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').
- GRB 231017A: Swift-XRT observations
- GRB 231012B may not be a GRB
- GRB 231018A: BALROG localization (Fermi Trigger / GRB 231018521)
- GRB 231018A: Fermi GBM Final Real-time Localization
- GRB 231017A: Swift ToO observations
- GRB 231017A: Swift/BAT-GUANO candidate arcminute localization of a burst
- Fermi-LAT gamma-ray observations of IceCube-231014A
- GRB231017A: Fermi GBM Final Localization
- IceCube-231014A: Upper limits from a search for additional neutrino events in IceCube
- LIGO/Virgo/KAGRA S231014r: Upper limits from Swift/BAT-GUANO
- (correction) Discovery of an optical transient with strong flaring activity: a new blazar candidate in the Messier 31 field
- Discovery of an optical transient with strong flaring activity: a new blazar candidate in the Messier 31 field.
- IceCube-231014A - IceCube observation of a high-energy neutrino candidate track-like event
- LIGO/Virgo/KAGRA S231014r: Identification of a GW compact binary merger candidate
- Correction in GCN 34814: GRB 231012B (not GRB 231012A)
- GRB 231012A: Fermi GBM Final Real-time Localization
- GRB 231012A: Fermi GBM Final Real-time Localization
- GRB 231004A: Glowbug gamma-ray detection
- LIGO/Virgo/KAGRA S231001aq: Updated Sky localization
- IceCube-231004A: One Candidate Counterpart from the Zwicky Transient Facility
- LIGO/Virgo/KAGRA S231005j: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S231008ap: Updated Sky localization
- LIGO/Virgo/KAGRA S231008ap: Identification of a GW compact binary merger candidate
- IceCube-231004A: Upper limits from a search for additional neutrino events in IceCube
- IceCube-231004A: No significant detection in HAWC
- GRB 231004A: CALET Gamma-Ray Burst Monitor detection
- Fermi-LAT gamma-ray observations of IceCube-231004A
- LIGO/Virgo/KAGRA S231005ah: Updated Sky localization
- LIGO/Virgo/KAGRA S231005ah: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S231005j: Updated Sky localization
- LIGO/Virgo/KAGRA S231005j: Identification of a GW compact binary merger candidate
- Update of IceCube-231004A - Corrected direciton
- IceCube-231004A - IceCube observation of a high-energy neutrino candidate track-like event
- transient AT2023sva: radio observations with AMI-LA
- GRB 231004A: Fermi GBM Final Real-time Localization
- GRB 231003A is not a GRB
- GRB 231003A: Fermi GBM Final Real-time Localization
- LIGO/Virgo/KAGRA S231001aq: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S230930al: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S230928cb: Upper limits from Swift/BAT-GUANO
- GRB 230827B: 10.4m GTC spectroscopic redshift
- LIGO/Virgo/KAGRA S231001aq: Updated Sky localization
- LIGO/Virgo/KAGRA S230930al: Updated Sky localization
- LIGO/Virgo/KAGRA S230928cb: Updated Sky localization
- LIGO/Virgo/KAGRA S231001aq: Identification of a GW compact binary merger candidate
- GRB 230930A: Fermi GBM Final Real-time Localization
- LIGO/Virgo/KAGRA S230930al: Identification of a GW compact binary merger candidate
- NuEm-230927A: Swift-XRT follow-up
- LIGO/Virgo/KAGRA S230928cb: Identification of a GW compact binary merger candidate
- AT2023sva / GRB230916B: GIT observations of the afterglow
- transient AT2023sva: A Binary Driven Hypernova with a possible associated supernova
- LIGO/Virgo/KAGRA S230927be: Updated Sky localization
- LIGO/Virgo/KAGRA S230927l: Updated Sky localization
- AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230927A
- LIGO/Virgo/KAGRA S230927be: Identification of a GW compact binary merger candidate
- Swift Triggers 1192745 and 1192747 are not astrophysical events
- LIGO/Virgo/KAGRA S230927l: Identification of a GW compact binary merger candidate
- Swift Triggers 1192740, 1192742 and 1192743 are not astrophysical events
- Swift Triggers 1192735 and 1192737 are not astrophysical events
- LIGO/Virgo/KAGRA S230922q: Updated Sky localization
- Konus-Wind detection of GRB 230919A
- LIGO/Virgo/KAGRA S230924an: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S230920al: Upper limits from Swift/BAT-GUANO
- Title: LIGO/Virgo/KAGRA S230919bj: Upper limits from Swift/BAT-GUANO
- Fermi Gamma-ray Burst Monitor trigger 717299390/230925076 is not a GRB
- Fermi Gamma-ray Burst Monitor trigger 230925241/717313591 is not a GRB
- LIGO/Virgo/KAGRA S230922g: DECam GW-MMADS candidates
- GRB 230812B: r'-band observations from MISTRAL at Observatoire de Haute-Provence
- LIGO/Virgo/KAGRA S230924an: Updated Sky localization
- LIGO/Virgo/KAGRA S230924an: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S230917af: GRAWITA wide-field observations
- LIGO/Virgo/KAGRA S230922g: Updated Sky localization
- LIGO/Virgo/KAGRA S230922g: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S230922q: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S230917af: Zwicky Transient Facility observations
- GRB 230921A: Fermi GBM Final Real-time Localization
- GRB 230918B: VLT/X-shooter classification of AT 2023tbf (GOTO23aky) as a dwarf nova
- IPN triangulation of GRB 230919A (short)
- LIGO/Virgo/KAGRA S230904n: Classification of the candidate AT2023rkw with DBSP
- GRB 230919A: Fermi GBM Observation
- Correction to Fermi GBM Statement for Trigger 716527670/230916144
- Fermi GBM Statement for Trigger 716527670/230916144
- GRB 230919A: Swift/BAT-GUANO detection of a possibly short burst outside the coded FOV
- LIGO/Virgo/KAGRA S230920al: Updated Sky localization
- LIGO/Virgo/KAGRA S230919bj: Updated Sky localization
- transient AT2023sva: imaging and spectroscopic observations from MISTRAL at Observatoire de Haute-Provence
- GRB 230812B : optical observations from MISTRAL at Observatoire de Haute-Provence
- GRB 230919A: AstroSat CZTI detection
- LIGO/Virgo/KAGRA S230920al: Identification of a GW compact binary merger candidate
- AT2023sva: redshift from OSIRIS+/GTC of the ZTF afterglow
- LIGO/Virgo/KAGRA S230919bj: Identification of a GW compact binary merger candidate
- GRB 230918B: GOTO detection of a fast-rising transient in the GBM localisation region
- GRB 230919A: Fermi GBM Final Real-time Localization
- LIGO/Virgo S230917af: Swift XRT observations, 6 X-ray sources
- Detection of self-absorbed radio emission from GRB 230812B with the JVLA + uGMRT
- GRB 230918B: Fermi GBM Final Real-time Localization
- GRB 230918A (short): Glowbug gamma-ray detection
- GRB 230916B: Glowbug gamma-ray detection
- AT 2023sva: NOT observations of the ZTF candidate afterglow
- ZTF and SEDM Observations of the Candidate Optical Afterglow AT 2023sva