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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"
  1. GRB 250925A: GROWTH-India Telescope Upper Limits
  2. GRB 250925A: Swift detection of a burst
  3. Swift GRB 250925A: Global MASTER-Net observations report
  4. GRB 250922A: SVOM/GRM observation
  5. GRB 250924A: 1.6m Mephisto optical upper limits
  6. GRB 250924A: SAO RAS optical observations
  7. GRB 250924A: NOT optical observations
  8. GRB 250924A: AstroSat CZTI detection
  9. GRB 250914A: AstroSat CZTI detection
  10. GRB 250920B: AstroSat CZTI detection
  11. GRB 250924A: SVOM/VT optical observation
  12. GRB 250924A: Swift/UVOT Detection
  13. GRB 250924A: Swift-XRT refined Analysis
  14. GRB 250924A: Enhanced Swift-XRT position
  15. GRB 250924A: J-band detection with WINTER
  16. GRB 250924A: GROWTH-India Telescope Upper Limits
  17. GRB 250924A: KAIT optical observations
  18. GRB 250924A: Mondy optical observations, afterglow fading
  19. GRB 250924A: Kilonova-Catcher optical afterglow detection
  20. GRB 250920C: Kilonova-Catcher optical afterglow detection
  21. GRB 250922B: SVOM/GRM observation
  22. GRB 250920C: TRT optical observation
  23. GRB 250924B: Fermi GBM Final Localization
  24. GRB 250924A: COLIBRÍ optical observations
  25. Swift GRB 250924A: Global MASTER-Net observations report
  26. GRB 250919A / EP250919a: further LCO optical observation
  27. GRB 250924A: DDOTI Detection of the Optical Counterpart
  28. GRB 250924A: Swift detection of a burst with an optical counterpart
  29. GRB 250920B: AbAO optical upper limits
  30. Konus-Wind detection of GRB 250920C
  31. GRB 250920C: KAIT optical observations
  32. GRB 250920C: VLT redshift confirmation z = 1.399
  33. EP250911a: e-MERLIN radio observations
  34. GRB 250920B: CrAO ZTSH optical observations
  35. GRB 250920C: SALT redshift confirmation
  36. GRB 250920C: COLIBRÍ optical observations
  37. GRB 250922C: AstroSat CZTI detection of a short burst
  38. Fermi GRB 250922B: Global MASTER-Net observations report
  39. GRB 250920B: SAO RAS optical observations
  40. GRB 250920C: NIR observations with WINTER
  41. GRB 250920B: NIR observations with WINTER
  42. Fermi trigger No 780156732: Global MASTER-Net observations report
  43. GRB 250922B: Fermi GBM Final Real-time Localization
  44. GRB 250920C: PRIME near-infrared detection
  45. Konus-Wind detection of GRB 250920B
  46. Konus-Wind detection of GRB 250920A
  47. IPN triangulation of GRB 250920A (long/bright)
  48. Konus-Wind detection of GRB 250911A
  49. GRB 250916A: Swift/UVOT Detection
  50. GRB 250920B: Glowbug gamma-ray detection
  51. GRB 250916A: CrAO ZTSh R-band optical observations
  52. GRB 250920C: Swift-XRT refined Analysis
  53. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  54. GRB 250922A: Fermi GBM Final Localization
  55. GRB 250920B: Asiago optical observations
  56. GRB 250920B: Kitab-ISON optical upper limit
  57. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  58. GRB 250920C: SVOM/GRM observation
  59. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  60. GRB 250917B: KAIT optical upper limit
  61. GRB 250920A: NuSTAR detection of bright prompt emission
  62. GRB 250920C: GROWTH-India Telescope optical observations
  63. GRB 250920C: Swift-BAT refined analysis
  64. GRB 250920B: Swift-BAT refined analysis
  65. GRB 250920C: Enhanced Swift-XRT position
  66. GRB 250916A: FTW optical and NIR observations of the counterpart
  67. GRB 250920C: Swift/UVOT Detection
  68. GRB 250920B: Fermi GBM Observation
  69. GRB 250920A: Fermi GBM Detection
  70. GRB 250920C: Fermi GBM Observation
  71. Swift GRB 250920C: Global MASTER-Net observations report
  72. GRB 250920B: Swift/UVOT Detection
  73. GRB 250920B: FTW optical and NIR observations of the counterpart
  74. GRB 250920C: Optical counterpart detection by LCO
  75. GRB 250920A: SVOM/GRM observation
  76. GRB250920C: LCOGT Optical Detection
  77. GRB 250920B: Enhanced Swift-XRT position
  78. GRB 250920B: Swift-XRT refined Analysis
  79. GRB 250920B: SVOM/C-GFT optical observations
  80. GRB 250920C: GOTO optical counterpart candidate
  81. GRB 250919A / EP250919a: LCO optical observation
  82. Konus-Wind detection of GRB 250919A
  83. GRB 250920C: Swift detection of a burst
  84. GRB 250920C: Fermi GBM Final Real-time Localization
  85. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  86. Swift GRB 250920B: Global MASTER-Net observations report
  87. GRB 250919A / EP250919a: Insight-HXMT detection
  88. GRB 250920A: AstroSat CZTI detection
  89. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  90. GRB 250920B: Fermi GBM Final Real-time Localization
  91. GRB 250920A: BALROG localization (Fermi Trigger 780029651 / GRB 250920121)
  92. GRB 250920A: Fermi GBM Final Localization
  93. GRB 250919A/EP250919a: SVOM/VT optical observation
  94. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  95. GRB 250916A: Mondy R-band optical observations
  96. GRB 250919A: Glowbug gamma-ray detection
  97. GRB 250919A: Fermi GBM Observation
  98. Fermi GRB 250918A: Global MASTER-Net observations report
  99. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  100. GRB 250918A: SVOM/GRM observation

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