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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"

1520 results found.

  1. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  2. IceCube Alert 250421.71: Global MASTER-Net observations report
  3. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  4. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  5. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  6. IceCube-250416A: DDOTI Optical Observations
  7. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  8. IceCube-250416A: Global MASTER-Net observations report
  9. IceCube 250414.324: DDOTI Optical Observations
  10. IceCube-250406A: Swift-XRT observations
  11. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  12. Fermi-LAT gamma-ray observations of IceCube-250406A
  13. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  14. IceCube-250406A: No candidates from the Zwicky Transient Facility
  15. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  16. IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
  17. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  18. IceCube 250406.951: DDOTI Optical Observations
  19. IceCube Alert 250406.95: Global MASTER-Net observations report
  20. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  21. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  22. Fermi-LAT gamma-ray observations of IceCube-250330A
  23. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  24. IceCube Alert 250330.35: Global MASTER-Net observations report
  25. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  26. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  27. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  28. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  29. IceCube-250309A: Upper limits from Fermi-GBM Observations
  30. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  31. IPN triangulation of GRB 250309B
  32. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  33. GRB 250309B / IceCube-250309A: GECAM-B observations
  34. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  35. IceCube-250309A: No candidates from the Zwicky Transient Facility
  36. Fermi-LAT gamma-ray observations of IceCube-250309A
  37. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  38. GRB 230509B: Tiled Swift observations
  39. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  40. IceCube Alert 250309.32: Global MASTER-Net observations report
  41. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  42. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  43. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  44. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  45. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  46. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  47. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  48. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  49. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  50. IceCube-250207A: One candidate from the Zwicky Transient Facility
  51. IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
  52. IceCube Alert 250207.09: Global MASTER-Net observations report
  53. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  54. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  55. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  56. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  57. IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
  58. IceCube-250207A - IceCube observation of a high-energy neutrino candidate track-like event
  59. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  60. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  61. LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
  62. IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event
  63. EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
  64. Fermi-LAT Gamma-ray Observations of IceCube-250102A
  65. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  66. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  67. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  68. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  69. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  70. IceCube Alert 250102.58: Global MASTER-Net observations report
  71. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  72. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  73. IceCube-Cascade 241228A: Upper limits from a search for additional neutrino events in IceCube
  74. IceCube-241224A: No transient candidates from the Zwicky Transient Facility
  75. IceCube-241224A: Upper limits from a search for additional neutrino events in IceCube
  76. LIGO/Virgo/KAGRA S241225c: Two counterpart neutrino candidates from IceCube neutrino searches
  77. IceCube-241224A - IceCube observation of a high-energy neutrino candidate track-like event
  78. IceCube Alert 241224.30: Global MASTER-Net observations report
  79. IceCube-241127A: No transient candidates from the Zwicky Transient Facility
  80. IceCube-241127A: Upper limits from a search for additional neutrino events in IceCube
  81. Swift-XRT observations of IceCube -241127A
  82. Fermi-LAT gamma-ray observations of IceCube-241127A
  83. IceCube Alert 241127.59: Global MASTER-Net observations report
  84. IceCube-241127A: IceCube observation of a high-energy neutrino candidate track-like event
  85. LIGO/Virgo/KAGRA S241109bn: Upper limits from a two-week IceCube neutrino search
  86. Updates to IceCube realtime alert system for muon tracks
  87. IceCube-Cascade 241116A: Upper limits from a search for additional neutrino events in IceCube
  88. IceCube-241113A: Upper limits from a search for additional neutrino events in IceCube
  89. Fermi-LAT gamma-ray observations of IceCube-241113A
  90. IceCube-241113A - IceCube observation of a high-energy neutrino candidate track-like event
  91. IceCube Alert 241113.02: Global MASTER-Net observations report
  92. LIGO/Virgo/KAGRA S241110bk: 1 counterpart neutrino candidate event from an IceCube neutrino search
  93. LIGO/Virgo/KAGRA S241106ba: 1 counterpart neutrino candidate event from an IceCube neutrino search
  94. LIGO/Virgo/KAGRA S241102o: 1 counterpart neutrino candidate event from an IceCube neutrino search
  95. IceCube-Cascade 241019A: Upper limits from a search for additional neutrino events in IceCube
  96. IceCube alert 139977_2910365 retraction
  97. IceCube Alert 241016.04: Global MASTER-Net observations report
  98. IceCube-241006A: Upper limits from a search for additional neutrino events in IceCube
  99. Fermi-LAT Gamma-ray Observations of IceCube-241006A
  100. IceCube-241006A: No candidates from the Zwicky Transient Facility

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