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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"

45457 results found.

  1. EP260602a: COLIBRÍ optical observations
  2. GRB260601B/EP260601a: NOT near-infrared observations
  3. SVOM GRB260603.23: Global MASTER-Net observations report
  4. GRB 260603A: SVOM detection of a burst
  5. EP260602b: Einstein Probe detection of a fast X-ray transient
  6. GRB 260601B/EP260601a: Insight-HXMT detection
  7. Fermi GRB 260602B: Global MASTER-Net observations report
  8. Fermi GRB 260602B: Global MASTER-Net observations report
  9. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  10. EP260602a: SVOM/VT optical candidate
  11. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  12. GRB 260602B: Fermi GBM Final Localization
  13. GRB 260601A: GECAM-B observation of a short burst
  14. GRB 260601B/EP260601a: J-band upper limit with WINTER
  15. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  16. EP260530a/AT 2026nwl: KAIT optical observations
  17. GRB 260602A: Fermi GBM Final Real-time Localization
  18. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  19. EP260602a: Optical upper limits with Kinder observations
  20. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  21. EP260602a: Einstein Probe detection of a fast X-ray transient
  22. GRB 260601B/EP260601a: SVOM/VT optical observations
  23. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  24. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  25. EP260601a: Einstein Probe detection of an X-ray transient
  26. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  27. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  28. GRB 260601A: Glowbug gamma-ray detection of a short burst
  29. GRB 260531B: Glowbug gamma-ray detection
  30. GRB 260516D: VLA radio detection
  31. GRB 260601A: Fermi GBM Observation
  32. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  33. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  34. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  35. Fermi GRB 260601A: Global MASTER-Net observations report
  36. GRB 260601A: Fermi GBM Final Real-time Localization
  37. GRB 260531B: GECAM-B observation
  38. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  39. The EP-WXT trigger 01709266272 is likely a flaring star
  40. GRB 260531C: Fermi GBM Final Localization Correction
  41. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  42. AT2026nik: EP-FXT X-ray counterpart
  43. Fermi trigger No 801900520: Global MASTER-Net observations report
  44. GRB 260531B: Fermi GBM Final Real-time Localization
  45. GRB 260531A: MAXI/GSC detection
  46. AT 2026nuz: COLIBRÍ optical observations
  47. IPN triangulation of GRB 260527A / EP260527a
  48. EP260527a/GRB 260527A: further FTW optical and NIR observations
  49. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  50. GRB 260530A: Fermi GBM Final Real-time Localization
  51. GRB 260527A / EP260527a: VLA radio detection
  52. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  53. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  54. GRB 260529A: GOTO tentative optical afterglow candidate
  55. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  56. GRB 260527A/EP260527a: Insight-HXMT detection
  57. Fermi GRB 260529A: Global MASTER-Net observations report
  58. GRB 260529A: Fermi GBM Final Real-time Localization
  59. EP260526a: SVOM/VT optical upper limits
  60. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  61. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  62. EP260527a / GRB 260527A: NOT optical observations
  63. GRB 260527A/EP260527a: FTW optical and NIR observations
  64. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  65. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  66. EP260527a/GRB 260527A: EP-FXT follow-up observation
  67. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  68. GRB 260526A: GECAM-B observation
  69. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  70. EP260526a: EP-FXT follow-up observation
  71. EP260527a: SVOM/VT optical observation
  72. EP260527a: COLIBRÍ optical detection
  73. EP260527a: Einstein Probe detection of a fast X-ray transient
  74. The EP-WXT trigger 01709266172 is likely a flaring star
  75. The EP-WXT trigger 01709266147 is likely a flaring star
  76. Fermi trigger No 801580882: Global MASTER-Net observations report
  77. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  78. EP260526a: LCO optical upper limits
  79. EP260526a: Einstein Probe detection of a fast X-ray transient
  80. GRB 260525A: AstroSat CZTI detection
  81. EP260526.405: COLIBRÍ optical upper limits
  82. The EP-WXT trigger 01709266106 is not a real source
  83. Fermi GRB 260526A: Global MASTER-Net observations report
  84. GRB 260526A: Fermi GBM Final Real-time Localization
  85. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  86. EP-WXT 01709266106: NOT optical upper limits
  87. Fermi GRB 260525A: Global MASTER-Net observations report
  88. GRB 260525A: Fermi GBM Final Real-time Localization
  89. GRB 260523B: AstroSat CZTI detection
  90. GRB 260523B: GECAM-B observation
  91. Fermi GRB 260523A: Global MASTER-Net observations report
  92. GRB 260523B: Fermi GBM Final Real-time Localization
  93. GRB 260523A: Fermi GBM Final Real-time Localization
  94. GRB 260522A: Fermi GBM Observation
  95. GRB 260522B: NuSTAR detection of prompt emission
  96. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  97. GRB 260522B: Fermi GBM Final Real-time Localization
  98. GRB 260522A: GOTO optical upper limit
  99. Fermi trigger No 801135305: Global MASTER-Net observations report
  100. Fermi GRB 260522A: Global MASTER-Net observations report

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