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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"

37982 results found.

  1. GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
  2. GRB 260822A: Retraction of GOTO optical counterpart detection GCN 45431
  3. GRB 260822A: GOTO optical counterpart detection
  4. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  5. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  6. GRB 260822A: LCO optical upper limits
  7. GRB260822B: Fermi GBM Final Localization
  8. GRB 260822A: GROWTH-India Telescope Upper Limits
  9. GRB 260822A: GOTO optical upper limit
  10. GRB 260822A: SVOM detection of a short burst
  11. GRB 260818B: VLA radio observations
  12. GRB 260818B: SVOM/C-GFT optical upper limit
  13. IceCube Alert 260821A: Global MASTER-Net observations report
  14. GRB 260820A: Insight-HXMT/HE detection
  15. GRB 260818B: SVOM/GRM observation
  16. GRB260820A: Fermi GBM Final Real-Time Localization
  17. GRB 260818B: Insight-HXMT detection
  18. GRB 260818B: EP-FXT follow-up observation
  19. GRB 260818A: J-band observations with WINTER
  20. GRB 260818B: SVOM/ECLAIRs refined analysis
  21. GRB 260818A: SVOM/ECLAIRs refined analysis
  22. GRB 260818B: NOT optical upper limits
  23. GRB 260810A: SVOM/GRM observation
  24. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  25. GRB260818A: EP-FXT follow-up observation
  26. GRB 260818B: LCO optical upper limits
  27. GRB 260818B: SVOM detection of a short burst
  28. SVOM trigger sb26081806 is not a GRB
  29. EP260806a: SAO RAS multicolor optical observations
  30. GRB 260818A: LCO optical upper limits
  31. EP260812a: AbAO optical upper limit
  32. GRB 260818A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  33. GRB 260810A: Insight-HXMT/HE detection
  34. GRB 260818A: SVOM possible detection of a long and faint GRB
  35. GRB 260805D: SVOM/GRM detection of a possible magnetar burst
  36. GRB 260808B: Liverpool Telescope further optical observations
  37. GRB 260808B: GTC/OSIRIS+ spectroscopic redshift z = 1.295
  38. GRB 260813A: BALROG localization (Fermi Trigger 808341387 / GRB 260813803)
  39. GRB 260813A: Fermi GBM Final Real-time Localization
  40. GRB 260808A: SVOM/GRM observation
  41. Fermi GBM Sub-Threshold Detection of GRB 260809A
  42. GRB 260810A: Glowbug gamma-ray detection
  43. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  44. GRB 260810A: AstroSat CZTI detection of a long burst
  45. GRB 260809A: SAO RAS optical observations
  46. GRB 260808B: SAO RAS optical observations
  47. GRB 260808B: SVOM/VT optical re-brightening at day 3
  48. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  49. GRB 260806A: CALET Gamma-Ray Burst Monitor detection
  50. GRB 260808A: GECAM-B observation
  51. GRB 260807A: SVOM/ECLAIRs refined analysis
  52. GRB260808B: MAO/AZT-22 optical observations
  53. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  54. GRB 260809A: J-band upper limit with WINTER
  55. GRB 260806A: Glowbug gamma-ray detection
  56. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  57. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  58. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  59. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  60. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  61. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  62. GRB 260809A: NOT optical observations
  63. GRB260809A: MAO/AZT-22 optical observations
  64. GRB260809A: OHP/T193 optical observations
  65. GRB 260809A: SVOM/VT optical counterpart
  66. GRB 260808B: J-band upper limit with WINTER
  67. GRB 260808B: SVOM/ECLAIRs refined analysis
  68. GRB 260809A: SVOM detection of a faint burst
  69. GRB 260808B: Liverpool Telescope optical observations
  70. GRB 260808B: NOT optical observations
  71. GRB 260808B: LCO optical observations
  72. GRB 260808A: NuSTAR detection of prompt emission
  73. GRB260808B: OHP/T193 optical observations
  74. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  75. GRB 260808B: SVOM/VT optical afterglow confirmation
  76. GRB 260808C: Fermi GBM Final Real-time Localization
  77. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  78. GRB 260808B: SVOM/VT optical candidate from VHF data
  79. GRB 260808B: SVOM detection of a faint burst
  80. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  81. Fermi GRB 260808A: Global MASTER-Net observations report
  82. GRB 260808A: Fermi GBM Final Real-time Localization
  83. IceCube Alert 260807A: Global MASTER-Net observations report
  84. IceCube-260805A: One candidate from the Zwicky Transient Facility
  85. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  86. GRB 260807A: SVOM possible detection of a faint burst
  87. GRB 260715A: cubesat Avion detection
  88. GRB 260709A: cubesat Avion detection
  89. GRB 260708A: cubesat Avion detection
  90. SN 2026stf / GRB 260708A: ATLAS forced photometry
  91. GRB 260730B: Glowbug gamma-ray detection
  92. GRB 260805C: Glowbug gamma-ray detection
  93. GRB 260805B: Glowbug gamma-ray detection
  94. Fermi GRB 260805A: Global MASTER-Net observations report
  95. GRB 260805B: Fermi GBM Final Localization
  96. GRB 260804A: Glowbug gamma-ray detection
  97. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  98. GRB 260805A: Fermi GBM Final Localization
  99. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  100. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova

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