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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. IceCube-210516A - IceCube observation of a high-energy neutrino candidate track-like event
  2. GRB 210514A: Swift/UVOT Upper Limits
  3. AMON IC_HAWC NuEm-210515A / NuEm-210515B : No neutrino counterpart detected with ANTARES
  4. GRB 210515C: Swift-XRT refined Analysis
  5. Swift GRB210515.83: Global MASTER-Net observations report
  6. GRB 210515C: Swift-BAT refined analysis
  7. GRB 210515C: Swift detection of a burst
  8. Fermi GRB 210515B: Global MASTER-Net observations report
  9. GRB 210514A: Swift-BAT refined analysis
  10. Fermi GRB 210515A: Global MASTER-Net observations report
  11. GRB 210515B: Fermi GBM Final Real-time Localization
  12. GRB 210515A: Fermi GBM Final Real-time Localization
  13. Swift GRB210514.71: Global MASTER-Net observations report
  14. GRB 210514A: Swift XRT light curve is fading
  15. GRB 210514A: Swift-XRT refined Analysis
  16. GRB 210514A: Enhanced Swift-XRT position
  17. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEM-210515A and 210515B
  18. GRB 210514A: update on the BAT trigger time and burst duration
  19. GRB 210514A: Swift detection of a burst
  20. Konus-Wind detection of GRB 210511B
  21. GRB 210512.786: DDOTI Upper Limits on the Afterglow
  22. GRB210510A: Optical afterglow candidate from the Zwicky Transient Facility
  23. Fermi trigger No 642538568: Global MASTER-Net observations report
  24. IceCube-210510A: Upper limits from a search for additional neutrino events in IceCube
  25. IPN triangulation of GRB 210511B
  26. IceCube-210510A: not observable by Fermi-GBM
  27. Short GRB 210323A: likely host galaxy detection
  28. IceCube-210510A: No candidate counterparts from the Zwicky Transient Facility
  29. GRB 210511B: DDOTI Upper Limits on the Afterglow
  30. IPN triangulation of GRB 210427A
  31. GRB 210511B: Fermi GBM observation
  32. Fermi-LAT Gamma-ray Observations of IceCube-210510A
  33. Fermi GRB 210511A: Global MASTER-Net observations report
  34. Fermi GRB 210510A: DDOTI Upper Limits on the Afterglow
  35. Fermi GRB 210511B: Global MASTER-Net observations report
  36. GRB 210511B: AGILE detection
  37. GRB 210511B: GECAM detection
  38. GRB 210511B: BALROG localization (Fermi Trigger 642425204 / GRB 210511477)
  39. GRB 210511B: Fermi GBM Final Real-time Localization
  40. GRB 210511A: Fermi GBM Final Real-time Localization
  41. Fermi GRB 210510A: Global MASTER-Net observations report
  42. GRB 201228B: Swift/BAT-GUANO archival detection and arcminute localization
  43. GRB 200716A: Swift/BAT-GUANO archival detection and arcminute localization
  44. Swift trigger 1047857 is 4U 1700-377
  45. IceCube Alert 210510.20: Global MASTER-Net observations report
  46. GRB 210510A: Fermi GBM Final Real-time Localization
  47. IceCube-210510A: DDOTI Upper Limits
  48. GRB 210509A: RATIR Optical and NIR Upper Limits
  49. GRB 210509A: Swift/UVOT Upper Limits
  50. GRB 210509A: Swift-XRT refined Analysis
  51. IceCube-210510A - IceCube observation of a high-energy neutrino candidate track-like event
  52. GRB 210509A: Swift-BAT refined analysis
  53. Swift GRB 210509A: Global MASTER-Net observations report
  54. GRB 210509A: Enhanced Swift-XRT position
  55. GRB 210509A: BOOTES-4/MET optical upper limit
  56. GRB 210509A: Swift-XRT observations
  57. GRB 210509A: Swift detection of a burst
  58. GRB 210506A: Swift/BAT-GUANO position retraction
  59. IPN triangulation of GRB 210506A
  60. HAWC-210507A: No neutrino counterpart candidates in ANTARES search
  61. Fermi GRB 210507A: Global MASTER-Net observations report
  62. Fermi-LAT Gamma-ray Observations of IceCube-210503A and detection of a new gamma-ray source, Fermi J0931.9+3633
  63. ZTF21aayokph (AT2021lfa): continued Mondy optical observations
  64. GRB 210507A: Fermi GBM Final Real-time Localization
  65. Integral GRB210507.04: Global MASTER-Net observations report
  66. Integral GRB210506.78: Global MASTER-Net observations report
  67. GRB 210506A: Swift-XRT observations
  68. ZTF21aayokph (AT2021lfa): MASTER OT detection 3h befor ZTF
  69. Alert from the HAWC Burst Monitor HAWC-210507A
  70. HAWC GRB 210507.443: DDOTI Upper Limit
  71. GRB 210506A: Nanshan/NEXT optical upper limit
  72. GRB 210506A: TNG NIR upper limits
  73. ZTF21aayokph (AT2021lfa): Mondy and Koshka observatory optical observations
  74. ZTF21aayokph (AT2021lfa): X-ray Detection with Swift/XRT
  75. Lowell Discovery Telescope Observations of ZTF21aayokph (AT2021lfa)
  76. IceCube-210503A: IceCube observation of a high-energy neutrino candidate event
  77. ZTF21aayokph (AT2021lfa): Assy optical observations
  78. GRB 210506A: Swift ToO observations
  79. ZTF21aayokph (AT2021lfa): Nanshan/NEXT optical upper limit
  80. GRB 210506A: Swift/BAT-GUANO detection and possible arcminute localization of a short hard burst
  81. GRB 210504A: Lowell Discovery Telescope optical observations
  82. ZTF21aayokph (AT2021lfa): Redshift from Gemini South
  83. GRB 210504A: VLT X-shooter redshift
  84. GRB 210424B: AstroSat CZTI detection
  85. GRB 210504A: Swift-XRT refined Analysis
  86. RATIR Observations of ZTF21aayokph (AT2021lfa)
  87. DDOTI Observations of ZTF21aayokph (AT2021lfa)
  88. GRB 210504A: Swift-BAT refined analysis
  89. ZTF and LT observations of ZTF21aayokph (AT2021lfa), a fast-fading red transient
  90. GRB 210504A: NOT optical afterglow detection
  91. GRB 210504A: MITSuME Akeno optical upper limits
  92. Fermi GRB 210503A: DDOTI Upper Limits on the Afterglow
  93. GRB 210504A: AST3-3 YaoAn Optical Upper Limit
  94. GRB 210504A: Swift/UVOT Detection
  95. GRB 210504A: BOOTES-4/MET optical upper limit
  96. Swift GRB210504.58: Global MASTER-Net observations report
  97. GRB 210504A: update on the BAT trigger time and burst duration
  98. GRB 210504A: Swift detection of a burst
  99. Fermi GRB 210503A: Global MASTER-Net observations report
  100. GRB 210503A: Fermi GBM Final Real-time Localization

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