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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"

16079 results found.

  1. GRB 251103A: Swift/UVOT Detection
  2. GRB 251103A: SVOM/GRM observation
  3. GRB 251103A: Swift-XRT afterglow detection
  4. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  5. EP251102a: Einstein Probe detection of a fast X-ray transient
  6. GRB 251025B: OHP/T193 optical upper limit
  7. GRB 251103A: LCO optical observation
  8. EP251102.890: COLIBRÍ optical counterpart candidate
  9. GRB 251103A: GOTO optical afterglow detection
  10. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  11. GRB 251103A: NOT spectroscopic redshift z = 0.76
  12. GRB 251103A: BOOTES-2/TELMA optical afterglow
  13. GRB 251103A: LCO optical afterglow detection
  14. GRB 251103A: NOT optical afterglow candidate (duplicate submission)
  15. GRB 251103A: NOT optical afterglow candidate
  16. GRB 251103A: SVOM detection of a bright burst
  17. GRB 251025C: SVOM/GRM observation
  18. GRB 251028A: SVOM/GRM observation
  19. GRB 251026B: SOAR Classification of GOTO25jgl/SN2025absf as a Type Ia supernova
  20. GRB 251026B: LBT near-infrared observations
  21. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  22. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  23. GRB251026B: PRIME H-band upper limit
  24. GRB251025B: 3.6m DOT Optical Observations
  25. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  26. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  27. GRB 251023B: Swift-UVOT Upper Limits
  28. EP251027.145: COLIBRÍ optical upper limits
  29. GRB 251022A: SVOM/GRM observation
  30. GRB 251027A: LCO optical upper limit
  31. GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  32. GRB 251017A: Mondy AZT-33IK and Koshka Zeiss-1000 optical observations
  33. GRB 251023B / EP251023b: Mondy optical upper limit
  34. GRB 251017A: INASAN-Kislovodsk optical observations
  35. GRB 251026A: Mondy optical upper limit
  36. GRB 251025B: Mondy optical observations
  37. GRB 251025B: Kilonova-Catcher optical afterglow detection
  38. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  39. GRB 251026B: Tentative GOTO optical counterpart candidate
  40. EP251023a: Mondy optical observations
  41. GRB 251025B: MAO/AZT-22 optical observations
  42. GRB 251025B: OHP/T193 optical detection
  43. GRB 251025B: J-band detection with WINTER
  44. IceCube-251025A: DDOTI Optical Upper Limit
  45. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  46. GRB 251025B: SVOM/VT optical bump
  47. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  48. GRB 251023A: SVOM/GRM observation
  49. GRB 251025B: ULL-ASTRO-MASTER optical counterpart detection with IAC80 telescope at Teide Observatory
  50. GRB 251025B: GROWTH-India Telescope optical observations
  51. GRB 251024A: Swift/UVOT Upper Limits
  52. GRB 251025B: SVOM/VT optical observations with VHF data
  53. GRB 251025B: MASTER OT detection
  54. GRB 251025B: SVOM/C-GFT optical counterpart detection
  55. GRB 251025A (sb25102501): Likely a stellar flare by SVOM/VT
  56. GRB 251025A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  57. GRB 251025A: SVOM/VT VHF optical upper limit
  58. GRB 251024A: LCOGT Optical Afterglow Detection
  59. GRB 251022A: KAIT optical observations
  60. GRB 251023B / EP251023b: COLIBRÍ Confirmation of the Fading Nature of the Optical Candidate
  61. GRB 251022A: COLIBRÍ Further Multi-frequency Optical Observations
  62. EP251023a: MAO/AZT-22 optical observations
  63. GRB 251023B: OHP/T193 optical observations
  64. EP251023a: OHP/T193 optical observations
  65. EP251023b/GRB 251023B: JinShan optical observation
  66. GRB 251022A: Swift-XRT detection of GOTO25iym
  67. GRB 251022A: GROWTH-India Telescope optical observations
  68. EP251023a: GROWTH-India Telescope optical observations
  69. GRB 251022A: Swift/BAT-GUANO localization skymap of a burst
  70. EP251023a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at Teide Observatory
  71. GRB 251023B / EP#01709247298: COLIBRÍ optical counterpart candidate
  72. EP251023a: COLIBRÍ optical observations
  73. GRB 251013C: further SAO RAS optical observations
  74. EP251023a: Keck/LRIS spectroscopic redshift z=2.232
  75. GRB 251022A: COLIBRÍ optical observations
  76. GRB 251013C: ISON-Castelgrande observatory optical observations
  77. GRB 251022A: MASTER OT detection
  78. GRB 251022A: DDOTI Optical Detection
  79. EP251021b/GRB 251021A: SVOM/VT optical candidate
  80. EP251023a: NOT optical counterpart detection
  81. EP251023a: GSP Optical Counterpart Detection
  82. EP251023a: Einstein Probe detection of an X-ray transient
  83. EP/WXT 01709247295: GOTO optical afterglow candidate.
  84. GRB 251022A: GOTO optical counterpart detection
  85. EP251021b: BOOTES-7 optical upper limit
  86. GRB 251017A: COLIBRÍ optical observations of a late plateau
  87. IceCube-251018A: DDOTI Optical Upper Limit
  88. GRB 251018A: BOOTES-5 and BOOTES-7 early optical detections
  89. GRB 251016A: Swift/UVOT Detection
  90. GRB 251017A: VLT/MUSE spectroscopic redshift z = 4.327
  91. GRB 251016A: VLT/FORS2 Optical Observation
  92. GRB 251018A: MASTER OT detection
  93. GRB 251018A: TRT optical afterglow detection
  94. GRB 251018A: Swift detection of a burst with an optical counterpart
  95. GRB 251017A: SVOM/VT optical observation
  96. GRB 251013C: OHP/T193 third epoch optical observations and detected rebrightening
  97. GRB 251017A: J-band detection with WINTER
  98. GRB 251013C: Liverpool Telescope observations
  99. GRB 251013C: Leavitt Observatory optical photometry
  100. GRB 251017A: JinShan observations of the optical afterglow

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