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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 191016A: REM optical observations
  2. GRB 191017B: Swift-XRT refined Analysis
  3. GRB 191016A: Swift-XRT afterglow detection
  4. Fermi trigger No 593045905: Global MASTER-Net observations report
  5. GRB 191016A: Swift/UVOT Detection
  6. GRB 191017C: Fermi GBM Final Real-time Localization
  7. GRB 191017B: Enhanced Swift-XRT position
  8. GRB 191017B: Swift detection of a burst
  9. GRB 191017A: Fermi GBM Final Localization
  10. GRB191016A: MITSuME Okayama optical observation
  11. GRB 191016A: AZT-20 (Assy observatory) optical photometry
  12. GRB 191016A: early time BOOTES Network and follow-up 1.5m OSN optical observations
  13. 191017A: BALROG localization (Fermi Trigger 592997024 / GRB 191017391)
  14. GRB 191016A: RATIR Optical and NIR Observations
  15. Baksan Neutrino Observatory Alert 191016.51: Global MASTER-Net observations report
  16. GRB 191016A: Optical limit by Ondrejov D50
  17. GRB 191016A: Swift-BAT refined analysis
  18. GRB 191016A: KAIT Optical Afterglow Confirmation
  19. GRB 191016A: COATLI Optical Observations and Detection of the Afterglow
  20. Swift GRB191016.17: Global MASTER-Net observations report
  21. GRB 191016A: Swift detection of a burst
  22. Fermi trigger No 592818648: Global MASTER-Net observations report
  23. ANTARES 191011A: MASTER optical observation befor and after trigger
  24. ANTARES 191011A: AMON + ANTARES Identification of a High-Energy Neutrino + Fermi LAT Coincidence
  25. GRB 191009A: AstroSat CZTI detection
  26. GRB 191011A: Swift-BAT refined analysis
  27. GRB 191011A: Swift/UVOT Detection
  28. GRB 191011A: RATIR Optical and NIR Observations
  29. GRB 191011A: Fermi GBM observation
  30. GRB 19011A: Optical Afterglow Detection with LCO
  31. GRB 191011A: Swift-XRT refined Analysis
  32. GRB 191009A: Insight-HXMT/HE detection
  33. GRB 191011A: MASTER OT retraction.
  34. GRB 191011A: Enhanced Swift-XRT position
  35. GRB 191011A: correction of reported magnitudes
  36. GRB 191011A: BALROG localization (Fermi Trigger 592461363 / GRB 191011192)
  37. GRB 191011A: GROND Detection of the Optical/NIR afterglow
  38. GRB 191011A: VLT X-shooter redshift from RRM Observations
  39. Swift GRB191011.19: Global MASTER-Net observations report
  40. Swift GRB191011.19: Global MASTER-Net OT detection
  41. GRB 191011A: Swift detection of a burst with an optical counterpart
  42. GRB 191011A: Fermi GBM Final Real-time Localization
  43. GRB 191009A: BALROG localization (Fermi Trigger 592297741 / GRB 191009298)
  44. GRB 191009A: Fermi GBM Final Real-time Localization
  45. LIGO/Virgo S190930t: Continued Swift observations of AT2019sbk
  46. Fermi trigger No 592211224: Global MASTER-Net observations report
  47. TESS Detection of the Optical Emission from the Possible Untriggered GRB Associated with ZTF19abvizsw
  48. GRB 191004A: CALET Gamma-Ray Burst Monitor detection
  49. Fermi trigger No 592211224: Global MASTER-Net observations report
  50. GRB 191008A: Fermi GBM Final Real-time Localization
  51. GRB 191004B: Swift/UVOT Detection
  52. GRB 191004B: Continued Optical Afterglow Monitoring with LCO
  53. GRB 191004B: Correction to Konus-Wind GCN 25974
  54. Fermi/GBM observation of a bright burst from magnetar SGR 1935+2154
  55. Konus-Wind observation of GRB 191004B
  56. Konus-Wind observation of GRB 191004A
  57. GRB 191004A: Swift/UVOT Detection
  58. GRB 191004A: Optical Detection with LCO
  59. LIGO/Virgo S190930s: no counterpart candidate in the SVOM/GWAC observations
  60. LIGO/Virgo S190930s: Updated Sky Localization
  61. LIGO/Virgo S190930t: Magellan/IMACS imaging of Swift J224718-581442 (AT2019sbk)
  62. LIGO/Virgo S190930t: Swift XRT observations, no secure afterglow found
  63. GRB 190928A: AstroSat CZTI detection
  64. LIGO/Virgo S190930t: Swift discovery of Swift J224718-581442 (AT2019sbk): a fading UV transient with an X-ray counterpart
  65. LIGO/Virgo S190930t: Swift J221951-484240 optical photometry of Chilescope observatory
  66. LIGO/Virgo S190930t: SALT optical spectroscopy of Swift J221951-484240
  67. GRB 191004B: Swift-XRT refined Analysis
  68. GRB 191004B: GROND Detection of the Optical/NIR Afterglow
  69. GRB 191004A: GROND Upper limits
  70. GRB 191004B: COATLI Optical Observations
  71. GRB 191004A: Swift-XRT refined Analysis
  72. GRB 191004B: VLT/X-shooter redshift
  73. GRB 191004B: Swift-BAT refined analysis
  74. GRB 191004B: NOT optical photometry
  75. GRB 191004A: Swift-BAT refined analysis
  76. GRB 191004A: NOT optical upper limits
  77. GRB 191004B: Enhanced Swift-XRT position
  78. GRB 191004A: Enhanced Swift-XRT position
  79. GRB 191004B: Optical Afterglow Detection with LCO
  80. Swift GRB191004.9: Global MASTER-Net OT detection
  81. GRB 191004B: Swift detection of a burst with an optical counterpart
  82. FACT follow-up of IceCube-191001A
  83. GRB 191004A: Swift detection of a burst with an optical detection
  84. Swift GRB191004.75: Global MASTER-Net OT detection
  85. LIGO/Virgo S190930t: AT2019rpn, AT2019rpj CrAO continued optical photometry
  86. GRB 191001A: Swift-XRT observations
  87. LIGO/Virgo S190930t: J-GEM follow-up observation for Swift J221951-484240
  88. GRB 191001B: Optical Upper Limits with LCO
  89. LIGO/Virgo S190930t: Continued Swift/UVOT observations of Swift J221951-484240
  90. GRB 191001A: Fermi GBM observation
  91. GRB 190926A: Upper limit from CAHA 2.2m observation
  92. IceCube-191001A: HAWC follow-up
  93. GRB 190919A: AstroSat CZTI detection
  94. LIGO/Virgo S190930t: Upper limits from Insight-HXMT/HE observations
  95. LIGO/Virgo S190930s: Upper limits from Insight-HXMT/HE observations
  96. Fermi-LAT Gamma-ray Observations of IceCube-191001A
  97. LIGO/Virgo S190930t: Palomar 200-in DBSP spectroscopy of ZTF19acbwaah
  98. GRB 191001B: Swift-BAT refined analysis
  99. IceCube-191001A: Candidate Counterparts with the Zwicky Transient Facility
  100. LIGO/Virgo S190930t: AT2019rpn, AT2019rpj CrAO optical photometry

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