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"27775 results found.
- GRB 251125B: GECAM-B detection
- GRB 251127A: Fermi GBM Final Real-time Localization
- GRB 251126A: Enhanced Swift-XRT position
- GRB 251126A: Kilonova-Catcher optical afterglow detection
- GRB 251126A: Asiago i-band detection
- GRB 251126A: Nanshan/HMT optical afterglow detection
- Swift GRB 251126A: Global MASTER-Net observations report
- GRB 251121A: Fermi GBM Observation
- GRB 251126A: Prompt enhanced Swift-XRT position
- GRB 251126A: GIT discovery of the likely optical afterglow
- GRB 251126A: Swift detection of a burst
- Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
- GRB 251125B: Fermi GBM Final Real-time Localization
- EP251124b: EP-WXT detection of a fast X-ray transient
- EP251124a: Xinglong GWAC-F60A optical observation
- GRB 251125A: Fermi GBM Final Real-time Localization
- EP251124a: NOT r- and z-band optical upper limits
- EP251124a: Swift-XRT observations
- GRB 251124A: Fermi GBM Localization by automated pipeline
- LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
- GRB 251122B: Fermi GBM Final Localization
- EP251118A: 6 GHz VLA Detection
- GRB 251124a: Fermi GBM Final Localization
- LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
- LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
- EP251124a: Einstein Probe detection of an X-ray transient
- GRB 251116C: Swift-XRT confirmation of fading
- GRB 251122A/EP251122A: 1.3m DFOT optical detection
- EP251118A: 3.6m DOT optical afterglow detection
- GRB 251122A / EP251122a: EP-FXT counterpart detection
- GRB 251122A / EP251122a: WFST optical observations
- GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
- GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
- EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
- GRB 251122A / EP251122a: SVOM detection of a long burst
- EP251122a: Einstein Probe detection of an X-ray transient
- EP251118a: Continued Optical Detection with Kinder observations
- LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
- GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
- GRB 251121A: Glowbug gamma-ray detection of a likely short burst
- GRB 251121A: Fermi GBM Final Real-time Localization
- EP251118A: 1.3m DFOT optical afterglow detection
- GRB 251118A: Swift/UVOT Detection
- GRB 251118A: Glowbug gamma-ray detection
- GRB 251118A: Fermi GBM Observation
- GRB 251118A: Swift-XRT afterglow detection
- GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
- EP251118a: Optical detection with Kinder observations
- GRB 251118A: GECAM-B detection
- GRB 251118A: NuSTAR detection of bright prompt emission
- EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
- GRB 251116C: NOT optical observations
- GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
- GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
- GRB 251018A: FRAM-Auger optical detection
- GRB 251117A: Swift-XRT observations
- Konus-Wind detection of GRB 251118C (EP251118a)
- GRB 251117A: Insight-HXMT/HE detection
- EP251118a: GOTO optical afterglow detection
- GRB 251119A: SVOM detection of a possible burst
- GRB 251118A: Fermi-LAT detection
- GRB 251118A: Swift ToO observations
- EP251118a: Einstein Probe detected of a fast X-ray transient
- GRB 251118B: Fermi GBM Final Real-time Localization
- GRB 251117A: FTW Observations of Swift candidate X-ray sources
- GRB 251118A: Fermi GBM Final Real-time Localization
- GRB 251116C: SVOM/ECLAIRs refined analysis
- GRB 251117A: AstroSat CZTI detection
- GRB 251114B: Insight-HXMT/HE detection
- GRB 251114B: GECAM-B detection of a short burst
- GRB 251117A: Fermi GBM observation
- GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
- GRB 251116D: Insight-HXMT/HE detection
- GRB 251115A: Swift-XRT observations
- GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
- GRB 251117A: Tiled Swift observations
- GRB 251117A: Fermi-LAT detection
- GRB 251116C: Swift/BAT arcminute localization of a burst
- LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
- GRB 251116C: Swift-XRT observations
- GRB 251117A: Fermi GBM Final Localization Correction
- GRB 251116D: Glowbug gamma-ray detection
- GRB 251116D: AstroSat CZTI detection
- GRB 251116C: SVOM/VT optical upper limit
- GRB 251116C: SVOM detection of a burst
- GRB 251116B: SVOM detection of a burst
- GRB 251116A: Fermi GBM Final Real-time Localization
- GRB 251115A: Tiled Swift observations
- GRB 251115A: Fermi-LAT detection
- GRB 251115A: Fermi GBM Final Real-time Localization
- GRB 251113A: Glowbug gamma-ray detection
- GRB 251113A: AstroSat CZTI detection
- GRB 251114B: Fermi GBM Final Real-time Localization
- GRB 251112A: Swift-BAT refined analysis
- Konus-Wind detection of GRB 251108C
- Konus-Wind detection of GRB 251103A
- LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
- LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
- IPN triangulation of GRB 251108C
- GRB 251114A: Fermi GBM Final Real-time Localization