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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"

27777 results found.

  1. GRB 251025B: Swift-XRT confirmation of fading
  2. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  3. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  4. GRB 251025C: Glowbug gamma-ray detection
  5. GRB 251023B: Swift-UVOT Upper Limits
  6. Konus-Wind detection of GRB 251022A
  7. GRB 251027A: Swift-XRT observations
  8. GRB 251022A: SVOM/GRM observation
  9. GRB 251026B: Swift ToO observations
  10. GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
  11. GRB 251017A: Mondy AZT-33IK and Koshka Zeiss-1000 optical observations
  12. GRB 251017A: INASAN-Kislovodsk optical observations
  13. GRB 251025B: Kilonova-Catcher optical afterglow detection
  14. Konus-Wind detection of GRB 251016A (short/hard)
  15. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  16. GRB 251027A: SVOM detection of a faint burst
  17. GRB 251025C: AstroSat CZTI detection
  18. GRB 251025C: CALET Gamma-Ray Burst Monitor detection
  19. GRB 251026A: Swift-XRT observations
  20. GRB 251025B: OHP/T193 optical detection
  21. GRB 251025B: J-band detection with WINTER
  22. GRB 251026B: Fermi GBM Final Localization
  23. GRB 251026A: SVOM detection of a long burst
  24. GRB 251025B: SVOM/VT optical bump
  25. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  26. GRB 251025B: ULL-ASTRO-MASTER optical counterpart detection with IAC80 telescope at Teide Observatory
  27. GRB 251025C: Fermi GBM Final Real-time Localization
  28. Konus-Wind detection of GRB 251016B
  29. GRB 251024A: Swift/UVOT Upper Limits
  30. GRB 251025B: Swift-XRT afterglow detection
  31. GRB 251024A: Swift-BAT refined analysis
  32. GRB 251024A: Swift-XRT refined Analysis
  33. GRB 251025B: SVOM/VT optical observations with VHF data
  34. GRB 251025B: MASTER OT detection
  35. GRB 251025B: SVOM/C-GFT optical counterpart detection
  36. GRB 251025B: SVOM detection of a burst
  37. IceCube-251025A - IceCube observation of a high-energy neutrino candidate track-like event
  38. GRB 251025A: SVOM detection of a faint burst
  39. GRB 251003A: VLA Detection
  40. GRB 251024A: Enhanced Swift-XRT position
  41. GRB 251023C: Glowbug gamma-ray detection
  42. GRB 251024A: LCOGT Optical Afterglow Detection
  43. GRB 251024A: Swift detection of a burst
  44. Swift GRB 251024A: Global MASTER-Net observations report
  45. GRB 251023B / EP251023b: COLIBRÍ Confirmation of the Fading Nature of the Optical Candidate
  46. GRB 251022A: COLIBRÍ Further Multi-frequency Optical Observations
  47. GRB 251023C: AstroSat CZTI detection
  48. GRB 251022A: Swift-XRT detection of GOTO25iym
  49. EP251023b/GRB 251023B : Einstein Probe detection of a fast X-ray transient
  50. GRB 251023C: CALET Gamma-Ray Burst Monitor detection
  51. GRB 251023C: Swift/BAT-GUANO localization skymap of a burst
  52. GRB 251022A: Fermi GBM Observation
  53. GRB 251022A: Swift/BAT-GUANO localization skymap of a burst
  54. GRB 251023A: Glowbug gamma-ray detection
  55. GRB 251023B: Glowbug gamma-ray detection
  56. EP251023a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at Teide Observatory
  57. IPN triangulation of GRB 251016B
  58. GRB 251023B: CALET Gamma-Ray Burst Monitor detection
  59. EP#01709247298: Swift-XRT counterpart detection
  60. GRB 251022A: MASTER OT detection
  61. GRB 251022A: DDOTI Optical Detection
  62. GRB 251023B / MAXI J0451+122: MAXI/GSC detection
  63. EP251023a: NOT optical counterpart detection
  64. EP251023a: GSP Optical Counterpart Detection
  65. EP251023a: Einstein Probe detection of an X-ray transient
  66. GRB 251022A: GOTO optical counterpart detection
  67. GRB 251023A: Fermi GBM Final Localization Correction
  68. GRB 251022A: Fermi-LAT detection
  69. GRB 251016B: Fermi GBM Detection
  70. GRB 251022A: Tiled Swift observations
  71. GRB 251022A: Fermi GBM Final Real-time Localization
  72. GRB 251021A/EP251021b: Fermi-GBM Sub-Threshold Detection
  73. EP251021b: BOOTES-7 optical upper limit
  74. EP251021b: Einstein Probe detection of a fast X-ray transient
  75. GRB 250911A: MAXI/GSC detection
  76. GRB 251017A: COLIBRÍ optical observations of a late plateau
  77. GRB 251017A: Swift-BAT refined analysis
  78. GRB 251018A: Fermi GBM Observation
  79. GRB 251018A: BOOTES-5 and BOOTES-7 early optical detections
  80. GRB 251018A: Swift-XRT refined Analysis
  81. GRB 251018A: Enhanced Swift-XRT position
  82. GRB 251016A: HXMT/HE detection
  83. GRB 251016A: Swift-XRT afterglow detection
  84. GRB 251017A: Swift/UVOT Detection
  85. GRB 251016A: Swift/UVOT Detection
  86. GRB 251018A: Swift/UVOT Detection
  87. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event
  88. GRB 251016A: VLT/FORS2 Optical Observation
  89. GRB 251017A: COLIBRÍ photometric redshift
  90. GRB 251017A: Swift-XRT refined Analysis
  91. GRB 251018A: MASTER OT detection
  92. GRB 251018A: TRT optical afterglow detection
  93. Swift GRB 251018A: Global MASTER-Net observations report
  94. GRB 251018A: Swift detection of a burst with an optical counterpart
  95. GRB 251018A: Fermi GBM Final Real-time Localization
  96. GRB 251017A: SVOM/VT optical observation
  97. GRB 251011A: Fermi GBM Observation
  98. LIGO/Virgo/KAGRA S251017di: Retraction of GW compact binary merger candidate
  99. GRB 251017A: J-band detection with WINTER
  100. GRB 251017A: Glowbug gamma-ray detection

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