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').
18787 results found.
- GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
- GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
- EP250108a/AT2025kg: 1.3m DFOT Optical observations
- Konus-Wind detection of GRB 250117A
- IPN triangulation of GRB 250117A (short)
- EP 250108A: Late-time optical observation by LCO
- LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
- 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: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
- 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
- Konus-Wind detection of GRB 250116A
- GRB 241217A / EP241217B: radio detection with the VLA
- GRB 250116A: Fermi-LAT detection
- GRB 250114B: Swift-XRT afterglow detection
- EP250108a: MeerKAT radio upper limit
- GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
- Konus-Wind detection of GRB 250113A
- IPN triangulation of GRB 250113A
- GRB 250114B: Liverpool Telescope optical upper limit
- GRB 250114B : MITSuME Akeno optical afterglow candidate detection
- GRB 250114A: LCO optical counterpart detection.
- GRB 250114B: OHP/T193 optical upper limit
- GRB 250114A: GRANDMA/TAROT optical afterglow detection
- GRB 250114A: LCOGT optical afterglow i-band detection
- GRB 250114B : GIT optical upper limit
- EP250111a: SAO RAS optical upper limit
- 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 250109A / EP250109a: GRBAlpha detection
- GRB 250107D: GRBAlpha detection
- 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
- EP250111a: Swift/XRT detection and fading
- 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 250109A / EP250109a: Swift detection of the X-ray afterglow
- Konus-Wind detection of GRB 250107C
- EP-WXT trigger EP250108a：Xinglong optical follow-up observations
- GRB 250101A: CMO RC-500 optical observations
- EP250108a: EP-FXT follow-up 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
- Konus-Wind detection of GRB 250107D (short/hard)
- IPN triangulation of GRB 250107D (short/hard)
- EP250108a: Liverpool Telescope likely optical counterpart
- GRB 250108B: 1.3m DFOT upper limit
- GRB 250108B: REM optical/NIR upper limits
- EP250109a: Global MASTER-Net observations report
- GRB 250101A: Terskol K-800 optical observations
- EP250109a: Swift/XRT non-detection
- GRB 250108A: Swift/UVOT Upper Limits
- LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
- GRB 250108A: NOT optical upper limit
- EP250108a: EP-WXT detection of an X-ray transient
- LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
- GRB 250103A: 1.6m Mephisto optical observations
- GRB 250108A: Swift-XRT afterglow detection
- LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
- GRB 250108B: Swift/UVOT Upper Limits
- GRB 250103A: Swift-XRT afterglow detection
- GRB 250108B: Enhanced Swift-XRT position
- GRB 250108B: Swift detection of a burst
- GRB 250108A: SVOM detection of a soft long burst
- GRB 241228B: Fermi-LAT detection
- GRB 250101A: J band upper limit by SYSU 80cm telescope
- EPWXT01709129925: Xinglong optical observations
- GRB 250106A: NOT optical observations
- GRB 250103B: REM optical/NIR upper limits
- GRB 250101A: REM optical/NIR counterpart detection
- GRB 250106A: SVOM detection of a long burst
- GRB 250103B: Swift-XRT refined Analysis
- GRB 250103B: LCO/1m optical afterglow candidate detection
- GRB 250103A: Bassano Bresciano Observatory upper limit
- GRB 250101A: 1.3m DFOT optical afterglow detection
- GRB 241229A: 1.3m DFOT upper limit
- GRB 241228B: 1.3m DFOT Optical observations
- GRB 241228A: 1.3m DFOT upper limit