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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"
  1. GRB 260103A: SVOM/GRM observation of a possible GRB
  2. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  3. GRB 260101A: COLIBRÍ optical observations
  4. SVOM GRB260103.08: Global MASTER-Net observations report
  5. GRB 260102B: Fermi GBM Final Real-time Localization
  6. SVOM GRB260102A: Global MASTER-Net observations report
  7. Fermi GBM Sub-Threshold Detection of GRB 260102A
  8. GRB 260102A: EP-FXT follow-up observation
  9. EP260101a: Global MASTER-Net observations report
  10. GRB 260102A: LCO optical upper limits
  11. GRB 260102A: Swift-XRT observations
  12. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  13. Fermi Gamma-ray Burst Monitor trigger 789047602/260102495 is not a GRB
  14. GRB 251230A / EP251230a: GECAM-B detection
  15. GRB 260102A: SVOM/VT optical counterpart
  16. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  17. GRB 260102A: Swift ToO observations
  18. GRB 260101A: Fermi GBM Observation
  19. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  20. GRB 260102A: SVOM detection of a burst
  21. GRB 260101A: GECAM-B detection
  22. GRB 260101A: NOT spectroscopic observations
  23. GRB 260101A: SVOM/GRM observation
  24. GRB 260101A: Swift-XRT refined Analysis
  25. Swift GRB 260101A: Global MASTER-Net observations report
  26. GRB 260101A: Enhanced Swift-XRT position
  27. EP260101a: Einstein Probe detection of an X-ray transient
  28. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  29. GRB 260101A: LCO detection of the optical counterpart
  30. GRB 260101A: Swift detection of a burst with an optical counterpart
  31. GRB 260101A: Fermi GBM Final Real-time Localization
  32. SVOM GRB251231.57: Global MASTER-Net observations report
  33. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  34. GRB 251230A: GRANDMA/TAROT Early Detection
  35. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  36. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  37. EP251229a: Optical upper limit with Kinder observations
  38. GRB 251230A: 1.3m DFOT optical upper limit
  39. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  40. GRB 251230A: Swift-XRT refined Analysis
  41. GRB 251231A: Fermi GBM Final Real-time Localization
  42. GRB 251222A: Mondy Optical Observations
  43. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  44. GRB 251230A: Swift/UVOT detection
  45. GRB251230A: 7DT optical upper limits
  46. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  47. EP251229a: BOOTES-2 early optical upper limit
  48. GRB 251230A: GOTO optical upper limit
  49. EP251229a: NOT optical upper limits
  50. GRB 251230A / EP251230a: SVOM/VT optical observation
  51. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  52. GRB 251230A: Enhanced Swift-XRT position
  53. GRB 251230A: Early optical counterpart detection by LCO.
  54. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  55. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  56. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  57. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  58. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  59. Swift GRB 251230A: Global MASTER-Net observations report
  60. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  61. EP251229a: Global MASTER-Net observations report
  62. EP251229a: Einstein Probe detection of an X-ray transient
  63. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  64. GRB 251226A: Glowbug gamma-ray detection
  65. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  66. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  67. Fermi GRB 251228A: Global MASTER-Net observations report
  68. The EP-WXT trigger 01709250662 is likely a flaring star
  69. GRB 251228A: Fermi GBM Final Real-time Localization
  70. GRB 251226A: SVOM/GRM observation
  71. GRB 251226A: GECAM-B detection
  72. SVOM GRB251227.07: Global MASTER-Net observations report
  73. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  74. The EP-WXT trigger 01709250617 is likely a flaring star
  75. IceCube Alert 251225.84: Global MASTER-Net observations report
  76. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  77. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  78. GRB 251222A: NUTTelA-TAO Early Measurements
  79. GRB 251222A/EP251222b: Optical detection with Kinder observations
  80. EP251222a: Optical upper limit with Kinder observations
  81. GRB 251221A: Swift-BAT refined analysis
  82. GRB 251222A/EP251222b: FTW optical and NIR observations
  83. EP251222a: FTW optical and NIR observations
  84. GRB 251205A: Kilonova-Catcher optical afterglow detection
  85. GRB 251222A: AbAO optical observations
  86. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  87. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  88. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  89. GRB 251222A: ZTSH BVRI optical observations
  90. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  91. GRB 251222A: Continued 1.3m DFOT optical observation
  92. EP251220a: 3.6m DOT optical afterglow detection
  93. GRB 251222A: Fermi GBM Observation
  94. EP251220a: CrAO ZTSh optical observations
  95. EP251221a: PRIME upper limit
  96. EP251222a: Global MASTER-Net observations report
  97. GRB 251222A / EP251222b: GECAM-B observation
  98. EP251221a: Liverpool Telescope upper limits
  99. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  100. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations

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