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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 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  2. GRB 251027A: Swift-XRT observations
  3. GRB 251026B: Swift ToO observations
  4. GRB 251023B / EP251023b: Mondy optical upper limit
  5. GRB 251026B: Tentative GOTO optical counterpart candidate
  6. LIGO/Virgo/KAGRA S251026bn: Updated Sky localization
  7. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  8. GRB 251026A: Swift-XRT observations
  9. GRB 251026A: SVOM/C-GFT upper limit
  10. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  11. IceCube-251025A - IceCube observation of a high-energy neutrino candidate track-like event
  12. GRB 251025A: SVOM/VT VHF optical upper limit
  13. GRB 251024A: Swift detection of a burst
  14. GRB 251023B / EP251023b: COLIBRÍ Confirmation of the Fading Nature of the Optical Candidate
  15. GRB 251023B / EP#01709247298: COLIBRÍ optical counterpart candidate
  16. GRB 251022A: DDOTI Optical Detection
  17. EP251021b/GRB 251021A: SVOM/VT optical candidate
  18. EP/WXT 01709247295: GOTO optical afterglow candidate.
  19. GRB 251022A: Tiled Swift observations
  20. GRB 251021A/EP251021b: Fermi-GBM Sub-Threshold Detection
  21. LIGO/Virgo/KAGRA S251021u: Updated Sky localization
  22. LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
  23. LIGO/Virgo/KAGRA S251018bi: Updated Sky localization
  24. IceCube-251018A: Upper limits from a search for additional neutrino events in IceCube
  25. GRB 251018A: BOOTES-5 and BOOTES-7 early optical detections
  26. LIGO/Virgo/KAGRA S251018bi: Identification of a GW compact binary merger candidate
  27. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event
  28. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  29. GRB 251018A: Swift detection of a burst with an optical counterpart
  30. LIGO/Virgo/KAGRA S251017di: Retraction of GW compact binary merger candidate
  31. GRB 251017A : MITSuME Akeno optical afterglow candidate detection
  32. GRB 251017A: Swift detection of a burst with an optical counterpart
  33. GRB 251013C: JinShan observations of the non-thermal rebrightening of the optical counterpart
  34. sb25101602: Swift-XRT counterpart detection
  35. LIGO/Virgo/KAGRA S251014cn: Updated Sky localization
  36. Upper limits from a search for additional neutrino events in IceCube
  37. GRB 251013C: detection of a radio counterpart at 15.5GHz
  38. Swift Trigger 1404295: possible GRB 251015A
  39. IceCube-251014A - IceCube observation of a high-energy neutrino candidate track-like event
  40. GRB 251014B: Swift ToO observations
  41. LIGO/Virgo/KAGRA S251014cn: NED Galaxies in the 3-Initial Localization Volume
  42. GRB 251013D: Swift ToO observations
  43. LIGO/Virgo/KAGRA S251014cn: Identification of a GW compact binary merger candidate
  44. GRB 251013C: SVOM/VT optical observation
  45. LIGO/Virgo/KAGRA S251013x: Updated Sky localization and Source Classification
  46. LIGO/Virgo/KAGRA S251013x: Identification of a GW compact binary merger candidate
  47. IceCube alert 141456_888784 retraction
  48. GRB 251006B/EP251006a: EP-FXT afterglow detection
  49. GRB 251007B: SVOM/VT optical candidate
  50. GRB 251007B: SVOM/C-GFT upper limit
  51. GRB 251007B: Swift detection of a burst
  52. GRB 251007A: Swift detection of a burst with an optical counterpart
  53. GRB 251006B/EP251006a: SVOM/VT optical candidate
  54. GRB 251005C: SVOM/VT optical fading
  55. LIGO/Virgo/KAGRA S251006dd: Identification of a GW compact binary merger candidate
  56. GRB 251005C: VLT/X-shooter Imaging
  57. GRB 251005C: SVOM/VT optical candidate
  58. GRB 251005C: Swift detection of a burst
  59. Fermi GBM Sub-Threshold Detection of GRB 250910A
  60. LIGO/Virgo/KAGRA S251003at: Retraction of GW compact binary merger candidate
  61. GRB 251002A: Swift-XRT afterglow detection
  62. GRB 251003A: 1.5m OSN afterglow candidate
  63. GRB 251003A: Swift detection of a burst
  64. GRB 251002A: SVOM/VT optical observation
  65. GRB 251001B: Swift detection of a burst
  66. LIGO/Virgo/KAGRA S250830bp: SOAR spectroscopy of two DESGW candidates
  67. LIGO/Virgo/KAGRA S250929c: Updated Sky localization
  68. LIGO/Virgo/KAGRA S250929c: Identification of a GW compact binary merger candidate
  69. LIGO/Virgo/KAGRA S250927cy: Updated Sky localization
  70. LIGO/Virgo/KAGRA S250927ck: Updated Sky localization
  71. LIGO/Virgo/KAGRA S250927cy: Identification of a GW compact binary merger candidate
  72. LIGO/Virgo/KAGRA S250927ck: Identification of a GW compact binary merger candidate
  73. IceCube-250926A: Upper limits from a search for additional neutrino events in IceCube
  74. IceCube-250926A - IceCube observation of a high-energy neutrino candidate track-like event
  75. GRB250925A: Liverpool Telescope optical observations
  76. GRB 250925A: NOT optical afterglow candidate
  77. GRB 250925A: Leavitt Observatory optical upper limit
  78. GRB 250924A: 1.6m Mephisto optical upper limits
  79. GRB 250924A: Swift detection of a burst with an optical counterpart
  80. GRB 250920C: COLIBRÍ optical observations
  81. GRB 250920B: NIR observations with WINTER
  82. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  83. GRB250920C: LCOGT Optical Detection
  84. GRB 250920C: GOTO optical counterpart candidate
  85. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  86. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  87. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  88. GRB 250916A: NuSTAR detection of the prompt emission
  89. GRB 250917B: Swift-BAT refined analysis
  90. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  91. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  92. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  93. GRB 250916A: Swift ToO observations
  94. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  95. GRB 250917B: Swift detection of a short burst
  96. GRB 250916A: GOTO optical counterpart candidate
  97. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  98. GRB 250912A: VLT observations
  99. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  100. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube

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