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"12319 results found.
- 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 250313A: Swift-XRT observations
- Konus-Wind detection of GRB 250308A
- FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
- IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
- Fermi trigger No 763581136: Global MASTER-Net observations report
- Fermi GRB 250313A: Global MASTER-Net observations report
- GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
- Fermi trigger No 763509110: Global MASTER-Net observations report
- Fermi GRB 250312B: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
- Swift GRB 250312A: Global MASTER-Net observations report
- 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 250311A: Swift-XRT observations
- IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
- EP250311a: Global MASTER-Net observations report
- GRB 250311A/EP250311a: TRT optical upper limit
- GRB 250311A/MAXI J1457-026: MAXI/GSC detection
- IceCube-250309A: Upper limits from Fermi-GBM Observations
- EP250308a: 1.6m Mephisto optical upper limits
- Konus-Wind detection of GRB 250309B
- IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
- GRB 250309B / IceCube-250309A: GECAM-B observations
- 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
- IceCube Alert 250309.32: Global MASTER-Net observations report
- EP250308a: Global MASTER-Net observations report
- EP250308a: GSP optical upper limit
- EP250308a: FTW optical and NIR upper limits
- EP250308a: NOT optical upper limit
- Fermi GRB 250307A: Global MASTER-Net observations report
- IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
- Fermi trigger No 762963055: Global MASTER-Net observations report
- Swift GRB 250306A: Global MASTER-Net observations report
- GRB250101A: Radio upper limits from VLA observations
- EP250304A: Upper limits from Fermi-GBM Observations
- Fermi GRB 250305A: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-250302A
- EP250302a: Optical Observations at CrAO and SAO RAS
- GRB 250219A: SVOM/C-GFT optical upper limit at early phase
- IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
- EP250304a: REM NIR upper limits
- EP250304a: Swift-XRT detection of a fading X-ray source
- EP250304a: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
- EP250302a: REM NIR upper limits
- IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
- EP250302a: Global MASTER-Net observations report
- Fermi GRB 250302A: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
- EP250228a: Optical observations with Kinder and Swift/UVOT
- 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
- EP250225a: EP-FXT follow-up observation
- EP250223a: J band upper limit by SYSU 80cm telescope
- EP250228a: Global MASTER-Net observations report
- GRB 250205A / EP250205A: further radio observations with the VLA
- EP250225a: TRT optical upper limits
- EP250226a/GRB 250226A: 1.6m Mephisto observations
- LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
- Fermi GRB 250226B: Global MASTER-Net observations report
- GRB 250221A: ATCA Detections and Upper Limits
- GRB 250225B: REM NIR upper limits
- Konus-Wind detection of GRB 250225B
- LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
- EP250226a: Global MASTER-Net observations report
- Swift GRB 250225B: Global MASTER-Net observations report
- Fermi GRB 250226A: Global MASTER-Net observations report
- Fermi trigger No 762205158: Global MASTER-Net observations report
- EP250225a: Global MASTER-Net observations report
- EP250225a: GSP optical upper limit
- Fermi GRB 250225A: Global MASTER-Net observations report
- EP250215A: J band upper limit by SYSU 80cm telescope
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
- GRB 250207a: ATCA Radio Upper Limits
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
- EP250223a: REM NIR upper limit
- EP250223a: 1.6m Mephisto and 50cm array observations
- LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
- EP250223a: Global MASTER-Net observations report
- Fermi GRB 250223A: Global MASTER-Net observations report
- Fermi trigger No 762020305: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
- EP250220a: FTW optical and NIR observations and upper limits
- EP250220a: EP-FXT follow-up observations
- GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
- Fermi trigger No 761805304: Global MASTER-Net observations report