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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"

35152 results found.

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

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