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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 210306A: Tautenburg observations
  2. GRB 210306A: iTelescope T24 optical observations
  3. GRB 210306A: Fermi-LAT detection
  4. GRB 210306B: Swift detection of a burst
  5. GRB 210306A: LCO Optical Afterglow Detection
  6. GRB 210306A: iTelescope optical afterglow observations
  7. GRB 210306A: DDOTI Afterglow Confirmation
  8. GRB 210306A: Swift detection of a burst with a bright optical counterpart
  9. Swift GRB 210305A: Global MASTER-Net observations report
  10. GRB 210305A: Swift detection of a burst
  11. GRB 210228B: Insight-HXMT/HE detection
  12. Trigger 1035744: Swift detection of Sco X-1 due to Star Tracker loss of lock
  13. Fermi trigger No 636459103: Global MASTER-Net observations report
  14. GRB 210217A: 3.6m DOT optical observations
  15. GRB 210226A: Swift/UVOT Upper Limits
  16. Fermi trigger No 636187116: Global MASTER-Net observations report
  17. GRB 210228A: GECAM detection
  18. Fermi trigger No 636168178: Global MASTER-Net observations report
  19. Integral GRB210227.20: Global MASTER-Net observations report
  20. Integral GRB210227.19: MASTER OT retraction
  21. GRB 210225A: Insight-HXMT/HE detection
  22. INTEGRAL IBAS Alert n.9020 not a GRB
  23. Integral GRB210227.20: Global MASTER-Net observations report
  24. Integral GRB210227.19: Global MASTER-Net observations report
  25. Integral GRB210227.19: Global MASTER-Net OT detection
  26. GRB 210226A: Swift-BAT refined analysis
  27. GRB 210226A: Fermi GBM detection
  28. GRB 210217A: Mondy optical observations
  29. GRB 210226A: KAIT Optical Upper Limit
  30. GRB 210226A: Swift-XRT refined Analysis
  31. Swift GRB 210226A: Global MASTER-Net observations report
  32. GRB 210218A: Swift-XRT confirmation of afterglow
  33. GRB 210226A: Burke-Gaffney Observatory optical upper limit
  34. GRB 210226A: Enhanced Swift-XRT position
  35. GRB 210226A: Ondrejov BART/SBT optical limit
  36. GRB 210222B: 1.3m DFOT Optical upper limit
  37. GRB 210226A: Swift detection of a burst
  38. GRB 210222B: REM observations of the optical/NIR afterglow
  39. Fermi trigger No 635922820: Global MASTER-Net observations report
  40. GRB 210222B: MITSuME Akeno optical upper limits
  41. Konus-Wind detection of GRB 210222A
  42. GRB 210222B: Zeiss-1000 of Koshka observatory, optical observations
  43. GRB 210222B: VIRT optical detection
  44. GRB 210222B: Swift-BAT refined analysis
  45. GRB 210222B: Swift-XRT refined Analysis
  46. GRB 210222B: Swift/UVOT Detection
  47. GRB 210222B: KAIT Optical Upper Limit
  48. GRB 210222B: FRAM-ORM afterglow detection
  49. GRB 210218A: Swift/UVOT observations
  50. GRB 210217A: Swift/UVOT Detection
  51. GRB 210222B: MASTER OT observation
  52. GRB 210222A: CALET Gamma-Ray Burst Monitor detection
  53. GRB 210222B: Redshift from FORS2/VLT
  54. GRB 210222B: NEXT early optical afterglow observations
  55. GRB 210222B: GOTO confirmation of afterglow detection (correction to GCN29548)
  56. GRB 210222B: Liverpool Telescope optical detection
  57. GRB 210222B: GOTO confirmation of afterglow detection
  58. GRB210222B: LCO Optical Afterglow Detection
  59. GRB210222B: BOOTES-1 optical afterglow detection
  60. GRB 210222B: Swift detection of a burst with an optical counterpart
  61. Swift GRB210222.94: Global MASTER-Net observations report
  62. GRB 210222A: MAXI/GSC detection
  63. GRB 210218A: Swift-XRT observations
  64. uGMRT radio detection of GRB 210204A
  65. GRB 210212A: Lowell Discovery Telescope observations
  66. GRB 210217A: 1.3m DFOT optical detection
  67. GRB 210217A: Swift-XRT refined Analysis
  68. GRB 210218A: Swift-BAT refined analysis
  69. Fermi GBM Sub-Threshold Detection of GRB 210217A
  70. GRB 210217A: Liverpool Telescope First Hour Observations
  71. GRB 210217A: Swift-BAT refined analysis
  72. GRB 210217A: KAIT Optical Observations
  73. GRB 210218A: MITSuME Akeno optical upper limits
  74. GRB 210218A： GWAC-F60A optical upper limit
  75. GRB 210218A: NEXT optical upper limit
  76. GRB 210218A: Swift detection of a burst
  77. ZTF21aakruew/AT2021cwd: GROND observations
  78. GRB 210212A: REM early-time optical/NIR upper limits
  79. GRB 210205A: observations with the 3.6m DOT, a potential dark burst?
  80. GRB 210217A: Enhanced Swift-XRT position
  81. Fermi/GBM observation of a burst from SGR 1830-0645
  82. GRB 210217A: NEXT early optical afterglow observations
  83. GRB 210212A: Mondy optical observations
  84. GRB 210217A: Swift detection of a burst with an optical counterpart
  85. GRB 210204A (ZTF21aagwbjr/AT2021buv): continued Assy and Mondy optical observations
  86. IceCube-210210A: Two Additional Optical Candidate Counterparts Found by DECam
  87. GRB 210208A: 1.3m DFOT Optical upper limit
  88. GRB 210210A: Konus-Wind detection and joint Konus-Wind + Swift-BAT spectral analysis
  89. Swift Trigger 1033144: Detection of SGR 1830-0645
  90. GRB 210211A: ePESSTO+ NTT optical observations
  91. Konus-Wind detection of GRB 210212B / ZTF21aakruew
  92. GRB 210212B: Swift ToO observations
  93. GRB 210212B (TF21aakruew/AT2021cwd): Assy optical observations
  94. IPN triangulation of GRB 210212B (consistent with ZTF21aakruew/AT2021cwd)
  95. GRB 210212A: 1.3m DFOT Optical upper limit
  96. GRB 210213B: Insight-HXMT/HE detection
  97. ZTF21aakruew/AT2021cwd: ZTF and LT discovery of a hostless, red, and rapidly fading optical transient
  98. GRB 210212A: Gemini South optical observations
  99. IceCube alert 134994_1103075 retraction
  100. Fermi GRB 210213A: Global MASTER-Net observations report

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