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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 200716A: Swift/BAT-GUANO archival detection and arcminute localization
  2. Swift trigger 1047857 is 4U 1700-377
  3. IceCube Alert 210510.20: Global MASTER-Net observations report
  4. GRB 210510A: Fermi GBM Final Real-time Localization
  5. IceCube-210510A: DDOTI Upper Limits
  6. GRB 210509A: RATIR Optical and NIR Upper Limits
  7. GRB 210509A: Swift/UVOT Upper Limits
  8. GRB 210509A: Swift-XRT refined Analysis
  9. IceCube-210510A - IceCube observation of a high-energy neutrino candidate track-like event
  10. GRB 210509A: Swift-BAT refined analysis
  11. Swift GRB 210509A: Global MASTER-Net observations report
  12. GRB 210509A: Enhanced Swift-XRT position
  13. GRB 210509A: BOOTES-4/MET optical upper limit
  14. GRB 210509A: Swift-XRT observations
  15. GRB 210509A: Swift detection of a burst
  16. GRB 210506A: Swift/BAT-GUANO position retraction
  17. IPN triangulation of GRB 210506A
  18. HAWC-210507A: No neutrino counterpart candidates in ANTARES search
  19. Fermi GRB 210507A: Global MASTER-Net observations report
  20. Fermi-LAT Gamma-ray Observations of IceCube-210503A and detection of a new gamma-ray source, Fermi J0931.9+3633
  21. ZTF21aayokph (AT2021lfa): continued Mondy optical observations
  22. GRB 210507A: Fermi GBM Final Real-time Localization
  23. Integral GRB210507.04: Global MASTER-Net observations report
  24. Integral GRB210506.78: Global MASTER-Net observations report
  25. GRB 210506A: Swift-XRT observations
  26. ZTF21aayokph (AT2021lfa): MASTER OT detection 3h befor ZTF
  27. Alert from the HAWC Burst Monitor HAWC-210507A
  28. HAWC GRB 210507.443: DDOTI Upper Limit
  29. GRB 210506A: Nanshan/NEXT optical upper limit
  30. GRB 210506A: TNG NIR upper limits
  31. ZTF21aayokph (AT2021lfa): Mondy and Koshka observatory optical observations
  32. ZTF21aayokph (AT2021lfa): X-ray Detection with Swift/XRT
  33. Lowell Discovery Telescope Observations of ZTF21aayokph (AT2021lfa)
  34. IceCube-210503A: IceCube observation of a high-energy neutrino candidate event
  35. ZTF21aayokph (AT2021lfa): Assy optical observations
  36. GRB 210506A: Swift ToO observations
  37. ZTF21aayokph (AT2021lfa): Nanshan/NEXT optical upper limit
  38. GRB 210506A: Swift/BAT-GUANO detection and possible arcminute localization of a short hard burst
  39. GRB 210504A: Lowell Discovery Telescope optical observations
  40. ZTF21aayokph (AT2021lfa): Redshift from Gemini South
  41. GRB 210504A: VLT X-shooter redshift
  42. GRB 210424B: AstroSat CZTI detection
  43. GRB 210504A: Swift-XRT refined Analysis
  44. RATIR Observations of ZTF21aayokph (AT2021lfa)
  45. DDOTI Observations of ZTF21aayokph (AT2021lfa)
  46. GRB 210504A: Swift-BAT refined analysis
  47. ZTF and LT observations of ZTF21aayokph (AT2021lfa), a fast-fading red transient
  48. GRB 210504A: NOT optical afterglow detection
  49. GRB 210504A: MITSuME Akeno optical upper limits
  50. Fermi GRB 210503A: DDOTI Upper Limits on the Afterglow
  51. GRB 210504A: AST3-3 YaoAn Optical Upper Limit
  52. GRB 210504A: Swift/UVOT Detection
  53. GRB 210504A: BOOTES-4/MET optical upper limit
  54. Swift GRB210504.58: Global MASTER-Net observations report
  55. GRB 210504A: update on the BAT trigger time and burst duration
  56. GRB 210504A: Swift detection of a burst
  57. Fermi GRB 210503A: Global MASTER-Net observations report
  58. GRB 210503A: Fermi GBM Final Real-time Localization
  59. Swift GRB210502.74: Global MASTER-Net observations report
  60. Swift Detection of MAXI J1803-298 including an optical counterpart
  61. MAXI GRB210501.83: Global MASTER-Net observations report
  62. Fermi GRB 210501A: Global MASTER-Net observations report
  63. Fermi trigger No 641601187: Global MASTER-Net observations report
  64. GRB 210430A: BOOTES-1 optical limit
  65. GRB 210424B: MITSuME Akeno optical upper limits
  66. GRB 210501A: Fermi GBM Final Real-time Localization
  67. GRB 210430A: Swift-BAT refined analysis
  68. Fermi GRB 210430B: Global MASTER-Net observations report
  69. GRB 210430B: Fermi GBM Final Real-time Localization
  70. Swift GRB210430.45: Global MASTER-Net observations report
  71. GRB 210430A: Swift detection of a burst
  72. GRB 210424B: CALET Gamma-Ray Burst Monitor detection
  73. GRB 210413B: Swift/UVOT Observations
  74. Konus-Wind detection of GRB 210424B
  75. Delayed GRB GCN Notices from Swift
  76. IPN triangulation of GRB 210424B (short/hard)
  77. GRB 210323B: Swift-XRT observations
  78. Swift Trigger 1045571 is not a GRB
  79. GRB 210427A: GECAM detection
  80. GRB 210427A: BALROG localization (Fermi Trigger / GRB 210427206)
  81. Fermi GRB 210427A: Global MASTER-Net observations report
  82. GRB 210427A: Fermi GBM Final Real-time Localization
  83. GRB 210422B: Fermi GBM Final Localization
  84. GRB 210420B: Assy optical observations
  85. Fermi trigger No 640975205: Global MASTER-Net observations report
  86. GRB 210425A: GECAM detection
  87. GRB 210424.694: DDOTI Upper Limits on the Afterglow
  88. GRB 210422A: Swift-BAT refined analysis
  89. GRB 210424A: Fermi GBM Final Real-time Localization
  90. GRB 210420B: follow-up photometry of optical afterglow at INASAN/Simeiz
  91. GRB 210420B: Zeiss-1000 of Koshka optical observations
  92. GRB 210421A: Swift-BAT refined analysis
  93. GRB 210421B: Swift-XRT observations
  94. GRB 210421B: AstroSat CZTI detection
  95. GRB 210420B: continued Tautenburg observations
  96. GRB 210421A: GECAM detection
  97. GRB 210421B: AstroSat CZTI detection
  98. Swift GRB210422.74: Global MASTER-Net observations report
  99. GRB 210422A: Swift detection of a burst
  100. GRB 210421A: Swift/UVOT Upper Limits

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