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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 GRB 210510A: DDOTI Upper Limits on the Afterglow
  2. Fermi GRB 210511B: Global MASTER-Net observations report
  3. GRB 210511B: AGILE detection
  4. GRB 210511B: GECAM detection
  5. GRB 210511B: BALROG localization (Fermi Trigger 642425204 / GRB 210511477)
  6. GRB 210511B: Fermi GBM Final Real-time Localization
  7. GRB 210511A: Fermi GBM Final Real-time Localization
  8. Fermi GRB 210510A: Global MASTER-Net observations report
  9. GRB 201228B: Swift/BAT-GUANO archival detection and arcminute localization
  10. GRB 200716A: Swift/BAT-GUANO archival detection and arcminute localization
  11. Swift trigger 1047857 is 4U 1700-377
  12. IceCube Alert 210510.20: Global MASTER-Net observations report
  13. GRB 210510A: Fermi GBM Final Real-time Localization
  14. IceCube-210510A: DDOTI Upper Limits
  15. GRB 210509A: RATIR Optical and NIR Upper Limits
  16. GRB 210509A: Swift/UVOT Upper Limits
  17. GRB 210509A: Swift-XRT refined Analysis
  18. IceCube-210510A - IceCube observation of a high-energy neutrino candidate track-like event
  19. GRB 210509A: Swift-BAT refined analysis
  20. Swift GRB 210509A: Global MASTER-Net observations report
  21. GRB 210509A: Enhanced Swift-XRT position
  22. GRB 210509A: BOOTES-4/MET optical upper limit
  23. GRB 210509A: Swift-XRT observations
  24. GRB 210509A: Swift detection of a burst
  25. GRB 210506A: Swift/BAT-GUANO position retraction
  26. IPN triangulation of GRB 210506A
  27. HAWC-210507A: No neutrino counterpart candidates in ANTARES search
  28. Fermi GRB 210507A: Global MASTER-Net observations report
  29. Fermi-LAT Gamma-ray Observations of IceCube-210503A and detection of a new gamma-ray source, Fermi J0931.9+3633
  30. ZTF21aayokph (AT2021lfa): continued Mondy optical observations
  31. GRB 210507A: Fermi GBM Final Real-time Localization
  32. Integral GRB210507.04: Global MASTER-Net observations report
  33. Integral GRB210506.78: Global MASTER-Net observations report
  34. GRB 210506A: Swift-XRT observations
  35. ZTF21aayokph (AT2021lfa): MASTER OT detection 3h befor ZTF
  36. Alert from the HAWC Burst Monitor HAWC-210507A
  37. HAWC GRB 210507.443: DDOTI Upper Limit
  38. GRB 210506A: Nanshan/NEXT optical upper limit
  39. GRB 210506A: TNG NIR upper limits
  40. ZTF21aayokph (AT2021lfa): Mondy and Koshka observatory optical observations
  41. ZTF21aayokph (AT2021lfa): X-ray Detection with Swift/XRT
  42. Lowell Discovery Telescope Observations of ZTF21aayokph (AT2021lfa)
  43. IceCube-210503A: IceCube observation of a high-energy neutrino candidate event
  44. ZTF21aayokph (AT2021lfa): Assy optical observations
  45. GRB 210506A: Swift ToO observations
  46. ZTF21aayokph (AT2021lfa): Nanshan/NEXT optical upper limit
  47. GRB 210506A: Swift/BAT-GUANO detection and possible arcminute localization of a short hard burst
  48. GRB 210504A: Lowell Discovery Telescope optical observations
  49. ZTF21aayokph (AT2021lfa): Redshift from Gemini South
  50. GRB 210504A: VLT X-shooter redshift
  51. GRB 210424B: AstroSat CZTI detection
  52. GRB 210504A: Swift-XRT refined Analysis
  53. RATIR Observations of ZTF21aayokph (AT2021lfa)
  54. DDOTI Observations of ZTF21aayokph (AT2021lfa)
  55. GRB 210504A: Swift-BAT refined analysis
  56. ZTF and LT observations of ZTF21aayokph (AT2021lfa), a fast-fading red transient
  57. GRB 210504A: NOT optical afterglow detection
  58. GRB 210504A: MITSuME Akeno optical upper limits
  59. Fermi GRB 210503A: DDOTI Upper Limits on the Afterglow
  60. GRB 210504A: AST3-3 YaoAn Optical Upper Limit
  61. GRB 210504A: Swift/UVOT Detection
  62. GRB 210504A: BOOTES-4/MET optical upper limit
  63. Swift GRB210504.58: Global MASTER-Net observations report
  64. GRB 210504A: update on the BAT trigger time and burst duration
  65. GRB 210504A: Swift detection of a burst
  66. Fermi GRB 210503A: Global MASTER-Net observations report
  67. GRB 210503A: Fermi GBM Final Real-time Localization
  68. Swift GRB210502.74: Global MASTER-Net observations report
  69. Swift Detection of MAXI J1803-298 including an optical counterpart
  70. MAXI GRB210501.83: Global MASTER-Net observations report
  71. Fermi GRB 210501A: Global MASTER-Net observations report
  72. Fermi trigger No 641601187: Global MASTER-Net observations report
  73. GRB 210430A: BOOTES-1 optical limit
  74. GRB 210424B: MITSuME Akeno optical upper limits
  75. GRB 210501A: Fermi GBM Final Real-time Localization
  76. GRB 210430A: Swift-BAT refined analysis
  77. Fermi GRB 210430B: Global MASTER-Net observations report
  78. GRB 210430B: Fermi GBM Final Real-time Localization
  79. Swift GRB210430.45: Global MASTER-Net observations report
  80. GRB 210430A: Swift detection of a burst
  81. GRB 210424B: CALET Gamma-Ray Burst Monitor detection
  82. GRB 210413B: Swift/UVOT Observations
  83. Konus-Wind detection of GRB 210424B
  84. Delayed GRB GCN Notices from Swift
  85. IPN triangulation of GRB 210424B (short/hard)
  86. GRB 210323B: Swift-XRT observations
  87. Swift Trigger 1045571 is not a GRB
  88. GRB 210427A: GECAM detection
  89. GRB 210427A: BALROG localization (Fermi Trigger / GRB 210427206)
  90. Fermi GRB 210427A: Global MASTER-Net observations report
  91. GRB 210427A: Fermi GBM Final Real-time Localization
  92. GRB 210422B: Fermi GBM Final Localization
  93. GRB 210420B: Assy optical observations
  94. Fermi trigger No 640975205: Global MASTER-Net observations report
  95. GRB 210425A: GECAM detection
  96. GRB 210424.694: DDOTI Upper Limits on the Afterglow
  97. GRB 210422A: Swift-BAT refined analysis
  98. GRB 210424A: Fermi GBM Final Real-time Localization
  99. GRB 210420B: follow-up photometry of optical afterglow at INASAN/Simeiz
  100. GRB 210420B: Zeiss-1000 of Koshka optical observations

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