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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"

21791 results found.

  1. Fermi GBM Sub-Threshold Detection of GRB 251106A
  2. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  3. GRB 251106A: MASTER optical observations
  4. Fermi trigger No 784034269: Global MASTER-Net observations report
  5. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  6. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  7. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  8. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  9. Fermi GBM Sub-Threshold Detection of GRB 251105B
  10. GRB 251103B: Swift/UVOT Upper Limits
  11. Fermi GRB 251105A: Global MASTER-Net observations report
  12. EP251102a: FTW optical and NIR observations
  13. GRB 251103A: WFST optical observations
  14. EP251102a: OHP/T193 optical observations
  15. GRB 251103A: OHP/T193 optical observations
  16. GRB 251103A: KAIT optical observations
  17. GRB 251103B: Nanshan/HMT optical upper limit
  18. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  19. GRB 251103A: Swift/BAT-GUANO arcminute localization of a burst
  20. Fermi GRB 251103A: Global MASTER-Net observations report
  21. EP251102a: NIR observations with WINTER
  22. GRB 251103A: J-band detection with WINTER
  23. Swift GRB 251103B: Global MASTER-Net observations report
  24. GRB 251103A: Kilonova-Catcher optical afterglow detection
  25. GRB 251103A: Swift/UVOT Detection
  26. GRB 251103A: Swift-XRT afterglow detection
  27. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  28. GRB 251025B: OHP/T193 optical upper limit
  29. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  30. GRB 251103A: LCO optical observation
  31. EP251102.890: COLIBRÍ optical counterpart candidate
  32. GRB 251103A: GOTO optical afterglow detection
  33. GRB 251103A: NOT optical afterglow candidate
  34. Fermi GRB 251102A: Global MASTER-Net observations report
  35. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  36. IceCube-251025A: Two Transient Candidates from the Zwicky Transient Facility
  37. GRB 251026B: SOAR Classification of GOTO25jgl/SN2025absf as a Type Ia supernova
  38. GRB 251022A: Swift-XRT confirmation of fading
  39. GRB 251026B: LBT near-infrared observations
  40. GRB 251026A/EP251026a: EP-FXT follow-up observation
  41. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  42. Fermi GRB 251028B: Global MASTER-Net observations report
  43. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  44. GRB251026B: PRIME H-band upper limit
  45. GRB251025B: 3.6m DOT Optical Observations
  46. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  47. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  48. Fermi-LAT Gamma-ray Observations of IceCube-251025A
  49. GRB 251023B: Swift-UVOT Upper Limits
  50. GRB 251027A: Swift-XRT observations
  51. GRB 251026B: Swift ToO observations
  52. GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
  53. GRB 251017A: Mondy AZT-33IK and Koshka Zeiss-1000 optical observations
  54. GRB 251017A: INASAN-Kislovodsk optical observations
  55. GRB 251025B: Mondy optical observations
  56. GRB 251025B: Kilonova-Catcher optical afterglow detection
  57. GRB 251027A: SVOM detection of a faint burst
  58. GRB 251026B: Tentative GOTO optical counterpart candidate
  59. EP251023a: Mondy optical observations
  60. GRB 251025B: MAO/AZT-22 optical observations
  61. Fermi GRB 251026B: Global MASTER-Net observations report
  62. Fermi GRB 251025C: Global MASTER-Net observations report
  63. GRB 251026A: Swift-XRT observations
  64. GRB 251025B: OHP/T193 optical detection
  65. GRB 251025B: J-band detection with WINTER
  66. GRB 251026A: SVOM/C-GFT upper limit
  67. IceCube-251025A: DDOTI Optical Upper Limit
  68. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  69. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  70. GRB 251025B: ULL-ASTRO-MASTER optical counterpart detection with IAC80 telescope at Teide Observatory
  71. GRB 251025B: GROWTH-India Telescope optical observations
  72. GRB 251024A: Swift/UVOT Upper Limits
  73. GRB 251025B: Swift-XRT afterglow detection
  74. IceCube Alert 251025.57: Global MASTER-Net observations report
  75. GRB 251025A (sb25102501): stellar flare confirmed
  76. GRB 251025B: SVOM/VT optical observations with VHF data
  77. GRB 251025B: SVOM/C-GFT optical counterpart detection
  78. GRB 251003A: VLA Detection
  79. GRB 251022A: KAIT optical observations
  80. Swift GRB 251024A: Global MASTER-Net observations report
  81. GRB 251022A: COLIBRÍ Further Multi-frequency Optical Observations
  82. EP251023a: MAO/AZT-22 optical observations
  83. GRB 251023B: OHP/T193 optical observations
  84. EP251023a: OHP/T193 optical observations
  85. EP251023b/GRB 251023B: JinShan optical observation
  86. GRB 251022A: Swift-XRT detection of GOTO25iym
  87. EP251023b: Global MASTER-Net observations report
  88. GRB 251022A: GROWTH-India Telescope optical observations
  89. GRB 251023C: Swift/BAT-GUANO localization skymap of a burst
  90. EP251023a: GROWTH-India Telescope optical observations
  91. GRB 251022A: Swift/BAT-GUANO localization skymap of a burst
  92. EP251023a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at Teide Observatory
  93. EP251023a: Global MASTER-Net observations report
  94. GRB 251023B / EP#01709247298: COLIBRÍ optical counterpart candidate
  95. EP#01709247298: Swift-XRT counterpart detection
  96. EP251023a: COLIBRÍ optical observations
  97. GRB 251013C: further SAO RAS optical observations
  98. EP251023a: Keck/LRIS spectroscopic redshift z=2.232
  99. GRB 251022A: COLIBRÍ optical observations
  100. GRB 251013C: ISON-Castelgrande observatory optical observations

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