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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"

26507 results found.

  1. GRB 260330A: Glowbug gamma-ray detection
  2. GRB 260310A: VLA Multi-frequency Radio Observations
  3. GRB 260330B: LCO optical upper limits
  4. GRB 260330B: SVOM detection of a burst
  5. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  6. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  7. EP260329a: COLIBRÍ optical upper limit
  8. EP260329a: EP-FXT follow up observation
  9. EP260329a: NOT optical counterpart candidate
  10. EP260329b: Optical follow-up with Kinder observations
  11. EP 260329b: COLIBRÍ optical observations
  12. EP260329a: Optical upper limit with Kinder observations
  13. EP260329b: LCO optical observations of the counterpart
  14. EP260329b: Einstein Probe detection of an X-ray transient
  15. EP260329a: Einstein Probe detection of an X-ray transient
  16. EP-WXT trigger 01709259209: TRT optical counterpart detection
  17. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  18. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  19. EP260327a: SVOM/VT optical upper limits
  20. EP260327a: WINTER J-band upper limit
  21. EP260327a: COLIBRÍ optical upper limits
  22. EP260327a: Gemini-North optical upper limits
  23. EP260324a: GROWTH-India Telescope optical observation
  24. EP260327a: Einstein Probe detection of an X-ray transient
  25. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  26. The EP-WXT trigger 01709259173 is likely a flaring star
  27. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  28. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  29. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  30. GRB 260326A: Fermi GBM Detection
  31. EP260321a: JinShan near-infrared observations
  32. EP260321a: Upper limits from a neutrino search with IceCube
  33. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  34. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  35. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  36. The EP-WXT trigger 01709259112 is likely a flaring star
  37. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  38. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  39. GRB 260320A: Glowbug gamma-ray detection
  40. EP260321a: COLIBRÍ further optical observations and brightening
  41. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  42. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  43. The EP-WXT trigger 01709259045 is likely a flaring star
  44. EP260321a: GOTO detection of blue variable source
  45. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  46. EP260321a: further Kinder optical observations
  47. GRB 260321A: SVOM/VT optical upper limits
  48. EP260321a: Las Cumbres upper limit
  49. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  50. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  51. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  52. EP260321a: SVOM/VT optical upper limit
  53. GRB 260321A: SVOM detection of a burst
  54. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  55. EP260321a: Einstein Probe detection of an X-ray transient
  56. GRB 260318A: Glowbug gamma-ray detection
  57. GRB 260310A / AT 2026fgk: KAIT optical observations
  58. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  59. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  60. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  61. NOEMA Detection of GRB 260310A / AT 2026fgk
  62. GRB 260318A: SVOM/GRM observation
  63. The EP-WXT trigger 01709258989 is likely a flaring star
  64. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  65. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  66. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  67. GRB 260310A / AT 2026fgk: radio detection with the VLA
  68. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  69. GRB 260310A / AT2026fgk: LCO optical observations
  70. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  71. GRB 260316B: SVOM/GRM observation
  72. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  73. EP260316a: COLIBRÍ faint optical counterpart candidate
  74. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  75. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  76. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  77. EP260316a: Xinglong optical upper limit
  78. EP260316a: optical upper limit with Kinder observations
  79. GRB 260314A: Glowbug gamma-ray detection
  80. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  81. IceCube-260315A: COLIBRÍ optical observations
  82. EP260314a: Xinglong optical upper limit
  83. EP260314a: optical upper limit with Kinder observations
  84. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  85. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  86. GRB 260310A / AT 2026fgk: iTelescope optical observations
  87. EP260314a: COLIBRÍ optical upper limit
  88. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  89. EP260314a: SVOM/VT optical candidate
  90. EP260314a: Einstein Probe detection of an X-ray transient
  91. GRB 260310A / AT2026fgk: SAO RAS optical observations
  92. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  93. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  94. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  95. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  96. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  97. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  98. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  99. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  100. GRB260310A / AT2026fgk: P200 Spectroscopy

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