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.
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"16161 results found.
- EP250223a: refined analysis of the EP-WXT and FXT observations
- EP250223a: 1.6m Mephisto and 50cm array observations
- GRB 250221A: TNOT detection of the optical counterpart
- EP250223a: SVOM/VT optical observation
- LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
- EP250223a: OASDG optical observations
- EP250223a: LCO detection of the afterglow
- EP250223a: early optical detection by BOOTES-4
- EP250223a: NOT redshift z = 2.756
- EP250223a: NOT optical afterglow candidate
- GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
- GRB 250221A: continued Mondy optical observations, brightening afterglow
- GRB 250221A: Optical counterpart detection by LCO.
- GRB 250221A: Mondy optical observations
- GRB 250221A: Assy optical observations
- EP250220a: FTW optical and NIR observations and upper limits
- GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
- GRB 250221A: VLT/X-shooter redshift z = 0.768
- GRB 250221A: GRANDMA/TAROT Detection
- GRB 250221A: NOT optical observations
- GRB 250221A: 1.6m Mephisto optical detection
- GRB 250221A: AKO Optical Upper Limit
- GRB 250221A: Swift/UVOT Detection
- EP250220a: Liverpool Telescope upper limits
- GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
- GRB 250221A: REM optical/NIR afterglow detection
- EP250220a: 1.6m Mephisto observations
- EP250220a: Liverpool Telescope optical upper limits
- EP250220a: Optical upper limit with Kinder observations
- GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
- GRB 250221A: Swift detection of a burst with an optical counterpart
- Swift GRB250221.15: Global MASTER-Net OT detection
- EP250220a: Xinglong optical upper limit
- GRB 250219A: OHP/T193 optical upper limit
- GRB 250219A: NOT optical observations
- GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
- GRB 250219A: 1.6m Mephisto optical upper limits
- GRB 250219A: SVOM/VT optical counterpart
- GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
- GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
- GRB 250217C: SVOM/GRM observation
- GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
- Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
- LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
- LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
- GRB 250215A / EP250215a: LCO detection of the afterglow
- EP250212a: FTW optical and NIR upper limits
- GRB 250215A: Swift/UVOT Upper Limits
- GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
- EP250215a / GRB 250215A : GTC redshift z = 4.61
- GRB 250215A: Fermi GBM Observation
- EP250215a / GRB 250215A : NOT optical observations
- GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
- GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
- LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
- GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
- GRB 250215A: Swift-XRT refined Analysis
- GRB 250215A: SVOM/GRM observation
- GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
- EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
- GRB 250213A:SVOM/VT optical candidate
- EP250207b: Xinglong optical upper limit
- EP250212a: Xinglong optical upper limit
- GRB 250205A: VIRT Optical Upper Limit
- GRB 250205A: Leavitt Observatory optical upper limit
- EP250207B: Chandra localization of the X-ray counterpart
- EP250212a: Liverpool Telescope optical upper limits
- GRB250101A: Radio upper limits from GMRT observations
- EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
- LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
- GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
- EP250207b: NOT optical counterpart candidate
- LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
- GRB 250205A / EP250205A: radio detection with the VLA
- LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
- LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
- GRB 250210A: SVOM/GRM observation of a long burst
- EP250207b: Liverpool Telescope possible optical counterpart
- Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
- GRB 250207A: Skynet optical afterglow observations
- GRB 241128A: VIRT Optical Upper Limit
- EP250207b: Gemini GMOS-N z-band observations
- LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
- GRB 250207A: 1.3m DFOT Optical observations
- LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
- GRB 250129A: GRANDMA Continued Afterglow Detection
- LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
- GRB 250205A: 1.3m DFOT optical upper limit
- LIGO/Virgo/KAGRA S250206dm: Spectroscopic Classification of AT2025bay and AT2025baz with Keck I/LRIS
- LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
- LIGO/Virgo/KAGRA S250206dm: ePESSTO+ classification of AT2025bar
- LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
- LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
- EP-WXT trigger 01709131361: correction to GCN 39214
- EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
- LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
- EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations
- GRB 250129A: ABObservatory SLOAN r’ afterglow detection
- GRB 250207A: REM IR afterglow detection