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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 251222A: Mondy Optical Observations
  2. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  3. GRB 251230A: Swift/UVOT detection
  4. GRB251230A: 7DT optical upper limits
  5. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  6. EP251229a: BOOTES-2 early optical upper limit
  7. GRB 251230A: GOTO optical upper limit
  8. EP251229a: NOT optical upper limits
  9. GRB 251230A / EP251230a: SVOM/VT optical observation
  10. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  11. GRB 251230A: Enhanced Swift-XRT position
  12. GRB 251230A: Early optical counterpart detection by LCO.
  13. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  14. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  15. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  16. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  17. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  18. Swift GRB 251230A: Global MASTER-Net observations report
  19. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  20. EP251229a: Global MASTER-Net observations report
  21. EP251229a: Einstein Probe detection of an X-ray transient
  22. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  23. GRB 251226A: Glowbug gamma-ray detection
  24. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  25. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  26. Fermi GRB 251228A: Global MASTER-Net observations report
  27. The EP-WXT trigger 01709250662 is likely a flaring star
  28. GRB 251228A: Fermi GBM Final Real-time Localization
  29. GRB 251226A: SVOM/GRM observation
  30. GRB 251226A: GECAM-B detection
  31. SVOM GRB251227.07: Global MASTER-Net observations report
  32. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  33. The EP-WXT trigger 01709250617 is likely a flaring star
  34. IceCube Alert 251225.84: Global MASTER-Net observations report
  35. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  36. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  37. GRB 251222A: NUTTelA-TAO Early Measurements
  38. GRB 251222A/EP251222b: Optical detection with Kinder observations
  39. EP251222a: Optical upper limit with Kinder observations
  40. GRB 251221A: Swift-BAT refined analysis
  41. GRB 251222A/EP251222b: FTW optical and NIR observations
  42. EP251222a: FTW optical and NIR observations
  43. GRB 251205A: Kilonova-Catcher optical afterglow detection
  44. GRB 251222A: AbAO optical observations
  45. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  46. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  47. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  48. GRB 251222A: ZTSH BVRI optical observations
  49. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  50. GRB 251222A: Continued 1.3m DFOT optical observation
  51. EP251220a: 3.6m DOT optical afterglow detection
  52. GRB 251222A: Fermi GBM Observation
  53. EP251220a: CrAO ZTSh optical observations
  54. EP251221a: PRIME upper limit
  55. EP251222a: Global MASTER-Net observations report
  56. GRB 251222A / EP251222b: GECAM-B observation
  57. EP251221a: Liverpool Telescope upper limits
  58. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  59. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  60. Konus-Wind detection of GRB 251222A / EP251222b
  61. GRB 251222A: Swift-XRT afterglow detection
  62. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  63. EP251222a: NTT/ULTRACAM optical observations
  64. EP251222a: GOTO optical upper limit
  65. GRB 251222A / EP251222b: GOTO optical counterpart detection
  66. GRB 251222A / EP251222b: LCO optical observations
  67. GRB 251222A: 1.3m DFOT optical detection
  68. GRB251221A: 7DT optical upper limits
  69. EP251222a: GSP Optical Counterpart Detection
  70. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  71. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  72. EP251222b/GRB 251222A: SVOM/GRM observation
  73. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  74. EP251222a: Einstein Probe detection of an X-ray transient
  75. The EP-WXT trigger 01709250397 is likely a flaring star
  76. EP251221a: Global MASTER-Net observations report
  77. GRB 251222A: PRIME near-infrared detection
  78. EP251221a: NOT optical upper limit
  79. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  80. GRB 251222A: NOT optical observations
  81. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  82. IPN triangulation of GRB 251220B (short)
  83. GRB 251222A: Swift ToO observations
  84. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  85. GRB 251222A: SVOM/VT optical candidate
  86. GRB 251222A: SVOM detection of a long burst
  87. SVOM GRB251222A: Global MASTER-Net observations report
  88. GRB 251222A: Fermi GBM Final Real-time Localization
  89. EP251220a: PRIME upper limit
  90. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  91. GRB 251221A: PRIME near-infrared observation
  92. EP251220a: NOT optical observations
  93. EP251220a: FTW optical and NIR observations
  94. GRB 251221A: UAFO and Mondy optical upper limit
  95. GRB 251221A: Swift-XRT refined Analysis
  96. EP251221a: Einstein Probe detection of a fast X-ray transient
  97. GRB 251221A: Swift/UVOT Upper Limits
  98. Fermi Gamma-ray Burst Monitor trigger 788028118/251221696 is not a GRB
  99. GRB 251221A: Enhanced Swift-XRT position
  100. GRB 251221A: Fermi GBM Observation

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