Gamma-ray Burst 240807A = EP 240807a

(All information courtesy of the instrument teams.)

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Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 07 Aug 24 05:43:14 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      48
TRIGGER_NUM:     744702170
GRB_RA:          244.117d {+16h 16m 28s} (J2000),
                 245.252d {+16h 21m 00s} (current),
                 241.852d {+16h 07m 24s} (1950)
GRB_DEC:         -81.383d {-81d 22' 59"} (J2000),
                 -81.442d {-81d 26' 30"} (current),
                 -81.257d {-81d 15' 23"} (1950)
GRB_ERROR:       27.98 [deg radius, statistical plus systematic]
GRB_INTEN:       66 [cnts/sec]
DATA_SIGNIF:     4.50 [sigma]
INTEG_TIME:      1.024 [sec]
GRB_DATE:        20529 TJD;   220 DOY;   24/08/07
GRB_TIME:        20565.20 SOD {05:42:45.20} UT
GRB_PHI:         225.00 [deg]
GRB_THETA:       160.00 [deg]
DATA_TIME_SCALE: 1.0240 [sec]
HARD_RATIO:      0.00
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:     100%  Unreliable location
2nd_MOST_LIKELY:   0%  n/a
DETECTORS:       0,0,0, 0,0,0, 1,0,1, 0,0,0, 0,0,
SUN_POSTN:       137.69d {+09h 10m 45s}  +16.27d {+16d 16' 06"}
SUN_DIST:        108.67 [deg]   Sun_angle= -7.2 [hr] (East of Sun)
MOON_POSTN:      168.07d {+11h 12m 16s}   +7.06d {+07d 03' 39"}
MOON_DIST:        95.09 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      310.15,-21.55 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      262.79,-58.60 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240807238/quicklook/glg_lc_medres34_bn240807238.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 309.65,19.05 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 07 Aug 24 13:46:55 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     744702170
GRB_RA:          346.220d {+23h 04m 53s} (J2000),
                 346.778d {+23h 07m 07s} (current),
                 345.040d {+23h 00m 09s} (1950)
GRB_DEC:         -82.580d {-82d 34' 47"} (J2000),
                 -82.447d {-82d 26' 47"} (current),
                 -82.850d {-82d 50' 58"} (1950)
GRB_ERROR:       7.14 [deg radius, statistical only]
GRB_DATE:        20529 TJD;   220 DOY;   24/08/07
GRB_TIME:        20565.20 SOD {05:42:45.20} UT
GRB_PHI:         232.95 [deg]
GRB_THETA:       148.02 [deg]
E_RANGE:         50.000 - 300.000 [keV]
LOC_ALGORITHM:   415 (Gnd S/W Version number)
SUN_POSTN:       138.01d {+09h 12m 02s}  +16.17d {+16d 10' 24"}
SUN_DIST:        112.75 [deg]   Sun_angle= 10.1 [hr] (West of Sun)
MOON_POSTN:      171.64d {+11h 26m 34s}   +5.18d {+05d 10' 52"}
MOON_DIST:       102.71 [deg]
MOON_ILLUM:      9 [%]
GAL_COORDS:      306.92,-33.70 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      286.53,-63.84 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240807238/quicklook/glg_lc_medres34_bn240807238.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240807238/quicklook/glg_locplot_all_bn240807238.png
COMMENTS:        Fermi-GBM Final Position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file should be available by the time this FINAL notice is produced.  
COMMENTS:        This notice has human-in-the-loop processing.

GCN Circular #37088
Y. C. Fu (BNU), S. Q. Jiang, J. W. Hu, Z. X. Ling, W. D. Zhang, Y. Liu, C. = C. Jin, C. Zhang, H. Q. Cheng, W. Chen, C. Z. Cui, D. W. Fan, H. B. Hu, M. = H. Huang, D. Y. Li, H. Y. Liu, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. = W. Pan, X. Pan, H. Sun, W. X. Wang, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. X= u, H. N. Yang, W. Yuan, M. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, = CAS), Y. Chen, S. M. Jia, W. W. Cui, D. W. Han, C. K. Li, L. M. Song, X. F.= Zhao, J. Zhang, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ES= A), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (C= EA) on behalf of the Einstein Probe team=C2=A0
We report on the detection of a fast X-ray transient designated EP240807a, = by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mi= ssion. The transient started at 2024-08-07T05:42:48(UTC). The WXT position = of EP240807a is R.A.=3D 300.970 deg, DEC =3D -68.777 deg (J2000) with an un= certainty of 2.5 arcmin (radius, 90% C.L. statistical and systematic). The = lightcurve of the transient observed by the WXT lasts around 70 seconds and= has a peak flux of ~1 x 10^-8 erg/s/cm^2 in the 0.5-4 keV band. The averag= e 0.5-4 keV spectrum can be fitted with an absorbed power law with a photon= index of 0.9(-0.8, +1.7) (with a freely fitted column density value of 1.1= (-1.1, +1.6) x 10^21 cm^-2). The derived average unabsorbed 0.5-4 keV flux = is 1.7(-0.6, +0.7) x 10^(-10) erg/s/cm^2. The uncertainties are at the 90% = confidence level for the above parameters.
No previously known bright X-ray sources are found within the error circle = around the source position. Following the WXT detection, we performed a fol= low-up observation with the Follow-up X-ray Telescope (FXT) on board the EP= . Further follow-up observations are encouraged to identify the nature of t= his X-ray transient.=C2=A0
Launched on January 9, 2024, EP is a space X-ray observatory to monitor the= soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook= of X-ray and Gamma-ray Astrophysics).
GCN Circular #37089
The Fermi GBM team reports the detection of a likely Short GRB.
At 05:42:45 UT on 7 Aug 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240807A (trigger 744702170 / 240807238). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 346.2, Dec = -82.6 (J2000 degrees, equivalent to J2000 23h 04m, -82d 34'), with a statistical uncertainty of 7.1 degrees. The angle from the Fermi LAT boresight is 148.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240807238/quicklook/glg_skymap_all_bn240807238.png
The HEALPix FITS file, including the estimated localization systematic, can be f ound here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240807238/quicklook/glg_healpix_all_bn240807238.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240807238/quicklook/glg_lc_medres34_bn240807238.gif
GCN Circular #37108
A. Santos (CBPF), L. Santana-Silva (CBPF), C. R. Bom (CBPF), C. D. Kilpatri= ck (Northwestern), P. Darc (CBPF), C. Mendes de Oliveira (IAG-USP) report o= n behalf of the STEP collaboration:
We conducted optical follow up with the T80S 0.8-m robotic telescope (Santo= s et al., 2024, MNRAS, 529, 59) of the fast X-ray transient EP240807a disco= vered by the Einstein Probe (GCN [36691](https://gcn.nasa.gov/circulars/36691). EP240807a was temporally coincident with the Fermi-GBM alert from GRB= 240807A (GCN 37089) and subsequently localized by the Follow-up X-ray Teles= cope (FXT) on Einstein probe (GCN 37097). The T80S observations started on = August 8 07:40 UT (~16 hours after the trigger). We obtained images totalin= g 360s (2x180s) in g-band and 720s (3x240s) in r-band with the T80S camera = centered at the position of the FXT counterpart at R.A.=3D20:03:52.90 and D= ecl.=3D-68:46:37.20 (J2000). Subtracting DECAM template images from the T8= 0S frames using photpipe (Rest et al., 2005), we do not detect any transien= t source in our difference images and derive 3-sigma limiting magnitudes of= g > 21.9 and r > 22.2 mag for any optical transient.
