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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"

37518 results found.

  1. GRB 260809A: J-band upper limit with WINTER
  2. GRB 260806A: Glowbug gamma-ray detection
  3. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  4. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  5. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  6. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  7. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  8. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  9. GRB 260809A: NOT optical observations
  10. GRB260809A: MAO/AZT-22 optical observations
  11. GRB260809A: OHP/T193 optical observations
  12. GRB 260809A: SVOM/VT optical counterpart
  13. GRB 260808B: J-band upper limit with WINTER
  14. GRB 260808B: SVOM/ECLAIRs refined analysis
  15. GRB 260809A: SVOM detection of a faint burst
  16. GRB 260808B: Liverpool Telescope optical observations
  17. GRB 260808B: NOT optical observations
  18. GRB 260808B: LCO optical observations
  19. GRB 260808A: NuSTAR detection of prompt emission
  20. GRB260808B: OHP/T193 optical observations
  21. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  22. GRB 260808B: SVOM/VT optical afterglow confirmation
  23. GRB 260808C: Fermi GBM Final Real-time Localization
  24. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  25. GRB 260808B: SVOM/VT optical candidate from VHF data
  26. GRB 260808B: SVOM detection of a faint burst
  27. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  28. Fermi GRB 260808A: Global MASTER-Net observations report
  29. GRB 260808A: Fermi GBM Final Real-time Localization
  30. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  31. GRB 260807A: SVOM possible detection of a faint burst
  32. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  33. GRB 260715A: cubesat Avion detection
  34. GRB 260709A: cubesat Avion detection
  35. GRB 260708A: cubesat Avion detection
  36. SN 2026stf / GRB 260708A: ATLAS forced photometry
  37. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  38. GRB 260730B: Glowbug gamma-ray detection
  39. GRB 260805C: Glowbug gamma-ray detection
  40. GRB 260805B: Glowbug gamma-ray detection
  41. Fermi GRB 260805A: Global MASTER-Net observations report
  42. GRB 260805B: Fermi GBM Final Localization
  43. GRB 260804A: Glowbug gamma-ray detection
  44. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  45. GRB 260805A: Fermi GBM Final Localization
  46. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  47. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  48. GRB 260804A: Fermi GBM Final Real-time Localization
  49. GRB 260708A: LCO further optical observations show supernova features
  50. GRB 260803A: Fermi GBM Final Real-time Localization
  51. Fermi GRB 260802B: Global MASTER-Net observations report
  52. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  53. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  54. GRB 260802A: SVOM/VT optical upper limits from VHF data
  55. GRB 260802A: LCO optical upper limits
  56. GRB 260802B: Fermi GBM Final Localization
  57. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  58. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  59. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  60. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  61. GRB 260731A: AstroSat CZTI detection of a long burst
  62. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  63. GRB 260730B: AstroSat CZTI detection
  64. GRB 260730B: NuSTAR detection of prompt emission
  65. GRB 260727A: SVOM/ECLAIRs refined analysis
  66. GRB 260726A: SVOM/ECLAIRs refined analysis
  67. GRB260730A: Fermi GBM Final Localization
  68. EP260727a: SAO RAS optical observations
  69. GRB 260727A: AbAO and SAO RAS optical observations
  70. GRB 260726A: EP-FXT follow-up observations
  71. GRB 260727A: SVOM/GRM observation
  72. GRB 260726A: Fermi GBM Observation
  73. Konus-Wind detection of GRB 260727A
  74. GRB 260726A: Liverpool Telescope optical observations
  75. GRB 260727A: Liverpool Telescope optical upper limits
  76. GRB 260728A: Fermi GBM Final Localization
  77. GRB 260727A: EP/FXT follow-up observations
  78. GRB 260727A: Glowbug gamma-ray detection
  79. GRB 260726A: J-band upper limit with WINTER
  80. GRB 260727A: J-band upper limit with WINTER
  81. GRB 260726A: SVOM/VT optical candidate
  82. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  83. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  84. GRB 260727A: GOTO early optical upper limit
  85. GRB 260727A: AstroSat CZTI detection
  86. GRB 260727A: Kilonova-Catcher optical upper limit
  87. GRB 260727A: LCO optical upper limits
  88. GRB 260727B: Fermi GBM Final Real-time Localization
  89. Fermi GRB 260726A: Global MASTER-Net observations report
  90. GRB 260727A: SVOM detection of a bright long burst
  91. GRB 260726A: SVOM detection of a burst
  92. GRB 260726A: Fermi GBM Final Real-time Localization
  93. GRB 260616A: cubesat Avion detection
  94. GRB 260602B: cubesat Avion detection
  95. GRB 260601A: cubesat Avion detection
  96. IPN triangulation of GRB 260706B
  97. GRB 260718A: SVOM/ECLAIRs refined analysis
  98. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  99. GRB 260723A: Fermi GBM Final Localization
  100. Konus-Wind detection of GRB 260721A

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