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"21769 results found.
- GRB 250806A: SVOM/VT optical upper limit
- GRB 250806A: SVOM detection of a soft burst
- GRB 250805A: SVOM/VT optical counterpart
- GRB 250804B: Swift-XRT observations
- GRB 250805A: Enhanced Swift-XRT position
- GRB 250805A: TRT optical upper limits
- GRB 250805A: Swift-XRT observations
- GRB 250804B: SVOM/GRM observation of a short burst
- EP250802a: additional Liverpool Telescope upper limits
- EP250730a: SVOM/VT optical upper limit
- EP250802a: Liverpool Telescope optical upper limits
- EP250802a: GROWTH-India Telescope optical upper limit
- LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
- 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: COLIBRÍ optical upper limit
- GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
- LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
- 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 250727A: SVOM/ECLAIRs refined analysis
- GRB 250728A: COLIBRÍ 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
- GRB 250727A: SVOM detection of a burst
- LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
- 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
- GRB 250725A: Fermi-LAT detection
- GRB 250725A: SVOM/VT optical candidate
- GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
- LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
- GRB 250725A: Enhanced Swift-XRT position
- GRB 250725A: Swift detection of a burst
- Swift GRB 250725A: Global MASTER-Net OT detection
- EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
- SVOM J195836+32283 is not a real source
- EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
- SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
- SVOM J195836+32283/sb25072103: NIR observations with WINTER
- GRB 250721A: Swift-XRT observations
- GRB 250717B: SVOM/GRM observation
- The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
- EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
- GRB 250717B: COLIBRÍ optical upper limit
- LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
- Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
- GRB 270713A: Kitab and AbAO Optical Observations
- GRB 250717B: Fermi GBM Observation
- Konus-Wind detection of GRB 250716A
- GRB 250716A: Swift-XRT afterglow detection
- GRB 250716A: GOTO tentative optical counterpart candidate
- GRB 250714A: SVOM/GRM observation
- EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
- GRB 250713A: Mephisto optical upper limits
- GRB 250713A: SVOM/VT optical upper limit
- GRB 250713A: NOT optical upper limits
- GRB 250713A: OHP/T193 upper limit
- GRB 250713A: SVOM/C-GFT upper limit
- GRB 250706B/C: 7DT Follow-up Observations
- GRB 250713A: EP-FXT counterpart detection
- EP250711a: COLIBRÍ continuous optical observations
- GRB 250713A: JinShan optical upper limits
- GRB 250713A: SVOM detection of a long burst
- GRB 250711A: DDOTI Optical Upper Limit
- LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
- EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
- GRB 250711A: SVOM/GRM observation
- EP250711a: NOT optical counterpart candidate
- EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
- EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
- GRB 250704A: GRANDMA observations
- LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
- IceCube-250708A: No Candidates from WINTER
- IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
- EP250704a/GRB 250704B: 10 GHz VLA detection
- IceCube-250706A: No Candidates from WINTER
- IceCube-250706A: No Candidates from the Zwicky Transient Facility
- LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
- EP250704a/GRB250704B : HCT optical and NIR upper limits
- GRB 250706B/C: Konus-Wind analysis of the prompt emission
- GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
- GRB 250704B / EP250704a: Mondy and AbAO optical observations
- GRB 250702F: radio detection with the VLA
- IceCube-250706A: EP-FXT follow-up observations
- GRB 250706B/C: Fermi-LAT detection
- GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations