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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"
  1. GRB 260601B/EP260601a: SVOM/VT optical observations
  2. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  3. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  4. EP260601a: Einstein Probe detection of an X-ray transient
  5. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  6. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  7. GRB 260601A: Glowbug gamma-ray detection of a short burst
  8. GRB 260531B: Glowbug gamma-ray detection
  9. GRB 260516D: VLA radio detection
  10. GRB 260601A: Fermi GBM Observation
  11. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  12. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  13. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  14. Fermi GRB 260601A: Global MASTER-Net observations report
  15. GRB 260601A: Fermi GBM Final Real-time Localization
  16. GRB 260531B: GECAM-B observation
  17. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  18. The EP-WXT trigger 01709266272 is likely a flaring star
  19. GRB 260531C: Fermi GBM Final Localization Correction
  20. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  21. AT2026nik: EP-FXT X-ray counterpart
  22. Fermi trigger No 801900520: Global MASTER-Net observations report
  23. GRB 260531B: Fermi GBM Final Real-time Localization
  24. GRB 260531A: MAXI/GSC detection
  25. AT 2026nuz: COLIBRÍ optical observations
  26. IPN triangulation of GRB 260527A / EP260527a
  27. EP260527a/GRB 260527A: further FTW optical and NIR observations
  28. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  29. GRB 260530A: Fermi GBM Final Real-time Localization
  30. GRB 260527A / EP260527a: VLA radio detection
  31. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  32. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  33. GRB 260529A: GOTO tentative optical afterglow candidate
  34. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  35. GRB 260527A/EP260527a: Insight-HXMT detection
  36. Fermi GRB 260529A: Global MASTER-Net observations report
  37. GRB 260529A: Fermi GBM Final Real-time Localization
  38. EP260526a: SVOM/VT optical upper limits
  39. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  40. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  41. EP260527a / GRB 260527A: NOT optical observations
  42. GRB 260527A/EP260527a: FTW optical and NIR observations
  43. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  44. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  45. EP260527a/GRB 260527A: EP-FXT follow-up observation
  46. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  47. GRB 260526A: GECAM-B observation
  48. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  49. EP260526a: EP-FXT follow-up observation
  50. EP260527a: SVOM/VT optical observation
  51. EP260527a: COLIBRÍ optical detection
  52. EP260527a: Einstein Probe detection of a fast X-ray transient
  53. The EP-WXT trigger 01709266172 is likely a flaring star
  54. The EP-WXT trigger 01709266147 is likely a flaring star
  55. Fermi trigger No 801580882: Global MASTER-Net observations report
  56. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  57. EP260526a: LCO optical upper limits
  58. EP260526a: Einstein Probe detection of a fast X-ray transient
  59. GRB 260525A: AstroSat CZTI detection
  60. EP260526.405: COLIBRÍ optical upper limits
  61. The EP-WXT trigger 01709266106 is not a real source
  62. Fermi GRB 260526A: Global MASTER-Net observations report
  63. GRB 260526A: Fermi GBM Final Real-time Localization
  64. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  65. EP-WXT 01709266106: NOT optical upper limits
  66. Fermi GRB 260525A: Global MASTER-Net observations report
  67. GRB 260525A: Fermi GBM Final Real-time Localization
  68. GRB 260523B: AstroSat CZTI detection
  69. GRB 260523B: GECAM-B observation
  70. Fermi GRB 260523A: Global MASTER-Net observations report
  71. GRB 260523B: Fermi GBM Final Real-time Localization
  72. GRB 260523A: Fermi GBM Final Real-time Localization
  73. GRB 260522A: Fermi GBM Observation
  74. GRB 260522B: NuSTAR detection of prompt emission
  75. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  76. GRB 260522B: Fermi GBM Final Real-time Localization
  77. GRB 260522A: GOTO optical upper limit
  78. Fermi trigger No 801135305: Global MASTER-Net observations report
  79. Fermi GRB 260522A: Global MASTER-Net observations report
  80. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  81. GRB 260522A: Fermi-LAT detection
  82. GRB 260519C: SVOM/GRM observation
  83. GRB 260522A: Fermi GBM Final Real-time Localization
  84. GRB 260511A: iTelescope T-75 optical detection
  85. GRB 260520B: SVOM/GRM observation
  86. GRB 260411B: TERI Gamma-ray detection
  87. GRB 260407A: TERI Gamma-ray detection
  88. GRB 260307A: TERI Gamma-ray detection
  89. GRB 260225D: TERI Gamma-ray detection
  90. GRB 251118A: TERI Gamma-ray detection
  91. GRB 251113A: TERI Gamma-ray detection
  92. GRB 260428A: TERI Gamma-ray detection
  93. Konus-Wind detection of GRB 260519C
  94. GRB 260520B: Fermi GBM Final Localization
  95. GRB 260509A: SVOM/ECLAIRs refined analysis
  96. GRB 260520A: Fermi GBM Final Localization
  97. GRB 260519D: Fermi GBM Final Localization Correction
  98. GRB 260519C: NuSTAR detection of prompt emission
  99. Konus-Wind detection of GRB 260518A
  100. GRB 260519B: Fermi GBM Final Localization

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