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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"

7287 results found.

  1. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  2. EP260131a: COLIBRÍ observations of slow optical fading
  3. EP260131a: COLIBRÍ optical observations of the counterpart
  4. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  5. GRB 260127B: Swift-XRT observations
  6. EP260128a: NOT optical counterpart candidate
  7. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  8. GRB 260127A: COLIBRÍ optical observations
  9. GRB 260127B: Swift ToO observations
  10. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  11. GRB 260127B: GOTO candidate optical counterpart
  12. GRB 260127A: Swift detection of a burst
  13. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  14. GRB 260125A: Swift ToO observations
  15. GRB 260125A: GOTO candidate optical counterpart
  16. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  17. GRB 260114A: SVOM/VT optical upper limits
  18. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  19. GRB 260120B: COLIBRÍ optical upper limits
  20. GRB 260117A: Swift-XRT afterglow detection
  21. EP260119a: COLIBRÍ optical counterpart candidate
  22. GRB 260117A: SVOM/VT optical candidate
  23. GRB 260117A: SVOM/C-GFT upper limit
  24. GRB 260117A: Swift ToO observations
  25. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  26. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  27. GRB 260114A: GMG Optical Observation
  28. GRB 260114A: Swift detection of a short burst
  29. Swift Trigger 1439093: is probably not GRB 260113A
  30. GRB 260111A: COLIBRÍ optical afterglow candidate
  31. GRB 260111A: Swift ToO observations
  32. IceCube-260111A - IceCube observation of a high-energy neutrino candidate track-like event
  33. Swift trigger 1436759 is not an astrophysical event
  34. EP260110a: SVOM/C-GFT upper limit
  35. Swift Trigger 1434591: possible GRB 260109C
  36. GRB 260104A: Swift detection of a burst
  37. GRB 260102A: Swift ToO observations
  38. GRB 260101A: Swift detection of a burst with an optical counterpart
  39. GRB 251230A: GRANDMA/TAROT Early Detection
  40. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  41. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  42. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  43. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  44. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  45. GRB 251222A/EP251222b: Optical detection with Kinder observations
  46. EP251222a: Optical upper limit with Kinder observations
  47. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  48. GRB 251222A: Swift ToO observations
  49. GRB 251222A: SVOM/VT optical candidate
  50. EP251220a: PRIME upper limit
  51. GRB 251221A: Swift detection of a burst
  52. IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
  53. EP251214a: Optical upper limit with Kinder observations
  54. GRB 251215A: Swift ToO observations
  55. GRB 251214B: Swift detection of a burst with an optical counterpart
  56. IceCube-251210A: No Candidate Transients from the Zwicky Transient Facility
  57. IceCube-251210A - IceCube observation of a high-energy neutrino candidate track-like event
  58. GRB 251208B: COLIBRÍ optical upper limits
  59. GRB 251208D: Swift-XRT observations
  60. GRB 251208B: Swift ToO observations
  61. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  62. GRB 251205A: Swift detection of a burst with an optical afterglow
  63. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  64. GRB 251203C: LCO optical afterglow confirmation
  65. GRB 251203B: Swift-XRT observations
  66. GRB 251203B: SVOM/VT optical observation
  67. GRB 251201B: Swift detection of a burst with an optical counterpart
  68. EP251130a: JinShan optical observations
  69. IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
  70. EP251130a: Swift-XRT counterpart detection
  71. EP251130a: COLIBRÍ optical counterpart candidate
  72. GRB 251129A: Swift ToO observations
  73. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  74. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  75. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  76. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  77. EP251124a: Swift-XRT observations
  78. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  79. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  80. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  81. GRB 251122A / EP251122a: LCO optical upper limits
  82. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  83. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  84. EP251118a: Continued Optical Detection with Kinder observations
  85. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  86. EP251118a: Optical detection with Kinder observations
  87. EP251118a: NOT candidate optical counterpart
  88. GRB 251118A: Swift ToO observations
  89. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  90. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  91. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  92. GRB 251117A: Tiled Swift observations
  93. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  94. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  95. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  96. GRB 251116C: Swift-XRT observations
  97. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  98. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  99. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  100. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap

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