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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. GRB 221009A:DAMPE observed a 34.7 GeV photon at 1.36 hour after the GBM trigger
  2. GRB 221120A: GTC Confirmation of an Underlying Galaxy
  3. IPN triangulation of GRB 221121A (long)
  4. GRB 221120A: Swift-BAT refined analysis
  5. GRB221121A: AstroSat CZTI detection
  6. GRB 221120A: AKO Telescope Upper Limits
  7. GRB221120A: WIRC near-IR imaging of the afterglow candidate
  8. GRB 221120A: Liverpool Telescope Upper Limits
  9. GRB 221120A: Archival PS1 Imaging of Faint Source near XRT position
  10. GRB 221120A: Fermi GBM observation
  11. GRB 221120A: Swift-XRT refined Analysis
  12. GRB 221120A: Enhanced Swift-XRT position
  13. GRB221120A: Montarrenti Observatory Upper Limit
  14. GRB 221121A: Fermi GBM Final Real-time Localization
  15. GRB 221120A is a short burst
  16. GRB 221120A: Swift/UVOT Upper Limits
  17. GRB 221120A: LDT Optical Afterglow Candidate
  18. GRB 221120A: GIT upper limits on optical afterglow
  19. GRB 221120A: Swift detection of a likely short burst
  20. GRB 221119A: Fermi GBM detection
  21. GRB 221119A: Detection by GRBAlpha
  22. GRB 221119A: Fermi-LAT detection
  23. LAT GRB221119.63: Global MASTER-Net observations report
  24. GRB 221119A: Fermi GBM Final Real-time Localization
  25. GRB 221009A: Japanese VLBI Network observation
  26. GRB 221115B: CALET Gamma-Ray Burst Monitor detection
  27. GRB 221114A: CALET Gamma-Ray Burst Monitor detection
  28. GRB 221118A: Fermi GBM Final Real-time Localization
  29. GRB 221115B: LCOGT Optical Upper Limits
  30. Correction to GCN 32646 (GRB 221009A (Swift J1913.1+1946): MeerLICHT observations)
  31. GRB 221115B : MeerLICHT upper limits
  32. GRB 221115A: Fermi GBM detection
  33. GRB 221115B: Swift/BAT-GUANO arcminute localization
  34. GRB 221115A: Swift/BAT-GUANO detection
  35. GRB 221110A: GRANDMA observations
  36. Konus-Wind detection of a burst from SGR 1935+2154 on 2022 November 9
  37. GRB 221112A: Detection by GRBAlpha
  38. GRB 221112A: Fermi GBM Final Real-time Localization
  39. GRB 221110A: COATLI Second-Epoch Upper Limits
  40. GRB 221009A: GRANDMA/Kilonova-Catcher observations
  41. GRB 221110A: GMG upper limit
  42. GRB 221110A: Swift/UVOT Detection and Corrected UVOT Position
  43. GRB 221110A: Swift-BAT refined analysis
  44. GRB 221110A: Swift-XRT refined Analysis
  45. GRB 221110A: Enhanced Swift-XRT position
  46. GRB 221110A: VLT/X-shooter redshift
  47. GRB 221110A: COATLI Afterglow detection
  48. GRB 221110A: LCOGT Optical Afterglow Detection
  49. GRB 221110A: Swift detection of a burst with an optical counterpart
  50. Swift GRB221110.10: Global MASTER-Net OT detection
  51. Swift GRB221110.10: Global MASTER-Net observations report
  52. Fermi-GBM Observations of High Bursting Activity from SGR J1935+2154
  53. GRB 221009A: Hubble Space Telescope observations
  54. GRB 221104A: Fermi GBM Final Localization
  55. GRB 221108A: Fermi GBM Final Localization
  56. GRB 221107A: Fermi GBM Observation
  57. GRB 221107A: Detection by GRBAlpha
  58. GRB 221009A: Extended Bad Time Intervals for Fermi LAT data
  59. GRB 221107A: Swift/BAT-GUANO detection outside the coded FOV
  60. IceCube-221104A: Upper limits from a search for additional neutrino events in IceCube
  61. GRB 221107A: Fermi GBM Final Localization
  62. Correction to GCN 32852 (GRB 221009A: SARA-RM 1m Optical Afterglow Detection)
  63. IceCube Alert 221104.26: Global MASTER-Net observations report
  64. Fermi-LAT gamma-ray observations of IceCube-221104A
  65. IceCube-221104A - IceCube observation of a high-energy neutrino candidate track-like event
  66. GRB 221029A: CALET Gamma-Ray Burst Monitor detection
  67. High-precision position of the compact radio counterpart to GRB221009A
  68. GRB 221028A: GRANDMA observations
  69. GRB 221027B: GRANDMA observations
  70. GRB 221028A: Detection by VZLUSAT-2
  71. GRB 221029A: Fermi GBM observation
  72. GRB 221027C: AstroSat CZTI detection
  73. Konus-Wind detection of GRB 221022C
  74. GRB 221029A: Fermi GBM Final Localization
  75. GRB 221028A: Swift-XRT refined Analysis
  76. GRB 221028A: 1.3m DFOT Optical upper limit
  77. GRB 221028A: NUTTelA-TAO / BSTI Early Optical Limits
  78. GRB 221028A: NUTTelA-TAO / BSTI Early Optical Limits
  79. GRB 221028A: Correction to GCN 32893 - Fluence and flux are for 50-150 keV
  80. GRB 221028A: AKO Optical Upper Limit
  81. GRB 221028A, Swift-BAT refined analysis
  82. GRB 221027B: Swift-BAT refined analysis
  83. GRB 221029A: Swift/BAT-GUANO detection outside the coded FOV
  84. GRB 221029A: Detection by GRBAlpha
  85. GRB 221028A: CrAO/ZTSh optical upper limit
  86. GRB 221028A: COATLI Upper Limits
  87. Trigger 1132968: Swift trigger is the Crab
  88. GRB 221028A: HCT optical upper limit
  89. GRB 221028A: AGILE detection
  90. GRB 221027A: AGILE detection
  91. GRB 221028A: MITSuME Okayama optical upper limits
  92. GRB 221028B: MAXI/GSC detection
  93. GRB 221028A: LCOGT Optical Upper Limits
  94. GRB 221027B: COATLI Upper Limits
  95. Swift GRB 221028A: Global MASTER-Net observations report
  96. GRB 221028A: BOOTES-4/MET optical upper limit
  97. LIGO-Virgo-KAGRA and GEO600 statement on GRB 221009A
  98. GRB 221028A: GIT optical upper limit
  99. GRB 221027B: Swift/UVOT Upper Limits
  100. GRB 221028A: Swift detection of a burst

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