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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').
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"
  1. Correction to GCN 32852 (GRB 221009A: SARA-RM 1m Optical Afterglow Detection)
  2. IceCube Alert 221104.26: Global MASTER-Net observations report
  3. Fermi-LAT gamma-ray observations of IceCube-221104A
  4. IceCube-221104A - IceCube observation of a high-energy neutrino candidate track-like event
  5. GRB 221029A: CALET Gamma-Ray Burst Monitor detection
  6. High-precision position of the compact radio counterpart to GRB221009A
  7. GRB 221028A: GRANDMA observations
  8. GRB 221027B: GRANDMA observations
  9. GRB 221028A: Detection by VZLUSAT-2
  10. GRB 221029A: Fermi GBM observation
  11. GRB 221027C: AstroSat CZTI detection
  12. Konus-Wind detection of GRB 221022C
  13. GRB 221029A: Fermi GBM Final Localization
  14. GRB 221028A: Swift-XRT refined Analysis
  15. GRB 221028A: 1.3m DFOT Optical upper limit
  16. GRB 221028A: NUTTelA-TAO / BSTI Early Optical Limits
  17. GRB 221028A: NUTTelA-TAO / BSTI Early Optical Limits
  18. GRB 221028A: Correction to GCN 32893 - Fluence and flux are for 50-150 keV
  19. GRB 221028A: AKO Optical Upper Limit
  20. GRB 221028A, Swift-BAT refined analysis
  21. GRB 221027B: Swift-BAT refined analysis
  22. GRB 221029A: Swift/BAT-GUANO detection outside the coded FOV
  23. GRB 221029A: Detection by GRBAlpha
  24. GRB 221028A: CrAO/ZTSh optical upper limit
  25. GRB 221028A: COATLI Upper Limits
  26. Trigger 1132968: Swift trigger is the Crab
  27. GRB 221028A: HCT optical upper limit
  28. GRB 221028A: AGILE detection
  29. GRB 221027A: AGILE detection
  30. GRB 221028A: MITSuME Okayama optical upper limits
  31. GRB 221028B: MAXI/GSC detection
  32. GRB 221028A: LCOGT Optical Upper Limits
  33. GRB 221027B: COATLI Upper Limits
  34. Swift GRB 221028A: Global MASTER-Net observations report
  35. GRB 221028A: BOOTES-4/MET optical upper limit
  36. LIGO-Virgo-KAGRA and GEO600 statement on GRB 221009A
  37. GRB 221028A: GIT optical upper limit
  38. GRB 221027B: Swift/UVOT Upper Limits
  39. GRB 221028A: Swift detection of a burst
  40. GRB 221027B: FRAM-ORM and Ondrejov SBT optical limits
  41. Konus-Wind detection of GRB 221017A
  42. Swift GRB 221027B: Global MASTER-Net observations report
  43. GRB 221027B: Swift-XRT refined Analysis
  44. GRB 221027B: BOOTES-1 optical upper limit
  45. GRB 221027B: Enhanced Swift-XRT position
  46. GRB 221027B: Swift detection of a burst
  47. GRB 221027A: Fermi GBM detection
  48. IPN triangulation of GRB 221025A (short)
  49. Konus-Wind detection of GRB 221022B
  50. GRB 221024A: Mondy optical observations
  51. GRB 221027A: Fermi-LAT detection
  52. GRB 221027A: Fermi GBM Final Real-time Localization
  53. GRB 221009A: Further Gemini-South Infrared Observations
  54. GRB 221024A: GRANDMA observations
  55. Fermi Gamma-ray Burst Monitor trigger 688431261/221025954 is not a GRB
  56. IPN triangulation of GRB 221022C (short)
  57. GRB 221023A: AGILE/GRID analysis
  58. SGR 1935+2154: AstroSat CZTI Detections
  59. GRB 221024A: Swift-BAT refined analysis
  60. GRB 221025A: AstroSat CZTI detection
  61. GRB 221009A: SARA-RM 1m Optical Afterglow Detection
  62. GRB 221025A: Fermi GBM Observation
  63. GRB 221009A: spectroscopic confirmation of SN in LBT spectra
  64. Konus-Wind detection of GRB 221023A
  65. GRB 221024A: Swift/UVOT UV upper limits
  66. GRB 221022A: Swift-XRT observations
  67. GRB 221024A: Swift-XRT refined Analysis
  68. GRB 221023A: Fermi GBM Observation
  69. GRB 221022B: Detection by GRBAlpha
  70. GRB 221025A: Fermi-LAT detection
  71. IPN triangulation of GRB 221022B (long)
  72. GRB 221024A: GIT confirmation of the optical afterglow
  73. LAT GRB221025.04: Global MASTER-Net observations report
  74. GRB 221024A: Enhanced Swift-XRT position
  75. GRB 221024A: D50 candidate afterglow
  76. GRB 221022B: AstroSat CZTI detection
  77. GRB 221022A: Fermi GBM detection
  78. GRB 221022A: Swift ToO observations
  79. Fermi Gamma-ray Burst Monitor detections of SGR 1935+2154
  80. GRB 221023A: Fermi-LAT detection
  81. GRB 221022B: Fermi GBM detection
  82. GRB 221021A: Fermi GBM observation
  83. GRB 221009A: Determination of the black holes mass and spin
  84. GRB 221024A: Swift detection of a burst
  85. GRB 221023A: Fermi GBM Final Localization
  86. GRB 221023A: AGILE detection of a burst
  87. GRB 221022A: Swift/BAT-GUANO detection
  88. GRB 221022B: Swift/BAT-GUANO detection outside the coded FOV
  89. GRB 221022B: AGILE detection
  90. GRB 221009A: James Webb Space Telescope Observations
  91. GRB 221022B: Fermi GBM Final Real-time Localization
  92. GRB 221009A: Analysis of the initial episode using data of GBM/Fermi and SPI-ACS/INTEGRAL
  93. GRB 221009A: optical observations, SN photometric evidence
  94. GRB 221021A: Swift/BAT-GUANO detection outside the coded FOV
  95. GRB 221022A: Fermi GBM Final Real-time Localization
  96. GRB 221020A: Detection by GRBAlpha
  97. SGR 1935+21542: VZLUSAT-2 and GRBAlpha joint detection
  98. GRB 221017A: CALET Gamma-Ray Burst Monitor detection
  99. GRB 221021A: Fermi GBM Final Real-time Localization
  100. GRB 221009A: 1.3m DFOT Optical Observations

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