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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"

36162 results found.

  1. GRB 250916A: Fermi GBM Final Real-time Localization
  2. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  3. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  4. GRB 250912A: Swift-XRT observations
  5. GRB250912A: VLT/HAWK-I follow-up observations
  6. GRB 250912A: VLT observations
  7. GRB 250912A: Fermi GBM Observation
  8. GRB 250911A: Insight-HXMT detection
  9. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  10. GRB 250912A:SVOM/VT optical upper limit
  11. GRB 250912A: LCO optical upper limit
  12. Fermi GRB 250912A: Global MASTER-Net observations report
  13. GRB 250912A: SVOM detection of a burst
  14. GRB 250912A: Fermi GBM Final Real-time Localization
  15. EP250911a: Upper limit from Fermi-GBM Observations
  16. GRB 250911A: GECAM-B detection
  17. GRB 250911A: Swift-BAT refined analysis
  18. GRB 250910B: SVOM/GRM observation
  19. GRB 250911A: MASTER optical counterpart observations
  20. EP250911a: SAO RAS optical observations
  21. GRB 250911A: Swift-XRT refined Analysis
  22. GRB 250910C: Fermi GBM Final Localization Correction
  23. GRB 250911A: Swift/UVOT Detection
  24. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  25. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  26. GRB 250909B: Insight-HXMT detection
  27. GRB 250909B: SVOM/GRM observation
  28. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  29. Fermi GRB 250910B: Global MASTER-Net observations report
  30. GRB 250404A / EP250404a: spectroscopic redshift at z = 1.88 (correction to GCN 40084)
  31. GRB 250903A: SVOM/ECLAIRs refined analysis
  32. GRB 250911A: Enhanced Swift-XRT position
  33. GRB 250911A: Swift-XRT observations
  34. GRB 250911A: COLIBRÍ optical counterpart candidate
  35. GRB 250911A: Swift detection of a burst
  36. GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
  37. GRB 250910B: Fermi GBM Final Real-time Localization
  38. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  39. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  40. GRB 250909B: AstroSat CZTI detection of a long burst
  41. GRB 250910A: SVOM/VT optical upper limit
  42. GRB 250910A: LCO optical upper limit
  43. GRB 250909A: AstroSat CZTI detection
  44. GRB 250910A: SVOM/MXT possible afterglow detection
  45. GRB 250910A: SVOM detection of a faint burst
  46. GRB 250702B: Late time Chandra observations
  47. GRB 250907A: CALET Gamma-Ray Burst Monitor detection
  48. Fermi GRB 250909A: Global MASTER-Net observations report
  49. GRB 250909A: Fermi GBM Final Real-time Localization
  50. GRB 250907A: GECAM-B detection
  51. GRB 250905A: Swift-BAT refined analysis
  52. GRB 250903A: Swift-XRT afterglow detection
  53. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  54. GRB 250905A: Swift-XRT refined Analysis
  55. GRB 250904A: Swift-BAT refined analysis
  56. GRB 250905A: Swift/UVOT Upper Limits
  57. GRB 250901A - SVOM/ECLAIRs refined analysis
  58. GRB 250905B: Fermi GBM Final Localization
  59. GRB 250905A: Enhanced Swift-XRT position
  60. GRB 250904A: Swift/UVOT Detection
  61. GRB 250903A: Swift/UVOT detection
  62. GRB 250904A: Swift-XRT refined Analysis
  63. GRB 250905A: KAIT optical upper limit
  64. GRB 250905A: Swift detection of a burst
  65. Swift GRB 250904A: Global MASTER-Net observations report
  66. GRB 250904A: Enhanced Swift-XRT position
  67. GRB 250904A: TRT optical counterpart detection
  68. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  69. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  70. GRB 250904A: Prompt enhanced Swift-XRT position
  71. GRB 250904A: Swift detection of a burst
  72. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  73. GRB 250902A: VZLUSAT-2 detection
  74. GRB 250903A: Swift-XRT observations
  75. GRB 250830C: VZLUSAT-2 detection
  76. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  77. GRB 250903A: EP-FXT counterpart detection
  78. GRB 250902A: GECAM-B detection
  79. GRB 250903A: LCO optical observation
  80. GRB 250903A: LCO optical afterglow detection
  81. GRB 250903A: SVOM/VT optical confirmation with VHF data
  82. EP250901a: Mondy, Assy and SAO RAS optical limits
  83. Subject GRB 250903A: SVOM/MXT afterglow detection
  84. GRB 250903A: TRT optical counterpart detection
  85. GRB 250902B: AstroSat CZTI detection
  86. GRB 250903A: SVOM detection of a burst
  87. EP 250827B: Detection of supernova counterpart by LCO.
  88. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  89. GRB 250902B: SVOM/GRM observation
  90. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  91. Fermi GRB 250902B: Global MASTER-Net observations report
  92. GRB 250902A: Fermi GBM Detection
  93. GRB 250901A: Swift/UVOT Upper Limit
  94. GRB 250902B: Fermi GBM Final Real-time Localization
  95. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  96. GRB 250830B: Swift-XRT afterglow detection
  97. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  98. GRB 250902A: SVOM/GRM observation
  99. GRB 250901A: EP-FXT follow-up observation
  100. GRB 250901A: NOT optical observations

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