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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"
  1. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  2. EP260602a: SVOM/VT optical candidate
  3. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  4. GRB 260602B: Fermi GBM Final Localization
  5. GRB 260601A: GECAM-B observation of a short burst
  6. GRB 260601B/EP260601a: J-band upper limit with WINTER
  7. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  8. EP260530a/AT 2026nwl: KAIT optical observations
  9. GRB 260602A: Fermi GBM Final Real-time Localization
  10. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  11. EP260602a: Optical upper limits with Kinder observations
  12. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  13. EP260602a: Einstein Probe detection of a fast X-ray transient
  14. GRB 260601B/EP260601a: SVOM/VT optical observations
  15. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  16. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  17. EP260601a: Einstein Probe detection of an X-ray transient
  18. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  19. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  20. GRB 260601A: Glowbug gamma-ray detection of a short burst
  21. GRB 260531B: Glowbug gamma-ray detection
  22. GRB 260516D: VLA radio detection
  23. GRB 260601A: Fermi GBM Observation
  24. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  25. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  26. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  27. Fermi GRB 260601A: Global MASTER-Net observations report
  28. GRB 260601A: Fermi GBM Final Real-time Localization
  29. GRB 260531B: GECAM-B observation
  30. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  31. The EP-WXT trigger 01709266272 is likely a flaring star
  32. GRB 260531C: Fermi GBM Final Localization Correction
  33. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  34. AT2026nik: EP-FXT X-ray counterpart
  35. Fermi trigger No 801900520: Global MASTER-Net observations report
  36. GRB 260531B: Fermi GBM Final Real-time Localization
  37. GRB 260531A: MAXI/GSC detection
  38. AT 2026nuz: COLIBRÍ optical observations
  39. IPN triangulation of GRB 260527A / EP260527a
  40. EP260527a/GRB 260527A: further FTW optical and NIR observations
  41. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  42. GRB 260530A: Fermi GBM Final Real-time Localization
  43. GRB 260527A / EP260527a: VLA radio detection
  44. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  45. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  46. GRB 260529A: GOTO tentative optical afterglow candidate
  47. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  48. GRB 260527A/EP260527a: Insight-HXMT detection
  49. Fermi GRB 260529A: Global MASTER-Net observations report
  50. GRB 260529A: Fermi GBM Final Real-time Localization
  51. EP260526a: SVOM/VT optical upper limits
  52. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  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. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  57. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  58. EP260527a/GRB 260527A: EP-FXT follow-up observation
  59. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  60. GRB 260526A: GECAM-B observation
  61. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  62. EP260526a: EP-FXT follow-up observation
  63. EP260527a: SVOM/VT optical observation
  64. EP260527a: COLIBRÍ optical detection
  65. EP260527a: Einstein Probe detection of a fast X-ray transient
  66. The EP-WXT trigger 01709266172 is likely a flaring star
  67. The EP-WXT trigger 01709266147 is likely a flaring star
  68. Fermi trigger No 801580882: Global MASTER-Net observations report
  69. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  70. EP260526a: LCO optical upper limits
  71. EP260526a: Einstein Probe detection of a fast X-ray transient
  72. GRB 260525A: AstroSat CZTI detection
  73. EP260526.405: COLIBRÍ optical upper limits
  74. The EP-WXT trigger 01709266106 is not a real source
  75. Fermi GRB 260526A: Global MASTER-Net observations report
  76. GRB 260526A: Fermi GBM Final Real-time Localization
  77. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  78. EP-WXT 01709266106: NOT optical upper limits
  79. Fermi GRB 260525A: Global MASTER-Net observations report
  80. GRB 260525A: Fermi GBM Final Real-time Localization
  81. GRB 260523B: AstroSat CZTI detection
  82. GRB 260523B: GECAM-B observation
  83. Fermi GRB 260523A: Global MASTER-Net observations report
  84. GRB 260523B: Fermi GBM Final Real-time Localization
  85. GRB 260523A: Fermi GBM Final Real-time Localization
  86. GRB 260522A: Fermi GBM Observation
  87. GRB 260522B: NuSTAR detection of prompt emission
  88. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  89. GRB 260522B: Fermi GBM Final Real-time Localization
  90. GRB 260522A: GOTO optical upper limit
  91. Fermi trigger No 801135305: Global MASTER-Net observations report
  92. Fermi GRB 260522A: Global MASTER-Net observations report
  93. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  94. GRB 260522A: Fermi-LAT detection
  95. GRB 260519C: SVOM/GRM observation
  96. GRB 260522A: Fermi GBM Final Real-time Localization
  97. GRB 260511A: iTelescope T-75 optical detection
  98. GRB 260520B: SVOM/GRM observation
  99. GRB 260411B: TERI Gamma-ray detection
  100. GRB 260407A: TERI Gamma-ray detection

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