TITLE: GCN CIRCULAR
NUMBER: 36344
SUBJECT: LIGO/Virgo/KAGRA S240428dr: Updated Sky localization
DATE: 24/04/29 13:30:56 GMT
FROM: Divyajyoti NLN <divyajyoti.nln(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 Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S240428dr (GCN Circular ***CITE ORIGINAL GCN ID, …
[View More]e.g. 25012***). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page:
https://gracedb.ligo.org/superevents/S240428dr
For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 186 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 831 +/- 145 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/36344.
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TITLE: GCN CIRCULAR
NUMBER: 36343
SUBJECT: LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet ToO observations
DATE: 24/04/29 12:29:25 GMT
FROM: Mankeun Jeong <jmk5040(a)gmail.com>
Mankeun Jeong, Myungshin Im, Gregory S. H. Paek, Seo-Won Chang, Seong-Kook Lee (SNU/SNU ARC), Dong-Jin Kim and Chung-Uk Lee (KASI), on behalf of the GECKO team
We report on the observations conducted by the GECKO team using the three Korea Microlensing Telescope Network (KMTNet) 1.6-m telescopes equipped with …
[View More]4 square degree cameras in response to the LIGO/Virgo/KAGRA S240422ed trigger (GCN 36236). Observations commenced on 2024-04-23 00:54:26 UTC, approximately 3.3 hours after the event, utilizing the Johnson-Coursin R band. Our efforts resulted in coverage of 232 sq. degrees of the localization area. The spatial extent of our observations is detailed in TreasureMap (Wyatt et al. 2020; https://treasuremap.space/alerts?graceids=S240422ed).
For each field, we conducted 4×120 sec exposures, revisiting each target field twice. This strategy achieved a depth between 20.4 and 22.2 AB magnitudes with a 5-sigma detection limit for each visit. For the subtraction process, we utilized template images from the KMTNet Synoptic Survey of Southern Sky (KS4), taken before the gravitational wave detection. The overlapping area between our observed regions and the KS4 templates is approximately 60 sq. degrees. In areas without KS4 coverage, we employed PS1 templates to facilitate transient searches around GLADE+ galaxies (Dalya et al., 2022).
Additional measures included cross-matching our candidate detections with the Minor Planet Center database to identify known asteroids and exclude recognized sources. The integration of machine learning algorithms is also underway to refine the detection process. Data reduction and analysis are ongoing, and further updates will be provided as new results become available.
Gravitational-wave EM Counterpart Korean Observatory (GECKO; Im et al. 2023, Proceedings of IAU Symp. Vol. 363, pp. 207.; Paek et al. 2024, The Astrophysical Journal, Vol. 960, Number 2, 113.) is a network of 0.5m to 1m class telescopes worldwide. KMTNet is operated by the Korea Astronomy and Space Science Institute. We thank the KMTNet operators for their support for the KMTNet observations.
View this GCN Circular online at https://gcn.nasa.gov/circulars/36343.
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TITLE: GCN CIRCULAR
NUMBER: 36342
SUBJECT: LIGO/Virgo/KAGRA S240429an: Retraction of GW compact binary merger candidate
DATE: 24/04/29 06:18:54 GMT
FROM: Cam Sprague <cspragu2(a)nd.edu>
SUBJECT: LIGO/Virgo/KAGRA S240429an: Retraction of GW compact binary merger candidate
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
The trigger S240429an is no longer considered to be a candidate of interest. This candidate was initially …
[View More]identified by one or more early-warning analyses by matching partial signal templates to the data. Analysis of additional data up to the putative merger time, with full signal templates, did not make a significant detection, indicating that the initial candidate was likely due to transient noise.
View this GCN Circular online at https://gcn.nasa.gov/circulars/36342.
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TITLE: GCN CIRCULAR
NUMBER: 36341
SUBJECT: LIGO/Virgo/KAGRA S240422ed: ENGRAVE VLT/XShooter spectroscopy of the host galaxy of J-GEM24a
DATE: 24/04/29 00:56:26 GMT
FROM: katemaguire101(a)gmail.com
K. Maguire (Trinity College Dublin), A. Levan (Radboud), F. Fortin (IRAP, Toulouse) report on behalf of the ENGRAVE collaboration:
We obtained a VLT+XShooter spectrum of the potential host galaxy of J-GEM24a (Takahashi et al., GCN 36333), GL080850-243120, suggested as a potential …
[View More]counterpart to S240422ed (LVK, GCN 36236), on UT 2024-04-28. Multiple host lines (Ca II H&K, Na I D) are identified at a redshift of 0.055.
This redshift is inconsistent with the S240422ed GW distance estimate at the coordinates of J-GEM24a of 170 +/-42 Mpc at the 2 sigma level.
We thank the ESO observing staff and observers at Paranal who allowed us to undertake these observations. Based on observations collected by the ENGRAVE collaboration at the European Southern Observatory under ESO programme 108.22JF.021.
View this GCN Circular online at https://gcn.nasa.gov/circulars/36341.
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TITLE: GCN CIRCULAR
NUMBER: 36340
SUBJECT: LIGO/Virgo/KAGRA S240428dr: Identification of a GW compact binary merger candidate
DATE: 24/04/29 00:21:43 GMT
FROM: Quynh Lan Nguyen <lnguyen3(a)nd.edu>
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
We identified the compact binary merger candidate S240428dr during real-time processing of data from LIGO Hanford Observatory (H1) and Virgo Observatory (V1) at 2024-04-28 22:54:40.077 UTC (…
[View More]GPS time: 1398380098.077). The candidate was found by the GstLAL [1] analysis pipeline.
S240428dr is an event of interest because its false alarm rate, as estimated by the online analysis, is 2.1e-14 Hz, or about one in 1e6 years. The event's properties can be found at this URL:
https://gracedb.ligo.org/superevents/S240428dr
The classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), NSBH (<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%. [2] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [2] 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 [3], distributed via GCN notice about 29 seconds after the candidate event time.
bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [3], 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 286 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 765 +/- 177 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] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe
[3] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013
View this GCN Circular online at https://gcn.nasa.gov/circulars/36340.
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TITLE: GCN CIRCULAR
NUMBER: 36339
SUBJECT: Fermi GRB 240428A: Global MASTER-Net observations report
DATE: 24/04/28 17:45:56 GMT
FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru>
V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik, D. Vlasenko,
G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij
(Lomonosov Moscow State University, SAI, …
[View More]Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile
(Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra
(The Instituto de Astrofisica de Canarias),
D. Buckley
(South African Astronomical Observatory),
O.A. Gress, N.M. Budnev, O.Ershova
(Irkutsk State University, API),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez
(INAOE, Guillermo Haro Astrophysics Observatory),
A. Tlatov, D. Dormidontov
(Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich
(Blagoveschensk Educational State University)
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 240428A ( Fermi GBM team, GCN 36338) errorbox 8392 sec after notice time and 8401 sec after trigger time at 2024-04-28 17:22:55 UT, with upper limit up to 18.5 mag. The observations began at zenith distance = 65 deg. The sun altitude is -17.4 deg.
The galactic latitude b = 75 deg., longitude l = 238 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2438479
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
8431 | 2024-04-28 17:22:55 | MASTER-SAAO | (11h 49m 40.27s , +20d 18m 15.1s) | C | 60 | 18.5 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
View this GCN Circular online at https://gcn.nasa.gov/circulars/36339.
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TITLE: GCN CIRCULAR
NUMBER: 36337
SUBJECT: LIGO/Virgo/KAGRA S240422ed: J-band non-detection of J-GEM24a
DATE: 24/04/28 05:07:32 GMT
FROM: Viraj Karambelkar at Indian Inst of Tech,Bombay <karambelkarvraj21197(a)gmail.com>
LIGO/Virgo/KAGRA S240422ed: J-band non-detection of J-GEM24a
Viraj Karambelkar (Caltech), Mansi Kasliwal (Caltech) on behalf of a larger
collaboration.
We imaged the source J-GEM24a (GCN 36333), reported as a candidate
counterpart to the LVK gravitational wave …
[View More]event S240422ed (GCN 36236) with
the Wide-Field Infrared Camera (WIRC) on the 200-inch Hale Telescope at
Palomar Observatory on UTC 2024-04-28T04:28:38.
We do not detect any source at the location of J-GEM24a, to a depth of J ~
21 mag (AB).
We thank the P200 observer and P200 staff for their cooperation with these
target of opportunity observations.
View this GCN Circular online at https://gcn.nasa.gov/circulars/36337.
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TITLE: GCN CIRCULAR
NUMBER: 36336
SUBJECT: LIGO/Virgo/KAGRA S240422ed: DDOTI Optical Upper Limit for J-GEM24a
DATE: 24/04/27 21:34:23 GMT
FROM: Camila Angulo at UNAM <camiangulo(a)astro.unam.mx>
Camila Angulo Valdez (UNAM), Rosa L. Becerra (UTOV), Alan M. Watson (UNAM), Simone Dichiara (PSU), Eleonora Troja (UTOV), Nat Butler (ASU), William H. Lee (UNAM), Alexander Kutyrev (GSFC/UMD), Tsvetelina Dimitrova (ASU), Keneth Garcia Cifuentes (UNAM), Margarita Pereyra (UNAM) and Océ…
[View More]lotl Lopez (UNAM) report:
Following the detection of a possible near-infrared counterpart J-GEM24a (GCN #36333) to LIGO/Virgo/KAGRA S240422ed (GCN #36236, #36240), we visually inspected the position of this candidate in the images obtained with the DDOTI wide-field imager at the Observatorio Astronomico Nacional on Sierra de San Pedro Martir (http://ddoti.astroscu.unam.mx) on the night of 2024-04-23 UTC (GCN #36256).
We found no significant optical counterparts at the position of this source in our stacked unfiltered image, down to a limiting 5-sigma AB magnitude of w=20.2.
We thank the staff of the Observatorio Astronomico Nacional in San Pedro Martir.
View this GCN Circular online at https://gcn.nasa.gov/circulars/36336.
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