TITLE: GCN CIRCULAR
NUMBER: 36602
SUBJECT: GRB 240603A: GECAM detection of a short burst
DATE: 24/06/03 04:36:25 GMT
FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn>
Chen-Wei Wang, Shao-Lin Xiong report on behalf of the GECAM team:
GECAM-B was triggered in-flight by a weak short burst, GRB 240603A, at 2024-06-03T02:27:33.950 UTC (T0), which was also detected by INTEGRAL/SPI-ACS (trigger #10729).
The GECAM-B in-flight location (J2000) is:
Ra: 3.5 deg
Dec: -18.5 deg
Err: 5.9 deg (1-sigma, statistical only)
According to the realtime alert data of GECAM-B, this burst mainly consists of a spike and a tail with a total duration of about 1 s. The time-averaged spectrum from T0-0.5 s to T0 could be adequately fit by a power law with high energy exponential cutoff function with a fluence of about 1.21E-6 erg/cm^2 in 20-1000 keV.
We note that these results are very preliminary. Refined analysis will be reported later.
Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM) mission originally consists of two microsatellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS).
View this GCN Circular online at https://gcn.nasa.gov/circulars/36602.
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TITLE: GCN CIRCULAR
NUMBER: 36601
SUBJECT: GRB 240529A: continued SAO RAS optical observations
DATE: 24/06/03 02:31:13 GMT
FROM: Moskvitin Alexander at SAO RAS <mosk(a)sao.ru>
A. S. Moskvitin, O. A. Maslennikova, O. I. Spiridonova (SAO RAS),
report on behalf of the GRB follow-up team.
We observed the field of the GRB 240529A (Eyles-Ferris et al.
GCN 36556; Osborne et al. GCN 36557; Joshi et al. GCN 36560;
Dichiara et al. GCN 36564; Markwardt et al. GCN 36566; Tan et al.
GCN 36578; Kozyrev et al. GCN 36583; Svinkin et al. GCN 36584)
with the SAO RAS 1m telescope Zeiss-1000 equipped with CCD-photometer.
We obtained 11 x 300 sec frames in the Rc band on June 2, 23:09:06 --
June 3, 00:12:47 UT (t_mid - T0 = 4.8628 days).
The OT (Kumar et al. GCN 36559; Fu et al. GCN 36561; Shilling et al.
GCN 36562; Perez-Garcia et al. GCN 36563; Dutton et al. GCN 36568;
Mo et al. GCN 36569; Odeh et al. GCNs 36573, 36592;
de Ugarte Postigo et al. GCN 36574; Adami et al. GCN 36575;
Mohan et al. GCN 36576; Vinko et al. GCN 36577; Lim et al. GCN 36579;
Moskvitin et al. GCNs 36582, 36597; Pankov et al. GCN 36585;
Ror et al., 36589; Hu et al. GCN 36599) is clearly detected
in the stacked frame almost with the same brightness as the day before
R = 20.72 +/- 0.09.
The magnitudes were calibrated using R2 magnitudes of nearby USNO-B1.0
stars.
View this GCN Circular online at https://gcn.nasa.gov/circulars/36601.
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TITLE: GCN CIRCULAR
NUMBER: 36599
SUBJECT: GRB 240529A: OSN optical detection
DATE: 24/06/02 20:53:59 GMT
FROM: Youdong HU at INAF-OAB <huyoudong072(a)hotmail.com>
Y.-D. Hu (INAF-OAB), F. Aceituno, E. Fernandez-Garcia, A. J. Castro-Tirado, I. Perez-Garcia, S.-Y. Wu, M.D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy (IAA-CSIC), on behalf of a larger collaboration, report:
Following the detection of GRB 240529A by Swift (Eyles-Ferris et al. GCNC 36556), we triggered the 1.5m telescope of the Observatiorio Sierra Nevada (OSN) near Granada, Spain. Observations in the RI bands began on Jun. 1 at 01:06 UT (~ 2.9 days post burst). The afterglow is clearly detected with 19.4+-0.1 mag in the I-band image (exposure 300 s) within the enhanced XRT/Swift position (Osborne et al. GCNC 36557). Our result is consistent with previous reports from GOTO (Kumar et al. GCNC 36559), NOT (Fu et al. GCNC 36561), UVOT (Shilling et al. GCNC 36562), BOOTES (Perez-Garcia et al., GCNC 36563), Skynet (Dutton et al., GCNC 36568), WINTER (Mo et al., GCNC 36569), AKO (Odeh et al. GCNC 36573), GTC (de Ugarte Postigo et al., GCNC 36574), T193/MISTRAL (Adami et al., GCNC 36575), GROWTH (Mohan et al., GCNC 36576), Konkoly (Vinko et al., GCNC 36577), MAAO (Gu et al., GCNC 36579), SAO (Moskvitin et al., GCNC 36582, GCNC 36594), Mondy (Pankov et al., GCNC 36585) and DFOT (Ror et al., GCNC 36589). Further imaging is ongoing.
