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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 251215A: Swift-XRT afterglow detection
  2. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
  3. IceCube-251218A: COLIBRÍ optical upper limits
  4. SVOM GRB251219.11: Global MASTER-Net observations report
  5. IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
  6. IceCube Alert 251218.85: Global MASTER-Net observations report
  7. GRB 251214B: VIRT Optical Upper Limit
  8. Fermi trigger No 787736968: Global MASTER-Net observations report
  9. Fermi GRB 251217A: Global MASTER-Net observations report
  10. GRB 251217A: Fermi GBM Final Real-time Localization
  11. GRB 251215A: Swift/UVOT Upper LImits
  12. GRB 251215A: Fermi GBM Observation
  13. Fermi GRB 251216A: Global MASTER-Net observations report
  14. GRB 251202A/EP251202a: Koshka optical upper limit
  15. GRB 251214B: Mondy optical upper limit
  16. GRB 251215A: COLIBRÍ optical upper limit
  17. GRB 251216A: Fermi GBM Final Real-time Localization
  18. EP251214b: KAIT optical upper limit
  19. GRB 251215A: Swift-XRT observations
  20. Fermi GRB 251215A: Global MASTER-Net observations report
  21. EP251214a: Optical upper limit with Kinder observations
  22. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  23. GRB 251215A: Glowbug gamma-ray detection
  24. GRB 251214B: UAFO optical upper limit
  25. GRB 251214B: VLT/X-shooter observations
  26. GRB 251213A: GRID-10B observation
  27. GRB 251214B: Swift-BAT refined analysis
  28. GRB 251202A: radio detection with the VLA
  29. EP251214b: Global MASTER-Net observations report
  30. EP251214b : Einstein Probe detection of a fast X-ray transient
  31. EP251214b : Einstein Probe detection of a fast X-ray transient
  32. GRB 251214B: AbAO optical observations
  33. GRB 251214B: LCO detection of the optical counterpart
  34. GRB 251209A: GECAM-B observation of a long burst
  35. GRB 251214D: GECAM-B observation of a long burst
  36. GRB 251214B: Fermi GBM Observation
  37. GRB 251209A: Insight-HXMT/HE detection
  38. GRB 251215A: Swift ToO observations
  39. EP251214b (EP trigger 01709250023): LCO optical limits
  40. GRID detection of GRB 251213A
  41. GRB 251203B: AbAO optical observations
  42. GRB 251215A: Swift/BAT-GUANO arcminute localization of a burst
  43. GRB 251214B: GECAM-B observation of a long burst
  44. GRB 251214B: Swift-XRT refined Analysis
  45. GRB 251213A: SVOM/GRM observation
  46. EP251214a: KAIT optical upper limit
  47. GRB 251214D: AstroSat CZTI detection of a long burst
  48. GRB 251213A: AstroSat CZTI detection
  49. GRB 251214A: AstroSat CZTI detection
  50. GRB 251213A: GECAM-B detection
  51. GRB 251214B: Swift/UVOT Detection
  52. GRB 251215A: Fermi GBM Final Real-time Localization
  53. GRB 251214B: COLIBRÍ observations of the afterglow
  54. EP251214a: EP-FXT non-detection and upper limit
  55. GRB 251214A: GECAM-B observation of a likely long burst
  56. GRB 251214B: 1.3m DFOT optical detection
  57. EP251214a: Global MASTER-Net observations report
  58. GRB 251214B: Enhanced Swift-XRT position
  59. GRB 251214B: Xinglong-2.16m optical observation
  60. GRB 251214C: Fermi GBM Final Localization
  61. GRB 251214B : MASTER optical afterglow detection
  62. Fermi trigger No 787396657: Global MASTER-Net observations report
  63. GRB 251214B: SVOM/C-GFT optical observations
  64. EP251214a: COLIBRÍ optical upper limit
  65. Swift GRB 251214B: Global MASTER-Net observations report
  66. EP251214.305: COLIBRÍ optical upper limit
  67. GRB 251214B: Swift detection of a burst with an optical counterpart
  68. GRB 251214B: Fermi GBM Final Real-time Localization
  69. EP251214a: EP-WXT detection of an X-ray transient possibly associated with GRB 251214A
  70. Fermi GRB 251214A: Global MASTER-Net observations report
  71. GRB 251214A: Fermi GBM Final Real-time Localization
  72. EP251212a: Global MASTER-Net observations report
  73. EP251212a: KAIT optical upper limit
  74. EP251212a / GRB 251212A: AstroSat CZTI detection
  75. EP251212a: EP-FXT follow-up observation
  76. GRB 251211B: AstroSat CZTI detection
  77. IceCube-251210A: No Candidate Transients from the Zwicky Transient Facility
  78. GRB 251209A: NuSTAR detection of prompt emission
  79. EP251212a : COLIBRÍ optical upper limit
  80. EP251212a: Einstein Probe detection of an X-ray transient
  81. Fermi-LAT Gamma-ray Observations of IceCube-251210A
  82. IceCube-251210A: Upper limits from a search for additional neutrino events in IceCube
  83. Fermi GRB 251211B: Global MASTER-Net observations report
  84. GRB 251211B: Fermi GBM Final Real-time Localization
  85. IceCube-251210A: DDOTI Optical Upper Limit
  86. SVOM GRB251211.12: Global MASTER-Net observations report
  87. GRB 251211A: Fermi GBM Final Real-time Localization
  88. GRB 251209A: Fermi GBM observation
  89. GRB 251205A: 1.3m DFOT optical upper limit
  90. GRB 251209A: AstroSat CZTI detection
  91. IceCube Alert 251210.46: Global MASTER-Net observations report
  92. IceCube-251210A - IceCube observation of a high-energy neutrino candidate track-like event
  93. EP251124a: Mondy optical upper limit
  94. GRB 251129A/EP251129a: AbAO and Mondy optical observations
  95. EP251130a: Mondy and AbAO optical observations
  96. GRB 251208A: AstroSat CZTI detection
  97. Fermi GBM Sub-Threshold Detection of GRB 251205A
  98. GRB 251208A: Glowbug gamma-ray detection
  99. GRB 251208B: COLIBRÍ optical upper limits
  100. EP251118a / GRB 251118C: VLT/MUSE redshift confirmation

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