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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 260601A: GECAM-B observation of a short burst
  2. GRB 260601B/EP260601a: J-band upper limit with WINTER
  3. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  4. EP260530a/AT 2026nwl: KAIT optical observations
  5. GRB 260602A: Fermi GBM Final Real-time Localization
  6. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  7. EP260602a: Optical upper limits with Kinder observations
  8. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  9. EP260602a: Einstein Probe detection of a fast X-ray transient
  10. GRB 260601B/EP260601a: SVOM/VT optical observations
  11. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  12. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  13. EP260601a: Einstein Probe detection of an X-ray transient
  14. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  15. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  16. GRB 260601A: Glowbug gamma-ray detection of a short burst
  17. GRB 260531B: Glowbug gamma-ray detection
  18. GRB 260516D: VLA radio detection
  19. GRB 260601A: Fermi GBM Observation
  20. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  21. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  22. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  23. Fermi GRB 260601A: Global MASTER-Net observations report
  24. GRB 260601A: Fermi GBM Final Real-time Localization
  25. GRB 260531B: GECAM-B observation
  26. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  27. The EP-WXT trigger 01709266272 is likely a flaring star
  28. GRB 260531C: Fermi GBM Final Localization Correction
  29. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  30. AT2026nik: EP-FXT X-ray counterpart
  31. Fermi trigger No 801900520: Global MASTER-Net observations report
  32. GRB 260531B: Fermi GBM Final Real-time Localization
  33. GRB 260531A: MAXI/GSC detection
  34. AT 2026nuz: COLIBRÍ optical observations
  35. IPN triangulation of GRB 260527A / EP260527a
  36. EP260527a/GRB 260527A: further FTW optical and NIR observations
  37. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  38. GRB 260530A: Fermi GBM Final Real-time Localization
  39. GRB 260527A / EP260527a: VLA radio detection
  40. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  41. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  42. GRB 260529A: GOTO tentative optical afterglow candidate
  43. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  44. GRB 260527A/EP260527a: Insight-HXMT detection
  45. Fermi GRB 260529A: Global MASTER-Net observations report
  46. GRB 260529A: Fermi GBM Final Real-time Localization
  47. EP260526a: SVOM/VT optical upper limits
  48. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  49. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  50. EP260527a / GRB 260527A: NOT optical observations
  51. GRB 260527A/EP260527a: FTW optical and NIR observations
  52. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  53. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  54. EP260527a/GRB 260527A: EP-FXT follow-up observation
  55. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  56. GRB 260526A: GECAM-B observation
  57. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  58. EP260526a: EP-FXT follow-up observation
  59. EP260527a: SVOM/VT optical observation
  60. EP260527a: COLIBRÍ optical detection
  61. EP260527a: Einstein Probe detection of a fast X-ray transient
  62. The EP-WXT trigger 01709266172 is likely a flaring star
  63. The EP-WXT trigger 01709266147 is likely a flaring star
  64. Fermi trigger No 801580882: Global MASTER-Net observations report
  65. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  66. EP260526a: LCO optical upper limits
  67. EP260526a: Einstein Probe detection of a fast X-ray transient
  68. GRB 260525A: AstroSat CZTI detection
  69. EP260526.405: COLIBRÍ optical upper limits
  70. The EP-WXT trigger 01709266106 is not a real source
  71. Fermi GRB 260526A: Global MASTER-Net observations report
  72. GRB 260526A: Fermi GBM Final Real-time Localization
  73. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  74. EP-WXT 01709266106: NOT optical upper limits
  75. Fermi GRB 260525A: Global MASTER-Net observations report
  76. GRB 260525A: Fermi GBM Final Real-time Localization
  77. GRB 260523B: AstroSat CZTI detection
  78. GRB 260523B: GECAM-B observation
  79. Fermi GRB 260523A: Global MASTER-Net observations report
  80. GRB 260523B: Fermi GBM Final Real-time Localization
  81. GRB 260523A: Fermi GBM Final Real-time Localization
  82. GRB 260522A: Fermi GBM Observation
  83. GRB 260522B: NuSTAR detection of prompt emission
  84. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  85. GRB 260522B: Fermi GBM Final Real-time Localization
  86. GRB 260522A: GOTO optical upper limit
  87. Fermi trigger No 801135305: Global MASTER-Net observations report
  88. Fermi GRB 260522A: Global MASTER-Net observations report
  89. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  90. GRB 260522A: Fermi-LAT detection
  91. GRB 260519C: SVOM/GRM observation
  92. GRB 260522A: Fermi GBM Final Real-time Localization
  93. GRB 260511A: iTelescope T-75 optical detection
  94. GRB 260520B: SVOM/GRM observation
  95. GRB 260411B: TERI Gamma-ray detection
  96. GRB 260407A: TERI Gamma-ray detection
  97. GRB 260307A: TERI Gamma-ray detection
  98. GRB 260225D: TERI Gamma-ray detection
  99. GRB 251118A: TERI Gamma-ray detection
  100. GRB 251113A: TERI Gamma-ray detection

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