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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"

19150 results found.

  1. GRB 251006A: CALET Gamma-Ray Burst Monitor detection
  2. GRB 251006A: Fermi GBM Observation
  3. GRB 251007A: 1.5m OSN and 2.2m CAHA optical follow-up
  4. GRB 251003A: Fermi GBM Observation
  5. GRB 251007B: COLIBRÍ optical upper limit
  6. GRB 251007A: AstroSat CZTI detection
  7. GRB 250917B: iTelescope T-26 upper limit
  8. GRB 251007A: Swift-XRT refined Analysis
  9. GRB 251007A: Enhanced Swift-XRT position
  10. GRB 251007B: Swift-XRT refined Analysis
  11. GRB 251007B: Enhanced Swift-XRT position
  12. GRB 251007A: AKO Optical Upper Limit
  13. GRB 251007A: CALET Gamma-Ray Burst Monitor detection
  14. GRB 251007A: SVOM/C-GFT optical observations
  15. GRB 251005C: PRIME J-band upper limit
  16. Swift GRB 251007B: Global MASTER-Net observations report
  17. GRB 251007A: Glowbug gamma-ray detection
  18. Swift GRB 251007A: Global MASTER-Net observations report
  19. GRB 251007B: SVOM detection of a faint burst
  20. GRB 251007B: Swift detection of a burst
  21. GRB 251007A: Swift detection of a burst with an optical counterpart
  22. GRB 251006A: Swift/BAT-GUANO subthreshold detection of a short burst
  23. GRB 251005C: SVOM/GRM observation of a likely short GRB
  24. GRB 251005C: COLIBRÍ optical observations
  25. GRB 251003A: LAST optical observations
  26. GRB 251005C: SVOM/VT optical candidate
  27. GRB 251005C: AstroSat CZTI detection
  28. GRB 251005​C: Swift/UVOT Upper Limits
  29. GRB 251005C: Swift-XRT refined Analysis
  30. GRB 251005C: Fermi GBM Observation
  31. Swift GRB 251005A: Global MASTER-Net observations report
  32. GRB 251005C: Enhanced Swift-XRT position
  33. GRB 251005C: GOTO optical upper limits
  34. GRB 251005C: Swift detection of a burst
  35. GRB 251003A: Swift-BAT refined analysis
  36. GRB 251003A: Swift/UVOT Upper Limits
  37. GRB 251002A: Swift/UVOT detection
  38. GRB 251003A: Swift-XRT refined Analysis
  39. GRB 251003A: COLIBRÍ photometric redshift
  40. GRB 251003A: Enhanced Swift-XRT position
  41. GRB 251003A: GTC/OSIRIS+ spectroscopic redshift z = 4.412
  42. GRB 251003A: Kilonova-Catcher optical afterglow detection
  43. GRB 251002A: Swift-XRT afterglow detection
  44. GRB 251001B: AbAO optical upper limit
  45. GRB 251003A: LCOGT Optical Detection
  46. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  47. GRB 251003A: 1.5m OSN afterglow candidate
  48. GRB 251003A: Prompt enhanced Swift-XRT position
  49. GRB 251003A: Swift detection of a burst
  50. Swift GRB251003A: Global MASTER-Net observations report
  51. GRB 251001B: Swift-BAT refined analysis
  52. GRB 251001B: Swift/UVOT Detection
  53. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  54. GRB 251001B: Swift-XRT refined Analysis
  55. GRB 251001B: SVOM/VT optical observation
  56. Swift GRB 251001B: Global MASTER-Net observations report
  57. GRB 251001B: Fermi GBM Observation
  58. GRB 251001B: Enhanced Swift-XRT position
  59. GRB 251001B: LCOGT Optical Observations
  60. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  61. GRB 251001B: GOTO optical counterpart detection
  62. GRB 251001B: Swift detection of a burst
  63. GRB 250925A: MAO/AZT-22 optical observations
  64. GRB 250925A: Mondy I-band optical observations
  65. GRB 250924A: SVOM/GRM observation
  66. GRB 250925A: Swift-XRT refined Analysis
  67. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  68. GRB 250925A: Swift/UVOT Upper Limits
  69. GRB 250925A: Swift-BAT refined analysis
  70. GRB 250925A: Mondy and AbAO optical observations
  71. GRB 250925A: COLIBRÍ photometric redshift
  72. GRB 250925A : MITSuME Akeno optical upper limits
  73. GRB 250925A: JinShan optical observations
  74. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  75. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  76. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  77. GRB250925A: Liverpool Telescope optical observations
  78. GRB 250925A: Leavitt Observatory optical upper limit
  79. GRB 250925A: Enhanced Swift-XRT position
  80. GRB 250924A: Swift-BAT refined analysis
  81. GRB 250925A: GROWTH-India Telescope Upper Limits
  82. GRB 250925A: Swift detection of a burst
  83. Swift GRB 250925A: Global MASTER-Net observations report
  84. GRB 250924A: 1.6m Mephisto optical upper limits
  85. GRB 250924A: NOT optical observations
  86. GRB 250924A: AstroSat CZTI detection
  87. GRB 250920B: AstroSat CZTI detection
  88. GRB 250924A: SVOM/VT optical observation
  89. GRB 250924A: Swift/UVOT Detection
  90. GRB 250924A: Swift-XRT refined Analysis
  91. GRB 250924A: Enhanced Swift-XRT position
  92. GRB 250924A: GROWTH-India Telescope Upper Limits
  93. GRB 250924A: KAIT optical observations
  94. GRB 250924A: Mondy optical observations, afterglow fading
  95. GRB 250924A: Kilonova-Catcher optical afterglow detection
  96. GRB 250920C: Kilonova-Catcher optical afterglow detection
  97. GRB 250920C: TRT optical observation
  98. GRB 250924A: COLIBRÍ optical observations
  99. Swift GRB 250924A: Global MASTER-Net observations report
  100. GRB 250924A: DDOTI Detection of the Optical Counterpart

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