TITLE: GCN CIRCULAR
NUMBER: 34774
SUBJECT: Swift Triggers 1192745 and 1192747 are not astrophysical events
DATE: 23/09/27 07:46:34 GMT
FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk>
K. L. Page (U Leicester) reports on behalf of the Neil Gehrels Swift
Observatory Team:
To conclude the summary of false triggers caused by the Swift star tracker
loss-of-lock event on 2023-09-26, triggers 1192745 and 1192747 (at 22:53
and 23:00 UT respectively) were also not astrophysical events.
View this GCN Circular online at https://gcn.nasa.gov/circulars/34774.
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TITLE: GCN CIRCULAR
NUMBER: 34773
SUBJECT: LIGO/Virgo/KAGRA S230927l: Identification of a GW compact binary merger candidate
DATE: 23/09/27 05:48:48 GMT
FROM: Dongfeng Gao at Innovation Academy for Precision Measurement Science and Technology,Chinese Academy of Sciences <dfgao(a)apm.ac.cn>
The LIGO Scientific Collaboration, the Virgo Collaboration, and the
KAGRA Collaboration report:
We identified the compact binary merger candidate S230927l during
real-time processing of data from LIGO Hanford Observatory (H1) and
LIGO Livingston Observatory (L1) at 2023-09-27 04:37:29.118 UTC (GPS
time: 1379824667.118). The candidate was found by the CWB [1], GstLAL
[2], MBTA [3], PyCBC Live [4], and SPIIR [5] analysis pipelines.
S230927l is an event of interest because its false alarm rate, as
estimated by the online analysis, is 1.1e-08 Hz, or about one in 2
years. The event's properties can be found at this URL:
https://gracedb.ligo.org/superevents/S230927l
The classification of the GW signal, in order of descending
probability, is BBH (98%), Terrestrial (2%), BNS (<1%), or NSBH (<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%. [6] Using the masses and spins inferred from the
signal, the probability of matter outside the final compact object
(HasRemnant) is <1%. [6] 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 <1%.
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 [7], distributed via GCN notice about 29 seconds after the
candidate event time.
* bayestar.multiorder.fits,1, an initial localization generated by
BAYESTAR [7], 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
1851 deg2. Marginalized over the whole sky, the a posteriori
luminosity distance estimate is 3359 +/- 951 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/userguide/.
[1] Klimenko et al. PRD 93, 042004 (2016)
[2] Tsukada et al. arXiv:2305.06286 (2023) and Ewing et al.
arXiv:2305.05625 (2023)
[3] Aubin et al. CQG 38, 095004 (2021)
[4] Dal Canton et al. ApJ 923, 254 (2021)
[5] Chu et al. PRD 105, 024023 (2022)
[6] Chatterjee et al. ApJ 896, 54 (2020)
[7] Singer & Price PRD 93, 024013 (2016)
View this GCN Circular online at https://gcn.nasa.gov/circulars/34773.
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TITLE: GCN CIRCULAR
NUMBER: 34772
SUBJECT: Swift Triggers 1192740, 1192742 and 1192743 are not astrophysical events
DATE: 23/09/26 22:48:32 GMT
FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk>
K. L. Page (U Leicester) report on behalf of the Neil Gehrels Swift
Observatory Team:
As of 22:45 UT, Swift continues to have star tracker loss-of-lock problems. Swift
triggers 1192740, 1192742 and 1192743 are also not astrophysical events. As a
reminder, please verify that the Swift GCN notices do not have the comment
COMMENTS: This trigger occured while the StarTracker had lost lock, so it is possibly bogus.
before assuming an event is real. Further retraction circulars will not be published until the loss-of-lock problem is cleared.
View this GCN Circular online at https://gcn.nasa.gov/circulars/34772.
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TITLE: GCN CIRCULAR
NUMBER: 34771
SUBJECT: Swift Triggers 1192735 and 1192737 are not astrophysical events
DATE: 23/09/26 22:32:45 GMT
FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk>
J. A. Kennea (PSU) and K. L. Page (U Leicester) report on behalf of
the Neil Gehrels Swift Observatory Team:
The Swift triggers 1192735 and 1192737 at 21:51:11 UT and 22:11:52 respectively, were caused by star tracker loss-of-lock problems, and are not astrophysical events.
View this GCN Circular online at https://gcn.nasa.gov/circulars/34771.
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TITLE: GCN CIRCULAR
NUMBER: 34770
SUBJECT: LIGO/Virgo/KAGRA S230922q: Updated Sky localization
DATE: 23/09/26 19:40:42 GMT
FROM: naresh.adhikari(a)ligo.org
The LIGO Scientific Collaboration, the Virgo Collaboration, and the
KAGRA Collaboration report:
We have conducted further analysis of the LIGO Hanford Observatory
(H1) and LIGO Livingston Observatory (L1) data around the time of the
compact binary merger (CBC) candidate S230922q (GCN Circular 34756). 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/S230922q
For the Bilby.offline0.multiorder.fits,0 sky map, the 90% credible
region is 4658 deg2. Marginalized over the whole sky, the a posteriori
luminosity distance estimate is 6653 +/- 2348 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/userguide/.
