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 250305A: AstroSat CZTI detection
- GRB 250306A: AstroSat CZTI detection
- Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB
- Swift GRB 250306A: Global MASTER-Net observations report
- GRB 250306A: Swift detection of a burst
- GRB 250305A: SVOM/GRM observation of a burst
- EP250304A: Upper limits from Fermi-GBM Observations
- Fermi GRB 250305A: Global MASTER-Net observations report
- GRB 250305A: Fermi GBM Final Real-time Localization
- EP250302a: Optical Observations at CrAO and SAO RAS
- GRB 250219A: SVOM/C-GFT optical upper limit at early phase
- EP 250304A: Optical counterpart detection by LCO
- Konus-Wind detection of GRB 250222A
- IPN triangulation of GRB 250222A
- EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
- EP250302a: Mondy Continued Optical Observations
- EP250304a: VLT/X-shooter redshift z = 0.200
- EP250302a: VLT/X-shooter redshift confirmation
- 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
- GRB 250226A: GRANDMA Optical Observations
- EP250302a: Montarrenti Observatory optical detection
- Fermi GRB 250302A: Global MASTER-Net observations report
- GRB 250302A: Fermi GBM Final Real-time Localization
- GRB 250228A: Fermi GBM Final Localization
- GRB 250225B: VLT near-infrared afterglow confirmation
- 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
- EP250223A: Upper limits from Fermi-GBM Observations
- GRB 250225B: VLT/HAWKI near-infrared observations
- GRB 250226A: Fermi GBM Observation
- GRB 250226A / EP250226a: LCO detection of the afterglow
- GRB 250225B: VLT/Xshooter imaging
- GRB 250205A / EP250205A: further radio observations with the VLA
- GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
- EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
- GRB 250225B: INTEGRAL SPI-ACS detection
- EP250226a/GRB 250226A:Xinglong optical follow-up observations
- EP250226a / GRB 250226A: SVOM/VT optical observations
- EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
- 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)
- Fermi GRB 250226B: Global MASTER-Net observations report
- GRB 250226B: Fermi GBM Final Real-time Localization
- GRB 250225B: Fermi GBM Observation
- GRB 250221A: ATCA Detections and Upper Limits
- GRB 250225B: REM NIR upper limits
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
- Konus-Wind detection of GRB 250225B
- EP250223a: CrAO ZTSH optical observation
- GRB 250225B: VLT optical and near-infrared candidate counterpart
- GRB 250225B: VLT/FORS2 candidate optical afterglow
- GRB 250225B: SVOM/GRM observation of a long burst
- GRB 250226A: GECAM-B detection
- GRB 250221A: EP-FXT detection of the X-ray afterglow
- GRB 250214A: SVOM/GRM observation
- EP250226a/GRB 250226A: GSP detects optical counterpart
- EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
- EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
- EP250226a / GRB 250226A: TRT optical counterpart observation
- Swift GRB 250225B: Global MASTER-Net observations report
- EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
- Fermi GRB 250226A: Global MASTER-Net observations report
- GRB 250226A: Fermi GBM Final Real-time Localization
- Fermi GRB 250225A: Global MASTER-Net observations report
- GRB 250225B: Swift detection of a burst
- GRB 250221A: Swift-BAT refined analysis
- GRB 250223C: SVOM/GRM observation of a long burst
- GRB 250225A: Fermi GBM Final Real-time Localization
- GRB 250207a: ATCA Radio Upper Limits
- 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
- GRB 250202B: VZLUSAT-2 detection
- GRB 250219A: EP-FXT afterglow detection
- GRB 250222A: SVOM/GRM observation of a burst
- GRB 250210A: VZLUSAT-2 detection
- GRB 250206A: VZLUSAT-2 detection
- GRB 250221A: TNOT detection of 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
- GRB 250223B: Fermi GBM Final Localization
- GRB 250221A: VLA radio detection
- Fermi GRB 250223A: Global MASTER-Net observations report
- GRB 250223A: Fermi GBM Final Real-time Localization
- GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
- GRB 250221A: continued Mondy optical observations, brightening afterglow
- GRB 250221A: Optical counterpart detection by LCO.
- GRB 250221A: Mondy optical observations
- Konus-Wind detection of GRB 250221A
- GRB 250221A: Assy optical observations
- GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
- GRB 250221A: VLT/X-shooter redshift z = 0.768