The quick and strong recovery of the He ii emission in 2014 supports a scenario, in which the wind-wind shock may not have completely collapsed as was proposed for previous events. The polar spectrum at FOS4 shows fewer changes in the broad wind emission lines, which may be explained by the latitude-dependent wind structure of η Car. The strengthening of He i and N ii emission and the weakening of the lower-excitation H α and Fe ii wind featuresin our direct line of sight implies a substantial change in the physical parameters of the emitting regions. The ionizing UV radiation dramatically weakened during each pre-2014 event but not in 2014. The basic character of η Car’s spectroscopic events has changed in the past two to three cycles. The He ii equivalent widths at FOS4 were larger in 20 than during the 2003 event.Ĭonclusions. The optical continuum brightened by a factor of ~4 in the past 10 −15 years.The polar spectrum shows fewer changes in the broad wind emission lines: the Fe ii emission strength decreased by a factor of ~2 (compared to a factor of ~4 in our direct line of sight). On the other hand, H α and Fe ii lines show the smallest emission strengths ever observed in η Car. The N ii emission lines also increased in strength. The He i line flux grew by a factor of ~8 in 2009 −2014 compared to 1998 −2003. The second He ii peak occurred at about the same phase as in 2009, but was stronger. While the timing of the first He ii λ4686 flash was remarkably similar to previous events, the He ii equivalent widths were slightly larger, and the line flux increased by a factor of ~7 compared to 2003. Important spectroscopic diagnostics during η Car’s events show significant changes in 2014 compared to previous events. The strategy for UVES observations allows for a multidimensional analysis, because each location in the reflection nebula is correlated with a different stellar latitude. The STIS spectra provide high spatial resolution and include epochs during the 2014 event when observations from most ground-based observatories were not feasible. Archival observations with these instruments cover three orbital cycles and the events of 2003.5, 2009.1, and 2014.6. Eta Car was observed with HST STIS, VLT UVES, and CTIO 1.5 m CHIRON for a period of more than two years in 2012 −2015. We compare the recent spectroscopic event in mid-2014 to the events in 20 and investigate long-term trends. These so-called spectroscopic events are most likely caused by the close approach of a companion. Every 5.5 years, η Car’s light curve and spectrum change remarkably across all observed wavelength bands. Universidad de Chile, Departamento Astronomía, Casilla 36-D,Īstronomisches Institut, Ruhr-Universität Bochum,Īims. School of Science, Nagoya University, 464-8602 University of Illinois Springfield, Springfield, ILĭivision of Elementary Particle Physics and Astrophysics, Graduate Southern Hemisphere, Karl-Schwarzschild-Straße 2, 85748 Hemisphere, Alonso de Cordova 3107, of Astronomy, University of Minnesota,ĭepartment of Physics and Astronomy, Stony BrookĮSO – European Organisation for Astronomical Research in the Weis 8ĮSO – European Organisation for Astronomical Research in the Southern Astronomical objects: linking to databasesĪ.Including author names using non-Roman alphabets.Suggested resources for more tips on language editing in the sciences Punctuation and style concerns regarding equations, figures, tables, and footnotes
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