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').
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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"32493 results found.
- IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
- LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
- EP250827b: Liverpool Telescope observations
- GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
- GRB 250902A: SVOM/GRM observation
- EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
- EP250901a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250901A: EP-FXT follow-up observation
- GRB 250901A: NOT optical observations
- GRB 250901A: SVOM/VT optical afterglow with VHF data
- LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
- GRB 250901A: LCO optical upper limit
- EP250827b: Swift observations of AT 2025wkm
- LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
- EP250827b: Gemini Spectroscopy of AT 2025wkm
- LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
- EP250831a: NOT optical observations and tentative afterglow candidate
- EP250827b: FTW Observations of AT 2025wkm
- EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
- GRB 250830C: Insight-HXMT detection
- EP250901a: Mephisto optical upper limits
- EP250901a: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250830m: Updated Sky localization
- EP250831a: EP-FXT follow-up observation
- EP250831a: Swift-XRT observations
- EP250831a: Global MASTER-Net observations report
- GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
- GRB 250831A: Swift-XRT counterpart detection
- GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250831A: SVOM/VT upper limit with VHF data
- EP250830a: Global MASTER-Net observations report
- EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
- LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
- LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
- LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
- LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
- EP-WXT trigger 01709200994: Liverpool Telescope upper limits
- GRB 250830B: Swift ToO observations
- LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
- GRB 250828B: Swift-BAT refined analysis
- EP250821a: SOAR observations
- EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
- LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
- LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
- EP250828a: refined analysis of the EP-WXT and EP-FXT observations
- EP250828a: Optical counterpart detection with Kinder observations
- EP250828a: Liverpool Telescope upper limits
- Swift GRB 250828B: Global MASTER-Net observations report
- EP250828a: Global MASTER-Net observations report
- EP-WXT trigger 01709200800 : KAIT optical observations
- EP250828a: KAIT optical upper limit
- EP250827a: Swift/UVOT Detection
- EP250828a: NOT optical counterpart confirmation
- EP250828a: SVOM/VT optical candidate
- EP250828a: Seimei/TriCCS optical counterpart detection
- EP250827a: STEP/T80S Confirmation of fading optical counterpart
- EP250828a: Optical upper limit with Kinder observations
- LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
- LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
- EP250827a: LCO observations show fading optical counterpart
- EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
- GRID detection of GRB 250824A
- LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
- EP250827A: VLT/X-shooter redshift confirmation
- Fermi GRB 250827A: Global MASTER-Net observations report
- EP250827a: confirmation of optical rebrightening with LCO
- EP250827a: GOTO observation of the optical afterglow
- GRB 250826A: SVOM/GRM observation
- EP250827A: An optical rebrightening was detected by LCO.
- EP250827a: Swift-XRT counterpart detection
- LIGO/Virgo/KAGRA S250827l: Updated Sky localization
- EP250827a: TRT optical observations
- EP250827a / GRB 250827A: MASTER-OAFA OT observation
- EP250827a: Gemini-South redshift z = 1.613
- EP250827a: Global MASTER-Net observations report
- EP250827a: Las Cumbres independent detection of the optical counterpart
- EP250827a: Gemini-South optical counterpart detection
- LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
- Fermi GRB 250826A: Global MASTER-Net observations report
- GRB 250806A: HiPERCAM/GTC limits on a possible supernova
- EP250821a: Gemini GMOS Redshift Confirmation
- LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
- LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
- Fermi GRB 250824B: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
- LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
- LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
- GRB 250823A: Swift-BAT refined analysis
- LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
- GRB 250821B: AstroSat CZTI detection
- GRB 250819A: AstroSat CZTI detection
- LIGO/Virgo/KAGRA S250818k: FTW Observations Show Continued Reddening of AT 2025ulz
- LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
- GRB 250821B: Insight-HXMT detection
- LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
- EP250821a: MeerKAT radio counterpart
- EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars
- LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
- GRB 250823A: COLIBRÍ optical observations
- GRB 250823A: SVOM/VT optical observation