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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"

35441 results found.

  1. GRB 260102A: EP-FXT follow-up observation
  2. GRB 260102A: LCO optical upper limits
  3. GRB 260102A: Swift-XRT observations
  4. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  5. Fermi Gamma-ray Burst Monitor trigger 789047602/260102495 is not a GRB
  6. GRB 251230A / EP251230a: GECAM-B detection
  7. GRB 260102A: SVOM/VT optical counterpart
  8. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  9. GRB 260102A: Swift ToO observations
  10. GRB 260101A: Fermi GBM Observation
  11. GRB 260102A: SVOM detection of a burst
  12. GRB 260101A: GECAM-B detection
  13. GRB 260101A: NOT spectroscopic observations
  14. GRB 260101A: SVOM/GRM observation
  15. GRB 260101A: Swift-XRT refined Analysis
  16. Swift GRB 260101A: Global MASTER-Net observations report
  17. GRB 260101A: Enhanced Swift-XRT position
  18. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  19. GRB 260101A: LCO detection of the optical counterpart
  20. GRB 260101A: Swift detection of a burst with an optical counterpart
  21. GRB 260101A: Fermi GBM Final Real-time Localization
  22. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  23. GRB 251230A: GRANDMA/TAROT Early Detection
  24. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  25. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  26. GRB 251230A: 1.3m DFOT optical upper limit
  27. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  28. GRB 251230A: Swift-XRT refined Analysis
  29. GRB 251231A: Fermi GBM Final Real-time Localization
  30. GRB 251222A: Mondy Optical Observations
  31. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  32. GRB 251230A: Swift/UVOT detection
  33. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  34. GRB 251230A: GOTO optical upper limit
  35. GRB 251230A / EP251230a: SVOM/VT optical observation
  36. GRB 251230A: Enhanced Swift-XRT position
  37. GRB 251230A: Early optical counterpart detection by LCO.
  38. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  39. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  40. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  41. Swift GRB 251230A: Global MASTER-Net observations report
  42. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  43. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  44. GRB 251226A: Glowbug gamma-ray detection
  45. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  46. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  47. Fermi GRB 251228A: Global MASTER-Net observations report
  48. GRB 251228A: Fermi GBM Final Real-time Localization
  49. GRB 251226A: SVOM/GRM observation
  50. GRB 251226A: GECAM-B detection
  51. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  52. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  53. GRB 251222A: NUTTelA-TAO Early Measurements
  54. GRB 251222A/EP251222b: Optical detection with Kinder observations
  55. GRB 251221A: Swift-BAT refined analysis
  56. GRB 251222A/EP251222b: FTW optical and NIR observations
  57. GRB 251205A: Kilonova-Catcher optical afterglow detection
  58. GRB 251222A: AbAO optical observations
  59. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  60. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  61. GRB 251222A: ZTSH BVRI optical observations
  62. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  63. GRB 251222A: Continued 1.3m DFOT optical observation
  64. GRB 251222A: Fermi GBM Observation
  65. EP251220a: CrAO ZTSh optical observations
  66. GRB 251222A / EP251222b: GECAM-B observation
  67. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  68. Konus-Wind detection of GRB 251222A / EP251222b
  69. GRB 251222A: Swift-XRT afterglow detection
  70. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  71. GRB 251222A / EP251222b: GOTO optical counterpart detection
  72. GRB 251222A / EP251222b: LCO optical observations
  73. GRB 251222A: 1.3m DFOT optical detection
  74. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  75. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  76. EP251222b/GRB 251222A: SVOM/GRM observation
  77. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  78. GRB 251222A: PRIME near-infrared detection
  79. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  80. GRB 251222A: NOT optical observations
  81. IPN triangulation of GRB 251220B (short)
  82. GRB 251222A: Swift ToO observations
  83. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  84. GRB 251222A: SVOM/VT optical candidate
  85. GRB 251222A: SVOM detection of a long burst
  86. GRB 251222A: Fermi GBM Final Real-time Localization
  87. GRB 251221A: PRIME near-infrared observation
  88. GRB 251221A: UAFO and Mondy optical upper limit
  89. GRB 251221A: Swift-XRT refined Analysis
  90. GRB 251221A: Swift/UVOT Upper Limits
  91. Fermi Gamma-ray Burst Monitor trigger 788028118/251221696 is not a GRB
  92. GRB 251221A: Enhanced Swift-XRT position
  93. GRB 251221A: Fermi GBM Observation
  94. GRB 251221B: Fermi GBM Final Real-time Localization
  95. GRB 251220B: SVOM/GRM observation of a short burst
  96. GRB 251221A: COLIBRÍ detection of the optical counterpart
  97. GRB 251221A: Swift detection of a burst
  98. GRB 251221A: Fermi GBM Final Real-time Localization
  99. GRB 251220B: Fermi GBM Final Real-time Localization
  100. GRB 251219A: SVOM/GRM observation of a short burst

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