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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 210212A: Swift detection of a burst
  2. GRB 210207B: GECAM detection
  3. GRB 210211A: Swift/UVOT Detection
  4. GRB 210211A: Swift-XRT refined Analysis
  5. GRB 210211A: Swift-BAT refined analysis
  6. GRB 210211A: Fermi GBM observation
  7. GRB 210210A as a BdHN II
  8. Swift-XRT observations of IceCube-210210A
  9. GRB 210209A: Swift-BAT refined analysis
  10. GRB 210211A: Enhanced Swift-XRT position
  11. GRB 210211A: MASTER optical observation of REM OT
  12. GRB 210210A: CAHA detection and likely jet break
  13. IceCube-210210A: No neutrino counterpart in ANTARES
  14. GRB 210211A: REM optical/NIR afterglow detection
  15. Fermi-LAT Gamma-ray Observations of IceCube-210210A
  16. GRB 210211A: Swift detection of a burst
  17. Swift GRB210211.36: Global MASTER-Net observations report
  18. GRB 210211A: Fermi GBM Final Real-time Localization
  19. GRB 210210A: FRAM-ORM afterglow detection
  20. Fermi trigger No 634659312: Global MASTER-Net observations report
  21. GRB 210210A: Swift-BAT refined analysis
  22. IceCube Alert 210210.50: Global MASTER-Net observations report
  23. Fermi GRB 210210B: Global MASTER-Net observations report
  24. IceCube-210210A: Upper limits from Fermi-GBM Observations
  25. IceCube-210210A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  26. GRB 210210B: Fermi GBM Final Real-time Localization
  27. IceCube-210210A: Two Candidate Counterparts from the Zwicky Transient Facility
  28. GRB 210209A: BOOTES-4/MET optical upper limit
  29. GRB 210210A: LCO Optical Afterglow Detection
  30. Swift GRB 210209A: Global MASTER-Net observations report
  31. GRB 210210A: Swift/UVOT Detection
  32. GRB 210112A: LBT host detection and correction to GCN 29319 (CAHA observations)
  33. GRB 210209A: MITSuME Akeno optical upper limits
  34. IceCube-210210A: IceCube observation of a high-energy neutrino candidate event
  35. GRB 210209A: Swift/UVOT Upper Limits
  36. GRB 210210A: Swift-XRT refined Analysis
  37. GRB 210208A: GIT optical upper limit
  38. GRB 210210A: Redshift from OSIRIS/GTC
  39. GRB 210209A: Swift-XRT refined Analysis
  40. GRB 210210A: Enhanced Swift-XRT position
  41. GRB 210210A: MASTER afterglow observation
  42. ZTF21aahifke/AT2021clk: ZTF discovery of an optical fast transient (possible afterglow)
  43. Swift GRB 210210A: Global MASTER-Net observations report
  44. GRB 210210A: Swift detection of a burst with an optical counterpart
  45. GRB 210209A: Enhanced Swift-XRT position
  46. GRB 210209A: Swift detection of a burst
  47. GRB 210207B: Continued LCO Observations
  48. GRB 210104A: LBT observations
  49. GRB 210208A: BOOTES-2/TELMA optical upper limit
  50. GRB 210204A (ZTF21aagwbjr/AT2021buv): continued Mondy optical observations
  51. GRB 210207B: AstroSat CZTI detection
  52. GRB 210207B: Swift/UVOT Detection
  53. GRB 210207B: Swift-BAT refined analysis
  54. GRB 210207B: Insight-HXMT/HE detection
  55. GRB 210204A: LBT observations and jet break
  56. GRB 210204A: redshift revision of ZTF21aagwbjr/AT2021buv (correction to GCN 29411)
  57. GRB 210207B: LCO Optical Afterglow Detection
  58. GRB 210207B: KAIT Optical Observations
  59. GRB 210208A: A long GRB detected by INTEGRAL
  60. GRB 210207B: AGILE observations
  61. GRB 210207B: Swift-XRT refined Analysis
  62. Konus-Wind detection of GRB 210207B
  63. SGR 1935+2154: MAXI/GSC detection
  64. Konus-Wind detection of GRB 210204A (correction to GCN 29415)
  65. GRB 210207B: AbAO optical upper limit
  66. GRB 210207B: Enhanced Swift-XRT position
  67. GRB 210207B: optical detection with 3.6m Devasthal Optical Telescope
  68. GRB 210207B: Swift detection of a burst with a bright optical counterpart
  69. Fermi GRB 210207A: Global MASTER-Net observations report
  70. GRB 210207A: BALROG localization (Fermi Trigger / GRB 210207603)
  71. GRB 210204A (ZTF21aagwbjr/AT2021buv): Mondy and AbAO optical observations
  72. GRB 210207A: Fermi GBM Final Real-time Localization
  73. Konus-Wind detection of GRB 210204A / ZTF21aagwbjr
  74. GRB 210204A: Optical Observations from HCT
  75. GRB 210204A / ZTF21aagwbjr: Swift-XRT observations
  76. GRB 210204A: Swift ToO observations
  77. VLT/X-shooter redshift of 1.466 for ZTF21aagwbjr/AT2021buv, strengthening its association with GRB 210204A
  78. GRB 210204A: AstroSat CZTI Detection
  79. GRB 210205A: Swift-BAT refined analysis
  80. IPN triangulation of GRB 210204A
  81. GRB 210205A: Swift-XRT refined Analysis
  82. GRB 210205A: MITSuME Ishigaki optical observation
  83. ZTF21aagwbjr/AT2021buv: ZTF discovery of a fast optical transient likely associated with GRB 210104A
  84. GRB 210205B: AGILE/MCAL detection of a burst
  85. GRB 210205A: Swift/UVOT Upper Limits
  86. Swift GRB 210205A: Global MASTER-Net observations report
  87. GRB 210205A: Nanshan/NEXT optical upper limit
  88. GRB 210205A: BOOTES-4/MET optical upper limit
  89. GRB 210205A: Enhanced Swift-XRT position
  90. GRB 210205A： GWAC-F60A optical upper limit
  91. GRB 210205A: Swift detection of a burst
  92. Fermi GRB 210204B: Global MASTER-Net observations report
  93. Fermi GRB 210204A: Global MASTER-Net observations report
  94. GRB 210204B: Fermi GBM Final Real-time Localization
  95. GRB 210204: Fermi GBM observation
  96. GRB 210204A: GECAM detection
  97. GRB 210204A: BALROG localization (Fermi Trigger 634112970 / GRB 210204270)
  98. GRB 210204A: Fermi GBM Final Real-time Localization
  99. GRB 210202A: AGILE/MCAL detection
  100. Fermi GBM Observations of a bright burst from SGR J1935+2154

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