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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"

27808 results found.

  1. GRB 251001A: AstroSat CZTI detection
  2. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  3. GRB 251003A: Swift-XRT refined Analysis
  4. GRB 251003A: COLIBRÍ photometric redshift
  5. GRB 251003A: GOTO detection of the optical counterpart
  6. LIGO/Virgo/KAGRA S251003at: Retraction of GW compact binary merger candidate
  7. GRB 251002A: GOTO detection of optical counterpart
  8. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  9. GRB 251003A: Enhanced Swift-XRT position
  10. GRB 251002A: AKO Early Optical Afterglow Detection
  11. GRB 251003A: GTC/OSIRIS+ spectroscopic redshift z = 4.412
  12. GRB 251003A: Kilonova-Catcher optical afterglow detection
  13. GRB 251002A: Swift-XRT afterglow detection
  14. GRB 251001B: AbAO optical upper limit
  15. GRB 251002A: Kilonova-Catcher optical afterglow detection
  16. GRB 251001C: CALET Gamma-Ray Burst Monitor detection
  17. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  18. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  19. GRB 251002A: EP-FXT counterpart detection
  20. GRB 251003A: LCOGT Optical Detection
  21. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  22. GRB 251003A: 1.5m OSN afterglow candidate
  23. GRB 251003A: Prompt enhanced Swift-XRT position
  24. GRB 251003A: Swift detection of a burst
  25. GRB 251003A: Fermi GBM Final Real-time Localization
  26. Swift GRB251003A: Global MASTER-Net observations report
  27. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  28. GRB 251002A: BOOTES-6 early optical detection
  29. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  30. GRB 251002A: FRAM-ORM afterglow detection
  31. GRB 251002A: SVOM detection of a burst
  32. GRB 251001B: Swift-BAT refined analysis
  33. GRB 251001A: Insight-HXMT detection
  34. GRB 251001B: Swift/UVOT Detection
  35. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  36. GRB 251001B: Swift-XRT refined Analysis
  37. GRB 251001B: SVOM/VT optical observation
  38. GRB 251001C: Glowbug gamma-ray detection
  39. Swift GRB 251001B: Global MASTER-Net observations report
  40. GRB 251001B: Fermi GBM Observation
  41. GRB 251001B: Further GOTO observations of optical counterpart.
  42. GRB 251001B: Enhanced Swift-XRT position
  43. GRB 250930A: Fermi GBM Final Localization
  44. GRB 251001B: LCOGT Optical Observations
  45. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  46. GRB 251001B: GOTO optical counterpart detection
  47. GRB 251001B: Swift detection of a burst
  48. GRB 251001B: Fermi GBM Final Real-time Localization
  49. GRB 251001A: Fermi GBM Detection
  50. GRB 251001A: Fermi GBM Final Real-time Localization
  51. GRB 250925A: MAO/AZT-22 optical observations
  52. GRB 250929A: Fermi GBM Final Real-time Localization
  53. GRB 250926A: CALET Gamma-Ray Burst Monitor detection
  54. GRB 250925A: Mondy I-band optical observations
  55. GRB 250924A: SVOM/GRM observation
  56. GRB 250925A: Swift-XRT refined Analysis
  57. GRB 250926A: Insight-HXMT detection
  58. GRB 250926B: Fermi GBM Final Localization
  59. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  60. GRB 250926A: AstroSat CZTI detection
  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. IceCube-250926A - IceCube observation of a high-energy neutrino candidate track-like event
  66. GRB 250925A/EP250925a: EP-WXT detection
  67. GRB 250925A : MITSuME Akeno optical upper limits
  68. GRB 250925A: JinShan optical observations
  69. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  70. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  71. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  72. GRB 250926A: Fermi GBM Final Real-time Localization
  73. GRB250925A: Liverpool Telescope optical observations
  74. GRB 250925A: Leavitt Observatory optical upper limit
  75. GRB 250925A: Enhanced Swift-XRT position
  76. GRB 250924A: Swift-BAT refined analysis
  77. GRB 250925A: GROWTH-India Telescope Upper Limits
  78. GRB 250925A: Swift detection of a burst
  79. Swift GRB 250925A: Global MASTER-Net observations report
  80. GRB 250924A: 1.6m Mephisto optical upper limits
  81. GRB 250924A: NOT optical observations
  82. GRB 250924A: AstroSat CZTI detection
  83. GRB 250914A: AstroSat CZTI detection
  84. GRB 250920B: AstroSat CZTI detection
  85. GRB 250924A: SVOM/VT optical observation
  86. GRB 250924A: Swift/UVOT Detection
  87. GRB 250924A: Swift-XRT refined Analysis
  88. GRB 250924A: Enhanced Swift-XRT position
  89. GRB 250924A: J-band detection with WINTER
  90. GRB 250924A: GROWTH-India Telescope Upper Limits
  91. GRB 250924A: KAIT optical observations
  92. GRB 250924A: Mondy optical observations, afterglow fading
  93. GRB 250924A: Kilonova-Catcher optical afterglow detection
  94. GRB 250920C: Kilonova-Catcher optical afterglow detection
  95. GRB 250920C: TRT optical observation
  96. GRB 250924B: Fermi GBM Final Localization
  97. GRB 250924A: COLIBRÍ optical observations
  98. Swift GRB 250924A: Global MASTER-Net observations report
  99. GRB 250924A: DDOTI Detection of the Optical Counterpart
  100. GRB 250924A: Swift detection of a burst with an optical counterpart

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