hu, E. Fernandez-Garcia, A. J. Castro-Tirado M. D. Caballero-Garcia, M. A. Castro Tirado (IAA-CSIC), P. Martin-Fernandez (CAHA) on behalf of a larger collaboration, report:
Following the detection of GRB210704A by Fermi (Kunzweiler et al. GCNC 30369), AGILE (Ursi et al. GCNC 30372), AstroSat (Prasad et al. GCNC 30378) and Konus-Wind (Ridnaia et al. GCNC 30388), we triggered the 2.2m CAHA telescope (+ CAFOS) at the Calar Alto Observatory (Almeria, Spain). A series of r-band images were gathered starting on July 6, 20:40 UT (i.e. 2.05 day post trigger). On the co-added image (9 x 300s), no optical object is detected down to 22.7 mag at the afterglow position reported by Swift/XRT (Evans et al. GCNC 30374), Assy (Kim et al. GCNC 30384) and TNG (D'Avanzo et al. GCNC 30385). Combined with the additional detections (de Ugarte Postigo et al. GCNC 30392, Kann et al. GCNC 30391, Kann et al. GCNC 30401), the optical afterglow decaying lightcurve is confirmed.
We thank the staff at Calar Alto observatory for their excellent support.
GCN Circular 30401
Subject
GRB 210704A: OAJ T80 multi-color detections
Date
2021-07-07T10:40:21Z (5 years ago)
From
Alexander Kann at IAA-CSIC <kann@iaa.es>
D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC,
DARK/NBI), C. Thoene, M. Blazek, J. F. Agui Fernandez (all
HETH/IAA-CSIC), N. Maicas, and J. L. Lamadrid (COAJ report:
We observed the afterglow of GRB 210704A (BALROG localization:
Kunzweiler et al., GCN #30369; Fermi/LAT detection: Berretta et al., GCN
#30375; Fermi/GBM detection: Malacaria & Meegan, GCN #30382; AGILE/MCAL
detection: Ursi et al., GCN #30372; AstroSat/CZTI detection: Prasad et
al., GCN #30378; Konus-Wind detection: Ridnaia et al., GCN #30388;
Swift/XRT afterglow detection: D'Ai et al., GCN #30379) with the T80
0.8m telescope at the Observatorio de Javalambre (Teruel, Spain).
Observations consisted of 3 x 300 s in z', i', g' r' each, at midtimes
1.081, 1.093, 1.104, and 1.116 days after the GRB, respectively.
The afterglow (Kim et al., GCN #30384, D'Avanzo et al., GCN #30385, Kann
et al., GCN #30391, de Ugarte Postigo et al., GCN #30392) is
well-detected in g'r', faintly in i' and not in z'. Against four
Pan-STARRS field stars, we measure (AB magnitudes):
g' = 22.42 +/- 0.11 mag;
r' = 22.17 +/- 0.10 mag;
i' = 22.08 +/- 0.23 mag;
z' > 21.5 mag
at the above-mentioned mid-times.
GCN Circular 30392
Subject
GRB 210704A: OSIRIS/GTC spectroscopy
Date
2021-07-06T14:24:06Z (5 years ago)
From
Antonio de Ugarte Postigo at IAA-CSIC <deugarte@iaa.es>
A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), D. A. Kann,
C. Thoene, M. Blazek, J. F. Agui Fernandez (all HETH/IAA-CSIC),
J. P. U Fynbo (DAWN/NBI), L. Izzo (DARK/NBI), N. R. Tanvir (U. Leicester),
G. Lombardi, A. Marante (both GTC) report:
We observed the afterglow of GRB 210704A (BALROG localization:
Kunzweiler et al., GCN #30369; Fermi/LAT detection: Berretta et al.,
GCN #30375; Fermi/GBM detection: Malacaria & Meegan, GCN #30382;
AGILE/MCAL detection: Ursi et al., GCN #30372; AstroSat/CZTI detection:
Prasad et al., GCN #30378; Konus-Wind detection: Ridnaia et al., GCN
#30388; Swift/XRT afterglow detection: D'Ai et al., GCN #30379; optical
afterglow: Kim et al., GCN #30384, D'Avanzo et al., GCN #30385, Kann et
al. GCN #30391) with OSIRIS, mounted on the 10.4 m GTC telescope, at
the Roque de los Muchachos observatory (La Palma, Spain). The
observation consisted of 2x60s acquisition images in r-band followed by
4x600s spectra with grism R1000B, covering the spectral range between
3700 and 7800 AA. The observation started at 21:48:57 UT (26.26 hr after
the burst) and the combined spectrum has an average epoch of 22:18:25
UT (26.75 hr after the burst).
