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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: LCO optical upper limits
  2. GRB 260102A: Swift-XRT observations
  3. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  4. Fermi Gamma-ray Burst Monitor trigger 789047602/260102495 is not a GRB
  5. GRB 251230A / EP251230a: GECAM-B detection
  6. GRB 260102A: SVOM/VT optical counterpart
  7. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  8. GRB 260102A: Swift ToO observations
  9. GRB 260101A: Fermi GBM Observation
  10. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  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. EP260101a: Einstein Probe detection of an X-ray transient
  19. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  20. GRB 260101A: LCO detection of the optical counterpart
  21. GRB 260101A: Swift detection of a burst with an optical counterpart
  22. GRB 260101A: Fermi GBM Final Real-time Localization
  23. SVOM GRB251231.57: Global MASTER-Net observations report
  24. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  25. GRB 251230A: GRANDMA/TAROT Early Detection
  26. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  27. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  28. EP251229a: Optical upper limit with Kinder observations
  29. GRB 251230A: 1.3m DFOT optical upper limit
  30. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  31. GRB 251230A: Swift-XRT refined Analysis
  32. GRB 251231A: Fermi GBM Final Real-time Localization
  33. GRB 251222A: Mondy Optical Observations
  34. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  35. GRB 251230A: Swift/UVOT detection
  36. GRB251230A: 7DT optical upper limits
  37. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  38. EP251229a: BOOTES-2 early optical upper limit
  39. GRB 251230A: GOTO optical upper limit
  40. EP251229a: NOT optical upper limits
  41. GRB 251230A / EP251230a: SVOM/VT optical observation
  42. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  43. GRB 251230A: Enhanced Swift-XRT position
  44. GRB 251230A: Early optical counterpart detection by LCO.
  45. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  46. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  47. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  48. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  49. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  50. Swift GRB 251230A: Global MASTER-Net observations report
  51. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  52. EP251229a: Global MASTER-Net observations report
  53. EP251229a: Einstein Probe detection of an X-ray transient
  54. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  55. GRB 251226A: Glowbug gamma-ray detection
  56. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  57. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  58. Fermi GRB 251228A: Global MASTER-Net observations report
  59. The EP-WXT trigger 01709250662 is likely a flaring star
  60. GRB 251228A: Fermi GBM Final Real-time Localization
  61. GRB 251226A: SVOM/GRM observation
  62. GRB 251226A: GECAM-B detection
  63. SVOM GRB251227.07: Global MASTER-Net observations report
  64. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  65. The EP-WXT trigger 01709250617 is likely a flaring star
  66. IceCube Alert 251225.84: Global MASTER-Net observations report
  67. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  68. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  69. GRB 251222A: NUTTelA-TAO Early Measurements
  70. GRB 251222A/EP251222b: Optical detection with Kinder observations
  71. EP251222a: Optical upper limit with Kinder observations
  72. GRB 251221A: Swift-BAT refined analysis
  73. GRB 251222A/EP251222b: FTW optical and NIR observations
  74. EP251222a: FTW optical and NIR observations
  75. GRB 251205A: Kilonova-Catcher optical afterglow detection
  76. GRB 251222A: AbAO optical observations
  77. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  78. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  79. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  80. GRB 251222A: ZTSH BVRI optical observations
  81. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  82. GRB 251222A: Continued 1.3m DFOT optical observation
  83. EP251220a: 3.6m DOT optical afterglow detection
  84. GRB 251222A: Fermi GBM Observation
  85. EP251220a: CrAO ZTSh optical observations
  86. EP251221a: PRIME upper limit
  87. EP251222a: Global MASTER-Net observations report
  88. GRB 251222A / EP251222b: GECAM-B observation
  89. EP251221a: Liverpool Telescope upper limits
  90. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  91. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  92. Konus-Wind detection of GRB 251222A / EP251222b
  93. GRB 251222A: Swift-XRT afterglow detection
  94. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  95. EP251222a: NTT/ULTRACAM optical observations
  96. EP251222a: GOTO optical upper limit
  97. GRB 251222A / EP251222b: GOTO optical counterpart detection
  98. GRB 251222A / EP251222b: LCO optical observations
  99. GRB 251222A: 1.3m DFOT optical detection
  100. GRB251221A: 7DT optical upper limits

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