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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"

6772 results found.

  1. GRB 260914A: EP-FXT follow-up observation
  2. GRB 260909A: OSN 1.5m, CAHA 2.2m and GTC 10.4m optical upper limits
  3. GRB 260903A: Swift-XRT observations
  4. GRB 260903A: SAO RAS optical upper limit
  5. EP260903a: EP-FXT follow-up observation
  6. GRB 260903A: SAO RAS optical observations
  7. NuSTAR Transient 260828: SOAR Optical Upper Limits
  8. EP260901a: EP-FXT follow-up observation
  9. EP260830a: EP-FXT follow-up observation
  10. NuSTAR Transient 260828: LCO Optical Upper Limits
  11. Fermi-LAT Gamma-ray Observations of IceCube-260827A
  12. Fermi-LAT Gamma-ray Observations of IceCube-260825A
  13. GRB 260829A: Fermi GBM Detection
  14. GRB 260818B: Further EP-FXT observation
  15. GRB 260808B: SAO RAS observations of the optical rebrightening
  16. GRB 260807A: EP-FXT follow-up observations
  17. GRB 260822A: EP/FXT follow-up observations
  18. GRB 260822A: GROWTH-India Telescope Upper Limits
  19. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  20. Fermi-LAT Gamma-ray Observations of IceCube-260807A
  21. GRB 260818B: EP-FXT follow-up observation
  22. GRB260818A: EP-FXT follow-up observation
  23. EP260806a: SAO RAS multicolor optical observations
  24. EP260812b: Optical upper limit with Kinder
  25. EP260812a: NOT and Liverpool Telescope upper limits:
  26. GRB 260809A: SAO RAS optical observations
  27. GRB 260808B: SAO RAS optical observations
  28. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  29. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  30. AT 2026wki: EP/FXT follow-up observations
  31. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  32. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  33. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  34. EP260727a: SAO RAS optical observations
  35. EP260728a: EP-FXT follow-up observation
  36. GRB 260726A: EP-FXT follow-up observations
  37. GRB 260726A: Fermi GBM Observation
  38. Konus-Wind detection of GRB 260727A
  39. GRB 260727A: EP/FXT follow-up observations
  40. EP260723a: further EP-FXT follow-up observation
  41. EP260725a: EP-WXT detection of an X-ray transient
  42. EP260723a: EP-FXT follow-up observation
  43. GRB 260718A: EP-FXT follow-up observation
  44. GRB 260718A: Fermi GBM Observation
  45. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  46. GRB 260618B: EP-FXT follow-up observation upper limit
  47. GRB 260714B: Fermi-LAT detection
  48. GRB 260714B: Fermi GBM Detection
  49. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  50. EP260711a: EP-FXT follow-up observation
  51. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  52. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  53. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  54. GRB 260710A: Fermi GBM Detection
  55. GRB 260708A: Fermi-GBM observation
  56. GRB 260708A: Fermi-LAT detection
  57. GRB 260706A: Further EP-FXT follow-up observation
  58. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  59. GRB 260706A: EP-FXT follow-up observation
  60. GRB 260706A: Fermi GBM Observation
  61. GRB 260704A: EP-FXT follow-up observation
  62. EP260703a: EP-FXT follow-up observation
  63. EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
  64. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  65. EP260628a: EP-FXT follow-up observation
  66. EP260626a: EP-FXT follow-up observation
  67. Konus-Wind detection of GRB 260623B / EP260623a
  68. GRB 260618A: Fermi GBM Observation
  69. EP260623a: Optical follow-up observations with Kinder
  70. GRB 260614B: EP-FXT follow-up observation
  71. GRB 260618B: Fermi GBM Observation
  72. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  73. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  74. EP260618a: EP-FXT follow-up observation
  75. GRB 260618B: Fermi-LAT detection
  76. EP260618a: EP-WXT detection of an X-ray transient
  77. EP260616a/GRB 260616B: EP-FXT follow-up observation
  78. GRB 260617A: Fermi GBM Detection
  79. GRB 260616A: Fermi GBM Observation
  80. GRB 260616A: Fermi-LAT detection
  81. GRB 260616B: Fermi GBM Detection
  82. GRB 260614B: Fermi GBM Observation
  83. GRB 260610B: Fermi GBM Observation
  84. GRB 260610B / AT2026owq: further SAO RAS optical observations
  85. IceCube-260610A: EP-FXT follow-up observation
  86. GRB 260610B / AT2026owq: OASDG optical observations
  87. GRB 260610B / AT2026owq: SAO RAS optical observations
  88. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  89. GRB 260608A: Fermi GRB Observation
  90. GRB 260604C: further SAO RAS optical observations
  91. EP260605a: EP-FXT follow-up observation
  92. GRB 260607B: Fermi GBM Observation
  93. GRB 260607B: Fermi-LAT detection
  94. GRB 260604C: SAO RAS optical observations
  95. EP260602d: EP-FXT follow-up observation
  96. EP260602c: EP-FXT follow-up observation
  97. GRB 260604C: Fermi GBM Observation
  98. EP260602a: EP-FXT follow-up observation
  99. EP260602d: Optical Upper limits with kinder observations
  100. GRB 260603A: EP-FXT follow-up observation

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