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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"

11468 results found.

  1. EP260403a: Einstein Probe detection of an X-ray transient
  2. GRB 260403A: AstroSat CZTI detection
  3. GRB 260402C: AstroSat CZTI detection of a long burst
  4. EP260324A / AT 2026hir: COLIBRÍ optical observations
  5. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  6. GRB 260402A: SVOM detection of a burst
  7. Fermi GRB 260401A: Global MASTER-Net observations report
  8. GRB 260401A: MAXI/GSC detection
  9. EP260329b: Mondy and Assy-Turgen optical upper limits
  10. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  11. EP260327a: Xinglong optical upper limit
  12. EP260329b: GOTO detection of optical counterpart
  13. Konus-Wind detection of GRB 260320A
  14. Konus-Wind detection of GRB 260316B
  15. GRB 260330B: SVOM detection of a burst
  16. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  17. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  18. Fermi trigger No 796485221: Global MASTER-Net observations report
  19. EP260329b: Optical follow-up with Kinder observations
  20. EP260329a: Optical upper limit with Kinder observations
  21. EP260329b: Einstein Probe detection of an X-ray transient
  22. EP-WXT trigger 01709259209: TRT optical counterpart detection
  23. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  24. GRB 260327A: AstroSat CZTI detection of a long burst
  25. EP260327a: Global MASTER-Net observations report
  26. EP260327a: Einstein Probe detection of an X-ray transient
  27. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  28. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  29. GRID detection of GRB 260320A
  30. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  31. GRB 260320A: Glowbug gamma-ray detection
  32. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  33. EP260214b: ATCA 6 GHz detection
  34. EP260321a: further Kinder optical observations
  35. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  36. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  37. EP260321a: Einstein Probe detection of an X-ray transient
  38. GRB 260310A / AT 2026fgk: KAIT optical observations
  39. GRB 260320A: NuSTAR detection of prompt emission
  40. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  41. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  42. NOEMA Detection of GRB 260310A / AT 2026fgk
  43. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  44. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  45. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  46. GRB 260317A: Fermi GBM Final Localization
  47. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  48. GRB 260316B: AstroSat CZTI detection
  49. EP260316a: optical upper limit with Kinder observations
  50. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  51. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  52. EP260314a: optical upper limit with Kinder observations
  53. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  54. EP260314a: Global MASTER-Net observations report
  55. Fermi trigger No 795185313: Global MASTER-Net observations report
  56. EP260314a: Einstein Probe detection of an X-ray transient
  57. GRB 260310A/AT2026fgk: radio detection at 15GHz
  58. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  59. Fermi GRB 260314A: Global MASTER-Net observations report
  60. Fermi GRB 260313A: Global MASTER-Net observations report
  61. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  62. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  63. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  64. GRB 260312B: AstroSat CZTI detection
  65. Fermi GRB 260311B: Global MASTER-Net observations report
  66. GRB 260310A: AstroSat CZTI detection of a long burst
  67. Fermi GRB 260310B: Global MASTER-Net observations report
  68. Fermi GRB 260310A: Global MASTER-Net observations report
  69. GRB 260308A: Fermi GBM Final Real-time Localization
  70. Fermi GRB 260307A: Global MASTER-Net observations report
  71. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  72. EP260306a: Einstein Probe detection of an X-ray transient
  73. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  74. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  75. Fermi GRB 260305A: Global MASTER-Net observations report
  76. GRB 260303B: AstroSat CZTI detection
  77. GRB 260304A: AstroSat CZTI detection of a long burst
  78. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  79. GRB 260303B: NuSTAR detection of prompt emission
  80. GRB 260228A: SVOM/ECLAIRs refined analysis
  81. GRB 260225A: SVOM/ECLAIRs refined analysis
  82. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  83. GRB 260303B: Fermi GBM Final Real-time Localization
  84. EP260302a: analysis of the follow-up EP-FXT observation
  85. EP260302a: LCO observations
  86. EP260302a: BOOTES-7 optical counterpart detection at early times
  87. GRB 260303A: SVOM detection of a burst
  88. EP260302a: Einstein Probe detection of an X-ray transient
  89. EP260227a: Mondy optical observations
  90. EP260227a: Mephisto optical detection
  91. EP260227a: SVOM/VT optical observation
  92. GRB 260228A: SVOM detection of a burst
  93. EP260227a: NOT optical observations
  94. EP260227a: Global MASTER-Net observations report
  95. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  96. Konus-Wind detection of GRB 260226A
  97. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  98. GRB 260226A: COLIBRÍ optical upper limits
  99. GRB 260226A: NuSTAR detection of bright prompt emission
  100. GRB 260226A: Fermi-LAT refined analysis

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