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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').
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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

7396 results found.

  1. GRB 251117A: Tiled Swift observations
  2. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  3. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  4. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  5. GRB 251116C: Swift-XRT observations
  6. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  7. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  8. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  9. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  10. GRB 251115A: Tiled Swift observations
  11. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  12. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  13. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  14. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  15. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  16. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  17. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  18. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  19. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  20. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  21. Swift Trigger 1413695: a possible GRB 251112A
  22. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  23. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 3-Initial Localization Volume
  24. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  25. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  26. LIGO/Virgo/KAGRA S251108fi: One counterpart neutrino candidate from IceCube neutrino searches
  27. LIGO/Virgo/KAGRA S251108fi: Updated Sky localization
  28. LIGO/Virgo/KAGRA S251108dn: Updated Sky localization
  29. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  30. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  31. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  32. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  33. GRB 251106A: Swift-XRT afterglow detection
  34. Fermi GBM Sub-Threshold Detection of GRB 251106A
  35. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  36. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  37. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  38. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  39. GRB 251103B: Swift detection of a burst
  40. LIGO/Virgo/KAGRA S251031cq: Updated Sky localization
  41. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  42. EP251102.890: COLIBRÍ optical counterpart candidate
  43. GRB 251103A: LCO optical afterglow detection
  44. GRB 251103A: NOT optical afterglow candidate (duplicate submission)
  45. GRB 251103A: NOT optical afterglow candidate
  46. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  47. GRB 251026B: LBT near-infrared observations
  48. GRB251026B: PRIME H-band upper limit
  49. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  50. GRB 251027A: Swift-XRT observations
  51. GRB 251026B: Swift ToO observations
  52. GRB 251023B / EP251023b: Mondy optical upper limit
  53. GRB 251026B: Tentative GOTO optical counterpart candidate
  54. LIGO/Virgo/KAGRA S251026bn: Updated Sky localization
  55. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  56. GRB 251026A: Swift-XRT observations
  57. GRB 251026A: SVOM/C-GFT upper limit
  58. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  59. IceCube-251025A - IceCube observation of a high-energy neutrino candidate track-like event
  60. GRB 251025A: SVOM/VT VHF optical upper limit
  61. GRB 251024A: Swift detection of a burst
  62. GRB 251023B / EP251023b: COLIBRÍ Confirmation of the Fading Nature of the Optical Candidate
  63. GRB 251023B / EP#01709247298: COLIBRÍ optical counterpart candidate
  64. GRB 251022A: DDOTI Optical Detection
  65. EP251021b/GRB 251021A: SVOM/VT optical candidate
  66. EP/WXT 01709247295: GOTO optical afterglow candidate.
  67. GRB 251022A: Tiled Swift observations
  68. LIGO/Virgo/KAGRA S251021u: Updated Sky localization
  69. LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
  70. LIGO/Virgo/KAGRA S251018bi: Updated Sky localization
  71. LIGO/Virgo/KAGRA S251018bi: Identification of a GW compact binary merger candidate
  72. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event
  73. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  74. GRB 251018A: Swift detection of a burst with an optical counterpart
  75. LIGO/Virgo/KAGRA S251017di: Retraction of GW compact binary merger candidate
  76. GRB 251017A : MITSuME Akeno optical afterglow candidate detection
  77. GRB 251017A: Swift detection of a burst with an optical counterpart
  78. sb25101602: Swift-XRT counterpart detection
  79. LIGO/Virgo/KAGRA S251014cn: Updated Sky localization
  80. GRB 251013C: detection of a radio counterpart at 15.5GHz
  81. Swift Trigger 1404295: possible GRB 251015A
  82. IceCube-251014A - IceCube observation of a high-energy neutrino candidate track-like event
  83. GRB 251014B: Swift ToO observations
  84. LIGO/Virgo/KAGRA S251014cn: NED Galaxies in the 3-Initial Localization Volume
  85. GRB 251013D: Swift ToO observations
  86. LIGO/Virgo/KAGRA S251014cn: Identification of a GW compact binary merger candidate
  87. GRB 251013C: SVOM/VT optical observation
  88. LIGO/Virgo/KAGRA S251013x: Updated Sky localization and Source Classification
  89. LIGO/Virgo/KAGRA S251013x: Identification of a GW compact binary merger candidate
  90. IceCube alert 141456_888784 retraction
  91. GRB 251006B/EP251006a: EP-FXT afterglow detection
  92. GRB 251007B: SVOM/VT optical candidate
  93. GRB 251007B: SVOM/C-GFT upper limit
  94. GRB 251007B: Swift detection of a burst
  95. GRB 251007A: Swift detection of a burst with an optical counterpart
  96. GRB 251006B/EP251006a: SVOM/VT optical candidate
  97. GRB 251005C: SVOM/VT optical fading
  98. LIGO/Virgo/KAGRA S251006dd: Identification of a GW compact binary merger candidate
  99. GRB 251005C: VLT/X-shooter Imaging
  100. GRB 251005C: SVOM/VT optical candidate

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