The afterglow is well detected in the acquisition image at an r-band
magnitude of 22.40 +/- 0.07 as compared to several SDSS field stars. The
spectrum shows continuum above 3800 AA with a typical SNR of 5 above
5000 AA.
The detection of continuum down to 3800 AA implies an upper limit on the
redshift of z < 3.15.
We do not detect any absorption or emission features at the redshift of the
field galaxy (z = 0.0817) or field cluster (z = 0.203) reported in by Levan et
al. in GCN #30381. However, a featureless spectrum would be expected
if this event were a short GRB in an intracluster environment.
We note that there is a tentative detection of a broad dip in the continuum at
~ 4050 AA, that could be identified as due to Ly-alpha. However, we caution
that the SNR in this part of the spectrum is very low. This would imply a
redshift of z = 2.34, and could be sustained by further low-significance
detections of OI, SiII and CII. However, we also note that at this redshift
there is no detection of CIV, nor SiIV, which is uncommon but not
unprecedented.
The spectrum is publicly available for inspection at GRBSpec.eu.
GCN Circular 30391
Subject
GRB 210704A: CAHA 2.2m Afterglow Detection
Date
2021-07-06T12:12:22Z (5 years ago)
From
Alexander Kann at IAA-CSIC <kann@iaa.es>
D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC,
DARK/NBI), C. Thoene, M. Blazek, J. F. Agui Fernandez (all
HETH/IAA-CSIC), and P. Martin-Fernandez (CAHA) report:
We observed the afterglow of GRB 210704A (BALROG localization:
Kunzweiler et al., GCN #30369; Fermi/LAT detection: Berretta et al., GCN
#30375; Fermi/GBM detection: Malacaria & Meegan, GCN #30382; AGILE/MCAL
detection: Ursi et al., GCN #30372; AstroSat/CZTI detection: Prasad et
al., GCN #30378; Konus-Wind detection: Ridnaia et al., GCN #30388;
Swift/XRT afterglow detection: D'Ai et al., GCN #30379) with CAFOS
mounted at the 2.2m Calar Alto telescope (Almeria, Spain), under good
conditions but at high airmass. We obtained 5 x 300 s images in i'.
The optical afterglow (Kim et al., GCN #30384, D'Avanzo et al., GCN
#30385) is faintly detected in the stacked image. Against four
Pan-STARRS comparison stars, we derive a preliminary measurement of i' =
21.84 +/- 0.13 mag at 1.09286 ���d after the trigger.
Compared to contemporary observations (D'Avanzo et al., GCN #30385), the
r' - i' color is unremarkable, indicating the afterglow likely does not
suffer from high extinction, and is therefore intrinsically faint. If it
is associated with the surrounding galaxy cluster (Levan et al., GCN
#30381), this would add evidence to the merger-induced ("short") nature
of the event.
GCN Circular 30390
Subject
GRB 210704A: RATIR optical upper limits
Date
2021-07-06T11:51:23Z (5 years ago)
From
Eleonora Troja at NASA/GSFC/UMD <eleonora@umd.edu>
Eleonora Troja (GSFC), Nat Butler (ASU), Alan M. Watson (UNAM),
Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G.
Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC),
Josh Bloom (UCB), Antonino Cucchiara (UVI), Owen Littlejohns (ASU),
Enrico Ramirez-Ruiz (UCSC), Jesus Gonz��lez (UNAM), Carlos
Roman-Zuniga (UNAM), Harvey Moseley (GSFC), John Capone (UMD),
V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report:
We observed the field of GRB 210704A (Berretta et al. GCN 30375,
Ursi et al. GCN 30372, Malacaria et al. GCN 30380) with the
Reionization and Transients Infrared Camera (RATIR) on the 1.5m
Harold Johnson Telescope at the Observatorio Astronomico Nacional on
Sierra San Pedro Martir. The target was visible from 2021/07 6.17 to
2021/07 6.18 UTC (30.72 to 31.18 hours after the BAT trigger), and we
obtained a total of 0.37 hours exposure in the r and i bands.
No source is detected at the position of the candidate optical counterpart
(Kim et al. GCN 30384, D'Avanzo et al. GCN 30385). In comparison with the
SDSS DR9 catalog, we obtain the following upper limits (3-sigma):
r > 22.4
i > 22.1
These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.
We thank the staff of the Observatorio Astronomico Nacional in San Pedro
Martir.
Further observations are planned.
GCN Circular 30389
Subject
GRB 210704A: Swift/UVOT Upper Limits
Date
2021-07-06T10:16:25Z (5 years ago)
From
Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk>
A. A. Breeveld (UCL-MSSL) and A. Y. Lien (GSFC/UMBC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 210704A 53458 s after the LAT trigger
(Kunzweiler et al., GCN Circ. 30369).
No optical afterglow consistent with the XRT position (D'Ai et al. GCN Circ. 30379) nor the optical
positions given by Kim et al., (GCN Circ. 30384) and D'Avanzo et al., (GCN Circ. 30385) 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 initial exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
v 53458 72068 3038 >21.1
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of
E(B-V) = 0.007 in the direction of the burst (Schlegel et al. 1998).
GCN Circular 30388
Subject
Konus-Wind detection of GRB 210704A
Date
2021-07-06T09:51:51Z (5 years ago)
From
Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>
A. Ridnaia, D. Frederiks, S. Golenetskii, A. Lysenko,
D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline
on behalf of the Konus-Wind team, report:
The long-duration GRB 210704A
(BALROG localization: Kunzweiler et al., GCN 30369;
AGILE/MCAL detection: Ursi et al., GCN 30372;
Fermi-LAT detection: Berretta et al., GCN 30375;
AstroSat CZTI detection: Prasad et al., GCN 30378;
Fermi GBM detection: Malacaria & Meegan, GCN 30380)
triggered Konus-Wind at T0=70400.814 s UT (19:33:20.814).
The burst light curve shows a bright peak
in the interval from ~T0 to ~T0+2 s followed by
a weaker pulse peaked at ~T0+4.5 s.
The emission is seen up to ~4 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210704_T70400/
As observed by Konus-Wind, the burst
had a fluence of 2.25(-0.12,+0.14)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+0.528 s,
of 3.31(-0.37,+0.39)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst
(measured from T0 to T0+1.536 s)
is best fit in the 20 keV - 4 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.21(-0.09,+0.10),
the high energy photon index beta = -2.97(-0.31,+0.22),
the peak energy Ep = 271(-14,+14) keV
(chi2 = 56/57 dof).
The spectrum near the maximum count rate
(measured from T0+0.256 to T0+0.768 s)
is best fit in the 20 keV - 4 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.20(-0.12,+0.13),
the high energy photon index beta = -2.84(-0.40,+0.25),
the peak energy Ep = 320(-24,+27) keV
(chi2 = 44/53 dof).
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
GCN Circular 30385
Subject
GRB 210704A: TNG detection of the optical afterglow candidate
Date
2021-07-05T23:15:32Z (5 years ago)
From
Paolo D'Avanzo at INAF-OAB <pda.davanzo@gmail.com>
P. D'Avanzo (INAF-OAB), V. D'Elia (ASI-SSDC), A. Fiorenzano, C. Padilla (INAF-TNG) on behalf of the CIBO collaboration report:
We observed the field of GRB 210704A (Kunzweiler et al., GCN Circ. 30369; Ursi et al., GCN Circ. 30372; Berretta et al., GCN Circ. 30375;
Prasad et al., GCN 30378; Malacaria et al. GCN 30380), covering the position of the X-ray afterglow reported by D'Ai et al. (GCN Circ. 30379)
with the Italian 3.6m TNG telescope equipped with the optical camera DOLORES. A series of images were obtained with the r-sdss filter on
2021-07-05 from 21:13:11 UT to 21:39:50 UT (i.e. about 1.08 days after the burst).
