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"
24595 results found.
- EP250302a: Swift/UVOT detection
- EP250302a: optical observation from the INAF Asiago Observatory
- EP250302a: REM NIR upper limits
- IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
- EP250302a: Mondy Observations and Optical Light Curve
- EP250302a: VLT/MUSE optical redshift z = 1.131
- EP250302A: VLT near-infrared observations
- EP250302A: VLT/X-shooter tentative redshift
- EP250302a: OHP/T193 optical and spectroscopic observations
- EP250302a: Swift-XRT observations of a fading X-ray source
- EP250302a: Einstein Probe detection of an X-ray transient
- EP250302a: SVOM/C-GFT optical observations
- GRB 250226A: GRANDMA Optical Observations
- EP250302a: Montarrenti Observatory optical detection
- EP250302a: Nanshan/HMT optical counterpart detection
- LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
- GRB 250225B: VLT near-infrared afterglow confirmation
- EP250228a: Optical observations with Kinder and Swift/UVOT
- Konus-Wind detection of GRB 250226A
- GRB 250225B: EIRSAT-1 GMOD Detection
- GRB 250226A: KAO Optical Upper Limit
- GRB 250226A: AbAO AS-32 Optical Upper Limit
- EP250227a: Global MASTER-Net observations report
- EP250223A: Upper limits from Fermi-GBM Observations
- EP250227a: TRT optical upper limit
- GRB 250225B: VLT/HAWKI near-infrared observations
- EP250227a: Optical upper limits with Kinder observations
- EP250227a: NOT optical observations
- EP250227a: Einstein Probe detected of a fast X-ray transient
- EP250228a: updates on the EP observations
- GRB 250226A: Fermi GBM Observation
- EP250223a: J band upper limit by SYSU 80cm telescope
- EP250228a: Swift/XRT localisation
- EP250228a: Einstein Probe detection of an X-ray transient
- GRB 250226A / EP250226a: LCO detection of the afterglow
- LIGO/Virgo/KAGRA S250227e: Updated Sky localization
- LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
- GRB 250225B: VLT/Xshooter imaging
- GRB 250205A / EP250205A: further radio observations with the VLA
- EP250225a: NOT optical candidate counterpart
- EP250226a/GRB 250226A:Xinglong optical follow-up observations
- EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
- EP250225a: TRT optical upper limits
- EP250226a/GRB 250226A: 1.6m Mephisto observations
- LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
- EP250226a/GRB 250226A: Kinder optical follow-up observations
- LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
- LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
- GRB 250225B: Fermi GBM Observation
- GRB 250225B: REM NIR upper limits
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
- LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
- EP250223a: CrAO ZTSH optical observation
- GRB 250225B: VLT optical and near-infrared candidate counterpart
- GRB 250225B: SVOM/GRM observation of a long burst
- EP250226a/GRB 250226A: GSP detects optical counterpart
- EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
- EP250226a / GRB 250226A: TRT optical counterpart observation
- LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
- EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
- EP250225a: GSP optical upper limit
- EP250223a: GMG Optical Observation
- EP250225a: Einstein Probe detected of a fast X-ray transient
- GRB 250225B: Swift detection of a burst
- EP250223a: GROWTH-India Telescope optical observations
- GRB 250221A: Swift-BAT refined analysis
- EP250215A: J band upper limit by SYSU 80cm telescope
- 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
- EP250223a: Kinder optical follow-up observations
- 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 250202B: VZLUSAT-2 detection
- GRB 250222A: SVOM/GRM observation of a burst
- EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
- GRB 250206A: VZLUSAT-2 detection
- EP250223a: REM NIR upper limit
- EP250223a: TRT optical afterglow observation
- EP250223a: refined analysis of the EP-WXT and FXT observations
- EP250223a: 1.6m Mephisto and 50cm array observations
- 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: Swift/XRT localization
- EP250223a: NOT optical afterglow candidate
- EP250223a: Einstein Probe detection of an X-ray transient
- LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
- GRB 250221A: Optical counterpart detection by LCO.
- GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
- 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
- EP250220a: Liverpool Telescope upper limits