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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"

6773 results found.

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

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