GCN Circulars
GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"32561 results found.
- 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
- GRB 250823A: Swift/UVOT Detection
- GRB 250823A: NOT optical observations
- LIGO/Virgo/KAGRA S250818k: CFH/MegaCam follow-up observation for AT2025ulz
- LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
- GRB 250823A: Fermi GBM Observation
- GRB 250818B: MeerKAT Detection
- GRB 250823A: LCOGT Optical Detection
- GRB 250823A: BOOTES6/DPRT early optical detection
- GRB 250823A: Liverpool Telescope optical detection
- Konus-Wind detection of GRB 250821B
- LIGO/Virgo/KAGRA S250818k: Rebrightening detected with Gemini/GMOS
- LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
- LIGO/Virgo/KAGRA S250818k: J-GEM follow-up observation for AT2025ulz
- LIGO/Virgo/KAGRA S250818k: PRIME nIR observations of AT2025ulz
- LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
- LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
- LIGO/Virgo/Kagra S250818k: STEP/T80N upper limits on 2025ulz
- LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
- GRB 250806A: Gemini observations of host galaxy candidate
- IPN triangulation of GRB 250821B (long/bright)
- GRB 250821A: Kilonova-Catcher optical upper limits
- EP250821a: Swift/XRT counterpart fading
- GRB 250812A: SVOM/ECLAIRs refined analysis
- GRB 250821A: Swift-BAT refined analysis
- LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
- LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
- EP250821a: Swift/UVOT further observations.
- EP250821a: VLT X-shooter spectroscopic redshift z = 0.577
- LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
- GRB 250821A: VLT/FORS2 Optical Observation
- GRB 250821A: GECAM-B detection
- GRB 250821B: SVOM/GRM observation