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').
- EP240416a: EP-WXT detection of a fast X-ray transient
- GRB 240414A: AbAO optical upprer limit
- GRB 240415A: Swift/UVOT Detection
- EP240413a: BOOTES-2/TELMA Optical Upper Limit
- GRB 240415A: Fermi GBM Observation
- GRB 240414A: GAD Observatory, La Spezia, Italy ,upper limit
- GRB 240415A: Earliest optical followup with the Kinder observations
- GRB 240414A: GMG observation
- EP 240414a: BOOTES-4/MET Optical Upper Limits
- EP240414a: EP-FXT follow-up observation
- GRB 240415A: Enhanced Swift-XRT position
- GRB 240415B: Swift ToO observations
- GRB 240415B: Swift/BAT-GUANO Correction
- GRB 240415B: Swift/BAT-GUANO arcminute localization of a short burst
- GRB 240415A: OHP/T193 optical observations
- GRB 240415A: optical afterglow detection from the INAF Asiago Observatory
- GRB 240415A: SAO RAS optical observations
- GRB 240415A: Mondy optical transient detection (photometry correction in GCN 36118 )
- GRB 240414A: Fermi GBM Observation
- Fermi GRB 240415A: Global MASTER-Net observations report
- GRB 240415A: Mondy optical transient detection
- GRB 240414A: Photometric observation from 2.2m CAHA
- IceCube-240412A: Upper limits from a search for additional neutrino events in IceCube
- GRB 240414A: Swift/UVOT Detection
- LXT 240402A/GRB 240402B: Swift follow-up observations
- GRB 240414A: Mondy optical observations
- GRB 240414B: Fermi GBM Final Real-time Localization
- GRB 240414A: AKO Optical Upper Limit
- X-ray transient EP 240414a - GTC spectroscopic observations
- GRB 240415A: Prompt Swift-XRT observations
- GRB 240415A: Swift detection of a burst
- GRB 240415A: Fermi GBM Final Real-time Localization
- EP240413a: Upper limits from GECAM-B Observation
- EP 240414a: NOT optical counterpart confirmation
- GRB 240414A: Swift-XRT refined Analysis
- GRB240414A : J-band upper limits from WINTER
- GRB 240414A: Enhanced Swift-XRT position
- GRB 240414A : OHP/T193 second epoch of optical follow-up and afterglow detection
- GRB 240414A: MarSEC Observatory, Vicenza, Italy, UPPER LIMIT
- LIGO/Virgo/KAGRA S240413p: No Counterparts in DDOTI/OAN Optical Observations
- EP240413A: GOTO optical upper limits
- GRB 240414A: Skynet Optical Afterglow Observations
- Fermi trigger No 734754044: Global MASTER-Net observations report
- Swift GRB 240414A: Global MASTER-Net observations report
- EP240414a: Kinder optical counterpart candidate possibly associated with the galaxy SDSS J124601.99-094309.3
- IPN triangulation of GRB 240410A
- EP240413a: possible detection of the X-ray emission with EP-FXT after 14 hours
- EP240414a: EP-WXT detection of a fast X-ray transient
- IPN triangulation of GRB 240411A
- Fermi-LAT gamma-ray observations of IceCube-240412A
- GRB 240414A : MITSuME Akeno optical upper limits
- GRB 240414A: Redshift confirmation from GTC/OSIRIS+
- EP240413a: EP-WXT detection of a fast X-ray transient
- GRB 240414A : OHP/T193 redshift determination
- GRB 240414A : OHP/T193 optical counterpart detection
- GRB 240414A: Swift detection of a burst
- LIGO/Virgo/KAGRA S240413p: Updated Sky localization
- LIGO/Virgo/KAGRA S240413p: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S240413p: Zwicky Transient Facility observations
- EP240408a: GSP optical upper limit
- GRB 240411B: CrAO/ZTSh optical observations
- GRB 240411B: Kinder observations with Lulin observatory
- LIGO/Virgo/Kagra S240413p: NED Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S240413p: Identification of a GW compact binary merger candidate
- GRB 240411B: HiPERCAM/GTC observation
- IceCube Alert 240412.23: Global MASTER-Net observations report
- GRB 240411B: Swift-BAT refined analysis
- GRB 240411B: Swift-XRT refined Analysis
- IceCube-240412A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 240411B: 1.3m DFOT Optical observations
- GRB 240411A: GRBAlpha detection
- GRB 240411B: OHP/T193 optical observations
- GRB 240405A: Glowbug gamma-ray detection
- GRB 240411B: Enhanced Swift-XRT position
- GRB 240411B: LCO optical afterglow detection
- GRB 240411B: Swift detection of a burst
- GRB 240408B: GRBAlpha detection
- GRB 240411A: Fermi GBM Final Real-time Localization
- EP240408A: MASTER optical observations
- EP240408a: GROND detection of a candidate counterpart
- EP240408a: Upper limits from GECAM-B Observation
- EP240408a: Swift follow-up observation
- EP240408a: BOOTES-6/DPRT optical upper limit
- X-ray transient EP240315a: second epoch e-MERLIN radio observations
- GRB 240405A: GRBAlpha detection
- EP240408a: EP-WXT detection of a fast X-ray transient
- Swift Trigger 1220736: detection of 4U 1543-62.
- GRB 240408B: AstroSat CZTI detection
- IceCube-240327B: GRANDMA/Kilonova-Catcher observations of 4FGL J0555.9+0030 and optical upper limits
- Fermi GRB 240408A: Global MASTER-Net observations report
- GRB 240408A: Fermi GBM Final Real-time Localization
- GRB 240407A: BALROG localization (Fermi Trigger 734144396 / GRB 240407042)
- GRB 240402C: CALET Gamma-Ray Burst Monitor detection
- Fermi GRB 240407A: Global MASTER-Net observations report
- GRB 240407A: Fermi GBM Final Real-time Localization
- Fermi-LAT gamma-ray observations of IceCube-240327B
- Fermi-LAT gamma-ray observations of IceCube-240327A
- LXT 240402A/GRB 240402B: rest-frame energetics from Konus-Wind observation
- Fermi GRB 240405B: Global MASTER-Net observations report
- GRB 240405B: Fermi GBM Final Real-time Localization