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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"

19546 results found.

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

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