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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: SVOM/COLIBRÍ (FM-GFT) optical observations
  2. Fermi Gamma-ray Burst Monitor trigger 789047602/260102495 is not a GRB
  3. GRB 251230A / EP251230a: GECAM-B detection
  4. GRB 260102A: SVOM/VT optical counterpart
  5. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  6. GRB 260102A: Swift ToO observations
  7. GRB 260101A: Fermi GBM Observation
  8. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  9. GRB 260102A: SVOM detection of a burst
  10. GRB 260101A: GECAM-B detection
  11. GRB 260101A: NOT spectroscopic observations
  12. GRB 260101A: SVOM/GRM observation
  13. GRB 260101A: Swift-XRT refined Analysis
  14. Swift GRB 260101A: Global MASTER-Net observations report
  15. GRB 260101A: Enhanced Swift-XRT position
  16. EP260101a: Einstein Probe detection of an X-ray transient
  17. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  18. GRB 260101A: LCO detection of the optical counterpart
  19. GRB 260101A: Swift detection of a burst with an optical counterpart
  20. GRB 260101A: Fermi GBM Final Real-time Localization
  21. SVOM GRB251231.57: Global MASTER-Net observations report
  22. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  23. GRB 251230A: GRANDMA/TAROT Early Detection
  24. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  25. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  26. EP251229a: Optical upper limit with Kinder observations
  27. GRB 251230A: 1.3m DFOT optical upper limit
  28. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  29. GRB 251230A: Swift-XRT refined Analysis
  30. GRB 251231A: Fermi GBM Final Real-time Localization
  31. GRB 251222A: Mondy Optical Observations
  32. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  33. GRB 251230A: Swift/UVOT detection
  34. GRB251230A: 7DT optical upper limits
  35. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  36. EP251229a: BOOTES-2 early optical upper limit
  37. GRB 251230A: GOTO optical upper limit
  38. EP251229a: NOT optical upper limits
  39. GRB 251230A / EP251230a: SVOM/VT optical observation
  40. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  41. GRB 251230A: Enhanced Swift-XRT position
  42. GRB 251230A: Early optical counterpart detection by LCO.
  43. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  44. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  45. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  46. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  47. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  48. Swift GRB 251230A: Global MASTER-Net observations report
  49. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  50. EP251229a: Global MASTER-Net observations report
  51. EP251229a: Einstein Probe detection of an X-ray transient
  52. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  53. GRB 251226A: Glowbug gamma-ray detection
  54. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  55. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  56. Fermi GRB 251228A: Global MASTER-Net observations report
  57. The EP-WXT trigger 01709250662 is likely a flaring star
  58. GRB 251228A: Fermi GBM Final Real-time Localization
  59. GRB 251226A: SVOM/GRM observation
  60. GRB 251226A: GECAM-B detection
  61. SVOM GRB251227.07: Global MASTER-Net observations report
  62. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  63. The EP-WXT trigger 01709250617 is likely a flaring star
  64. IceCube Alert 251225.84: Global MASTER-Net observations report
  65. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  66. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  67. GRB 251222A: NUTTelA-TAO Early Measurements
  68. GRB 251222A/EP251222b: Optical detection with Kinder observations
  69. EP251222a: Optical upper limit with Kinder observations
  70. GRB 251221A: Swift-BAT refined analysis
  71. GRB 251222A/EP251222b: FTW optical and NIR observations
  72. EP251222a: FTW optical and NIR observations
  73. GRB 251205A: Kilonova-Catcher optical afterglow detection
  74. GRB 251222A: AbAO optical observations
  75. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  76. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  77. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  78. GRB 251222A: ZTSH BVRI optical observations
  79. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  80. GRB 251222A: Continued 1.3m DFOT optical observation
  81. EP251220a: 3.6m DOT optical afterglow detection
  82. GRB 251222A: Fermi GBM Observation
  83. EP251220a: CrAO ZTSh optical observations
  84. EP251221a: PRIME upper limit
  85. EP251222a: Global MASTER-Net observations report
  86. GRB 251222A / EP251222b: GECAM-B observation
  87. EP251221a: Liverpool Telescope upper limits
  88. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  89. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  90. Konus-Wind detection of GRB 251222A / EP251222b
  91. GRB 251222A: Swift-XRT afterglow detection
  92. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  93. EP251222a: NTT/ULTRACAM optical observations
  94. EP251222a: GOTO optical upper limit
  95. GRB 251222A / EP251222b: GOTO optical counterpart detection
  96. GRB 251222A / EP251222b: LCO optical observations
  97. GRB 251222A: 1.3m DFOT optical detection
  98. GRB251221A: 7DT optical upper limits
  99. EP251222a: GSP Optical Counterpart Detection
  100. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171

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