[1] Ashton et al. ApJS 241, 27 (2019)
View this GCN Circular online at https://gcn.nasa.gov/circulars/34770.
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TITLE: GCN CIRCULAR
NUMBER: 34769
SUBJECT: Konus-Wind detection of GRB 230919A
DATE: 23/09/26 13:36:05 GMT
FROM: Y. Temiraev at Ioffe Institute <yuri.temiraev(a)mail.ioffe.ru>
Y. Temiraev, D. Svinkin, D. Frederiks, M. Ulanov,
A. Tsvetkova, A. Lysenko, A. Ridnaia, and T. Cline
on behalf of the Konus-Wind team, report:
The short-duration GRB 230919A
(Fermi-GBM detection: The Fermi GBM team, GCN Circ. 34737;
Scotton et al., GCN Circ. 34750;
AstroSat CZTI detection: Navaneeth et al., GCN Circ. 34742;
Swift/BAT-GUANO detection: DeLaunay et al., GCN Circ. 34747;
IPN triangulation: Kozyrev et al., GCN Circ. 34752)
triggered Konus-Wind at T0=61103.312 s UT (16:58:23.312).
The burst light curve shows a multipeaked structure
which starts at ~T0-0.4 s and has a total duration of ~2.4 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/GRB230919_T61103/
As observed by Konus-Wind, the burst
had a fluence of 8.37(-2.57,+3.19)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0+0.430 s,
of 1.44(-0.72,+0.81)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The spectrum of the burst (measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 4 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.88(-0.25,+0.37)
and Ep = 1452(-629,+1078) keV (chi2 = 69/83 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.1
(chi2 = 69/82 dof).
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
View this GCN Circular online at https://gcn.nasa.gov/circulars/34769.
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TITLE: GCN CIRCULAR
NUMBER: 34768
SUBJECT: LIGO/Virgo/KAGRA S230924an: Upper limits from Swift/BAT-GUANO
DATE: 23/09/25 14:58:56 GMT
FROM: Samuele Ronchini at PSU <sjs8171(a)psu.edu>
Samuele Ronchini (PSU), James DeLaunay (U Alabama), Tyler Parsotan (NASA GSFC), Aaron Tohuvavohu (U Toronto), Jamie A. Kennea (PSU), Gayathri Raman (PSU) report:
Swift/BAT was observing >99,9% of the GW localization probability (bayestar.multiorder.fits) at merger time. A fraction 51.5 % of the GW localization posterior is contained inside the BAT coded FoV.
The LVK notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).
Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground.
Using the NITRATES analysis (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), we searched for emission on 8 timescales from 0.128s to 16.384s in the interval [-20,+20] seconds around the merger time. We find no evidence for a signal, and derive the following upper limits.
We quote the 5-sigma flux upper limits in the 15-350 keV band, weighted over the GW localization, for four spectral templates (soft, normal, and hard GRB-like templates described in [arXiv:1612.02395], and spectral shape from GRB170817A [arXiv:1710.05446]) and for four time bins.
In units of 10^-7 erg/s/cm^2:
time_bin (s) soft normal hard GRB170817
------------------------------------
0.256 6.57 5.08 4.62 5.53
1.024 3.35 2.59 2.35 2.82
4.096 1.80 1.39 1.26 1.51
16.38 1.11 0.86 0.78 0.94
The upper limits as function of sky position are plotted here, alongside the GW localization:
https://doi.org/10.5281/zenodo.8374512
The solid and dashed lines indicate the 90% and 50% GW contour levels, respectively.
The corresponding fits file can be found here:
https://doi.org/10.5281/zenodo.8374524
GUANO is a fully autonomous, extremely low latency, spacecraft
commanding pipeline designed for targeted recovery of BAT event mode
data around the times of compelling astrophysical events to enable
more sensitive GRB searches.
A live reporting of Swift/BAT event data recovered by GUANO can be
found at: https://www.swift.psu.edu/guano/
View this GCN Circular online at https://gcn.nasa.gov/circulars/34768.
