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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

6829 results found.

  1. EP261015a: VST optical observations
  2. EP261015a: GSP multiband optical follow-up observations
  3. EP261015a: Further optical observations with the 1.3m DFOT
  4. Fermi-LAT Gamma-ray Observations of IceCube-261020A
  5. GRB 261020A: Fermi GBM Observation
  6. EP261015a: Wendelstein 43 cm optical observations
  7. EP261015a: Follow-up with the 1.3m DFOT
  8. GRB 261017A: R-band upper limit with the 1.3-m DFOT
  9. GRB 261017A: Swift-XRT refined Analysis
  10. GRB 261017A: Fermi GBM Observation
  11. EP261015a: Tentative fading of the candidate optical counterpart from the NOT
  12. EP261006a / AT 2026aetp: Optical follow-up with the 1.3-m DFOT
  13. GRB 261011A: 1.3m DFOT optical upper limit
  14. EP261015a (WXT 11900947714): Possible optical counterpart from NOT and LCO
  15. GRB 261011A: SAO RAS and AbAO optical observations
  16. GRB 261010A: initial pulse rest-frame energetics from Konus-Wind detection
  17. Fermi-LAT Gamma-ray Observations of IceCube-261012A
  18. GRB 261010A: Swift-XRT refined Analysis
  19. GRB 261011A: Swift-XRT refined Analysis
  20. GRB 261010A: a Type I-L (merger-driven) GRB candidate
  21. Konus-Wind detection of GRB 261007A/EP261007a
  22. GRB 261011A: GMG Optical Observation
  23. GRB 261010A: Fermi GBM Observation
  24. GRB 261011A: Optical follow-up observations with Kinder
  25. EP261010a: NOT optical upper limits
  26. EP261006a: Xinglong 2.16m/BFOSC optical follow-up observations
  27. EP261007b: NOT optical observations, variable source outside the FXT region
  28. EP261006a: Swift/XRT detection of the fading X-ray counterpart
  29. GRB 261007A/EP261007a: Optical follow-up observations with Kinder
  30. EP261006a: Optical follow-up observations with Kinder
  31. GRB 261007A: Swift-XRT afterglow detection
  32. GRB 261007A: Fermi GBM observation
  33. GRB 261005B: Swift-XRT refined Analysis
  34. GRB 261005B: Fermi GBM Observation
  35. EP#01709320865: Swift-XRT observations
  36. Konus-Wind detection of GRB 260919A / EP 260920a
  37. Fermi-LAT Gamma-ray Observations of IceCube-260930A
  38. EP260927a: Einstein Probe detection of a fast X-ray transient
  39. GRB 260925A: Swift-XRT refined Analysis
  40. EP260924a: EP-FXT follow-up observation
  41. Konus-Wind detection of GRB 260924A
  42. GRB 260924A: Optical follow-up observations with Kinder
  43. GRB 260924A: Swift-XRT refined Analysis
  44. Konus-Wind detection of GRB 260921A (correction to GCN 45722)
  45. GRB 260924A: Fermi GRB Observation
  46. Konus-Wind detection of GRB 260921A (possible merger-origin)
  47. GRB 260924A: Fermi-LAT detection of a bright burst
  48. Fermi-LAT Gamma-ray Observations of IceCube-260919A
  49. Fermi-LAT Gamma-ray Observations of IceCube-260916A
  50. GRB 260922A: Swift-XRT refined Analysis
  51. Fermi-LAT Gamma-ray Observations of IceCube-260805A
  52. GRB 260921A: Fermi GBM Observation
  53. EP260920a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  54. EP260917a: refined analysis of the EP-FXT observations
  55. GRB 260915A: Swift-XRT afterglow detection
  56. GRB 260916B: Fermi GBM Detection
  57. GRB 260909A: Swift-XRT observations
  58. GRB 260914A: EP-FXT follow-up observation
  59. GRB 260909A: OSN 1.5m, CAHA 2.2m and GTC 10.4m optical upper limits
  60. GRB 260903A: Swift-XRT observations
  61. GRB 260903A: SAO RAS optical upper limit
  62. EP260903a: EP-FXT follow-up observation
  63. GRB 260903A: SAO RAS optical observations
  64. NuSTAR Transient 260828: SOAR Optical Upper Limits
  65. EP260901a: EP-FXT follow-up observation
  66. EP260830a: EP-FXT follow-up observation
  67. NuSTAR Transient 260828: LCO Optical Upper Limits
  68. Fermi-LAT Gamma-ray Observations of IceCube-260827A
  69. Fermi-LAT Gamma-ray Observations of IceCube-260825A
  70. GRB 260829A: Fermi GBM Detection
  71. GRB 260818B: Further EP-FXT observation
  72. GRB 260808B: SAO RAS observations of the optical rebrightening
  73. GRB 260807A: EP-FXT follow-up observations
  74. GRB 260822A: EP/FXT follow-up observations
  75. GRB 260822A: GROWTH-India Telescope Upper Limits
  76. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  77. Fermi-LAT Gamma-ray Observations of IceCube-260807A
  78. GRB 260818B: EP-FXT follow-up observation
  79. GRB260818A: EP-FXT follow-up observation
  80. EP260806a: SAO RAS multicolor optical observations
  81. EP260812b: Optical upper limit with Kinder
  82. EP260812a: NOT and Liverpool Telescope upper limits:
  83. GRB 260809A: SAO RAS optical observations
  84. GRB 260808B: SAO RAS optical observations
  85. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  86. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  87. AT 2026wki: EP/FXT follow-up observations
  88. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  89. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  90. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  91. EP260727a: SAO RAS optical observations
  92. EP260728a: EP-FXT follow-up observation
  93. GRB 260726A: EP-FXT follow-up observations
  94. GRB 260726A: Fermi GBM Observation
  95. Konus-Wind detection of GRB 260727A
  96. GRB 260727A: EP/FXT follow-up observations
  97. EP260723a: further EP-FXT follow-up observation
  98. EP260725a: EP-WXT detection of an X-ray transient
  99. EP260723a: EP-FXT follow-up observation
  100. GRB 260718A: EP-FXT follow-up observation

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