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"
24665 results found.
- EP250125a: Optical upper limit with Kinder observations
- EP250125a: REM optical counterpart detection
- GRB 250119C: Fermi GBM Observation
- EP250125a: Swift/XRT detection of a fading counterpart
- EP250125a: a new X-ray transient detected by Einstein Probe
- EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
- GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
- EP250108a: AbAO, CMO and Terskol optical upper limits
- GRB 250121A: Fermi GBM Observation
- IPN triangulation of GRB 250118B
- IPN triangulation of GRB 250119B
- GRB 250114A: Swift-BAT refined analysis
- LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
- GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
- GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
- Fermi-LAT Gamma-ray Observations of IceCube-241224A
- GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
- GRB 250119B: Fermi GBM Observation
- EP250108a/AT2025kg: 1.3m DFOT Optical observations
- IPN triangulation of GRB 250117A (short)
- LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
- EP 250108A: Late-time optical observation by LCO
- LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
- LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
- LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
- GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
- LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
- GRB 250117A: GECAM observation of a short burst
- LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
- GRB 250119B: BALROG localization (Fermi Trigger 758968026 / GRB 250119352)
- LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250118t: Updated Sky localization
- LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
- EP250108a / AT2025kg: GMG Optical Observations
- LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
- GRB 241217A / EP241217B: radio detection with the VLA
- GRB 250116A: Fermi GBM Observation of an Extremely Interesting Burst
- GRB 250114B: Swift-XRT afterglow detection
- EP250108a: MeerKAT radio upper limit
- LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
- GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
- LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
- IPN triangulation of GRB 250113A
- GRB 250114B: Liverpool Telescope optical upper limit
- LIGO/Virgo/KAGRA S250114ax: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
- GRB 250114B : MITSuME Akeno optical afterglow candidate detection
- GRB 250114B: Swift-XRT observations
- GRB 250114A: LCO optical counterpart detection.
- GRB 250114B: OHP/T193 optical upper limit
- GRB 250114A: GRANDMA/TAROT optical afterglow detection
- GRB 250114A: Swift-XRT refined Analysis
- GRB 250114A: LCOGT optical afterglow i-band detection
- GRB 250114B : GIT optical upper limit
- EP250111a: SAO RAS optical upper limit
- LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
- GRB 250114B: a short GRB detected with INTEGRAL
- GRB 250114A: Enhanced Swift-XRT position
- GRB 250114A: REM detection of the optical and NIR counterpart
- LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
- Swift GRB250114A: Global MASTER-Net OT detection
- GRB 250114A: LCO optical observations
- GRB 250114A: TRT optical observations
- GRB 250114A: Swift detection of a burst with an optical counterpart
- GRB 250101A: Terskol Zeiss-2000 optical observations
- EP250108a / AT 2025kg: SAO RAS optical observations
- EP241021a: SMA radio observation
- GRB 250113A: SVOM/GRM observation of a long burst
- GRB 250107A: VZLUSAT-2 detection
- EP250109b: optical upper limits with the Liverpool Telescope
- GRB 250106A: Swift-XRT afterglow detection
- EP250111a: KAIT optical observations
- GRB 250109A / EP250109a: Mephisto optical upper limits
- EP250108a: Mephisto detection
- EP250111a: Mondy optical observation
- EP250108a / AT 2025kg: LCO optical observations
- EP250108a / AT 2025kg: Swift UVOT detections
- EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
- EP250111a: NOT likely optical counterpart
- GRB 250101B: Fermi GBM Observation
- GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
- GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
- GRB 250108A: Swift/XRT afterglow fading
- LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
- LIGO/Virgo/KAGRA S250109f: Updated Sky localization
- LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
- EP-WXT trigger EP250108a:Xinglong optical follow-up observations
- GRB 250101A: CMO RC-500 optical observations
- GRB 250109A: Fermi GBM Observation
- EP250108a: NOT optical observations
- EP-WXT trigger EP250109a:Xinglong optical follow-up observations
- GRB 250109a: GMG Optical Upper Limit
- EP250109a: Swift/UVOT non-detection
- IPN triangulation of GRB 250107D (short/hard)
- EP250108a: Liverpool Telescope likely optical counterpart
- GRB 250108B: Swift-BAT refined analysis
- GRB 250108B: 1.3m DFOT upper limit
- GRB 250108B: REM optical/NIR upper limits