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').
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"6400 results found.
- GRB 250727A: Swift-XRT observations
- GRB 250725A: Swift-XRT refined Analysis
- GRB 250725A: Fermi GBM Observation
- Konus-Wind detection of GRB 250725A
- GRB 250725A: Fermi-LAT detection
- Swift GRB 250725A: Global MASTER-Net observations report
- SVOM J195836+32283 is not a real source
- GRB 250721A: Fermi GBM Observation
- SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
- GRB 250721A: Swift-XRT observations
- GRB 250717B: Swift-XRT observations
- GRB 250717B: Fermi GBM Observation
- GRB 250716A: Swift-XRT afterglow detection
- GRB 250716A: Fermi GBM Observation
- GRB 250706B/C: 7DT Follow-up Observations
- GRB 250713A: Swift-XRT observations
- GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
- LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
- GRB 250706B/C: Konus-Wind analysis of the prompt emission
- IceCube-250706A: EP-FXT follow-up observations
- Fermi-LAT Gamma-ray Observations of IceCube-250706A
- GRB 250706B/C: Fermi-LAT detection
- GRB 250706B: Swift/UVOT Detection
- EP250702a/ GRB 250702B: NuSTAR X-ray Observations
- GRB 250706A: Swift-XRT refined Analysis
- GRB 250706B: refined SVOM/MXT data analysis
- GRB 250706A: SAO RAS optical observations
- GRB250706B: Swift-XRT counterpart detection
- GRB 250706B: iTelescope optical observations
- GRB 250706A: GROWTH-India Telescope optical upper limit
- GRB 250704B: Swift-XRT refined Analysis
- EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
- GRB 250704B: Swift/UVOT Upper Limits
- GRB 250704A: Swift/UVOT Detection
- EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
- EP250704a / GRB 250704B: JinShan optical observations
- EP250704a / GRB 250704B: SAO RAS optical observations
- EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
- GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
- EP250704a / GRB250704B: Swift-XRT counterpart detection
- GRB 250704A: Swift-XRT afterglow detection
- Konus-Wind detection of GRB 250702F
- GRB 250702F: GROWTH-India Telescope optical observations
- GRB 250702F: optical photometry from Konkoly
- Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
- GRB 250702F: Swift-XRT refined Analysis
- GRB 250702F: Fermi GBM Observation
- GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
- Fermi GBM Triggers 250702B, C, D and E are likely from the same source
- GRB 250702A: Fermi GBM Detection
- LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
- GRB 250628B: Swift-XRT observations
- GRB 250628A: Swift-XRT refined Analysis
- GRB 250625A: Fermi-LAT detection
- GRB 250625A: Swift-XRT refined Analysis
- GRB250625A: Fermi GBM Observation
- GRB 250620B: Fermi GBM Observation
- GRB 250625A: SAO RAS possible optical afterglow
- GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
- GRB250620A: Fermi GBM Observation
- GRB 250619B: Fermi GBM Observation
- GRB250620C: Fermi GBM Observation
- GRB 250506A - SVOM/ECLAIRs Refined analysis
- EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
- GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
- GRB 250617B: Swift-XRT refined Analysis
- GRB 250617B: Fermi GBM Observation
- GRB 250617B: SAO RAS optical observations
- EP#01709178975: Swift-XRT counterpart detection
- GRB 250615A: Swift-XRT refined Analysis
- GRB 250615A: Prompt enhanced Swift-XRT position
- sb25061207: Mephisto optical upper limits
- sb25061218: Swift-XRT observations
- sb25061207: EP-FXT follow-up observation and afterglow candidate
- GRB 250612B: Fermi GBM Observation
- GRB 250612C: Fermi GBM Observation
- sb25061207: Swift-XRT observations
- GRB 250610B: Swift-XRT refined Analysis
- GRB 250610B: Swift/UVOT Detection
- EP250610A: Swift/UVOT Upper limits
- GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
- GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
- GRB 250610B: Swift-XRT counterpart detection
- GRB 250609A: Fermi GBM Observation
- EP250610a: Swift-XRT counterpart detection
- GRB 250605A: Swift-XRT refined Analysis
- GRB 250601A: Fermi GBM Observation
- GRB 250603A: Swift-XRT refined Analysis
- GRB 250602A: Fermi GBM Observation
- GRB 250602A: Fermi-LAT detection
- GRB 250601A: EP-FXT follow-up observation and afterglow candidates
- GRB 250601A: Swift-XRT observations
- EP#01709177494: Swift-XRT counterpart detection of known source
- GRB 250530C: Swift-XRT refined Analysis
- GRB 250530A: Swift-XRT counterpart detection
- GRB 250527C: Swift/UVOT Upper Limits
- EP J1350.0-8622: EP-FXT follow-up observation
- GRB 250527B: Swift-XRT observations
- GRB 250521B: EP-FXT follow-up observation and afterglow candidates
- EP#01709176612: Swift-XRT counterpart detection of flaring star