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"28103 results found.
- GRB 250309B: Swift-XRT refined Analysis
- GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
- Liverpool Telecope observations of AT 2025dws / GRB 250309B
- GRB 250309B / AT2025dws: SAO RAS optical observations
- GRB 250309B / AT2025dws: Swift-UVOT detection
- 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 250308A: SVOM/GRM detection of QPO in the tail emission
- GRB 250309B: Fermi GBM Final Localization
- Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
- GRB 230509B: Tiled Swift observations
- IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
- EP250308a: GSP optical upper limit
- EP250308a: Einstein Probe detection of an X-ray transient
- GRB 250309A: Fermi GBM Final Real-time Localization
- GRB 250306A: EIRSAT-1 GMOD detection
- Konus-Wind detection of GRB 250306A
- GRB 250307A: Fermi GBM Final Real-time Localization
- GRB 250306A: NuSTAR detection of the prompt emission
- EP250304a: MeerKAT detection of a possible radio counterpart
- GRB 250305A: AstroSat CZTI detection
- GRB 250306A: AstroSat CZTI detection
- GRB 250306A: Swift detection of a burst
- LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
- GRB 250305A: Fermi GBM Final Real-time Localization
- 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
- Konus-Wind detection of GRB 250222A
- EP250304a: REM NIR upper limits
- IPN triangulation of GRB 250222A
- EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
- EP250304a: Swift-XRT detection of a fading X-ray source
- 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
- EP250225a: the candidate optical counterpart is an AGN
- EP250302a: Swift/UVOT detection
- EP250302a: NUTTelA-TAO Early Measurments
- EP250302a: REM NIR upper limits
- EP250302a: Xinglong F60B optical observation
- EP250302a: Swift-XRT observations of a fading X-ray source
- EP250302a: Einstein Probe detection of an X-ray transient
- GRB 250226A: GRANDMA Optical Observations
- EP250302a: Montarrenti Observatory optical detection
- EP250302a: FTW optical and NIR detection
- EP250302a: Nanshan/HMT optical counterpart detection
- IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 250302A: Fermi GBM Final Real-time Localization
- GRB 250228A: Fermi GBM Final Localization
- GRB 250225B: VLT near-infrared afterglow confirmation
- EP250228a: Optical observations with Kinder and Swift/UVOT
- Konus-Wind detection of GRB 250226A
- GRB 250225B: EIRSAT-1 GMOD Detection
- GRB 250225B: VLT/HAWKI near-infrared observations
- EP250227a: Optical upper limits with Kinder observations
- EP250227a: Einstein Probe detected of a fast X-ray transient
- EP250228a: updates on the EP observations
- EP250225a: EP-FXT follow-up observation
- EP250223a: J band upper limit by SYSU 80cm telescope
- EP250228a: Swift/XRT localisation
- EP250228a: Einstein Probe detection of an X-ray transient
- GRB 250226A / EP250226a: LCO detection of the afterglow
- GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
- EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
- GRB 250225B: INTEGRAL SPI-ACS detection
- EP250226a / GRB 250226A: SVOM/VT optical observations
- EP250225a: TRT optical upper limits
- LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
- LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
- LIGO/Virgo/KAGRA S250227y: Retraction of GW compact binary merger candidate
- GRB 250226B: Fermi GBM Final Real-time Localization
- GRB 250221A: ATCA Detections and Upper Limits
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
- Konus-Wind detection of GRB 250225B
- LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
- GRB 250225B: VLT optical and near-infrared candidate counterpart
- GRB 250225B: VLT/FORS2 candidate optical afterglow
- GRB 250226A: GECAM-B detection
- GRB 250221A: EP-FXT detection of the X-ray afterglow
- EP250226a/GRB 250226A: GSP detects optical counterpart
- EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
- EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
- LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
- EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
- GRB 250226A: Fermi GBM Final Real-time Localization
- EP250225a: GSP optical upper limit
- EP250225a: Einstein Probe detected of a fast X-ray transient
- GRB 250225B: Swift detection of a burst
- EP250223a: GROWTH-India Telescope optical observations
- EP250215A: J band upper limit by SYSU 80cm telescope
- GRB 250225A: Fermi GBM Final Real-time Localization
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
- GRB 250207a: ATCA Radio Upper Limits
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
- GRB 250119B: VZLUSAT-2 detection
- GRB 250223C: Fermi GBM Final Real-time Localization
- GRB 250202B: VZLUSAT-2 detection