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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. Fermi trigger No 642991619: Global MASTER-Net observations report
  2. Fermi-LAT Gamma-ray Observations of IceCube-210516A
  3. GRB 210518A: Fermi GBM Final Real-time Localization
  4. IceCube Alert 210515.01: Global MASTER-Net observations report
  5. GRB 210517A: Swift-BAT refined analysis
  6. GRB 210517A: Swift-XRT refined Analysis
  7. IceCube-210516A: No significant detection in HAWC
  8. GRB 210517A: Swift/UVOT Upper Limits
  9. GRB 210515C: Swift/UVOT Upper Limits
  10. IceCube-210516A: Upper limits from a search for additional neutrino events in IceCube
  11. GRB 210517A: VLT/X-shooter optical afterglow and redshift
  12. GRB 210517A: AGILE detection
  13. GRB 210514A: CALET Gamma-Ray Burst Monitor detection
  14. GRB 210517A: Enhanced Swift-XRT position
  15. Swift GRB 210517A: Global MASTER-Net observations report
  16. GRB 210517A: Swift detection of a burst
  17. Fermi GRB 210516A: Global MASTER-Net observations report
  18. GRB 210516A: Fermi GBM Final Real-time Localization
  19. IceCube Alert 210516.61: Global MASTER-Net observations report
  20. GRB 210515C: LCO Optical Upper Limit
  21. GRB 210504A: LCO Optical Afterglow Detection
  22. IceCube-210516A - IceCube observation of a high-energy neutrino candidate track-like event
  23. GRB 210514A: Swift/UVOT Upper Limits
  24. AMON IC_HAWC NuEm-210515A / NuEm-210515B : No neutrino counterpart detected with ANTARES
  25. GRB 210515C: Swift-XRT refined Analysis
  26. Swift GRB210515.83: Global MASTER-Net observations report
  27. GRB 210515C: Swift-BAT refined analysis
  28. GRB 210515C: Swift detection of a burst
  29. Fermi GRB 210515B: Global MASTER-Net observations report
  30. GRB 210514A: Swift-BAT refined analysis
  31. Fermi GRB 210515A: Global MASTER-Net observations report
  32. GRB 210515B: Fermi GBM Final Real-time Localization
  33. GRB 210515A: Fermi GBM Final Real-time Localization
  34. Swift GRB210514.71: Global MASTER-Net observations report
  35. GRB 210514A: Swift XRT light curve is fading
  36. GRB 210514A: Swift-XRT refined Analysis
  37. GRB 210514A: Enhanced Swift-XRT position
  38. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEM-210515A and 210515B
  39. GRB 210514A: update on the BAT trigger time and burst duration
  40. GRB 210514A: Swift detection of a burst
  41. Konus-Wind detection of GRB 210511B
  42. GRB 210512.786: DDOTI Upper Limits on the Afterglow
  43. GRB210510A: Optical afterglow candidate from the Zwicky Transient Facility
  44. Fermi trigger No 642538568: Global MASTER-Net observations report
  45. IceCube-210510A: Upper limits from a search for additional neutrino events in IceCube
  46. IPN triangulation of GRB 210511B
  47. IceCube-210510A: not observable by Fermi-GBM
  48. Short GRB 210323A: likely host galaxy detection
  49. IceCube-210510A: No candidate counterparts from the Zwicky Transient Facility
  50. GRB 210511B: DDOTI Upper Limits on the Afterglow
  51. IPN triangulation of GRB 210427A
  52. GRB 210511B: Fermi GBM observation
  53. Fermi-LAT Gamma-ray Observations of IceCube-210510A
  54. Fermi GRB 210511A: Global MASTER-Net observations report
  55. Fermi GRB 210510A: DDOTI Upper Limits on the Afterglow
  56. Fermi GRB 210511B: Global MASTER-Net observations report
  57. GRB 210511B: AGILE detection
  58. GRB 210511B: GECAM detection
  59. GRB 210511B: BALROG localization (Fermi Trigger 642425204 / GRB 210511477)
  60. GRB 210511B: Fermi GBM Final Real-time Localization
  61. GRB 210511A: Fermi GBM Final Real-time Localization
  62. Fermi GRB 210510A: Global MASTER-Net observations report
  63. GRB 201228B: Swift/BAT-GUANO archival detection and arcminute localization
  64. GRB 200716A: Swift/BAT-GUANO archival detection and arcminute localization
  65. Swift trigger 1047857 is 4U 1700-377
  66. IceCube Alert 210510.20: Global MASTER-Net observations report
  67. GRB 210510A: Fermi GBM Final Real-time Localization
  68. IceCube-210510A: DDOTI Upper Limits
  69. GRB 210509A: RATIR Optical and NIR Upper Limits
  70. GRB 210509A: Swift/UVOT Upper Limits
  71. GRB 210509A: Swift-XRT refined Analysis
  72. IceCube-210510A - IceCube observation of a high-energy neutrino candidate track-like event
  73. GRB 210509A: Swift-BAT refined analysis
  74. Swift GRB 210509A: Global MASTER-Net observations report
  75. GRB 210509A: Enhanced Swift-XRT position
  76. GRB 210509A: BOOTES-4/MET optical upper limit
  77. GRB 210509A: Swift-XRT observations
  78. GRB 210509A: Swift detection of a burst
  79. GRB 210506A: Swift/BAT-GUANO position retraction
  80. IPN triangulation of GRB 210506A
  81. HAWC-210507A: No neutrino counterpart candidates in ANTARES search
  82. Fermi GRB 210507A: Global MASTER-Net observations report
  83. Fermi-LAT Gamma-ray Observations of IceCube-210503A and detection of a new gamma-ray source, Fermi J0931.9+3633
  84. ZTF21aayokph (AT2021lfa): continued Mondy optical observations
  85. GRB 210507A: Fermi GBM Final Real-time Localization
  86. Integral GRB210507.04: Global MASTER-Net observations report
  87. Integral GRB210506.78: Global MASTER-Net observations report
  88. GRB 210506A: Swift-XRT observations
  89. ZTF21aayokph (AT2021lfa): MASTER OT detection 3h befor ZTF
  90. Alert from the HAWC Burst Monitor HAWC-210507A
  91. HAWC GRB 210507.443: DDOTI Upper Limit
  92. GRB 210506A: Nanshan/NEXT optical upper limit
  93. GRB 210506A: TNG NIR upper limits
  94. ZTF21aayokph (AT2021lfa): Mondy and Koshka observatory optical observations
  95. ZTF21aayokph (AT2021lfa): X-ray Detection with Swift/XRT
  96. Lowell Discovery Telescope Observations of ZTF21aayokph (AT2021lfa)
  97. IceCube-210503A: IceCube observation of a high-energy neutrino candidate event
  98. ZTF21aayokph (AT2021lfa): Assy optical observations
  99. GRB 210506A: Swift ToO observations
  100. ZTF21aayokph (AT2021lfa): Nanshan/NEXT optical upper limit

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