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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"

8280 results found.

  1. GRB 251103A: NOT optical afterglow candidate (duplicate submission)
  2. GRB 251103A: NOT optical afterglow candidate
  3. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  4. GRB 251026B: LBT near-infrared observations
  5. GRB251026B: PRIME H-band upper limit
  6. IceCube-251025A: Upper limits from a search for additional neutrino events in IceCube
  7. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  8. GRB 251027A: Swift-XRT observations
  9. GRB 251026B: Swift ToO observations
  10. GRB 251023B / EP251023b: Mondy optical upper limit
  11. GRB 251026B: Tentative GOTO optical counterpart candidate
  12. LIGO/Virgo/KAGRA S251026bn: Updated Sky localization
  13. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  14. GRB 251026A: Swift-XRT observations
  15. GRB 251026A: SVOM/C-GFT upper limit
  16. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  17. IceCube-251025A - IceCube observation of a high-energy neutrino candidate track-like event
  18. GRB 251025A: SVOM/VT VHF optical upper limit
  19. GRB 251024A: Swift detection of a burst
  20. GRB 251023B / EP251023b: COLIBRÍ Confirmation of the Fading Nature of the Optical Candidate
  21. GRB 251023B / EP#01709247298: COLIBRÍ optical counterpart candidate
  22. GRB 251022A: DDOTI Optical Detection
  23. EP251021b/GRB 251021A: SVOM/VT optical candidate
  24. EP/WXT 01709247295: GOTO optical afterglow candidate.
  25. GRB 251022A: Tiled Swift observations
  26. GRB 251021A/EP251021b: Fermi-GBM Sub-Threshold Detection
  27. LIGO/Virgo/KAGRA S251021u: Updated Sky localization
  28. LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
  29. LIGO/Virgo/KAGRA S251018bi: Updated Sky localization
  30. IceCube-251018A: Upper limits from a search for additional neutrino events in IceCube
  31. GRB 251018A: BOOTES-5 and BOOTES-7 early optical detections
  32. LIGO/Virgo/KAGRA S251018bi: Identification of a GW compact binary merger candidate
  33. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event
  34. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  35. GRB 251018A: Swift detection of a burst with an optical counterpart
  36. LIGO/Virgo/KAGRA S251017di: Retraction of GW compact binary merger candidate
  37. GRB 251017A : MITSuME Akeno optical afterglow candidate detection
  38. GRB 251017A: Swift detection of a burst with an optical counterpart
  39. GRB 251013C: JinShan observations of the non-thermal rebrightening of the optical counterpart
  40. sb25101602: Swift-XRT counterpart detection
  41. LIGO/Virgo/KAGRA S251014cn: Updated Sky localization
  42. Upper limits from a search for additional neutrino events in IceCube
  43. GRB 251013C: detection of a radio counterpart at 15.5GHz
  44. Swift Trigger 1404295: possible GRB 251015A
  45. IceCube-251014A - IceCube observation of a high-energy neutrino candidate track-like event
  46. GRB 251014B: Swift ToO observations
  47. LIGO/Virgo/KAGRA S251014cn: NED Galaxies in the 3-Initial Localization Volume
  48. GRB 251013D: Swift ToO observations
  49. LIGO/Virgo/KAGRA S251014cn: Identification of a GW compact binary merger candidate
  50. GRB 251013C: SVOM/VT optical observation
  51. LIGO/Virgo/KAGRA S251013x: Updated Sky localization and Source Classification
  52. LIGO/Virgo/KAGRA S251013x: Identification of a GW compact binary merger candidate
  53. IceCube alert 141456_888784 retraction
  54. GRB 251006B/EP251006a: EP-FXT afterglow detection
  55. GRB 251007B: SVOM/VT optical candidate
  56. GRB 251007B: SVOM/C-GFT upper limit
  57. GRB 251007B: Swift detection of a burst
  58. GRB 251007A: Swift detection of a burst with an optical counterpart
  59. GRB 251006B/EP251006a: SVOM/VT optical candidate
  60. GRB 251005C: SVOM/VT optical fading
  61. LIGO/Virgo/KAGRA S251006dd: Identification of a GW compact binary merger candidate
  62. GRB 251005C: VLT/X-shooter Imaging
  63. GRB 251005C: SVOM/VT optical candidate
  64. GRB 251005C: Swift detection of a burst
  65. Fermi GBM Sub-Threshold Detection of GRB 250910A
  66. LIGO/Virgo/KAGRA S251003at: Retraction of GW compact binary merger candidate
  67. GRB 251002A: Swift-XRT afterglow detection
  68. GRB 251003A: 1.5m OSN afterglow candidate
  69. GRB 251003A: Swift detection of a burst
  70. GRB 251002A: SVOM/VT optical observation
  71. GRB 251001B: Swift detection of a burst
  72. LIGO/Virgo/KAGRA S250830bp: SOAR spectroscopy of two DESGW candidates
  73. LIGO/Virgo/KAGRA S250929c: Updated Sky localization
  74. LIGO/Virgo/KAGRA S250929c: Identification of a GW compact binary merger candidate
  75. LIGO/Virgo/KAGRA S250927cy: Updated Sky localization
  76. LIGO/Virgo/KAGRA S250927ck: Updated Sky localization
  77. LIGO/Virgo/KAGRA S250927cy: Identification of a GW compact binary merger candidate
  78. LIGO/Virgo/KAGRA S250927ck: Identification of a GW compact binary merger candidate
  79. IceCube-250926A: Upper limits from a search for additional neutrino events in IceCube
  80. IceCube-250926A - IceCube observation of a high-energy neutrino candidate track-like event
  81. GRB250925A: Liverpool Telescope optical observations
  82. GRB 250925A: NOT optical afterglow candidate
  83. GRB 250925A: Leavitt Observatory optical upper limit
  84. GRB 250924A: 1.6m Mephisto optical upper limits
  85. GRB 250924A: Swift detection of a burst with an optical counterpart
  86. GRB 250920C: COLIBRÍ optical observations
  87. GRB 250920B: NIR observations with WINTER
  88. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  89. GRB250920C: LCOGT Optical Detection
  90. GRB 250920C: GOTO optical counterpart candidate
  91. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  92. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  93. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  94. GRB 250916A: NuSTAR detection of the prompt emission
  95. GRB 250917B: Swift-BAT refined analysis
  96. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  97. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  98. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  99. GRB 250916A: Swift ToO observations
  100. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate

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