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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"

27032 results found.

  1. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  2. GRB 251001B: GOTO optical counterpart detection
  3. GRB 251001B: Swift detection of a burst
  4. GRB 251001B: Fermi GBM Final Real-time Localization
  5. GRB 251001A: Fermi GBM Detection
  6. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  7. GRB 251001A: BALROG localization (Fermi Trigger 780979261 / GRB 251001112)
  8. GRB 251001A: Fermi GBM Final Real-time Localization
  9. LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
  10. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  11. GRB 250925A: MAO/AZT-22 optical observations
  12. Fermi GRB 250929A: Global MASTER-Net observations report
  13. GRB 250929A: Fermi GBM Final Real-time Localization
  14. GRB 250926A: CALET Gamma-Ray Burst Monitor detection
  15. GRB 250925A: Mondy I-band optical observations
  16. GRB 250916A: SVOM/VT optical observation
  17. GRB 250924A: SVOM/GRM observation
  18. GRB 250925A: Swift-XRT refined Analysis
  19. GRB 250926A: Insight-HXMT detection
  20. GRB 250926B: Fermi GBM Final Localization
  21. Fermi trigger No 780609036: Global MASTER-Net observations report
  22. IceCube Alert 250926.52: Global MASTER-Net observations report
  23. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  24. GRB 250925A: Swift-BAT refined analysis
  25. GRB 250925A: Mondy and AbAO optical observations
  26. GRB 250925A: COLIBRÍ photometric redshift
  27. GRB 250925A/EP250925a: EP-WXT detection
  28. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  29. GRB 250925A : MITSuME Akeno optical upper limits
  30. GRB 250925A: JinShan optical observations
  31. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  32. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  33. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  34. Fermi GRB 250926A: Global MASTER-Net observations report
  35. GRB 250926A: Fermi GBM Final Real-time Localization
  36. GRB250925A: Liverpool Telescope optical observations
  37. GRB 250925A: NOT optical afterglow candidate
  38. GRB 250925A: Leavitt Observatory optical upper limit
  39. GRB 250924A: Swift-BAT refined analysis
  40. GRB 250925A: GROWTH-India Telescope Upper Limits
  41. GRB 250925A: Swift detection of a burst
  42. Swift GRB 250925A: Global MASTER-Net observations report
  43. GRB 250922A: SVOM/GRM observation
  44. GRB 250924A: 1.6m Mephisto optical upper limits
  45. GRB 250924A: NOT optical observations
  46. GRB 250924A: SVOM/VT optical observation
  47. GRB 250924A: Swift/UVOT Detection
  48. GRB 250924A: Swift-XRT refined Analysis
  49. GRB 250924A: J-band detection with WINTER
  50. GRB 250924A: GROWTH-India Telescope Upper Limits
  51. GRB 250924A: Kilonova-Catcher optical afterglow detection
  52. GRB 250920C: Kilonova-Catcher optical afterglow detection
  53. GRB 250922B: SVOM/GRM observation
  54. GRB 250920C: TRT optical observation
  55. GRB 250924B: Fermi GBM Final Localization
  56. GRB 250924A: COLIBRÍ optical observations
  57. Swift GRB 250924A: Global MASTER-Net observations report
  58. GRB 250919A / EP250919a: further LCO optical observation
  59. GRB 250924A: DDOTI Detection of the Optical Counterpart
  60. GRB 250924A: Swift detection of a burst with an optical counterpart
  61. GRB 250920B: AbAO optical upper limits
  62. GRB 250920C: VLT redshift confirmation z = 1.399
  63. EP250911a: e-MERLIN radio observations
  64. GRB 250920B: CrAO ZTSH optical observations
  65. GRB 250920C: COLIBRÍ optical observations
  66. Fermi GRB 250922B: Global MASTER-Net observations report
  67. GRB 250920C: NIR observations with WINTER
  68. GRB 250920B: NIR observations with WINTER
  69. Fermi trigger No 780156732: Global MASTER-Net observations report
  70. GRB 250922B: Fermi GBM Final Real-time Localization
  71. IPN triangulation of GRB 250920A (long/bright)
  72. GRB 250916A: Swift/UVOT Detection
  73. GRB 250920C: Swift-XRT refined Analysis
  74. GRB 250922A: Fermi GBM Final Localization
  75. GRB 250920B: Kitab-ISON optical upper limit
  76. GRB 250920C: SVOM/GRM observation
  77. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  78. GRB 250920C: GROWTH-India Telescope optical observations
  79. GRB 250920C: Swift-BAT refined analysis
  80. GRB 250920B: Swift-BAT refined analysis
  81. GRB 250916A: FTW optical and NIR observations of the counterpart
  82. GRB 250920C: Swift/UVOT Detection
  83. GRB 250920B: Fermi GBM Observation
  84. GRB 250920A: Fermi GBM Detection
  85. GRB 250920C: Fermi GBM Observation
  86. Swift GRB 250920C: Global MASTER-Net observations report
  87. GRB 250920B: Swift/UVOT Detection
  88. GRB 250920B: FTW optical and NIR observations of the counterpart
  89. GRB 250920C: Optical counterpart detection by LCO
  90. GRB 250920A: SVOM/GRM observation
  91. GRB250920C: LCOGT Optical Detection
  92. GRB 250920B: Swift-XRT refined Analysis
  93. GRB 250920B: SVOM/C-GFT optical observations
  94. GRB 250920C: GOTO optical counterpart candidate
  95. GRB 250919A / EP250919a: LCO optical observation
  96. GRB 250920C: Swift detection of a burst
  97. GRB 250920C: Fermi GBM Final Real-time Localization
  98. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  99. Swift GRB 250920B: Global MASTER-Net observations report
  100. GRB 250920B: Swift detection of a burst with a bright optical counterpart.

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