The optical afterglow candidate reported by Kim et al. (GCN Circ. 30384) is clearly detected at the following position (J2000):
RA: 10:36:04.92
Dec: +57:12:59.3
(+/- 0.5").
With preliminary photometry we derive the following magnitude:
r = 22.13 +/- 0.13
(AB; calibrated against the SDSS catalogue).
As noted by Kim et al. (GCN Circ. 30384), this source is not visible in archival SDSS and Pan-STARRS images.
GCN Circular 30384
Subject
GRB 210704A: Assy optical afterglow candidate
Date
2021-07-05T20:32:34Z (5 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
V. Kim (FAI, Pulkovo Observatory), A. Pozanenko (IKI), M. Krugov (FAI),
S. Belkin (IKI), N. Pankov (HSE, IKI) report on behalf of GRB IKI FuN:
We observed the field of GRB 210704A Fermi-LAT (Berretta et al. 2021,
GCN 30375), AGILE/MCAL (Ursi et al. 2021, GCN 30372), AstroSat/CZTI
(Prasad et al. 2021, GCN 30378), Swift/XRT (D'Ai et al. GCN 30379), and
Fermi-GBM (Malacaria et al. GCN 30380) with AZT-20 telescope of
Assy-Turgen observatory starting on 2021-07-05 (UT) 17:42:41.27.
In a stacked image we detect only one object near enhanced XRT position
(D'Ai et al. GCN 30379). Coordinates of the object are (J2000)
10:36:04.88 +57:12:58.5 with uncertainty of 0.5 arcsec in both coordinates.
Preliminary photometry of the object is following
Date UT start t-T0 Exp. Filter OT Err. UL(3sigma)
(mid, days) (s)
2021-07-05 17:42:41.27 0.94407 66*60 r' 22.25 0.13 23.0
The photometry is based on the nearby SDSS-DR12 stars.
The object is not presented in the SDSS DR12, nor in PS1 catalogue. We
suggest the object is the afterglow of GRB 210704A.
GCN Circular 30383
Subject
GRB 210704A: DDOTI upper limit
Date
2021-07-05T18:47:55Z (5 years ago)
From
Simone Dichiara at UMCP/NASA/GSFC <dichiara@umd.edu>
Simone Dichiara (GSFC/UMD), Eleonora Troja (GSFC/UMD), Nat Butler (ASU),
Alan M. Watson (UNAM), Rosa L. Becerra (UNAM), Alexander Kutyrev
(GSFC/UMD), William H. Lee (UNAM),
Oc��lotl Lopez (UNAM), Diego Gonzalez (UNAM), Margarita Pereyra (UNAM) and
Srihari Ravi (ASU) report:
We observed the field of the Fermi/LAT GRB 210704A (Berretta et al. GCN
Circ. 30375, Ursi et al. GCN Circ. 30372, Malacaria et al. GCN Circ. 30380)
with the DDOTI wide-field imager at the Observatorio Astron��mico Nacional
on Sierra San Pedro Martir (http://ddoti.astroscu.unam.mx) starting from
2021-07-05 04:51 to 05:01 UTC (from 9 hours after the trigger). We obtained
a 360 seconds of total exposure in the w filter.
We find no new sources within the XRT error region reported by D'Ai et al.
(GCN Circ. 30379) . Calibrating our images against the APASS catalog we
obtained a 5-sigma limiting magnitude of w = 19.7.
Compared to the USNO-B1, Pan-STARRS DR1, and APASS DR10 catalogs, we detect
no uncataloged sources to our limit.
We also noticed the presence of a galaxy cluster at z~0.2 coincident with
the afterglow localization region and the presence of a bright galaxy about
30" north from the X-ray transient.
