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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"
  1. GRB 210210A: Enhanced Swift-XRT position
  2. GRB 210210A: MASTER afterglow observation
  3. ZTF21aahifke/AT2021clk: ZTF discovery of an optical fast transient (possible afterglow)
  4. Swift GRB 210210A: Global MASTER-Net observations report
  5. GRB 210210A: Swift detection of a burst with an optical counterpart
  6. GRB 210209A: Enhanced Swift-XRT position
  7. GRB 210209A: Swift detection of a burst
  8. GRB 210207B: Continued LCO Observations
  9. GRB 210104A: LBT observations
  10. GRB 210208A: BOOTES-2/TELMA optical upper limit
  11. GRB 210204A (ZTF21aagwbjr/AT2021buv): continued Mondy optical observations
  12. GRB 210207B: AstroSat CZTI detection
  13. GRB 210207B: Swift/UVOT Detection
  14. GRB 210207B: Swift-BAT refined analysis
  15. GRB 210207B: Insight-HXMT/HE detection
  16. GRB 210204A: LBT observations and jet break
  17. GRB 210204A: redshift revision of ZTF21aagwbjr/AT2021buv (correction to GCN 29411)
  18. GRB 210207B: LCO Optical Afterglow Detection
  19. GRB 210207B: KAIT Optical Observations
  20. GRB 210208A: A long GRB detected by INTEGRAL
  21. GRB 210207B: AGILE observations
  22. GRB 210207B: Swift-XRT refined Analysis
  23. Konus-Wind detection of GRB 210207B
  24. SGR 1935+2154: MAXI/GSC detection
  25. Konus-Wind detection of GRB 210204A (correction to GCN 29415)
  26. GRB 210207B: AbAO optical upper limit
  27. GRB 210207B: Enhanced Swift-XRT position
  28. GRB 210207B: optical detection with 3.6m Devasthal Optical Telescope
  29. GRB 210207B: Swift detection of a burst with a bright optical counterpart
  30. Fermi GRB 210207A: Global MASTER-Net observations report
  31. GRB 210207A: BALROG localization (Fermi Trigger / GRB 210207603)
  32. GRB 210204A (ZTF21aagwbjr/AT2021buv): Mondy and AbAO optical observations
  33. GRB 210207A: Fermi GBM Final Real-time Localization
  34. Konus-Wind detection of GRB 210204A / ZTF21aagwbjr
  35. GRB 210204A: Optical Observations from HCT
  36. GRB 210204A / ZTF21aagwbjr: Swift-XRT observations
  37. GRB 210204A: Swift ToO observations
  38. VLT/X-shooter redshift of 1.466 for ZTF21aagwbjr/AT2021buv, strengthening its association with GRB 210204A
  39. GRB 210204A: AstroSat CZTI Detection
  40. GRB 210205A: Swift-BAT refined analysis
  41. IPN triangulation of GRB 210204A
  42. GRB 210205A: Swift-XRT refined Analysis
  43. GRB 210205A: MITSuME Ishigaki optical observation
  44. ZTF21aagwbjr/AT2021buv: ZTF discovery of a fast optical transient likely associated with GRB 210104A
  45. GRB 210205B: AGILE/MCAL detection of a burst
  46. GRB 210205A: Swift/UVOT Upper Limits
  47. Swift GRB 210205A: Global MASTER-Net observations report
  48. GRB 210205A: Nanshan/NEXT optical upper limit
  49. GRB 210205A: BOOTES-4/MET optical upper limit
  50. GRB 210205A: Enhanced Swift-XRT position
  51. GRB 210205A： GWAC-F60A optical upper limit
  52. GRB 210205A: Swift detection of a burst
  53. Fermi GRB 210204B: Global MASTER-Net observations report
  54. Fermi GRB 210204A: Global MASTER-Net observations report
  55. GRB 210204B: Fermi GBM Final Real-time Localization
  56. GRB 210204: Fermi GBM observation
  57. GRB 210204A: GECAM detection
  58. GRB 210204A: BALROG localization (Fermi Trigger 634112970 / GRB 210204270)
  59. GRB 210204A: Fermi GBM Final Real-time Localization
  60. GRB 210202A: AGILE/MCAL detection
  61. Fermi GBM Observations of a bright burst from SGR J1935+2154
  62. GRB 210202A: Fermi GBM detection
  63. GRB 210202A: Fermi-LAT detection
  64. Fermi GRB 210202A: Global MASTER-Net observations report
  65. Fermi trigger No 633963272: Global MASTER-Net observations report
  66. Recent activity of SGR 1935+2154 as observed by CGBM
  67. GRB 210202A: BALROG localization (Fermi Trigger / GRB 210202841)
  68. INTEGRAL detection of a short burst from SGR 1935+2154
  69. GRB 210202A: Fermi GBM Final Real-time Localization
  70. GRB 210131A: GECAM detection
  71. Fermi trigger No 633879387: Global MASTER-Net observations report
  72. GECAM observations of SGR 1935+2154
  73. GRB 210129A: Insight-HXMT/HE detection
  74. Continued Chandra observations of GW170817 at ~3.3 years since merger
  75. Fermi GBM Observations of SGR J1935+2154
  76. Konus-Wind detection of two bright bursts from SGR 1935+2154
  77. GRB 140330A: Swift-XRT refined Analysis
  78. GRB 140320B: Swift-XRT refined Analysis
  79. GRB 140402A: Swift-XRT refined Analysis
  80. GRB 140104B: Swift-XRT refined Analysis
  81. GRB 210126A: AstroSat CZTI detection
  82. GRB 210124B: AstroSat CZTI detection
  83. GRB 210123A: AstroSat CZTI detection
  84. IPN triangulation of a bright burst from SGR 1935+2154
  85. ZTF21aaeyldq: Observations with the 3.6m DOT
  86. GECAM detection of a short burst probably from SGR 1935+2154
  87. GRB 210127A: Fermi GBM Final Real-time Localization
  88. GRB 210120A: Fermi GBM detection
  89. Fermi trigger No 633348010: Global MASTER-Net observations report
  90. HAWC Transient event on 2021/01/25
  91. Konus-Wind detection of GRB 210121A
  92. Konus-Wind detection of GRB 210124B
  93. GRB 210126A: GECAM detection
  94. IPN triangulation of GRB 210124B (short)
  95. GRB 210126A: BALROG localization (Fermi Trigger / GRB 210126417)
  96. GRB 210124B: Insight-HXMT/HE detection
  97. Fermi trigger No 633257525: Global MASTER-Net observations report
  98. GRB 210123A: Fermi GBM Final Localization
  99. GECAM detection of a burst possibly from the X-ray burster 4U 0614+09 or GRB 210124A
  100. GRB 210123A: Insight-HXMT/HE detection

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