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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"

12084 results found.

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

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