Spectral disentangling with Spectangular

Sablowski, D. P.; Weber, M.

doi:10.1051/0004-6361/201628716

Cited by 11 publications

(12 citation statements)

References 18 publications

(17 reference statements)

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“…Since the RVs of BAT99 32 and 77 could not be derived, we attempted their disentanglement using the code Spectangular, which is based on singular value decomposition in the wavelength domain (Sablowski & Weber 2017), first applied to WR stars in Shenar et al (2017). This procedure needs spectra spread over the orbital period and optimizes the orbital parameters or the RVs to minimize the residuals between the disentangled spectra and the observations.…”

Section: Spectral Disentanglementmentioning

confidence: 99%

The Wolf–Rayet binaries of the nitrogen sequence in the Large Magellanic Cloud

Shenar

Sablowski

Hainich

et al. 2019

A&A

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Context. Massive Wolf-Rayet (WR) stars dominate the radiative and mechanical energy budget of galaxies and probe a critical phase in the evolution of massive stars prior to core collapse. It is not known whether core He-burning WR stars (classical WR; cWR) form predominantly through wind stripping (w-WR) or binary stripping (b-WR). Whereas spectroscopy of WR binaries has so-far largely been avoided because of its complexity, our study focuses on the 44 WR binaries and binary candidates of the Large Magellanic Cloud (LMC; metallicity Z ≈ 0.5 Z ), which were identified on the basis of radial velocity variations, composite spectra, or high X-ray luminosities. Aims. Relying on a diverse spectroscopic database, we aim to derive the physical and orbital parameters of our targets, confronting evolution models of evolved massive stars at subsolar metallicity and constraining the impact of binary interaction in forming these stars. Methods. Spectroscopy was performed using the Potsdam Wolf-Rayet (PoWR) code and cross-correlation techniques. Disentanglement was performed using the code Spectangular or the shift-and-add algorithm. Evolutionary status was interpreted using the Binary Population and Spectral Synthesis (BPASS) code, exploring binary interaction and chemically homogeneous evolution. Results. Among our sample, 28/44 objects show composite spectra and are analyzed as such. An additional five targets show periodically moving WR primaries but no detected companions (SB1); two (BAT99 99 and 112) are potential WR + compact-object candidates owing to their high X-ray luminosities. We cannot confirm the binary nature of the remaining 11 candidates. About two-thirds of the WN components in binaries are identified as cWR, and one-third as hydrogen-burning WR stars. We establish metallicity-dependent mass-loss recipes, which broadly agree with those recently derived for single WN stars, and in which so-called WN3/O3 stars are clear outliers. We estimate that 45±30% of the cWR stars in our sample have interacted with a companion via mass transfer. However, only ≈12±7% of the cWR stars in our sample naively appear to have formed purely owing to stripping via a companion (12% b-WR). Assuming that apparently single WR stars truly formed as single stars, this comprises ≈ 4% of the whole LMC WN population, which is about ten times less than expected. No obvious differences in the properties of single and binary WN stars, whose luminosities extend down to log L≈5.2 [L ], are apparent. With the exception of a few systems (BAT99 19, 49, and 103), the equatorial rotational velocities of the OB-type companions are moderate (v eq 250 km s −1 ) and challenge standard formalisms of angular-momentum accretion. For most objects, chemically homogeneous evolution can be rejected for the secondary, but not for the WR progenitor. Conclusions. No obvious dichotomy in the locations of apparently single and binary WN stars on the Hertzsprung-Russell diagram is apparent. According to commonly used stellar evolution models (BPASS, Geneva), most a...

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Section: Spectral Disentanglementmentioning

confidence: 99%

The Wolf–Rayet binaries of the nitrogen sequence in the Large Magellanic Cloud

Shenar

Sablowski

Hainich

et al. 2019

A&A

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“…The results for the spectra of the primary and secondary star showed that our method can be considered as a valid, and somewhat easier, alternative to well established codes for analysing binary stars like e.g. KOREL, FDbinary (Ilijic et al 2004) or Spectangular (Sablowski & Weber 2017).…”

Section: Discussionmentioning

confidence: 79%

Using Independent Component Analysis to Detect Exoplanet Reflection Spectrum from Composite Spectra of Exoplanetary Binary Systems

