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').
32051 results found.
- GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
- GRB 250316A: Fermi GBM Final Real-time Localization
- GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
- GRB 250314A: EP-FXT afterglow detection
- GRB 250314A: Swift/UVOT Upper Limits
- GRB 250312B: GRBAlpha detection
- GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
- GRB 250314A: Swift XRT Detection
- GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
- GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
- SVOM/MXT upper limit on GRB 250314A
- GRB 250314A: SVOM/VT upper limit
- GRB 250314A: NOT near-infrared candidate counterpart
- GRB 250313A: Fermi GBM Detection
- GRB 250313A: CALET Gamma-Ray Burst Monitor detection
- GRB 250312B: Fermi GBM Observation
- GRB 250313A: Swift-XRT observations
- Konus-Wind detection of GRB 250313A
- Konus-Wind detection of GRB 250308A
- GRB 250314A: SVOM detection of a burst
- EP250311a/GRB 250311A: Correction to EP-WXT detection time
- GRB 250313B: SVOM/GRM observation of a soft bright short burst
- GRB 250313A: SVOM/GRM observation of a bright long burst
- GRB 250313A: AstroSat CZTI detection of a bright long burst
- GRB 250313A: Fermi-LAT detection
- GRB 250313A: Swift ToO observations
- GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
- EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
- Fermi GRB 250313A: Global MASTER-Net observations report
- GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
- GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
- GRB 250313A: Fermi GBM Final Real-time Localization
- EP250311a/GRB 250311A: EP-FXT follow-up observation
- ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
- GRB 250312A: Swift-XRT refined Analysis
- Fermi Gamma-ray Burst Monitor trigger 763509110/250312911 is not a GRB
- Fermi GRB 250312B: Global MASTER-Net observations report
- GRB 250312A: Enhanced Swift-XRT position
- GRB 250312B: Fermi GBM Final Localization
- 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 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
- GRB 250312A: Swift detection of a burst
- GRB 241213A: VIRT Optical Upper Limit
- GRB 241228A: VIRT Optical Upper Limit
- GRB 250311A/EP250311a: Optical upper limits with Kinder observations
- 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
- GRB 250309B: PRIME near-infrared detection
- GRB 250225B: Swift-BAT refined analysis
- GRB 250311A/EP250311a: TRT optical upper limit
- GRB 250311A: Tiled Swift observations
- EP250311a/GRB 250311A: EP-WXT detection
- GRB 250308A: CALET Gamma-Ray Burst Monitor detection
- GRB 250311B: SVOM detection of a burst
- GRB 250309B: SVOM/VT optical observation
- GRB 250311A/MAXI J1457-026: MAXI/GSC detection
- GRB 250309B / AT2025dws: further SAO RAS optical observations
- IceCube-250309A: Upper limits from Fermi-GBM Observations
- Konus-Wind detection of GRB 250309B
- GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
- IPN triangulation of GRB 250308A (short)
- IPN triangulation of GRB 250309B
- GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
- GRB 250309B: Swift-XRT refined Analysis
- GRB 250309B / IceCube-250309A: GECAM-B observations
- GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
- Liverpool Telecope observations of AT 2025dws / GRB 250309B
- GRB 250309B / AT2025dws: SAO RAS optical observations
- GRB 250309B / AT2025dws: Swift-UVOT detection
- AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
- GRB 250309B: Fermi GBM Observation
- Fermi GRB 250309B: Global MASTER-Net observations report
- Fermi GRB 250309A: Global MASTER-Net observations report
- GRB250309B: One candidate counterpart from the Zwicky Transient Facility
- Fermi-LAT gamma-ray observations of IceCube-250309A
- GRB 250308A: SVOM/GRM detection of QPO in the tail emission
- GRB 250309B: Fermi GBM Final Localization
- Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
- GRB 230509B: Tiled Swift observations
- GRB 250308A: SVOM/GRM observation of a bright short burst
- IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
- GRB 250309A: Fermi GBM Final Real-time Localization
- GRB 250306A: EIRSAT-1 GMOD detection
- Fermi GRB 250307A: Global MASTER-Net observations report
- Konus-Wind detection of GRB 250306A
- GRB 250307A: Fermi GBM Final Real-time Localization
- GRB 250306A: Swift-BAT refined analysis
- GRB 250306A: NuSTAR detection of the prompt emission