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"32485 results found.
- EP260430a: LCO optical upper limits
- GRB 260430A / EP260430a: COLIBRÍ optical upper limit
- Fermi GRB 260429A: Global MASTER-Net observations report
- EP260430a: Global MASTER-Net observations report
- GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
- GRB 260428A: GECAM-B detection of a possible long duration Type I burst
- IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
- GRB 260428A: AstroSat CZTI detection
- Fermi GRB 260428A: Global MASTER-Net observations report
- EP260416a: Mondy and Terskol optical upper limits
- GRB 260424B: Glowbug gamma-ray detection of a short burst
- GRB 260424B: COLIBRÍ optical upper limit
- Konus-Wind detection of GRB 260424B
- Fermi-LAT Gamma-ray Observations of IceCube-260425A
- EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
- IPN triangulation of GRB 260424B (short)
- IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
- GRB 260401A: cubesat Avion detection
- EP260321a: Upper limits from ATCA radio observations
- GRB 260421B: Kilonova-Catcher optical afterglow detection
- GRB 260421B: Insight-HXMT/HE detection
- The EP-WXT trigger 01709258652: Mondy optical observations
- GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
- EP260416a: Mondy optical observations
- GRB 260421B: SVOM/ECLAIRs refined analysis
- GRB 260421B: 3.6m DOT optical observation
- EP260416a: ZTSh R band observations
- EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
- EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
- GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
- GRB 260419A: AstroSat CZTI detection
- GRB 260421B: SVOM/GRM observation
- GRB260421B: J band upper limit by SYSU 80cm infrared telescope
- GRB 260421B: EP-FXT follow-up observation
- GOTO26djh/AT2026jpw: ATCA radio detection
- GRB 260421B: J-band upper limit with WINTER
- GRB 260421B: LCO optical counterpart detection
- GRB 260421B: Fermi GBM Observation
- GRB 260421A: AstroSat CZTI detection
- GOTO26djh/AT2026jpw: radio detection at 15GHz
- GRB 260412A: SVOM/ECLAIRs refined analysis
- GRB 260421B: SVOM/VT optical observations
- EP260416a: J band upper limit by SYSU 80cm infrared telescope
- GRB 260310A: Late-time Chandra X-ray Detection
- GRB 260418A: Insight-HXMT/HE detection
- EP260416a: 1.3m DFOT optical observation
- GRB 260415A: CALET Gamma-Ray Burst Monitor detection
- GRB 260415B: CALET Gamma-Ray Burst Monitor detection
- Fermi GRB 260421C: Global MASTER-Net observations report
- GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
- Fermi GRB 260421B: Global MASTER-Net observations report
- GRB 260421B: BOOTES-7 early optical afterglow detection
- GRB 260421B: LCO optical afterglow confirmation
- GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
- GRB 260421B: TRT optical counterpart detection
- GRB 260421B: SVOM detection of a long burst
- Fermi GRB 260421A: Global MASTER-Net observations report
- EP260321a: VLA radio follow-up
- GRB 260412A: LCOGT Optical Upper Limits
- EP260416a: Optical follow-up observations with Kinder
- GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
- EP-WXT trigger 01709260303: KAIT optical observations
- EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
- GRB 260417A: SVOM/GRM observation
- EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
- EP260417a: GROWTH-India Telescope optical upper limit
- Fermi GRB 260417B: Global MASTER-Net observations report
- EP260417b: GROWTH-India Telescope optical upper limit
- EP260416a: Ondrejov D50 optical detection
- EP260416a: VLT/FORS2 spectroscopic redshift confirmation
- EP260417a: Global MASTER-Net observations report
- EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
- EP260416a: NOT tentative spectroscopic redshift of z =1.909
- EP260416a: GMG Optical Observation
- Fermi GRB 260417A: Global MASTER-Net observations report
- Konus-Wind detection of GRB 260411B
- GRB 260417A: AstroSat CZTI detection
- IPN triangulation of GRB 260411B
- EP260416a: LCO observations confirm end of flaring phase
- EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
- EP260417a: TRT optical counterpart detection
- EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
- EP-WXT trigger 01709259586: KAIT optical observations
- EP260416a: KAIT optical upper limit
- GRB 260414A: Insight-HXMT/HE detection
- EP260416a: COLIBRÍ confirmation of the optical rebrightening
- EP260416a: WFST optical observations and rebrightening
- GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
- EP260416a: SVOM/VT optical observation
- GOTO26djh/AT2026jpw: SVOM/VT optical observation
- GRB 260415B: Glowbug gamma-ray detection
- GRB 260411B: Glowbug gamma-ray detection
- GRB 260415A: Insight-HXMT/HE detection
- EP260416a: COLIBRÍ optical counterpart candidate
- COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
- EP260416a: Global MASTER-Net observations report
- GOTO26djh/AT2026jpw : MASTER OT observation
- GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
- GOTO26djh/AT2026jpw transient: SAO RAS optical observations