GCN Circular #37111
SVOM/GRM team: Chen-Wei Wang, Yong-Wei Dong, Jiang-Tao Liu, Shi-Jie Zheng, = Jian-Chao Sun, Wen-Jun tan, Jiang He, Min Gao, Hao-Xuan Guo, Yue Huang, Lu = Li, Yong-Ye Li, Hong-Wei Liu, Xin Liu, Hao-Li Shi, Li-Ming Song, You-Li Tuo= , Hao-Xi Wang, Jin Wang, Jin-Zhou Wang, Ping Wang, Rui-Jie Wang, Yu-Xi Wang= , Bo-Bing Wu, Shao-Lin Xiong, Jian-Ying Ye, Yi-Tao Yin, Wen-Hui Yu, Fan Zha= ng, Li Zhang, Peng Zhang, Shuang-Nan Zhang, Wen-Long Zhang, Yan-Ting Zhang,= Shu-Min Zhao, Xiao-Yun Zhao, Chao Zheng (IHEP), Maria-Grazia Bernardini (L= UPM/INAF-OAB), Laurent Bouchet (IRAP), David Corre (CEA), Tais Maiolino (LU= PM), Fr=C3=A9d=C3=A9ric Piron (LUPM) , St=C3=A9phane Schanne (CEA), Jingwei= Wang (IAP)
SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (I= HEP), St=C3=A9phane Basa (LAM), JeanLuc Att=C3=A9ia (IRAP), Arnaud Claret (= CEA), Zi-Gao Dai (USTC), Fr=C3=A9d=C3=A9ric Daigne (IAP), Jin-Song Deng (NA= OC), Andrea Goldwurm (APC), Diego G=C3=B6tz (CEA), Xu-Hui Han (NAOC), Cyril= Lachaud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs= .Paris), Jing Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Bing Zhang (= UNLV)
report on behalf of the SVOM team:
During the commissioning phase, the SVOM/GRM has detected GRB 240807A which= was first detected by EP-WXT (GCN 37088), Fermi/GBM (GCN 37089) and EP-FXT= (GCN 37097).
With the event-by-event data downloaded through the X-band ground station, = the GRB was detected with a significance of about 6 sigma in the GRM around= the Fermi/GBM trigger time at 2024-08-07T05:42:45 UT (T0). The GRM light c= urve shows that the duration of this burst is about 4 s.
The GRM light curve can be found here: https://www.bursthub.cn/admin/static/svgrb240807A.png
At the time of this burst, SVOM/ECLAIRs was not in operational mode.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission l= ed by the Chinese National Space Administration (CNSA, China), National Cen= ter for Space Studies (CNES, France) and the Chinese Academy of Sciences (C= AS, China), which is dedicated to observing gamma-ray bursts and other tran= sient phenomena in the energetic universe. GRM is developed by the Institut= e of High Energy Physics (IHEP) of CAS.
The SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang@ih= ep.ac.cn)
GCN Circular #37118
O. Guiffreda (UMD), J. Durbak (UMD), A. S. Kutyrev (NASA/GSFC), E. Troja (U Rome), K. De (MIT), S. B. Cenko (NASA/GSFC), Atri, S. (U Rome)
Following the Einstein Probe detection (GCN 37088), we observed the transient field in the J filter with PRIME ~21 hours after the EP/WXT detection. The total exposure time of the observation was 1200s.
We report that no new near-infrared detection was discovered within the EP/FXT (GCN 37097) error radius down to ~21.5 AB mag in J band.
At the position of the fast x-ray transient, we detect no uncatalogued source in J band. Using nearby VISTA Hemispherical Survey (VHS) stars for preliminary calibration we derive the following limiting magnitudes, not corrected for Galactic extinction:
```
Filter | Mag(AB)        | Total exposure time (s) 
-------|----------------|-------------------------
J      | >21.5 +/- 0.1  | 1200
```
PRIME is a 1.8m telescope with 1.56 square degree FOV (0.5 arcsec/pixel) located in Sutherland, South Africa at the South African Astronomical Observatory (SAAO) (Kutyrev et al. 2023, Yama et al. 2023).
We thank the Osaka University observers at PRIME and the staff at SAAO for their support with these observations.