We thank the staff at OSN for their excellent support.
View this GCN Circular online at https://gcn.nasa.gov/circulars/36599.
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TITLE: GCN CIRCULAR
NUMBER: 36598
SUBJECT: The EP-WXT source triggered on June 1st is likely a flaring star
DATE: 24/06/02 16:47:13 GMT
FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn>
C. Y. Wang (THU), H. N. Yang (NAOC, CAS), S. X. Wen (NAOC, CAS), W. X. Wang (NAOC, CAS), W. Yuan, Z. X. Ling, Y. Liu, C. Zhang, C. C. Jin, H. Q. Cheng, W. Chen, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, H. Y. Liu, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, H. Sun, Y. L. Wang, Q.Y. Wu, X. P. Xu, Y. F. Xu, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang (NAOC, CAS), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team
The candidate X-ray transient (RA=336.13, DEC=-58.429) triggered by the Wide-field X-ray Telescope (WXT) on board Einstein Probe (EP) at 17:15:42.949 UT on June 1st, 2024 is likely a stellar flare associated with the Eruptive Variable UPM J2224-5826.
Upon the detection of the event by WXT, the onboard processing and triggering unit triggered automated follow-up observation by the Follow-up X-ray Telescope (FXT) on board EP. The observation started at 2024-06-01T17:17:40, about 2 minutes after the WXT detection, with a net exposure time of 3.0 ks.
Within the error circle of WXT, an X-ray source was clearly detected at R.A. = 336.101 deg, DEC = -58.437 deg, with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). The FXT position is 3.3 arcsec away from a known X-ray source, 1eRASS J222424.3-582612, which has an archival flux of 2.48 x 10^-13 erg/s/cm^2 in the 0.2-2.3 keV band. The source is likely associated with a possible M-type dwarf star, UPM J2224-5826, approximately 16 pc in distance. The spectrum can be well fitted with a model comprising two apec components with a temperature of 0.89 (-0.07/+0.05) keV and 2.9 (+/- 0.3) keV, respectively. The flux of the FXT source is 3.0 (+/- 0.1) x 10^-11 erg/s/cm^2 in the 0.5-10 keV range, which is two orders of magnitude higher than the eROSITA flux. If the FXT source is indeed associated with the M star, the flare reached a peak luminosity of 7.6 x 10^29 erg/s in the 0.5-4.0 keV range. (The quoted errors of the parameters derived above are at the 90% C.L.). We thus suggest that the X-ray flare detected by WXT is likely from the M dwarf star.
Please note that EP-FXT is currently undergoing in-flight calibration. The derived source parameters may be subject to larger uncertainties, so please use them with caution. 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). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES.
View this GCN Circular online at https://gcn.nasa.gov/circulars/36598.
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TITLE: GCN CIRCULAR
NUMBER: 36597
SUBJECT: GRB 240529A: further SAO RAS optical observations
DATE: 24/06/02 13:30:58 GMT
FROM: Moskvitin Alexander at SAO RAS <mosk(a)sao.ru>
A. S. Moskvitin, O. I. Spiridonova, O. A. Maslennikova (SAO RAS),
report on behalf of the GRB follow-up team.
We observed the field of the GRB 240529A (Eyles-Ferris et al.
GCN 36556; Osborne et al. GCN 36557; Joshi et al. GCN 36560;
Dichiara et al. GCN 36564; Markwardt et al. GCN 36566; Tan et al.
GCN 36578) with the SAO RAS 1m telescope Zeiss-1000 equipped
with CCD-photometer. We obtained 8 x 300 sec frames in the Rc band
on June 1, 23:30:20 -- June 2, 00:16:50 UT (t_mid - T0 = 3.8716 days).
The OT (Kumar et al. GCN 36559; Fu et al. GCN 36561; Shilling et al.
GCN 36562; Perez-Garcia et al. GCN 36563; Dutton et al. GCN 36568;
Mo et al. GCN 36569; Odeh et al. GCNs 36573, 36592;
de Ugarte Postigo et al. GCN 36574; Adami et al. GCN 36575;
Mohan et al. GCN 36576; Vinko et al. GCN 36577; Lim et al. GCN 36579;
Pankov et al. GCN 36585; Ror et al., 36589) is clearly detected
in the stacked frame with the brightness of R = 20.7 +/- 0.1.
