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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"

1526 results found.

  1. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  2. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  3. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  4. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  5. Fermi-LAT gamma-ray observations of IceCube-250421A
  6. IceCube-250421A: DDOTI Detection of the LAST Candidate
  7. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  8. IceCube Alert 250421.71: Global MASTER-Net observations report
  9. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  10. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  11. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  12. IceCube-250416A: DDOTI Optical Observations
  13. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  14. IceCube-250416A: Global MASTER-Net observations report
  15. IceCube 250414.324: DDOTI Optical Observations
  16. IceCube-250406A: Swift-XRT observations
  17. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  18. Fermi-LAT gamma-ray observations of IceCube-250406A
  19. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  20. IceCube-250406A: No candidates from the Zwicky Transient Facility
  21. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  22. IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
  23. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  24. IceCube 250406.951: DDOTI Optical Observations
  25. IceCube Alert 250406.95: Global MASTER-Net observations report
  26. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  27. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  28. Fermi-LAT gamma-ray observations of IceCube-250330A
  29. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  30. IceCube Alert 250330.35: Global MASTER-Net observations report
  31. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  32. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  33. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  34. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  35. IceCube-250309A: Upper limits from Fermi-GBM Observations
  36. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  37. IPN triangulation of GRB 250309B
  38. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  39. GRB 250309B / IceCube-250309A: GECAM-B observations
  40. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  41. IceCube-250309A: No candidates from the Zwicky Transient Facility
  42. Fermi-LAT gamma-ray observations of IceCube-250309A
  43. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  44. GRB 230509B: Tiled Swift observations
  45. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  46. IceCube Alert 250309.32: Global MASTER-Net observations report
  47. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  48. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  49. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  50. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  51. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  52. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  53. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  54. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  55. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  56. IceCube-250207A: One candidate from the Zwicky Transient Facility
  57. IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
  58. IceCube Alert 250207.09: Global MASTER-Net observations report
  59. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  60. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  61. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  62. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  63. IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
  64. IceCube-250207A - IceCube observation of a high-energy neutrino candidate track-like event
  65. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  66. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  67. LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
  68. IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event
  69. EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
  70. Fermi-LAT Gamma-ray Observations of IceCube-250102A
  71. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  72. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  73. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  74. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  75. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  76. IceCube Alert 250102.58: Global MASTER-Net observations report
  77. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  78. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  79. IceCube-Cascade 241228A: Upper limits from a search for additional neutrino events in IceCube
  80. IceCube-241224A: No transient candidates from the Zwicky Transient Facility
  81. IceCube-241224A: Upper limits from a search for additional neutrino events in IceCube
  82. LIGO/Virgo/KAGRA S241225c: Two counterpart neutrino candidates from IceCube neutrino searches
  83. IceCube-241224A - IceCube observation of a high-energy neutrino candidate track-like event
  84. IceCube Alert 241224.30: Global MASTER-Net observations report
  85. IceCube-241127A: No transient candidates from the Zwicky Transient Facility
  86. IceCube-241127A: Upper limits from a search for additional neutrino events in IceCube
  87. Swift-XRT observations of IceCube -241127A
  88. Fermi-LAT gamma-ray observations of IceCube-241127A
  89. IceCube Alert 241127.59: Global MASTER-Net observations report
  90. IceCube-241127A: IceCube observation of a high-energy neutrino candidate track-like event
  91. LIGO/Virgo/KAGRA S241109bn: Upper limits from a two-week IceCube neutrino search
  92. Updates to IceCube realtime alert system for muon tracks
  93. IceCube-Cascade 241116A: Upper limits from a search for additional neutrino events in IceCube
  94. IceCube-241113A: Upper limits from a search for additional neutrino events in IceCube
  95. Fermi-LAT gamma-ray observations of IceCube-241113A
  96. IceCube-241113A - IceCube observation of a high-energy neutrino candidate track-like event
  97. IceCube Alert 241113.02: Global MASTER-Net observations report
  98. LIGO/Virgo/KAGRA S241110bk: 1 counterpart neutrino candidate event from an IceCube neutrino search
  99. LIGO/Virgo/KAGRA S241106ba: 1 counterpart neutrino candidate event from an IceCube neutrino search
  100. LIGO/Virgo/KAGRA S241102o: 1 counterpart neutrino candidate event from an IceCube neutrino search

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