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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"

11835 results found.

  1. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  2. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  3. GRB 260326A: Fermi GBM Detection
  4. GRB 260325A: Fermi GBM Final Localization
  5. GRB 260326A: Fermi GBM Final Real-time Localization
  6. EP260321a: Upper limits from a neutrino search with IceCube
  7. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  8. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  9. IPN triangulation of GRB 260316B
  10. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  11. GRB 260310A: LBT optical observations
  12. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  13. Fermi GRB 260323A: Global MASTER-Net observations report
  14. GRB 260323A: Fermi GBM Final Real-time Localization
  15. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  16. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  17. GRB 260322A: Fermi GBM Final Localization
  18. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  19. GRB 260310A: continued optical observation at Mondy
  20. Fermi GBM Sub-Threshold Detection of GRB 260321A
  21. GRB 260318A: Glowbug gamma-ray detection
  22. GRB 260310A / AT 2026fgk: KAIT optical observations
  23. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  24. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  25. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  26. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  27. GRB 260310A/AT2026fgk: LBT near-infrared observations
  28. GRB 260318A: SVOM/GRM observation
  29. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  30. GRB 260318A: GECAM-B observation
  31. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  32. Fermi GRB 260318A: Global MASTER-Net observations report
  33. GRB 260318A: Fermi GBM Final Real-time Localization
  34. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  35. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  36. GRB 260310A / AT 2026fgk: radio detection with the VLA
  37. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  38. GRB 260310A / AT2026fgk: LCO optical observations
  39. GRB 260317A: Fermi GBM Final Localization
  40. GRB 260316B: GECAM-B observation
  41. GRB 260316B: SVOM/GRM observation
  42. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  43. EP260316a: COLIBRÍ faint optical counterpart candidate
  44. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  45. GRB 260316B: AstroSat CZTI detection
  46. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  47. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  48. GRB 260316B: Fermi GBM Final Real-time Localization
  49. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  50. GRB 260314A: Glowbug gamma-ray detection
  51. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  52. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  53. GRB 260310A / AT 2026fgk: iTelescope optical observations
  54. GRID detection of GRB 260312B
  55. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  56. Fermi trigger No 795185313: Global MASTER-Net observations report
  57. GRB 260314A: GECAM-B observation of a burst
  58. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  59. GRB 260310A / AT2026fgk: SAO RAS optical observations
  60. GRB 260310A/AT2026fgk: radio detection at 15GHz
  61. GRB 260310A / AT2026fgk: TNG NIR detection
  62. GRB 260310A / AT2026fgk: OASDG optical observations
  63. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  64. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  65. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  66. Fermi GRB 260314A: Global MASTER-Net observations report
  67. Fermi GRB 260313A: Global MASTER-Net observations report
  68. GRB 260314A: Fermi GBM Final Real-time Localization
  69. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  70. GRB 260313A: A Correction to the Fermi GBM Final Localization
  71. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  72. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  73. GRB 260310B: Insight-HXMT/HE detection
  74. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  75. GRB 260312B: AstroSat CZTI detection
  76. GRB 260313A: Fermi GBM Final Real-time Localization
  77. GRB 260308A: Insight-HXMT/HE detection
  78. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  79. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  80. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  81. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  82. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  83. GRB260310A / AT2026fgk: P200 Spectroscopy
  84. GRB 260312B: Glowbug gamma-ray detection
  85. GRB 260310A: Fermi GBM Observation
  86. GRB 260310A: potential optical counterpart
  87. Fermi GRB 260312B: Global MASTER-Net observations report
  88. Fermi GRB 260311B: Global MASTER-Net observations report
  89. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  90. GRB 260312B: Fermi GBM Final Real-time Localization
  91. GRB 260310B: GECAM-B observation of a burst
  92. GRB 260311B: Fermi GBM Final Real-time Localization
  93. GRB 260131A/B: radio detection with the VLA
  94. GRB260307A: GECAM-B observation of a burst
  95. GRB 260308A: SVOM/GRM observation of a short GRB
  96. GRB 260310A: AstroSat CZTI detection of a long burst
  97. GRB 260311A: Fermi GBM Final Real-time Localization
  98. Fermi GRB 260310B: Global MASTER-Net observations report
  99. GRB 260310B: Fermi GBM Final Real-time Localization
  100. Fermi GRB 260310A: Global MASTER-Net observations report

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