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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: OSIRIS+ redshift z = 2.623 for the new year burst
  2. GRB 260101A: LCO detection of the optical counterpart
  3. GRB 260101A: Swift detection of a burst with an optical counterpart
  4. GRB 260101A: Fermi GBM Final Real-time Localization
  5. SVOM GRB251231.57: Global MASTER-Net observations report
  6. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  7. GRB 251230A: GRANDMA/TAROT Early Detection
  8. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  9. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  10. EP251229a: Optical upper limit with Kinder observations
  11. GRB 251230A: 1.3m DFOT optical upper limit
  12. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  13. GRB 251230A: Swift-XRT refined Analysis
  14. GRB 251231A: Fermi GBM Final Real-time Localization
  15. GRB 251222A: Mondy Optical Observations
  16. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  17. GRB 251230A: Swift/UVOT detection
  18. GRB251230A: 7DT optical upper limits
  19. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  20. EP251229a: BOOTES-2 early optical upper limit
  21. GRB 251230A: GOTO optical upper limit
  22. EP251229a: NOT optical upper limits
  23. GRB 251230A / EP251230a: SVOM/VT optical observation
  24. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  25. GRB 251230A: Enhanced Swift-XRT position
  26. GRB 251230A: Early optical counterpart detection by LCO.
  27. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  28. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  29. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  30. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  31. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  32. Swift GRB 251230A: Global MASTER-Net observations report
  33. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  34. EP251229a: Global MASTER-Net observations report
  35. EP251229a: Einstein Probe detection of an X-ray transient
  36. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  37. GRB 251226A: Glowbug gamma-ray detection
  38. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  39. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  40. Fermi GRB 251228A: Global MASTER-Net observations report
  41. The EP-WXT trigger 01709250662 is likely a flaring star
  42. GRB 251228A: Fermi GBM Final Real-time Localization
  43. GRB 251226A: SVOM/GRM observation
  44. GRB 251226A: GECAM-B detection
  45. SVOM GRB251227.07: Global MASTER-Net observations report
  46. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  47. The EP-WXT trigger 01709250617 is likely a flaring star
  48. IceCube Alert 251225.84: Global MASTER-Net observations report
  49. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  50. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  51. GRB 251222A: NUTTelA-TAO Early Measurements
  52. GRB 251222A/EP251222b: Optical detection with Kinder observations
  53. EP251222a: Optical upper limit with Kinder observations
  54. GRB 251221A: Swift-BAT refined analysis
  55. GRB 251222A/EP251222b: FTW optical and NIR observations
  56. EP251222a: FTW optical and NIR observations
  57. GRB 251205A: Kilonova-Catcher optical afterglow detection
  58. GRB 251222A: AbAO optical observations
  59. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  60. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  61. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  62. GRB 251222A: ZTSH BVRI optical observations
  63. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  64. GRB 251222A: Continued 1.3m DFOT optical observation
  65. EP251220a: 3.6m DOT optical afterglow detection
  66. GRB 251222A: Fermi GBM Observation
  67. EP251220a: CrAO ZTSh optical observations
  68. EP251221a: PRIME upper limit
  69. EP251222a: Global MASTER-Net observations report
  70. GRB 251222A / EP251222b: GECAM-B observation
  71. EP251221a: Liverpool Telescope upper limits
  72. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  73. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  74. Konus-Wind detection of GRB 251222A / EP251222b
  75. GRB 251222A: Swift-XRT afterglow detection
  76. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  77. EP251222a: NTT/ULTRACAM optical observations
  78. EP251222a: GOTO optical upper limit
  79. GRB 251222A / EP251222b: GOTO optical counterpart detection
  80. GRB 251222A / EP251222b: LCO optical observations
  81. GRB 251222A: 1.3m DFOT optical detection
  82. GRB251221A: 7DT optical upper limits
  83. EP251222a: GSP Optical Counterpart Detection
  84. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  85. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  86. EP251222b/GRB 251222A: SVOM/GRM observation
  87. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  88. EP251222a: Einstein Probe detection of an X-ray transient
  89. The EP-WXT trigger 01709250397 is likely a flaring star
  90. EP251221a: Global MASTER-Net observations report
  91. GRB 251222A: PRIME near-infrared detection
  92. EP251221a: NOT optical upper limit
  93. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  94. GRB 251222A: NOT optical observations
  95. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  96. IPN triangulation of GRB 251220B (short)
  97. GRB 251222A: Swift ToO observations
  98. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  99. GRB 251222A: SVOM/VT optical candidate
  100. GRB 251222A: SVOM detection of a long burst

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