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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"

36144 results found.

  1. GRB 251001B: Further GOTO observations of optical counterpart.
  2. GRB 251001B: Enhanced Swift-XRT position
  3. GRB 250930A: Fermi GBM Final Localization
  4. GRB 251001B: LCOGT Optical Observations
  5. GRB 250930A: SVOM/GRM observation
  6. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  7. GRB 251001B: GOTO optical counterpart detection
  8. GRB 251001B: Swift detection of a burst
  9. GRB 251001B: Fermi GBM Final Real-time Localization
  10. GRB 251001A: Fermi GBM Detection
  11. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  12. GRB 251001A: BALROG localization (Fermi Trigger 780979261 / GRB 251001112)
  13. GRB 251001A: Fermi GBM Final Real-time Localization
  14. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  15. GRB 250925A: MAO/AZT-22 optical observations
  16. Fermi GRB 250929A: Global MASTER-Net observations report
  17. GRB 250929A: Fermi GBM Final Real-time Localization
  18. GRB 250926A: CALET Gamma-Ray Burst Monitor detection
  19. GRB 250925A: Mondy I-band optical observations
  20. GRB 250916A: SVOM/VT optical observation
  21. GRB 250926A: triangulation location with Insight-HXMT/HE and Fermi/GBM
  22. GRB 250924A: SVOM/GRM observation
  23. GRB 250925A: Swift-XRT refined Analysis
  24. IceCube-250926A: Upper limits from a search for additional neutrino events in IceCube
  25. GRB 250926A: Insight-HXMT detection
  26. GRB 250926B: Fermi GBM Final Localization
  27. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  28. GRB 250926A: AstroSat CZTI detection
  29. GRB 250925A: Swift/UVOT Upper Limits
  30. GRB 250925A: Swift-BAT refined analysis
  31. GRB 250925A: Mondy and AbAO optical observations
  32. GRB 250925A: COLIBRÍ photometric redshift
  33. GRB 250925A: SVOM/GWAC-F60A upper limit
  34. GRB 250925A/EP250925a: EP-WXT detection
  35. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  36. GRB 250925A : MITSuME Akeno optical upper limits
  37. GRB 250925A: JinShan optical observations
  38. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  39. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  40. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  41. Fermi GRB 250926A: Global MASTER-Net observations report
  42. GRB 250926A: Fermi GBM Final Real-time Localization
  43. GRB 250925A: Optical Observations via Virtual Telescope Project, Italy
  44. GRB 250925A: NOT optical afterglow candidate
  45. GRB 250925A: Leavitt Observatory optical upper limit
  46. GRB 250925A: Enhanced Swift-XRT position
  47. GRB 250924A: Swift-BAT refined analysis
  48. GRB 250925A: GROWTH-India Telescope Upper Limits
  49. GRB 250925A: Swift detection of a burst
  50. Swift GRB 250925A: Global MASTER-Net observations report
  51. GRB 250922A: SVOM/GRM observation
  52. GRB 250924A: 1.6m Mephisto optical upper limits
  53. GRB 250924A: SAO RAS optical observations
  54. GRB 250924A: NOT optical observations
  55. GRB 250924A: AstroSat CZTI detection
  56. GRB 250914A: AstroSat CZTI detection
  57. GRB 250920B: AstroSat CZTI detection
  58. GRB 250924A: SVOM/VT optical observation
  59. GRB 250924A: Swift/UVOT Detection
  60. GRB 250924A: Swift-XRT refined Analysis
  61. GRB 250924A: Enhanced Swift-XRT position
  62. GRB 250924A: J-band detection with WINTER
  63. GRB 250924A: GROWTH-India Telescope Upper Limits
  64. GRB 250924A: KAIT optical observations
  65. GRB 250924A: Mondy optical observations, afterglow fading
  66. GRB 250924A: Kilonova-Catcher optical afterglow detection
  67. GRB 250920C: Kilonova-Catcher optical afterglow detection
  68. GRB 250922B: SVOM/GRM observation
  69. GRB 250920C: TRT optical observation
  70. GRB 250924B: Fermi GBM Final Localization
  71. GRB 250924A: COLIBRÍ optical observations
  72. Swift GRB 250924A: Global MASTER-Net observations report
  73. GRB 250919A / EP250919a: further LCO optical observation
  74. GRB 250924A: DDOTI Detection of the Optical Counterpart
  75. GRB 250924A: Swift detection of a burst with an optical counterpart
  76. GRB 250920B: AbAO optical upper limits
  77. Konus-Wind detection of GRB 250920C
  78. GRB 250920C: KAIT optical observations
  79. GRB 250920C: VLT redshift confirmation z = 1.399
  80. GRB 250920B: CrAO ZTSH optical observations
  81. GRB 250920C: SALT redshift confirmation
  82. GRB 250920C: COLIBRÍ optical observations
  83. GRB 250922C: AstroSat CZTI detection of a short burst
  84. Fermi GRB 250922B: Global MASTER-Net observations report
  85. GRB 250920B: SAO RAS optical observations
  86. GRB 250920C: NIR observations with WINTER
  87. GRB 250920B: NIR observations with WINTER
  88. GRB 250922B: Fermi GBM Final Real-time Localization
  89. GRB 250920C: PRIME near-infrared detection
  90. Konus-Wind detection of GRB 250920B
  91. Konus-Wind detection of GRB 250920A
  92. IPN triangulation of GRB 250920A (long/bright)
  93. Konus-Wind detection of GRB 250911A
  94. GRB 250916A: Swift/UVOT Detection
  95. GRB 250920B: Glowbug gamma-ray detection
  96. GRB 250916A: CrAO ZTSh R-band optical observations
  97. GRB 250920C: Swift-XRT refined Analysis
  98. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  99. GRB 250922A: Fermi GBM Final Localization
  100. GRB 250920B: Asiago optical observations

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