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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. GRB210510A: Optical afterglow candidate from the Zwicky Transient Facility
  2. Fermi trigger No 642538568: Global MASTER-Net observations report
  3. IceCube-210510A: Upper limits from a search for additional neutrino events in IceCube
  4. IPN triangulation of GRB 210511B
  5. IceCube-210510A: not observable by Fermi-GBM
  6. Short GRB 210323A: likely host galaxy detection
  7. IceCube-210510A: No candidate counterparts from the Zwicky Transient Facility
  8. GRB 210511B: DDOTI Upper Limits on the Afterglow
  9. IPN triangulation of GRB 210427A
  10. GRB 210511B: Fermi GBM observation
  11. Fermi-LAT Gamma-ray Observations of IceCube-210510A
  12. Fermi GRB 210511A: Global MASTER-Net observations report
  13. Fermi GRB 210510A: DDOTI Upper Limits on the Afterglow
  14. Fermi GRB 210511B: Global MASTER-Net observations report
  15. GRB 210511B: AGILE detection
  16. GRB 210511B: GECAM detection
  17. GRB 210511B: BALROG localization (Fermi Trigger 642425204 / GRB 210511477)
  18. GRB 210511B: Fermi GBM Final Real-time Localization
  19. GRB 210511A: Fermi GBM Final Real-time Localization
  20. Fermi GRB 210510A: Global MASTER-Net observations report
  21. GRB 201228B: Swift/BAT-GUANO archival detection and arcminute localization
  22. GRB 200716A: Swift/BAT-GUANO archival detection and arcminute localization
  23. Swift trigger 1047857 is 4U 1700-377
  24. IceCube Alert 210510.20: Global MASTER-Net observations report
  25. GRB 210510A: Fermi GBM Final Real-time Localization
  26. IceCube-210510A: DDOTI Upper Limits
  27. GRB 210509A: RATIR Optical and NIR Upper Limits
  28. GRB 210509A: Swift/UVOT Upper Limits
  29. GRB 210509A: Swift-XRT refined Analysis
  30. IceCube-210510A - IceCube observation of a high-energy neutrino candidate track-like event
  31. GRB 210509A: Swift-BAT refined analysis
  32. Swift GRB 210509A: Global MASTER-Net observations report
  33. GRB 210509A: Enhanced Swift-XRT position
  34. GRB 210509A: BOOTES-4/MET optical upper limit
  35. GRB 210509A: Swift-XRT observations
  36. GRB 210509A: Swift detection of a burst
  37. GRB 210506A: Swift/BAT-GUANO position retraction
  38. IPN triangulation of GRB 210506A
  39. HAWC-210507A: No neutrino counterpart candidates in ANTARES search
  40. Fermi GRB 210507A: Global MASTER-Net observations report
  41. Fermi-LAT Gamma-ray Observations of IceCube-210503A and detection of a new gamma-ray source, Fermi J0931.9+3633
  42. ZTF21aayokph (AT2021lfa): continued Mondy optical observations
  43. GRB 210507A: Fermi GBM Final Real-time Localization
  44. Integral GRB210507.04: Global MASTER-Net observations report
  45. Integral GRB210506.78: Global MASTER-Net observations report
  46. GRB 210506A: Swift-XRT observations
  47. ZTF21aayokph (AT2021lfa): MASTER OT detection 3h befor ZTF
  48. Alert from the HAWC Burst Monitor HAWC-210507A
  49. HAWC GRB 210507.443: DDOTI Upper Limit
  50. GRB 210506A: Nanshan/NEXT optical upper limit
  51. GRB 210506A: TNG NIR upper limits
  52. ZTF21aayokph (AT2021lfa): Mondy and Koshka observatory optical observations
  53. ZTF21aayokph (AT2021lfa): X-ray Detection with Swift/XRT
  54. Lowell Discovery Telescope Observations of ZTF21aayokph (AT2021lfa)
  55. IceCube-210503A: IceCube observation of a high-energy neutrino candidate event
  56. ZTF21aayokph (AT2021lfa): Assy optical observations
  57. GRB 210506A: Swift ToO observations
  58. ZTF21aayokph (AT2021lfa): Nanshan/NEXT optical upper limit
  59. GRB 210506A: Swift/BAT-GUANO detection and possible arcminute localization of a short hard burst
  60. GRB 210504A: Lowell Discovery Telescope optical observations
  61. ZTF21aayokph (AT2021lfa): Redshift from Gemini South
  62. GRB 210504A: VLT X-shooter redshift
  63. GRB 210424B: AstroSat CZTI detection
  64. GRB 210504A: Swift-XRT refined Analysis
  65. RATIR Observations of ZTF21aayokph (AT2021lfa)
  66. DDOTI Observations of ZTF21aayokph (AT2021lfa)
  67. GRB 210504A: Swift-BAT refined analysis
  68. ZTF and LT observations of ZTF21aayokph (AT2021lfa), a fast-fading red transient
  69. GRB 210504A: NOT optical afterglow detection
  70. GRB 210504A: MITSuME Akeno optical upper limits
  71. Fermi GRB 210503A: DDOTI Upper Limits on the Afterglow
  72. GRB 210504A: AST3-3 YaoAn Optical Upper Limit
  73. GRB 210504A: Swift/UVOT Detection
  74. GRB 210504A: BOOTES-4/MET optical upper limit
  75. Swift GRB210504.58: Global MASTER-Net observations report
  76. GRB 210504A: update on the BAT trigger time and burst duration
  77. GRB 210504A: Swift detection of a burst
  78. Fermi GRB 210503A: Global MASTER-Net observations report
  79. GRB 210503A: Fermi GBM Final Real-time Localization
  80. Swift GRB210502.74: Global MASTER-Net observations report
  81. Swift Detection of MAXI J1803-298 including an optical counterpart
  82. MAXI GRB210501.83: Global MASTER-Net observations report
  83. Fermi GRB 210501A: Global MASTER-Net observations report
  84. Fermi trigger No 641601187: Global MASTER-Net observations report
  85. GRB 210430A: BOOTES-1 optical limit
  86. GRB 210424B: MITSuME Akeno optical upper limits
  87. GRB 210501A: Fermi GBM Final Real-time Localization
  88. GRB 210430A: Swift-BAT refined analysis
  89. Fermi GRB 210430B: Global MASTER-Net observations report
  90. GRB 210430B: Fermi GBM Final Real-time Localization
  91. Swift GRB210430.45: Global MASTER-Net observations report
  92. GRB 210430A: Swift detection of a burst
  93. GRB 210424B: CALET Gamma-Ray Burst Monitor detection
  94. GRB 210413B: Swift/UVOT Observations
  95. Konus-Wind detection of GRB 210424B
  96. Delayed GRB GCN Notices from Swift
  97. IPN triangulation of GRB 210424B (short/hard)
  98. GRB 210323B: Swift-XRT observations
  99. Swift Trigger 1045571 is not a GRB
  100. GRB 210427A: GECAM detection

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