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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"

36180 results found.

  1. GRB 260111A: Fermi GBM Final Real-time Localization
  2. EP260110a: KAIT optical upper limit
  3. GRB 260109C: LCO optical upper limits
  4. GRB 260109C: Kilonova-Catcher optical upper limit
  5. EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
  6. Swift Trigger 1434591: possible GRB 260109C
  7. GRB 260109B: Fermi GBM Final Real-time Localization
  8. GRB 260102A: Swift-XRT afterglow detection
  9. GRB 260109A: Fermi GBM Final Real-time Localization
  10. GRB 260104A: Swift-BAT refined analysis
  11. GRB 260101A: Swift-BAT refined analysis
  12. Swift GRB 251230A: Global MASTER-Net OT detection
  13. Fermi GRB 260107A: Global MASTER-Net observations report
  14. GRB 260102A: AbAO optical observations
  15. GRB 260107A: Fermi GBM Final Real-time Localization
  16. Fermi GRB 260105A: Global MASTER-Net observations report
  17. GRB 260105B: Fermi GBM Detection
  18. GRB 260105B: BALROG localization (Fermi Trigger 789348101 / GRB 260105973)
  19. GRB 260105A: SVOM/GRM observation
  20. GRB 260105B: SVOM/GRM observation
  21. Fermi GRB 260105B: Global MASTER-Net observations report
  22. GRB 260105B: Fermi GBM Final Real-time Localization
  23. GRB 260105A: Fermi GBM Final Real-time Localization
  24. GRB 260101A: COLIBRÍ optical upper limits
  25. GRB 260103A: Insight-HXMT/HE detection
  26. GRB 260104A: COLIBRÍ optical upper limits
  27. GRB 260104C: Fermi GBM Final Real-time Localization
  28. Fermi GRB 260104B: Global MASTER-Net observations report
  29. Swift GRB 260104A: Global MASTER-Net observations report
  30. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  31. GRB 260104A: Swift-XRT refined Analysis
  32. GRB 260104A: Enhanced Swift-XRT position
  33. GRB 260101A: Swift/UVOT Detection
  34. GRB 260103A: GECAM-B observation of a burst
  35. GRB 260104B: Fermi GBM Final Localization
  36. GRB 260104A: Swift detection of a burst
  37. GRB 260103A: SVOM/GRM observation of a possible GRB
  38. GRB 260101A: COLIBRÍ optical observations
  39. GRB 260102B: Fermi GBM Final Real-time Localization
  40. Fermi GBM Sub-Threshold Detection of GRB 260102A
  41. GRB 260102A: EP-FXT follow-up observation
  42. GRB 260102A: LCO optical upper limits
  43. GRB 260102A: Swift-XRT observations
  44. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  45. Fermi Gamma-ray Burst Monitor trigger 789047602/260102495 is not a GRB
  46. GRB 251230A / EP251230a: GECAM-B detection
  47. GRB 260102A: SVOM/VT optical counterpart
  48. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  49. GRB 260102A: Swift ToO observations
  50. GRB 260101A: Fermi GBM Observation
  51. GRB 260102A: SVOM detection of a burst
  52. GRB 260101A: GECAM-B detection
  53. GRB 260101A: NOT spectroscopic observations
  54. GRB 260101A: SVOM/GRM observation
  55. GRB 260101A: Swift-XRT refined Analysis
  56. Swift GRB 260101A: Global MASTER-Net observations report
  57. GRB 260101A: Enhanced Swift-XRT position
  58. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  59. GRB 260101A: LCO detection of the optical counterpart
  60. GRB 260101A: Swift detection of a burst with an optical counterpart
  61. GRB 260101A: Fermi GBM Final Real-time Localization
  62. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  63. GRB 251230A: GRANDMA/TAROT Early Detection
  64. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  65. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  66. GRB 251230A: 1.3m DFOT optical upper limit
  67. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  68. GRB 251230A: Swift-XRT refined Analysis
  69. GRB 251231A: Fermi GBM Final Real-time Localization
  70. GRB 251222A: Mondy Optical Observations
  71. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  72. GRB 251230A: Swift/UVOT detection
  73. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  74. GRB 251230A: GOTO optical upper limit
  75. GRB 251230A / EP251230a: SVOM/VT optical observation
  76. GRB 251230A: Enhanced Swift-XRT position
  77. GRB 251230A: Early optical counterpart detection by LCO.
  78. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  79. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  80. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  81. Swift GRB 251230A: Global MASTER-Net observations report
  82. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  83. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  84. GRB 251226A: Glowbug gamma-ray detection
  85. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  86. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  87. Fermi GRB 251228A: Global MASTER-Net observations report
  88. GRB 251228A: Fermi GBM Final Real-time Localization
  89. GRB 251226A: SVOM/GRM observation
  90. GRB 251226A: GECAM-B detection
  91. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  92. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  93. GRB 251222A: NUTTelA-TAO Early Measurements
  94. GRB 251222A/EP251222b: Optical detection with Kinder observations
  95. GRB 251221A: Swift-BAT refined analysis
  96. GRB 251222A/EP251222b: FTW optical and NIR observations
  97. GRB 251205A: Kilonova-Catcher optical afterglow detection
  98. GRB 251222A: AbAO optical observations
  99. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  100. GRB 251129A / EP251129a: VLA detection of a radio counterpart

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