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"
17213 results found.
- GRB 250308A: CALET Gamma-Ray Burst Monitor detection
- GRB 250311B: SVOM detection of a burst
- GRB 250309B / AT2025dws: further SAO RAS optical observations
- EP250308a: 1.6m Mephisto optical upper limits
- Konus-Wind detection of GRB 250309B
- IPN triangulation of GRB 250308A (short)
- GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
- GRB 250309B / AT2025dws: SAO RAS optical observations
- AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
- GRB250309B: One candidate counterpart from the Zwicky Transient Facility
- IceCube-250309A: No candidates from the Zwicky Transient Facility
- Fermi-LAT gamma-ray observations of IceCube-250309A
- GRB 230509B: Tiled Swift observations
- EP250308a: Einstein Probe detection of an X-ray transient
- EP250308a: NOT optical upper limit
- EP250304a: MeerKAT detection of a possible radio counterpart
- GRB 250305A: AstroSat CZTI detection
- EP250302a:Xinglong optical observations
- GRB 250306A: AstroSat CZTI detection
- GRB250101A: Radio upper limits from VLA observations
- GRB 250305A: SVOM/GRM observation of a burst
- Fermi-LAT Gamma-ray Observations of IceCube-250302A
- EP250302a: Optical Observations at CrAO and SAO RAS
- GRB 250219A: SVOM/C-GFT optical upper limit at early phase
- EP 250304A: Optical counterpart detection by LCO
- EP250302A: 1.3m DFOT optical afterglow detection
- EP250304a: refined analysis of the EP-WXT and EP-FXT observations
- EP250304a: REM NIR upper limits
- EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
- EP250302a: Mondy Continued Optical Observations
- EP250304a: TRT optical counterpart detection
- EP250304a: Einstein Probe detection of an X-ray transient
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
- EP250302a: SAO RAS optical observations
- EP250302a : GIT optical follow-up
- EP250302a: Kinder optical follow-up observations
- EP250302a: Swift/UVOT detection
- EP250302a: optical observation from the INAF Asiago Observatory
- EP250302a: REM NIR upper limits
- EP250302a: Mondy Observations and Optical Light Curve
- EP250302a: VLT/MUSE optical redshift z = 1.131
- EP250302A: VLT near-infrared observations
- EP250302A: VLT/X-shooter tentative redshift
- EP250302a: OHP/T193 optical and spectroscopic observations
- EP250302a: Swift-XRT observations of a fading X-ray source
- EP250302a: Einstein Probe detection of an X-ray transient
- EP250302a: SVOM/C-GFT optical observations
- GRB 250226A: GRANDMA Optical Observations
- EP250302a: Montarrenti Observatory optical detection
- EP250302a: Nanshan/HMT optical counterpart detection
- LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
- GRB 250225B: VLT near-infrared afterglow confirmation
- EP250228a: Optical observations with Kinder and Swift/UVOT
- Konus-Wind detection of GRB 250226A
- GRB 250226A: KAO Optical Upper Limit
- GRB 250226A: AbAO AS-32 Optical Upper Limit
- EP250227a: TRT optical upper limit
- GRB 250225B: VLT/HAWKI near-infrared observations
- EP250227a: Optical upper limits with Kinder observations
- EP250227a: NOT optical observations
- EP250227a: Einstein Probe detected of a fast X-ray transient
- EP250228a: updates on the EP observations
- EP250223a: J band upper limit by SYSU 80cm telescope
- EP250228a: Einstein Probe detection of an X-ray transient
- GRB 250225B: VLT/Xshooter imaging
- GRB 250205A / EP250205A: further radio observations with the VLA
- EP250225a: NOT optical candidate counterpart
- EP250226a/GRB 250226A:Xinglong optical follow-up observations
- EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
- EP250225a: TRT optical upper limits
- EP250226a/GRB 250226A: 1.6m Mephisto observations
- EP250226a/GRB 250226A: Kinder optical follow-up observations
- LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
- GRB 250225B: REM NIR upper limits
- LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
- EP250223a: CrAO ZTSH optical observation
- GRB 250225B: VLT optical and near-infrared candidate counterpart
- GRB 250225B: SVOM/GRM observation of a long burst
- EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
- EP250226a / GRB 250226A: TRT optical counterpart observation
- EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
- EP250223a: GMG Optical Observation
- EP250225a: Einstein Probe detected of a fast X-ray transient
- EP250223a: GROWTH-India Telescope optical observations
- EP250215A: J band upper limit by SYSU 80cm telescope
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
- EP250223a: Kinder optical follow-up observations
- GRB 250222A: SVOM/GRM observation of a burst
- EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
- EP250223a: REM NIR upper limit
- EP250223a: TRT optical afterglow observation
- EP250223a: refined analysis of the EP-WXT and FXT observations
- EP250223a: 1.6m Mephisto and 50cm array observations
- LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
- EP250223a: OASDG optical observations
- EP250223a: NOT optical afterglow candidate
- EP250223a: Einstein Probe detection of an X-ray transient
- GRB 250221A: Optical counterpart detection by LCO.
- GRB 250219A: NUTTelA-TAO / BSTI Optical Limits