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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"

6770 results found.

  1. GRB 260903A: Swift-XRT observations
  2. GRB 260903A: SAO RAS optical upper limit
  3. EP260903a: EP-FXT follow-up observation
  4. GRB 260903A: SAO RAS optical observations
  5. NuSTAR Transient 260828: SOAR Optical Upper Limits
  6. EP260901a: EP-FXT follow-up observation
  7. EP260830a: EP-FXT follow-up observation
  8. NuSTAR Transient 260828: LCO Optical Upper Limits
  9. Fermi-LAT Gamma-ray Observations of IceCube-260827A
  10. Fermi-LAT Gamma-ray Observations of IceCube-260825A
  11. GRB 260829A: Fermi GBM Detection
  12. GRB 260818B: Further EP-FXT observation
  13. GRB 260808B: SAO RAS observations of the optical rebrightening
  14. GRB 260807A: EP-FXT follow-up observations
  15. GRB 260822A: EP/FXT follow-up observations
  16. GRB 260822A: GROWTH-India Telescope Upper Limits
  17. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  18. Fermi-LAT Gamma-ray Observations of IceCube-260807A
  19. GRB 260818B: EP-FXT follow-up observation
  20. GRB260818A: EP-FXT follow-up observation
  21. EP260806a: SAO RAS multicolor optical observations
  22. EP260812b: Optical upper limit with Kinder
  23. EP260812a: NOT and Liverpool Telescope upper limits:
  24. GRB 260809A: SAO RAS optical observations
  25. GRB 260808B: SAO RAS optical observations
  26. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  27. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  28. AT 2026wki: EP/FXT follow-up observations
  29. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  30. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  31. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  32. EP260727a: SAO RAS optical observations
  33. EP260728a: EP-FXT follow-up observation
  34. GRB 260726A: EP-FXT follow-up observations
  35. GRB 260726A: Fermi GBM Observation
  36. Konus-Wind detection of GRB 260727A
  37. GRB 260727A: EP/FXT follow-up observations
  38. EP260723a: further EP-FXT follow-up observation
  39. EP260725a: EP-WXT detection of an X-ray transient
  40. EP260723a: EP-FXT follow-up observation
  41. GRB 260718A: EP-FXT follow-up observation
  42. GRB 260718A: Fermi GBM Observation
  43. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  44. GRB 260618B: EP-FXT follow-up observation upper limit
  45. GRB 260714B: Fermi-LAT detection
  46. GRB 260714B: Fermi GBM Detection
  47. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  48. EP260711a: EP-FXT follow-up observation
  49. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  50. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  51. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  52. GRB 260710A: Fermi GBM Detection
  53. GRB 260708A: Fermi-GBM observation
  54. GRB 260708A: Fermi-LAT detection
  55. GRB 260706A: Further EP-FXT follow-up observation
  56. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  57. GRB 260706A: EP-FXT follow-up observation
  58. GRB 260706A: Fermi GBM Observation
  59. GRB 260704A: EP-FXT follow-up observation
  60. EP260703a: EP-FXT follow-up observation
  61. EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
  62. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  63. EP260628a: EP-FXT follow-up observation
  64. EP260626a: EP-FXT follow-up observation
  65. Konus-Wind detection of GRB 260623B / EP260623a
  66. GRB 260618A: Fermi GBM Observation
  67. EP260623a: Optical follow-up observations with Kinder
  68. GRB 260614B: EP-FXT follow-up observation
  69. GRB 260618B: Fermi GBM Observation
  70. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  71. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  72. EP260618a: EP-FXT follow-up observation
  73. GRB 260618B: Fermi-LAT detection
  74. EP260618a: EP-WXT detection of an X-ray transient
  75. EP260616a/GRB 260616B: EP-FXT follow-up observation
  76. GRB 260617A: Fermi GBM Detection
  77. GRB 260616A: Fermi GBM Observation
  78. GRB 260616A: Fermi-LAT detection
  79. GRB 260616B: Fermi GBM Detection
  80. GRB 260614B: Fermi GBM Observation
  81. GRB 260610B: Fermi GBM Observation
  82. GRB 260610B / AT2026owq: further SAO RAS optical observations
  83. IceCube-260610A: EP-FXT follow-up observation
  84. GRB 260610B / AT2026owq: OASDG optical observations
  85. GRB 260610B / AT2026owq: SAO RAS optical observations
  86. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  87. GRB 260608A: Fermi GRB Observation
  88. GRB 260604C: further SAO RAS optical observations
  89. EP260605a: EP-FXT follow-up observation
  90. GRB 260607B: Fermi GBM Observation
  91. GRB 260607B: Fermi-LAT detection
  92. GRB 260604C: SAO RAS optical observations
  93. EP260602d: EP-FXT follow-up observation
  94. EP260602c: EP-FXT follow-up observation
  95. GRB 260604C: Fermi GBM Observation
  96. EP260602a: EP-FXT follow-up observation
  97. EP260602d: Optical Upper limits with kinder observations
  98. GRB 260603A: EP-FXT follow-up observation
  99. EP260601a/GRB 260601B: EP-FXT follow-up observation
  100. EP260602b: EP-FXT follow-up observation

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