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

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