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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 S191213g: Lulin Follow-up Observations of AT2019wxt
  2. LIGO/Virgo S191205ah: AT2019wmy 10.4m GTC spectroscopy
  3. LIGO/Virgo S191213g: Swift UVOT/XRT observations of Pan-STARRS1 candidate: PS19hgw
  4. LIGO/Virgo S191213g: Palomar 60-inch imaging of AT2019wxt
  5. LIGO/Virgo S191213g: GRAWITA TNG NIR imaging of AT2019wxt (PS19hgw)
  6. LIGO/Virgo S191216ap, Swift XRT observations: 16 X-ray sources in the HAWC error region search
  7. LIGO/Virgo S191213g: MASTER observation of AT2019wxt (PS19hgw)
  8. LIGO/Virgo S191216ap: No candidates found in J-GEM follow-up observations of HAWC error region
  9. GRB 191218A: Swift-BAT refined analysis
  10. LIGO/VIRGO S191213g: ePESSTO+ spectroscopy of AT2019wxt (PS19hgw)
  11. LIGO/VIRGO S191213g: LT spectroscopy of AT2019wxt (PS19hgw)
  12. LIGO/Virgo S191213g: AT2019wnh, AT2019wnk and AT2019wrt 10.4m GTC spectroscopy
  13. LIGO/Virgo S191213g: NOT optical spectroscopy of AT2019wxt (PS19hgw)
  14. LIGO/Virgo S191213g: HCT spectroscopy of PS19hgw / AT2019wxt
  15. LIGO/Virgo S191216ap: Correction to GCN 26488 (NOWT observations)
  16. LIGO/Virgo S191213g: No counterpart candidate in the NOWT observations
  17. LIGO/Virgo S191216ap: No candidates found in CHES observations of HAWC error region
  18. LIGO/Virgo S191216ap and IceCube neutrino: no counterpart candidates from AGILE-GRID observations
  19. LIGO/Virgo S191213g: Pan-STARRS1 discovery of a potential optical counterpart
  20. Konus-Wind observation of GRB 191213A (ulong)
  21. LIGO/Virgo S191216ap: GRAWITA Loiano observations of HAWC error region
  22. GRB 191218A: AstroSat CZTI detection
  23. LIGO/Virgo S191216ap: No transient candidates in CALET observations
  24. GRB 191218A: Swift detection of a burst
  25. LIGO/Virgo S191216ap: CORRECTED list of galaxies coincident with LIGO/Virgo and HAWC positions
  26. LIGO/Virgo S191216ap: Nanshan follow-up observations
  27. LIGO/Virgo S191213g: No candidates found in J-GEM follow-up observations
  28. LIGO/Virgo S191216ap: galaxies consistent with GW + Neutrino + HAWC position
  29. LIGO/Virgo S191216ap and IceCube neutrino: Swift XRT sources
  30. LIGO/Virgo S191216ap: IceCube event: MASTER OF detection in GW and Neutrino error field
  31. LIGO/Virgo S191216ap: No significant counterpart candidates in SAGUARO observations
  32. LIGO/Virgo S191216ap: HAWC gamma-ray sub-threshold event coincident with LIGO/Virgo and IceCube localizations
  33. LIGO/Virgo S191213g: Swift UVOT/XRT observations of three ZTF sources
  34. LIGO/Virgo S191213g: MASTER OT J064855.37-055545.7 is a dwarf nova
  35. LIGO/Virgo S191215w : No significant candidates in TAROT - FRAM - GRANDMA observations.
  36. LIGO/Virgo G191216ap: No counterpart candidates in Fermi-LAT observations
  37. LIGO/Virgo S191213g: MASTER OT detection in BNS error-box
  38. LIGO/Virgo S191216ap: no counterpart candidates in the Swift/BAT observations
  39. LIGO/Virgo S191215w: No transient candidates in CALET observations
  40. LIGO/Virgo S191216ap: No Candidates from the Zwicky Transient Facility
  41. LIGO/Virgo S191216ap: Correction to GCN 26460 (IceCube event coincident with GW event)
  42. LIGO/Virgo S191216ap: Coverage and upper limits from MAXI/GSC observations
  43. LIGO/Virgo S191216ap: Upper limits from Fermi-GBM Observations
  44. LIGO/Virgo S191216ap: 1 counterpart neutrino candidate from IceCube neutrino searches
  45. Fermi-LAT Gamma-ray Observations of IceCube-191215A
  46. LIGO/Virgo S191216ap : no neutrino counterpart candidate in ANTARES search
  47. LIGO/Virgo S191216ap: Global MASTER-Net observations report
  48. LIGO/Virgo S191216ap: no INTEGRAL observation
