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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"

35422 results found.

  1. GRB 260101A: LCO detection of the optical counterpart
  2. GRB 260101A: Swift detection of a burst with an optical counterpart
  3. GRB 260101A: Fermi GBM Final Real-time Localization
  4. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  5. GRB 251230A: GRANDMA/TAROT Early Detection
  6. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  7. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  8. GRB 251230A: 1.3m DFOT optical upper limit
  9. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  10. GRB 251230A: Swift-XRT refined Analysis
  11. GRB 251231A: Fermi GBM Final Real-time Localization
  12. GRB 251222A: Mondy Optical Observations
  13. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  14. GRB 251230A: Swift/UVOT detection
  15. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  16. GRB 251230A: GOTO optical upper limit
  17. GRB 251230A / EP251230a: SVOM/VT optical observation
  18. GRB 251230A: Enhanced Swift-XRT position
  19. GRB 251230A: Early optical counterpart detection by LCO.
  20. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  21. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  22. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  23. Swift GRB 251230A: Global MASTER-Net observations report
  24. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  25. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  26. GRB 251226A: Glowbug gamma-ray detection
  27. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  28. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  29. Fermi GRB 251228A: Global MASTER-Net observations report
  30. GRB 251228A: Fermi GBM Final Real-time Localization
  31. GRB 251226A: SVOM/GRM observation
  32. GRB 251226A: GECAM-B detection
  33. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  34. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  35. GRB 251222A: NUTTelA-TAO Early Measurements
  36. GRB 251222A/EP251222b: Optical detection with Kinder observations
  37. GRB 251221A: Swift-BAT refined analysis
  38. GRB 251222A/EP251222b: FTW optical and NIR observations
  39. GRB 251205A: Kilonova-Catcher optical afterglow detection
  40. GRB 251222A: AbAO optical observations
  41. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  42. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  43. GRB 251222A: ZTSH BVRI optical observations
  44. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  45. GRB 251222A: Continued 1.3m DFOT optical observation
  46. GRB 251222A: Fermi GBM Observation
  47. EP251220a: CrAO ZTSh optical observations
  48. GRB 251222A / EP251222b: GECAM-B observation
  49. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  50. Konus-Wind detection of GRB 251222A / EP251222b
  51. GRB 251222A: Swift-XRT afterglow detection
  52. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  53. GRB 251222A / EP251222b: GOTO optical counterpart detection
  54. GRB 251222A / EP251222b: LCO optical observations
  55. GRB 251222A: 1.3m DFOT optical detection
  56. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  57. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  58. EP251222b/GRB 251222A: SVOM/GRM observation
  59. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  60. GRB 251222A: PRIME near-infrared detection
  61. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  62. GRB 251222A: NOT optical observations
  63. IPN triangulation of GRB 251220B (short)
  64. GRB 251222A: Swift ToO observations
  65. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  66. GRB 251222A: SVOM/VT optical candidate
  67. GRB 251222A: SVOM detection of a long burst
  68. GRB 251222A: Fermi GBM Final Real-time Localization
  69. GRB 251221A: PRIME near-infrared observation
  70. GRB 251221A: UAFO and Mondy optical upper limit
  71. GRB 251221A: Swift-XRT refined Analysis
  72. GRB 251221A: Swift/UVOT Upper Limits
  73. Fermi Gamma-ray Burst Monitor trigger 788028118/251221696 is not a GRB
  74. GRB 251221A: Enhanced Swift-XRT position
  75. GRB 251221A: Fermi GBM Observation
  76. GRB 251221B: Fermi GBM Final Real-time Localization
  77. GRB 251220B: SVOM/GRM observation of a short burst
  78. GRB 251221A: COLIBRÍ detection of the optical counterpart
  79. GRB 251221A: Swift detection of a burst
  80. GRB 251221A: Fermi GBM Final Real-time Localization
  81. GRB 251220B: Fermi GBM Final Real-time Localization
  82. GRB 251219A: SVOM/GRM observation of a short burst
  83. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  84. GRB 251220A: MAXI/GSC detection
  85. GRB 251215A: Swift-XRT afterglow detection
  86. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
  87. GRB 251214B: VIRT Optical Upper Limit
  88. Fermi GRB 251217A: Global MASTER-Net observations report
  89. GRB 251217A: Fermi GBM Final Real-time Localization
  90. GRB 251215A: Swift/UVOT Upper LImits
  91. GRB 251215A: Fermi GBM Observation
  92. Fermi GRB 251216A: Global MASTER-Net observations report
  93. GRB 251202A/EP251202a: Koshka optical upper limit
  94. GRB 251214B: Mondy optical upper limit
  95. GRB 251215A: COLIBRÍ optical upper limit
  96. GRB 251216A: Fermi GBM Final Real-time Localization
  97. EP251214b: KAIT optical upper limit
  98. GRB 251215A: Swift-XRT observations
  99. Fermi GRB 251215A: Global MASTER-Net observations report
  100. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras

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