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"
3820 results found.
- GRB 250213A: Swift-XRT observations
- Fermi GRB 250217A: Global MASTER-Net observations report
- EP250215a: Global MASTER-Net observations report
- Fermi trigger No 761206993: Global MASTER-Net observations report
- EP250212a: Xinglong optical upper limit
- EP250207b: VLA radio upper limits
- Fermi GRB 250212A: Global MASTER-Net observations report
- Fermi trigger No 760945500: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
- LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II
- GRB 241128A: VIRT Optical Upper Limit
- GRB 250210A: AstroSat CZTI detection
- GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
- Fermi GRB 250210A: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
- IceCube Alert 250207.09: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
- LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
- LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
- EP250207a: EP-WXT detection and XRT follow-up observation
- LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
- LIGO/Virgo/KAGRA S250207bg: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
- GRB 250207B: MAXI/GSC detection
- GRB 250202B: Fermi GBM Detection
- The EP-WXT trigger 01709131196 is likely a flaring star
- Swift GRB250129A: MASTER 4 days observations report
- GRB 250129A: optical photometry from Konkoly
- GRB 250128B: VLA possible radio detection
- GRB 250129A: AKO 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 250128B: VLA radio upper limit
- GRB 250129A: Skynet optical observations
- GRB 250128B: Gemini-North optical extended source detection
- GRB 250128B: TNG optical upper limit
- GRB 250129A: REM optical/NIR afterglow detection
- GRB 250129A: Early afterglow detection by LCO.
- GRB 250129A: LCO optical observations
- GRB 250129A: GOTO optical observations show brightening afterglow
- Swift GRB 250129A: Global MASTER-Net observations report
- The EP-WXT trigger 01709131085 is likely a flaring star
- Fermi GRB 250128B: Global MASTER-Net observations report
- Swift GRB 250129A: Global MASTER-Net OT detection
- GRB 250127A: EP-FXT afterglow detection
- Fermi GRB 250127B: Global MASTER-Net observations report
- GRB 250126A: MAXI/GSC detection
- GECAM-A detection of a bright burst from SGR 1E1841-045
- Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
- IPN triangulation of a bright burst from SGR 1E1841-045
- IPN triangulation of GRB 250119B
- EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
- LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
- GRB 250116A: GECAM-B detection of a long burst
- GRB 250114B: OHP/T193 optical upper limit
- EP250111a: Global MASTER-Net observations report
- EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
- GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
- IPN triangulation of GRB 250107D (short/hard)
- EP250109a: SVOM/VT optical candidate
- GRB 250106A: SVOM detection of a long burst
- Fermi trigger No 757753930: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
- Swift GRB 250103B: Global MASTER-Net observations report
- EP241231b and EP250101a: EP-WXT detection of two X-ray transients
- Fermi GRB 250101B: Global MASTER-Net observations report
- GRB 250101A: SAO RAS optical observations
- LIGO/Virgo/KAGRA S241231bg: Identification of a GW compact binary merger candidate
- GRB 241228B: SAO RAS optical observations
- GRB 241229B: CrAO ZTSh possible optical counterpart of SVOM/VT confirmation
- IceCube-Cascade 241228A: Upper limits from a search for additional neutrino events in IceCube
- GRB 241229A: EP-FXT afterglow candidates
- Fermi Gamma-ray Burst Monitor trigger 757207662/241229978 (GRB 241229C) is not a GRB
- GRB 241229C: Fermi GBM Final Real-time Localization
- GRB 241229B: Fermi GBM Observation
- GRB 241229B: NUTTelA-TAO / BSTI Optical Limits
- Swift GRB 241229B: Global MASTER-Net observations report
- GRB 241229A: GOTO optical upper limits
- GRB 241228B: VLT/X-shooter redshift of z = 2.674
- GRB 241229B: Fermi GBM Final Real-time Localization
- GRB 241223A: GRBAlpha detection
- LIGO/Virgo/KAGRA S241225v: Identification of a GW compact binary merger candidate
- GRB 241029A: AbAO AS-32 optical observations
- Fermi trigger No 756678579: Global MASTER-Net observations report
- IceCube Alert 241224.30: Global MASTER-Net observations report
- Fermi Gamma-ray Burst Monitor trigger 756678579 / 241223854 is not a GRB
- Fermi trigger No 756447119: Global MASTER-Net observations report
- Fermi GRB 241221A: Global MASTER-Net observations report
- EP241217a: Liverpool Telescope optical upper limit
- GRB 241217A/EP241217B: Fermi-GBM Sub-Threshold Detection
- GRB 241218A: NUTTelA-TAO / BSTI Optical Limits
- EP241119a: 7DT Optical upper limits
- GRB 241213A: REM optical/NIR upper limits
- GRB 241207A: TSHAO Zeiss-1000 optical observations
- GRB 241129A: Fermi GBM Observation
- GRB 241209A: Swift-XRT refined Analysis
- LIGO/Virgo/KAGRA S241210cw: Identification of a GW compact binary merger candidate
- EP241208a: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S241210d: Identification of a GW compact binary merger candidate
- Fermi GRB 241209E: Global MASTER-Net observations report