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"
6094 results found.
- GRB 250327A: Fermi GBM observation
- Konus-Wind detection of GRB 250322A (short)
- Swift follow-up observations of FRB250316A and EP J120944.2+585060
- FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
- EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
- GRB 250321B: Swift-XRT observations
- GRB 250322A: Swift-XRT refined Analysis
- GRB 250322A: NOT optical upper limits
- FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
- FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
- EP250321a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250320B: Fermi GBM Observation
- GRB 250321A: Swift-XRT refined Analysis
- GRB 250320B: Fermi-LAT detection
- EP250321a: Kinder optical follow-up observations
- EP250321a: Swift-XRT detection of an X-ray source
- EP250321a: TRT optical counterpart detection
- GRB 250321A: Swift-XRT localisation
- GRB 250321A: Fermi GBM Observation
- GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
- GRB 250317B: NOT optical observations suggest an optical plateau phase
- GRB 250317B: Swift-XRT observations
- GRB 250316A: Swift/UVOT Upper Limits
- EP 250317B: Fading optical counterpart detection by LCO
- GRB 250316A: Swift-XRT afterglow detection
- GRB 250317B: LCO detection of the fading optical afterglow
- GRB 250316A: Fermi GBM Observation
- GRB 250316A: Swift-XRT observations
- GRB 250314A: Swift/UVOT Upper Limits
- GRB 250314A: SVOM/VT upper limit
- GRB 250313A: Fermi GBM Detection
- GRB 250312B: Fermi GBM Observation
- GRB 250313A: Swift-XRT observations
- GRB 250313A: Fermi-LAT detection
- EP250302a: Chandra X-ray Detection
- GRB 250312A: Swift-XRT refined Analysis
- GRB 250226B: Fermi GBM Observation
- GRB 250302A: Fermi GBM Observation
- 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 / AT2025dws: further SAO RAS optical observations
- Konus-Wind detection of GRB 250309B
- GRB 250309B: Swift-XRT refined Analysis
- GRB 250309B / IceCube-250309A: GECAM-B observations
- GRB 250309B / AT2025dws: SAO RAS optical observations
- GRB 250309B: Fermi GBM Observation
- Fermi GRB 250309A: Global MASTER-Net observations report
- Fermi-LAT gamma-ray observations of IceCube-250309A
- EP250308a: Einstein Probe detection of an X-ray transient
- EP250308a: NOT optical upper limit
- Fermi trigger No 762963055: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-250302A
- EP250302a: Optical Observations at CrAO and SAO RAS
- EP250302A: 1.3m DFOT optical afterglow detection
- EP250304a: refined analysis of the EP-WXT and EP-FXT observations
- EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
- EP250304a: Swift-XRT detection of a fading X-ray source
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
- EP250302a: SAO RAS optical observations
- EP250302a: Kinder optical follow-up observations
- EP250302a: NUTTelA-TAO Early Measurments
- EP250302a: Swift-XRT observations of a fading X-ray source
- EP250228a: Optical observations with Kinder and Swift/UVOT
- Konus-Wind detection of GRB 250226A
- EP250227a: TRT optical upper limit
- GRB 250225B: VLT/HAWKI near-infrared observations
- EP250227a: Optical upper limits with Kinder observations
- GRB 250226A: Fermi GBM Observation
- EP250225a: EP-FXT follow-up observation
- GRB 250226A / EP250226a: LCO detection of the afterglow
- EP250225a: TRT optical upper limits
- EP250226a/GRB 250226A: 1.6m Mephisto observations
- EP250226a/GRB 250226A: Kinder optical follow-up observations
- GRB 250221A: EP-FXT detection of the X-ray afterglow
- EP250226a / GRB 250226A: TRT optical counterpart observation
- LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
- Fermi GRB 250226A: Global MASTER-Net observations report
- EP250223a: Kinder optical follow-up observations
- EP250223a: 1.6m Mephisto and 50cm array observations
- EP250223a: LCO detection of the afterglow
- EP250223a: NOT optical afterglow candidate
- Konus-Wind detection of GRB 250221A
- EP250220a: EP-FXT follow-up observations
- GRB 250221A: Swift-XRT refined Analysis
- GRB 250221A: 1.6m Mephisto optical detection
- EP250220a: 1.6m Mephisto observations
- EP250220a: Optical upper limit with Kinder observations
- GRB 250219A: Swift/UVOT Upper Limits
- GRB 250219A: NOT optical observations
- GRB 250219A: Swift-XRT observations
- Konus-Wind detection of GRB 250215A / EP250215a
- GRB 250217C: Swift-XRT observations
- GRB 250217C: Fermi GBM Observation
- GRB 250213A: Swift-XRT observations
- GRANDMA/OPD observations of GRB250215A
- GRB 250215A: Swift/UVOT Upper Limits
- GRB 250215A: Fermi GBM Observation
- GRB 250215A/EP250215a: 1.6m Mephisto optical observation report