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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"

5810 results found.

  1. GRB 260204A: Swift-XRT observations
  2. EP260131a: SVOM/VT optical observation
  3. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  4. GRB 260131B: MAXI/GSC detection
  5. Fermi GRB 260127A: Global MASTER-Net observations report
  6. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  7. GRB 260127A: COLIBRÍ optical observations
  8. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  9. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  10. GRB 260122A: Fermi GBM Final Real-time Localization
  11. Fermi GRB 260120C: Global MASTER-Net observations report
  12. SVOM GRB260121.06: Global MASTER-Net observations report
  13. SVOM GRB260119.90: Global MASTER-Net observations report
  14. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  15. EP260119a: Global MASTER-Net observations report
  16. EP260119a: LCO optical observations
  17. EP260119a: COLIBRÍ optical counterpart candidate
  18. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  19. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  20. The EP-WXT trigger 01709251266 is likely a flaring star
  21. Swift trigger 1436759 is not an astrophysical event
  22. GRB 260109C: LCO optical upper limits
  23. Fermi GRB 260105A: Global MASTER-Net observations report
  24. EP260104a: FTW optical observations
  25. EP260104a: Global MASTER-Net observations report
  26. EP260105a: Global MASTER-Net observations report
  27. SVOM GRB260103.08: Global MASTER-Net observations report
  28. Fermi GBM Sub-Threshold Detection of GRB 260102A
  29. GRB 260102A: SVOM detection of a burst
  30. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  31. EP251229a: Global MASTER-Net observations report
  32. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  33. Fermi GRB 251228A: Global MASTER-Net observations report
  34. SVOM GRB251227.07: Global MASTER-Net observations report
  35. EP251222a: FTW optical and NIR observations
  36. EP251222a: Global MASTER-Net observations report
  37. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  38. EP 251220a: COLIBRÍ detection of the optical counterpart
  39. EP251220a: Global MASTER-Net observations report
  40. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  41. GRB 251220A: MAXI/GSC detection
  42. GRB 251216A: Fermi GBM Final Real-time Localization
  43. Fermi GRB 251215A: Global MASTER-Net observations report
  44. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  45. GRB 251214B: Swift-BAT refined analysis
  46. GRB 251214B: Fermi GBM Observation
  47. GRB 251214B: Swift/UVOT Detection
  48. GRB 251214B: Enhanced Swift-XRT position
  49. GRB 251214C: Fermi GBM Final Localization
  50. EP251214a: COLIBRÍ optical upper limit
  51. GRB 251214B: Swift detection of a burst with an optical counterpart
  52. GRB 251214B: Fermi GBM Final Real-time Localization
  53. Fermi GRB 251214A: Global MASTER-Net observations report
  54. EP251212a: KAIT optical upper limit
  55. EP251212a: EP-FXT follow-up observation
  56. GRB 251209A: NuSTAR detection of prompt emission
  57. IceCube-251210A: Upper limits from a search for additional neutrino events in IceCube
  58. GRB 251205A: 1.3m DFOT optical upper limit
  59. GRB 251209A: AstroSat CZTI detection
  60. GRB 251208A: AstroSat CZTI detection
  61. GRB 251208A: Glowbug gamma-ray detection
  62. GRB 251208B: COLIBRÍ optical upper limits
  63. Fermi GRB 251209A: Global MASTER-Net observations report
  64. Fermi GRB 251208C: Global MASTER-Net observations report
  65. GRB 251206A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  66. LAT GRB251208.43: Global MASTER-Net observations report
  67. GRB 251208A: Fermi GBM Final Real-time Localization
  68. EP-WXT trigger 01709249380: KAIT confirmation of a stellar flare
  69. GRB 251205A: Swift detection of a burst with an optical afterglow
  70. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  71. GRB 251129B: Glowbug gamma-ray detection of a short burst
  72. GRB 251203B: Swift-XRT observations
  73. GRB 251203B: SVOM/VT optical observation
  74. GRB 251203B: SVOM detection of a burst
  75. IPN triangulation of GRB 251129B (short/hard)
  76. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  77. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  78. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  79. GRB 251201B: Swift detection of a burst with an optical counterpart
  80. Fermi GRB 251130B: Global MASTER-Net observations report
  81. IceCube Alert 251130.75: Global MASTER-Net observations report
  82. EP251130a: COLIBRÍ optical counterpart candidate
  83. EP251129a/GRB 251129A: EP-FXT follow-up observations
  84. EP251129a: Global MASTER-Net observations report
  85. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  86. Fermi GRB 251125A: Global MASTER-Net observations report
  87. GRB 251122A / EP251122a: EP-FXT counterpart detection
  88. EP251118a: Continued Optical Detection with Kinder observations
  89. EP251118a: Global MASTER-Net observations report
  90. LAT GRB251118.86: Global MASTER-Net observations report
  91. GRB 251115A: Swift-XRT observations
  92. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  93. SVOM GRB251116C: Global MASTER-Net observations report
  94. Fermi GRB 251115A: Global MASTER-Net observations report
  95. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  96. GRB 251112A: Swift-BAT refined analysis
  97. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  98. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  99. Fermi Gamma-ray Burst Monitor trigger 784717756/251113381 is not a GRB
  100. GRB 251112A: Swift-XRT refined Analysis

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