GCN Circular #37120
A. Ridnaia, D. Frederiks, D. Svinkin, A. Lysenko, and T. Cline on behalf of the Konus-Wind team,
A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi GBM team,
E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team
and
J. DeLaunay, A. Tohuvavohu, S. Barthelmy, J. Cummings, H. Krimm, and D. Palmer on behalf of the Swift-BAT team, report:
The long-duration GRB 240807A (Fermi GBM detection: Fermi GBM team, GCN 37089; SVOM-GRM detection: Wang et al., GCN 37111) was detected by Fermi (GBM), Konus-Wind, in the waiting mode, INTEGRAL (SPI-ACS), Swift (BAT), and SVOM (GRM) at about 20565 s UT (05:42:45). The burst was outside the coded field of view of the BAT.
We have triangulated it to a GBM-Konus annulus centered at RA(2000)=295.559 deg (19h 42m 14s) Dec(2000)=-22.821 deg (-22d 49' 15"), whose radius is 32.402 +/- 32.402 deg (3 sigma).
This localization may be improved.
The fast X-ray transient EP 240807a (Fu et al., GCN 37088; Hu et al., GCN 37097) is inside the annulus and is consistent with the Konus-Wind ecliptic latitude response, supporting the association of the GRB and EP 240807a.
A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB240807A/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density.
The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular.
GCN Circular #37130
A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report:
The long-duration GRB 240807A (Fermi GBM detection: Fermi GBM team, GCN 37089; SVOM-GRM detection: Wang et al., GCN 37111; IPN triangulation: Ridnaia et al., GCN 37120) was detected by Konus-Wind (KW) in the waiting mode at T0~20568 s UT (05:42:48).
A Bayesian block analysis of the KW waiting mode data in the 20-300 keV band reveals a >8 sigma count rate increase in the interval from ~T0+0.143 s to ~T0+3.087 s.
Corrected for the propagation time, the burst started ~4 s before the start time of the fast X-ray transient EP240807a (T0(EP)=05:42:48 UT; Fu et al., GCN 37088). The positional (Ridnaia et al., GCN 37120) and temporal coincidence of GRB 240807A with the EP transient supports the conclusion that EP240807a is the GRB counterpart.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB240807A/
The time-integrated spectrum of the burst, measured from T0+0.143 s to T0+3.087 s, cat be described by a power law with exponential cutoff (CPL) model dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.60(-0.95,+3.74) and Ep = 134(-35,+285) keV.
The total burst fluence is 4.24(-0.01,+4.68)x10^-7 erg/cm^2, and the 2.944 s peak energy flux, measured from T0+0.143 s, is 1.43(-0.27,+1.61)x10^-7 erg/cm^2. (both in the 20 keV - 10 MeV energy range).
All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary.
GCN Circular #37153
O. Guiffreda (UMD), J. Durbak (UMD), A. S. Kutyrev (NASA/GSFC), E. Troja (U Rome), K. De (MIT), S. B. Cenko (NASA/GSFC), S. Atri(U Rome)
Following the Einstein Probe detection (GCN 37088), we observed the transient field in the H filter with PRIME ~22 hours after the EP/WXT detection. This observation was taken directly after the J-band observations reported in GCN 37118. The total exposure time of the observation was 600s.
At the position of the fast x-ray transient, we detect no uncatalogued source in H band. Using nearby 2MASS stars for preliminary calibration we derive the following limiting magnitudes, not corrected for Galactic extinction:
```
Filter | Mag(AB)        | Total exposure time (s) 
-------|----------------|-------------------------
H      | >21.1 +/- 0.1  | 600
```
PRIME is a 1.8m telescope with 1.56 square degree FOV (0.5 arcsec/pixel) located in Sutherland, South Africa at the South African Astronomical Observatory (SAAO) (Kutyrev et al. 2023, Yama et al. 2023).
We thank the Osaka University observers at PRIME and the staff at SAAO for their support with these observations.

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