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.
Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
- GRB 240910A: further Swift observations and confirmation of afterglow
- LIGO/Virgo/KAGRA S240919bn: Identification of a GW compact binary merger candidate
- EP240918a: Swift-XRT observation
- Fermi GRB 240918A: Global MASTER-Net observations report
- GRB 240918A: Fermi GBM Final Real-time Localization
- EP EP240918a: Global MASTER-Net observations report
- EP240918a: JinShan optical upper limits
- EP240918a: YAHPT Optical Upper Limit
- EP240918a: Optical upper limits with Kinder observations
- EP240918a: GMG Optical Upper Limit
- GRB 240916A: GRBAlpha detection
- GRB 240914B: GRBAlpha detection
- EP240918a: an X-ray transient detected by Einstein Probe
- GRB 240916A: NOT optical observation
- GRB 240912A: Swift-BAT refined analysis
- IPN triangulation of GRB 240913C / EP 240913a
- GRB 240825A: INTEGRAL SPI ACS LIGHT CURVE
- GRB 240825A: The nature of the afterglow motivates the search of the associated supernova
- GRB 240916A: Fermi GBM Observation
- LIGO/Virgo/KAGRA S240917cb: Identification of a GW compact binary merger candidate
- GRB 240821A: radio observation with the VLA
- GRB 240916A (AT 2024vlp / GOTO24fzn): VLT/X-shooter redshift
- GRB 240916A: Swift-XRT afterglow detection
- LIGO/Virgo/KAGRA S240916ar: Identification of a GW compact binary merger candidate
- GRB 240916A: Swift ToO observations
- LIGO/Virgo/KAGRA S240915b: NED Galaxies in the Localization Volume
- LIGO/Virgo S240915b: Swift XRT observations, 8 X-ray sources
- GRB 240916A: JinShan optical decay in one of the two GOTO candidates
- GRB 240916B: Fermi GBM Final Real-time Localization
- GRB 240914B: Fermi GBM Final Localization
- The EP-WXT triggers 01709047257 and 01709047278 are not real sources
- GRB 240916A: GOTO identification of two new optical sources within the GBM localisation region
- EP EP240913a: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S240915b: Coverage and upper limits from MAXI/GSC observations
- GRB 240916A INTEGRAL SPI ACS LIGHT CURVE
- GRB 240916A: Fermi GBM Final Real-time Localization
- Fermi Gamma-ray Burst Monitor trigger 748124309/240915846 is not a GRB
- LIGO/Virgo/KAGRA S240915bd: Updated Sky localization
- EP240913a: VLT/HAWK-I near-infrared upper limits
- LIGO/Virgo/KAGRA S240915bd: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S240915b: Updated Sky localization and EM Bright Classification
- LIGO/Virgo/KAGRA S240915b: Identification of a GW compact binary merger candidate
- EP240913a/GRB 240913C: KAIT optical upper limit
- EP240913a / GRB 240913C INTEGRAL SPI ACS LIGHT CURVE
- GRB 240913C: Fermi GBM detection
- GRB 240914A: Swift-XRT observations
- GRB 240913C: Joint location by ETJASMIN
- GRB 240914B: AstroSat CZTI detection
- EP240913A / GRB 240913C: AstroSat CZTI detection
- GRB 240914A: SVOM/GRM observation
- GRB 240910A: SVOM/VT optical observations
- GRB 240914A: Swift ToO observations
- EP240913a: NOT optical upper limits
- EP240913a: JinShan optical upper limits
- EP240913a: ESO-NTT optical observations
- GRB 240914A: ESO-NTT optical observations
- EP240913a: Swift/XRT detection of an X-ray source within the EP/WXT error circle
- GRB 240914B: BALROG localization (Fermi Trigger 747990592 / GRB 240914298)
- GRB 240914A : An intermediate duration GRB located on-board by SVOM/ECLAIRs.
- GRB 240905E: further NOT optical observations
- EP240913a: A GRB Event
- EP240913a: EP-WXT detection of a fast X-ray transient
- GRB 240913B: Fermi GBM Final Real-time Localization
- GRB 240911A: LCO optical observations
- GRB 240911A: JinShan optical upper limits on two Swift/XRT candidates
- Fermi Gamma-ray Burst Monitor trigger 747837485/240912526 is not a GRB
- GRB 240912A: Swift/UVOT Detection
- GRB 240911A: GOTO optical limits on Swift/XRT candidates
- Fermi trigger No 747920561: Global MASTER-Net observations report
- GRB 240912A: SVOM/GRM observation
- GRB 240911A: Swift-XRT observations
- Fermi GRB 240913A: Global MASTER-Net observations report
- GRB 240913A: Fermi GBM Final Real-time Localization
- GRB 240912A: J-band observations with WINTER
- GRB 240912A: Swift-XRT refined Analysis
- GRB 240912A: Fermi GBM Observation
- Swift GRB 240912A: Global MASTER-Net observations report
- GRB 240912A: LCOGT detection and Legacy Surveys likely host galaxy
- GRB 240911A: Tiled Swift observations
- Fermi Gamma-ray Burst Monitor trigger 747839931/240912555 is not a GRB
- GRB 240912A : INTEGRAL SPI ACS LIGHT CURVE
- GRB 240912B: Fermi GBM Final Real-time Localization
- GRB 240912A: NOT optical spectroscopy
- GRB 240912A: Enhanced Swift-XRT position
- GRB 240912A: Redshift from OSIRIS+/GTC
- Fast X-ray Transient EP240801a: GMRT radio observations
- GRB 240910A: Redshift from OSIRIS+/GTC
- GRB 240912A: Swift detection of a burst with an optical counterpart
- GRB 240912A: Fermi GBM Final Real-time Localization
- GRB 240910A: Fermi GBM Observation
- GRB 240910A: NOT optical observations
- GRB 240911A : a likely weak GRB detected by SVOM/ECLAIRs
- GRB 240910A: Swift-XRT detection of GOTO24fvl/AT2024vfp
- GRB 240910A: JinShan optical observations
- GRB 240910A: GOTO candidate optical counterpart
- EP240908a: Optical afterglow confirmation
- GRB 240710A: SVOM/GRM observation
- GRB 240910A: Swift ToO observations
- IPN triangulation of GRB 240905B (short)
- GRB 240825A: 7DT Optical Upper Limit