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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"

23436 results found.

  1. GRB 260402C: AstroSat CZTI detection of a long burst
  2. EP260324A / AT 2026hir: COLIBRÍ optical observations
  3. GRB 260403A: Fermi GBM Final Real-time Localization
  4. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  5. GRB 260402A: WINTER J-band upper limit
  6. GRB260402A: GROWTH-India Telescope optical upper limit
  7. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  8. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  9. GRB 260401A: SVOM/GRM observation
  10. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  11. GRB 260402A: Kilonova-Catcher optical upper limit
  12. GRB 260402A: MASTER optical observations
  13. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  14. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  15. GRB 260402A: SVOM detection of a burst
  16. EP260329b: Mondy and Assy-Turgen optical upper limits
  17. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  18. EP260321a :Xinglong optical observations
  19. EP260327a: Xinglong optical upper limit
  20. EP260329b: GOTO detection of optical counterpart
  21. GRB 260330B: SVOM/VT optical upper limits
  22. GRB 260321A: SVOM/ECLAIRs refined analysis
  23. EP260329b: J-band upper limits with WINTER
  24. EP260329a: J-band upper limit with WINTER
  25. GRB 260330A: Glowbug gamma-ray detection
  26. GRB 260310A: VLA Multi-frequency Radio Observations
  27. GRB 260330B: LCO optical upper limits
  28. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  29. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  30. EP260329a: COLIBRÍ optical upper limit
  31. EP260329a: EP-FXT follow up observation
  32. EP260329a: NOT optical counterpart candidate
  33. EP260329b: Optical follow-up with Kinder observations
  34. EP 260329b: COLIBRÍ optical observations
  35. EP260329a: Optical upper limit with Kinder observations
  36. EP260329b: LCO optical observations of the counterpart
  37. EP260329b: Einstein Probe detection of an X-ray transient
  38. EP260329a: Einstein Probe detection of an X-ray transient
  39. EP-WXT trigger 01709259209: TRT optical counterpart detection
  40. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  41. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  42. EP260327a: SVOM/VT optical upper limits
  43. GRB 260307B: ATCA Radio Upper Limits
  44. EP260327a: WINTER J-band upper limit
  45. EP260327a: COLIBRÍ optical upper limits
  46. GRB 260327A: AstroSat CZTI detection of a long burst
  47. EP260327a: Gemini-North optical upper limits
  48. EP260324a: GROWTH-India Telescope optical observation
  49. EP260327a: Einstein Probe detection of an X-ray transient
  50. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  51. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  52. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  53. IPN triangulation of GRB 260320A
  54. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  55. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  56. EP260321a: JinShan near-infrared observations
  57. EP260321a: Upper limits from a neutrino search with IceCube
  58. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  59. IPN triangulation of GRB 260316B
  60. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  61. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  62. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  63. GRB 260320A: Glowbug gamma-ray detection
  64. EP260321a: COLIBRÍ further optical observations and brightening
  65. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  66. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  67. EP260321a: GOTO detection of blue variable source
  68. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  69. EP260321a: further Kinder optical observations
  70. GRB 260321A: SVOM/VT optical upper limits
  71. EP260321a: Las Cumbres upper limit
  72. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  73. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  74. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  75. EP260321a: SVOM/VT optical upper limit
  76. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  77. EP260321a: Einstein Probe detection of an X-ray transient
  78. GRB 260318A: Glowbug gamma-ray detection
  79. GRB 260310A / AT 2026fgk: KAIT optical observations
  80. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  81. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  82. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  83. GRB 260318A: SVOM/GRM observation
  84. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  85. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  86. GRB 260310A / AT 2026fgk: radio detection with the VLA
  87. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  88. GRB 260310A / AT2026fgk: LCO optical observations
  89. GRB 260316B: SVOM/GRM observation
  90. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  91. EP260316a: COLIBRÍ faint optical counterpart candidate
  92. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  93. EP260316a: Xinglong optical upper limit
  94. EP260316a: optical upper limit with Kinder observations
  95. GRB 260314A: Glowbug gamma-ray detection
  96. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  97. IceCube-260315A: COLIBRÍ optical observations
  98. EP260314a: Xinglong optical upper limit
  99. EP260314a: optical upper limit with Kinder observations
  100. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate

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