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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. Trigger 1035744: Swift detection of Sco X-1 due to Star Tracker loss of lock
  2. Fermi trigger No 636459103: Global MASTER-Net observations report
  3. GRB 210217A: 3.6m DOT optical observations
  4. GRB 210226A: Swift/UVOT Upper Limits
  5. Fermi trigger No 636187116: Global MASTER-Net observations report
  6. GRB 210228A: GECAM detection
  7. Fermi trigger No 636168178: Global MASTER-Net observations report
  8. Integral GRB210227.20: Global MASTER-Net observations report
  9. Integral GRB210227.19: MASTER OT retraction
  10. GRB 210225A: Insight-HXMT/HE detection
  11. INTEGRAL IBAS Alert n.9020 not a GRB
  12. Integral GRB210227.20: Global MASTER-Net observations report
  13. Integral GRB210227.19: Global MASTER-Net observations report
  14. Integral GRB210227.19: Global MASTER-Net OT detection
  15. GRB 210226A: Swift-BAT refined analysis
  16. GRB 210226A: Fermi GBM detection
  17. GRB 210217A: Mondy optical observations
  18. GRB 210226A: KAIT Optical Upper Limit
  19. GRB 210226A: Swift-XRT refined Analysis
  20. Swift GRB 210226A: Global MASTER-Net observations report
  21. GRB 210218A: Swift-XRT confirmation of afterglow
  22. GRB 210226A: Burke-Gaffney Observatory optical upper limit
  23. GRB 210226A: Enhanced Swift-XRT position
  24. GRB 210226A: Ondrejov BART/SBT optical limit
  25. GRB 210222B: 1.3m DFOT Optical upper limit
  26. GRB 210226A: Swift detection of a burst
  27. GRB 210222B: REM observations of the optical/NIR afterglow
  28. Fermi trigger No 635922820: Global MASTER-Net observations report
  29. GRB 210222B: MITSuME Akeno optical upper limits
  30. Konus-Wind detection of GRB 210222A
  31. GRB 210222B: Zeiss-1000 of Koshka observatory, optical observations
  32. GRB 210222B: VIRT optical detection
  33. GRB 210222B: Swift-BAT refined analysis
  34. GRB 210222B: Swift-XRT refined Analysis
  35. GRB 210222B: Swift/UVOT Detection
  36. GRB 210222B: KAIT Optical Upper Limit
  37. GRB 210222B: FRAM-ORM afterglow detection
  38. GRB 210218A: Swift/UVOT observations
  39. GRB 210217A: Swift/UVOT Detection
  40. GRB 210222B: MASTER OT observation
  41. GRB 210222A: CALET Gamma-Ray Burst Monitor detection
  42. GRB 210222B: Redshift from FORS2/VLT
  43. GRB 210222B: NEXT early optical afterglow observations
  44. GRB 210222B: GOTO confirmation of afterglow detection (correction to GCN29548)
  45. GRB 210222B: Liverpool Telescope optical detection
  46. GRB 210222B: GOTO confirmation of afterglow detection
  47. GRB210222B: LCO Optical Afterglow Detection
  48. GRB210222B: BOOTES-1 optical afterglow detection
  49. GRB 210222B: Swift detection of a burst with an optical counterpart
  50. Swift GRB210222.94: Global MASTER-Net observations report
  51. GRB 210222A: MAXI/GSC detection
  52. GRB 210218A: Swift-XRT observations
  53. uGMRT radio detection of GRB 210204A
  54. GRB 210212A: Lowell Discovery Telescope observations
  55. GRB 210217A: 1.3m DFOT optical detection
  56. GRB 210217A: Swift-XRT refined Analysis
  57. GRB 210218A: Swift-BAT refined analysis
  58. Fermi GBM Sub-Threshold Detection of GRB 210217A
  59. GRB 210217A: Liverpool Telescope First Hour Observations
  60. GRB 210217A: Swift-BAT refined analysis
  61. GRB 210217A: KAIT Optical Observations
  62. GRB 210218A: MITSuME Akeno optical upper limits
  63. GRB 210218A： GWAC-F60A optical upper limit
  64. GRB 210218A: NEXT optical upper limit
  65. GRB 210218A: Swift detection of a burst
  66. Subject: ZTF21aakruew/AT2021cwd: GROND observations
  67. GRB 210212A: REM early-time optical/NIR upper limits
  68. GRB 210205A: observations with the 3.6m DOT, a potential dark burst?
  69. GRB 210217A: Enhanced Swift-XRT position
  70. Fermi/GBM observation of a burst from SGR 1830-0645
  71. GRB 210217A: NEXT early optical afterglow observations
  72. GRB 210212A: Mondy optical observations
  73. GRB 210217A: Swift detection of a burst with an optical counterpart
  74. GRB 210204A (ZTF21aagwbjr/AT2021buv): continued Assy and Mondy optical observations
  75. IceCube-210210A: Two Additional Optical Candidate Counterparts Found by DECam
  76. GRB 210208A: 1.3m DFOT Optical upper limit
  77. GRB 210210A: Konus-Wind detection and joint Konus-Wind + Swift-BAT spectral analysis
  78. Swift Trigger 1033144: Detection of SGR 1830-0645
  79. GRB 210211A: ePESSTO+ NTT optical observations
  80. Konus-Wind detection of GRB 210212B / ZTF21aakruew
  81. GRB 210212B: Swift ToO observations
  82. GRB 210212B (TF21aakruew/AT2021cwd): Assy optical observations
  83. IPN triangulation of GRB 210212B (consistent with ZTF21aakruew/AT2021cwd)
  84. GRB 210212A: 1.3m DFOT Optical upper limit
  85. GRB 210213B: Insight-HXMT/HE detection
  86. ZTF21aakruew/AT2021cwd: ZTF and LT discovery of a hostless, red, and rapidly fading optical transient
  87. GRB 210212A: Gemini South optical observations
  88. IceCube alert 134994_1103075 retraction
  89. Fermi GRB 210213A: Global MASTER-Net observations report
  90. IceCube Alert 210213.78: Global MASTER-Net observations report
  91. GRB 210213A: Fermi GBM Final Real-time Localization
  92. GRB 210210A: CAHA 2nd epoch and jet break confirmation
  93. IceCube-210210A: Four Candidate Optical Counterparts from DECam Observations
  94. Swift Trigger 1032350: Detection of SGR 1830-0645
  95. GRB 210204A (ZTF21aagwbjr/AT2021buv): continued CrAO and AbAO optical observations
  96. GRB 210212A: Possible host galaxy counterpart with the NOT
  97. Swift GRB 210212A: Global MASTER-Net observations report
  98. GRB 210212A: MITSuME Akeno optical upper limits
  99. GRB 210212A: Swift-XRT refined Analysis
  100. GRB 210212A: BOOTES-4/MET optical upper limit

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