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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 191009A: Insight-HXMT/HE detection
  2. GRB 191011A: MASTER OT retraction.
  3. GRB 191011A: Enhanced Swift-XRT position
  4. GRB 191011A: correction of reported magnitudes
  5. GRB 191011A: BALROG localization (Fermi Trigger 592461363 / GRB 191011192)
  6. GRB 191011A: GROND Detection of the Optical/NIR afterglow
  7. GRB 191011A: VLT X-shooter redshift from RRM Observations
  8. Swift GRB191011.19: Global MASTER-Net observations report
  9. Swift GRB191011.19: Global MASTER-Net OT detection
  10. GRB 191011A: Swift detection of a burst with an optical counterpart
  11. GRB 191011A: Fermi GBM Final Real-time Localization
  12. GRB 191009A: BALROG localization (Fermi Trigger 592297741 / GRB 191009298)
  13. GRB 191009A: Fermi GBM Final Real-time Localization
  14. LIGO/Virgo S190930t: Continued Swift observations of AT2019sbk
  15. Fermi trigger No 592211224: Global MASTER-Net observations report
  16. TESS Detection of the Optical Emission from the Possible Untriggered GRB Associated with ZTF19abvizsw
  17. GRB 191004A: CALET Gamma-Ray Burst Monitor detection
  18. Fermi trigger No 592211224: Global MASTER-Net observations report
  19. GRB 191008A: Fermi GBM Final Real-time Localization
  20. GRB 191004B: Swift/UVOT Detection
  21. GRB 191004B: Continued Optical Afterglow Monitoring with LCO
  22. GRB 191004B: Correction to Konus-Wind GCN 25974
  23. Fermi/GBM observation of a bright burst from magnetar SGR 1935+2154
  24. Konus-Wind observation of GRB 191004B
  25. Konus-Wind observation of GRB 191004A
  26. GRB 191004A: Swift/UVOT Detection
  27. GRB 191004A: Optical Detection with LCO
  28. LIGO/Virgo S190930s: no counterpart candidate in the SVOM/GWAC observations
  29. LIGO/Virgo S190930s: Updated Sky Localization
  30. LIGO/Virgo S190930t: Magellan/IMACS imaging of Swift J224718-581442 (AT2019sbk)
  31. LIGO/Virgo S190930t: Swift XRT observations, no secure afterglow found
  32. GRB 190928A: AstroSat CZTI detection
  33. LIGO/Virgo S190930t: Swift discovery of Swift J224718-581442 (AT2019sbk): a fading UV transient with an X-ray counterpart
  34. LIGO/Virgo S190930t: Swift J221951-484240 optical photometry of Chilescope observatory
  35. LIGO/Virgo S190930t: SALT optical spectroscopy of Swift J221951-484240
  36. GRB 191004B: Swift-XRT refined Analysis
  37. GRB 191004B: GROND Detection of the Optical/NIR Afterglow
  38. GRB 191004A: GROND Upper limits
  39. GRB 191004B: COATLI Optical Observations
  40. GRB 191004A: Swift-XRT refined Analysis
  41. GRB 191004B: VLT/X-shooter redshift
  42. GRB 191004B: Swift-BAT refined analysis
  43. GRB 191004B: NOT optical photometry
  44. GRB 191004A: Swift-BAT refined analysis
  45. GRB 191004A: NOT optical upper limits
  46. GRB 191004B: Enhanced Swift-XRT position
  47. GRB 191004A: Enhanced Swift-XRT position
  48. GRB 191004B: Optical Afterglow Detection with LCO
  49. Swift GRB191004.9: Global MASTER-Net OT detection
  50. GRB 191004B: Swift detection of a burst with an optical counterpart
  51. FACT follow-up of IceCube-191001A
  52. GRB 191004A: Swift detection of a burst with an optical detection
  53. Swift GRB191004.75: Global MASTER-Net OT detection
