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"
24658 results found.
- 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
- GRB 250311B: SVOM detection of a burst
- GRB 250311A/MAXI J1457-026: MAXI/GSC detection
- 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)
- IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
- GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
- GRB 250309B: Swift-XRT refined Analysis
- GRB 250309B / IceCube-250309A: GECAM-B observations
- GRB 250309B / AT2025dws: SAO RAS optical observations
- AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
- GRB 250309B: Fermi GBM Observation
- 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
- IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
- EP250308a: GSP optical upper limit
- EP250308a: Einstein Probe detection of an X-ray transient
- EP250308a: NOT optical upper limit
- GRB 250306A: EIRSAT-1 GMOD detection
- GRB 250306A: Swift-BAT refined analysis
- GRB 250306A: NuSTAR detection of the prompt emission
- EP250304a: MeerKAT detection of a possible radio counterpart
- IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
- GRB 250305A: AstroSat CZTI detection
- EP250302a:Xinglong optical observations
- LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
- GRB250101A: Radio upper limits from VLA observations
- GRB 250305A: SVOM/GRM observation of a burst
- The EP-WXT trigger 01709132323 is likely a flaring star
- EP250304A: Upper limits from Fermi-GBM Observations
- 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
- IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
- 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: Swift-XRT detection of a fading X-ray source
- EP250304a: TRT optical counterpart detection
- LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
- 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
- EP250225a: the candidate optical counterpart is an AGN
- EP250302a: Kinder optical follow-up observations
- LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
- EP250302a: Swift/UVOT detection
- EP250302a: optical observation from the INAF Asiago Observatory
- EP250302a: REM NIR upper limits
- IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
- 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 250225B: EIRSAT-1 GMOD Detection
- GRB 250226A: KAO Optical Upper Limit
- GRB 250226A: AbAO AS-32 Optical Upper Limit
- EP250227a: Global MASTER-Net observations report
- EP250223A: Upper limits from Fermi-GBM Observations
- 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
- GRB 250226A: Fermi GBM 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
- LIGO/Virgo/KAGRA S250227e: Updated Sky localization
- LIGO/Virgo/KAGRA S250226dl: Updated Sky localization