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').
- GRB 240602A: Fermi GBM Final Real-time Localization
- LIGO/Virgo/KAGRA S240601co: Identification of a GW compact binary merger candidate
- Swift Trigger 1232465 is not a GRB
- GRB 240529A: AKO Optical Afterglow Follow-Up Observations
- LIGO/Virgo/KAGRA S240530a: Updated Sky localization
- LXT 240528A: GSP optical upper limit
- GRB 240529A: 1.3m DFOT Optical observations
- LIGO/Virgo/KAGRA S240527en: Updated Sky localization
- LIGO/Virgo/KAGRA S240601aj: Identification of a GW compact binary merger candidate
- GRB 240531A: AstroSat CZTI detection of a short burst
- GRB 240529A : Mondy optical observations
- Konus-Wind detection of GRB 240529A
- IPN triangulation of the initial episode of GRB 240529A
- GRB 240529A: SAO RAS optical observations
- LIGO/Virgo/KAGRA S240531bp: Updated Sky localization
- LIGO/Virgo/KAGRA S240531bp: Identification of a GW compact binary merger candidate
- GRB 240529A: MAAO 0.7m telescope optical afterglow detection
- GRB 240529A: Insight-HXMT/HE detection
- GRB 240529A: optical photometry from Konkoly
- GRB 240529A: GROWTH-India optical follow-up
- GRB 240529A: T193/MISTRAL observations
- GRB 240529A: Redshift from GTC/OSIRIS+
- GRB 240529A: AKO Optical Afterglow Detection
- LIGO/Virgo/KAGRA S240530a: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S240527fv: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S240525p: Upper limits from Swift/BAT-GUANO
- GRB 240529A: J-band detections with WINTER
- GRB 240529A: Skynet Optical Observations
- LXT 240528A: LEIA detection of a fast X-ray transient
- GRB 240529A: Swift-BAT refined analysis
- LIGO/Virgo S240527fv: GRANDMA/FRAM-Auger Optical Observations
- GRB 240529A: Swift-XRT refined Analysis
- GRB240529A: BOOTES-6/DPRT optical detection
- GRB 240529A: Swift/UVOT Detection
- GRB 240529A: NOT optical observations
- GRB 240529A: AstroSat CZTI detection
- GRB 240529A: GOTO optical afterglow detection
- GRB 240527B: Swift-XRT afterglow detection
- GRB 240529A: Enhanced Swift-XRT position
- GRB 240529A: Swift detection of a burst with an optical counterpart
- Swift GRB240529.12: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S240527fv: Updated Sky localization
- GRB 240527B: Fermi GBM Observation
- Fermi GRB 240527A: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S240527fv: Identification of a GW compact binary merger candidate
- GRB 240527B: Fermi-LAT detection
- LAT GRB240527.59: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S240527en: Identification of a GW compact binary merger candidate
- Fermi GRB 240527B: Global MASTER-Net observations report
- GRB 240527B: Fermi GBM Final Localization
- GRB 240527B: BALROG localization (Fermi Trigger 738511436 / GRB 240527586)
- GRB 240527A: Fermi GBM Final Real-time Localization
- GRB 240523A: Swift-BAT refined analysis
- Fermi trigger No 738348224: Global MASTER-Net observations report
- Fermi trigger No 738330463: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S240525p: Updated Sky localization
- LIGO/Virgo/KAGRA S240525p: Identification of a GW compact binary merger candidate
- GRB 240523A: Swift-XRT refined Analysis
- GRB 240523A: Enhanced Swift-XRT position
- GRB 240523A: Swift detection of a burst
- GRB 240521B: Fermi GBM Observation
- Fermi GBM Sub-Threshold Detection of GRB 240516B
- GRB 240513A: Swift-XRT afterglow detection
- GRB 240521B: Swift/BAT-GUANO arcminute localization of a long burst
- Fermi trigger No 737996942: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S240520cv: Updated Sky localization and EM Bright Classification
- EP240518a: GSP optical upper limit
- GRB 240521A: GECAM-B detection of a long burst
- GRB 240516B: AstroSat CZTI detection
- LIGO/Virgo/KAGRA S240515m: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S240514x: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S240513ei: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S240520cv: Identification of a GW compact binary merger candidate
- IceCube-Cascade 240518A: Upper limits from a search for additional neutrino events in IceCube
- GRB 240514B: VZLUSAT-2 detection
- GRB 240504A: VZLUSAT-2 detection
- GRB 240502A: VZLUSAT-2 detection
- GRB 240519A: GRBAlpha detection
- GRB 240516A: Swift/UVOT Upper Limits
- GRB 240519A: AstroSat CZTI detection
- Fermi trigger No 737788024: Global MASTER-Net observations report
- EP240518a: possibly identified with a flare star by EP-FXT
- GRB 240519A: BALROG localization (Fermi Trigger 737788024 / GRB 240519213)
- EP240518a: EP-WXT detection of a new X-ray transient
- LIGO/Virgo/KAGRA S240514c: Updated Sky localization
- GRB 240516A: Swift-BAT refined analysis
- Fermi GRB 240517A: Global MASTER-Net observations report
- GRB 240516A ATCA radio observations
- IPN triangulation of GRB 240514B (short)
- GRB 240513A: Swift ToO observations
- GRB 240517A: Fermi GBM Final Real-time Localization
- Konus-Wind detection of GRB 240513A
- GRB 240516A: AstroSat CZTI detection
- GRB 240516A: Swift-XRT refined Analysis
- GRB 240514E: A possible candidate BD-21 1074
- Fermi trigger No 737559855: Global MASTER-Net observations report
- GRB 240516A: Fermi GBM Observation
- GRB 240511A: Observations from GTC/OSIRIS+
- GRB 240502C: Zeiss-1000 at Koshka observations of GOTO24bao optical counterpart candidate
- GRB 240516A: GOTO optical upper limit