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').
- Fermi GRB 230603A: Global MASTER-Net observations report
- Fermi trigger No 707039690: Global MASTER-Net observations report
- GRB 230506B: Chandra localization of the X-ray afterglow
- ZTF and GIT Observations of the Candidate Optical Afterglow AT2023jxk
- GRB 230606A: Swift-BAT refined analysis
- GRB 230606A: Gaoyazi/GOT optical upper limit
- GRB 230606A: Fermi GBM Observation
- GRB 230606A: BOOTES-5/JGT optical upper limit
- LIGO/Virgo/KAGRA S230602ap: Zwicky Transient Facility observations
- GRB 230606A: Swift-XRT refined Analysis
- GRB 230604A: GRBAlpha detection
- GRB 230606A: Swift/UVOT Upper Limits
- LIGO/Virgo S230606z: Global MASTER-Net observations report
- GRB 230606A: Enhanced Swift-XRT position
- LIGO/Virgo S230606d: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S230606d: Identification of a GW compact binary merger candidate
- GRB 230606A: Swift detection of a burst
- Fermi-LAT gamma-ray observations of IceCube-230603A
- LIGO/Virgo/KAGRA S230605o: Updated Sky localization
- IceCube-230603A: Upper limits from a search for additional neutrino events in IceCube
- LIGO/Virgo/KAGRA S230601bf: Updated Sky localization
- Super-Kamiokande: Neutrino search for SN2023ixf
- GRB 230604A: AstroSat CZTI detection of a short GRB
- LIGO/Virgo/KAGRA S230605o: Identification of a GW compact binary merger candidate
- LIGO/Virgo S230605o: Global MASTER-Net observations report
- LIGO/Virgo S230604z: Global MASTER-Net observations report
- IceCube-230603A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 230603A: Fermi GBM Final Real-time Localization
- LIGO/Virgo S230603aa: Global MASTER-Net observations report
- LIGO/Virgo S230602ap: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S230518h: Upper limits from a two-week IceCube neutrino search
- GRB 230521A: VZLUSAT-2 detection
- GRB 230522A: GRBAlpha and VZLUSAT-2 joint detection
- LIGO/Virgo S230601bf: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S230601bf: Identification of a GW compact binary merger candidate
- LIGO/Virgo S230531f: Global MASTER-Net observations report
- GRB 230525A: CALET Gamma-Ray Burst Monitor detection
- LIGO/Virgo/KAGRA S230529ay: Zwicky Transient Facility observations
- LIGO/Virgo/KAGRA S230528a: Zwicky Transient Facility observations
- LIGO/Virgo/KAGRA S230527ch: Zwicky Transient Facility observations
- LIGO/Virgo/KAGRA S230529ay: Upper limits from CALET observations.
- LIGO/Virgo/KAGRA S230529ay: AstroSat CZTI non-detection and upper limits
- LIGO/Virgo S230529ay: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S230529ay: upper limits from AGILE/MCAL
- LIGO/Virgo/KAGRA S230529ay: Coverage and upper limits from MAXI/GSC observations
- LIGO/Virgo/KAGRA S230529ay: Upper limits from Fermi-GBM Observations
- LIGO/Virgo/KAGRA S230529ay: Updated Sky localization and EM Bright Classification
- LIGO/Virgo/KAGRA S230529ay: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
- LIGO/Virgo/KAGRA S230529ay: Identification of a GW compact binary merger candidate
- LIGO/Virgo S230529p: Global MASTER-Net observations report
- GRB 230529A: Fermi GBM Final Real-time Localization
- Alert from the HAWC Burst Monitor HAWC-230527A
- LIGO/Virgo S230525a: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S230518h: Updated Sky localization
- LIGO/Virgo/KAGRA S230520ae: Updated Sky localization
- Fermi-LAT gamma-ray observations of IceCube-230524A
- LIGO/Virgo/KAGRA S230518h: Upper limits from Glowbug gamma-ray observations
- GRB 230510A: Swift-BAT refined analysis
- GRB 230525A: Fermi GBM Detection
- LIGO/Virgo/KAGRA S230518h: TESS observations of the localization region
- GRB 230525A: Fermi GBM Final Localization
- IceCube-230524A: Upper limits from a search for additional neutrino events in IceCube
- GRB 230523B: GRBAlpha detection
- GRB 230524A: Fermi GBM Observation
- IceCube Alert 230524.47: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S230518h: No transient candidates in CALET observations
- LIGO/Virgo/KAGRA S230524x: Retraction of GW compact binary merger candidate
- IceCube-230524A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 230524B: AstroSat CZTI detection
- GRB 230524A: AstroSat CZTI detection
- GRB 230524A: AGILE detection
- Fermi trigger No 706610076: Global MASTER-Net observations report
- LIGO/Virgo S230524b: Global MASTER-Net observations report
- GRB 230524A: Fermi GBM Final Real-time Localization
- Fermi trigger No 706599831: Global MASTER-Net observations report
- Fermi trigger No 706536788: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S230521k: MASTER new OT discovery
- GRB 230523B: Name correction from GCN Circular 33859
- GRB 230523A: Swift/BAT-GUANO detection of a short hard burst
- LIGO/Virgo/KAGRA S230521k: Additional candidates from Zwicky Transient Facility
- Fermi Gamma-ray Burst Monitor trigger 706536788/230523509 is not a GRB
- GRB 230523A: Fermi GBM Final Real-time Localization
- AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230523A
- LIGO/Virgo S230522n: Global MASTER-Net observations report
- LIGO/Virgo S230522a: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S230522n: Upper limits from IceCube neutrino search
- LIGO/Virgo/KAGRA S230518h: Swift/UVOT Upper Limits for MeerLICHT candidates: AT2023ixg and AT2023iyb
- LIGO/Virgo/KAGRA S230522a: 2 counterpart neutrino candidates from IceCube neutrino searches
- LIGO/Virgo S230521k: Global MASTER-Net observations report
- # LIGO/Virgo/KAGRA S230521k: Zwicky Transient Facility observations
- GRB 230518B: VZLUSAT-2 detection
- Fermi Gamma-ray Burst Monitor trigger 706338208/230521211 is not a GRB
- LIGO/Virgo S230520ae: Global MASTER-Net observations report
- Fermi trigger No 706328428: Global MASTER-Net observations report
- IPN triangulation of GRB 230518A (short)
- Fermi trigger No 706331483: Global MASTER-Net observations report
- Fermi trigger No 706317104: Global MASTER-Net observations report
- GRB 230520A: CALET Gamma-Ray Burst Monitor detection
- GRB 230521A: Fermi GBM Final Real-time Localization
- LIGO/Virgo/KAGRA S230520ae: Identification of a GW compact binary merger candidate: End-to-End Test