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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 S190930t: Transient found in Swift/UVOT counterpart search
  2. LIGO/Virgo S190930t and S190930s: MASTER PSN in unknown disk galaxy
  3. LIGO/Virgo S190930t: Candidates from the Zwicky Transient Facility
  4. LIGO/Virgo S190930t: No counterpart candidates in Fermi-LAT observations
  5. LIGO/Virgo S190930t and S190930s: MASTER optical observation and optical transient
  6. Fermi trigger No 591604915: Global MASTER-Net observations report
  7. LIGO/Virgo S190930s: No counterpart candidates in Fermi-LAT observations
  8. GRB 191001A: BALROG localization (Fermi Trigger 591604915 / GRB 191001279)
  9. GRB 191001A: Fermi GBM Final Real-time Localization
  10. LIGO/Virgo S190930t: Upper limits from CALET observations.
  11. LIGO/Virgo S190930s: Upper limits from CALET observations.
  12. LIGO/Virgo S190930t: Coverage and upper limits from MAXI/GSC observations
  13. LIGO/Virgo S190930s: no counterpart candidates in the Swift/BAT observations
  14. LIGO/Virgo S190930t: no counterpart candidates in the Swift/BAT observations
  15. LIGO/Virgo S190930t: Upper limits from Fermi-GBM Observations
  16. LIGO/Virgo S190930s: Upper limits from Fermi-GBM Observations
  17. LIGO/Virgo S190930t: No counterpart candidates in HAWC observations
  18. LIGO/Virgo S190930s: no counterpart candidates in AGILE-GRID observations
  19. LIGO/Virgo S190928c: Retraction of GW unmodeled transient candidate
  20. LIGO/Virgo S190930t : no neutrino counterpart candidate in ANTARES search
  21. LIGO/Virgo S190930s : no neutrino counterpart candidate in ANTARES search
  22. LIGO/Virgo S190930t: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  23. GRB 190928A: Insight-HXMT/HE detection
  24. LIGO/Virgo S190930s: No counterpart candidates in AGILE-MCAL observations
  25. LIGO/Virgo S190930s: Coverage and upper limits from MAXI/GSC observations
  26. LIGO/Virgo S190930t: Identification of a GW compact binary merger candidate
  27. LIGO/Virgo S190930t: Global MASTER-Net observations report
  28. LIGO/Virgo S190930t: Upper limits from IceCube neutrino searches
  29. LIGO/Virgo S190930s: Upper limits from IceCube neutrino searches
  30. LIGO/Virgo S190930s: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  31. LIGO/Virgo S190930s: Identification of a GW compact binary merger candidate
  32. LIGO/Virgo S190930s: Global MASTER-Net observations report
  33. Fermi trigger No 591532362: Global MASTER-Net observations report
  34. Konus-Wind observation of GRB 190928A
  35. GRB 190928A: MASTER optical observations
  36. GRB 190930A: Fermi GBM Final Real-time Localization
  37. GRB 190928A: CALET Gamma-Ray Burst Monitor detection
  38. IPN triangulation of GRB 190928A (long/bright)
  39. Fermi trigger No 591391412: Global MASTER-Net observations report
  40. GRB 190926A: AbAO upper optical limit
  41. LIGO/Virgo S190828j: Updated Sky Localization
  42. GRB 190926A: Swift-BAT refined analysis
  43. GRB 190928A: AGILE/MCAL detection of a burst
  44. Baksan Neutrino Observatory Alert 190928.37: Global MASTER-Net observations report
  45. Fermi trigger No 591321287: Global MASTER-Net observations report
  46. GRB 190926A: Upper Limit from OSN T150 Observation
  47. LIGO/Virgo S190923y: MASTER OT outburst detection inside NSBH merger error-box
  48. GRB 190926A: MITSuME Akeno optical upper limits
  49. GRB 190926A: Swift/UVOT Upper Limits
  50. GRB 190926A: KAIT Optical Upper Limit
  51. GRB 190926A: Swift-XRT refined Analysis
  52. GRB 190926A: Enhanced Swift-XRT position
