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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 191011A: VLT X-shooter redshift from RRM Observations
  2. Swift GRB191011.19: Global MASTER-Net observations report
  3. Swift GRB191011.19: Global MASTER-Net OT detection
  4. GRB 191011A: Swift detection of a burst with an optical counterpart
  5. GRB 191011A: Fermi GBM Final Real-time Localization
  6. GRB 191009A: BALROG localization (Fermi Trigger 592297741 / GRB 191009298)
  7. GRB 191009A: Fermi GBM Final Real-time Localization
  8. LIGO/Virgo S190930t: Continued Swift observations of AT2019sbk
  9. Fermi trigger No 592211224: Global MASTER-Net observations report
  10. TESS Detection of the Optical Emission from the Possible Untriggered GRB Associated with ZTF19abvizsw
  11. GRB 191004A: CALET Gamma-Ray Burst Monitor detection
  12. Fermi trigger No 592211224: Global MASTER-Net observations report
  13. GRB 191008A: Fermi GBM Final Real-time Localization
  14. GRB 191004B: Swift/UVOT Detection
  15. GRB 191004B: Continued Optical Afterglow Monitoring with LCO
  16. GRB 191004B: Correction to Konus-Wind GCN 25974
  17. Fermi/GBM observation of a bright burst from magnetar SGR 1935+2154
  18. Konus-Wind observation of GRB 191004B
  19. Konus-Wind observation of GRB 191004A
  20. GRB 191004A: Swift/UVOT Detection
  21. GRB 191004A: Optical Detection with LCO
  22. LIGO/Virgo S190930s: no counterpart candidate in the SVOM/GWAC observations
  23. LIGO/Virgo S190930s: Updated Sky Localization
  24. LIGO/Virgo S190930t: Magellan/IMACS imaging of Swift J224718-581442 (AT2019sbk)
  25. LIGO/Virgo S190930t: Swift XRT observations, no secure afterglow found
  26. GRB 190928A: AstroSat CZTI detection
  27. LIGO/Virgo S190930t: Swift discovery of Swift J224718-581442 (AT2019sbk): a fading UV transient with an X-ray counterpart
  28. LIGO/Virgo S190930t: Swift J221951-484240 optical photometry of Chilescope observatory
  29. LIGO/Virgo S190930t: SALT optical spectroscopy of Swift J221951-484240
  30. GRB 191004B: Swift-XRT refined Analysis
  31. GRB 191004B: GROND Detection of the Optical/NIR Afterglow
  32. GRB 191004A: GROND Upper limits
  33. GRB 191004B: COATLI Optical Observations
  34. GRB 191004A: Swift-XRT refined Analysis
  35. GRB 191004B: VLT/X-shooter redshift
  36. GRB 191004B: Swift-BAT refined analysis
  37. GRB 191004B: NOT optical photometry
  38. GRB 191004A: Swift-BAT refined analysis
  39. GRB 191004A: NOT optical upper limits
  40. GRB 191004B: Enhanced Swift-XRT position
  41. GRB 191004A: Enhanced Swift-XRT position
  42. GRB 191004B: Optical Afterglow Detection with LCO
  43. Swift GRB191004.9: Global MASTER-Net OT detection
  44. GRB 191004B: Swift detection of a burst with an optical counterpart
  45. FACT follow-up of IceCube-191001A
  46. GRB 191004A: Swift detection of a burst with an optical detection
  47. Swift GRB191004.75: Global MASTER-Net OT detection
  48. LIGO/Virgo S190930t: AT2019rpn, AT2019rpj CrAO continued optical photometry
  49. GRB 191001A: Swift-XRT observations
  50. LIGO/Virgo S190930t: J-GEM follow-up observation for Swift J221951-484240
  51. GRB 191001B: Optical Upper Limits with LCO
  52. LIGO/Virgo S190930t: Continued Swift/UVOT observations of Swift J221951-484240
  53. GRB 191001A: Fermi GBM observation
