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"- 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
- GRB 181201A: Continued GROND observations show that afterglow is still bright
- GRB181201A: GOTO optical observations
- GRB 181203A: Swift-XRT refined Analysis
- GRB 181201A: AstroSat CZTI detection
- GRB 181203A: Swift-BAT refined analysis
- GRB 181201A: Swift/UVOT Detection
- GRB 181202A: Swift/UVOT Detection
- GRB 181201A: continued optical observations in SAAO and Chilesope
- GRB 181202A: RATIR Optical and NIR Observations
- Konus-Wind observation of GRB 181201A
- GRB 181203A: Enhanced Swift-XRT position
- GRB 181203A: Swift detection of a burst
- GRB 181201A: Further COATLI Optical Monitoring
- GRB 181201A: Insight-HXMT/HE detection
- GRB 181202A: Global MASTER-Net optical observations
- GRB 181202A: Swift-BAT refined analysis
- GRB 181201A: VLT/FORS2 tentative spectroscopic redshift
- GRB 181202A: Swift-XRT refined Analysis
- GRB 181201A: GROND detection of the afterglow and redshift upper limit of z < 3
- GRB 181201A: optical observations in Chilescope observatory
- GRB 181201A: Global MASTER-Net prompt optical descovery and afterglow observations
- GRB 181202A: Enhanced Swift-XRT position
- GRB 181202A: Swift detection of a burst with an optical counterpart
- GRB 181201A: COATLI Optical Detection
- GRB 181201A: Fermi-LAT detection
- GRB 181201A: Zeiss-1000/CrAO optical observations
- GRB 181201A: NOT optical observations
- GRB 181201A: optical observations in SAAO
- GRB 181201A MASTER-Net OT continued observation
- GRB 181201A: iTelescope optical afterglow detection
- GRB 181201A: Swift-XRT afterglow detection
- GRB 181201A: Swift ToO observations
- GRB 181201A: Swift-XRT afterglow
- GRB 181201A: likely Swift/XRT afterglow
- GRB 181201A MASTER-Net OT detection
- GRB 181201A: a long GRB detected by INTEGRAL
- GRB 181119A: CALET Gamma-Ray Burst Monitor detection
- GRB 181123B: ATCA 5/9 GHz rapid-response radio observation
- Short-duration GRB 181121.4: MASTER-Tavrida possible OT detection near the PGC galaxy during large Fermi error box inspection
- GRB 181127A : a long GRB detected by INTEGRAL
- GRB 181126A: Swift-BAT refined analysis
- GRB 181126A: No Ks-band afterglow detection with Keck I
- GRB 181123B: Keck further near-infrared imaging
- GRB 181126A: Swift/UVOT Upper Limits
- GRB 181126A: Swift-XRT refined Analysis
- GRB 181126A deep Gemini imaging
- GRB 181126A: Fermi GBM observation
- Konus-Wind observation of GRB 181121A
- GRB 181126A: Enhanced Swift-XRT position
- GRB 181126A: Prompt enhanced Swift-XRT position
- GRB 181126A: Swift detection of a burst
- GRB 181123B: Insight-HXMT/HE detection
- GRB 181125A: Fermi GBM observation
- GRB 181125A: Swift-BAT refined analysis
- IPN Triangulation of GRB 181121A (short)
- GRB 181125A: Swift detection of a burst
- GRB 181121A: AstroSat CZTI detection
- Swift J1858.6-0814/GRB 181123A: Swift/BAT location correction to GCN 23442
- Swift trigger 873178: GRB 181123A is Swift J1858.6-0814
- GRB 181123B: Global MASTER Net optical inspection
- GRB 181123B: Swift-BAT lag analysis and search for extended emission
- GRB 181123A, Swift-BAT refined analysis
- GRB 181123B: Keck near-infrared imaging
- GRB 181123B: Gemini-North optical detection
- GRB 181119A: AstroSat CZTI detection
- GRB 181123B: Swift/UVOT Upper Limits
- GRB 181020A: AstroSat CZTI detection
- GRB 181123B: Swift-XRT refined Analysis
- GRB 181123B: Enhanced Swift-XRT position
- GRB 181123B: Prompt enhanced Swift-XRT position
- GRB 181123B: Swift detection of a short burst
- GRB 181123A: Swift detection of a burst
- GRB 181119A: Insight-HXMT/HE detection
- GRB 181121A: AGILE/MCAL detection of a burst
- GRB 181120A: Fermi GBM observation
- GRB 181120A: Fermi-LAT detection