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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. Baksan Neutrino Observatory Alert 191127.25: Global MASTER-Net observations report
  2. IceCube-191122A: Not observable by Fermi-GBM
  3. IceCube-191122A: Upper limits from a search for additional neutrino events in IceCube
  4. Fermi trigger No 596387570: Global MASTER-Net observations report
  5. GRB 191125B: Fermi GBM Final Real-time Localization
  6. GRB 191125A: Fermi GBM Final Real-time Localization
  7. Baksan Neutrino Observatory Alert 191124.13: Global MASTER-Net observations report
  8. Fermi-LAT Gamma-ray Observations of IceCube-191122A
  9. LIGO/Virgo S191124be: Global MASTER-Net observations report
  10. LIGO/Virgo S191124be: Retraction of GW compact binary merger candidate
  11. GRB 191123A: Swift/UVOT further analysis
  12. GRB 191123A: Swift-BAT refined analysis
  13. GRB 191123A: Swift-XRT refined Analysis
  14. GRB 191123A: Enhanced Swift-XRT position
  15. GRB 191123A: iTelescope optical upper limits
  16. GRB 191123A: Swift/UVOT detection
  17. IceCube-191122A: INTEGRAL was inactive at the time of the event
  18. IceCube-191122A: Global MASTER-Net observations report
  19. GRB 191123A: Swift detection of a burst with an optical counterpart
  20. GRB 191118A: Insight-HXMT/HE detection
  21. GRB 191122A: Swift/UVOT Upper Limits
  22. IceCube-191122A - IceCube observation of a high-energy neutrino candidate event
  23. GRB 191122A: Swift-BAT refined analysis
  24. GRB 191122A: Swift-XRT refined Analysis
  25. GRB 191122A: BOOTES-4/MET optical limit
  26. GRB 191122A: Enhanced Swift-XRT position
  27. GRB 191122A: CHES Optical Observations
  28. GRB 191122A: Prompt enhanced Swift-XRT position
  29. GRB 191122A: Swift detection of a burst
  30. GRB 191119A: AstroSat CZTI detection of a short GRB
  31. IceCube-191119A: No significant detection in HAWC
  32. IceCube-191119A: No neutrino counterpart candidates in ANTARES search
  33. LIGO/Virgo S191120at: Retraction of GW compact binary merger candidate
  34. LIGO/Virgo S191120aj: Global MASTER-Net observations report
  35. LIGO/Virgo S191120aj: Retraction of GW compact binary merger candidate
  36. IceCube-191119A: Upper limits from a search for additional neutrino events in IceCube
  37. Fermi-LAT Gamma-ray Observations of IceCube-191119A
  38. IceCube-191119A: Upper limits from Fermi-GBM Observations
  39. IceCube-191119A - No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  40. IceCube-191119A - IceCube observation of a high-energy neutrino candidate event