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TITLE: GCN CIRCULAR
NUMBER: 34767
SUBJECT: LIGO/Virgo/KAGRA S230920al: Upper limits from Swift/BAT-GUANO
DATE: 23/09/25 14:58:51 GMT
FROM: Samuele Ronchini at PSU <sjs8171(a)psu.edu>
Samuele Ronchini (PSU), Gayathri Raman (PSU), Tyler Parsotan (NASA GSFC), Aaron Tohuvavohu (U Toronto), James DeLaunay (U Alabama), Jamie A. Kennea (PSU) report:
Swift/BAT was observing 63.5% of the GW localization probability (bayestar.multiorder.fits) at merger time. A fraction 7.7 % of the GW localization posterior is contained inside the BAT coded FoV.
The LVK notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).
Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground.
Using the NITRATES analysis (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), we searched for emission on 8 timescales from 0.128s to 16.384s in the interval [-20,+20] seconds around the merger time. We find no evidence for a signal, and derive the following upper limits.
We quote the 5-sigma flux upper limits in the 15-350 keV band, weighted over the GW localization, for four spectral templates (soft, normal, and hard GRB-like templates described in [arXiv:1612.02395], and spectral shape from GRB170817A [arXiv:1710.05446]) and for four time bins.
In units of 10^-7 erg/s/cm^2:
time_bin (s) soft normal hard GRB170817
------------------------------------
0.256 9.21 6.79 6.27 7.31
1.024 4.69 3.46 3.19 3.72
4.096 2.51 1.85 1.71 1.99
16.38 1.54 1.13 1.05 1.22
The upper limits as function of sky position are plotted here, alongside the GW localization:
https://doi.org/10.5281/zenodo.8371090
The solid and dashed lines indicate the 90% and 50% GW contour levels, respectively.
The corresponding fits file can be found here:
https://doi.org/10.5281/zenodo.8371099
GUANO is a fully autonomous, extremely low latency, spacecraft
commanding pipeline designed for targeted recovery of BAT event mode
data around the times of compelling astrophysical events to enable
more sensitive GRB searches.
A live reporting of Swift/BAT event data recovered by GUANO can be
found at: https://www.swift.psu.edu/guano/
View this GCN Circular online at https://gcn.nasa.gov/circulars/34767.
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TITLE: GCN CIRCULAR
NUMBER: 34766
SUBJECT: Title: LIGO/Virgo/KAGRA S230919bj: Upper limits from Swift/BAT-GUANO
DATE: 23/09/25 14:58:46 GMT
FROM: Samuele Ronchini at PSU <sjs8171(a)psu.edu>
Samuele Ronchini (PSU), James DeLaunay (U Alabama), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Aaron Tohuvavohu (U Toronto), Gayathri Raman (PSU) report:
Swift/BAT was observing 95.2% of the GW localization probability (Bilby.multiorder.fits) at merger time. A fraction 0.6 % of the GW localization posterior is contained inside the BAT coded FoV.
The LVK notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).
Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground.
Using the NITRATES analysis (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), we searched for emission on 8 timescales from 0.128s to 16.384s in the interval [-20,+20] seconds around the merger time. We find no evidence for a signal, and derive the following upper limits.
We quote the 5-sigma flux upper limits in the 15-350 keV band, weighted over the GW localization, for four spectral templates (soft, normal, and hard GRB-like templates described in [arXiv:1612.02395], and spectral shape from GRB170817A [arXiv:1710.05446]) and for four time bins.
In units of 10^-7 erg/s/cm^2:
time_bin (s) soft normal hard GRB170817
------------------------------------
0.256 9.33 6.77 6.33 7.22
1.024 4.75 3.45 3.22 3.68
4.096 2.53 1.84 1.72 1.96
16.38 1.54 1.12 1.04 1.19
The upper limits as function of sky position are plotted here, alongside the GW localization:
https://doi.org/10.5281/zenodo.8374493
The solid and dashed lines indicate the 90% and 50% GW contour levels, respectively.
The corresponding fits file can be found here:
https://doi.org/10.5281/zenodo.8374504
GUANO is a fully autonomous, extremely low latency, spacecraft
commanding pipeline designed for targeted recovery of BAT event mode
data around the times of compelling astrophysical events to enable
more sensitive GRB searches.
A live reporting of Swift/BAT event data recovered by GUANO can be
found at: https://www.swift.psu.edu/guano/
View this GCN Circular online at https://gcn.nasa.gov/circulars/34766.
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TITLE: GCN CIRCULAR
NUMBER: 34765
SUBJECT: Fermi Gamma-ray Burst Monitor trigger 717299390/230925076 is not a GRB
DATE: 23/09/25 13:50:25 GMT
FROM: Cori Fletcher at USRA <cfletcher(a)usra.edu>
C. Fletcher (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:
"The Fermi Gamma-ray Burst Monitor (GBM) trigger 717299390/230925076 at
01:49:45.24 UT on 25 September 2023, tentatively classified as a GRB, is in fact
not due to a GRB. This trigger is likely due to particles."
View this GCN Circular online at https://gcn.nasa.gov/circulars/34765.
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