GCN Circulars
GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search
To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.
Advanced Search Examples (click to copy):
subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
- GRB 250706B/C: Insight-HXMT detection
- EP/WXT 01709181970: GOTO observations confirm stellar variability
- EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
- EP250704a/GRB 250704B: 10 GHz VLA detection
- The EP-WXT trigger 01709181970 is likely a flaring star
- GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
- LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
- IceCube-250706A: No Candidates from WINTER
- IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
- IceCube-250706A: No Candidates from the Zwicky Transient Facility
- IceCube-250708A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 250704B / EP250704a: VLA radio detection
- Fermi GRB 250708A: Global MASTER-Net observations report
- IceCube Alert 250708.59: Global MASTER-Net observations report
- IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
- LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
- LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
- LIGO/Virgo/KAGRA S250702n: Updated Sky localization
- LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
- EP250704a/GRB250704B : HCT optical and NIR upper limits
- LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
- GRB 250708A: Fermi GBM Final Real-time Localization
- GRB 250706B/C: Konus-Wind analysis of the prompt emission
- GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
- GRB 250704B: CALET Gamma-Ray Burst Monitor detection
- GRB 250704B / EP250704a: Mondy and AbAO optical observations
- GRB 250702F: radio detection with the VLA
- GRB 250706B/C: VLT/X-shooter redshift z = 0.942
- IceCube-250706A: EP-FXT follow-up observations
- Fermi-LAT Gamma-ray Observations of IceCube-250706A
- GRB 250706B/C: Fermi-LAT detection
- IceCube Alert 250706.55: Global MASTER-Net observations report
- GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
- EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
- GRB 250706B: Swift/UVOT Detection
- EP250702a/ GRB 250702B: NuSTAR X-ray Observations
- GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
- GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
- GRB 250702F: GRANDMA observations
- GRB 250706A: Swift-XRT refined Analysis
- GRB 250706B: refined SVOM/MXT data analysis
- GRB 250706A: Swift/UVOT Upper Limits
- GRB 250706B: REM optical observations
- GRB 250706A: REM optical/NIR observations
- EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
- IceCube-250416A: DDOTI Optical Upper Limit
- IceCube-250706A: COLIBRÍ optical upper limits
- Swift GRB 250706A: Global MASTER-Net observations report
- GRB 250706A: JinShan optical upper limits
- GRB 250706A: SAO RAS optical observations
- EP250704A: NOWT Detection
- GRB 250706A: SVOM/C-GFT upper limit in eary phase
- The EP-WXT trigger 01709181580 is likely a flaring star
- GRB250706B: Swift-XRT counterpart detection
- GRB 250706B: iTelescope optical observations
- IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
- EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
- GRB 250706B: SVOM/VT optical observation
- GRB 250706B: TRT bright optical counterpart detection
- GRB 250706A: GROWTH-India Telescope optical upper limit
- GRB 250706B: SVOM detection of a long burst
- GRB 250706A: Swift detection of a burst
- GRB 250704B: Swift-XRT refined Analysis
- GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
- EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
- GRB 250703A: EIRSAT-1 GMOD Detection
- EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
- GRB 250704B: Swift/UVOT Upper Limits
- GRB 250704A: Swift/UVOT Detection
- LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
- Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
- GRB 250704B: Insight-HXMT detection
- Konus-Wind detection of GRB 250703A
- IPN triangulation of GRB 250703A
- EP250704a/GRB 250704B: GSP observations of the optical counterpart
- EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
- GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
- Konus-Wind detection of short/hard GRB 250704B/ EP250704a
- EP250704a / GRB 250704B: NOT observations of the optical afterglow
- EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
- GRB 250702F: Kilonova-Catcher optical afterglow detection
- GRB 250702F: Monte Agliale Observatory optical observations
- GRB250702F: afterglow detected by joint EP-ZTF shadowing program
- EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
- EP250704a / GRB 250704B: JinShan optical observations
- GRB 250704A: SVOM/VT optical observation
- EP250704a / GRB 250704B: SAO RAS optical observations
- EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
- GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
- EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
- LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
- EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
- EP 250704a: BOOTES-5 optical detection
- EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
- LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
- GRB 250702A: Insight-HXMT detection
- GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
- GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
- EP250704a / GRB250704B: Swift-XRT counterpart detection
- GRB 250704A: Swift-XRT afterglow detection