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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"

35441 results found.

  1. GRB 250920C: SVOM/GRM observation
  2. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  3. GRB 250917B: KAIT optical upper limit
  4. GRB 250920A: NuSTAR detection of bright prompt emission
  5. GRB 250920C: GROWTH-India Telescope optical observations
  6. GRB 250920C: Swift-BAT refined analysis
  7. GRB 250920B: Swift-BAT refined analysis
  8. GRB 250920C: Enhanced Swift-XRT position
  9. GRB 250916A: FTW optical and NIR observations of the counterpart
  10. GRB 250920C: Swift/UVOT Detection
  11. GRB 250920B: Fermi GBM Observation
  12. GRB 250920A: Fermi GBM Detection
  13. GRB 250920C: Fermi GBM Observation
  14. Swift GRB 250920C: Global MASTER-Net observations report
  15. GRB 250920B: Swift/UVOT Detection
  16. GRB 250920B: FTW optical and NIR observations of the counterpart
  17. GRB 250920C: Optical counterpart detection by LCO
  18. GRB 250920A: SVOM/GRM observation
  19. GRB250920C: LCOGT Optical Detection
  20. GRB 250920B: Enhanced Swift-XRT position
  21. GRB 250920B: Swift-XRT refined Analysis
  22. GRB 250920B: SVOM/C-GFT optical observations
  23. GRB 250920C: GOTO optical counterpart candidate
  24. GRB 250919A / EP250919a: LCO optical observation
  25. Konus-Wind detection of GRB 250919A
  26. GRB 250920C: Swift detection of a burst
  27. GRB 250920C: Fermi GBM Final Real-time Localization
  28. Swift GRB 250920B: Global MASTER-Net observations report
  29. GRB 250919A / EP250919a: Insight-HXMT detection
  30. GRB 250920A: AstroSat CZTI detection
  31. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  32. GRB 250920B: Fermi GBM Final Real-time Localization
  33. GRB 250920A: BALROG localization (Fermi Trigger 780029651 / GRB 250920121)
  34. GRB 250920A: Fermi GBM Final Localization
  35. GRB 250919A/EP250919a: SVOM/VT optical observation
  36. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  37. GRB 250916A: Mondy R-band optical observations
  38. GRB 250919A: Glowbug gamma-ray detection
  39. GRB 250919A: Fermi GBM Observation
  40. Fermi GRB 250918A: Global MASTER-Net observations report
  41. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  42. GRB 250918A: SVOM/GRM observation
  43. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  44. GRB 250919A: Swift-XRT afterglow detection
  45. GRB 250919A: Fermi-LAT detection
  46. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  47. GRB 250919A: SVOM/GRM observation of a very bright GRB
  48. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  49. EP250919a: Einstein Probe detection of an X-ray transient
  50. GRB 250916A: Fermi GBM Observation
  51. Fermi GRB 250919A: Global MASTER-Net observations report
  52. GRB 250919A: Fermi GBM Final Real-time Localization
  53. GRB 250916A: KAIT optical observations
  54. GRB 250917B: VLT/HAWK-I near-infrared observations
  55. GRB 250916A: NuSTAR detection of the prompt emission
  56. GRB 250916A: further SAO RAS optical observations
  57. GRB 250912A: SVOM/ECLAIRs refined analysis
  58. GRB 250917B: Swift-BAT refined analysis
  59. GRB 250918A: BALROG localization (Fermi Trigger 779891543 / GRB 250918522)
  60. GRB 250918A: Fermi GBM Final Real-time Localization
  61. GRB 250917B: Swift/UVOT Upper Limits
  62. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  63. GRB 250916A: Swift-XRT observations
  64. GRB 250916A: MAO/AZT-22 optical observations
  65. GRB 250916A: SAO RAS optical observations
  66. GRB 250916A : GIT optical observations
  67. GRB 250916A: Glowbug gamma-ray detection
  68. GRB250917B: WFST optical observations
  69. GRB 250916A: Swift ToO observations
  70. GRB 250917B: Fermi GBM Observation
  71. GRB 250917B: Swift-XRT observations
  72. Fermi GRB 250917B: Global MASTER-Net observations report
  73. GRB 250917B: Swift detection of a short burst
  74. GRB 250916A: GOTO optical counterpart candidate
  75. GRB 250917B: Fermi GBM Final Real-time Localization
  76. GRB 250917A: Fermi GBM Final Real-time Localization
  77. GRB 250916A: AstroSat CZTI detection of a bright long burst
  78. GRB 250910A: SVOM/ECLAIRs refined analysis
  79. Fermi GRB 250916A: Global MASTER-Net observations report
  80. GRB 250916A: Fermi GBM Final Real-time Localization
  81. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  82. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  83. GRB 250912A: Swift-XRT observations
  84. GRB250912A: VLT/HAWK-I follow-up observations
  85. GRB 250912A: VLT observations
  86. GRB 250912A: Fermi GBM Observation
  87. GRB 250911A: Insight-HXMT detection
  88. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  89. GRB 250912A:SVOM/VT optical upper limit
  90. GRB 250912A: LCO optical upper limit
  91. Fermi GRB 250912A: Global MASTER-Net observations report
  92. GRB 250912A: SVOM detection of a burst
  93. GRB 250912A: Fermi GBM Final Real-time Localization
  94. EP250911a: Upper limit from Fermi-GBM Observations
  95. GRB 250911A: GECAM-B detection
  96. GRB 250911A: Swift-BAT refined analysis
  97. GRB 250910B: SVOM/GRM observation
  98. GRB 250911A: MASTER optical counterpart observations
  99. EP250911a: SAO RAS optical observations
  100. GRB 250911A: Swift-XRT refined Analysis

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