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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 S190728q: Optical Candidate from the Zwicky Transient Facility ZTF19abjethn
  2. LIGO/Virgo S190728q: No counterpart candidates in Fermi-LAT observations
  3. LIGO/Virgo S190728q: Second update on neutrino search with IceCube
  4. LIGO/Virgo S190728q: Upper limits from Fermi-GBM Observations
  5. LIGO/Virgo S190728q: no counterpart candidates in AGILE-GRID observations
  6. LIGO/Virgo S190728q : no neutrino counterpart candidate in ANTARES search
  7. LIGO/Virgo S190728q: No counterpart candidates in AGILE-MCAL observations
  8. LIGO/Virgo S190728q: One neutrino candidate from IceCube search
  9. LIGO/Virgo S190728q: No counterpart candidates in HAWC observations
  10. LIGO/Virgo S190728q: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  11. LIGO/Virgo S190728q: SPI-ACS/INTEGRAL data analysis
  12. LIGO/Virgo S190728q: Coverage and upper limits from MAXI/GSC observations
  13. LIGO/Virgo S190728q: Identification of a GW compact binary merger candidate
  14. GRB 190727B: Fermi-LAT detection
  15. LIGO/Virgo S190728q: Upper limits from IceCube neutrino searches
  16. LIGO/Virgo S190727h: No transient candidates in CALET observations
  17. LIGO/Virgo S190728q Global MASTER-Net observations report
  18. Fermi trigger No 585988241 Global MASTER-Net observations report
  19. GRB 190728A: Fermi GBM Final Real-time Localization
  20. GRB 190727B: Fermi GBM observations
  21. LIGO/Virgo S190727h: No counterpart candidates in KAIT observations
  22. GRB 190727B: BALROG localization (Fermi Trigger 585951481 / GRB 190727846)
  23. GRB 190727B: Fermi GBM Final Real-time Localization
  24. GRB 190727B: Swift detection of a burst
  25. GRB 190727A: BALROG localization (Fermi Trigger 585936117 / GRB 190727668)
  26. LIGO/Virgo S190727h: No counterpart candidates in the Swift/BAT Observations
  27. GRB 190727A: Fermi GBM Final Real-time Localization
  28. LIGO/Virgo S190727h: No counterpart candidates in Fermi-LAT observations
  29. LIGO/Virgo S190727h: possible counterpart candidate in SPI-ACS/INTEGRAL
  30. LIGO/Virgo S190727h: Upper limits from Fermi-GBM Observations
  31. LIGO/Virgo S190727h: No counterpart candidates in HAWC observations
  32. LIGO/Virgo S190727h : no neutrino counterpart candidate in ANTARES search
  33. LIGO/Virgo S190727h: No counterpart candidates in AGILE-MCAL observations
  34. LIGO/Virgo S190727h: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  35. LIGO/Virgo S190727h: Coverage and upper limits from MAXI/GSC observations
  36. LIGO/Virgo S190727h: Identification of a GW compact binary merger candidate
  37. LIGO/Virgo S190727h Global MASTER-Net observations report
  38. LIGO/Virgo S190727h: Upper limits from IceCube neutrino searches
  39. Fermi trigger No 585864875 Global MASTER-Net observations report
  40. Fermi trigger No 585847498 Global MASTER-Net observations report
  41. GRB 190726B: BALROG localization (Fermi Trigger 585864875 / GRB 190726843)
  42. GRB 190726B: Fermi GBM Final Real-time Localization
  43. Fermi trigger No 585856427 Global MASTER-Net observations report
  44. GRB 190726A: BALROG localization (Fermi Trigger 585847498 / GRB 190726642)
  45. GRB 190726A: Fermi GBM Final Real-time Localization
  46. LIGO/Virgo S190718y: Classification of AT 2019lqm / Gaia19dcs as a Type Ia Supernova
