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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"

28884 results found.

  1. GRB 260516D: VLA radio detection
  2. GRB 260601A: Fermi GBM Observation
  3. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  4. Fermi GRB 260601A: Global MASTER-Net observations report
  5. GRB 260601A: Fermi GBM Final Real-time Localization
  6. GRB 260531B: GECAM-B observation
  7. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  8. The EP-WXT trigger 01709266272 is likely a flaring star
  9. GRB 260531C: Fermi GBM Final Localization Correction
  10. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  11. Fermi trigger No 801900520: Global MASTER-Net observations report
  12. GRB 260531B: Fermi GBM Final Real-time Localization
  13. AT 2026nuz: COLIBRÍ optical observations
  14. IPN triangulation of GRB 260527A / EP260527a
  15. EP260527a/GRB 260527A: further FTW optical and NIR observations
  16. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  17. GRB 260530A: Fermi GBM Final Real-time Localization
  18. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  19. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  20. GRB 260529A: GOTO tentative optical afterglow candidate
  21. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  22. Fermi GRB 260529A: Global MASTER-Net observations report
  23. GRB 260529A: Fermi GBM Final Real-time Localization
  24. EP260526a: SVOM/VT optical upper limits
  25. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  26. EP260527a / GRB 260527A: NOT optical observations
  27. GRB 260527A/EP260527a: FTW optical and NIR observations
  28. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  29. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  30. GRB 260526A: GECAM-B observation
  31. EP260527a: SVOM/VT optical observation
  32. EP260527a: COLIBRÍ optical detection
  33. EP260527a: Einstein Probe detection of a fast X-ray transient
  34. The EP-WXT trigger 01709266172 is likely a flaring star
  35. The EP-WXT trigger 01709266147 is likely a flaring star
  36. Fermi trigger No 801580882: Global MASTER-Net observations report
  37. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  38. EP260526a: Einstein Probe detection of a fast X-ray transient
  39. GRB 260525A: AstroSat CZTI detection
  40. EP260526.405: COLIBRÍ optical upper limits
  41. The EP-WXT trigger 01709266106 is not a real source
  42. Fermi GRB 260526A: Global MASTER-Net observations report
  43. GRB 260526A: Fermi GBM Final Real-time Localization
  44. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  45. EP-WXT 01709266106: NOT optical upper limits
  46. Fermi GRB 260525A: Global MASTER-Net observations report
  47. GRB 260525A: Fermi GBM Final Real-time Localization
  48. GRB 260523B: AstroSat CZTI detection
  49. GRB 260523B: GECAM-B observation
  50. Fermi GRB 260523A: Global MASTER-Net observations report
  51. GRB 260523B: Fermi GBM Final Real-time Localization
  52. GRB 260523A: Fermi GBM Final Real-time Localization
  53. GRB 260522A: Fermi GBM Observation
  54. GRB 260522B: NuSTAR detection of prompt emission
  55. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  56. GRB 260522B: Fermi GBM Final Real-time Localization
  57. GRB 260522A: GOTO optical upper limit
  58. Fermi trigger No 801135305: Global MASTER-Net observations report
  59. Fermi GRB 260522A: Global MASTER-Net observations report
  60. GRB 260522A: Fermi-LAT detection
  61. GRB 260519C: SVOM/GRM observation
  62. GRB 260522A: Fermi GBM Final Real-time Localization
  63. GRB 260511A: iTelescope T-75 optical detection
  64. GRB 260520B: SVOM/GRM observation
  65. GRB 260411B: TERI Gamma-ray detection
  66. GRB 260407A: TERI Gamma-ray detection
  67. GRB 260307A: TERI Gamma-ray detection
  68. GRB 251118A: TERI Gamma-ray detection
  69. GRB 251113A: TERI Gamma-ray detection
  70. GRB 260428A: TERI Gamma-ray detection
  71. GRB 260520B: Fermi GBM Final Localization
  72. GRB 260520A: Fermi GBM Final Localization
  73. GRB 260519D: Fermi GBM Final Localization Correction
  74. GRB 260519B: Fermi GBM Final Localization
  75. GRB 260519A: Fermi GBM Final Localization
  76. GRB 260516D: SVOM/ECLAIRs refined analysis
  77. GRB 260515A: SVOM/ECLAIRs refined analysis
  78. GRB 260421B: radio detection with the VLA
  79. GRID detection of GRB 260511A
  80. GRB 260509A: CrAO ZTSh optical upper limit
  81. GRB 260516D: EP-FXT follow-up observation
  82. GRB 260516D: LCO optical observations
  83. GRB 260515A: further Liverpool Telescope observations
  84. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
  85. GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
  86. GRB 260516D: GROWTH-India Telescope optical detection
  87. GRB 260516D: SVOM/VT optical bright candidate
  88. GRB 260516D: FRAM-ORM optical limit
  89. GRB 260515A: CrAO ZTSh BVRI optical observations
  90. Fermi GRB 260516C: Global MASTER-Net observations report
  91. SVOM GRB260516D: Global MASTER-Net observations report
  92. GRB 260516D: SVOM possible detection of a burst
  93. GRB 260516C: Fermi GBM Final Real-time Localization
  94. GRB 260515A: LCO optical counterpart detection
  95. Fermi Gamma-ray Burst Monitor trigger 800627191/260516518 is not a GRB
  96. GRB 260515A: SVOM/COLIBRÍ (FM-GFT) optical observations
  97. GRB 260515A: EP-FXT follow-up observation
  98. EP260514a: NOT optical counterpart confirmation
  99. EP260514a: TRT optical counterpart candidate
  100. EP260514a: SVOM/VT optical candidate

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