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"32485 results found.
- GRB 250129A: REM optical/NIR afterglow detection
- GRB 250129A: OHP/T193 optical and spectroscopy observations
- GRB 250129A: Early afterglow detection by LCO.
- GRB 250128B: OHP/T193 optical upper limit
- Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
- 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: Fermi GBM Observation
- 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
- GRB 250127A: EP-FXT afterglow detection
- Fermi GRB 250128A: Global MASTER-Net observations report
- GRB 250117A: Fermi GBM Observation
- Fermi GRB 250127B: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-250101A
- GRB 250127A: SVOM/VT upper limit
- IPN triangulation of GRB 250119C
- GRB 250127A: Swift ToO observations
- GRB 250127A: LCO optical upper limit
- GRB 241223A: cubesat Avion detection
- GRB 250126A: CALET Gamma-Ray Burst Monitor detection
- EP250125A: Non-detection from Fermi-GBM Observations
- GRB 250126A: MAXI/GSC detection
- EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
- GECAM-A detection of a bright burst from SGR 1E1841-045
- GRB 250118A: Fermi GBM Observation
- 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
- Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
- GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
- IPN triangulation of a bright burst from SGR 1E1841-045
- GRB 250121A: CALET Gamma-Ray Burst Monitor detection
- EP250108a: AbAO, CMO and Terskol optical upper limits
- Konus-Wind detection of GRB 250118B
- GRB 250121A: Fermi GBM Observation
- IPN triangulation of GRB 250118B
- Konus-Wind detection of GRB 250119B
- IPN triangulation of GRB 250119B
- Improved IPN triangulation of GRB 250107C
- GRB 250114A: Swift-BAT refined analysis
- GRB 250121A: INTEGRAL/SPI-ACS detection
- GRB 250121A: Fermi-LAT detection
- 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
- Konus-Wind detection of GRB 250117A
- IPN triangulation of GRB 250117A (short)
- 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
- GRB 250117A: SVOM/GRM observation of a short burst
- LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
- GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
- EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
- LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
- 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
- LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
- 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
- EP250108a / AT2025kg: VLA radio upper limit
- Konus-Wind detection of GRB 250116A
- GRB 250116A: GECAM-B detection of a long burst
- GRB 241217A / EP241217B: radio detection with the VLA
- GRB 250116A: INTEGRAL/SPI-ACS and PICsIT detection
- GRB 250116A: Fermi-LAT detection
- GRB 250114B: Swift-XRT afterglow detection
- GRB 250114B: SVOM/VT upper limit
- EP250108a: MeerKAT radio upper limit
- GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
- LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
- Konus-Wind detection of GRB 250113A
- 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 250114A: LCO optical counterpart detection.