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').
- EP241021a: SAO RAS optical observations
- EP241021a: KAIT optical observations
- EP241021a: EP-FXT follow-up observation update
- IPN triangulation of GRB 241021A (long)
- EP241021a: Optical counterpart observations with the Liverpool Telescope
- EP241021a: 1.3m DFOT Optical observations
- EP241021a: GSP detects optical candidate counterpart
- EP241021a: Optical upper limits with Kinder observations
- EP241021a: TRT optical observations
- GRB 241018A: SVOM/C-GFT optical observations
- EP241021a: NOT likely optical counterpart
- EP EP241021a: Global MASTER-Net observations report
- GRB241017A: 1.3m DFOT optical upper limit
- GRB 241018A: 1.3m DFOT Optical upper limit
- GRB 241018A: EP-FXT afterglow detection
- EP241021a: GOTO optical upper limits
- EP241021a: EP detection of a fast X-ray transient
- IceCube-Cascade 241019A: Upper limits from a search for additional neutrino events in IceCube
- Konus-Wind detection of GRB 241018A
- GRB 241018A: SVOM/GRM observation
- GRB 241018A/sb24101802: Mephisto optical upper limit
- GRB 241017A/sb24101702: Mephisto optical upper limit
- GRB 241018A: BOOTES-4/MET optical upper limit
- GRB 241018A: Mondy optical upper limit
- GRB 241018A: SVOM/VT further analysis and counterpart confirmed
- GRB 241018A: GROWTH-India telescope optical upper limit
- GRB241018A: XingLong Optical Upper Limit
- GRB 241018A: Swift-XRT observations
- GRB 241018A: REM optical/NIR upper limits
- GRB 241018A: NOT optical observations
- GRB 241017A: SVOM/VT follow-up and optical upper limit
- GRB 241018A: SVOM/VT follow-up and optical candidate
- GRB 241018A: LCO/0.4m optical upper limits
- GRB 241018A: Swift ToO observations
- GRB 241006A: VIRT Optical Upper Limit
- GRB 240727A: VIRT Optical Upper Limit
- GRB 241018A: X-ray afterglow candidate observed by MXT
- GRB 241016B: Fermi GBM Observations
- GRB 241018A: Detection of a bright long GRB by SVOM
- GRB 241017A: Swift-XRT observations
- GRB241017a: Liverpool Telescope observations of XRT uncatalogued sources
- GRB 241001A: EP-FXT afterglow detection
- GRB 241017A: GROWTH-India Telescope optical upper limit
- GRB241017A: TOO Observations by SVOM/MXT
- GRB 241016B: Swift/BAT-GUANO localization skymap of a short burst
- GRB 241017A: J-band upper limit from WINTER
- Fermi trigger No 750788395: Global MASTER-Net observations report
- GRB 241016B: SVOM/GRM observation
- GRB241016C: Fermi GBM Final Localization
- Fermi Gamma-ray Burst Monitor trigger 750792698/241016730 is not a GRB
- GRB 241017A: Swift ToO observations
- GRB 241017A : Detection of a weak and soft long duration GRB by SVOM/ECLAIRs
- Fermi GRB 241016B: Global MASTER-Net observations report
- GRB 241016B: Fermi GBM Final Localization
- Fermi GRB 241016A: Global MASTER-Net observations report
- GRB 241016A: Fermi GBM Final Real-time Localization
- IceCube alert 139977_2910365 retraction
- IceCube Alert 241016.04: Global MASTER-Net observations report
- GRB 241010A: Swift-BAT refined analysis
- GRB 241013B: Fermi GBM Observation
- GRB 241013B: Swift/BAT-GUANO localization skymap of a burst
- GRB 241013A: Fermi GBM Observation
- GRB 240916A: radio detection with the VLA
- GRB241013A: REM observations
- GRB 241009A: LCO optical upper limits
- GRB 241013B: SVOM/GRM observation
- Fermi GRB 241013B: Global MASTER-Net observations report
- Integral GRB241013.04: Global MASTER-Net observations report
- GRB 241013B: Fermi GBM Final Real-time Localization
- GRB 241013A: a long GRB detected by INTEGRAL
- GRB 241013A: Fermi GBM Final Real-time Localization
- LIGO/Virgo/KAGRA S241009em: Updated Sky localization
- LIGO/Virgo/KAGRA S241011k: Updated Sky localization
- LIGO/Virgo/KAGRA S241011k: NED Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S241011k: Identification of a GW compact binary merger candidate
- Fermi Gamma-ray Burst Monitor GRB trigger 750372658/241011869 (GRB 241011A) is not a GRB
- GRB 241011A: Fermi GBM Final Real-time Localization
- GRB 241009A: GRANDMA optical upper limits
- GRB 241009A: Swift-XRT afterglow detection
- GRB 241010A: JinShan optical observations and potential host galaxy
- GRB 241006A: ATCA Radio Upper Limits
- GRB 241010A: Swift-XRT refined Analysis
- LIGO/Virgo/KAGRA S241007bw: Updated Sky localization
- Fermi trigger No 750211959: Global MASTER-Net observations report
- Fermi Gamma-ray Burst Monitor trigger 750303285/241011066 is not a GRB
- Fermi Gamma-ray Burst Monitor trigger 750291012/241010924 is not a GRB
- Swift GRB 241010A: Global MASTER-Net observations report
- Fermi trigger No 750291012: Global MASTER-Net observations report
- GRB 241010A: J-band observations with WINTER
- LIGO/Virgo/KAGRA S241009an: Updated Sky localization
- Fermi GRB 241010B: Global MASTER-Net observations report
- GRB 241010B: Fermi GBM Final Real-time Localization
- IceCube-241006A: Upper limits from a search for additional neutrino events in IceCube
- GRB 241010A: Enhanced Swift-XRT position
- GRB 241010A: LCO optical observations
- GRB 241010A: Swift detection of a burst with an optical counterpart
- Fermi-LAT Gamma-ray Observations of IceCube-241006A
- GRB 241006A: Swift-BAT refined analysis
- GRB 241009A: Swift ToO observations
- LIGO/Virgo/KAGRA S241009l: Updated Sky localization