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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"

11511 results found.

  1. Fermi GBM Sub-Threshold Detection of GRB 260809A
  2. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  3. GRB 260808A: GECAM-B observation
  4. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  5. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  6. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  7. GRB 260808A: NuSTAR detection of prompt emission
  8. GRB 260808C: Fermi GBM Final Real-time Localization
  9. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  10. Fermi GRB 260808A: Global MASTER-Net observations report
  11. GRB 260808A: Fermi GBM Final Real-time Localization
  12. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  13. GRB 260715A: cubesat Avion detection
  14. GRB 260709A: cubesat Avion detection
  15. GRB 260708A: cubesat Avion detection
  16. SN 2026stf / GRB 260708A: ATLAS forced photometry
  17. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  18. GRB 260805B: Glowbug gamma-ray detection
  19. Fermi GRB 260805A: Global MASTER-Net observations report
  20. GRB 260805B: Fermi GBM Final Localization
  21. GRB 260804A: Glowbug gamma-ray detection
  22. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  23. GRB 260805A: Fermi GBM Final Localization
  24. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  25. GRB 260804A: Fermi GBM Final Real-time Localization
  26. GRB 260708A: LCO further optical observations show supernova features
  27. GRB 260803A: Fermi GBM Final Real-time Localization
  28. Fermi GRB 260802B: Global MASTER-Net observations report
  29. GRB 260802B: Fermi GBM Final Localization
  30. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  31. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  32. GRB 260726A: SVOM/ECLAIRs refined analysis
  33. GRB260730A: Fermi GBM Final Localization
  34. GRB 260726A: EP-FXT follow-up observations
  35. GRB 260726A: Fermi GBM Observation
  36. GRB 260726A: Liverpool Telescope optical observations
  37. GRB 260728A: Fermi GBM Final Localization
  38. GRB 260726A: J-band upper limit with WINTER
  39. GRB 260726A: SVOM/VT optical candidate
  40. GRB 260727B: Fermi GBM Final Real-time Localization
  41. Fermi GRB 260726A: Global MASTER-Net observations report
  42. GRB 260726A: SVOM detection of a burst
  43. GRB 260726A: Fermi GBM Final Real-time Localization
  44. GRB 260616A: cubesat Avion detection
  45. GRB 260602B: cubesat Avion detection
  46. GRB 260601A: cubesat Avion detection
  47. GRB 260718A: SVOM/ECLAIRs refined analysis
  48. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  49. GRB 260723A: Fermi GBM Final Localization
  50. GRB 260722A: Fermi GBM Final Real-time Localization
  51. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  52. Fermi GBM trigger 806384210/260722151 is not a GRB
  53. Konus-Wind detection of GRB 260714B
  54. GRB 260714B: Insight-HXMT/HE detection
  55. GRB 260718A: EP-FXT follow-up observation
  56. Fermi trigger No 806104130: Global MASTER-Net observations report
  57. Fermi GRB 260718A: Global MASTER-Net observations report
  58. GRB 260718A: LCO optical upper limits
  59. GRB 260710A: SVOM/GRM observation
  60. GRB 260718A: Fermi GBM Observation
  61. GRB 260714B: SVOM/GRM observation
  62. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  63. GRB 260714B: GECAM-B observation of a burst
  64. GRB 260618B: EP-FXT follow-up observation upper limit
  65. GRB 260714B: COLIBRÍ optical counterpart candidate
  66. GRB 260715A: Fermi GBM Final Real-time Localization
  67. GRB 260710A: AstroSat CZTI detection
  68. GRB 260709A: AstroSat CZTI detection
  69. GRB 260714B: AstroSat CZTI detection
  70. GRB 260714B: Fermi-LAT detection
  71. GRB 260714B: Fermi GBM Detection
  72. GRB 260714B: BALROG localization (Fermi Trigger 805746211 / GRB 260714766)
  73. GRB 260714B: Fermi GBM Final Real-time Localization
  74. GRB 260706A: ATCA detection of possible radio counterpart
  75. GRB 260705A: ATCA radio observations
  76. GRB 260714A: Fermi GBM Final Real-time Localization
  77. GRB 260619A: SVOM/VT continuous optical observations
  78. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  79. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  80. GRB 260708A: GRANDMA Optical Observations
  81. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  82. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  83. GRB 260710A: Insight-HXMT/HE detection
  84. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  85. IceCube-260712A - IceCube observation of a high-energy neutrino candidate track-like event
  86. GRB 260708A: LCO optical observations
  87. GRB 260710A: Fermi GBM Detection
  88. GRB 260709A: SVOM/GRM detection
  89. GRB 260709A: GECAM-B observation
  90. GRB 260705C: AstroSat CZTI detection
  91. GRB 260710A: Fermi GBM Final Real-time Localization
  92. GRB 260708A: Glowbug gamma-ray detection
  93. GRB 260706A : GRANDMA Upper limits
  94. GRB 260708A: Kilonova-Catcher optical afterglow detection
  95. GRB 260708A: GECAM-B observation of a burst
  96. GRB 260708A: Fermi-GBM observation
  97. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  98. GRB 260709A: Fermi GBM Final Real-time Localization
  99. IceCube-260708A - IceCube observation of a high-energy neutrino candidate track-like event
  100. GRB 260708A: Fermi-LAT detection

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