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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"

28067 results found.

  1. GRB 260810A: Glowbug gamma-ray detection
  2. GRB 260810A: AstroSat CZTI detection of a long burst
  3. EP260812a: Einstein Probe detection of an X-ray transient
  4. GRB 260808B: SVOM/VT optical re-brightening at day 3
  5. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  6. GRB 260806A: CALET Gamma-Ray Burst Monitor detection
  7. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  8. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  9. GRB 260806A: Glowbug gamma-ray detection
  10. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  11. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  12. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  13. GRB 260809A: NOT optical observations
  14. GRB260809A: MAO/AZT-22 optical observations
  15. GRB260809A: OHP/T193 optical observations
  16. GRB 260809A: SVOM detection of a faint burst
  17. GRB 260808B: NOT optical observations
  18. GRB 260808A: NuSTAR detection of prompt emission
  19. GRB260808B: OHP/T193 optical observations
  20. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  21. EP260809a: Einstein Probe detection of an X-ray transient
  22. GRB 260808B: SVOM/VT optical afterglow confirmation
  23. GRB 260808C: Fermi GBM Final Real-time Localization
  24. GRB 260808B: SVOM detection of a faint burst
  25. GRB 260808A: Fermi GBM Final Real-time Localization
  26. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  27. GRB 260807A: SVOM possible detection of a faint burst
  28. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  29. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  30. EP260806a: Einstein Probe detection of an X-ray transient
  31. GRB 260715A: cubesat Avion detection
  32. GRB 260709A: cubesat Avion detection
  33. GRB 260708A: cubesat Avion detection
  34. SN 2026stf / GRB 260708A: ATLAS forced photometry
  35. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  36. GRB 260730B: Glowbug gamma-ray detection
  37. GRB 260805C: Glowbug gamma-ray detection
  38. GRB 260805B: Glowbug gamma-ray detection
  39. GRB 260805B: Fermi GBM Final Localization
  40. GRB 260804A: Glowbug gamma-ray detection
  41. GRB 260805A: Fermi GBM Final Localization
  42. AT 2026wki: EP/FXT follow-up observations
  43. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  44. GRB 260804A: Fermi GBM Final Real-time Localization
  45. GRB 260803A: Fermi GBM Final Real-time Localization
  46. GRB 260802B: Fermi GBM Final Localization
  47. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  48. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  49. GRB 260731A: AstroSat CZTI detection of a long burst
  50. GRB 260730B: AstroSat CZTI detection
  51. GRB 260730B: NuSTAR detection of prompt emission
  52. EP260731a: Einstein Probe detection of an X-ray transient
  53. GRB260730A: Fermi GBM Final Localization
  54. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  55. EP260729a: Einstein Probe detection of an X-ray transient
  56. EP260728a: Einstein Probe detection of a fast X-ray transient
  57. EP260727a: 1.5m OSN optical counterpart detection
  58. Konus-Wind detection of GRB 260727A
  59. GRB 260726A: Liverpool Telescope optical observations
  60. EP260727a: Liverpool Telescope confirmation of optical counterpart
  61. GRB 260728A: Fermi GBM Final Localization
  62. EP260727a: Einstein Probe detection of an X-ray transient
  63. GRB 260727A: Glowbug gamma-ray detection
  64. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  65. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  66. GRB 260727A: AstroSat CZTI detection
  67. GRB 260727B: Fermi GBM Final Real-time Localization
  68. GRB 260727A: SVOM detection of a bright long burst
  69. GRB 260726A: SVOM detection of a burst
  70. GRB 260726A: Fermi GBM Final Real-time Localization
  71. EP260723a: further EP-FXT follow-up observation
  72. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  73. EP260725a: EP-WXT detection of an X-ray transient
  74. GRB 260616A: cubesat Avion detection
  75. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  76. GRB 260602B: cubesat Avion detection
  77. GRB 260601A: cubesat Avion detection
  78. EP260723a: EP-FXT follow-up observation
  79. EP260723a: Liverpool Telescope likely optical counterpart
  80. EP260723a: EP-WXT detection of a fast X-ray transient
  81. GRB 260723A: Fermi GBM Final Localization
  82. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  83. Konus-Wind detection of GRB 260721A
  84. GRB 260722A: Fermi GBM Final Real-time Localization
  85. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  86. GRB 260721A: NuSTAR detection of prompt emission
  87. Konus-Wind detection of GRB 260714B
  88. GRB 260705A: Retraction of optical counterpart
  89. GRB 260714B: Insight-HXMT/HE detection
  90. GRB 260718A: SVOM/VT optical upper limits
  91. GRB 260718A: SVOM/VT optical upper limits from VHF data
  92. GRB 260718A: SVOM detection of a burst
  93. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  94. sb26071506: SVOM detection of a X-ray transient
  95. GRB 260715A: Fermi GBM Final Real-time Localization
  96. GRB 260710A: AstroSat CZTI detection
  97. GRB 260709A: AstroSat CZTI detection
  98. GRB 260714B: AstroSat CZTI detection
  99. GRB 260714B: Fermi-LAT detection
  100. GRB 260714B: Fermi GBM Detection

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