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"24390 results found.
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan 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
- GRB 250223C: Fermi GBM Final Real-time Localization
- GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
- GRB 250202B: VZLUSAT-2 detection
- GRB 250222A: SVOM/GRM observation of a burst
- GRB 250210A: VZLUSAT-2 detection
- GRB 250206A: VZLUSAT-2 detection
- EP250223a: REM NIR upper limit
- EP250223a: 1.6m Mephisto and 50cm array observations
- EP250223a: SVOM/VT optical observation
- 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: Swift/XRT localization
- EP250223a: NOT optical afterglow candidate
- GRB 250223B: Fermi GBM Final Localization
- EP250223a: Global MASTER-Net observations report
- GRB 250221A: VLA radio detection
- Fermi GRB 250223A: Global MASTER-Net observations report
- Fermi trigger No 762020305: Global MASTER-Net observations report
- GRB 250223A: Fermi GBM Final Real-time Localization
- LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
- GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
- Konus-Wind detection of GRB 250221A
- EP250220a: FTW optical and NIR observations and upper limits
- GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
- GRB 250221A: VLT/X-shooter redshift z = 0.768
- Fermi trigger No 761805304: Global MASTER-Net observations report
- GRB 250221A: NOT optical observations
- GRB 250221A: 1.6m Mephisto optical detection
- GRB 250221A: AKO Optical Upper Limit
- GRB 250221A: REM optical/NIR afterglow detection
- IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
- EP250220a: 1.6m Mephisto observations
- EP250220a: Optical upper limit with Kinder observations
- SVOM/sb25022102: SVOM detection of an X-ray transient
- Swift GRB250221.15: Global MASTER-Net OT detection
- Swift GRB250221.15: Global MASTER-Net observations report
- EP250220a: Xinglong optical upper limit
- GRB 250220B: Fermi GBM Final Real-time Localization
- GRB 250220A: Fermi GBM Final Real-time Localization
- EP250220a: Global MASTER-Net observations report
- Konus-Wind detection of GRB 250217C (short)
- GRB 250219A: NOT optical observations
- GRB 250219A: 1.6m Mephisto optical upper limits
- GRB 250219A: SVOM/VT optical counterpart
- GRB 250219A: Swift-XRT observations
- LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
- GRB 250219A: SVOM detection of a burst
- Konus-Wind detection of GRB 250215A / EP250215a
- GRB 250217C: Swift-XRT observations
- GRB 250217C: SVOM/GRM observation
- GRB 250217C: Fermi GBM Observation
- IPN triangulation of GRB 250217C (short)
- SVOM/sb25021804: SVOM detection of a long X-ray transient
- GRB 250213A: Swift-XRT observations
- LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
- Fermi GRB 250217C: Global MASTER-Net observations report
- GRB 250217C: Fermi GBM Final Real-time Localization
- IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
- LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
- Fermi GRB 250217A: Global MASTER-Net observations report
- GRB 250217B: Fermi GBM Final Real-time Localization
- GRB 250217A: Fermi GBM Final Real-time Localization
- Fermi GRB 250216A: Global MASTER-Net observations report
- GRB 250216A: Fermi GBM Final Real-time Localization
- EP250212a: FTW optical and NIR upper limits
- GRB 250215A: Fermi GBM Observation
- GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
- GRB 250215A: SVOM/GRM observation
- GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
- EP250215a: Global MASTER-Net observations report
- EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
- EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
- Fermi GRB 250215A: Global MASTER-Net observations report
- GRB 250215A: Fermi GBM Final Real-time Localization
- Fermi trigger No 761206993: Global MASTER-Net observations report
- GRB 250213A:SVOM/VT optical candidate
- EP250207b: Xinglong optical upper limit
- Fermi GRB 250214A: Global MASTER-Net observations report
- GRB 250214A: Fermi GBM Final Real-time Localization
- EP250212a: Xinglong optical upper limit
- LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
- GRB 250213A: SVOM detection of a burst
- EP250212a: Global MASTER-Net observations report
- GRB 250205A: Leavitt Observatory optical upper limit
- GRB 250210A: GRBAlpha detection
- EP250207B: Chandra localization of the X-ray counterpart
- LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
- EP250207b: VLA radio upper limits
- EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
- GRB250101A: Radio upper limits from GMRT observations
- EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
- Fermi GRB 250212A: Global MASTER-Net observations report
- Fermi trigger No 760945500: Global MASTER-Net observations report
- EP250207b: NOT optical counterpart candidate
- GRB 250211B: A long GRB detected by INTEGRAL
- Integral GRB250211.89: Global MASTER-Net observations report
- GRB 250212A: Fermi GBM Final Real-time Localization