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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 260102A: Swift-XRT observations
  2. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  3. Fermi Gamma-ray Burst Monitor trigger 789047602/260102495 is not a GRB
  4. GRB 251230A / EP251230a: GECAM-B detection
  5. GRB 260102A: SVOM/VT optical counterpart
  6. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  7. GRB 260102A: Swift ToO observations
  8. GRB 260101A: Fermi GBM Observation
  9. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  10. GRB 260102A: SVOM detection of a burst
  11. GRB 260101A: GECAM-B detection
  12. GRB 260101A: NOT spectroscopic observations
  13. GRB 260101A: SVOM/GRM observation
  14. GRB 260101A: Swift-XRT refined Analysis
  15. Swift GRB 260101A: Global MASTER-Net observations report
  16. GRB 260101A: Enhanced Swift-XRT position
  17. EP260101a: Einstein Probe detection of an X-ray transient
  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. SVOM GRB251231.57: Global MASTER-Net observations report
  23. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  24. GRB 251230A: GRANDMA/TAROT Early Detection
  25. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  26. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  27. EP251229a: Optical upper limit with Kinder observations
  28. GRB 251230A: 1.3m DFOT optical upper limit
  29. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  30. GRB 251230A: Swift-XRT refined Analysis
  31. GRB 251231A: Fermi GBM Final Real-time Localization
  32. GRB 251222A: Mondy Optical Observations
  33. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  34. GRB 251230A: Swift/UVOT detection
  35. GRB251230A: 7DT optical upper limits
  36. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  37. EP251229a: BOOTES-2 early optical upper limit
  38. GRB 251230A: GOTO optical upper limit
  39. EP251229a: NOT optical upper limits
  40. GRB 251230A / EP251230a: SVOM/VT optical observation
  41. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  42. GRB 251230A: Enhanced Swift-XRT position
  43. GRB 251230A: Early optical counterpart detection by LCO.
  44. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  45. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  46. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  47. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  48. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  49. Swift GRB 251230A: Global MASTER-Net observations report
  50. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  51. EP251229a: Global MASTER-Net observations report
  52. EP251229a: Einstein Probe detection of an X-ray transient
  53. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  54. GRB 251226A: Glowbug gamma-ray detection
  55. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  56. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  57. Fermi GRB 251228A: Global MASTER-Net observations report
  58. The EP-WXT trigger 01709250662 is likely a flaring star
  59. GRB 251228A: Fermi GBM Final Real-time Localization
  60. GRB 251226A: SVOM/GRM observation
  61. GRB 251226A: GECAM-B detection
  62. SVOM GRB251227.07: Global MASTER-Net observations report
  63. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  64. The EP-WXT trigger 01709250617 is likely a flaring star
  65. IceCube Alert 251225.84: Global MASTER-Net observations report
  66. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  67. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  68. GRB 251222A: NUTTelA-TAO Early Measurements
  69. GRB 251222A/EP251222b: Optical detection with Kinder observations
  70. EP251222a: Optical upper limit with Kinder observations
  71. GRB 251221A: Swift-BAT refined analysis
  72. GRB 251222A/EP251222b: FTW optical and NIR observations
  73. EP251222a: FTW optical and NIR observations
  74. GRB 251205A: Kilonova-Catcher optical afterglow detection
  75. GRB 251222A: AbAO optical observations
  76. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  77. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  78. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  79. GRB 251222A: ZTSH BVRI optical observations
  80. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  81. GRB 251222A: Continued 1.3m DFOT optical observation
  82. EP251220a: 3.6m DOT optical afterglow detection
  83. GRB 251222A: Fermi GBM Observation
  84. EP251220a: CrAO ZTSh optical observations
  85. EP251221a: PRIME upper limit
  86. EP251222a: Global MASTER-Net observations report
  87. GRB 251222A / EP251222b: GECAM-B observation
  88. EP251221a: Liverpool Telescope upper limits
  89. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  90. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  91. Konus-Wind detection of GRB 251222A / EP251222b
  92. GRB 251222A: Swift-XRT afterglow detection
  93. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  94. EP251222a: NTT/ULTRACAM optical observations
  95. EP251222a: GOTO optical upper limit
  96. GRB 251222A / EP251222b: GOTO optical counterpart detection
  97. GRB 251222A / EP251222b: LCO optical observations
  98. GRB 251222A: 1.3m DFOT optical detection
  99. GRB251221A: 7DT optical upper limits
  100. EP251222a: GSP Optical Counterpart Detection

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