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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"

27475 results found.

  1. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  2. GRB 260310A/AT2026fgk: LBT near-infrared observations
  3. NOEMA Detection of GRB 260310A / AT 2026fgk
  4. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  5. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  6. GRB 260318A: Fermi GBM Final Real-time Localization
  7. GRB 260310A / AT 2026fgk: radio detection with the VLA
  8. GRB 260317A: Fermi GBM Final Localization
  9. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  10. GRB 260316B: AstroSat CZTI detection
  11. EP260316a: Xinglong optical upper limit
  12. GRB 260316B: Fermi GBM Final Real-time Localization
  13. EP260316a: optical upper limit with Kinder observations
  14. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  15. GRB 260314A: Glowbug gamma-ray detection
  16. EP260314a: Xinglong optical upper limit
  17. EP260314a: optical upper limit with Kinder observations
  18. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  19. GRB 260310A / AT 2026fgk: iTelescope optical observations
  20. GRID detection of GRB 260312B
  21. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  22. EP260314a: BOOTES-6/DPR optical upper limits at early times
  23. EP260314a: Einstein Probe detection of an X-ray transient
  24. GRB 260310A/AT2026fgk: radio detection at 15GHz
  25. GRB 260310A / AT2026fgk: TNG NIR detection
  26. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  27. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  28. GRB 260314A: Fermi GBM Final Real-time Localization
  29. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  30. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  31. GRB 260310B: Insight-HXMT/HE detection
  32. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  33. GRB 260312B: AstroSat CZTI detection
  34. Swift BAT trigger 1500295: A solar flare
  35. GRB 260313A: Fermi GBM Final Real-time Localization
  36. Swift BAT trigger 1500287: A solar flare
  37. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  38. GRB 260308A: Insight-HXMT/HE detection
  39. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  40. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  41. GRB260310A / AT2026fgk: P200 Spectroscopy
  42. GRB 260312B: Glowbug gamma-ray detection
  43. GRB 260310A: potential optical counterpart
  44. Swift BAT trigger 1500148: A solar flare
  45. GRB 260312B: Fermi GBM Final Real-time Localization
  46. GRB 260312A: Swift detection of a burst
  47. GRB 260311B: Fermi GBM Final Real-time Localization
  48. GRB 260131A/B: radio detection with the VLA
  49. GRB 260310A: AstroSat CZTI detection of a long burst
  50. GRB 260311A: Fermi GBM Final Real-time Localization
  51. GRB 260310B: Fermi GBM Final Real-time Localization
  52. GRB 260208A: radio detection with the VLA
  53. GRB 260310A: Fermi GBM Final Real-time Localization
  54. GRB 260307A: Glowbug gamma-ray detection
  55. GRB 260308A: Fermi GBM Final Real-time Localization
  56. Fermi GBM Sub-Threshold Detection of GRB 260307B
  57. GRB 260307B: Mephisto optical upper limits
  58. GRB 260307B: possible NOT optical counterpart
  59. GRB 260307B: SVOM/VT upper limit with X band data analysis
  60. GRB 260307B: SVOM/VT optical candidate
  61. GRB 260307B: SVOM detection of a burst
  62. GRB 260307A: Fermi GBM Final Localization
  63. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  64. GRB 260207A: TESS Detection and Possible VLA Counterpart
  65. EP260306a: Gemini-North redshift z = 4.773
  66. EP260306a: Einstein Probe detection of an X-ray transient
  67. EP260302a: Optical afterglow rebrightening
  68. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  69. GRB 260303A: 1.3m DFOT optical upper limit
  70. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  71. GRB 260305A: Fermi GBM Final Real-time Localization
  72. GRB 260303B: AstroSat CZTI detection
  73. GRB 260304A: AstroSat CZTI detection of a long burst
  74. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  75. GRB 260303A: SVOM/VT optical observations
  76. GRB 260303B: NuSTAR detection of prompt emission
  77. GRB 260303B: Fermi GBM Final Real-time Localization
  78. EP260302a: BOOTES-7 optical counterpart detection at early times
  79. GRB 260303A: SVOM detection of a burst
  80. EP260302a: Einstein Probe detection of an X-ray transient
  81. GRB 251130B: TERI Gamma-ray detection
  82. GRB 260208A: TERI Gamma-ray detection
  83. GRB 260302A: Fermi GBM Final Real-time Localization
  84. GRB 260228A: CAHA 2.2m telescope optical upper limit
  85. EP260227a: Mephisto optical detection
  86. GRID detection of GRB 260225D
  87. EP260227A: 3.6m DOT optical afterglow detection
  88. GRB 260228A: SVOM detection of a burst
  89. GRB 260226A: Asiago r-band upper limit
  90. EP260227a: Liverpool Telescope observations
  91. GRID detection of GRB 260223A
  92. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  93. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  94. IceCube cascade alert 142200_1517143 retraction
  95. GRB 260226A: Insight-HXMT/HE detection of the very bright burst
  96. Konus-Wind detection of GRB 260226A
  97. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  98. GRB 260226A: CALET Gamma-Ray Burst Monitor detection
  99. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  100. GRB 260226A: Glowbug gamma-ray detection

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