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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 260603A: SVOM detection of a burst
  2. EP260602b: Einstein Probe detection of a fast X-ray transient
  3. GRB 260601B/EP260601a: Insight-HXMT detection
  4. Fermi GRB 260602B: Global MASTER-Net observations report
  5. Fermi GRB 260602B: Global MASTER-Net observations report
  6. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  7. EP260602a: SVOM/VT optical candidate
  8. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  9. GRB 260602B: Fermi GBM Final Localization
  10. GRB 260601A: GECAM-B observation of a short burst
  11. GRB 260601B/EP260601a: J-band upper limit with WINTER
  12. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  13. EP260530a/AT 2026nwl: KAIT optical observations
  14. GRB 260602A: Fermi GBM Final Real-time Localization
  15. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  16. EP260602a: Optical upper limits with Kinder observations
  17. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  18. EP260602a: Einstein Probe detection of a fast X-ray transient
  19. GRB 260601B/EP260601a: SVOM/VT optical observations
  20. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  21. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  22. EP260601a: Einstein Probe detection of an X-ray transient
  23. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  24. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  25. GRB 260601A: Glowbug gamma-ray detection of a short burst
  26. GRB 260531B: Glowbug gamma-ray detection
  27. GRB 260516D: VLA radio detection
  28. GRB 260601A: Fermi GBM Observation
  29. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  30. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  31. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  32. Fermi GRB 260601A: Global MASTER-Net observations report
  33. GRB 260601A: Fermi GBM Final Real-time Localization
  34. GRB 260531B: GECAM-B observation
  35. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  36. The EP-WXT trigger 01709266272 is likely a flaring star
  37. GRB 260531C: Fermi GBM Final Localization Correction
  38. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  39. AT2026nik: EP-FXT X-ray counterpart
  40. Fermi trigger No 801900520: Global MASTER-Net observations report
  41. GRB 260531B: Fermi GBM Final Real-time Localization
  42. GRB 260531A: MAXI/GSC detection
  43. AT 2026nuz: COLIBRÍ optical observations
  44. IPN triangulation of GRB 260527A / EP260527a
  45. EP260527a/GRB 260527A: further FTW optical and NIR observations
  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. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  50. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  51. GRB 260529A: GOTO tentative optical afterglow candidate
  52. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  53. GRB 260527A/EP260527a: Insight-HXMT detection
  54. Fermi GRB 260529A: Global MASTER-Net observations report
  55. GRB 260529A: Fermi GBM Final Real-time Localization
  56. EP260526a: SVOM/VT optical upper limits
  57. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  58. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  59. EP260527a / GRB 260527A: NOT optical observations
  60. GRB 260527A/EP260527a: FTW optical and NIR observations
  61. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  62. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  63. EP260527a/GRB 260527A: EP-FXT follow-up observation
  64. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  65. GRB 260526A: GECAM-B observation
  66. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  67. EP260526a: EP-FXT follow-up observation
  68. EP260527a: SVOM/VT optical observation
  69. EP260527a: COLIBRÍ optical detection
  70. EP260527a: Einstein Probe detection of a fast X-ray transient
  71. The EP-WXT trigger 01709266172 is likely a flaring star
  72. The EP-WXT trigger 01709266147 is likely a flaring star
  73. Fermi trigger No 801580882: Global MASTER-Net observations report
  74. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  75. EP260526a: LCO optical upper limits
  76. EP260526a: Einstein Probe detection of a fast X-ray transient
  77. GRB 260525A: AstroSat CZTI detection
  78. EP260526.405: COLIBRÍ optical upper limits
  79. The EP-WXT trigger 01709266106 is not a real source
  80. Fermi GRB 260526A: Global MASTER-Net observations report
  81. GRB 260526A: Fermi GBM Final Real-time Localization
  82. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  83. EP-WXT 01709266106: NOT optical upper limits
  84. Fermi GRB 260525A: Global MASTER-Net observations report
  85. GRB 260525A: Fermi GBM Final Real-time Localization
  86. GRB 260523B: AstroSat CZTI detection
  87. GRB 260523B: GECAM-B observation
  88. Fermi GRB 260523A: Global MASTER-Net observations report
  89. GRB 260523B: Fermi GBM Final Real-time Localization
  90. GRB 260523A: Fermi GBM Final Real-time Localization
  91. GRB 260522A: Fermi GBM Observation
  92. GRB 260522B: NuSTAR detection of prompt emission
  93. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  94. GRB 260522B: Fermi GBM Final Real-time Localization
  95. GRB 260522A: GOTO optical upper limit
  96. Fermi trigger No 801135305: Global MASTER-Net observations report
  97. Fermi GRB 260522A: Global MASTER-Net observations report
  98. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  99. GRB 260522A: Fermi-LAT detection
  100. GRB 260519C: SVOM/GRM observation

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