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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 260101A: Fermi GBM Observation
  2. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  3. GRB 260102A: SVOM detection of a burst
  4. GRB 260101A: GECAM-B detection
  5. GRB 260101A: NOT spectroscopic observations
  6. GRB 260101A: SVOM/GRM observation
  7. GRB 260101A: Swift-XRT refined Analysis
  8. Swift GRB 260101A: Global MASTER-Net observations report
  9. GRB 260101A: Enhanced Swift-XRT position
  10. EP260101a: Einstein Probe detection of an X-ray transient
  11. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  12. GRB 260101A: LCO detection of the optical counterpart
  13. GRB 260101A: Swift detection of a burst with an optical counterpart
  14. GRB 260101A: Fermi GBM Final Real-time Localization
  15. SVOM GRB251231.57: Global MASTER-Net observations report
  16. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  17. GRB 251230A: GRANDMA/TAROT Early Detection
  18. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  19. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  20. EP251229a: Optical upper limit with Kinder observations
  21. GRB 251230A: 1.3m DFOT optical upper limit
  22. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  23. GRB 251230A: Swift-XRT refined Analysis
  24. GRB 251231A: Fermi GBM Final Real-time Localization
  25. GRB 251222A: Mondy Optical Observations
  26. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  27. GRB 251230A: Swift/UVOT detection
  28. GRB251230A: 7DT optical upper limits
  29. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  30. EP251229a: BOOTES-2 early optical upper limit
  31. GRB 251230A: GOTO optical upper limit
  32. EP251229a: NOT optical upper limits
  33. GRB 251230A / EP251230a: SVOM/VT optical observation
  34. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  35. GRB 251230A: Enhanced Swift-XRT position
  36. GRB 251230A: Early optical counterpart detection by LCO.
  37. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  38. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  39. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  40. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  41. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  42. Swift GRB 251230A: Global MASTER-Net observations report
  43. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  44. EP251229a: Global MASTER-Net observations report
  45. EP251229a: Einstein Probe detection of an X-ray transient
  46. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  47. GRB 251226A: Glowbug gamma-ray detection
  48. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  49. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  50. Fermi GRB 251228A: Global MASTER-Net observations report
  51. The EP-WXT trigger 01709250662 is likely a flaring star
  52. GRB 251228A: Fermi GBM Final Real-time Localization
  53. GRB 251226A: SVOM/GRM observation
  54. GRB 251226A: GECAM-B detection
  55. SVOM GRB251227.07: Global MASTER-Net observations report
  56. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  57. The EP-WXT trigger 01709250617 is likely a flaring star
  58. IceCube Alert 251225.84: Global MASTER-Net observations report
  59. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  60. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  61. GRB 251222A: NUTTelA-TAO Early Measurements
  62. GRB 251222A/EP251222b: Optical detection with Kinder observations
  63. EP251222a: Optical upper limit with Kinder observations
  64. GRB 251221A: Swift-BAT refined analysis
  65. GRB 251222A/EP251222b: FTW optical and NIR observations
  66. EP251222a: FTW optical and NIR observations
  67. GRB 251205A: Kilonova-Catcher optical afterglow detection
  68. GRB 251222A: AbAO optical observations
  69. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  70. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  71. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  72. GRB 251222A: ZTSH BVRI optical observations
  73. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  74. GRB 251222A: Continued 1.3m DFOT optical observation
  75. EP251220a: 3.6m DOT optical afterglow detection
  76. GRB 251222A: Fermi GBM Observation
  77. EP251220a: CrAO ZTSh optical observations
  78. EP251221a: PRIME upper limit
  79. EP251222a: Global MASTER-Net observations report
  80. GRB 251222A / EP251222b: GECAM-B observation
  81. EP251221a: Liverpool Telescope upper limits
  82. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  83. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  84. Konus-Wind detection of GRB 251222A / EP251222b
  85. GRB 251222A: Swift-XRT afterglow detection
  86. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  87. EP251222a: NTT/ULTRACAM optical observations
  88. EP251222a: GOTO optical upper limit
  89. GRB 251222A / EP251222b: GOTO optical counterpart detection
  90. GRB 251222A / EP251222b: LCO optical observations
  91. GRB 251222A: 1.3m DFOT optical detection
  92. GRB251221A: 7DT optical upper limits
  93. EP251222a: GSP Optical Counterpart Detection
  94. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  95. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  96. EP251222b/GRB 251222A: SVOM/GRM observation
  97. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  98. EP251222a: Einstein Probe detection of an X-ray transient
  99. The EP-WXT trigger 01709250397 is likely a flaring star
  100. EP251221a: Global MASTER-Net observations report

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