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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"

11533 results found.

  1. GRB 260825A: Fermi GBM Final Real-time Localization
  2. IceCube-260825A - IceCube observation of a high-energy neutrino candidate track-like event
  3. GRB260822B: Fermi GBM Final Localization
  4. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  5. Fermi-LAT Gamma-ray Observations of IceCube-260807A
  6. GRB 260820A: Insight-HXMT/HE detection
  7. IceCube-260821A - IceCube observation of a high-energy neutrino candidate track-like event
  8. GRB260820A: Fermi GBM Final Real-Time Localization
  9. GRB 260805D: SVOM/GRM detection of a possible magnetar burst
  10. GRB 260813A: BALROG localization (Fermi Trigger 808341387 / GRB 260813803)
  11. GRB 260813A: Fermi GBM Final Real-time Localization
  12. GRB 260808A: SVOM/GRM observation
  13. Fermi GBM Sub-Threshold Detection of GRB 260809A
  14. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  15. GRB 260808A: GECAM-B observation
  16. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  17. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  18. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  19. GRB 260808A: NuSTAR detection of prompt emission
  20. GRB 260808C: Fermi GBM Final Real-time Localization
  21. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  22. Fermi GRB 260808A: Global MASTER-Net observations report
  23. GRB 260808A: Fermi GBM Final Real-time Localization
  24. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  25. GRB 260715A: cubesat Avion detection
  26. GRB 260709A: cubesat Avion detection
  27. GRB 260708A: cubesat Avion detection
  28. SN 2026stf / GRB 260708A: ATLAS forced photometry
  29. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  30. GRB 260805B: Glowbug gamma-ray detection
  31. Fermi GRB 260805A: Global MASTER-Net observations report
  32. GRB 260805B: Fermi GBM Final Localization
  33. GRB 260804A: Glowbug gamma-ray detection
  34. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  35. GRB 260805A: Fermi GBM Final Localization
  36. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  37. GRB 260804A: Fermi GBM Final Real-time Localization
  38. GRB 260708A: LCO further optical observations show supernova features
  39. GRB 260803A: Fermi GBM Final Real-time Localization
  40. Fermi GRB 260802B: Global MASTER-Net observations report
  41. GRB 260802B: Fermi GBM Final Localization
  42. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  43. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  44. GRB 260726A: SVOM/ECLAIRs refined analysis
  45. GRB260730A: Fermi GBM Final Localization
  46. GRB 260726A: EP-FXT follow-up observations
  47. GRB 260726A: Fermi GBM Observation
  48. GRB 260726A: Liverpool Telescope optical observations
  49. GRB 260728A: Fermi GBM Final Localization
  50. GRB 260726A: J-band upper limit with WINTER
  51. GRB 260726A: SVOM/VT optical candidate
  52. GRB 260727B: Fermi GBM Final Real-time Localization
  53. Fermi GRB 260726A: Global MASTER-Net observations report
  54. GRB 260726A: SVOM detection of a burst
  55. GRB 260726A: Fermi GBM Final Real-time Localization
  56. GRB 260616A: cubesat Avion detection
  57. GRB 260602B: cubesat Avion detection
  58. GRB 260601A: cubesat Avion detection
  59. GRB 260718A: SVOM/ECLAIRs refined analysis
  60. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  61. GRB 260723A: Fermi GBM Final Localization
  62. GRB 260722A: Fermi GBM Final Real-time Localization
  63. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  64. Fermi GBM trigger 806384210/260722151 is not a GRB
  65. Konus-Wind detection of GRB 260714B
  66. GRB 260714B: Insight-HXMT/HE detection
  67. GRB 260718A: EP-FXT follow-up observation
  68. Fermi trigger No 806104130: Global MASTER-Net observations report
  69. Fermi GRB 260718A: Global MASTER-Net observations report
  70. GRB 260718A: LCO optical upper limits
  71. GRB 260710A: SVOM/GRM observation
  72. GRB 260718A: Fermi GBM Observation
  73. GRB 260714B: SVOM/GRM observation
  74. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  75. GRB 260714B: GECAM-B observation of a burst
  76. GRB 260618B: EP-FXT follow-up observation upper limit
  77. GRB 260714B: COLIBRÍ optical counterpart candidate
  78. GRB 260715A: Fermi GBM Final Real-time Localization
  79. GRB 260710A: AstroSat CZTI detection
  80. GRB 260709A: AstroSat CZTI detection
  81. GRB 260714B: AstroSat CZTI detection
  82. GRB 260714B: Fermi-LAT detection
  83. GRB 260714B: Fermi GBM Detection
  84. GRB 260714B: BALROG localization (Fermi Trigger 805746211 / GRB 260714766)
  85. GRB 260714B: Fermi GBM Final Real-time Localization
  86. GRB 260706A: ATCA detection of possible radio counterpart
  87. GRB 260705A: ATCA radio observations
  88. GRB 260714A: Fermi GBM Final Real-time Localization
  89. GRB 260619A: SVOM/VT continuous optical observations
  90. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  91. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  92. GRB 260708A: GRANDMA Optical Observations
  93. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  94. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  95. GRB 260710A: Insight-HXMT/HE detection
  96. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  97. IceCube-260712A - IceCube observation of a high-energy neutrino candidate track-like event
  98. GRB 260708A: LCO optical observations
  99. GRB 260710A: Fermi GBM Detection
  100. GRB 260709A: SVOM/GRM detection

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