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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"

34160 results found.

  1. GRB 250919A: Fermi GBM Observation
  2. Fermi GRB 250918A: Global MASTER-Net observations report
  3. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  4. GRB 250918A: SVOM/GRM observation
  5. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  6. GRB 250919A: Swift-XRT afterglow detection
  7. GRB 250919A: Fermi-LAT detection
  8. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  9. GRB 250919A: SVOM/GRM observation of a very bright GRB
  10. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  11. EP250919a: Einstein Probe detection of an X-ray transient
  12. GRB 250916A: Fermi GBM Observation
  13. Fermi GRB 250919A: Global MASTER-Net observations report
  14. GRB 250919A: Fermi GBM Final Real-time Localization
  15. GRB 250916A: KAIT optical observations
  16. GRB 250917B: VLT/HAWK-I near-infrared observations
  17. GRB 250916A: NuSTAR detection of the prompt emission
  18. GRB 250916A: further SAO RAS optical observations
  19. GRB 250912A: SVOM/ECLAIRs refined analysis
  20. GRB 250917B: Swift-BAT refined analysis
  21. GRB 250918A: BALROG localization (Fermi Trigger 779891543 / GRB 250918522)
  22. GRB 250918A: Fermi GBM Final Real-time Localization
  23. GRB 250917B: Swift/UVOT Upper Limits
  24. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  25. GRB 250916A: Swift-XRT observations
  26. GRB 250916A: MAO/AZT-22 optical observations
  27. GRB 250916A: SAO RAS optical observations
  28. GRB 250916A : GIT optical observations
  29. GRB 250916A: Glowbug gamma-ray detection
  30. GRB250917B: WFST optical observations
  31. GRB 250916A: Swift ToO observations
  32. GRB 250917B: Fermi GBM Observation
  33. GRB 250917B: Swift-XRT observations
  34. Fermi GRB 250917B: Global MASTER-Net observations report
  35. GRB 250917B: Swift detection of a short burst
  36. GRB 250916A: GOTO optical counterpart candidate
  37. GRB 250917B: Fermi GBM Final Real-time Localization
  38. GRB 250917A: Fermi GBM Final Real-time Localization
  39. GRB 250916A: AstroSat CZTI detection of a bright long burst
  40. GRB 250910A: SVOM/ECLAIRs refined analysis
  41. Fermi GRB 250916A: Global MASTER-Net observations report
  42. GRB 250916A: Fermi GBM Final Real-time Localization
  43. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  44. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  45. GRB 250912A: Swift-XRT observations
  46. GRB250912A: VLT/HAWK-I follow-up observations
  47. GRB 250912A: VLT observations
  48. GRB 250912A: Fermi GBM Observation
  49. GRB 250911A: Insight-HXMT detection
  50. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  51. GRB 250912A:SVOM/VT optical upper limit
  52. GRB 250912A: LCO optical upper limit
  53. Fermi GRB 250912A: Global MASTER-Net observations report
  54. GRB 250912A: SVOM detection of a burst
  55. GRB 250912A: Fermi GBM Final Real-time Localization
  56. EP250911a: Upper limit from Fermi-GBM Observations
  57. GRB 250911A: GECAM-B detection
  58. GRB 250911A: Swift-BAT refined analysis
  59. GRB 250910B: SVOM/GRM observation
  60. GRB 250911A: MASTER optical counterpart observations
  61. EP250911a: SAO RAS optical observations
  62. GRB 250911A: Swift-XRT refined Analysis
  63. GRB 250910C: Fermi GBM Final Localization Correction
  64. GRB 250911A: Swift/UVOT Detection
  65. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  66. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  67. GRB 250909B: Insight-HXMT detection
  68. GRB 250909B: SVOM/GRM observation
  69. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  70. Fermi GRB 250910B: Global MASTER-Net observations report
  71. GRB 250404A / EP250404a: spectroscopic redshift at z = 1.88 (correction to GCN 40084)
  72. GRB 250903A: SVOM/ECLAIRs refined analysis
  73. GRB 250911A: Enhanced Swift-XRT position
  74. GRB 250911A: Swift-XRT observations
  75. GRB 250911A: COLIBRÍ optical counterpart candidate
  76. GRB 250911A: Swift detection of a burst
  77. GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
  78. GRB 250910B: Fermi GBM Final Real-time Localization
  79. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  80. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  81. GRB 250909B: AstroSat CZTI detection of a long burst
  82. GRB 250910A: SVOM/VT optical upper limit
  83. GRB 250910A: LCO optical upper limit
  84. GRB 250909A: AstroSat CZTI detection
  85. GRB 250910A: SVOM/MXT possible afterglow detection
  86. GRB 250910A: SVOM detection of a faint burst
  87. GRB 250702B: Late time Chandra observations
  88. GRB 250907A: CALET Gamma-Ray Burst Monitor detection
  89. Fermi GRB 250909A: Global MASTER-Net observations report
  90. GRB 250909A: Fermi GBM Final Real-time Localization
  91. GRB 250907A: GECAM-B detection
  92. GRB 250905A: Swift-BAT refined analysis
  93. GRB 250903A: Swift-XRT afterglow detection
  94. GRB 250905A: Swift-XRT refined Analysis
  95. GRB 250904A: Swift-BAT refined analysis
  96. GRB 250905A: Swift/UVOT Upper Limits
  97. GRB 250901A - SVOM/ECLAIRs refined analysis
  98. GRB 250905B: Fermi GBM Final Localization
  99. GRB 250905A: Enhanced Swift-XRT position
  100. GRB 250904A: Swift/UVOT Detection

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