  41. GRB 191118A: BALROG localization (Fermi Trigger 595807926 / GRB 191118925)
  42. GRB 191118A: Fermi GBM Final Real-time Localization
  43. GRB 191117B: Fermi GBM Final Real-time Localization
  44. LIGO/Virgo S191117j: Retraction of GW compact binary merger candidate
  45. GRB 191117A: Fermi GBM Final Real-time Localization
  46. Swift Trigger 937114 is not an astrophysical source
  47. Swift GRB191115A: Global MASTER-Net observations report
  48. LIGO/Virgo S191110af: Retraction of GW unmodeled transient candidate
  49. LIGO/Virgo S191110af: Upper limits from KM3NeT MeV neutrino search.
  50. LIGO/Virgo S191110af: Upper limits from Konus-Wind observations
  51. GRB 191111A: Insight-HXMT/HE detection
  52. GRB 191027A: CALET Gamma-Ray Burst Monitor detection
  53. LIGO/Virgo S191105e: Updated Sky Localization
  54. Announcing the GW Treasure Map
  55. LIGO/Virgo S191110af: Potential pulsar counterparts
  56. Konus-Wind observation of the recent SGR 1935+2154 activity
  57. GRB 191113A: Fermi GBM Final Real-time Localization
  58. GRB 191031D: CALET Gamma-Ray Burst Monitor detection
  59. GRB 191112A: Fermi GBM Final Real-time Localization
  60. LIGO/Virgo S191110af: Swift XRT observations, no secure afterglow found
  61. LIGO/Virgo S191110af: Upper limits from CALET observations.
  62. LIGO/Virgo S191109d: Not observable by CALET
  63. LIGO/Virgo S191110af: Upper limits from IceCube MeV neutrino searches
  64. LIGO/Virgo S191110af: no counterpart candidates in the Swift/BAT observations
  65. GRB 191111B: BALROG localization (Fermi Trigger 595170435 / GRB 191111547)
  66. LIGO/Virgo S191110af: No counterpart candidates in INTEGRAL SPI-ACS, and IBIS prompt observation
  67. GRB 191111B: Fermi GBM Final Real-time Localization
  68. LIGO/Virgo S191110af: No neutrino counterpart candidate in ANTARES search
  69. LIGO/Virgo S191110af: No counterpart candidates in Fermi-LAT observations
  70. LIGO/Virgo S191110af: upper limits from AGILE/MCAL observations
  71. LIGO/Virgo S191110af: Evryscope observation report, no counterpart candidates
  72. GRB 191111A: Fermi GBM Final Real-time Localization
  73. LIGO/Virgo S191110af: No counterpart candidates in INTEGRAL SPI-ACS, prompt observation
  74. LIGO/Virgo S191110af: Upper limits from Fermi-GBM Observations
  75. LIGO/Virgo S191110af: Coverage and upper limits from MAXI/GSC observations
  76. LIGO/Virgo S191110af: Identification of a GW unmodeled transient candidate
  77. LIGO/Virgo S191110af: Upper limits from IceCube neutrino searches
  78. LIGO/Virgo S191110af: Global MASTER-Net observations report
  79. LIGO/Virgo S191109d: No significant candidates in FRAM-TAROT-GRANDMA observations
  80. LIGO/Virgo S191110x: Retraction of GW compact binary merger candidate
  81. LIGO/Virgo S191110x: Global MASTER-Net observations report
  82. LIGO/Virgo S191109d: No counterpart candidates in Fermi-LAT observations
  83. LIGO/Virgo S191105e: No significant candidates in FRAM-TAROT-GRANDMA observations
  84. GRB 191110A: Fermi GBM Final Real-time Localization
  85. LIGO/Virgo S191105e: Upper limits from Insight-HXMT/HE observations
  86. LIGO/Virgo S191109d: AstroSat CZTI upper limits
  87. LIGO/Virgo S191109d: no counterpart candidates in the Swift/BAT observations
  88. LIGO/Virgo S191109d : no neutrino counterpart candidate in ANTARES search
  89. LIGO/Virgo S191109d: Global MASTER-Net observations report
  90. LIGO/Virgo S191109d: upper limits from AGILE-GRID observations mailed-by:
  91. LIGO/Virgo S191109d: No counterpart candidates in INTEGRAL SPI-ACS,prompt observation
  92. LIGO/Virgo S191109d: upper limits from AGILE/MCAL observations
  93. LIGO/Virgo S191109d: Upper limits from Fermi-GBM Observations
  94. LIGO/Virgo S191109d: Coverage and upper limits from MAXI/GSC observations
  95. LIGO/Virgo S191109d: Upper limits from IceCube neutrino searches
  96. LIGO/Virgo S191109d: Identification of a GW compact binary merger candidate
  97. GRB 191106A: AstroSat CZTI detection
  98. GRB 191108A: Fermi GBM Final Real-time Localization
  99. GRB 191106A: Swift/UVOT Upper Limits
  100. GRB 191106A: Swift-BAT refined analysis

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