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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"

6791 results found.

  1. GRB 251026B: Fermi GBM Observation
  2. GRB 251026A/EP251026a: EP-FXT follow-up observation
  3. GRB 251028B: Fermi/GBM observation
  4. GRB 251025B: Swift-XRT confirmation of fading
  5. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  6. Fermi-LAT Gamma-ray Observations of IceCube-251025A
  7. GRB 251023B: Swift-UVOT Upper Limits
  8. GRB 251027A: Swift-XRT observations
  9. GRB 251026A: Swift-XRT observations
  10. GRB 251025B: ULL-ASTRO-MASTER optical counterpart detection with IAC80 telescope at Teide Observatory
  11. GRB 251025B: Swift-XRT afterglow detection
  12. GRB 251024A: Swift-XRT refined Analysis
  13. GRB 251025B: SVOM/VT optical observations with VHF data
  14. GRB 251022A: Swift-XRT detection of GOTO25iym
  15. EP251023b: Global MASTER-Net observations report
  16. GRB 251022A: Fermi GBM Observation
  17. EP251023a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at Teide Observatory
  18. EP#01709247298: Swift-XRT counterpart detection
  19. GRB 251013C: further SAO RAS optical observations
  20. EP251023a: GSP Optical Counterpart Detection
  21. GRB 251022A: Fermi-LAT detection
  22. GRB 251016B: Fermi GBM Detection
  23. Fermi-LAT gamma-ray observations of IceCube-251018A
  24. GRB 251016A: Fermi GBM Observation
  25. GRB 251018A: Fermi GBM Observation
  26. GRB 251018A: Swift-XRT refined Analysis
  27. GRB 251016A: Swift-XRT afterglow detection
  28. GRB 251016A: Swift/UVOT Detection
  29. GRB 251017A: Swift-XRT refined Analysis
  30. GRB 251011A: Fermi GBM Observation
  31. sb25101602: Swift-XRT counterpart detection
  32. GRB 251014A: Swift-XRT observations
  33. Fermi-LAT Gamma-ray Observations of IceCube-251014A
  34. GRB 251013D: Swift/UVOT Observations
  35. GRB 251013C: Swift/UVOT Detection
  36. GRB 251013D: Swift-XRT observations
  37. GRB 251014B: Swift-XRT observations
  38. GRB 251014D: Swift-XRT afterglow detection
  39. GRB 251013D: Fermi GBM Observation
  40. GRB 251013C: Early and late-time optical counterpart detection by LCO
  41. GRB 251013C: Fermi GBM Observation
  42. GRB 251013C NUTTelA-TAO / BSTI Early Measurements
  43. GRB 251013C: ULL-ASTRO-MASTER detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  44. GRB 251014A: SAO RAS optical upper limit
  45. GRB 251014A: Fermi GBM Observation
  46. GRB 251013C: Swift-XRT counterpart detection
  47. GRB 251013C: SAO RAS optical observations
  48. GRB 251011B: Swift-XRT refined Analysis
  49. GRB 251011B: Fermi GBM Observation
  50. GRB 251006A: Fermi GBM Observation
  51. GRB 251003A: Fermi GBM Observation
  52. GRB 251006B: Fermi GBM Observation
  53. GRB 251006B/EP251006a: EP-FXT afterglow detection
  54. GRB 251007A: Swift-XRT refined Analysis
  55. GRB 251007B: Swift-XRT refined Analysis
  56. EP251003a: LCO and VST fading optical counterpart
  57. GRB 251006B/EP251006a: EP-FXT follow-up observation
  58. GRB 251005C: Swift-XRT refined Analysis
  59. GRB 251005C: Fermi GBM Observation
  60. GRB 251002A: Swift/UVOT detection
  61. GRB 251003A: Swift-XRT refined Analysis
  62. GRB 251002A: Fermi GBM Observation
  63. GRB 251002A: Swift-XRT afterglow detection
  64. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  65. GRB 251001B: Swift-XRT refined Analysis
  66. GRB 251001B: Fermi GBM Observation
  67. GRB 251001A: Fermi GBM Detection
  68. Fermi-LAT Gamma-ray Observations of IceCube-250926A
  69. GRB 250925A: Swift-XRT refined Analysis
  70. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  71. GRB 250925A: Swift/UVOT Upper Limits
  72. GRB 250925A: Optical Observations via Virtual Telescope Project, Italy
  73. GRB 250925A: GROWTH-India Telescope Upper Limits
  74. GRB 250924A: Swift-XRT refined Analysis
  75. Konus-Wind detection of GRB 250920C
  76. GRB 250920B: SAO RAS optical observations
  77. GRB 250920C: Swift-XRT refined Analysis
  78. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  79. GRB 250920B: Fermi GBM Observation
  80. GRB 250920A: Fermi GBM Detection
  81. GRB 250920C: Fermi GBM Observation
  82. GRB 250920B: Swift-XRT refined Analysis
  83. Konus-Wind detection of GRB 250919A
  84. GRB 250919A: Fermi GBM Observation
  85. GRB 250919A: Swift-XRT afterglow detection
  86. GRB 250919A: Fermi-LAT detection
  87. GRB 250916A: Fermi GBM Observation
  88. GRB 250917B: VLT/HAWK-I near-infrared observations
  89. GRB 250916A: Swift-XRT observations
  90. EP250916a: EP-FXT follow-up observation
  91. GRB 250916A: MAO/AZT-22 optical observations
  92. GRB 250916A: SAO RAS optical observations
  93. GRB 250917B: Fermi GBM Observation
  94. GRB 250917B: Swift-XRT observations
  95. GRB 250912A: Swift-XRT observations
  96. GRB 250912A: Fermi GBM Observation
  97. EP250911a: SAO RAS optical observations
  98. GRB 250911A: Swift-XRT refined Analysis
  99. EP250911a: Swift-XRT observations
  100. EP250911a: Optical detection with Kinder observations

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