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"
24595 results found.
- EP250220a: Liverpool Telescope upper limits
- GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
- GRB 250221A: REM optical/NIR afterglow detection
- IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
- GRB 250221A: Enhanced Swift-XRT position
- EP250220a: 1.6m Mephisto observations
- EP250220a: Liverpool Telescope optical upper limits
- EP250220a: Optical upper limit with Kinder observations
- SVOM trigger sb25022102 is not an astrophysical event
- GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
- GRB 250221A: Swift detection of a burst with an optical counterpart
- Swift GRB250221.15: Global MASTER-Net OT detection
- EP250220a: Xinglong optical upper limit
- GRB 250219A: Swift/UVOT Upper Limits
- GRB 250219A: OHP/T193 optical upper limit
- GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
- GRB 250219A: 1.6m Mephisto optical upper limits
- GRB 250219A: Swift-XRT observations
- LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
- Konus-Wind detection of GRB 250215A / EP250215a
- SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
- GRB 250217C: Swift-XRT observations
- SVOM/sb25021804: QSO variability in Liverpool Telescope observations
- GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
- GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
- GRB 250217C: SVOM/GRM observation
- Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
- SVOM/sb25021804: SVOM detection of a long X-ray transient
- GRB 250213A: Swift-XRT observations
- GRB 250216A: AstroSat CZTI detection
- GRB 250217C: AstroSat CZTI detection of a short burst
- IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
- GRANDMA/OPD observations of GRB250215A
- GRB 250215A / EP250215a: LCO detection of the afterglow
- GRB 250215A: Swift/UVOT Upper Limits
- GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
- GRB 250215A: Fermi GBM Observation
- GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
- GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
- GRB 250215A: Swift-XRT refined Analysis
- GRB 250215A: SVOM/GRM observation
- EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
- EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
- EP250207b: Xinglong optical upper limit
- EP250212a: Xinglong optical upper limit
- LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
- EP250212a: Global MASTER-Net observations report
- GRB 250205A: VIRT Optical Upper Limit
- GRB 250205A: Leavitt Observatory optical upper limit
- EP250207B: Chandra localization of the X-ray counterpart
- EP250212a: Liverpool Telescope optical upper limits
- GRB250101A: Radio upper limits from GMRT observations
- EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
- EP250207B: GTC z-band Observations
- Fermi GRB 250212A: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
- GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
- Fermi trigger No 760945500: Global MASTER-Net observations report
- EP250207b: NOT optical counterpart candidate
- GRB 250211B: A long GRB detected by INTEGRAL
- LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
- LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
- LIGO/Virgo/KAGRA S250211be: Updated Sky localization
- GRB 250207A: Fermi GBM Observation
- GRB 250206A: Fermi GBM Observation
- GRB 250205A / EP250205A: radio detection with the VLA
- EP250207b: Tentative z-band brightening source
- LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
- Konus-Wind detection of GRB 250206A
- GRB 250210A: SVOM/GRM observation of a long burst
- EP250207b: Liverpool Telescope possible optical counterpart
- LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
- LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
- GRB 250207A: Skynet optical afterglow observations
- GRB 241128A: VIRT Optical Upper Limit
- EP250207b: Gemini GMOS-N z-band observations
- EP250207A: Upper limits from Fermi-GBM Observations
- EP250207b: a new X-ray transient detected by Einstein Probe
- GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
- LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
- IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
- LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
- LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
- Fermi-LAT Gamma-ray Observations of IceCube-250207A
- GRB 250207A: 1.3m DFOT Optical observations
- LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
- GRB 250206A: Swift-XRT observations
- GRB 250129A: GRANDMA Continued Afterglow Detection
- GRB 250207A: Swift-BAT refined analysis
- LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
- LIGO/Virgo/KAGRA S250207bg: Updated NED Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
- LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
- GRB 250205A: 1.3m DFOT optical upper limit
- LIGO/Virgo/KAGRA S250118az: Updated Sky localization
- LIGO/Virgo/KAGRA S250208ad: Updated Sky localization
- GRB 250206A: EIRSAT-1 GMOD Detection