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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"

11514 results found.

  1. GRB 260813A: BALROG localization (Fermi Trigger 808341387 / GRB 260813803)
  2. GRB 260813A: Fermi GBM Final Real-time Localization
  3. GRB 260808A: SVOM/GRM observation
  4. Fermi GBM Sub-Threshold Detection of GRB 260809A
  5. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  6. GRB 260808A: GECAM-B observation
  7. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  8. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  9. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  10. GRB 260808A: NuSTAR detection of prompt emission
  11. GRB 260808C: Fermi GBM Final Real-time Localization
  12. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  13. Fermi GRB 260808A: Global MASTER-Net observations report
  14. GRB 260808A: Fermi GBM Final Real-time Localization
  15. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  16. GRB 260715A: cubesat Avion detection
  17. GRB 260709A: cubesat Avion detection
  18. GRB 260708A: cubesat Avion detection
  19. SN 2026stf / GRB 260708A: ATLAS forced photometry
  20. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  21. GRB 260805B: Glowbug gamma-ray detection
  22. Fermi GRB 260805A: Global MASTER-Net observations report
  23. GRB 260805B: Fermi GBM Final Localization
  24. GRB 260804A: Glowbug gamma-ray detection
  25. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  26. GRB 260805A: Fermi GBM Final Localization
  27. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  28. GRB 260804A: Fermi GBM Final Real-time Localization
  29. GRB 260708A: LCO further optical observations show supernova features
  30. GRB 260803A: Fermi GBM Final Real-time Localization
  31. Fermi GRB 260802B: Global MASTER-Net observations report
  32. GRB 260802B: Fermi GBM Final Localization
  33. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  34. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  35. GRB 260726A: SVOM/ECLAIRs refined analysis
  36. GRB260730A: Fermi GBM Final Localization
  37. GRB 260726A: EP-FXT follow-up observations
  38. GRB 260726A: Fermi GBM Observation
  39. GRB 260726A: Liverpool Telescope optical observations
  40. GRB 260728A: Fermi GBM Final Localization
  41. GRB 260726A: J-band upper limit with WINTER
  42. GRB 260726A: SVOM/VT optical candidate
  43. GRB 260727B: Fermi GBM Final Real-time Localization
  44. Fermi GRB 260726A: Global MASTER-Net observations report
  45. GRB 260726A: SVOM detection of a burst
  46. GRB 260726A: Fermi GBM Final Real-time Localization
  47. GRB 260616A: cubesat Avion detection
  48. GRB 260602B: cubesat Avion detection
  49. GRB 260601A: cubesat Avion detection
  50. GRB 260718A: SVOM/ECLAIRs refined analysis
  51. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  52. GRB 260723A: Fermi GBM Final Localization
  53. GRB 260722A: Fermi GBM Final Real-time Localization
  54. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  55. Fermi GBM trigger 806384210/260722151 is not a GRB
  56. Konus-Wind detection of GRB 260714B
  57. GRB 260714B: Insight-HXMT/HE detection
  58. GRB 260718A: EP-FXT follow-up observation
  59. Fermi trigger No 806104130: Global MASTER-Net observations report
  60. Fermi GRB 260718A: Global MASTER-Net observations report
  61. GRB 260718A: LCO optical upper limits
  62. GRB 260710A: SVOM/GRM observation
  63. GRB 260718A: Fermi GBM Observation
  64. GRB 260714B: SVOM/GRM observation
  65. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  66. GRB 260714B: GECAM-B observation of a burst
  67. GRB 260618B: EP-FXT follow-up observation upper limit
  68. GRB 260714B: COLIBRÍ optical counterpart candidate
  69. GRB 260715A: Fermi GBM Final Real-time Localization
  70. GRB 260710A: AstroSat CZTI detection
  71. GRB 260709A: AstroSat CZTI detection
  72. GRB 260714B: AstroSat CZTI detection
  73. GRB 260714B: Fermi-LAT detection
  74. GRB 260714B: Fermi GBM Detection
  75. GRB 260714B: BALROG localization (Fermi Trigger 805746211 / GRB 260714766)
  76. GRB 260714B: Fermi GBM Final Real-time Localization
  77. GRB 260706A: ATCA detection of possible radio counterpart
  78. GRB 260705A: ATCA radio observations
  79. GRB 260714A: Fermi GBM Final Real-time Localization
  80. GRB 260619A: SVOM/VT continuous optical observations
  81. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  82. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  83. GRB 260708A: GRANDMA Optical Observations
  84. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  85. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  86. GRB 260710A: Insight-HXMT/HE detection
  87. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  88. IceCube-260712A - IceCube observation of a high-energy neutrino candidate track-like event
  89. GRB 260708A: LCO optical observations
  90. GRB 260710A: Fermi GBM Detection
  91. GRB 260709A: SVOM/GRM detection
  92. GRB 260709A: GECAM-B observation
  93. GRB 260705C: AstroSat CZTI detection
  94. GRB 260710A: Fermi GBM Final Real-time Localization
  95. GRB 260708A: Glowbug gamma-ray detection
  96. GRB 260706A : GRANDMA Upper limits
  97. GRB 260708A: Kilonova-Catcher optical afterglow detection
  98. GRB 260708A: GECAM-B observation of a burst
  99. GRB 260708A: Fermi-GBM observation
  100. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection

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