We thank the staff of the Observatorio Astronomico Nacional in San Pedro
Martir.
GCN Circular 30381
Subject
GRB 210704A: possible local hosts
Date
2021-07-05T18:32:51Z (5 years ago)
From
Andrew Levan at U.of Leicester <a.levan@astro.ru.nl>
A.J. Levan (Radboud), S. Campana (INAF-OAB), D.A. Kann (HETH/IAA-CSIC), P. D'Avanzo (INAF-OAB) report:
���We note that the Swift XRT localisation (D���Ai et al. GCN 30379) of GRB 210704A detected by Fermi-LAT, Fermi-GBM (Kunzweiler et al. GCN 30369, Malacaria et al. GCN 30380), AGILE (Ursi et al. GCN 30722) and AstroSat (Prasad et al. GCN 30378) lies in a significant galaxy overdensity. Of particular note, the source localisation overlaps the galaxy cluster 400d J1036+5713 at z=0.203. Although there are no apparent galaxies within the XRT localisation visible in the PanSTARRS 3pi imaging of the field, there are numerous likely members of this cluster within a few arcseconds.
Furthermore, an even brighter foreground galaxy WISEA J103604.24+571327.7 lies offset approximately 30��� from the XRT position and has a reported redshift of z=0.0817. This galaxy has I=15.962 +/- 0.007 (and absolute magnitude around -22). Its projected physical offset from the burst position is approximately 45 kpc. Although this offset is significant, the probability of chance alignment remains small.
The burst itself appears dominated by a short-spike, with a fainter tail of emission, and these possible host galaxies are consistent with the hosts and locations of short GRBs (and not of long GRBs). At z=0.203 (or z=0.0817) the isotropic equivalent energy would be E_iso ~ 2e51 erg (or E_iso ~ 3e50 erg at z=0.0817), consistent with SGRBs.
Observations to search for the optical afterglow or possibly rising kilonova emission are strongly encouraged. ���
[GCN OPS NOTE(02Aug21): In the SUBJECT the "200704A" was corrected to "210704A".
In the author list, it should be "P. D'Avanzo", not "P D'Avanzo".
Both z-values given in the 3rd paragraph were listed as 0.0891, but they should be 0.0817.]
GCN Circular 30380
Subject
GRB 210704A: Fermi GBM detection
Date
2021-07-05T17:43:24Z (5 years ago)
From
Christian Malacaria at NASA-MSFC/USRA <cmalacaria@usra.edu>
C. Malacaria (USRA) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:
"At 19:33:24.59 UT on 04 July 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210704A (trigger 647120009 / 210704815),
which was also detected by Fermi-LAT (Berretta et al. 2021, GCN 30375),
AGILE/MCAL (Ursi et al. 2021, GCN 30372), AstroSat/CZTI (Prasad et al. 2021, GCN 30378)
and Swift/XRT (D'Ai et al. 2021, GCN 30379).
The Fermi-GBM on-ground calculated location is consistent with the Swift/XRT position.
The angle from the Fermi LAT boresight at the GBM trigger time is 63 degrees.
The GBM light curve consists of a main bright peak
with a duration (T90) of about 4.7 s (50-300 keV).
The time-averaged spectrum from T0+0.2 s to T0+1.8 s is
best fit by a Band function with Epeak = 286.1 +/- 6.4 keV,
alpha = -0.35 +/- 0.02, and beta = -2.91 +/- 0.12 .
The event fluence (10-1000 keV) in this time interval is
(1.95 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.5 s in the 10-1000 keV band
is 75.9 +/- 0.5 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular 30379
Subject
GRB 210704A: Swift-XRT afterglow detection
Date
2021-07-05T15:34:15Z (5 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
A. D'Ai (INAF-IASFPA), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto),
B. Sbarufatti (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U.
Leicester), A. Melandri (INAF-OAB), T. Sbarrato (INAF-OAB) and P.A.
