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"
10363 results found.
- Fermi GRB 250407A: Global MASTER-Net observations report
- GRB 250407A: SRG/ART-XC afterglow detection
- LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
- Konus-Wind detection of GRB 250406B (short/hard)
- GRB 250406A: AstroSat CZTI detection
- Fermi trigger No 765663719: Global MASTER-Net observations report
- Fermi GRB 250406A: Global MASTER-Net observations report
- EP250404a / GRB 250404A: Montarrenti Observatory optical observations
- EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
- Konus-Wind detection of GRB 250404A / EP250404a
- EP250404a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
- GRB 250404B: AstroSat CZTI detection of a short burst
- GRB 250403A: AstroSat CZTI detection
- EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
- EP250404a: LCO optical counterpart detection
- Fermi GRB 250404A: Global MASTER-Net observations report
- EP250404a: Xinglong decaying optical counterpart
- EP250404a: Global MASTER-Net observations report
- EP250404a: AKO Optical Afterglow Detection
- EP250404a: LAST detection of optical counterpart
- GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
- EP250404a: Mephisto multi-band optical detection
- EP250321A: J band upper limit by SYSU 80cm telescope
- EP250404a: BOOTES-4/JGT optical afterglow detection
- EP250404a: Nanshan/HMT optical counterpart detection
- EP250404a: Einstein Probe detection of an X-ray transient
- IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
- GRB 250402A: EP-FXT afterglow detection
- GRB 250322A: 10 GHz VLA radio upper limits
- GRB 250403A: GOTO optical counterpart follow-up observations
- GRB 250403A : SVOM detection of a burst
- GRB 250402B: AstroSat CZTI detection of a short burst
- GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
- GRB 250331D: Fermi GBM observation
- GRB 250328A: AbAO AS-32 Optical Observations
- GRB 250322B: GRBAlpha detection
- LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
- Fermi GRB 250331D: Global MASTER-Net observations report
- GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
- Konus-Wind detection of GRB 250327B
- LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
- LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
- Fermi-LAT gamma-ray observations of IceCube-250330A
- GRB 250331A: MAXI/GSC detection
- Fermi GRB 250330B: Global MASTER-Net observations report
- IceCube Alert 250330.35: Global MASTER-Net observations report
- GRB 250329B: Swift-XRT afterglow detection
- Swift GRB250330.26: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
- GRB 250329A: SVOM detection of a burst
- LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
- EP250302a: SPI-ACS/INTEGRAL Upper Limit
- GRB 250327B: Swift-XRT detection of the X-ray afterglow
- GRB 250327A: Swift-XRT refined Analysis
- FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
- Konus-Wind detection of GRB 250322A (short)
- IPN triangulation of GRB 250322B
- Swift follow-up observations of FRB250316A and EP J120944.2+585060
- GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
- GRB 250322A: AstroSat CZTI detection of a short burst
- GRB 250322B: AstroSat CZTI detection of a bright long burst
- GRB 250322A: NOT optical upper limits
- GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
- EP250321a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
- GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
- GRB 250320B: Fermi GBM Observation
- GRB 250320B: Fermi-LAT detection
- GRB 250320B: AstroSat CZTI detection
- Swift GRB 250321A: Global MASTER-Net observations report
- Fermi GRB 250321A: Global MASTER-Net observations report
- EP250226a/GRB 250226A: KAIT optical observations
- GRB 250320B: Fermi GBM Final Real-time Localization
- GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
- GRB 250320A: Fermi GBM Final Real-time Localization
- Fermi GRB 250319B: Global MASTER-Net observations report
- GRB 250317C: AstroSat CZTI detection
- GRB 250316A: Swift-XRT afterglow detection
- Fermi GRB 250316A: Global MASTER-Net observations report
- GRB 250314A: EP-FXT afterglow detection
- EP250315a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250312B: GRBAlpha detection
- EP250315a: Einstein Probe detection of an X-ray transient
- GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
- GRB 250314A: NOT near-infrared candidate counterpart
- GRB 250313A: Fermi GBM Detection
- GRB 250312B: Fermi GBM Observation
- GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
- Konus-Wind detection of GRB 250313A
- Konus-Wind detection of GRB 250308A
- GRB 250314A: SVOM detection of a burst
- GRB 250313A: AstroSat CZTI detection of a bright long burst
- IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
- GRB 250313A: Fermi-LAT detection
- GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
- Fermi GRB 250313A: Global MASTER-Net observations report
- ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
- EP250302a: Chandra X-ray Detection
- GRB 250312A: Swift-XRT refined Analysis