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.
Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
10043 results found.
- GRB 250221A: Assy optical observations
- GRB 250221A: VLT/X-shooter redshift z = 0.768
- GRB 250221A: GRANDMA/TAROT Detection
- GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
- EP250220a: Optical upper limit with Kinder observations
- GRB 250219A: NOT optical observations
- GRB 250219A: SVOM/VT optical counterpart
- GRB 250219A: SVOM detection of a burst
- GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
- SVOM/sb25021804: SVOM detection of a long X-ray transient
- LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
- LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
- GRANDMA/OPD observations of GRB250215A
- EP250215a / GRB 250215A : NOT optical observations
- EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
- EP250207b: Xinglong optical upper limit
- EP250212a: Xinglong optical upper limit
- GRB 250213A: SVOM detection of a burst
- GRB 250205A: VIRT Optical Upper Limit
- GRB 250210A: GRBAlpha detection
- GRB 250205A / EP250205A: radio detection with the VLA
- LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
- LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
- GRB 241128A: VIRT Optical Upper Limit
- EP250207b: Gemini GMOS-N z-band observations
- GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
- GRB 250204B: GRBAlpha detection
- GRB 250204A: GRBAlpha detection
- LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
- GRB 250129A: GRANDMA Continued Afterglow Detection
- GRB 250206A: EIRSAT-1 GMOD Detection
- LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
- LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
- LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
- LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
- GRB 250129A: Continued AbAO and Mondy optical observations
- LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
- GRB 250207B: MAXI/GSC detection
- The EP-WXT trigger 01709131290 is likely a flaring star
- LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
- EP250205a/GRB 250205A: correction to the source localization
- EP250205a/GRB 250205A: Einstein Probe observation
- GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
- GRB 250205A: SVOM detection of a burst
- GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
- GRB 250202C: GRBAlpha detection
- GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
- LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
- GRB 250129A: NOT optical observations of continuining activity
- GRB 250129A: GRANDMA/TAROT optical afterglow detection
- GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
- GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
- GRB 250127A: CrAO and Terskol optical upper limits
- GRB 250128B: NOT optical upper limit
- GRB 250129A: OHP/T193 optical and spectroscopy observations
- GRB 250129A: NOT optical observations and redshift confirmation
- GRB 250129A: VLT/X-shooter redshift of z = 2.151
- GRB 250127A: EP-FXT afterglow detection
- GRB 241223A: cubesat Avion detection
- GRB 250126A: CALET Gamma-Ray Burst Monitor detection
- GRB 250126A: MAXI/GSC detection
- EP250125a: Optical upper limit with Kinder observations
- GRB 250121A: CALET Gamma-Ray Burst Monitor detection
- EP250108a: AbAO, CMO and Terskol optical upper limits
- GRB 250114A: Swift-BAT refined analysis
- LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
- EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
- EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
- GRB 241217A / EP241217B: radio detection with the VLA
- Swift Trigger 1282245 is not a GRB
- GRB 250116A: Fermi-LAT detection
- GRB 250114B: SVOM/VT upper limit
- GRB 250114B : MITSuME Akeno optical afterglow candidate detection
- GRB 250114A: GRANDMA/TAROT optical afterglow detection
- GRB 250114A: VLT/X-shooter spectroscopic redshift z = 4.732
- Swift GRB 250114A: Global MASTER-Net observations report
- GRB 250114A: Swift detection of a burst with an optical counterpart
- GRB 250101A: Terskol Zeiss-2000 optical observations
- GRB 250107A: VZLUSAT-2 detection
- EP250109b: optical upper limits with the Liverpool Telescope
- GRB 250109A / EP250109a: GRBAlpha detection
- GRB 250107D: GRBAlpha detection
- EP250111a: Mondy optical observation
- EP250108a: optical follow-up observations with the Liverpool Telescope
- GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
- GRB 250107D: CALET Gamma-Ray Burst Monitor detection
- GRB 250107C: CALET Gamma-Ray Burst Monitor detection
- GRB 250101A: CMO RC-500 optical observations
- EP-WXT trigger EP250109a：Xinglong optical follow-up observations
- EP250109a: Swift/UVOT non-detection
- GRB 250108B: Gemini-North likely redshift z = 2.197
- GRB 250108B: Swift-BAT refined analysis
- GRB 250101A: Terskol K-800 optical observations
- GRB 250108A: Swift/UVOT Upper Limits
- GRB 250108A: NOT optical upper limit
- Swift GRB 250108B: Global MASTER-Net observations report
- GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
- GRB 250108B: Swift/UVOT Upper Limits
- GRB 250108B: Swift detection of a burst
- GRB 241228B: Fermi-LAT detection