Evans (U. Leicester) report on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the
Fermi/LAT-detected burst GRB 210704A (Berretta et al. GCN Circ. 30375),
collecting 2.6 ks of Photon Counting (PC) mode data between T0+53.5 ks
and T0+61.1 ks.
An uncatalogued X-ray source is detected and is above the 2SXPS 3-sigma
upper limit at this position, and is therefore likely the GRB
afterglow. Using 2378 s of PC mode data and 2 UVOT images, we find an
enhanced XRT position (using the XRT-UVOT alignment and matching UVOT
field sources to the USNO-B1 catalogue): RA, Dec = 159.02219, +57.21636
which is equivalent to:
RA (J2000): 10h 36m 05.33s
Dec(J2000): +57d 12' 58.9"
with an uncertainty of 3.2 arcsec (radius, 90% confidence). This
position is 5.9 arcmin from the Fermi/LAT position. We cannot
determine at the present time whether the source is fading.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00021454.
The results of the full analysis of the XRT observations are available
at https://www.swift.ac.uk/ToO_GRBs/00021454.
This circular is an official product of the Swift-XRT team.
GCN Circular 30378
Subject
GRB 210704A: AstroSat CZTI detection
Date
2021-07-05T15:15:59Z (5 years ago)
From
Gaurav Waratkar at IIT,Bombay <gauravwaratkar@iitb.ac.in>
V. Prasad (IUCAA), P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute
(IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao
(IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat
CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al,
2020, arxiv:2011.07067) showed detection of a short GRB 210704A, which
was also detected by Fermi - GBM (Trigger 647120009 / GRB210704815),
Fermi-LAT (GCN 30375), and AGILE/MCAL (GCN 30372).
The source was clearly detected in the 20-200 keV energy range. The
light curve showed multiple peaks of emission with the strongest peak at
2021-07-04 19:33:24.4 UT. The measured peak count rate associated with
the burst is 706 (+179, -132) cts/s above the background in the combined
data of four quadrants, with a total of 359 (+106, -109) cts. The local
mean background count rate was 489 (+6, -8) cts/s. Using cumulative
rates, we measure a T90 of 1.0 (+0.4, -0.4) s.
It was also clearly detected in the CsI anticoincidence (Veto) detector
in the 100-500 keV energy range. In one-second bins, the measured peak
count rate associated with the burst is 1417.7 (+89.9 -97.4) cts/s above
the background in the combined data of four quadrants, with a total of
2430 (+327 -361) cts. The local mean background count rate was 1743.4
(+4.2 -4.2) cts/s.
CZTI GRB detections are reported regularly on the payload site at
http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led
consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC
and PRL. The Indian Space Research Organisation funded, managed and
facilitated the project.
GCN Circular 30375
Subject
GRB 210704A: Fermi-LAT detection
Date
2021-07-05T11:19:51Z (5 years ago)
From
Francesco Longo at U of Trieste,INFN Trieste <franzlongo1969@gmail.com>
A. Berretta (University & INFN Perugia), F. Longo (University and
INFN, Trieste),
M. Axelsson (KTH & Stockholm Univ.), E. Bissaldi (Politecnico and INFN, Bari),
F. Piron (CNRS/IN2P3/LUPM) and M. Arimoto (Kanazawa Univ.)
report on behalf of the Fermi-LAT Collaboration:
On July 4th, 2021, Fermi-LAT detected high-energy emission from GRB 210704A
which was also detected by Fermi-GBM (trigger 647120009/210704815) and
by AGILE/MCAL (GCN 30372).
The best LAT on-ground location is found to be
RA, Dec = 159.08, 57.31 (degrees, J2000)
with an error radius of 0.11 deg (90% containment, statistical error only).
This was 63 deg from the LAT boresight at the time of the GBM trigger:
T0 = 19:33:24.59 UT.
The data from the Fermi-LAT show a very significant increase
in the event rate after the GBM trigger that is temporally and spatially
correlated with the GBM emission with high significance.
The photon flux above 100 MeV in the time interval 0-10s after the GBM trigger
is (1.60 +/- 0.31) E-03 ph/cm2/s.
The estimated photon index above 100 MeV is -1.74 +/- 0.13.
