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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. LIGO/Virgo S190727h: No counterpart candidates in Fermi-LAT observations
  2. LIGO/Virgo S190727h: possible counterpart candidate in SPI-ACS/INTEGRAL
  3. LIGO/Virgo S190727h: Upper limits from Fermi-GBM Observations
  4. LIGO/Virgo S190727h: No counterpart candidates in HAWC observations
  5. LIGO/Virgo S190727h : no neutrino counterpart candidate in ANTARES search
  6. LIGO/Virgo S190727h: No counterpart candidates in AGILE-MCAL observations
  7. LIGO/Virgo S190727h: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  8. LIGO/Virgo S190727h: Coverage and upper limits from MAXI/GSC observations
  9. LIGO/Virgo S190727h: Identification of a GW compact binary merger candidate
  10. LIGO/Virgo S190727h Global MASTER-Net observations report
  11. LIGO/Virgo S190727h: Upper limits from IceCube neutrino searches
  12. Fermi trigger No 585864875 Global MASTER-Net observations report
  13. Fermi trigger No 585847498 Global MASTER-Net observations report
  14. GRB 190726B: BALROG localization (Fermi Trigger 585864875 / GRB 190726843)
  15. GRB 190726B: Fermi GBM Final Real-time Localization
  16. Fermi trigger No 585856427 Global MASTER-Net observations report
  17. GRB 190726A: BALROG localization (Fermi Trigger 585847498 / GRB 190726642)
  18. GRB 190726A: Fermi GBM Final Real-time Localization
  19. LIGO/Virgo S190718y: Classification of AT 2019lqm / Gaia19dcs as a Type Ia Supernova
  20. LIGO/Virgo S190718y: Classification of AT 2019lqn / Gaia19dct as a Type Ia Supernova
  21. LIGO/Virgo S190718y: Swift XRT observations, 45 X-ray sources
  22. GRB 190724A: Insight-HXMT/HE detection
  23. GRB 190723A: Insight-HXMT/HE detection
  24. GRB 190720A: CALET Gamma-Ray Burst Monitor detection
  25. LIGO/Virgo S190720a: Thacher Observatory follow-up observations
  26. IPN triangulation of GRB 190724A (short)
  27. LIGO/Virgo S190718y: Gaia Photometric Alerts transient candidates
  28. GRB 190719C: optical afterglow confirmation
  29. Fermi trigger No 585621841 Global MASTER-Net observations report
  30. GRB 190724A: Fermi GBM Final Real-time Localization
  31. Fermi trigger No 585559462 Global MASTER-Net observations report
  32. GRB 190723A: Fermi GBM Final Real-time Localization
  33. IPN triangulation of GRB 190720A
  34. LIGO/Virgo S190720a: Updated localization from LIGO and Virgo data
  35. GRB 190720B: Insight-HXMT/HE detection
  36. LIGO/Virgo S190720a: No counterpart candidates in CNEOST observations
  37. LIGO/Virgo S190720a: No counterpart candidates in Fermi-LAT observations
  38. LIGO/Virgo S190720a: Upper limits from CALET observations
  39. LIGO/Virgo S190720a: No counterpart candidates in KAIT observations
  40. GRB 190720B: Fermi GBM Final Real-time Localization
  41. GRB 190720A: Fermi GBM detection
  42. GRB 190719C: Fermi GBM detection
  43. GRB 190719C: Swift-BAT refined analysis
  44. GRB 190719C: Swift/UVOT Upper Limits
  45. LIGO/Virgo S190720a: No counterpart candidates in the Swift/BAT Observations
  46. GRB 190719C: Swift-XRT light-curve fit
  47. GRB 190719C: Swift-XRT refined Analysis
  48. GRB 190720A: BALROG localization (Fermi Trigger 585326534 / GRB 190720613)
  49. GRB 190720A: Fermi GBM Final Real-time Localization
  50. LIGO/Virgo S190720a: Upper limits from Fermi-GBM Observations
