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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"

8474 results found.

  1. GRB 260924A: Upper limits from a neutrino search with IceCube
  2. Swift Trigger 1513439 is probably not a GRB
  3. GRB 260925A: Swift detection of a burst
  4. GRB 260924A: Swift-BAT refined analysis
  5. GRB 260924A: AstroSat CZTI detection
  6. GRB 260924A: Swift detection of a burst
  7. Trigger_21914: Swift ToO observations
  8. GRB 260922A: Ondrejov D50 optical limit
  9. EP260920a: VLT/HAWK-I near-infrared counterpart confirmation
  10. GRB 260922A: COLIBRÍ Optical Counterpart Candidate (correction to GCN 45698)
  11. GRB 260922A: SVOM/C-GFT optical upper limit
  12. GRB 260922A: Swift detection of a burst
  13. GRB 260917C: AstroSat CZTI detection
  14. GRB 260921A: AstroSat CZTI detection
  15. GRB 260921A: Fermi GBM Observation
  16. EP260920a: VLT/HAWK-I near-infrared candidate
  17. GRB 260920A: AstroSat CZTI detection
  18. EP260920b: COLIBRÍ optical observations
  19. IceCube-260919A: Upper limits from a search for additional neutrino events in IceCube
  20. EP260920a: NOT early time optical upper limits
  21. EP260920a: NOT optical upper limits
  22. EP260920a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  23. EP260920a: COLIBRÍ optical upper limits
  24. EP260920a: Update of the LCO optical counterpart candidate
  25. EP260920a: LCO optical counterpart candidate
  26. GRB 260915A: VLT optical and near-infrared upper limits
  27. IceCube-260919A - IceCube observation of a high-energy neutrino candidate track-like event
  28. GRB 260918A: SVOM/C-GFT optical upper limits
  29. Fermi GBM Sub-Threshold Detection of GRB 260918A
  30. GRB 260917B: EP-FXT follow-up observation
  31. IceCube-260916A: Upper limits from a search for additional neutrino events in IceCube
  32. GRB 260917B: SVOM/VT optical observations
  33. GRB 260917B: LCO optical observation
  34. GRB 260917B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  35. IceCube-260916A - IceCube observation of a high-energy neutrino candidate track-like event
  36. GRB 260914A: SVOM/ECLAIRs refined analysis
  37. GRB 260909A: Swift-XRT observations
  38. GRB 260915A: Swift ToO observations
  39. GRB 260915A: SVOM/C-GFT optical upper limits
  40. GRB 260915A: SVOM/VT optical upper limits
  41. Fermi GBM Sub-Threshold Detection of GRB 260915A
  42. Fermi GBM Sub-Threshold Detection of GRB 260914A
  43. GRB 260914A: SVOM/C-GFT optical observations
  44. GRB 260914A: SVOM/VT optical observation from VHF data
  45. GRB 260914A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  46. GRB 260818A: Continued ATCA observations
  47. GRB 260913A: SVOM/C-GFT optical upper limit
  48. GRB 260909A: CrAO and AbAO optical upper limits
  49. GRB 260910B: GOTO tentative optical counterpart candidates
  50. GRB 260909A: Swift ToO observations
  51. GRB 260909A: SVOM/VT optical upper limits
  52. GRB 260909A: Mondy optical observations and afterglow candidate
  53. GRB 260909A: SVOM/C-GFT optical upper limit
  54. GRB 260903A: Swift ToO observations
  55. GRB 260903A: SVOM/VT optical candidate
  56. EP260901a: SVOM/VT optical upper limits
  57. GRB 260818A: ATCA detection of a candidate radio counterpart
  58. IceCube-260827A: No transient candidates from the Zwicky Transient Facility
  59. GRB 260829A: AstroSat CZTI detection
  60. GRB 260825A: AstroSat CZTI detection
  61. IceCube-260827A: Upper limits from a search for additional neutrino events in IceCube
  62. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  63. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  64. GRB 260818B: Further EP-FXT observation
  65. GRB 260818B: VLT optical and nIR observations
  66. GRB 260818B: TNG NIR observations
  67. IceCube-260827A - IceCube observation of a high-energy neutrino candidate track-like event
  68. GRB 260818B: 6 GHz VLA observations
  69. GRB 260818B: SVOM/VT optical upper limit and continuous observations
  70. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  71. IceCube-260825A: No transient candidates from the Zwicky Transient Facility
  72. GRB 260822A: SVOM/VT optical upper limits
  73. IceCube-Cascade 260824A: Upper limits from a search for additional neutrino events in IceCube
  74. IceCube-260825A - IceCube observation of a high-energy neutrino candidate track-like event
  75. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  76. GRB 260822A: GOTO optical counterpart detection
  77. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  78. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  79. GRB 260822A: LCO optical upper limits
  80. IceCube-260821A: Upper limits from a search for additional neutrino events in IceCube
  81. GRB 260818B: SVOM/C-GFT optical upper limit
  82. IceCube-260821A - IceCube observation of a high-energy neutrino candidate track-like event
  83. EP260806a: WFST optical observations
  84. EP260812a: SVOM/C-GFT optical upper limit
  85. Fermi GBM Sub-Threshold Detection of GRB 260809A
  86. GRB 260810A: AstroSat CZTI detection of a long burst
  87. IceCube-260807A: Upper limits from a search for additional neutrino events in IceCube
  88. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  89. GRB 260808B: SVOM/VT optical afterglow confirmation
  90. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  91. GRB 260808B: SVOM/VT optical candidate from VHF data
  92. IceCube-260805A: One candidate from the Zwicky Transient Facility
  93. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  94. EP260806a: OSIRIS+/GTC redshift z=0.089
  95. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  96. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  97. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  98. GRB 260802A: SVOM/VT optical upper limits from VHF data
  99. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  100. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay

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