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"
2730 results found.
- EP250512a: Global MASTER-Net observations report
- Fermi GRB 250510C: Global MASTER-Net observations report
- Fermi GRB 250510B: Global MASTER-Net observations report
- IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
- EP250508a: Global MASTER-Net observations report
- EP250508a: Einstein Probe detection of an X-ray transient
- IceCube Alert 250506.59: Global MASTER-Net observations report
- GRB 250504A: Swift-XRT refined Analysis
- EP250428b: SAO RAS optical upper limit
- EP250427a / GRB 250427A: LCO optical counterpart detection
- GRB 250424A: BlackGEM optical afterglow detection
- IceCube-250421A: DDOTI Detection of the LAST Candidate
- IceCube Alert 250421.71: Global MASTER-Net observations report
- IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250419A: MASTER optical afterglow observation
- Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
- EP250416a: Global MASTER-Net observations report
- EP250404a: Nanshan 0.43m Telescope optical observatios
- Fermi trigger No 766173972: Global MASTER-Net observations report
- GRB 250407A: KAIT Optical Afterglow Candidate
- IceCube-250406A: No candidates from the Zwicky Transient Facility
- GRB 250407A: Swift-XRT afterglow detection
- Fermi GRB 250407A: Global MASTER-Net observations report
- IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
- Fermi GRB 250406A: Global MASTER-Net observations report
- GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
- Fermi GRB 250404A: Global MASTER-Net observations report
- EP250404a: Xinglong decaying optical counterpart
- GRB 250404A: Fermi GBM Detection
- EP250404a: AKO Optical Afterglow Detection
- GRB 250331B Swift-BAT refined analysis
- Fermi GRB 250331E: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
- Fermi GRB 250330A: Global MASTER-Net observations report
- GRB 250330A: Prompt Swift-XRT position
- Swift GRB250330.26: Global MASTER-Net observations report
- GRB 250327B: ALMA detection
- GRB 250327B: VLA detection
- GRB 250329A: Fading optical counterpart detection by LCO.
- GRB 250327B: SVOM/VT optically bright counterpart
- GRB 250327B: SAO RAS optical candidate
- GRB 250327A: Fermi GBM observation
- GRB 250321C: Fermi GBM Final Real-time Localization
- GRB 250317B: Mondy AZT-33IK Continued Optical Observations
- FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
- GRB 250317D: EIRSAT-1 GMOD Detection
- EP250315a: Einstein Probe detection of an X-ray transient
- GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
- Fermi trigger No 763581136: Global MASTER-Net observations report
- Fermi GRB 250313A: Global MASTER-Net observations report
- GRB 250313A: Fermi GBM Final Real-time Localization
- EP250302a: Chandra X-ray Detection
- Fermi trigger No 763509110: Global MASTER-Net observations report
- GRB 250311A: Swift-XRT observations
- EP250311a: Global MASTER-Net observations report
- GRB 250225B: Swift-BAT refined analysis
- GRB 250309B / AT2025dws: SAO RAS optical observations
- Fermi GRB 250309A: Global MASTER-Net observations report
- GRB250309B: One candidate counterpart from the Zwicky Transient Facility
- IceCube-250309A: No candidates from the Zwicky Transient Facility
- IceCube Alert 250309.32: Global MASTER-Net observations report
- Fermi trigger No 762963055: Global MASTER-Net observations report
- Fermi GRB 250305A: Global MASTER-Net observations report
- IPN triangulation of GRB 250222A
- EP250302a : GIT optical follow-up
- Fermi GRB 250302A: Global MASTER-Net observations report
- EP250302a: Nanshan/HMT optical counterpart detection
- LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
- EP250227a: Global MASTER-Net observations report
- EP250227a: Optical upper limits with Kinder observations
- GRB 250205A / EP250205A: further radio observations with the VLA
- Fermi GRB 250226A: Global MASTER-Net observations report
- Fermi GRB 250225A: Global MASTER-Net observations report
- The EP-WXT trigger 01709131882 is likely a flaring star
- EP250223a: LCO detection of the afterglow
- Konus-Wind detection of GRB 250217C (short)
- Fermi GRB 250217A: Global MASTER-Net observations report
- GRB 250217A: Fermi GBM Final Real-time Localization
- Fermi GRB 250216A: Global MASTER-Net observations report
- EP250215a: Global MASTER-Net observations report
- EP250207b: Xinglong optical upper limit
- EP250212a: Global MASTER-Net observations report
- Fermi trigger No 760945500: Global MASTER-Net observations report
- GRB 250211A: SVOM trigger sb25021103 is not a GRB
- GRB 250212A: Fermi GBM Final Real-time Localization
- IceCube-250207A: One candidate from the Zwicky Transient Facility
- EP250207b: Global MASTER-Net observations report
- GRB 241128A: VIRT Optical Upper Limit
- EP250207b: a new X-ray transient detected by Einstein Probe
- 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: GECKO Observation with 7DT and KMTNet
- LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
- IceCube-250203A: No transient candidates from the Zwicky Transient Facility
- LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
- EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
- IPN triangulation of GRB 250201A
- GRB 250202B: Fermi GBM Detection
- The EP-WXT trigger 01709131153 is not a real source
- GRB 250128B: VLA radio upper limit