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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"

11756 results found.

  1. GRB 251014D: Swift-XRT afterglow detection
  2. GRB 251014D: Swift detection of a burst
  3. GRB 251014C: Fermi GBM Final Localization
  4. GRB 251013C: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an bright optical counterpart
  5. GRB 251013D: LAST optical upper limit on Swift/BAT-GUANO localization
  6. LIGO/Virgo/KAGRA S251014cn: NED Galaxies in the 3-Initial Localization Volume
  7. GRB 251013C: ABObservatory optical observations
  8. GRB 251013C: J band observations by SYSU 80cm infrared telescope
  9. GRB 251013C: AstroSat CZTI detection
  10. Fermi GRB 251013C: Global MASTER-Net observations report
  11. GRB 251013C: Swift-XRT counterpart detection
  12. GRB 251013C: SAO RAS optical observations
  13. GRB 251013C: Optical Observations via Virtual Telescope Project, Italy
  14. GRB 251011B: Swift-XRT refined Analysis
  15. GRB 251011B : MASTER optical observations
  16. GRB 251011C: Fermi GBM Final Real-time Localization
  17. GRB 251010A: AstroSat CZTI detection
  18. GRB 251011A: AstroSat CZTI detection
  19. GRB 251011B: Swift detection of a burst
  20. SVOM/sb25101004: SVOM detection of a stellar flare
  21. GRB 251007A: 1.5m OSN and 2.2m CAHA optical follow-up
  22. IceCube Alert 251008A: Global MASTER-Net observations report
  23. GRB 251006B: Fermi GBM Observation
  24. GRB 251007A: AstroSat CZTI detection
  25. GRB 250917B: iTelescope T-26 upper limit
  26. EP250911a: Koshka Zeiss-1000 Optical Upper Limit
  27. GRB 251007A: Swift-XRT refined Analysis
  28. GRB 251006A: Swift/BAT-GUANO subthreshold detection of a short burst
  29. GRB 251006B/EP251006a: EP-WXT detection
  30. Fermi GRB 251006B: Global MASTER-Net observations report
  31. GRB 251006B: BALROG localization (Fermi Trigger 781473909 / GRB 251006837)
  32. GRB 251006B: Fermi GBM Final Real-time Localization
  33. GRB 251003A: LAST optical observations
  34. GRB 251002A: LAST optical observations
  35. GRB 251005C: AstroSat CZTI detection
  36. GRB 251002A: Fermi GBM Observation
  37. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  38. GRB 251002A: AKO Early Optical Afterglow Detection
  39. GRB 251003A: Kilonova-Catcher optical afterglow detection
  40. GRB 251002A: Swift-XRT afterglow detection
  41. GRB 251002A: Kilonova-Catcher optical afterglow detection
  42. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  43. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  44. GRB 251003A: Swift detection of a burst
  45. Swift GRB251003A: Global MASTER-Net observations report
  46. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  47. GRB 251002A: BOOTES-6 early optical detection
  48. GRB 251002A: SAO RAS optical observations
  49. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  50. GRB 251002A: FRAM-ORM afterglow detection
  51. Fermi GRB 251002A: Global MASTER-Net observations report
  52. GRB 251001B: Swift-BAT refined analysis
  53. GRB 251001B: Swift/UVOT Detection
  54. GRB 251001B: Swift-XRT refined Analysis
  55. GRB 250930A: Fermi GBM Final Localization
  56. GRB 251001B: Swift detection of a burst
  57. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  58. Fermi GRB 250929A: Global MASTER-Net observations report
  59. GRB 250929A: Fermi GBM Final Real-time Localization
  60. Fermi-LAT Gamma-ray Observations of IceCube-250926A
  61. GRB 250924A: SVOM/GRM observation
  62. IceCube-250926A: Upper limits from a search for additional neutrino events in IceCube
  63. Fermi trigger No 780609036: Global MASTER-Net observations report
  64. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  65. GRB 250926A: AstroSat CZTI detection
  66. GRB 250925A: Mondy and AbAO optical observations
  67. Fermi GRB 250926A: Global MASTER-Net observations report
  68. GRB250925A: Liverpool Telescope optical observations
  69. GRB 250924A: Swift-BAT refined analysis
  70. GRB 250925A: Swift detection of a burst
  71. GRB 250924A: SAO RAS optical observations
  72. GRB 250924A: AstroSat CZTI detection
  73. GRB 250914A: AstroSat CZTI detection
  74. GRB 250920B: AstroSat CZTI detection
  75. GRB 250920C: TRT optical observation
  76. Konus-Wind detection of GRB 250920C
  77. GRB 250920C: SALT redshift confirmation
  78. GRB 250922C: AstroSat CZTI detection of a short burst
  79. Fermi GRB 250922B: Global MASTER-Net observations report
  80. Fermi trigger No 780156732: Global MASTER-Net observations report
  81. Konus-Wind detection of GRB 250920B
  82. Konus-Wind detection of GRB 250920A
  83. Konus-Wind detection of GRB 250911A
  84. GRB 250920B: Glowbug gamma-ray detection
  85. GRB 250916A: CrAO ZTSh R-band optical observations
  86. GRB 250920C: Swift-XRT refined Analysis
  87. GRB 250920B: Kitab-ISON optical upper limit
  88. GRB 250920C: GROWTH-India Telescope optical observations
  89. GRB 250920B: Fermi GBM Observation
  90. GRB 250920A: Fermi GBM Detection
  91. GRB 250920C: Fermi GBM Observation
  92. Swift GRB 250920C: Global MASTER-Net observations report
  93. GRB 250920B: FTW optical and NIR observations of the counterpart
  94. GRB 250920C: Optical counterpart detection by LCO
  95. GRB250920C: LCOGT Optical Detection
  96. GRB 250920B: Swift-XRT refined Analysis
  97. GRB 250920B: SVOM/C-GFT optical observations
  98. GRB 250920C: GOTO optical counterpart candidate
  99. Konus-Wind detection of GRB 250919A
  100. GRB 250920C: Fermi GBM Final Real-time Localization

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