Marcantonio

Morossi

Franchini

et al. 2019

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The analysis of the wavelength-dependent albedo of exoplanets represents a direct way to provide insight of their atmospheric composition and to constrain theoretical planetary atmosphere modelling. Wavelength-dependent albedo can be inferred from the exoplanet's reflected light of the host star, but this is not a trivial task In fact, the planetary signal may be several orders of magnitude lower (10 −4 or below) than the flux of the host star, thus making its extraction very challenging. Successful detection of the planetary signature of 51 Peg b has been recently obtained by using cross-correlation function (CCF) or autocorrelation function (ACF) techniques. In this paper we present an alternative method based on the use of Independent Component Analysis (ICA). In comparison to the above-mentioned techniques, the main advantages of ICA are that the extraction is "blind" i.e. it does not require any a priori knowledge of the underlying signals, and that our method allows us not only to detect the planet signal but also to estimate its wavelength dependence. To show and quantify the effectiveness of our method we successfully applied it to both simulated data and real data of an eclipsing binary star system. Eventually, when applied to real 51 Peg + 51 Peg b data, our method extracts the signal of 51 Peg but we could not soundly detect the reflected spectrum of 51 Peg b mainly due to the insufficient SN R of the input composite spectra. Nevertheless, our results show that with "ad-hoc" scheduled observations an ICA approach will be, in perspective, a very valid tool for studying exoplanetary atmospheres.

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“…First, three spectra that show the smallest signal from tellurics were selected from the 12 spectra listed in Tabel 1. As pointed out by Sablowski & Weber (2017), at least 3 spectra are required because SVD has to be performed on an overdetermined system of equations, that is, for two components present in the spectra, at least three observations are required. Furthermore, these spectra should correspond to distinctive orbital phases.…”

Section: Appendix B: Spectrum Of the Secondarymentioning

confidence: 99%

“…Because the correction of the telluric lines in the wavelength range under consideration is crucial for the analysis, some details of this procedure are described here. A forthcoming paper by Sablowski et al (2019) will discuss these disentangling problems in more detail.…”

Section: Appendix A: Correction Of Tellurics and Flux Ratiomentioning

confidence: 99%

Carbon¹²C/¹³C isotope ratio ofαAurigae revised

Sablowski

Järvinen

Ilyin

et al. 2019

A&A

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Context. Capella (α Aur) is one of the few binaries in the sky with two cool giant stars. With spectral types of G8III and G0III, the two components appear at different but distinct stages in their evolution. The G0 secondary star is a Hertzsprung-gap giant, and the G8 primary star is thought to be a clump giant. Aims. We present a new measure of the carbon 12 C/ 13 C isotope ratio of the primary component of Capella using high-resolution R ≈250 000 spectra obtained with the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) with both the Vatican Advanced Technology Telescope (VATT) and the Large Binocular Telescope (LBT). Methods. Signal-to-noise ratios of up to 2 700 were obtained by averaging nightly spectra. These average spectra were used to disentangle the two binary components. The isotope ratio was derived with the use of spectrum synthesis from the CN lines at 8004 Å. Results. We found that the 12 C/ 13 C ratio of the primary component of Capella is 17.8±1.9. Our measurement precision is now primarily limited by the spectral-line data and by the grid-step size of the model atmospheres rather than the data. The separated spectrum of the secondary component does not show distinguishable 12 CN and 13 CN lines because of its v sin i and higher temperature. Conclusions. Our new 12 C/ 13 C value is significantly lower than the previous value of 27±4 but now agrees better with the recent model prediction of 18.8 -20.7.

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Spectral disentangling with Spectangular

Cited by 11 publications

References 18 publications

The Wolf–Rayet binaries of the nitrogen sequence in the Large Magellanic Cloud

The Wolf–Rayet binaries of the nitrogen sequence in the Large Magellanic Cloud

Using Independent Component Analysis to Detect Exoplanet Reflection Spectrum from Composite Spectra of Exoplanetary Binary Systems

Carbon¹²C/¹³C isotope ratio ofαAurigae revised

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Spectral disentangling with Spectangular

Cited by 11 publications

References 18 publications

The Wolf–Rayet binaries of the nitrogen sequence in the Large Magellanic Cloud

The Wolf–Rayet binaries of the nitrogen sequence in the Large Magellanic Cloud

Using Independent Component Analysis to Detect Exoplanet Reflection Spectrum from Composite Spectra of Exoplanetary Binary Systems

Carbon12C/13C isotope ratio ofαAurigae revised

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Product

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Carbon¹²C/¹³C isotope ratio ofαAurigae revised