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"4055 results found.
- IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
- IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
- LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
- GRB 250101A NUTTelA-TAO / BSTI Early Measurements
- GRB 250101A: 1.6m Mephisto multi-band optical followup
- LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
- LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
- LIGO/Virgo/KAGRA S241231du: Coverage and upper limit from MAXI/GSC observations
- LIGO/Virgo/KAGRA S250101k: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241231bg: Updated NED Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S241231bg: Updated Sky localization and EM Bright Classification
- LIGO/Virgo/KAGRA S241230ev: Updated Sky localization
- LIGO/Virgo/KAGRA S241231bg: NED Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S241230bd: Updated Sky localization
- LIGO/Virgo/KAGRA S241231bg: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241230ev: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241230bd: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241225v: Updated Sky localization
- LIGO/Virgo/KAGRA S241225c: Updated Sky localization and EM Bright Classification
- IceCube-241224A: Upper limits from a search for additional neutrino events in IceCube
- LIGO/Virgo/KAGRA S241225c: Two counterpart neutrino candidates from IceCube neutrino searches
- LIGO/Virgo/KAGRA S241225v: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241225c: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241210fu: Updated Sky localization
- LIGO/Virgo/KAGRA S241210cw: Updated Sky localization
- LIGO/Virgo/KAGRA S241210d: Updated Sky localization and EM Bright Classification
- LIGO/Virgo/KAGRA S241210fu: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241210cw: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241210d: Identification of a GW compact binary merger candidate
- GRB 241209B: BOOTES-5 optical upper limit
- LIGO/Virgo/KAGRA S241102br: continued GRAWITA observations and detection of an optical transient (AT2024adip)
- LIGO/Virgo/KAGRA S241125n: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
- GRB 241204A: DDOTI Upper Limits on the Afterglow
- EP241201a: BOOTES-5 optical upper limit
- IceCube-241127A: Upper limits from a search for additional neutrino events in IceCube
- LIGO/Virgo/KAGRA S241102br: GRAWITA wide-field optical observations
- LIGO/Virgo/KAGRA S241201ac: Updated Sky localization
- LIGO/Virgo/KAGRA S241201ac: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241130be: Updated Sky localization
- LIGO/Virgo/KAGRA S241130n: Updated Sky localization
- LIGO/Virgo/KAGRA S241125n: GRANDMA Optical Upper Limits
- LIGO/Virgo/KAGRA S241127aj: Updated Sky localization
- LIGO/Virgo/KAGRA S241130be: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241129aa: Updated Sky localization
- LIGO/Virgo/KAGRA S241130n: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241129aa: Identification of a GW compact binary merger candidate
- LIGO/Virgo S241127aj: GRANDMA/FRAM-CTA-N Observations
- LIGO/Virgo/KAGRA S241127aj: Updated Sky localization
- LIGO/Virgo/KAGRA S241125n: Update on Coincidence False Alarm Method
- LIGO/Virgo/KAGRA S241125n: Preliminary flux estimate and spectral analysis of the Swift/BAT-GUANO candidate counterpart
- LIGO/Virgo/KAGRA S241125n: Swift-UVOT Upper Limits
- LIGO/Virgo/KAGRA S241127aj: NED Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S241125n: EP-FXT follow-up observations (duplicate submission of 38345)
- LIGO/Virgo/KAGRA S241125n: EP-FXT follow-up observations (duplicate submission of 38345).
- LIGO/Virgo/KAGRA S241125n: EP-FXT follow-up observations
- LIGO/Virgo/KAGRA S241127aj: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241125n: COLIBRÍ Upper Limits on Optical Counterparts to Two of the Swift/XRT Sources
- LIGO/Virgo/KAGRA S241125n: SAGUARO follow-up observations with the MMT
- LIGO/Virgo/KAGRA S241126dm: Retraction of GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241125n: DDOTI Optical Upper Limits
- LIGO/Virgo/KAGRA S241125n: Gaoyazi/GOT optical observations
- LIGO/VIRGO/KAGRA S241125n: GROWTH-India telescope optical observations
- LIGO/Virgo S241125n: Swift XRT observations, 5 X-ray sources
- LIGO/Virgo/KAGRA S241125n: HCT upper limit
- LIGO/Virgo/KAGRA S241125n: Upper limits from Konus-Wind observations
- LIGO/Virgo/KAGRA S241125n: COLIBRÍ Upper Limits on a Optical Counterpart at the BAT Position
- LIGO/Virgo/KAGRA S241125n: Upper limits from Fermi-GBM Observations
- LIGO/Virgo/KAGRA S241125n: Updated Coincidence with External Event
- LIGO/Virgo/KAGRA S241125n: Kinder optical upper limit in the BAT error region
- LIGO/Virgo/KAGRA S241125n: Updated Sky localization
- LIGO/Virgo/KAGRA S241125n: Updated Coincidence with External Event
- LIGO/Virgo/KAGRA S241125n: No counterpart candidates in INTEGRAL SPI-ACS prompt observation, comparisong with Swift/BAT counterpart
- LIGO/Virgo/KAGRA S241109bn: Upper limits from a two-week IceCube neutrino search
- LIGO/Virgo/KAGRA S241125n: Updated Sky localization and Coincidence with External Event
- LIGO/Virgo/KAGRA S241125n: Swift/BAT-GUANO candidate counterpart
- LIGO/Virgo/KAGRA S241125n: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241122a: Updated Sky localization and Source Classification
- LIGO/Virgo/KAGRA S241122a: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241116cq: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S241114y: Updated Sky localization
- Updates to IceCube realtime alert system for muon tracks
- LIGO/Virgo/KAGRA S241116cq: Updated Sky localization
- LIGO/Virgo/KAGRA S241116cq: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241114bi: Updated Sky localization and EM Bright Classification
- LIGO/Virgo/KAGRA S241113p: Updated Sky localization
- LIGO/Virgo/KAGRA S241114bi: Upper limits from Fermi-GBM Observations
- LIGO/Virgo/KAGRA S241114bi: Coverage and upper limits from MAXI/GSC observations
- LIGO/Virgo/KAGRA S241114bi: Identification of a GW compact binary merger candidate
- IceCube-241113A: Upper limits from a search for additional neutrino events in IceCube
- LIGO/Virgo/KAGRA S241114y: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241113p: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241111bn: Updated Sky localization
- Fermi Gamma-ray Burst Monitor trigger 752995908/241111230 (GRB 241111A) is not a GRB
- LIGO/Virgo/KAGRA S241110br: NED Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S241109bn: ATLAS observations and discovery of the potential counterpart AT2024aawt
- LIGO/Virgo/KAGRA S241111bn: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241110br: Updated Sky localization
- LIGO/Virgo/KAGRA S241110bk: 1 counterpart neutrino candidate event from an IceCube neutrino search
- LIGO/Virgo/KAGRA S241110br: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S241109bn: Upper limits from EP-WXT observations