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.
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').
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"28251 results found.
- EP 250321A: Optical counterpart detection by LCO.
- EP250321a: Kinder optical follow-up observations
- GRB 250321A: Swift/UVOT Upper Limits
- GRB 250320B: SVOM/GRM observation of a long burst
- EP250321a: LCO optical counterpart detection
- EP250321a: Swift-XRT detection of an X-ray source
- EP250321A: COLIBRÍ Optical Observations
- GRB 250320B: AstroSat CZTI detection
- EP250321a: REM optical/NIR afterglow detection
- EP250321a: TRT optical counterpart detection
- Swift GRB 250321A: Global MASTER-Net observations report
- EP250321a: Einstein Probe detection of an X-ray transient
- GRB 250321A: GOTO optical upper limits
- GRB 250314A: Keck/NIRC2 J-band upper limit
- EP250226a/GRB 250226A: KAIT optical observations
- GRB 250321A: Fermi GBM Observation
- GRB 250321A: Swift detection of a burst
- GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
- GRB 250317B: Mondy AZT-33IK Continued Optical Observations
- FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
- LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
- GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
- GRB 250317D: EIRSAT-1 GMOD Detection
- LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
- GRB 250314A: ATCA radio upper limits
- GRB 250317B: OHP/T193 continued follow-up
- LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
- GRB 250317C: SVOM/GRM observation of a long burst
- GRB 250317B: Leavitt Observatory optical upper limit
- GRB 250317B: Mondy AZT-33IK Optical Observations
- GRB 250317B: NOT optical observations suggest an optical plateau phase
- GRB 250317C: GECAM-B detection
- GRB 250317B: OHP/T193 optical observations
- GRB250312A: Swift/UVOT Upper Limits
- GRB 250317B: REM optical/NIR observations
- GRB 250317B: Swift-XRT observations
- GRB 250316A: Swift/UVOT Upper Limits
- GRB 250314A: REM optical/NIR upper limits
- GRB 250316A: AbAO AS-32 Optical Upper Limit
- EP 250317B: Fading optical counterpart detection by LCO
- GRB 250316A: Swift-XRT afterglow detection
- GRB 250317B: LCO detection of the fading optical afterglow
- GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
- GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
- GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
- GRB 250317B: SVOM detection of a burst
- GRB 250316A: Fermi GBM Observation
- GRB 250316A: Swift-XRT observations
- GRB 250314A: SVOM/GRM analysis
- GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
- GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
- GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
- GRB 250314A: EP-FXT afterglow detection
- EP250315a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250314A: Swift/UVOT Upper Limits
- GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
- GRB 250314A: Swift XRT Detection
- EP250315a: optical counterpart candidate detected by Gemini North
- GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
- EP250315a: Einstein Probe detection of an X-ray transient
- GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
- SVOM/MXT upper limit on GRB 250314A
- GRB 250314A: SVOM/VT upper limit
- GRB 250314A: NOT near-infrared candidate counterpart
- GRB 250313A: Fermi GBM Detection
- GRB 250312B: Fermi GBM Observation
- GRB 250313A: Swift-XRT observations
- GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
- GRB 250314A: SVOM detection of a burst
- GRB 250313A: AstroSat CZTI detection of a bright long burst
- IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
- GRB 250313A: Fermi-LAT detection
- EP250304a: Pan-STARRS r and i-band imaging and photometry
- GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
- GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
- GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
- ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
- GRB 250312A: Swift-XRT refined Analysis
- GRB 250312A: Enhanced Swift-XRT position
- LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
- GRB 250226B: Fermi GBM Observation
- GRB 250302A: Fermi GBM Observation
- GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
- GRB 250312A: Swift detection of a burst
- GRB 241213A: VIRT Optical Upper Limit
- GRB 241228A: VIRT Optical Upper Limit
- GRB 250311A/EP250311a: Optical upper limits with Kinder observations
- GRB 250311A: Swift-XRT observations
- GRB 250309B: 1.3m DFOT Optical observations
- IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
- GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
- GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
- GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
- GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
- GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
- GRB 250309B: PRIME near-infrared detection
- GRB 250225B: Swift-BAT refined analysis
- GRB 250311A/EP250311a: TRT optical upper limit
- EP250311a/GRB 250311A: EP-WXT detection