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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"

36804 results found.

  1. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  2. GRB 250916A: Swift-XRT observations
  3. GRB 250916A: MAO/AZT-22 optical observations
  4. GRB 250916A: SAO RAS optical observations
  5. GRB 250916A : GIT optical observations
  6. GRB 250916A: Glowbug gamma-ray detection
  7. GRB250917B: WFST optical observations
  8. GRB 250916A: Swift ToO observations
  9. GRB 250917B: Fermi GBM Observation
  10. GRB 250917B: Swift-XRT observations
  11. Fermi GRB 250917B: Global MASTER-Net observations report
  12. GRB 250917B: Swift detection of a short burst
  13. GRB 250916A: GOTO optical counterpart candidate
  14. GRB 250917B: Fermi GBM Final Real-time Localization
  15. GRB 250917A: Fermi GBM Final Real-time Localization
  16. GRB 250916A: AstroSat CZTI detection of a bright long burst
  17. GRB 250910A: SVOM/ECLAIRs refined analysis
  18. Fermi GRB 250916A: Global MASTER-Net observations report
  19. GRB 250916A: Fermi GBM Final Real-time Localization
  20. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  21. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  22. GRB 250912A: Swift-XRT observations
  23. GRB250912A: VLT/HAWK-I follow-up observations
  24. GRB 250912A: VLT observations
  25. GRB 250912A: Fermi GBM Observation
  26. GRB 250911A: Insight-HXMT detection
  27. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  28. GRB 250912A:SVOM/VT optical upper limit
  29. GRB 250912A: LCO optical upper limit
  30. Fermi GRB 250912A: Global MASTER-Net observations report
  31. GRB 250912A: SVOM detection of a burst
  32. GRB 250912A: Fermi GBM Final Real-time Localization
  33. EP250911a: Upper limit from Fermi-GBM Observations
  34. GRB 250911A: GECAM-B detection
  35. GRB 250911A: Swift-BAT refined analysis
  36. GRB 250910B: SVOM/GRM observation
  37. GRB 250911A: MASTER optical counterpart observations
  38. EP250911a: SAO RAS optical observations
  39. GRB 250911A: Swift-XRT refined Analysis
  40. GRB 250910C: Fermi GBM Final Localization Correction
  41. GRB 250911A: Swift/UVOT Detection
  42. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  43. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  44. GRB 250909B: Insight-HXMT detection
  45. GRB 250909B: SVOM/GRM observation
  46. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  47. Fermi GRB 250910B: Global MASTER-Net observations report
  48. GRB 250404A / EP250404a: spectroscopic redshift at z = 1.88 (correction to GCN 40084)
  49. GRB 250903A: SVOM/ECLAIRs refined analysis
  50. GRB 250911A: Enhanced Swift-XRT position
  51. GRB 250911A: Swift-XRT observations
  52. GRB 250911A: COLIBRÍ optical counterpart candidate
  53. GRB 250911A: Swift detection of a burst
  54. GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
  55. GRB 250910B: Fermi GBM Final Real-time Localization
  56. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  57. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  58. GRB 250909B: AstroSat CZTI detection of a long burst
  59. GRB 250910A: SVOM/VT optical upper limit
  60. GRB 250910A: LCO optical upper limit
  61. GRB 250909A: AstroSat CZTI detection
  62. GRB 250910A: SVOM/MXT possible afterglow detection
  63. GRB 250910A: SVOM detection of a faint burst
  64. GRB 250702B: Late time Chandra observations
  65. GRB 250907A: CALET Gamma-Ray Burst Monitor detection
  66. Fermi GRB 250909A: Global MASTER-Net observations report
  67. GRB 250909A: Fermi GBM Final Real-time Localization
  68. GRB 250907A: GECAM-B detection
  69. GRB 250905A: Swift-BAT refined analysis
  70. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  71. GRB 250903A: Swift-XRT afterglow detection
  72. GRB 250905A: Swift-XRT refined Analysis
  73. IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event
  74. GRB 250904A: Swift-BAT refined analysis
  75. GRB 250905A: Swift/UVOT Upper Limits
  76. GRB 250901A - SVOM/ECLAIRs refined analysis
  77. GRB 250905B: Fermi GBM Final Localization
  78. GRB 250905A: Enhanced Swift-XRT position
  79. GRB 250904A: Swift/UVOT Detection
  80. GRB 250903A: Swift/UVOT detection
  81. GRB 250904A: Swift-XRT refined Analysis
  82. GRB 250905A: KAIT optical upper limit
  83. GRB 250905A: Swift detection of a burst
  84. Swift GRB 250904A: Global MASTER-Net observations report
  85. GRB 250904A: Enhanced Swift-XRT position
  86. GRB 250904A: TRT optical counterpart detection
  87. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  88. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  89. GRB 250904A: Prompt enhanced Swift-XRT position
  90. GRB 250904A: Swift detection of a burst
  91. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  92. GRB 250902A: VZLUSAT-2 detection
  93. GRB 250903A: Swift-XRT observations
  94. GRB 250830C: VZLUSAT-2 detection
  95. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  96. GRB 250903A: EP-FXT counterpart detection
  97. GRB 250902A: GECAM-B detection
  98. GRB 250903A: LCO optical observation
  99. GRB 250903A: LCO optical afterglow detection
  100. GRB 250903A: SVOM/VT optical confirmation with VHF data

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