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 151031A: Swift-XRT refined Analysis
- GRB 151027B: RATIR Late-Time Upper Limits
- GRB 151031A: Swift-BAT refined analysis
- GRB 151031A: Enhanced Swift-XRT position
- GRB 151031A: VLT/X-shooter optical counterpart and redshift
- GRB 151027A: optical follow-up observations
- GRB 151031A: Swift detection of a burst
- GRB 151027A: Continued P60 Monitoring
- LIGO/Virgo G194575: INAF-TNG follow-up of iPTF15dkm and iPTF15dlj
- Correction to the Trigger Time for Swift GRB 151029A
- GRB 151029A: MITSuME Ishigakijima upper limits
- GRB 151027A: Optical counterpart detection
- GRB 151029A: Swift-XRT refined Analysis
- GRB 151029A: Swift/UVOT Detection
- GRB 151029A: LCOGT-FTS afterglow observations
- GRB 151027B: Swift UVOT detection
- LIGO/Virgo G194575: VLA follow-up
- GRB 151029A: Swift-BAT refined analysis
- GRB 151029A: Enhanced Swift-XRT position
- GRB 151027A: MAXI/GSC detection
- GRB 151029A VLT/X-shooter redshift
- GRB 151029A: GROND afterglow observations
- GRB 151029A: Swift detection of a burst with an optical counterpart
- GRB 151027A: SAO RAS optical observations
- GRB 151027B: LCOGT FTN afterglow observations
- GRB 151027A: NOT optical and NIR observations
- GRB 151027A: T100 observations
- GRB 151027B: Swift/UVOT Upper Limits
- Konus-Wind observation of GRB 151027A
- GRB 151027A : Xinglong TNT optical observation
- GRB 151027B: Swift-BAT refined analysis
- GRB 151027A: continued GMG observation
- GRB 151027B: RATIR Observations
- GRB 151027B: MASTER-NET early OT detection
- GRB 151027A: LCOGT-McDonald afterglow observations
- GRB 151027B: Swift-XRT refined Analysis
- GRB 151027A: VLA detection
- GRB 151027B: GROND Optical/NIR Afterglow Detection
- GRB 151027B: VLT/X-shooter redshift
- GRB 151027B: Enhanced Swift-XRT position
- GRB 151027A: THO optical observations
- GRB 151027A: UVOT Observations
- GRB 151027B: NOT optical afterglow candidate
- LIGO/Virgo G194575 : RATIR Observation of La Silla - QUEST Candidate
- GRB 151027B: Swift detection of its 1000-th burst
- LIGO/Virgo O1 extended until January 12
- LIGO/Virgo G194575: iPTF Optical Transient Candidates
- GRB 151027A: Swift-BAT refined analysis
- GRB 151027A: Early RAPTOR Observations
- LIGO/Virgo G194575: MASTER Optical Inspection
- GRB 151027A: GMG observation
- GRB 151027A: Fermi GBM observation
- GRB 151027A: MITSuME Akeno Optical observation
- GRB 151027A: Swift-XRT refined Analysis
- LIGO/Virgo G194575: Swift observations of LSQ15bjb
- LIGO/Virgo G194575: INAF-TNG spectra of LSQ15bjb
- GRB 151027A: Keck/HIRES redshift
- LIGO/Virgo G194575: GROND multi-color observations
- GRB 151027A: Weihai optical observations
- LIGO/Virgo G194575: further Pan-STARRS observations of the RA=1hr localisation region
- Tentative redshift for GRB 151027A from Swift-XRT data
- GRB 151027A: Enhanced Swift-XRT position
- GRB 151027A: P60 afterglow confirmation and rebrightening
- GRB 151027A : ISON-NM early optical detection
- GRB 151027A: KAIT optical afterglow confirmation
- GRB 151027A: Swift detection of a burst with a bright optical afterglow
- LIGO/Virgo G194575: ASKAP followup
- LIGO/Virgo G194575: INAF-TNG follow-up of LSQ15bjb
- GRB 151006A: CALET Gamma-Ray Burst Monitor detection
- LIGO/Virgo G184098: VLA follow-up of iPTF15cyk
- LIGO/Virgo G194575 : La Silla - QUEST followup
- GRB 151021A: Skynet PROMPT-CTIO/DSO17 observations of the optical afterglow
- LIGO/Virgo G194575: Near-infrared follow-up with OAO-WFC
- LIGO/Virgo G194575: Kanata/J-GEM optical follow-up
- GRB 151023A: Swift-BAT refined analysis
- LIGO/Virgo G194575: Pi of the Sky observations
- LIGO/Virgo G194575: MAXI/GSC observations
- LIGO/Virgo G194575: Swift observations
- GRB 151022A: OSN optical upper limit
- GRB 151023A: RATIR Observations
- GRB 151023A: Swift-XRT refined Analysis
- GRB 151023A: Swift/UVOT Upper Limits
- GRB 151023A
- LIGO/Virgo G194575: CQUEAN/LOAO observations
- GRB 151023A: Enhanced Swift-XRT position
- Possible Fermi-LAT Gamma-ray counterpart for LIGO/Virgo G194575
- LIGO/Virgo G194575: LOFAR follow-up
- GRB 151022A: Swift/UVOT Upper Limits
- LIGO/Virgo G194575: RATIR Observations of Nearby Galaxies in the 1sigma Error Region
- LIGO Virgo G194575: MWA Observations
- LIGO/Virgo G194575: INTEGRAL search of temporally coincident prompt hard X-ray emission
- LIGO/Virgo G194575: RATIR Observations of Nearby Galaxies in the 1sigma Error Region
- GRB 151022A: Swift-BAT refined analysis
- LIGO/Virgo G194575: more details on transients from Pan-STARRS in the RA=1hr localisation region
- GRB 151023A: Swift detection of a burst
- GRB 151022A: RATIR Upper Limits
- GRB 151022A: Swift-XRT refined Analysis
- LIGO/Virgo G194575: Fermi GBM Observations
- GRB 151022A: MITSuME Okayama upper limits
- LIGO/Virgo G194575: Mini-MegaTORTORA observations