  49. LIGO/Virgo S191216ap: No counterpart candidates in HAWC observations
  50. LIGO/Virgo S191216ap: Identification of a GW compact binary merger candidate
  51. LIGO/Virgo S191215w: no counterpart candidates in the Swift/BAT observations
  52. LIGO/Virgo S191215w: No counterpart candidates in Fermi-LAT observations
  53. IceCube-191215A: Upper limits from a search for additional neutrino events in IceCube
  54. UKIRT photometry of ZTF19acyldun/AT 2019wrt
  55. LIGO/Virgo S191215w: AstroSat CZTI upper limits
  56. LIGO/Virgo S191215w: upper limits from AGILE-GRID observations
  57. LIGO/Virgo S191215w: upper limits from AGILE/MCAL observations
  58. LIGO/Virgo S191215w: Upper limits from Fermi-GBM Observations
  59. LIGO/Virgo S191215w: No counterpart candidates in HAWC observations
  60. LIGO/Virgo S191215w: Coverage and upper limits from MAXI/GSC observations
  61. LIGO/Virgo S191215w : no neutrino counterpart candidate in ANTARES search
  62. LIGO/Virgo S191215w: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  63. LIGO/Virgo S191215w: Identification of a GW compact binary merger candidate
  64. LIGO/Virgo S191215w: Global MASTER-Net observations report
  65. LIGO/Virgo S191215w: Upper limits from IceCube neutrino searches
  66. IceCube-191215A: not observable by Fermi-GBM
  67. LIGO/Virgo S191213g: Additional candidates from the Zwicky Transient Facility
  68. IceCube-191215A: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  69. IceCube-191215A - IceCube observation of a high-energy neutrino candidate event
  70. IceCube Alert 191215.47: Global MASTER-Net observations report
  71. LIGO/Virgo S191213g: Upper limits from Insight-HXMT/HE observations
  72. LIGO/Virgo S191213g: LCOGT photometry of ZTF19acymaru/AT2019wnh
  73. LIGO/Virgo S191213g: Lulin Follow-up Observations of ZTF19acykzsk/AT2019wqj
  74. LIGO/Virgo S191213g: Pan-STARRS1 previous detections of ZTF19acykzsk
  75. LIGO/Virgo S191213g: WHT spectroscopy of candidate counterparts
  76. LIGO/Virgo S191213g: GRAWITA TNG classification of ZTF19acykzsk
  77. LIGO/Virgo S191213g: GMOS-N spectroscopy shows ZTF19acykzsk/AT2019wqj is a SN II
  78. LIGO/Virgo S191213g: Liverpool Telescope spectroscopy of ZTF candidates
  79. LIGO/Virgo S191213g: AstroSat CZTI upper limits
  80. LIGO/Virgo S191213g: Candidates from the Zwicky Transient Facility
  81. LIGO/Virgo S191213g: No neutrino candidates at Pierre Auger Observatory
  82. LIGO/Virgo S191205ah: AT2019wix and AT2019wib 10.4m GTC spectroscopy
  83. LIGO/Virgo S191205ah: AT2019wkv, AT2019wid and AT2019wiy 10.4m GTC spectroscopy
  84. GRB 191213A: BOOTES-5/JGT optical limit
  85. LIGO/Virgo S191213g: No transient candidates in CALET observations
  86. GRB 191213A: Swift-BAT refined analysis
  87. LIGO/Virgo S191213g: Updated Sky Localization
  88. LIGO/Virgo S191205ah: Candidates from the Zwicky Transient Facility Public Survey
  89. Fermi trigger No 597955752: Global MASTER-Net observations report
  90. GRB 191213B: Fermi GBM Final Real-time Localization
  91. LIGO/Virgo S191213ai: Retraction of GW compact binary merger candidate
  92. LIGO/Virgo S191213g: No counterpart candidates in Fermi-LAT observations
  93. LIGO/Virgo S191213ai: Global MASTER-Net observations report
  94. LIGO/Virgo S191213g: no counterpart candidates in the Swift/BAT observations
  95. LIGO/Virgo S191213g: Upper limits from Fermi-GBM Observations
  96. LIGO/Virgo S191213g: upper limits from AGILE-GRID observations
  97. LIGO/Virgo S191213g: upper limits from AGILE-MCAL observations
  98. Fermi trigger No 597909938: Global MASTER-Net observations report
  99. LIGO/Virgo S191205ah: AT2019wfa 10.4m GTC spectroscopy
  100. LIGO/Virgo S191213g : no neutrino counterpart candidate in ANTARES search

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