  47. LIGO/Virgo S190718y: Classification of AT 2019lqn / Gaia19dct as a Type Ia Supernova
  48. LIGO/Virgo S190718y: Swift XRT observations, 45 X-ray sources
  49. GRB 190724A: Insight-HXMT/HE detection
  50. GRB 190723A: Insight-HXMT/HE detection
  51. GRB 190720A: CALET Gamma-Ray Burst Monitor detection
  52. LIGO/Virgo S190720a: Thacher Observatory follow-up observations
  53. IPN triangulation of GRB 190724A (short)
  54. LIGO/Virgo S190718y: Gaia Photometric Alerts transient candidates
  55. GRB 190719C: optical afterglow confirmation
  56. Fermi trigger No 585621841 Global MASTER-Net observations report
  57. GRB 190724A: Fermi GBM Final Real-time Localization
  58. Fermi trigger No 585559462 Global MASTER-Net observations report
  59. GRB 190723A: Fermi GBM Final Real-time Localization
  60. IPN triangulation of GRB 190720A
  61. LIGO/Virgo S190720a: Updated localization from LIGO and Virgo data
  62. GRB 190720B: Insight-HXMT/HE detection
  63. LIGO/Virgo S190720a: No counterpart candidates in CNEOST observations
  64. LIGO/Virgo S190720a: No counterpart candidates in Fermi-LAT observations
  65. LIGO/Virgo S190720a: Upper limits from CALET observations
  66. LIGO/Virgo S190720a: No counterpart candidates in KAIT observations
  67. GRB 190720B: Fermi GBM Final Real-time Localization
  68. GRB 190720A: Fermi GBM detection
  69. GRB 190719C: Fermi GBM detection
  70. GRB 190719C: Swift-BAT refined analysis
  71. GRB 190719C: Swift/UVOT Upper Limits
  72. LIGO/Virgo S190720a: No counterpart candidates in the Swift/BAT Observations
  73. GRB 190719C: Swift-XRT light-curve fit
  74. GRB 190719C: Swift-XRT refined Analysis
  75. GRB 190720A: BALROG localization (Fermi Trigger 585326534 / GRB 190720613)
  76. GRB 190720A: Fermi GBM Final Real-time Localization
  77. LIGO/Virgo S190720a: Upper limits from Fermi-GBM Observations
  78. LIGO/Virgo S190720a: Upper limits from AGILE-GRID observations
  79. LIGO/Virgo S190720a : no neutrino counterpart candidate in ANTARES search
  80. LIGO/Virgo S190720a: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  81. LIGO/Virgo S190720a: Coverage and upper limits from MAXI/GSC observations
  82. LIGO/Virgo S190718y: No counterpart candidates in CNEOST
  83. LIGO/Virgo S190720a: AGILE-MCAL observations
  84. LIGO/Virgo S190720a: Identification of a GW compact binary merger candidate
  85. LIGO/Virgo S190720a Global MASTER-Net observations report
  86. LIGO/Virgo S190720a: No counterpart candidates in HAWC observations
  87. LIGO/Virgo S190720a: Upper limits from IceCube neutrino searches
  88. Fermi trigger No 585196946 Global MASTER-Net observations report
  89. GRB 190719C: NOT candidate optical afterglow and host
  90. LIGO/Virgo S190718y: No counterpart candidates in KAIT observations
  91. LIGO/Virgo S190718y: ZTF pre-detection of MASTER candidate AT2019lly
  92. LIGO/Virgo S190718y: Analysis update
  93. GRB 190719C: Swift detection of a burst
  94. MASTER OT detection inside LIGO/Virgo S190718y error box
  95. GRB 190719C: Fermi GBM Final Real-time Localization
  96. LIGO/Virgo S190718y: Upper limits from Insight-HXMT/HE observations
  97. LIGO/Virgo S190718y: No counterpart candidates in Fermi-LAT observations
  98. GRB 190719B: a long GRB detected by INTEGRAL
  99. LIGO/Virgo S190718y: Coverage and upper limits from MAXI/GSC observations
  100. LIGO/Virgo S190718y: Upper limits from CALET observations

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