  51. LIGO/Virgo S190720a: Upper limits from AGILE-GRID observations
  52. LIGO/Virgo S190720a : no neutrino counterpart candidate in ANTARES search
  53. LIGO/Virgo S190720a: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  54. LIGO/Virgo S190720a: Coverage and upper limits from MAXI/GSC observations
  55. LIGO/Virgo S190718y: No counterpart candidates in CNEOST
  56. LIGO/Virgo S190720a: AGILE-MCAL observations
  57. LIGO/Virgo S190720a: Identification of a GW compact binary merger candidate
  58. LIGO/Virgo S190720a Global MASTER-Net observations report
  59. LIGO/Virgo S190720a: No counterpart candidates in HAWC observations
  60. LIGO/Virgo S190720a: Upper limits from IceCube neutrino searches
  61. Fermi trigger No 585196946 Global MASTER-Net observations report
  62. GRB 190719C: NOT candidate optical afterglow and host
  63. LIGO/Virgo S190718y: No counterpart candidates in KAIT observations
  64. LIGO/Virgo S190718y: ZTF pre-detection of MASTER candidate AT2019lly
  65. LIGO/Virgo S190718y: Analysis update
  66. GRB 190719C: Swift detection of a burst
  67. MASTER OT detection inside LIGO/Virgo S190718y error box
  68. GRB 190719C: Fermi GBM Final Real-time Localization
  69. LIGO/Virgo S190718y: Upper limits from Insight-HXMT/HE observations
  70. LIGO/Virgo S190718y: No counterpart candidates in Fermi-LAT observations
  71. GRB 190719B: a long GRB detected by INTEGRAL
  72. LIGO/Virgo S190718y: Coverage and upper limits from MAXI/GSC observations
  73. LIGO/Virgo S190718y: Upper limits from CALET observations
  74. GRB 190719A: Fermi GBM Final Real-time Localization
  75. GRB 190718A: Swift-BAT refined analysis
  76. LIGO/Virgo S190718y: No counterpart candidates in the Swift/BAT Observations
  77. LIGO/Virgo S190718y: Upper limits from Fermi-GBM Observations
  78. LIGO/Virgo S190630ag: Updated sky localization
  79. GRB 190718A: Swift-XRT refined Analysis
  80. LIGO/Virgo S190718y: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  81. LIGO/Virgo S190718y : no neutrino counterpart candidate in ANTARES search
  82. GRB 190718A: Swift/UVOT Upper Limits
  83. LIGO/Virgo S190718y Global MASTER-Net observations report
  84. LIGO/Virgo S190718y: Identification of a GW compact binary merger candidate
  85. LIGO/Virgo S190718y: Upper limits from IceCube neutrino searches
  86. GRB 190718A: FRAM-Auger optical limit
  87. GRB 190718A: Enhanced Swift-XRT position
  88. Swift GRB190718.2 Global MASTER-Net observations report
  89. GRB 190718A: Swift detection of a burst
  90. GRB 190613B: FRAM-Auger afterglow detection
  91. Fermi trigger No 585007213 Global MASTER-Net observations report
  92. GRB 190716A: BALROG localization (Fermi Trigger 585007213 / GRB 190716917)
  93. GRB 190716A: Fermi GBM Final Real-time Localization
  94. Fermi trigger No 584977168 Global MASTER-Net observations report
  95. GRB 190714A: an X-ray flare from 2E 1624.6+1504/UCAC4 525-061488
  96. Fermi trigger No 584929684 Global MASTER-Net observations report
  97. Fermi trigger No 584929684 Global MASTER-Net observations report
  98. GRB 190708B: confirmation of the X-ray afterglow
  99. IceCube-190712A: Upper limits from a search for additional neutrino events in IceCube
  100. Fermi trigger No 584804684 Global MASTER-Net observations report

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