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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"

7398 results found.

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

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