  53. Swift GRB190926.41: Global MASTER-Net observations report
  54. GRB 190926A: Swift detection of a burst
  55. LIGO/Virgo S190923y: No significant candidates in TAROT-GRANDMA observations
  56. LIGO/Virgo S190923y: no counterpart candidates in the Swift/BAT observations
  57. LIGO/Virgo S190924h: No counterpart candidates in Fermi-LAT observations
  58. LIGO/Virgo S190924h: Not observable by CALET
  59. LIGO/Virgo S190924h: no counterpart candidates in the Swift/BAT observations
  60. LIGO/Virgo S190923y: No neutrino candidates at Pierre Auger Observatory
  61. LIGO/Virgo S190924h: Upper limits from Fermi-GBM Observations
  62. LIGO/Virgo S190924h: no counterpart candidates in AGILE-GRID observations
  63. LIGO/Virgo S190924h: No counterpart candidates in AGILE-MCAL observations
  64. Fermi-LAT Gamma-ray Observations of IceCube-190922B
  65. LIGO/Virgo S190924h: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  66. LIGO/Virgo S190924h : no neutrino counterpart candidate in ANTARES search
  67. LIGO/Virgo S190924h: Coverage and upper limits from MAXI/GSC observations
  68. LIGO/Virgo S190923y: No counterpart candidates in Fermi-LAT observations
  69. IceCube-190922B: Upper limits from a search for additional neutrino events in IceCube
  70. IceCube-190922A: Upper limits from a search for additional neutrino events in IceCube
  71. LIGO/Virgo S190924h: Global MASTER-Net observations report
  72. LIGO/Virgo S190923y: Upper limits from CALET observations.
  73. LIGO/Virgo S190924h: Identification of a GW compact binary merger candidate
  74. LIGO/Virgo S190924h: Upper limits from IceCube neutrino searches
  75. Fermi-LAT Gamma-ray Observations of IceCube-190922A
  76. IceCube-190922B - HAWC follow-up
  77. LIGO/Virgo S190923y: INTEGRAL IBIS coded-masked imaging observations of part of the localization area and further all-sky upper limits
  78. IceCube-190922B: Identification of a Candidate Supernova from the Zwicky Transient Facility
  79. LIGO/Virgo S190923y: Upper limits from Fermi-GBM Observations
  80. LIGO/Virgo S190814bv: Chandra X-ray non-detection of ASKAP J005547-270433 / AT2019osy
  81. LIGO/Virgo S190923y: Upper limits from AGILE-GRID observations
  82. GRB 190923A: BALROG localization (Fermi Trigger 590942887 / GRB 190923617)
  83. LIGO/Virgo S190923y: No counterpart candidates in AGILE-MCAL observations
  84. GRB 190923A: Fermi GBM Final Real-time Localization
  85. LIGO/Virgo S190923y: Coverage and upper limits from MAXI/GSC observations
  86. LIGO/Virgo S190923y : no neutrino counterpart candidate in ANTARES search
  87. LIGO/Virgo S190923y: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  88. LIGO/Virgo S190923y: Identification of a GW compact binary merger candidate
  89. LIGO/Virgo S190923y: No counterpart candidates in HAWC observations
  90. LIGO/Virgo S190923y: Global MASTER-Net observations report
  91. LIGO/Virgo S190923y: Upper limits from IceCube neutrino searches
  92. Fermi trigger No 590899086: Global MASTER-Net observations report
  93. IceCube-190922B: INTEGRAL was inactive at the time of the event
  94. IceCube-190922B: Upper limits from Fermi-GBM Observations
  95. IceCube-190922A: Upper limits from Fermi-GBM Observations
  96. IceCube-190922B - IceCube observation of a high-energy neutrino candidate event
  97. IceCube-190922A - HAWC follow-up
  98. IceCube Alert 190922.96: Global MASTER-Net observations report
  99. IceCube-190922A: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  100. IceCube-190922A - IceCube observation of a high-energy neutrino candidate event

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