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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 210514A: update on the BAT trigger time and burst duration
  2. GRB 210514A: Swift detection of a burst
  3. Konus-Wind detection of GRB 210511B
  4. GRB 210512.786: DDOTI Upper Limits on the Afterglow
  5. GRB210510A: Optical afterglow candidate from the Zwicky Transient Facility
  6. Fermi trigger No 642538568: Global MASTER-Net observations report
  7. IceCube-210510A: Upper limits from a search for additional neutrino events in IceCube
  8. IPN triangulation of GRB 210511B
  9. IceCube-210510A: not observable by Fermi-GBM
  10. Short GRB 210323A: likely host galaxy detection
  11. IceCube-210510A: No candidate counterparts from the Zwicky Transient Facility
  12. GRB 210511B: DDOTI Upper Limits on the Afterglow
  13. IPN triangulation of GRB 210427A
  14. GRB 210511B: Fermi GBM observation
  15. Fermi-LAT Gamma-ray Observations of IceCube-210510A
  16. Fermi GRB 210511A: Global MASTER-Net observations report
  17. Fermi GRB 210510A: DDOTI Upper Limits on the Afterglow
  18. Fermi GRB 210511B: Global MASTER-Net observations report
  19. GRB 210511B: AGILE detection
  20. GRB 210511B: GECAM detection
  21. GRB 210511B: BALROG localization (Fermi Trigger 642425204 / GRB 210511477)
  22. GRB 210511B: Fermi GBM Final Real-time Localization
  23. GRB 210511A: Fermi GBM Final Real-time Localization
  24. Fermi GRB 210510A: Global MASTER-Net observations report
  25. GRB 201228B: Swift/BAT-GUANO archival detection and arcminute localization
  26. GRB 200716A: Swift/BAT-GUANO archival detection and arcminute localization
  27. Swift trigger 1047857 is 4U 1700-377
  28. IceCube Alert 210510.20: Global MASTER-Net observations report
  29. GRB 210510A: Fermi GBM Final Real-time Localization
  30. IceCube-210510A: DDOTI Upper Limits
  31. GRB 210509A: RATIR Optical and NIR Upper Limits
  32. GRB 210509A: Swift/UVOT Upper Limits
  33. GRB 210509A: Swift-XRT refined Analysis
  34. IceCube-210510A - IceCube observation of a high-energy neutrino candidate track-like event
  35. GRB 210509A: Swift-BAT refined analysis
  36. Swift GRB 210509A: Global MASTER-Net observations report
  37. GRB 210509A: Enhanced Swift-XRT position
  38. GRB 210509A: BOOTES-4/MET optical upper limit
  39. GRB 210509A: Swift-XRT observations
  40. GRB 210509A: Swift detection of a burst
  41. GRB 210506A: Swift/BAT-GUANO position retraction
  42. IPN triangulation of GRB 210506A
  43. HAWC-210507A: No neutrino counterpart candidates in ANTARES search
  44. Fermi GRB 210507A: Global MASTER-Net observations report
  45. Fermi-LAT Gamma-ray Observations of IceCube-210503A and detection of a new gamma-ray source, Fermi J0931.9+3633
  46. ZTF21aayokph (AT2021lfa): continued Mondy optical observations
  47. GRB 210507A: Fermi GBM Final Real-time Localization
  48. Integral GRB210507.04: Global MASTER-Net observations report
  49. Integral GRB210506.78: Global MASTER-Net observations report
  50. GRB 210506A: Swift-XRT observations
  51. ZTF21aayokph (AT2021lfa): MASTER OT detection 3h befor ZTF
  52. Alert from the HAWC Burst Monitor HAWC-210507A
  53. HAWC GRB 210507.443: DDOTI Upper Limit
  54. GRB 210506A: Nanshan/NEXT optical upper limit
  55. GRB 210506A: TNG NIR upper limits
  56. ZTF21aayokph (AT2021lfa): Mondy and Koshka observatory optical observations
  57. ZTF21aayokph (AT2021lfa): X-ray Detection with Swift/XRT
  58. Lowell Discovery Telescope Observations of ZTF21aayokph (AT2021lfa)
  59. IceCube-210503A: IceCube observation of a high-energy neutrino candidate event
  60. ZTF21aayokph (AT2021lfa): Assy optical observations
  61. GRB 210506A: Swift ToO observations
  62. ZTF21aayokph (AT2021lfa): Nanshan/NEXT optical upper limit
  63. GRB 210506A: Swift/BAT-GUANO detection and possible arcminute localization of a short hard burst
  64. GRB 210504A: Lowell Discovery Telescope optical observations
  65. ZTF21aayokph (AT2021lfa): Redshift from Gemini South
  66. GRB 210504A: VLT X-shooter redshift
  67. GRB 210424B: AstroSat CZTI detection
  68. GRB 210504A: Swift-XRT refined Analysis
  69. RATIR Observations of ZTF21aayokph (AT2021lfa)
  70. DDOTI Observations of ZTF21aayokph (AT2021lfa)
  71. GRB 210504A: Swift-BAT refined analysis
  72. ZTF and LT observations of ZTF21aayokph (AT2021lfa), a fast-fading red transient
  73. GRB 210504A: NOT optical afterglow detection
  74. GRB 210504A: MITSuME Akeno optical upper limits
  75. Fermi GRB 210503A: DDOTI Upper Limits on the Afterglow
  76. GRB 210504A: AST3-3 YaoAn Optical Upper Limit
  77. GRB 210504A: Swift/UVOT Detection
  78. GRB 210504A: BOOTES-4/MET optical upper limit
  79. Swift GRB210504.58: Global MASTER-Net observations report
  80. GRB 210504A: update on the BAT trigger time and burst duration
  81. GRB 210504A: Swift detection of a burst
  82. Fermi GRB 210503A: Global MASTER-Net observations report
  83. GRB 210503A: Fermi GBM Final Real-time Localization
  84. Swift GRB210502.74: Global MASTER-Net observations report
  85. Swift Detection of MAXI J1803-298 including an optical counterpart
  86. MAXI GRB210501.83: Global MASTER-Net observations report
  87. Fermi GRB 210501A: Global MASTER-Net observations report
  88. Fermi trigger No 641601187: Global MASTER-Net observations report
  89. GRB 210430A: BOOTES-1 optical limit
  90. GRB 210424B: MITSuME Akeno optical upper limits
  91. GRB 210501A: Fermi GBM Final Real-time Localization
  92. GRB 210430A: Swift-BAT refined analysis
  93. Fermi GRB 210430B: Global MASTER-Net observations report
  94. GRB 210430B: Fermi GBM Final Real-time Localization
  95. Swift GRB210430.45: Global MASTER-Net observations report
  96. GRB 210430A: Swift detection of a burst
  97. GRB 210424B: CALET Gamma-Ray Burst Monitor detection
  98. GRB 210413B: Swift/UVOT Observations
  99. Konus-Wind detection of GRB 210424B
  100. Delayed GRB GCN Notices from Swift

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