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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"

37943 results found.

  1. GRB 260808A: SVOM/GRM observation
  2. Fermi GBM Sub-Threshold Detection of GRB 260809A
  3. GRB 260810A: Glowbug gamma-ray detection
  4. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  5. GRB 260810A: AstroSat CZTI detection of a long burst
  6. GRB 260809A: SAO RAS optical observations
  7. GRB 260808B: SAO RAS optical observations
  8. GRB 260808B: SVOM/VT optical re-brightening at day 3
  9. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  10. GRB 260806A: CALET Gamma-Ray Burst Monitor detection
  11. GRB 260808A: GECAM-B observation
  12. GRB 260807A: SVOM/ECLAIRs refined analysis
  13. GRB260808B: MAO/AZT-22 optical observations
  14. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  15. GRB 260809A: J-band upper limit with WINTER
  16. GRB 260806A: Glowbug gamma-ray detection
  17. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  18. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  19. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  20. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  21. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  22. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  23. GRB 260809A: NOT optical observations
  24. GRB260809A: MAO/AZT-22 optical observations
  25. GRB260809A: OHP/T193 optical observations
  26. GRB 260809A: SVOM/VT optical counterpart
  27. GRB 260808B: J-band upper limit with WINTER
  28. GRB 260808B: SVOM/ECLAIRs refined analysis
  29. GRB 260809A: SVOM detection of a faint burst
  30. GRB 260808B: Liverpool Telescope optical observations
  31. GRB 260808B: NOT optical observations
  32. GRB 260808B: LCO optical observations
  33. GRB 260808A: NuSTAR detection of prompt emission
  34. GRB260808B: OHP/T193 optical observations
  35. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  36. GRB 260808B: SVOM/VT optical afterglow confirmation
  37. GRB 260808C: Fermi GBM Final Real-time Localization
  38. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  39. GRB 260808B: SVOM/VT optical candidate from VHF data
  40. GRB 260808B: SVOM detection of a faint burst
  41. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  42. Fermi GRB 260808A: Global MASTER-Net observations report
  43. GRB 260808A: Fermi GBM Final Real-time Localization
  44. IceCube Alert 260807A: Global MASTER-Net observations report
  45. IceCube-260805A: One candidate from the Zwicky Transient Facility
  46. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  47. GRB 260807A: SVOM possible detection of a faint burst
  48. GRB 260715A: cubesat Avion detection
  49. GRB 260709A: cubesat Avion detection
  50. GRB 260708A: cubesat Avion detection
  51. SN 2026stf / GRB 260708A: ATLAS forced photometry
  52. GRB 260730B: Glowbug gamma-ray detection
  53. GRB 260805C: Glowbug gamma-ray detection
  54. GRB 260805B: Glowbug gamma-ray detection
  55. Fermi GRB 260805A: Global MASTER-Net observations report
  56. GRB 260805B: Fermi GBM Final Localization
  57. GRB 260804A: Glowbug gamma-ray detection
  58. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  59. GRB 260805A: Fermi GBM Final Localization
  60. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  61. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  62. GRB 260804A: Fermi GBM Final Real-time Localization
  63. GRB 260708A: LCO further optical observations show supernova features
  64. GRB 260803A: Fermi GBM Final Real-time Localization
  65. Fermi GRB 260802B: Global MASTER-Net observations report
  66. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  67. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  68. GRB 260802A: SVOM/VT optical upper limits from VHF data
  69. GRB 260802A: LCO optical upper limits
  70. GRB 260802B: Fermi GBM Final Localization
  71. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  72. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  73. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  74. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  75. GRB 260731A: AstroSat CZTI detection of a long burst
  76. GRB 260730B: AstroSat CZTI detection
  77. GRB 260730B: NuSTAR detection of prompt emission
  78. GRB 260727A: SVOM/ECLAIRs refined analysis
  79. GRB 260726A: SVOM/ECLAIRs refined analysis
  80. GRB260730A: Fermi GBM Final Localization
  81. EP260727a: SAO RAS optical observations
  82. GRB 260727A: AbAO and SAO RAS optical observations
  83. GRB 260726A: EP-FXT follow-up observations
  84. GRB 260727A: SVOM/GRM observation
  85. GRB 260726A: Fermi GBM Observation
  86. Konus-Wind detection of GRB 260727A
  87. GRB 260726A: Liverpool Telescope optical observations
  88. GRB 260727A: Liverpool Telescope optical upper limits
  89. GRB 260728A: Fermi GBM Final Localization
  90. GRB 260727A: EP/FXT follow-up observations
  91. GRB 260727A: Glowbug gamma-ray detection
  92. GRB 260726A: J-band upper limit with WINTER
  93. GRB 260727A: J-band upper limit with WINTER
  94. GRB 260726A: SVOM/VT optical candidate
  95. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  96. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  97. GRB 260727A: GOTO early optical upper limit
  98. GRB 260727A: AstroSat CZTI detection
  99. GRB 260727A: Kilonova-Catcher optical upper limit
  100. GRB 260727A: LCO optical upper limits

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