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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"

1519 results found.

  1. IceCube Alert 250421.71: Global MASTER-Net observations report
  2. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  3. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  4. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  5. IceCube-250416A: DDOTI Optical Observations
  6. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  7. IceCube-250416A: Global MASTER-Net observations report
  8. IceCube 250414.324: DDOTI Optical Observations
  9. IceCube-250406A: Swift-XRT observations
  10. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  11. Fermi-LAT gamma-ray observations of IceCube-250406A
  12. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  13. IceCube-250406A: No candidates from the Zwicky Transient Facility
  14. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  15. IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
  16. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  17. IceCube 250406.951: DDOTI Optical Observations
  18. IceCube Alert 250406.95: Global MASTER-Net observations report
  19. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  20. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  21. Fermi-LAT gamma-ray observations of IceCube-250330A
  22. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  23. IceCube Alert 250330.35: Global MASTER-Net observations report
  24. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  25. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  26. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  27. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  28. IceCube-250309A: Upper limits from Fermi-GBM Observations
  29. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  30. IPN triangulation of GRB 250309B
  31. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  32. GRB 250309B / IceCube-250309A: GECAM-B observations
  33. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  34. IceCube-250309A: No candidates from the Zwicky Transient Facility
  35. Fermi-LAT gamma-ray observations of IceCube-250309A
  36. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  37. GRB 230509B: Tiled Swift observations
  38. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  39. IceCube Alert 250309.32: Global MASTER-Net observations report
  40. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  41. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  42. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  43. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  44. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  45. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  46. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  47. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  48. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  49. IceCube-250207A: One candidate from the Zwicky Transient Facility
  50. IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
  51. IceCube Alert 250207.09: Global MASTER-Net observations report
  52. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  53. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  54. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  55. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  56. IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
  57. IceCube-250207A - IceCube observation of a high-energy neutrino candidate track-like event
  58. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  59. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  60. LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
  61. IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event
  62. EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
  63. Fermi-LAT Gamma-ray Observations of IceCube-250102A
  64. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  65. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  66. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  67. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  68. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  69. IceCube Alert 250102.58: Global MASTER-Net observations report
  70. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  71. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  72. IceCube-Cascade 241228A: Upper limits from a search for additional neutrino events in IceCube
  73. IceCube-241224A: No transient candidates from the Zwicky Transient Facility
  74. IceCube-241224A: Upper limits from a search for additional neutrino events in IceCube
  75. LIGO/Virgo/KAGRA S241225c: Two counterpart neutrino candidates from IceCube neutrino searches
  76. IceCube-241224A - IceCube observation of a high-energy neutrino candidate track-like event
  77. IceCube Alert 241224.30: Global MASTER-Net observations report
  78. IceCube-241127A: No transient candidates from the Zwicky Transient Facility
  79. IceCube-241127A: Upper limits from a search for additional neutrino events in IceCube
  80. Swift-XRT observations of IceCube -241127A
  81. Fermi-LAT gamma-ray observations of IceCube-241127A
  82. IceCube Alert 241127.59: Global MASTER-Net observations report
  83. IceCube-241127A: IceCube observation of a high-energy neutrino candidate track-like event
  84. LIGO/Virgo/KAGRA S241109bn: Upper limits from a two-week IceCube neutrino search
  85. Updates to IceCube realtime alert system for muon tracks
  86. IceCube-Cascade 241116A: Upper limits from a search for additional neutrino events in IceCube
  87. IceCube-241113A: Upper limits from a search for additional neutrino events in IceCube
  88. Fermi-LAT gamma-ray observations of IceCube-241113A
  89. IceCube-241113A - IceCube observation of a high-energy neutrino candidate track-like event
  90. IceCube Alert 241113.02: Global MASTER-Net observations report
  91. LIGO/Virgo/KAGRA S241110bk: 1 counterpart neutrino candidate event from an IceCube neutrino search
  92. LIGO/Virgo/KAGRA S241106ba: 1 counterpart neutrino candidate event from an IceCube neutrino search
  93. LIGO/Virgo/KAGRA S241102o: 1 counterpart neutrino candidate event from an IceCube neutrino search
  94. IceCube-Cascade 241019A: Upper limits from a search for additional neutrino events in IceCube
  95. IceCube alert 139977_2910365 retraction
  96. IceCube Alert 241016.04: Global MASTER-Net observations report
  97. IceCube-241006A: Upper limits from a search for additional neutrino events in IceCube
  98. Fermi-LAT Gamma-ray Observations of IceCube-241006A
  99. IceCube-241006A: No candidates from the Zwicky Transient Facility
  100. Fermi-LAT Gamma-ray Observations of NuEm-240926A

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