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.
Lucene Examples (click to copy):
subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
18342 results found.
- GRB250309B: One candidate counterpart from the Zwicky Transient Facility
- Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
- GRB 230509B: Tiled Swift observations
- GRB 250306A: EIRSAT-1 GMOD detection
- Konus-Wind detection of GRB 250306A
- GRB 250306A: Swift-BAT refined analysis
- GRB 250306A: NuSTAR detection of the prompt emission
- GRB 250306A: AstroSat CZTI detection
- Swift GRB 250306A: Global MASTER-Net observations report
- GRB 250306A: Swift detection of a burst
- 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
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
- EP250302a: Swift/UVOT detection
- EP250302a: Swift-XRT observations of a fading X-ray source
- EP250228a: Optical observations with Kinder and Swift/UVOT
- GRB 250225B: EIRSAT-1 GMOD Detection
- GRB 250225B: VLT/HAWKI near-infrared observations
- EP250228a: updates on the EP observations
- EP250228a: Swift/XRT localisation
- GRB 250225B: INTEGRAL SPI-ACS detection
- LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
- GRB 250225B: Fermi GBM Observation
- GRB 250221A: ATCA Detections and Upper Limits
- GRB 250225B: REM NIR 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/FORS2 candidate optical afterglow
- GRB 250225B: SVOM/GRM observation of a long burst
- GRB 250221A: EP-FXT detection of the X-ray afterglow
- LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
- Swift GRB 250225B: Global MASTER-Net observations report
- GRB 250225B: Swift detection of a burst
- GRB 250221A: Swift-BAT refined analysis
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
- GRB 250207a: ATCA Radio Upper Limits
- LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
- GRB 250119B: VZLUSAT-2 detection
- GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
- GRB 250219A: EP-FXT afterglow detection
- 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: SVOM/VT optical observation
- 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: LCO detection of the afterglow
- EP250223a: early optical detection by BOOTES-4
- EP250223a: NOT redshift z = 2.756
- EP250223a: Swift/XRT localization
- GRB 250221A: VLA radio detection
- GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
- GRB 250221A: continued Mondy optical observations, brightening afterglow
- GRB 250221A: Optical counterpart detection by LCO.
- GRB 250221A: Mondy optical observations
- Konus-Wind detection of GRB 250221A
- GRB 250221A: Assy optical observations
- GRB 250221A: GRANDMA/TAROT Detection
- GRB 250221A: Swift-XRT refined Analysis
- GRB 250221A: NOT optical observations
- GRB 250221A: 1.6m Mephisto optical detection
- GRB 250221A: AKO Optical Upper Limit
- GRB 250221A: Swift/UVOT Detection
- GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
- GRB 250221A: REM optical/NIR afterglow detection
- GRB 250221A: Enhanced Swift-XRT position
- GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
- GRB 250221A: Swift detection of a burst with an optical counterpart
- Swift GRB250221.15: Global MASTER-Net OT detection
- Swift GRB250221.15: Global MASTER-Net observations report
- GRB 250219A: Swift/UVOT Upper Limits
- GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
- GRB 250219A: 1.6m Mephisto optical upper limits
- GRB 250219A: SVOM/VT optical counterpart
- GRB 250219A: Swift-XRT observations
- GRB 250219A: Swift ToO observations
- GRB 250217C: Swift-XRT observations
- GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
- GRB 250217C: Tiled Swift observations
- IPN triangulation of GRB 250217C (short)
- Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
- SVOM/sb25021804: SVOM detection of a long X-ray transient
- GRB 250213A: Swift-XRT observations
- GRB 250215A / EP250215a: LCO detection of the afterglow
- GRB 250215A: Swift/UVOT Upper Limits
- GRB 250215A: Fermi GBM Observation
- GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
- GRB 250215A: Swift-XRT refined Analysis
- GRB 250213A: Swift ToO observations
- GRB 250211A: SVOM trigger sb25021103 is not a GRB
- GRB 250211A: Swift ToO observations
- GRB 250207A: Fermi GBM Observation
- Konus-Wind detection of GRB 250207A