  54. LIGO/Virgo S190930t: AT2019rpn, AT2019rpj CrAO continued optical photometry
  55. GRB 191001A: Swift-XRT observations
  56. LIGO/Virgo S190930t: J-GEM follow-up observation for Swift J221951-484240
  57. GRB 191001B: Optical Upper Limits with LCO
  58. LIGO/Virgo S190930t: Continued Swift/UVOT observations of Swift J221951-484240
  59. GRB 191001A: Fermi GBM observation
  60. GRB 190926A: Upper limit from CAHA 2.2m observation
  61. IceCube-191001A: HAWC follow-up
  62. GRB 190919A: AstroSat CZTI detection
  63. LIGO/Virgo S190930t: Upper limits from Insight-HXMT/HE observations
  64. LIGO/Virgo S190930s: Upper limits from Insight-HXMT/HE observations
  65. Fermi-LAT Gamma-ray Observations of IceCube-191001A
  66. LIGO/Virgo S190930t: Palomar 200-in DBSP spectroscopy of ZTF19acbwaah
  67. GRB 191001B: Swift-BAT refined analysis
  68. IceCube-191001A: Candidate Counterparts with the Zwicky Transient Facility
  69. LIGO/Virgo S190930t: AT2019rpn, AT2019rpj CrAO optical photometry
  70. IceCube-191001A: Not observable by Fermi-GBM
  71. IPN triangulation of GRB 191001A
  72. LIGO/Virgo S190930t: No neutrino candidates at Pierre Auger Observatory
  73. GRB 191001A: Swift ToO observations
  74. LIGO/Virgo S190930t: ATLAS Forced photometry of ZTF19acbpqlh (AT2019rpn)
  75. LIGO/Virgo S190930t: Candidates from ATLAS observations and constraints on AT2019rpr and AT2019rpn
  76. LIGO/Virgo S190930t: Palomar 200-in DBSP follow-up of ZTF19acbpqlh and ATLAS19wyn
  77. LIGO/Virgo S190930t: J-GEM follow-up observations for AT2019rpj
  78. GRB 191001A: KAIT Optical Upper Limit
  79. GRB 191001A: RATIR Optical and NIR Observations
  80. LIGO/Virgo S190930t: HCT observations of ZTF19acbpsuf
  81. LIGO/Virgo S190930t: Lulin Follow-up Observations of AT2019rpn and AT2019rpj
  82. LIGO/Virgo S190930s: no counterpart candidates in SAGUARO/CSS observations
  83. IceCube-191001A: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  84. IceCube-191001A - IceCube observation of a high-energy neutrino candidate event
  85. LIGO/Virgo S190930s: No counterpart candidates in KAIT observations
  86. GRB 191001A: DDOTI Optical Counterpart Candidate
  87. IceCube Alert 191001.84: Global MASTER-Net observations report
  88. LIGO/Virgo S190924h: Correction to GCN 25905, updated sky localization for S190924h
  89. LIGO/Virgo S190930t and S190930s: MASTER OT J205529.78+220725.5/AT2019rpr further analysis
  90. LIGO/Virgo S190930t: Upper limits on the two of the ZTF/GROWTH candidates
  91. GRB 191001B: MITSuME Akeno optical upper limits
  92. LIGO/Virgo S190828h: Updated Sky Localization
  93. LIGO/Virgo S190814bv: VLA 6 GHz observations of 75 galaxies in the 90% localization region
  94. LIGO/Virgo S190923y: optical spectrum of MASTER detected transient
  95. GRB 191001B: Swift detection of a burst
  96. LIGO/Virgo S190930t: Transient found in Swift/UVOT counterpart search
  97. LIGO/Virgo S190930t and S190930s: MASTER PSN in unknown disk galaxy
  98. LIGO/Virgo S190930t: Candidates from the Zwicky Transient Facility
  99. LIGO/Virgo S190930t: No counterpart candidates in Fermi-LAT observations
  100. LIGO/Virgo S190930t and S190930s: MASTER optical observation and optical transient

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