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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"

28096 results found.

  1. GRB 260604C: SVOM detection of a long burst
  2. GRB 260604C: Fermi GBM Final Real-time Localization
  3. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  4. GRB 260603A: NOT optical observations
  5. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  6. GRB 260604B: Fermi GBM Final Real-time Localization
  7. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  8. EP260602a: EP-FXT follow-up observation
  9. EP260603a: Einstein Probe detection of a fast X-ray transient
  10. EP260602d: Optical Upper limits with kinder observations
  11. GRB 260604A: Fermi GBM Final Real-time Localization
  12. EP260602b: Liverpool Telescope observations
  13. GRB 260603B: Fermi GBM Final Localization
  14. Konus-Wind detection of GRB 260601B/EP260601a
  15. EP260602b: EP-FXT follow-up observation
  16. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  17. EP260602d: Einstein Probe detection of a fast X-ray transient
  18. EP260602c: Einstein Probe detection of a fast X-ray transient
  19. EP260602a: COLIBRÍ optical observations
  20. GRB 260603A: SVOM detection of a burst
  21. EP260602b: Einstein Probe detection of a fast X-ray transient
  22. GRB 260601B/EP260601a: Insight-HXMT detection
  23. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  24. GRB 260602B: Fermi GBM Final Localization
  25. GRB 260602A: Fermi GBM Final Real-time Localization
  26. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  27. EP260602a: Optical upper limits with Kinder observations
  28. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  29. EP260602a: Einstein Probe detection of a fast X-ray transient
  30. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  31. EP260601a: Einstein Probe detection of an X-ray transient
  32. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  33. GRB 260601A: Glowbug gamma-ray detection of a short burst
  34. GRB 260531B: Glowbug gamma-ray detection
  35. GRB 260516D: VLA radio detection
  36. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  37. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  38. GRB 260601A: Fermi GBM Final Real-time Localization
  39. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  40. GRB 260531C: Fermi GBM Final Localization Correction
  41. AT2026nik: EP-FXT X-ray counterpart
  42. GRB 260531B: Fermi GBM Final Real-time Localization
  43. GRB 260531A: MAXI/GSC detection
  44. AT 2026nuz: COLIBRÍ optical observations
  45. IPN triangulation of GRB 260527A / EP260527a
  46. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  47. GRB 260530A: Fermi GBM Final Real-time Localization
  48. GRB 260527A / EP260527a: VLA radio detection
  49. GRB 260529A: GOTO tentative optical afterglow candidate
  50. GRB 260527A/EP260527a: Insight-HXMT detection
  51. GRB 260529A: Fermi GBM Final Real-time Localization
  52. EP260526a: SVOM/VT optical upper limits
  53. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  54. EP260527a / GRB 260527A: NOT optical observations
  55. GRB 260527A/EP260527a: FTW optical and NIR observations
  56. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  57. EP260527a/GRB 260527A: EP-FXT follow-up observation
  58. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  59. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  60. EP260526a: EP-FXT follow-up observation
  61. EP260527a: COLIBRÍ optical detection
  62. EP260527a: Einstein Probe detection of a fast X-ray transient
  63. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  64. EP260526a: LCO optical upper limits
  65. EP260526a: Einstein Probe detection of a fast X-ray transient
  66. GRB 260525A: AstroSat CZTI detection
  67. GRB 260526A: Fermi GBM Final Real-time Localization
  68. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  69. GRB 260525A: Fermi GBM Final Real-time Localization
  70. GRB 260523B: AstroSat CZTI detection
  71. GRB 260523B: Fermi GBM Final Real-time Localization
  72. GRB 260523A: Fermi GBM Final Real-time Localization
  73. GRB 260522B: NuSTAR detection of prompt emission
  74. GRB 260522B: Fermi GBM Final Real-time Localization
  75. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  76. GRB 260522A: Fermi-LAT detection
  77. GRB 260522A: Fermi GBM Final Real-time Localization
  78. GRB 260511A: iTelescope T-75 optical detection
  79. GRB 260411B: TERI Gamma-ray detection
  80. GRB 260407A: TERI Gamma-ray detection
  81. GRB 260307A: TERI Gamma-ray detection
  82. GRB 260225D: TERI Gamma-ray detection
  83. GRB 251118A: TERI Gamma-ray detection
  84. GRB 251113A: TERI Gamma-ray detection
  85. GRB 260428A: TERI Gamma-ray detection
  86. Konus-Wind detection of GRB 260519C
  87. GRB 260520B: Fermi GBM Final Localization
  88. GRB 260520A: Fermi GBM Final Localization
  89. GRB 260519D: Fermi GBM Final Localization Correction
  90. GRB 260519C: NuSTAR detection of prompt emission
  91. Konus-Wind detection of GRB 260518A
  92. GRB 260519B: Fermi GBM Final Localization
  93. GRB 260519A: Fermi GBM Final Localization
  94. GRB 260518A: AstroSat CZTI detection of a long burst
  95. GRB 260421B: radio detection with the VLA
  96. GRID detection of GRB 260511A
  97. GRB 260516D: GOTO optical counterpart detection
  98. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
  99. GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
  100. GRB 260516D: GROWTH-India Telescope optical detection

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