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').
18174 results found.
- GRB 250314A: NOT near-infrared candidate counterpart
- GRB 250312B: Fermi GBM Observation
- GRB 250313A: Swift-XRT observations
- Konus-Wind detection of GRB 250308A
- GRB 250313A: Fermi-LAT detection
- GRB 250313A: Swift ToO observations
- GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
- EP250304a: SVOM/VT optical observation
- EP250302a: Chandra X-ray Detection
- GRB 250312A: Swift-XRT refined Analysis
- GRB 250312A: Enhanced Swift-XRT position
- LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
- GRB 250226B: Fermi GBM Observation
- Swift GRB 250312A: Global MASTER-Net observations report
- GRB 250302A: Fermi GBM Observation
- GRB 250312A: Swift detection of a burst
- GRB 250223B: Fermi GBM Observation
- GRB 250311A: Swift-XRT observations
- GRB 250228A: Fermi GBM Observation
- GRB 230509B: 1.3m DFOT Optical observations
- 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
- EP250304a: Chandra detection
- GRB 250225B: Swift-BAT refined analysis
- GRB 250311A: Tiled Swift observations
- IPN triangulation of GRB 250308A (short)
- GRB 250309B: Swift-XRT refined Analysis
- GRB 250309B / AT2025dws: Swift-UVOT detection
- 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