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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"

11747 results found.

  1. EP-WXT trigger 01709259209: TRT optical counterpart detection
  2. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  3. GRB 260327A: AstroSat CZTI detection of a long burst
  4. EP260327a: Global MASTER-Net observations report
  5. EP260327a: Einstein Probe detection of an X-ray transient
  6. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  7. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  8. GRID detection of GRB 260320A
  9. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  10. GRB 260320A: Glowbug gamma-ray detection
  11. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  12. EP260214b: ATCA 6 GHz detection
  13. EP260321a: further Kinder optical observations
  14. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  15. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  16. EP260321a: Einstein Probe detection of an X-ray transient
  17. GRB 260310A / AT 2026fgk: KAIT optical observations
  18. GRB 260320A: NuSTAR detection of prompt emission
  19. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  20. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  21. NOEMA Detection of GRB 260310A / AT 2026fgk
  22. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  23. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  24. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  25. GRB 260317A: Fermi GBM Final Localization
  26. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  27. GRB 260316B: AstroSat CZTI detection
  28. EP260316a: optical upper limit with Kinder observations
  29. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  30. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  31. EP260314a: optical upper limit with Kinder observations
  32. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  33. EP260314a: Global MASTER-Net observations report
  34. Fermi trigger No 795185313: Global MASTER-Net observations report
  35. EP260314a: Einstein Probe detection of an X-ray transient
  36. GRB 260310A/AT2026fgk: radio detection at 15GHz
  37. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  38. Fermi GRB 260314A: Global MASTER-Net observations report
  39. Fermi GRB 260313A: Global MASTER-Net observations report
  40. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  41. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  42. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  43. GRB 260312B: AstroSat CZTI detection
  44. Fermi GRB 260311B: Global MASTER-Net observations report
  45. GRB 260310A: AstroSat CZTI detection of a long burst
  46. Fermi GRB 260310B: Global MASTER-Net observations report
  47. Fermi GRB 260310A: Global MASTER-Net observations report
  48. GRB 260308A: Fermi GBM Final Real-time Localization
  49. Fermi GRB 260307A: Global MASTER-Net observations report
  50. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  51. EP260306a: Einstein Probe detection of an X-ray transient
  52. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  53. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  54. Fermi GRB 260305A: Global MASTER-Net observations report
  55. GRB 260303B: AstroSat CZTI detection
  56. GRB 260304A: AstroSat CZTI detection of a long burst
  57. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  58. GRB 260303B: NuSTAR detection of prompt emission
  59. GRB 260228A: SVOM/ECLAIRs refined analysis
  60. GRB 260225A: SVOM/ECLAIRs refined analysis
  61. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  62. GRB 260303B: Fermi GBM Final Real-time Localization
  63. EP260302a: analysis of the follow-up EP-FXT observation
  64. EP260302a: LCO observations
  65. EP260302a: BOOTES-7 optical counterpart detection at early times
  66. GRB 260303A: SVOM detection of a burst
  67. EP260302a: Einstein Probe detection of an X-ray transient
  68. EP260227a: Mondy optical observations
  69. EP260227a: Mephisto optical detection
  70. EP260227a: SVOM/VT optical observation
  71. GRB 260228A: SVOM detection of a burst
  72. EP260227a: NOT optical observations
  73. EP260227a: Global MASTER-Net observations report
  74. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  75. Konus-Wind detection of GRB 260226A
  76. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  77. GRB 260226A: COLIBRÍ optical upper limits
  78. GRB 260226A: NuSTAR detection of bright prompt emission
  79. GRB 260226A: Fermi-LAT refined analysis
  80. The EP-WXT trigger 01709258652 is likely a flaring star
  81. LAT GRB260226.44: Global MASTER-Net observations report
  82. GRB 260226A: AstroSat CZTI detection of bright long burst
  83. GRB 260226A: Fermi-LAT detection of a bright burst
  84. EP260223a: Xinglong optical upper limit
  85. sb26021801: SVOM/C-GFT upper limit
  86. EP260223a: Einstein Probe detection of an X-ray transient
  87. EP260221a: Optical upper limit with Kinder observations
  88. Fermi GRB 260223A: Global MASTER-Net observations report
  89. EP260221a: COLIBRÍ optical counterpart candidate
  90. EP260221a: Gemini South z-band upper limit
  91. EP260221a: EP-FXT follow-up observation
  92. EP260221a: Xinglong optical upper limit
  93. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  94. EP260221a: Einstein Probe detection of an X-ray transient
  95. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  96. sb26021801: SVOM detection of a long faint X-ray transient
  97. EP260210a: Mondy optical upper limits
  98. Konus-Wind detection of GRB 260212A
  99. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  100. EP260214b: Optical upper limit with Kinder observations

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