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').
Advanced Search
To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.
Advanced Search Examples (click to copy):
subject:"Swift"body:"GRB"submitter:"Judith Racusin"- IceCube-190104A - IceCube observation of a high-energy neutrino candidate event
- GRB 190103B: Swift-XRT refined Analysis
- GRB 190103B: Enhanced Swift-XRT position
- GRB 190103B: Swift detection of a burst
- GRB 181201A: photometric signature of the SN
- GRB 190103A: AGILE/MCAL detection of a burst
- GRB 181231A: BOOTES-2/TELMA optical observations
- GRB 181231A: Fermi GBM detection
- GRB 181231A: Fermi-LAT detection
- GRB 181228A: Mondy and AbAO optical upper limits
- GRB 181225A: further Swift-XRT observations
- GRB 181228A: Global MASTER Net OT is the same REM IR transient
- GRB 181228A: possible NOT optical detection
- Fermi GBM trigger 567868083/181230547 is not a GRB
- GRB 181227A: CALET Gamma-Ray Burst Monitor detection
- GRB 181228A: MITSuME Akeno optical upper limits
- Konus-Wind observation of GRB 181227A
- GRB 181228A: Xinglong-2.16m optical upper limit
- FRB 181228: Global MASTER Net optical inspection
- GRB 181227A: Global MASTER Net oprtical inspection
- Swift Trigger 880127 is not a GRB
- GRB 181228A: Swift-XRT refined Analysis
- GRB 181228A: Swift-BAT refined analysis
- GRB 181222B: Swift follow-up observations of MASTER optical transient J204928.79+245744.0
- GRB 181228A: Swift/UVOT Upper Limits
- GRB 181228A: TSHAO optical upper limit
- GRB 181228A: Fermi GBM observation
- IPN Triangulation of GRB 181227A (long)
- GRB 181228A: Global MASTER Net OT detection
- GRB 181228A: REM NIR detection
- GRB 181228A: Enhanced Swift-XRT position
- GRB 181225A: CALET Gamma-Ray Burst Monitor detection
- GRB 181225A: KAIT Follow-Up Observations with Upper Limit
- GRB 181228A: KAIT Optical Upper Limit
- GRB 181228A: Swift detection of a burst
- GRB 181227A: Fermi GBM detection
- GRB 181222B: Swift ToO observations
- GRB 181225A: Insight-HXMT/HE detection
- GRB 181222A: AstroSat CZTI detection
- GRB 181225A: Swift observations and X-ray candidate afterglow
- GRB 181225A: Global MASTER Net optical observations
- GRB 181225A: Swift ToO observations
- GRB 181225A: Fermi GBM detection
- GRB 181225A: Fermi-LAT Detection
- GRB 181225A: AGILE/MCAL detection of a burst
- Konus-Wind observation of GRB 181222A
- GRB 181222B: Global MASTER Net observations of short bright Fermi GRB
- Konus-Wind observation of GRB 181222B
- IPN Triangulation of extremely bright short GRB 181222B
- GRB 181224A: Swift-BAT refined analysis
- GRB 181224A: Swift detection of a burst
- GRB 181222A: CALET Gamma-Ray Burst Monitor detection
- GRB 181222B: Global MASTER Net observations of the short bright Fermi GRB error box.
- GRB 181222B : Fermi GBM detection
- Trigger 878548: Swift detection of AX 1631.9-4752
- Swift Trigger 878504 is not astrophysical
- GRB 181222A: Fermi GBM observation
- GRB 181222A: MAXI/GSC detection
- GRB 181217A: Insight-HXMT/HE detection
- GRB 181213A: Swift/UVOT Observations
- GRB 181213A: Mondy optical observations
- GRB 181213A: continued TSHAO optical observations
- GRB 181213A:Insight-HXMT/HE detection
- GRB 181212A:Insight-HXMT/HE detection
- Konus-Wind observation of GRB 181212A
- GRB 181213A: AbAO optical observations
- GRB 181213A: HMM-0.5m, NEXT-0.6m, CNEOST-1m optical observations
- GRB 181213A: NOT optical observations
- GRB 181213A: Swift-XRT refined Analysis
- GRB 181213A: Enhanced Swift-XRT position
- IPN Triangulation of GRB 181212A (long)
- GRB 181213A: Swift-BAT refined analysis
- GRB 181213A: GWAC-F60A upper limit
- GRB 181126A: MeerKAT radio observation
- GRB 181213A : TSHAO optical observations
- GRB181213A: Swift/UVOT Detection
- GRB 181213A: Swift-XRT observations
- GRB 181213A: BOOTES-5/JGT optical observations
- SWIFT GRB181213A Global MASTER-Net bright OT discovery
- GRB 181213A: Swift detection of a burst
- GRB 181212A: Fermi GBM Detection
- GRB 181126B: KAIT Follow-Up Observations of a Fermi Short GRB (Trigger 564897175)
- GRB 181201A: continued optical observations in Mondy
- MASTER OT J063515.49-624002.9 of Fermi trigger 565936249: optical observations in SAAO
- MASTER: OTs detection during Fermi alert trigger 565936249 early observations
- GRB 181201A: VLA detection
- GRB 181201A: ALMA detection of a fading mm afterglow
- INTEGRAL observations of the events in the GWTC-1 catalog
- GRB 181203A: GROND detection of the afterglow
- GRB 181126B: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 564897175)
- GRB 181201A: continued optical observations in TSHAO and Chilesope
- GRB 181203A: BOOTES-3/YA optical observations
- GRB 181205A: a long GRB detected by INTEGRAL
- GRB 180112B: AstroSat CZTI detection
- GRB181201A: Optical afterglow measurements by GROWTH-India
- Swift Trigger 874754 is likely not an astrophysical event
- Fermi-GBM Observations During Four New GW-Detected BBH Mergers (Correction)
- GRB 181201A: continued optical observations in TSHAO
- Fermi-GBM Observations During Four New GW-Detected BBH Mergers
- GRB 181203A: Swift/UVOT Upper Limits