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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 201020A: Fermi GBM observation
  2. GRB 201020A: Swift-BAT refined analysis
  3. Fermi GRB 201020B: Global MASTER-Net observations report
  4. GRB 201020A: Assy optical observations
  5. GRB 201020B: Fermi GBM Final Real-time Localization
  6. GRB 201020A: Nanshan/NEXT optical observations
  7. Swift GRB 201020A: Global MASTER-Net observations report
  8. GRB 201014A: SAO RAS optical observations
  9. GRB 201020A: Enhanced Swift-XRT position
  10. GRB 201020A: MITSuME Akeno optical observation
  11. GRB 201020A: Swift detection of a burst with an optical counterpart.
  12. GRB 201019B: AstroSat CZTI detection
  13. GRB 201016A: Insight-HXMT/HE detection
  14. GRB 201017A iTelescope observation
  15. GRB 201017A: SAO RAS optical observations
  16. GRB 201017A: GROWTH-India optical upper limit
  17. GRB 201019B: Fermi GBM correction to GCN 28687
  18. GRB 201014A: 3.6m DOT Optical Observations
  19. GRB 201015A: 6 GHz VLA radio afterglow candidate detection
  20. GRB 201019A: Fermi GBM Final Real-time Localization
  21. GRB 201013A: 3.6m DOT Optical Observations
  22. GRB 201014A: MMT afterglow detection
  23. GRB 201017A: MITSuME Akeno optical upper limits
  24. GRB 201019A: Fermi GBM Final Real-time Localization
  25. GRB 201017A: Swift-BAT refined analysis
  26. GRB 201015A: GROWTH-India Telescope (GIT) upper limit
  27. GRB 201015A: HCT optical photometric follow-up
  28. GRB 201017A: Assy and Mondy optical observations, possible afterglow detection
  29. GRB 201017A: Swift-XRT refined Analysis
  30. GRB 201015A: Xinglong-2.16m optical observations
  31. GRB 201015A: MMT afterglow imaging
  32. GRB 201017A: Fermi GBM detection
  33. GRB 201015A NUTTelA-TAO / BSTI Early Measurements (Preliminary)
  34. GRB 201015A: Assy and Mondy optical observations
  35. GRB 201017A: Xinglong TNT upper limit
  36. GRB 201017A: Enhanced Swift-XRT position
  37. Trigger 1000631: Swift detection of Cen X-3
  38. GRB 201015A: classification as long GRB
  39. Swift GRB 201017A: Global MASTER-Net observations report
  40. GRB 201017A: Swift detection of a burst
  41. GRB 201017A: Fermi GBM Final Real-time Localization
  42. GRB 201015A: FRAM-ORM afterglow detection
  43. Fermi GBM Sub-Threshold Detection of GRB 201015A
  44. GRB 201015A: Swift/UVOT Detection
  45. GRB 201015A: redshift confirmation
  46. GRB 201015A: Swift-XRT refined Analysis
  47. MAGIC observations of GRB 201015A: hint of very high energy gamma-ray signal
  48. GRB 201015A: Swift-BAT refined analysis (a soft short pulse with a tail emission)
  49. IceCube-201014A: No significant detection in HAWC
  50. GRB 201015A: CrAO/ZTSH optical observations
  51. GRB 201014A: Nanshan/NEXT optical observations
  52. GRB 201014A: Lowell Discovery Telescope afterglow imaging
  53. GRB201015A: Nanshan/NEXT early optical observations
  54. Konus-Wind observation of GRB 201013A
  55. GRB 201016A: AstroSat CZTI detection
  56. GRB 201014A: Redshift from GTC/OSIRIS
  57. GRB 201015A: Redshift from GTC/OSIRIS
  58. GRB 201008A: Swift-XRT afterglow detection
  59. GRB 201015A: Enhanced Swift-XRT position
  60. GRB 201016A: Fermi GBM detection
  61. GRB 201015A: BOOTES-1 early optical afterglow detection
  62. GRB 201014A: Swift/UVOT Upper Limits
  63. Fermi GRB 201016B: Global MASTER-Net observations report
  64. GRB 201016B: BALROG localization (Fermi Trigger 624510986 / GRB 201016136)
  65. GRB 201016A: BALROG localization (Fermi Trigger 624500874 / GRB 201016019)
  66. GRB 201016B: Fermi GBM Final Real-time Localization
  67. GRB 201015A: GOTO confirmation of afterglow detection
  68. GRB 201014A: Swift-XRT refined Analysis
  69. GRB 201015A: NOT optical afterglow confirmation
  70. GRB 201016A: Fermi GBM Final Real-time Localization
  71. GRB 201015A: Swift-XRT observations
  72. Swift GRB 201015A: Global MASTER-Net observations report
  73. Swift GRB201015.95: Global MASTER-Net OT detection
  74. GRB 201015A: Swift detection of a burst
  75. IceCube-201014A: Upper limits from a search for additional neutrino events in IceCube
  76. GRB 201014A: BOOTES-1 and -2 early optical upper limits
  77. GRB 201014A: Swift-BAT refined analysis
  78. GRB 201014A (Swift trigger =1000255): CrAO/ZTSH optical afterglow discovery
  79. IceCube Alert 201014.09: Global MASTER-Net observations report
  80. Swift-BAT trigger 1000255: XRT afterglow detection of GRB 201014A
  81. GRB 201013A: Insight-HXMT/HE detection
  82. IceCube-201014A: No neutrino counterpart candidates in ANTARES search
  83. Swift Trigger 1000255 is probably not a GRB
  84. Fermi-LAT Gamma-ray Observations of IceCube-201014A
  85. GRB 201013A: TSHAO and AbAO optical observations, afterglow confirmation
  86. GRB 201013A: AstroSat CZTI detection
  87. IceCube-201014A: Not observable by GBM
  88. GRB 201013A: CALET Gamma-Ray Burst Monitor detection
  89. IceCube-201014A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  90. IceCube-201014A - IceCube observation of a high-energy neutrino candidate track-like event
  91. GRB 201013A: FRAM-ORM possible afterglow candidate
  92. GRB 201013A: Swift-BAT refined analysis
  93. GRB 201013A: Swift/UVOT Upper Limits
  94. Swift GRB 201013A: Global MASTER-Net observations report
  95. GRB 201013A: Swift-XRT refined Analysis
  96. SGR 1830-0645: Swift/UVOT Upper Limits
  97. IceCube-201007A: No candidate counterparts from the Zwicky Transient Facility
  98. GRB 201013A: Enhanced Swift-XRT position
  99. GRB 201013A: Swift detection of a burst
  100. GRB 201011A: Fermi GBM detection of a likely Long GRB in the direction of SGR 1830-0645

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