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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"

11836 results found.

  1. EP260416a: Optical follow-up observations with Kinder
  2. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  3. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  4. GRB 260417A: SVOM/GRM observation
  5. Fermi trigger No 798275385: Global MASTER-Net observations report
  6. Fermi GRB 260417B: Global MASTER-Net observations report
  7. EP260416a: Ondrejov D50 optical detection
  8. GRB 260418B: Fermi GBM Final Real-time Localization
  9. EP260417a: Global MASTER-Net observations report
  10. Fermi GRB 260417A: Global MASTER-Net observations report
  11. Konus-Wind detection of GRB 260411B
  12. GRB 260417A: AstroSat CZTI detection
  13. IPN triangulation of GRB 260411B
  14. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  15. EP260417a: Einstein Probe detection of an X-ray transient
  16. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  17. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  18. EP260416a: COLIBRÍ optical counterpart candidate
  19. EP260416a: Global MASTER-Net observations report
  20. EP260416a: Einstein Probe detection of an X-ray transient
  21. GRB 260415B: NuSTAR detection of long prompt emission
  22. Fermi trigger No 797912738: Global MASTER-Net observations report
  23. EP260321a: CMO SAI J,K observations
  24. Konus-Wind detection of GRB 260410A (short/hard)
  25. GRB 260411B: Fermi-LAT detection
  26. GRB260411B: 3.6m DOT optical observation
  27. GRB 260411B: SVOM/GRM observation of a long burst
  28. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  29. EP-WXT01709259790: Optical Upper limits with kinder observations
  30. GRB 260410A: Fermi-LAT detection
  31. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  32. EP260409a: Einstein Probe detection of an X-ray transient
  33. GRB 260402A: SVOM/ECLAIRs refined analysis
  34. EP260402a / GRB 260402A: Mephisto optical upper limits
  35. EP260405a: Einstein Probe detection of a fast X-ray transient
  36. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  37. EP260403a: COLIBRÍ optical counterpart candidate
  38. EP260403a: Einstein Probe detection of an X-ray transient
  39. GRB 260403A: AstroSat CZTI detection
  40. GRB 260402C: AstroSat CZTI detection of a long burst
  41. EP260324A / AT 2026hir: COLIBRÍ optical observations
  42. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  43. GRB 260402A: SVOM detection of a burst
  44. Fermi GRB 260401A: Global MASTER-Net observations report
  45. GRB 260401A: MAXI/GSC detection
  46. EP260329b: Mondy and Assy-Turgen optical upper limits
  47. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  48. EP260327a: Xinglong optical upper limit
  49. EP260329b: GOTO detection of optical counterpart
  50. Konus-Wind detection of GRB 260320A
  51. Konus-Wind detection of GRB 260316B
  52. GRB 260330B: SVOM detection of a burst
  53. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  54. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  55. Fermi trigger No 796485221: Global MASTER-Net observations report
  56. EP260329b: Optical follow-up with Kinder observations
  57. EP260329a: Optical upper limit with Kinder observations
  58. EP260329b: Einstein Probe detection of an X-ray transient
  59. EP-WXT trigger 01709259209: TRT optical counterpart detection
  60. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  61. GRB 260327A: AstroSat CZTI detection of a long burst
  62. EP260327a: Global MASTER-Net observations report
  63. EP260327a: Einstein Probe detection of an X-ray transient
  64. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  65. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  66. GRID detection of GRB 260320A
  67. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  68. GRB 260320A: Glowbug gamma-ray detection
  69. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  70. EP260214b: ATCA 6 GHz detection
  71. EP260321a: further Kinder optical observations
  72. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  73. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  74. EP260321a: Einstein Probe detection of an X-ray transient
  75. GRB 260310A / AT 2026fgk: KAIT optical observations
  76. GRB 260320A: NuSTAR detection of prompt emission
  77. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  78. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  79. NOEMA Detection of GRB 260310A / AT 2026fgk
  80. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  81. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  82. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  83. GRB 260317A: Fermi GBM Final Localization
  84. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  85. GRB 260316B: AstroSat CZTI detection
  86. EP260316a: optical upper limit with Kinder observations
  87. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  88. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  89. EP260314a: optical upper limit with Kinder observations
  90. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  91. EP260314a: Global MASTER-Net observations report
  92. Fermi trigger No 795185313: Global MASTER-Net observations report
  93. EP260314a: Einstein Probe detection of an X-ray transient
  94. GRB 260310A/AT2026fgk: radio detection at 15GHz
  95. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  96. Fermi GRB 260314A: Global MASTER-Net observations report
  97. Fermi GRB 260313A: Global MASTER-Net observations report
  98. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  99. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  100. GRB 260310A/AT 2026fgk: DDOTI Optical Detection

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