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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"

27553 results found.

  1. GRB 251230A: Swift/UVOT detection
  2. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  3. EP251229a: BOOTES-2 early optical upper limit
  4. GRB 251230A: Enhanced Swift-XRT position
  5. GRB 251230A: Early optical counterpart detection by LCO.
  6. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  7. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  8. EP251229a: Einstein Probe detection of an X-ray transient
  9. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  10. GRB 251226A: Glowbug gamma-ray detection
  11. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  12. GRB 251228A: Fermi GBM Final Real-time Localization
  13. GRB 251226A: GECAM-B detection
  14. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  15. GRB 251222A/EP251222b: Optical detection with Kinder observations
  16. EP251222a: Optical upper limit with Kinder observations
  17. GRB 251205A: Kilonova-Catcher optical afterglow detection
  18. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  19. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  20. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  21. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  22. GRB 251222A: Continued 1.3m DFOT optical observation
  23. EP251220a: 3.6m DOT optical afterglow detection
  24. GRB 251222A: Fermi GBM Observation
  25. Konus-Wind detection of GRB 251222A / EP251222b
  26. GRB 251222A: Swift-XRT afterglow detection
  27. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  28. GRB 251222A / EP251222b: GOTO optical counterpart detection
  29. GRB 251222A: 1.3m DFOT optical detection
  30. GRB251221A: 7DT optical upper limits
  31. EP251222a: GSP Optical Counterpart Detection
  32. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  33. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  34. EP251222a: Einstein Probe detection of an X-ray transient
  35. GRB 251222A: PRIME near-infrared detection
  36. GRB 251222A: NOT optical observations
  37. IPN triangulation of GRB 251220B (short)
  38. GRB 251222A: Swift ToO observations
  39. GRB 251222A: SVOM detection of a long burst
  40. GRB 251222A: Fermi GBM Final Real-time Localization
  41. GRB 251221A: PRIME near-infrared observation
  42. GRB 251221A: UAFO and Mondy optical upper limit
  43. GRB 251221A: Swift-XRT refined Analysis
  44. EP251221a: Einstein Probe detection of a fast X-ray transient
  45. GRB 251221A: Swift/UVOT Upper Limits
  46. GRB 251221A: Enhanced Swift-XRT position
  47. GRB 251221B: Fermi GBM Final Real-time Localization
  48. EP251220a: EP-FXT follow-up observation
  49. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  50. EP 251220a: GOTO optical counterpart detection
  51. GRB 251221A: COLIBRÍ detection of the optical counterpart
  52. EP 251220a: COLIBRÍ detection of the optical counterpart
  53. GRB 251221A: Swift detection of a burst
  54. GRB 251221A: Fermi GBM Final Real-time Localization
  55. EP251220a: EP detection of a fast X-ray transient
  56. GRB 251220B: Fermi GBM Final Real-time Localization
  57. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  58. GRB 251220A: MAXI/GSC detection
  59. GRB 251215A: Swift-XRT afterglow detection
  60. IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
  61. GRB 251214B: VIRT Optical Upper Limit
  62. GRB 251217A: Fermi GBM Final Real-time Localization
  63. GRB 251215A: Swift/UVOT Upper LImits
  64. GRB 251215A: Fermi GBM Observation
  65. GRB 251215A: COLIBRÍ optical upper limit
  66. GRB 251216A: Fermi GBM Final Real-time Localization
  67. GRB 251215A: Swift-XRT observations
  68. EP251214a: Optical upper limit with Kinder observations
  69. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  70. GRB 251215A: Glowbug gamma-ray detection
  71. GRB 251214B: VLT/X-shooter observations
  72. GRB 251213A: GRID-10B observation
  73. GRB 251202A: radio detection with the VLA
  74. EP251214b : Einstein Probe detection of a fast X-ray transient
  75. EP251214b : Einstein Probe detection of a fast X-ray transient
  76. GRB 251214B: AbAO optical observations
  77. GRB 251214B: LCO detection of the optical counterpart
  78. GRB 251209A: Insight-HXMT/HE detection
  79. GRB 251215A: Swift ToO observations
  80. EP251214b (EP trigger 01709250023): LCO optical limits
  81. GRID detection of GRB 251213A
  82. GRB 251215A: Swift/BAT-GUANO arcminute localization of a burst
  83. GRB 251214B: Swift-XRT refined Analysis
  84. GRB 251214D: AstroSat CZTI detection of a long burst
  85. GRB 251213A: AstroSat CZTI detection
  86. GRB 251214A: AstroSat CZTI detection
  87. GRB 251213A: GECAM-B detection
  88. GRB 251214B: Swift/UVOT Detection
  89. GRB 251215A: Fermi GBM Final Real-time Localization
  90. GRB 251214B: COLIBRÍ observations of the afterglow
  91. EP251214a: EP-FXT non-detection and upper limit
  92. GRB 251214B: 1.3m DFOT optical detection
  93. GRB 251214B: Enhanced Swift-XRT position
  94. GRB 251214B: Xinglong-2.16m optical observation
  95. GRB 251214C: Fermi GBM Final Localization
  96. GRB 251214B : MASTER optical afterglow detection
  97. GRB 251214B: Swift detection of a burst with an optical counterpart
  98. GRB 251214B: Fermi GBM Final Real-time Localization
  99. EP251214a: EP-WXT detection of an X-ray transient possibly associated with GRB 251214A
  100. GRB 251214A: Fermi GBM Final Real-time Localization

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