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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"

14256 results found.

  1. EP260214b: ATCA 6 GHz detection
  2. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  3. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  4. EP260321a: GOTO detection of blue variable source
  5. EP260321a: further Kinder optical observations
  6. GRB 260320A: Insight-HXMT/HE detection
  7. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  8. Fermi GBM Sub-Threshold Detection of GRB 260321A
  9. GRB 260321A: SVOM detection of a burst
  10. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  11. EP260321a: Einstein Probe detection of an X-ray transient
  12. GRB 260318A: Glowbug gamma-ray detection
  13. GRB 260320A: NuSTAR detection of prompt emission
  14. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  15. GRB 260310A/AT2026fgk: LBT near-infrared observations
  16. NOEMA Detection of GRB 260310A / AT 2026fgk
  17. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  18. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  19. GRB 260318A: Fermi GBM Final Real-time Localization
  20. GRB 260310A / AT 2026fgk: radio detection with the VLA
  21. GRB 260317A: Fermi GBM Final Localization
  22. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  23. GRB 260316B: AstroSat CZTI detection
  24. EP260316a: Xinglong optical upper limit
  25. GRB 260316B: Fermi GBM Final Real-time Localization
  26. EP260316a: optical upper limit with Kinder observations
  27. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  28. GRB 260314A: Glowbug gamma-ray detection
  29. EP260314a: Xinglong optical upper limit
  30. EP260314a: optical upper limit with Kinder observations
  31. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  32. GRID detection of GRB 260312B
  33. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  34. EP260314a: BOOTES-6/DPR optical upper limits at early times
  35. EP260314a: Einstein Probe detection of an X-ray transient
  36. GRB 260310A/AT2026fgk: radio detection at 15GHz
  37. GRB 260310A / AT2026fgk: TNG NIR detection
  38. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  39. GRB 260314A: Fermi GBM Final Real-time Localization
  40. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  41. GRB 260310B: Insight-HXMT/HE detection
  42. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  43. GRB 260312B: AstroSat CZTI detection
  44. GRB 260313A: Fermi GBM Final Real-time Localization
  45. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  46. GRB 260308A: Insight-HXMT/HE detection
  47. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  48. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  49. GRB 260312B: Glowbug gamma-ray detection
  50. GRB 260310A: potential optical counterpart
  51. GRB 260312B: Fermi GBM Final Real-time Localization
  52. GRB 260312A: Swift detection of a burst
  53. GRB 260311B: Fermi GBM Final Real-time Localization
  54. GRB 260131A/B: radio detection with the VLA
  55. GRB 260310A: AstroSat CZTI detection of a long burst
  56. GRB 260311A: Fermi GBM Final Real-time Localization
  57. GRB 260310B: Fermi GBM Final Real-time Localization
  58. GRB 260208A: radio detection with the VLA
  59. GRB 260310A: Fermi GBM Final Real-time Localization
  60. GRB 260307A: Glowbug gamma-ray detection
  61. GRB 260308A: Fermi GBM Final Real-time Localization
  62. Fermi GBM Sub-Threshold Detection of GRB 260307B
  63. GRB 260307B: Mephisto optical upper limits
  64. GRB 260307B: possible NOT optical counterpart
  65. GRB 260307B: SVOM/VT upper limit with X band data analysis
  66. GRB 260307B: SVOM/VT optical candidate
  67. GRB 260307B: SVOM detection of a burst
  68. GRB 260307A: Fermi GBM Final Localization
  69. GRB 260207A: TESS Detection and Possible VLA Counterpart
  70. EP260306a: Gemini-North redshift z = 4.773
  71. EP260306a: Einstein Probe detection of an X-ray transient
  72. GRB 260303A: 1.3m DFOT optical upper limit
  73. EP260214b: ATCA 6 GHz observations
  74. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  75. GRB 260305A: Fermi GBM Final Real-time Localization
  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 260303B: Fermi GBM Final Real-time Localization
  81. EP260302a: BOOTES-7 optical counterpart detection at early times
  82. GRB 260303A: SVOM detection of a burst
  83. EP260302a: Einstein Probe detection of an X-ray transient
  84. GRB 251130B: TERI Gamma-ray detection
  85. GRB 260208A: TERI Gamma-ray detection
  86. GRB 260302A: Fermi GBM Final Real-time Localization
  87. GRB 260228A: CAHA 2.2m telescope optical upper limit
  88. EP260227a: Mephisto optical detection
  89. GRID detection of GRB 260225D
  90. EP260227A: 3.6m DOT optical afterglow detection
  91. GRB 260228A: SVOM detection of a burst
  92. GRB 260226A: Asiago r-band upper limit
  93. EP260227a: Liverpool Telescope observations
  94. EP260227a: NOT optical observations
  95. GRID detection of GRB 260223A
  96. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  97. IceCube cascade alert 142200_1517143 retraction
  98. GRB 260226A: Insight-HXMT/HE detection of the very bright burst
  99. Konus-Wind detection of GRB 260226A
  100. GRB 260223A: 7DT detection and Medium-band SED of Afterglow

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