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').
- Konus-Wind detection of GRB 241228A
- GRB 241229A: EP-FXT afterglow candidates
- EP240702a: 7DT Optical upper limits
- GRB 240606B: 7DT Optical upper limits
- Fermi trigger No 757231333: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S241230bd: Identification of a GW compact binary merger candidate
- GRB 241229B: Swift-BAT refined analysis
- LIGO/Virgo/KAGRA S241225v: Updated Sky localization
- LIGO/Virgo/KAGRA S241225c: Updated Sky localization and EM Bright Classification
- Fermi Gamma-ray Burst Monitor trigger 757207662/241229978 (GRB 241229C) is not a GRB
- GRB241229B: UVOT upper limits
- GRB 241229C: Fermi GBM Final Real-time Localization
- GRB 241228B: D50 optical detection
- GRB 241228B: Fermi GBM Observation
- GRB 241228B: Swift-XRT afterglow detection
- GRB 241229B: Fermi GBM Observation
- GRB 241229A: Swift ToO observations
- GRB 241229B: NUTTelA-TAO / BSTI Optical Limits
- GRB 241228A: Mondy optical afterglow observations
- GRB 241229B: Swift-XRT refined Analysis
- IceCube-241224A: No transient candidates from the Zwicky Transient Facility
- Swift GRB 241229B: Global MASTER-Net observations report
- GRB 241229A: GOTO optical upper limits
- GRB 241228B: VLT/X-shooter redshift of z = 2.674
- GRB 241228A: NOT optical upper limits
- GRB 241228B: LCO optical observation
- GRB 241228A: Swift-BAT refined analysis
- GRB 241228B: Swift/BAT-GUANO localization skymap of a burst
- GRB 241229B: Swift detection of a burst
- GRB 241229B: Fermi GBM Final Real-time Localization
- GRB 241229A: SVOM detection of a long burst
- Fermi GRB 241228B: Global MASTER-Net observations report
- GRB 241228A: Fermi GBM Observation
- GRB241228B: GROWTH-India Telescope optical observations
- Swift GRB 241228A: Global MASTER-Net observations report
- GRB 241228B: LCOGT photometry of the likely optical counterpart GOTO24jmz
- GRB 241228B: GOTO24jmz optical follow-up observations
- GRB 241226A: Swift/BAT-GUANO localization skymap of a burst
- GRB 241228A: GROWTH-India telescope optical upper limit
- GRB 241228B: Swift ToO observations
- GRB 241228B: TRT optical counterpart confirmation
- GRB 241228A: Swift-XRT refined Analysis
- GRB 241228A: Swift/UVOT Upper Limits
- GRB 241228B: GOTO possible optical counterpart candidate
- GRB 241228A: Enhanced Swift-XRT position
- GRB 241228B: Fermi GBM Final Real-time Localization
- GRB 241228A: Swift detection of a burst
- IceCube-241224A: Upper limits from a search for additional neutrino events in IceCube
- LIGO/Virgo/KAGRA S241225c: Two counterpart neutrino candidates from IceCube neutrino searches
- GRB 241223A: GRBAlpha detection
- GRB 241212A: VZLUSAT-2 detection
- GRB 241217A/EP241217b: continued SOAR observations
- Fermi GRB 241226A: Global MASTER-Net observations report
- GRB 241226A: Fermi GBM Final Real-time Localization
- EP241223a: Mondy AZT-33IK optical observations
- GRB 241029A: LCO optical observation
- GRB 241223A: Swift-XRT observations
- LIGO/Virgo/KAGRA S241225v: Identification of a GW compact binary merger candidate
- GRB 241029A: AbAO AS-32 optical observations
- GRB 241223A: Fermi GBM Detection
- Fermi trigger No 756678579: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S241225c: Identification of a GW compact binary merger candidate
- EP241223a
- IceCube-241224A - IceCube observation of a high-energy neutrino candidate track-like event
- IceCube Alert 241224.30: Global MASTER-Net observations report
- GRB 241219A: SVOM/GRM observation
- EP241223a: Global MASTER-Net observations report
- EP241223a: EP-WXT detection of a fast X-ray transient
- EP241113a: Non-detection in Radio Follow-up Observations with eMERLIN
- GRB241113A: 7DT Optical upper limits
- Fermi Gamma-ray Burst Monitor trigger 756678579 / 241223854 is not a GRB
- Fermi GRB 241223A: Global MASTER-Net observations report
- GRB 241223A: GOTO optical observations summary
- GRB 241105A: JWST photometric observations of the host galaxy
- GRB 241223A: Swift ToO observations
- EP241217a: e-MERLIN radio observations
- GRB 241223A: BALROG localization (Fermi Trigger 756648531 / GRB 241223506)
- GRB 241223A: Fermi GBM Final Real-time Localization
- GRB 241217A / EP241217b: Non-detection in ATCA Radio Follow-up Observations
- The EP-WXT trigger 01709129287 is likely a flaring star
- Fermi trigger No 756447119: Global MASTER-Net observations report
- GRB 241209B: host galaxy detection and GTC/OSIRIS+ spectroscopy
- Fermi Gamma-ray Burst Monitor trigger 756447119/241221175 is not a GRB
- Fermi GRB 241221A: Global MASTER-Net observations report
- GRB 241221A: Fermi GBM Final Real-time Localization
- GRB 241217A/EP241217b: SOAR afterglow detection
- EP241217a: Liverpool Telescope optical upper limit
- EP241021a: VLA radio detection
- GRB 241218A: Mondy AZT-33IK optical upper limit
- EP241217a : Leavitt Observatory optical upper limit
- GRB 241217A/EP241217b: tentative VLT spectroscopic redshift z=1.879
- EP241217a: 1.6m Mephisto multi-band optical observations
- GRB 241217a/EP241217B: 1.6m Mephisto optical upper limits
- GRB 241218A: Swift/UVOT Upper Limits
- EP241217a: optical upper limit with the Liverpool Telescope
- GRB 241209B: EP-FXT afterglow detection
- Konus-Wind detection of GRB 241204A (short/hard)
- GRB 241218A: NOT optical upper limits
- GRB 241218A: Swift-BAT refined analysis
- GRB 241217A / EP241217B: GRANDMA/T1MPicduMidi optical upperlimits