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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. EP260602a: SVOM/VT optical magnitudes correction
  2. GRB 260601A: SVOM/GRM observation of a short burst
  3. EP260602c: Einstein Probe detection of a fast X-ray transient
  4. GRB 260603A : SVOM/COLIBRÍ optical counterpart candidate
  5. EP260602a: COLIBRÍ optical observations
  6. GRB260601B/EP260601a: NOT near-infrared observations
  7. SVOM GRB260603.23: Global MASTER-Net observations report
  8. GRB 260603A: SVOM detection of a burst
  9. EP260602b: Einstein Probe detection of a fast X-ray transient
  10. GRB 260601B/EP260601a: Insight-HXMT detection
  11. Fermi GRB 260602B: Global MASTER-Net observations report
  12. Fermi GRB 260602B: Global MASTER-Net observations report
  13. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  14. EP260602a: SVOM/VT optical candidate
  15. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  16. GRB 260602B: Fermi GBM Final Localization
  17. GRB 260601A: GECAM-B observation of a short burst
  18. GRB 260601B/EP260601a: J-band upper limit with WINTER
  19. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  20. EP260530a/AT 2026nwl: KAIT optical observations
  21. GRB 260602A: Fermi GBM Final Real-time Localization
  22. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  23. EP260602a: Optical upper limits with Kinder observations
  24. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  25. EP260602a: Einstein Probe detection of a fast X-ray transient
  26. GRB 260601B/EP260601a: SVOM/VT optical observations
  27. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  28. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  29. EP260601a: Einstein Probe detection of an X-ray transient
  30. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  31. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  32. GRB 260601A: Glowbug gamma-ray detection of a short burst
  33. GRB 260531B: Glowbug gamma-ray detection
  34. GRB 260516D: VLA radio detection
  35. GRB 260601A: Fermi GBM Observation
  36. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  37. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  38. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  39. Fermi GRB 260601A: Global MASTER-Net observations report
  40. GRB 260601A: Fermi GBM Final Real-time Localization
  41. GRB 260531B: GECAM-B observation
  42. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  43. The EP-WXT trigger 01709266272 is likely a flaring star
  44. GRB 260531C: Fermi GBM Final Localization Correction
  45. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  46. AT2026nik: EP-FXT X-ray counterpart
  47. Fermi trigger No 801900520: Global MASTER-Net observations report
  48. GRB 260531B: Fermi GBM Final Real-time Localization
  49. GRB 260531A: MAXI/GSC detection
  50. AT 2026nuz: COLIBRÍ optical observations
  51. IPN triangulation of GRB 260527A / EP260527a
  52. EP260527a/GRB 260527A: further FTW optical and NIR observations
  53. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  54. GRB 260530A: Fermi GBM Final Real-time Localization
  55. GRB 260527A / EP260527a: VLA radio detection
  56. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  57. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  58. GRB 260529A: GOTO tentative optical afterglow candidate
  59. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  60. GRB 260527A/EP260527a: Insight-HXMT detection
  61. Fermi GRB 260529A: Global MASTER-Net observations report
  62. GRB 260529A: Fermi GBM Final Real-time Localization
  63. EP260526a: SVOM/VT optical upper limits
  64. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  65. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  66. EP260527a / GRB 260527A: NOT optical observations
  67. GRB 260527A/EP260527a: FTW optical and NIR observations
  68. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  69. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  70. EP260527a/GRB 260527A: EP-FXT follow-up observation
  71. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  72. GRB 260526A: GECAM-B observation
  73. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  74. EP260526a: EP-FXT follow-up observation
  75. EP260527a: SVOM/VT optical observation
  76. EP260527a: COLIBRÍ optical detection
  77. EP260527a: Einstein Probe detection of a fast X-ray transient
  78. The EP-WXT trigger 01709266172 is likely a flaring star
  79. The EP-WXT trigger 01709266147 is likely a flaring star
  80. Fermi trigger No 801580882: Global MASTER-Net observations report
  81. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  82. EP260526a: LCO optical upper limits
  83. EP260526a: Einstein Probe detection of a fast X-ray transient
  84. GRB 260525A: AstroSat CZTI detection
  85. EP260526.405: COLIBRÍ optical upper limits
  86. The EP-WXT trigger 01709266106 is not a real source
  87. Fermi GRB 260526A: Global MASTER-Net observations report
  88. GRB 260526A: Fermi GBM Final Real-time Localization
  89. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  90. EP-WXT 01709266106: NOT optical upper limits
  91. Fermi GRB 260525A: Global MASTER-Net observations report
  92. GRB 260525A: Fermi GBM Final Real-time Localization
  93. GRB 260523B: AstroSat CZTI detection
  94. GRB 260523B: GECAM-B observation
  95. Fermi GRB 260523A: Global MASTER-Net observations report
  96. GRB 260523B: Fermi GBM Final Real-time Localization
  97. GRB 260523A: Fermi GBM Final Real-time Localization
  98. GRB 260522A: Fermi GBM Observation
  99. GRB 260522B: NuSTAR detection of prompt emission
  100. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28

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