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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: Swift-XRT refined Analysis
  2. Swift GRB 260101A: Global MASTER-Net observations report
  3. GRB 260101A: Enhanced Swift-XRT position
  4. EP260101a: Einstein Probe detection of an X-ray transient
  5. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  6. GRB 260101A: LCO detection of the optical counterpart
  7. GRB 260101A: Swift detection of a burst with an optical counterpart
  8. GRB 260101A: Fermi GBM Final Real-time Localization
  9. SVOM GRB251231.57: Global MASTER-Net observations report
  10. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  11. GRB 251230A: GRANDMA/TAROT Early Detection
  12. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  13. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  14. EP251229a: Optical upper limit with Kinder observations
  15. GRB 251230A: 1.3m DFOT optical upper limit
  16. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  17. GRB 251230A: Swift-XRT refined Analysis
  18. GRB 251231A: Fermi GBM Final Real-time Localization
  19. GRB 251222A: Mondy Optical Observations
  20. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  21. GRB 251230A: Swift/UVOT detection
  22. GRB251230A: 7DT optical upper limits
  23. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  24. EP251229a: BOOTES-2 early optical upper limit
  25. GRB 251230A: GOTO optical upper limit
  26. EP251229a: NOT optical upper limits
  27. GRB 251230A / EP251230a: SVOM/VT optical observation
  28. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  29. GRB 251230A: Enhanced Swift-XRT position
  30. GRB 251230A: Early optical counterpart detection by LCO.
  31. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  32. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  33. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  34. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  35. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  36. Swift GRB 251230A: Global MASTER-Net observations report
  37. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  38. EP251229a: Global MASTER-Net observations report
  39. EP251229a: Einstein Probe detection of an X-ray transient
  40. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  41. GRB 251226A: Glowbug gamma-ray detection
  42. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  43. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  44. Fermi GRB 251228A: Global MASTER-Net observations report
  45. The EP-WXT trigger 01709250662 is likely a flaring star
  46. GRB 251228A: Fermi GBM Final Real-time Localization
  47. GRB 251226A: SVOM/GRM observation
  48. GRB 251226A: GECAM-B detection
  49. SVOM GRB251227.07: Global MASTER-Net observations report
  50. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  51. The EP-WXT trigger 01709250617 is likely a flaring star
  52. IceCube Alert 251225.84: Global MASTER-Net observations report
  53. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  54. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  55. GRB 251222A: NUTTelA-TAO Early Measurements
  56. GRB 251222A/EP251222b: Optical detection with Kinder observations
  57. EP251222a: Optical upper limit with Kinder observations
  58. GRB 251221A: Swift-BAT refined analysis
  59. GRB 251222A/EP251222b: FTW optical and NIR observations
  60. EP251222a: FTW optical and NIR observations
  61. GRB 251205A: Kilonova-Catcher optical afterglow detection
  62. GRB 251222A: AbAO optical observations
  63. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  64. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  65. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  66. GRB 251222A: ZTSH BVRI optical observations
  67. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  68. GRB 251222A: Continued 1.3m DFOT optical observation
  69. EP251220a: 3.6m DOT optical afterglow detection
  70. GRB 251222A: Fermi GBM Observation
  71. EP251220a: CrAO ZTSh optical observations
  72. EP251221a: PRIME upper limit
  73. EP251222a: Global MASTER-Net observations report
  74. GRB 251222A / EP251222b: GECAM-B observation
  75. EP251221a: Liverpool Telescope upper limits
  76. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  77. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  78. Konus-Wind detection of GRB 251222A / EP251222b
  79. GRB 251222A: Swift-XRT afterglow detection
  80. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  81. EP251222a: NTT/ULTRACAM optical observations
  82. EP251222a: GOTO optical upper limit
  83. GRB 251222A / EP251222b: GOTO optical counterpart detection
  84. GRB 251222A / EP251222b: LCO optical observations
  85. GRB 251222A: 1.3m DFOT optical detection
  86. GRB251221A: 7DT optical upper limits
  87. EP251222a: GSP Optical Counterpart Detection
  88. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  89. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  90. EP251222b/GRB 251222A: SVOM/GRM observation
  91. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  92. EP251222a: Einstein Probe detection of an X-ray transient
  93. The EP-WXT trigger 01709250397 is likely a flaring star
  94. EP251221a: Global MASTER-Net observations report
  95. GRB 251222A: PRIME near-infrared detection
  96. EP251221a: NOT optical upper limit
  97. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  98. GRB 251222A: NOT optical observations
  99. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  100. IPN triangulation of GRB 251220B (short)

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