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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"

14832 results found.

  1. GRB 260601A: Fermi GBM Final Real-time Localization
  2. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  3. GRB 260531C: Fermi GBM Final Localization Correction
  4. AT2026nik: EP-FXT X-ray counterpart
  5. GRB 260531B: Fermi GBM Final Real-time Localization
  6. GRB 260531A: MAXI/GSC detection
  7. IPN triangulation of GRB 260527A / EP260527a
  8. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  9. GRB 260530A: Fermi GBM Final Real-time Localization
  10. GRB 260527A / EP260527a: VLA radio detection
  11. GRB 260527A/EP260527a: Insight-HXMT detection
  12. GRB 260529A: Fermi GBM Final Real-time Localization
  13. EP260526a: SVOM/VT optical upper limits
  14. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  15. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  16. EP260527a/GRB 260527A: EP-FXT follow-up observation
  17. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  18. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  19. EP260526a: EP-FXT follow-up observation
  20. EP260527a: COLIBRÍ optical detection
  21. EP260527a: Einstein Probe detection of a fast X-ray transient
  22. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  23. EP260526a: LCO optical upper limits
  24. EP260526a: Einstein Probe detection of a fast X-ray transient
  25. GRB 260525A: AstroSat CZTI detection
  26. GRB 260526A: Fermi GBM Final Real-time Localization
  27. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  28. GRB 260525A: Fermi GBM Final Real-time Localization
  29. GRB 260523B: AstroSat CZTI detection
  30. GRB 260523B: Fermi GBM Final Real-time Localization
  31. GRB 260523A: Fermi GBM Final Real-time Localization
  32. GRB 260522B: NuSTAR detection of prompt emission
  33. GRB 260522B: Fermi GBM Final Real-time Localization
  34. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  35. GRB 260522A: Fermi-LAT detection
  36. GRB 260522A: Fermi GBM Final Real-time Localization
  37. GRB 260511A: iTelescope T-75 optical detection
  38. GRB 260411B: TERI Gamma-ray detection
  39. GRB 260407A: TERI Gamma-ray detection
  40. GRB 260307A: TERI Gamma-ray detection
  41. GRB 260225D: TERI Gamma-ray detection
  42. GRB 251118A: TERI Gamma-ray detection
  43. GRB 251113A: TERI Gamma-ray detection
  44. GRB 260428A: TERI Gamma-ray detection
  45. Konus-Wind detection of GRB 260519C
  46. GRB 260520B: Fermi GBM Final Localization
  47. GRB 260520A: Fermi GBM Final Localization
  48. GRB 260519D: Fermi GBM Final Localization Correction
  49. GRB 260519C: NuSTAR detection of prompt emission
  50. Konus-Wind detection of GRB 260518A
  51. GRB 260519B: Fermi GBM Final Localization
  52. GRB 260519A: Fermi GBM Final Localization
  53. GRB 260518A: AstroSat CZTI detection of a long burst
  54. GRB 260421B: radio detection with the VLA
  55. GRID detection of GRB 260511A
  56. GRB 260516D: GOTO optical counterpart detection
  57. GRB 260515A: further Liverpool Telescope observations
  58. GRB 260516D: GROWTH-India Telescope optical detection
  59. GRB 260516D: FRAM-ORM optical limit
  60. GRB 260515A: CrAO ZTSh BVRI optical observations
  61. GRB 260516D: SVOM possible detection of a burst
  62. GRB 260516C: Fermi GBM Final Real-time Localization
  63. Konus-Wind detection of GRB 260515A
  64. GRB 260515A: Liverpool Telescope optical detection
  65. GRB 260515A: LCO optical counterpart detection
  66. GRB 260515A: EP-FXT follow-up observation
  67. EP260514a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  68. EP260514a: NOT optical counterpart confirmation
  69. EP260514a: TRT optical counterpart candidate
  70. GRB 260516B: Fermi GBM Final Real-time Localization
  71. GRB 260515A: SVOM/VT optical observations
  72. GRB 260515A: OHP/T193 optical observations
  73. GRB 260516A: Fermi GBM Final Real-time Localization
  74. GRID detection of GRB 260507A
  75. GRB 260515A: GTC/OSIRIS+ spectroscopic redshift z = 0.764
  76. GRB 260515A: LCO optical observations
  77. GRB 260515A: NOT optical observations.
  78. SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection
  79. GRB 260515A: SVOM/VT optical candidate from VHF data
  80. GRB 260515A: JinShan optical counterpart candidate
  81. GRB 260515A: SVOM detection of a burst
  82. GRB 260510C: Glowbug gamma-ray detection
  83. Konus-Wind detection of GRB 260512A
  84. GRB 260510C: CALET Gamma-Ray Burst Monitor detection
  85. EP260514a: Einstein Probe detection of a fast X-ray transient
  86. EP260512a: LCO optical upper limits
  87. IPN triangulation of GRB 260512A
  88. GRB 260512A: AstroSat CZTI detection
  89. EP260512a: EP-FXT follow-up observation
  90. EP260507a: Xinglong Schmidt optical counterpart detection
  91. GRB 260514A: Fermi GBM Final Real-time Localization
  92. GRB 260513A: Fermi GBM Final Real-time Localization
  93. Konus-Wind detection of GRB 260511B
  94. EP260512a: Einstein Probe detection of an X-ray transient
  95. GRB 260512A: NuSTAR detection of prompt emission
  96. GRB 260512A: Fermi GBM Final Real-time Localization
  97. GRB 260511A: Glowbug gamma-ray detection
  98. Konus-Wind detection of GRB 260511A
  99. MASS-Cube (GRID 2.0) detection of GRB 260511A
  100. MASS-Cube (GRID 2.0) detection of GRB 260507A

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