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.
Lucene Examples (click to copy):
subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
19139 results found.
- GRB 250129A: LCO optical observations
- GRB 250129A: NOT optical observations and redshift confirmation
- GRB 250129A: GOTO optical observations show brightening afterglow
- GRB 250129A: VLT/X-shooter redshift of z = 2.151
- Swift GRB 250129A: Global MASTER-Net observations report
- Fermi GRB 250128B: Global MASTER-Net observations report
- GRB 250128B: GOTO optical upper limit
- Swift GRB 250128B: Global MASTER-Net observations report
- EP250125a: Upper limits from Swift/BAT-GUANO
- GRB 250128B: LCO optical observations
- GRB 250127A: Swift-XRT observations
- GRB 250127B: DDOTI Upper Limit on the Afterglow
- Fermi-LAT Gamma-ray Observations of IceCube-250102A
- Fermi GRB 250128A: Global MASTER-Net observations report
- Fermi GRB 250127B: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-250101A
- GRB 250127A: SVOM/VT upper limit
- GRB 250127A: Swift ToO observations
- GRB 250127A: LCO optical upper limit
- EP250125A: Non-detection from Fermi-GBM Observations
- EP250125a: Optical upper limit with Kinder observations
- EP250125a: REM optical counterpart detection
- 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: INTEGRAL/SPI-ACS detection
- 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
- EP250108a/AT2025kg: 1.3m DFOT Optical observations
- ATCA detection of possible radio counterpart to GRB 250114A
- EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
- GRB 250119B: INTEGRAL/SPI-ACS detection
- 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 S250119cv: Updated NED Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
- GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
- EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
- EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
- EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
- GRB 250117A: GECAM observation of a short burst
- EP250108a / AT2025kg: GMG Optical Observations
- EP250108a / AT2025kg: VLA radio upper limit
- GRB 241217A / EP241217B: radio detection with the VLA
- GRB 250116A: INTEGRAL/SPI-ACS and PICsIT detection
- GRB 250114B: Swift-XRT afterglow detection
- GRB 250114B: SVOM/VT upper limit
- 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.
- 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 250114A: GRANDMA/TAROT optical afterglow detection
- Integral GRB250114.55: Global MASTER-Net observations report
- GRB 250114A: LCOGT optical afterglow i-band detection
- GRB 250114B: Swift ToO observations
- LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
- GRB 250113A: INTEGRAL/SPI-ACS detection
- GRB 250114A: REM detection of the optical and NIR counterpart
- GRB 250114A: LCO optical observations
- GRB 250114A: TRT optical observations
- Swift GRB 250114A: Global MASTER-Net observations report
- GRB 250101A: Terskol Zeiss-2000 optical observations
- EP250108a / AT 2025kg: SAO RAS optical observations
- EP241021a: SMA radio observation
- EP250109b: optical upper limits with the Liverpool Telescope
- GRB 250106A: Swift-XRT afterglow detection
- Fermi trigger No 758442826: Global MASTER-Net observations report
- EP250111a: KAIT optical observations
- GRB 250109A / EP250109a: Mephisto optical upper limits
- EP250108a: Mephisto detection
- EP250111a: Mondy optical observation
- EP250108a / AT 2025kg: LCO optical observations
- EP250111a: Global MASTER-Net observations report
- EP250108a / AT 2025kg: Swift UVOT detections
- EP250108a: optical follow-up observations with the Liverpool Telescope
- EP250111a: NOT likely optical counterpart
- EP250111a: a new X-ray transient detected by Einstein Probe
- EP250109a/GRB 250109A:SVOM/VT optical counterpart
- EP250108a: further NOT optical observations
- 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
- EP-WXT trigger EP250108a:Xinglong optical follow-up observations
- GRB 250101A: CMO RC-500 optical observations
- EP250108a: NOT optical observations
- EP-WXT trigger EP250109a:Xinglong optical follow-up observations
- EP250109a: Swift/UVOT non-detection
- EP250108a: Liverpool Telescope likely optical counterpart
- GRB 250108B: Gemini-North likely redshift z = 2.197
- GRB 250108B: 1.3m DFOT upper limit
- GRB 250108B: REM optical/NIR upper limits