  54. GRB 190926A: Upper limit from CAHA 2.2m observation
  55. IceCube-191001A: HAWC follow-up
  56. GRB 190919A: AstroSat CZTI detection
  57. LIGO/Virgo S190930t: Upper limits from Insight-HXMT/HE observations
  58. LIGO/Virgo S190930s: Upper limits from Insight-HXMT/HE observations
  59. Fermi-LAT Gamma-ray Observations of IceCube-191001A
  60. LIGO/Virgo S190930t: Palomar 200-in DBSP spectroscopy of ZTF19acbwaah
  61. GRB 191001B: Swift-BAT refined analysis
  62. IceCube-191001A: Candidate Counterparts with the Zwicky Transient Facility
  63. LIGO/Virgo S190930t: AT2019rpn, AT2019rpj CrAO optical photometry
  64. IceCube-191001A: Not observable by Fermi-GBM
  65. IPN triangulation of GRB 191001A
  66. LIGO/Virgo S190930t: No neutrino candidates at Pierre Auger Observatory
  67. GRB 191001A: Swift ToO observations
  68. LIGO/Virgo S190930t: ATLAS Forced photometry of ZTF19acbpqlh (AT2019rpn)
  69. LIGO/Virgo S190930t: Candidates from ATLAS observations and constraints on AT2019rpr and AT2019rpn
  70. LIGO/Virgo S190930t: Palomar 200-in DBSP follow-up of ZTF19acbpqlh and ATLAS19wyn
  71. LIGO/Virgo S190930t: J-GEM follow-up observations for AT2019rpj
  72. GRB 191001A: KAIT Optical Upper Limit
  73. GRB 191001A: RATIR Optical and NIR Observations
  74. LIGO/Virgo S190930t: HCT observations of ZTF19acbpsuf
  75. LIGO/Virgo S190930t: Lulin Follow-up Observations of AT2019rpn and AT2019rpj
  76. LIGO/Virgo S190930s: no counterpart candidates in SAGUARO/CSS observations
  77. IceCube-191001A: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  78. IceCube-191001A - IceCube observation of a high-energy neutrino candidate event
  79. LIGO/Virgo S190930s: No counterpart candidates in KAIT observations
  80. GRB 191001A: DDOTI Optical Counterpart Candidate
  81. IceCube Alert 191001.84: Global MASTER-Net observations report
  82. LIGO/Virgo S190924h: Correction to GCN 25905, updated sky localization for S190924h
  83. LIGO/Virgo S190930t and S190930s: MASTER OT J205529.78+220725.5/AT2019rpr further analysis
  84. LIGO/Virgo S190930t: Upper limits on the two of the ZTF/GROWTH candidates
  85. GRB 191001B: MITSuME Akeno optical upper limits
  86. LIGO/Virgo S190828h: Updated Sky Localization
  87. LIGO/Virgo S190814bv: VLA 6 GHz observations of 75 galaxies in the 90% localization region
  88. LIGO/Virgo S190923y: optical spectrum of MASTER detected transient
  89. GRB 191001B: Swift detection of a burst
  90. LIGO/Virgo S190930t: Transient found in Swift/UVOT counterpart search
  91. LIGO/Virgo S190930t and S190930s: MASTER PSN in unknown disk galaxy
  92. LIGO/Virgo S190930t: Candidates from the Zwicky Transient Facility
  93. LIGO/Virgo S190930t: No counterpart candidates in Fermi-LAT observations
  94. LIGO/Virgo S190930t and S190930s: MASTER optical observation and optical transient
  95. Fermi trigger No 591604915: Global MASTER-Net observations report
  96. LIGO/Virgo S190930s: No counterpart candidates in Fermi-LAT observations
  97. GRB 191001A: BALROG localization (Fermi Trigger 591604915 / GRB 191001279)
  98. GRB 191001A: Fermi GBM Final Real-time Localization
  99. LIGO/Virgo S190930t: Upper limits from CALET observations.
  100. LIGO/Virgo S190930s: Upper limits from CALET observations.

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