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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. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  2. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  3. GRB 260529A: GOTO tentative optical afterglow candidate
  4. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  5. GRB 260527A/EP260527a: Insight-HXMT detection
  6. Fermi GRB 260529A: Global MASTER-Net observations report
  7. GRB 260529A: Fermi GBM Final Real-time Localization
  8. EP250526a: SVOM/VT optical upper limits
  9. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  10. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  11. EP260527a / GRB 260527A: NOT optical observations
  12. GRB 260527A/EP260527a: FTW optical and NIR observations
  13. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  14. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  15. EP260527a/GRB 260527A: EP-FXT follow-up observation
  16. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  17. GRB 260526A: GECAM-B observation
  18. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  19. EP260526a: EP-FXT follow-up observation
  20. EP260527a: SVOM/VT optical observation
  21. EP260527a: COLIBRÍ optical detection
  22. EP260527a: Einstein Probe detection of a fast X-ray transient
  23. The EP-WXT trigger 01709266172 is likely a flaring star
  24. The EP-WXT trigger 01709266147 is likely a flaring star
  25. Fermi trigger No 801580882: Global MASTER-Net observations report
  26. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  27. EP260526a: LCO optical upper limits
  28. EP260526a: Einstein Probe detection of a fast X-ray transient
  29. GRB 260525A: AstroSat CZTI detection
  30. EP260526.405: COLIBRÍ optical upper limits
  31. The EP-WXT trigger 01709266106 is not a real source
  32. Fermi GRB 260526A: Global MASTER-Net observations report
  33. GRB 260526A: Fermi GBM Final Real-time Localization
  34. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  35. EP-WXT 01709266106: NOT optical upper limits
  36. Fermi GRB 260525A: Global MASTER-Net observations report
  37. GRB 260525A: Fermi GBM Final Real-time Localization
  38. GRB 260523B: AstroSat CZTI detection
  39. GRB 260523B: GECAM-B observation
  40. Fermi GRB 260523A: Global MASTER-Net observations report
  41. GRB 260523B: Fermi GBM Final Real-time Localization
  42. GRB 260523A: Fermi GBM Final Real-time Localization
  43. GRB 260522A: Fermi GBM Observation
  44. GRB 260522B: NuSTAR detection of prompt emission
  45. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  46. GRB 260522B: Fermi GBM Final Real-time Localization
  47. GRB 260522A: GOTO optical upper limit
  48. Fermi trigger No 801135305: Global MASTER-Net observations report
  49. Fermi GRB 260522A: Global MASTER-Net observations report
  50. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  51. GRB 260522A: Fermi-LAT detection
  52. GRB 260519C: SVOM/GRM observation
  53. GRB 260522A: Fermi GBM Final Real-time Localization
  54. GRB 260511A: iTelescope T-75 optical detection
  55. GRB 260520B: SVOM/GRM observation
  56. GRB 260411B: TERI Gamma-ray detection
  57. GRB 260407A: TERI Gamma-ray detection
  58. GRB 260307A: TERI Gamma-ray detection
  59. GRB 260225D: TERI Gamma-ray detection
  60. GRB 251118A: TERI Gamma-ray detection
  61. GRB 251113A: TERI Gamma-ray detection
  62. GRB 260428A: TERI Gamma-ray detection
  63. Konus-Wind detection of GRB 260519C
  64. GRB 260520B: Fermi GBM Final Localization
  65. GRB 260509A: SVOM/ECLAIRs refined analysis
  66. GRB 260520A: Fermi GBM Final Localization
  67. GRB 260519D: Fermi GBM Final Localization Correction
  68. GRB 260519C: NuSTAR detection of prompt emission
  69. Konus-Wind detection of GRB 260518A
  70. GRB 260519B: Fermi GBM Final Localization
  71. GRB 260519A: Fermi GBM Final Localization
  72. GRB 260518A: AstroSat CZTI detection of a long burst
  73. GRB 260516D: SVOM/ECLAIRs refined analysis
  74. GRB 260515A: SVOM/ECLAIRs refined analysis
  75. GRB 260421B: radio detection with the VLA
  76. GRID detection of GRB 260511A
  77. GRB 260509A: CrAO ZTSh optical upper limit (Duplicate Submission)
  78. GRB 260509A: CrAO ZTSh optical upper limit
  79. GRB 260516D: EP-FXT follow-up observation
  80. GRB 260516D: GOTO optical counterpart detection
  81. GRB 260516D: LCO optical observations
  82. GRB 260515A: further Liverpool Telescope observations
  83. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
  84. GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
  85. GRB 260516D: GROWTH-India Telescope optical detection
  86. GRB 260516D: SVOM/VT optical bright candidate
  87. GRB 260516D: FRAM-ORM optical limit
  88. GRB 260515A: CrAO ZTSh BVRI optical observations
  89. Fermi GRB 260516C: Global MASTER-Net observations report
  90. SVOM GRB260516D: Global MASTER-Net observations report
  91. GRB 260516D: SVOM possible detection of a burst
  92. GRB 260516C: Fermi GBM Final Real-time Localization
  93. Konus-Wind detection of GRB 260515A
  94. GRB 260515A: Liverpool Telescope optical detection
  95. GRB 260515A: LCO optical counterpart detection
  96. Fermi Gamma-ray Burst Monitor trigger 800627191/260516518 is not a GRB
  97. GRB 260515A: SVOM/COLIBRÍ (FM-GFT) optical observations
  98. GRB 260515A: EP-FXT follow-up observation
  99. EP260514a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  100. EP260514a: NOT optical counterpart confirmation

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