The magnitudes were calibrated using R2 magnitudes of nearby USNO-B1.0
stars.
View this GCN Circular online at https://gcn.nasa.gov/circulars/36597.
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TITLE: GCN CIRCULAR
NUMBER: 36596
SUBJECT: LIGO/Virgo/KAGRA S240601aj: Updated Sky localization
DATE: 24/06/02 12:35:26 GMT
FROM: carl.haster(a)unlv.edu
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
We have conducted further analysis of the LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S240601aj (GCN Circular 36587). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.offline0.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page:
https://gracedb.ligo.org/superevents/S240601aj
For the Bilby.offline0.multiorder.fits,0 sky map, the 90% credible region is 2009 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 5366 +/- 2095 Mpc (a posteriori mean +/- standard deviation).
For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/.
[1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. (2023) arXiv:2307.13380
View this GCN Circular online at https://gcn.nasa.gov/circulars/36596.
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TITLE: GCN CIRCULAR
NUMBER: 36594
SUBJECT: LIGO/Virgo/KAGRA S240601co: Identification of a GW compact binary merger candidate
DATE: 24/06/01 23:56:46 GMT
FROM: chiajuichou(a)nycu.edu.tw
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
We identified the compact binary merger candidate S240601co during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2024-06-01 23:10:04.028 UTC (GPS time: 1401318622.028). The candidate was found by the GstLAL [1], MBTA [2], and PyCBC Live [3] analysis pipelines.
S240601co is an event of interest because its false alarm rate, as estimated by the online analysis, is 6e-11 Hz, or about one in 1e3 years. The event's properties can be found at this URL:
https://gracedb.ligo.org/superevents/S240601co
After parameter estimation by RapidPE-RIFT [4], the classification of the GW signal, in order of descending probability, is BBH (>99%), NSBH (<1%), Terrestrial (<1%), or BNS (<1%).
Assuming the candidate is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [5] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [5] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is 7%.
Two sky maps are available at this time and can be retrieved from the GraceDB event page:
* bayestar.multiorder.fits,0, an initial localization generated by BAYESTAR [6], distributed via GCN notice about 27 seconds after the candidate event time.
* bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [6], distributed via GCN notice about 5 minutes after the candidate event time.
The preferred sky map at this time is bayestar.multiorder.fits,1. For the bayestar.multiorder.fits,1 sky map, the 90% credible region is 1080 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1376 +/- 385 Mpc (a posteriori mean +/- standard deviation).
For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/.
[1] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. (2023) arXiv:2305.05625
[2] Aubin et al. CQG 38, 095004 (2021) doi:10.1088/1361-6382/abe913
[3] Dal Canton et al. ApJ 923, 254 (2021) doi:10.1088/1361-6382/abe913
[4] Rose et al. (2022) arXiv:2201.05263 and Pankow et al. PRD 92, 023002 (2015) doi:10.1103/PhysRevD.92.023002
[5] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe
[6] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013
View this GCN Circular online at https://gcn.nasa.gov/circulars/36594.
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TITLE: GCN CIRCULAR
NUMBER: 36593
SUBJECT: Swift Trigger 1232465 is not a GRB
DATE: 24/06/01 21:50:38 GMT
FROM: David Palmer at LANL <palmer(a)lanl.gov>
J.D. Gropp (PSU), R. Gupta (NASA/GSFC), A. Y. Lien (U Tampa) and
D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 21:30:20 UT, the Swift Burst Alert Telescope (BAT) triggered on
a rate increase and a marginal peak in the resulting image
(trigger=1232465). Swift slewed immediately to the peak location.
The BAT on-board calculated location is
RA, Dec 108.731, -6.206 which is
RA(J2000) = 07h 14m 55s
Dec(J2000) = -06d 12' 20"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The available BAT light curve does not show any
significant fluctuations above the noise level.
The XRT began observing the field at 21:31:59.9 UT, 99.7 seconds after
the BAT trigger. No source was detected in 559 s of promptly downlinked
data. We are waiting for the full dataset to detect and localise the
XRT counterpart.
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 104 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 25% of
the BAT 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
BAT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the large, but uncertain, extinction expected.
Due to the marginal significance of the initial rate trigger (6.5 sigma
in 0.032 s) and the BAT image (6.8 sigma), and the lack of an observed
counterpart in the XRT and UVOT data, we believe that this is probably
a statistical fluctuation and not a real astrophysical event.
Further analysis of the complete downlinked dataset will be used
to conclusively rule out this event.
View this GCN Circular online at https://gcn.nasa.gov/circulars/36593.
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