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

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