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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').
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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"

6759 results found.

  1. GRB 260818B: Further EP-FXT observation
  2. GRB 260808B: SAO RAS observations of the optical rebrightening
  3. GRB 260807A: EP-FXT follow-up observations
  4. GRB 260822A: EP/FXT follow-up observations
  5. GRB 260822A: GROWTH-India Telescope Upper Limits
  6. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  7. Fermi-LAT Gamma-ray Observations of IceCube-260807A
  8. GRB 260818B: EP-FXT follow-up observation
  9. GRB260818A: EP-FXT follow-up observation
  10. EP260806a: SAO RAS multicolor optical observations
  11. EP260812b: Optical upper limit with Kinder
  12. EP260812a: NOT and Liverpool Telescope upper limits:
  13. GRB 260809A: SAO RAS optical observations
  14. GRB 260808B: SAO RAS optical observations
  15. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  16. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  17. AT 2026wki: EP/FXT follow-up observations
  18. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  19. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  20. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  21. EP260727a: SAO RAS optical observations
  22. EP260728a: EP-FXT follow-up observation
  23. GRB 260726A: EP-FXT follow-up observations
  24. GRB 260726A: Fermi GBM Observation
  25. Konus-Wind detection of GRB 260727A
  26. GRB 260727A: EP/FXT follow-up observations
  27. EP260723a: further EP-FXT follow-up observation
  28. EP260725a: EP-WXT detection of an X-ray transient
  29. EP260723a: EP-FXT follow-up observation
  30. GRB 260718A: EP-FXT follow-up observation
  31. GRB 260718A: Fermi GBM Observation
  32. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  33. GRB 260618B: EP-FXT follow-up observation upper limit
  34. GRB 260714B: Fermi-LAT detection
  35. GRB 260714B: Fermi GBM Detection
  36. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  37. EP260711a: EP-FXT follow-up observation
  38. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  39. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  40. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  41. GRB 260710A: Fermi GBM Detection
  42. GRB 260708A: Fermi-GBM observation
  43. GRB 260708A: Fermi-LAT detection
  44. GRB 260706A: Further EP-FXT follow-up observation
  45. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  46. GRB 260706A: EP-FXT follow-up observation
  47. GRB 260706A: Fermi GBM Observation
  48. GRB 260704A: EP-FXT follow-up observation
  49. EP260703a: EP-FXT follow-up observation
  50. EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
  51. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  52. EP260628a: EP-FXT follow-up observation
  53. EP260626a: EP-FXT follow-up observation
  54. Konus-Wind detection of GRB 260623B / EP260623a
  55. GRB 260618A: Fermi GBM Observation
  56. EP260623a: Optical follow-up observations with Kinder
  57. GRB 260614B: EP-FXT follow-up observation
  58. GRB 260618B: Fermi GBM Observation
  59. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  60. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  61. EP260618a: EP-FXT follow-up observation
  62. GRB 260618B: Fermi-LAT detection
  63. EP260618a: EP-WXT detection of an X-ray transient
  64. EP260616a/GRB 260616B: EP-FXT follow-up observation
  65. GRB 260617A: Fermi GBM Detection
  66. GRB 260616A: Fermi GBM Observation
  67. GRB 260616A: Fermi-LAT detection
  68. GRB 260616B: Fermi GBM Detection
  69. GRB 260614B: Fermi GBM Observation
  70. GRB 260610B: Fermi GBM Observation
  71. GRB 260610B / AT2026owq: further SAO RAS optical observations
  72. IceCube-260610A: EP-FXT follow-up observation
  73. GRB 260610B / AT2026owq: OASDG optical observations
  74. GRB 260610B / AT2026owq: SAO RAS optical observations
  75. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  76. GRB 260608A: Fermi GRB Observation
  77. GRB 260604C: further SAO RAS optical observations
  78. EP260605a: EP-FXT follow-up observation
  79. GRB 260607B: Fermi GBM Observation
  80. GRB 260607B: Fermi-LAT detection
  81. GRB 260604C: SAO RAS optical observations
  82. EP260602d: EP-FXT follow-up observation
  83. EP260602c: EP-FXT follow-up observation
  84. GRB 260604C: Fermi GBM Observation
  85. EP260602a: EP-FXT follow-up observation
  86. EP260602d: Optical Upper limits with kinder observations
  87. GRB 260603A: EP-FXT follow-up observation
  88. EP260601a/GRB 260601B: EP-FXT follow-up observation
  89. EP260602b: EP-FXT follow-up observation
  90. EP260602a: Optical upper limits with Kinder observations
  91. GRB 260601A: Fermi GBM Observation
  92. AT2026nik: EP-FXT X-ray counterpart
  93. EP260527a/GRB 260527A: EP-FXT follow-up observation
  94. EP260526a: EP-FXT follow-up observation
  95. GRB 260522A: Fermi GBM Observation
  96. GRB 260522A: Fermi-LAT detection
  97. Konus-Wind detection of GRB 260515A
  98. GRB 260515A: EP-FXT follow-up observation
  99. EP260514a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  100. GRB 260515A: NOT optical observations.

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