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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 260530A: Fermi GBM Final Real-time Localization
  2. GRB 260527A / EP260527a: VLA radio detection
  3. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  4. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  5. GRB 260529A: GOTO tentative optical afterglow candidate
  6. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  7. GRB 260527A/EP260527a: Insight-HXMT detection
  8. Fermi GRB 260529A: Global MASTER-Net observations report
  9. GRB 260529A: Fermi GBM Final Real-time Localization
  10. EP250526a: SVOM/VT optical upper limits
  11. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  12. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  13. EP260527a / GRB 260527A: NOT optical observations
  14. GRB 260527A/EP260527a: FTW optical and NIR observations
  15. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  16. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  17. EP260527a/GRB 260527A: EP-FXT follow-up observation
  18. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  19. GRB 260526A: GECAM-B observation
  20. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  21. EP260526a: EP-FXT follow-up observation
  22. EP260527a: SVOM/VT optical observation
  23. EP260527a: COLIBRÍ optical detection
  24. EP260527a: Einstein Probe detection of a fast X-ray transient
  25. The EP-WXT trigger 01709266172 is likely a flaring star
  26. The EP-WXT trigger 01709266147 is likely a flaring star
  27. Fermi trigger No 801580882: Global MASTER-Net observations report
  28. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  29. EP260526a: LCO optical upper limits
  30. EP260526a: Einstein Probe detection of a fast X-ray transient
  31. GRB 260525A: AstroSat CZTI detection
  32. EP260526.405: COLIBRÍ optical upper limits
  33. The EP-WXT trigger 01709266106 is not a real source
  34. Fermi GRB 260526A: Global MASTER-Net observations report
  35. GRB 260526A: Fermi GBM Final Real-time Localization
  36. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  37. EP-WXT 01709266106: NOT optical upper limits
  38. Fermi GRB 260525A: Global MASTER-Net observations report
  39. GRB 260525A: Fermi GBM Final Real-time Localization
  40. GRB 260523B: AstroSat CZTI detection
  41. GRB 260523B: GECAM-B observation
  42. Fermi GRB 260523A: Global MASTER-Net observations report
  43. GRB 260523B: Fermi GBM Final Real-time Localization
  44. GRB 260523A: Fermi GBM Final Real-time Localization
  45. GRB 260522A: Fermi GBM Observation
  46. GRB 260522B: NuSTAR detection of prompt emission
  47. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  48. GRB 260522B: Fermi GBM Final Real-time Localization
  49. GRB 260522A: GOTO optical upper limit
  50. Fermi trigger No 801135305: Global MASTER-Net observations report
  51. Fermi GRB 260522A: Global MASTER-Net observations report
  52. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  53. GRB 260522A: Fermi-LAT detection
  54. GRB 260519C: SVOM/GRM observation
  55. GRB 260522A: Fermi GBM Final Real-time Localization
  56. GRB 260511A: iTelescope T-75 optical detection
  57. GRB 260520B: SVOM/GRM observation
  58. GRB 260411B: TERI Gamma-ray detection
  59. GRB 260407A: TERI Gamma-ray detection
  60. GRB 260307A: TERI Gamma-ray detection
  61. GRB 260225D: TERI Gamma-ray detection
  62. GRB 251118A: TERI Gamma-ray detection
  63. GRB 251113A: TERI Gamma-ray detection
  64. GRB 260428A: TERI Gamma-ray detection
  65. Konus-Wind detection of GRB 260519C
  66. GRB 260520B: Fermi GBM Final Localization
  67. GRB 260509A: SVOM/ECLAIRs refined analysis
  68. GRB 260520A: Fermi GBM Final Localization
  69. GRB 260519D: Fermi GBM Final Localization Correction
  70. GRB 260519C: NuSTAR detection of prompt emission
  71. Konus-Wind detection of GRB 260518A
  72. GRB 260519B: Fermi GBM Final Localization
  73. GRB 260519A: Fermi GBM Final Localization
  74. GRB 260518A: AstroSat CZTI detection of a long burst
  75. GRB 260516D: SVOM/ECLAIRs refined analysis
  76. GRB 260515A: SVOM/ECLAIRs refined analysis
  77. GRB 260421B: radio detection with the VLA
  78. GRID detection of GRB 260511A
  79. GRB 260509A: CrAO ZTSh optical upper limit (Duplicate Submission)
  80. GRB 260509A: CrAO ZTSh optical upper limit
  81. GRB 260516D: EP-FXT follow-up observation
  82. GRB 260516D: GOTO optical counterpart detection
  83. GRB 260516D: LCO optical observations
  84. GRB 260515A: further Liverpool Telescope observations
  85. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
  86. GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
  87. GRB 260516D: GROWTH-India Telescope optical detection
  88. GRB 260516D: SVOM/VT optical bright candidate
  89. GRB 260516D: FRAM-ORM optical limit
  90. GRB 260515A: CrAO ZTSh BVRI optical observations
  91. Fermi GRB 260516C: Global MASTER-Net observations report
  92. SVOM GRB260516D: Global MASTER-Net observations report
  93. GRB 260516D: SVOM possible detection of a burst
  94. GRB 260516C: Fermi GBM Final Real-time Localization
  95. Konus-Wind detection of GRB 260515A
  96. GRB 260515A: Liverpool Telescope optical detection
  97. GRB 260515A: LCO optical counterpart detection
  98. Fermi Gamma-ray Burst Monitor trigger 800627191/260516518 is not a GRB
  99. GRB 260515A: SVOM/COLIBRÍ (FM-GFT) optical observations
  100. GRB 260515A: EP-FXT follow-up observation

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