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"32485 results found.
- Konus-Wind detection of GRB 250308A
- EP250311a/GRB 250311A: Correction to EP-WXT detection time
- GRB 250313A: SVOM/GRM observation of a bright long burst
- FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
- 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
- GRB 250313A: Swift ToO observations
- EP250304a: Pan-STARRS r and i-band imaging and photometry
- GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
- EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
- Fermi GRB 250313A: Global MASTER-Net observations report
- GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
- EP250304a: SVOM/VT optical observation
- EP250311a/GRB 250311A: EP-FXT follow-up observation
- ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
- EP250302a: Chandra X-ray Detection
- Fermi GRB 250312B: Global MASTER-Net observations report
- GRB 250226B: Fermi GBM Observation
- Swift GRB 250312A: Global MASTER-Net observations report
- GRB 250302A: Fermi GBM Observation
- GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
- GRB 241213A: VIRT Optical Upper Limit
- GRB 241228A: VIRT Optical Upper Limit
- GRB 250311A/EP250311a: Optical upper limits with Kinder observations
- GRB 250223B: Fermi GBM Observation
- GRB 250311A: Swift-XRT observations
- GRB 250228A: Fermi GBM Observation
- GRB 250309B: 1.3m DFOT Optical observations
- IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
- EP250311a: Global MASTER-Net observations report
- 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
- EP250304a: Chandra detection
- GRB 250225B: Swift-BAT refined analysis
- GRB 250311A/EP250311a: TRT optical upper limit
- IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
- GRB 250311A: Tiled Swift observations
- EP250311a/GRB 250311A: EP-WXT detection
- GRB 250308A: CALET Gamma-Ray Burst Monitor detection
- GRB 250309B: SVOM/VT optical observation
- GRB 250309B / AT2025dws: further SAO RAS optical observations
- IceCube-250309A: Upper limits from Fermi-GBM Observations
- EP250308a: 1.6m Mephisto optical upper limits
- Konus-Wind detection of GRB 250309B
- GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
- IPN triangulation of GRB 250308A (short)
- IPN triangulation of GRB 250309B
- 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: 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
- GRB 250309B: Fermi GBM Observation
- Fermi GRB 250309B: Global MASTER-Net observations report
- Fermi GRB 250309A: Global MASTER-Net observations report
- 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
- 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: Global MASTER-Net observations report
- EP250308a: GSP optical upper limit
- GRB 250306A: EIRSAT-1 GMOD detection
- Fermi GRB 250307A: Global MASTER-Net observations report
- Konus-Wind detection of GRB 250306A
- 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
- GRB 250306A: AstroSat CZTI detection
- Swift GRB 250306A: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
- GRB250101A: Radio upper limits from VLA observations
- GRB 250305A: SVOM/GRM observation of a burst
- EP250304A: Upper limits from Fermi-GBM Observations
- Fermi GRB 250305A: Global MASTER-Net observations report
- 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
- Konus-Wind detection of GRB 250222A
- EP250304a: REM NIR upper limits
- IPN triangulation of GRB 250222A