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"32533 results found.
- GRB 250809A: LCOGT Optical Upper Limits
- GRB 250702B: Chandra X-ray Detection
- EP250807a: Global MASTER-Net observations report
- Fermi GRB 250808A: Global MASTER-Net observations report
- GRB 250808A: VLT X-shooter candidate counterpart
- GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250808A: Fermi GBM Observation
- GRB 250807A: SVOM/VT optical continued observation
- EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
- GRB 250808A: SVOM detection of a long burst
- Konus-Wind detection of GRB 250807A
- GRB 250807B: Swift/UVOT Detection
- GRB 250807B: Kilonova-Catcher optical afterglow detection
- IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250807A: Swift/UVOT Detection
- GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
- GRB 250806A: SVOM/MXT refined analysis
- GRB 250806A: SVOM/ECLAIRs refined analysis
- EP250807a: NTT z-band optical upper limit
- GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
- GRB 250804B: Insight-HXMT detection
- GRB 250807A: SVOM/GRM observation
- GRB 250807A: AstroSat CZTI detection of bright long burst
- GRB 250806A: NOT z-band upper limit and host galaxy candidate
- GRB 250807B: NTT optical observations
- EP250807a: EP-WXT detection of a fast X-ray transient
- GRB 250807A: SVOM/VT optical observation
- EP250806a: Upper limit from Fermi-GBM Observations
- GRB 250805A: Kilonova-Catcher optical upper limits
- EP250806a:SVOM/VT refined analysis
- GRB 250805A: Swift/UVOT Upper Limits
- GRB 250806A: Swift/UVOT U-band detection
- EP250806a: Liverpool telescope optical upper limit
- GRB 250806A: EP-FXT observation
- EP#01709198415/EP250806a: Swift-XRT observations
- EP250806a: Global MASTER-Net observations report
- EP250802a: EP-FXT follow-up observation
- EP250806a: refined analysis of the EP-WXT and EP-FXT observations
- EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
- EP250806a: SVOM /VT optical candidate
- GRB 250806A: J-band upper limit from WINTER
- GRB 250805A: Swift-BAT refined analysis
- GRB 250806A: KAIT optical upper limit
- GRB 250806A: SVOM/VT refined analysis
- EP250806a: COLIBRÍ optical upper limit
- GRB 250806A: Kilonova-Catcher optical upper limits
- GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250806A: SVOM/VT optical upper limit
- GRB 250805A: SVOM/VT optical counterpart
- GRB 250805A: ESO/VLT observations
- GRB 250805A: TRT optical upper limits
- GRB 250804B: Tiled Swift observations
- EP250802a: additional Liverpool Telescope upper limits
- EP250730a: SVOM/VT optical upper limit
- EP250802a: Liverpool Telescope optical upper limits
- EP250802a: Global MASTER-Net observations report
- EP250802a: GROWTH-India Telescope optical upper limit
- LIGO/Virgo/KAGRA S250802dn: Updated Sky localization
- LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
- GRB 250702B: SMA observations
- LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
- LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
- EP250711a: CrAO and Assy optical observations
- LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
- EP250730a: Global MASTER-Net observations report
- EP250730a: COLIBRÍ optical upper limit
- GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
- LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
- LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
- GRB 250725A: AstroSat CZTI detection
- GRB 250727A: EP-FXT follow-up observation
- GRB 250725A: PRIME near-infrared observations
- LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
- LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
- GRB: Clarification on Gamma-Ray Burst Naming Convention
- GRB 250727A: SVOM/ECLAIRs refined analysis
- EP-WXT trigger 01709195487: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
- GRB 250728A: COLIBRÍ optical upper limit
- GRB 250728A: Fermi GBM Observation
- LIGO/Virgo/KAGRA S250727dc: Updated Sky localization
- GRB 250728A: Swift ToO observations
- GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
- GRB 250727A: AST3-2 Upper limit
- LIGO/Virgo/KAGRA S250727cl: Updated Sky localization
- GRB 250727A: EP-FXT counterpart detection
- GRB250727A: SVOM/VT optical upper limit
- LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
- LIGO/Virgo/KAGRA S250725l: Updated Sky localization
- LIGO/Virgo/KAGRA S250726ak: Updated Sky localization
- LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
- GRB 250725A: Fermi GBM Observation
- LIGO/Virgo/KAGRA S250725j: Updated Sky localization
- GRB 250725A: Swift-BAT refined analysis
- Konus-Wind detection of GRB 250725A
- GRB 250725A: SVOM/GRM observation
- GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
- GRB 250725A: Swift/UVOT Upper Limits