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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"

12082 results found.

  1. Fermi trigger No 796485221: Global MASTER-Net observations report
  2. EP260329b: Optical follow-up with Kinder observations
  3. EP260329a: Optical upper limit with Kinder observations
  4. EP260329b: Einstein Probe detection of an X-ray transient
  5. EP-WXT trigger 01709259209: TRT optical counterpart detection
  6. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  7. GRB 260327A: AstroSat CZTI detection of a long burst
  8. EP260327a: Global MASTER-Net observations report
  9. EP260327a: Einstein Probe detection of an X-ray transient
  10. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  11. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  12. GRID detection of GRB 260320A
  13. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  14. GRB 260320A: Glowbug gamma-ray detection
  15. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  16. EP260214b: ATCA 6 GHz detection
  17. EP260321a: further Kinder optical observations
  18. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  19. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  20. EP260321a: Einstein Probe detection of an X-ray transient
  21. GRB 260310A / AT 2026fgk: KAIT optical observations
  22. GRB 260320A: NuSTAR detection of prompt emission
  23. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  24. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  25. NOEMA Detection of GRB 260310A / AT 2026fgk
  26. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  27. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  28. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  29. GRB 260317A: Fermi GBM Final Localization
  30. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  31. GRB 260316B: AstroSat CZTI detection
  32. EP260316a: optical upper limit with Kinder observations
  33. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  34. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  35. EP260314a: optical upper limit with Kinder observations
  36. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  37. EP260314a: Global MASTER-Net observations report
  38. Fermi trigger No 795185313: Global MASTER-Net observations report
  39. EP260314a: Einstein Probe detection of an X-ray transient
  40. GRB 260310A/AT2026fgk: radio detection at 15GHz
  41. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  42. Fermi GRB 260314A: Global MASTER-Net observations report
  43. Fermi GRB 260313A: Global MASTER-Net observations report
  44. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  45. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  46. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  47. GRB 260312B: AstroSat CZTI detection
  48. Fermi GRB 260311B: Global MASTER-Net observations report
  49. GRB 260310A: AstroSat CZTI detection of a long burst
  50. Fermi GRB 260310B: Global MASTER-Net observations report
  51. Fermi GRB 260310A: Global MASTER-Net observations report
  52. GRB 260308A: Fermi GBM Final Real-time Localization
  53. Fermi GRB 260307A: Global MASTER-Net observations report
  54. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  55. EP260306a: Einstein Probe detection of an X-ray transient
  56. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  57. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  58. Fermi GRB 260305A: Global MASTER-Net observations report
  59. GRB 260303B: AstroSat CZTI detection
  60. GRB 260304A: AstroSat CZTI detection of a long burst
  61. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  62. GRB 260303B: NuSTAR detection of prompt emission
  63. GRB 260228A: SVOM/ECLAIRs refined analysis
  64. GRB 260225A: SVOM/ECLAIRs refined analysis
  65. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  66. GRB 260303B: Fermi GBM Final Real-time Localization
  67. EP260302a: analysis of the follow-up EP-FXT observation
  68. EP260302a: LCO observations
  69. EP260302a: BOOTES-7 optical counterpart detection at early times
  70. GRB 260303A: SVOM detection of a burst
  71. EP260302a: Einstein Probe detection of an X-ray transient
  72. EP260227a: Mondy optical observations
  73. EP260227a: Mephisto optical detection
  74. EP260227a: SVOM/VT optical observation
  75. GRB 260228A: SVOM detection of a burst
  76. EP260227a: NOT optical observations
  77. EP260227a: Global MASTER-Net observations report
  78. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  79. Konus-Wind detection of GRB 260226A
  80. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  81. GRB 260226A: COLIBRÍ optical upper limits
  82. GRB 260226A: NuSTAR detection of bright prompt emission
  83. GRB 260226A: Fermi-LAT refined analysis
  84. The EP-WXT trigger 01709258652 is likely a flaring star
  85. LAT GRB260226.44: Global MASTER-Net observations report
  86. GRB 260226A: AstroSat CZTI detection of bright long burst
  87. GRB 260226A: Fermi-LAT detection of a bright burst
  88. EP260223a: Xinglong optical upper limit
  89. sb26021801: SVOM/C-GFT upper limit
  90. EP260223a: Einstein Probe detection of an X-ray transient
  91. EP260221a: Optical upper limit with Kinder observations
  92. Fermi GRB 260223A: Global MASTER-Net observations report
  93. EP260221a: COLIBRÍ optical counterpart candidate
  94. EP260221a: Gemini South z-band upper limit
  95. EP260221a: EP-FXT follow-up observation
  96. EP260221a: Xinglong optical upper limit
  97. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  98. EP260221a: Einstein Probe detection of an X-ray transient
  99. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  100. sb26021801: SVOM detection of a long faint X-ray transient

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