The highest-energy photon is a 16 GeV event which is observed 1.5 seconds
after the GBM trigger.
The Fermi-LAT point of contact for this burst is Alessandra Berretta
(alessandra.berretta@pg.infn.it).
The Fermi-LAT is a pair conversion telescope designed to cover
the energy band from 20 MeV to greater than 300 GeV.
It is the product of an international collaboration between
NASA and DOE in the U.S. and many scientific institutions
across France, Italy, Japan and Sweden.
GCN Circular 30374
Subject
GRB 210704A: Swift ToO observations
Date
2021-07-05T10:22:14Z (5 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the Fermi/LAT GRB 210704A.
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021454
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Fermi/LAT event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a
GCN Circular after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
GCN Circular 30372
Subject
GRB 210704A: AGILE/MCAL detection
Date
2021-07-05T09:00:27Z (5 years ago)
From
Alessandro Ursi at INAF/IAPS <alessandro.ursi@gmail.com>
A. Ursi (INAF/IAPS), C. Pittori, F. Verrecchia (SSDC, and INAF/OAR), M.
Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A. Argan, M. Cardillo, C.
Casentini, Y. Evangelista, G. Piano (INAF/IAPS), F. Lucarelli (SSDC, and
INAF/OAR), A. Bulgarelli, V. Fioretti, F. Fuschino, N. Parmiggiani
(INAF/OAS-Bologna), M. Marisaldi (INAF/OAS-Bologna, and Bergen University),
M. Pilia, A. Trois (INAF/OA-Cagliari), I. Donnarumma (ASI), F. Longo (Univ.
Trieste and INFN Trieste), A. Giuliani (INAF/IASF-Mi), report on behalf of
the AGILE Team:
The AGILE Mini-CALorimeter (MCAL) detected the short GRB 210704A at T0 =
2021-07-04 19:33:25.27 +/- 0.01 s (UTC) (Fermi trigger no.647120009).
The event lasted about 1.06 s and released a total number of ~1333 counts
in the detector (in the 0.4-100 MeV energy range), above an average
background rate of 574 Hz. The MCAL light curve can be found at
http://www.agilescienceapp.it/notices/073773_GRB_552512005.278593.png . The
time-integrated spectrum of the burst can be fitted in the energy range
0.4-10 MeV with a single power-law with ph.ind. = -2.54 -0.28/+0.34,
resulting in a reduced chi-squared of 0.77 (48 d.o.f.) and a fluence of
2.9e-06 ergs/cm^2 (90% confidence level), in the same energy range.
The event is also clearly visible in the scientific ratemeters of the
SuperAGILE (SA; 18-60 keV), MiniCALorimeter (MCAL; 0.4-100 MeV), and
AntiCoincidence (AC; 50-200 keV) detectors. The burst released 450 counts
in the SA detector (above a background rate of 60 Hz), 5040 counts in the
MCAL detector (above a background rate of 1100 Hz), and 15540 counts in the
AC detector (above a background rate of 3570 Hz). The AGILE ratemeters
light curves can be found at:
http://www.agilescienceapp.it/notices/GRB210704A_AGILE_RM.png .
The AGILE-MCAL detector is a CsI detector with a 4 pi FoV, sensitive in the
energy range 0.4-100 MeV. Additional analysis of AGILE data is in progress.
Automatic MCAL GRB alert Notices can be found at:
https://gcn.gsfc.nasa.gov/agile_mcal.html.
GCN Circular 30369
Subject
GRB 210704A: BALROG localization (Fermi Trigger 647120009 / GRB 210704815)
Date
2021-07-04T20:33:32Z (5 years ago)
From
Jochen Greiner at MPE,Garching <jcg@mpe.mpg.de>
F. Kunzweiler, B. Biltzinger, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:
The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
647120009 at 19:33:24 on 04 July 2021 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).
The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 158.1+/-1.2 deg
Decl.(2000.0) = 58.3+/-0.5 deg
We estimate an additional systematic error of 1 deg.
Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210704815/
The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210704815/healpix
The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210704815/json