Spectroscopic time-series analysis of R Canis Majoris

Lehmann, H.; Tsymbal, V.; Pertermann, F.; Tkachenko, A.; Mkrtichian, D. E.; A-thano, Napaporn

doi:10.1051/0004-6361/201629914

Cited by 15 publications

(16 citation statements)

References 54 publications

(60 reference statements)

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“…As can be seen the S 1 and S 2 are in very good agreement with the corresponding synthetic spectra and their detection significance is D 1 59 and D 2 = 54, respectively. A comparison of our results and those obtained by Lehmann et al (2018) using KOREL is shown in Figure 8. As can be seen there is a very good agreement for the Primary spectrum (with an rms values of 0.01) and a satisfactory agreement for the Secondary spectrum (rms = 0.10).…”

Section: Simulation Resultsmentioning

confidence: 70%

“…In making the average of the second component estimates we used the RV star2,star1 from Lehmann et al (2018) to put all the individual S j 2 in the reference frame where RV star2 = 0. The results are shown in Figure 7: in the top panel we plot S 1 compared with the synthetic spectrum of the primary star computed using its atmospheric parameters given in (Lehmann et al 2018, Table 1), in the middle panel S 2 is compared with the corresponding synthetic spectrum, and in the bottom panel we show S 1 an S 2 ACFs. To evaluate the detection significance we show in the bottom panel also the ACF of the false S 2 we obtained by using k pairs built with two spectra both taken during the secondary eclipse.…”

Section: Simulation Resultsmentioning

confidence: 99%

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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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Section: Simulation Resultsmentioning

confidence: 70%

Section: Simulation Resultsmentioning

confidence: 99%

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 effect was predicted and found in photometric (e.g. Gamarova et al 2003;Mkrtichian et al 2004;Reed et al 2005) and spectroscopic (Lehmann et al 2018) observations. The dynamic eclipse mapping method was introduced by Bíró & Nuspl (2011) with the aim of NRP mode identification by reconstructing the surface intensity patterns on EBs.…”

Section: Introductionmentioning

confidence: 55%

“…The program also delivers optimised values of the RVs of the components and their radii ratio. A first successful application of the program to the short-period Algol R CMa is presented in Lehmann et al (2018); this work also includes a short description of the program algorithms and shows the advantages of LSDbinary against TOD-COR (Zucker & Mazeh 1994) in the case of very small flux ratios between the components of binary stars. We applied LSDbinary to the spectra of RZ Cas to obtain the separated LSD profiles and RVs of its components.…”

Section: Radial Velocities and Lsd Profiles With Lsdbinarymentioning

confidence: 99%

“…This is in particular valid for systems like the so-called R CMa stars (e.g. Budding & Butland 2011;Lehmann et al 2013Lehmann et al , 2018 that include companions of extremely low masses. But also for the oEA star RZ Cas, calculations showed that its actual configuration cannot be explained when assuming a purely conservative mass-transfer scenario in the past (Mennekens et al 2008).…”

Section: Introductionmentioning

confidence: 99%

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Spectroscopic long-term monitoring of RZ Cas

Lehmann

Dervişoğlu

Mkrtichian

et al. 2020

A&A

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Context. RZ Cas is a short-period Algol-type system showing episodes of mass transfer and δ Sct-like oscillations of its massgaining primary component. This system exhibits temporal changes in orbital period, v sin i, and the oscillation pattern of the primary component. Aims. We analyse high-resolution spectra of RZ Cas that we obtained during a spectroscopic long-term monitoring lasting from 2001 to 2017. In this first part we investigate the atmospheric parameters of the stellar components and the time variation of orbital period, v sin i, and radial velocities (RVs), searching for seasonal changes that could be related to episodes of mass exchange and to a possible activity cycle of the system triggered by the magnetic cycle of the cool companion. Methods. We used spectrum synthesis to analyse the spectra of both components of RZ Cas. The study of variations of the orbital period is based on published times of primary minima. We used the LSDbinary program to derive separated RVs and least-squares deconvolved (LSD) profiles of the components. From the LSD profiles of the primary we determined its v sin i. Using Markov Chain Monte Carlo simulations with the PHOEBE program, we modelled the RV variations of both components. Results. Spectrum analysis resulted in precise atmospheric parameters of both components, in particular in surface abundances below solar values. We find that the variation of orbital period is semi-regular and derive different characteristic timescales for different epochs of observation. We show that the RV variations with orbital phase can be modelled when including two cool spots on the surface of the secondary component. The modelling leads to very precise masses and separation of the components. The seasonal variation of several parameters, such as v sin i, rotation-orbit synchronisation factor, strength of the spots on the cool companion, and orbital period, can be characterised by a common timescale of the order of nine years. Conclusions. We interpret the timescale of nine years as the magnetic activity cycle of the cool companion. In particular the behaviour of the dark spots on the cool companion leads us to the interpretation that this timescale is based on an 18-year magnetic dynamo cycle. We conclude that the mass-transfer rate is controlled by the variable depth of the Wilson depression in the magnetic spot around the Lagrangian point L1. In the result, based on available data, we observe a damped activity cycle of the star, starting with a high mass-transfer episode around 2001 with a calculated mass-transfer rate of 1.5 × 10 −6 M yr −1 , followed by quiet periods in 2006 and 2009, slightly higher activity around 2013 and 2014, and again followed by quiet periods in 2015 and 2016. However, owing to missing data for years 2010 and 2011, we cannot exclude that a second high mass-transfer episode occurred within this time span.

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Pushing least-squares deconvolution to the next level: Application to binary stars

Tkachenko

Tsymbal

Zvyagintsev

et al. 2022

A&A

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Context. Eclipsing, spectroscopic double-lined (SB2) binaries remain the prime source of precise and accurate fundamental properties of stars. Furthermore, high-cadence spectroscopic observations of the eclipse phases allow us to resolve the Rossiter-McLaughlin (RM) effect, whose modelling offers the means to probe spin-orbit misalignment in binaries. Aims. We aim to develop a method that provides precise and accurate measurements of radial velocities (RVs) of both binary components, including the in-eclipse orbital phases where line profiles are subject to large distortions due to the RM effect. We also intend to separate spectral contributions of the primary and secondary components in the velocity space in order that a time series of the separated spectroscopic signals can be obtained throughout the binary orbit, preserving any line-profile variability (LPV) that might be present in either or both of those spectroscopic contributions. Methods. In this study, we provide a generalisation of the least-squares deconvolution (LSD) method to SB2 systems. Our LSDBinary algorithm is capable of working with both in-eclipse and out-of-eclipse spectra as input, and delivers the LSD profiles, LSD-based model spectra, and precise RVs of both binary components as output. We offer an option to account for the RM effect in the calculation of the initial guess LSD profiles and components' flux ratio, such that the effect can be modelled within the algorithm itself. In that case, the algorithm delivers both the LSD profiles and RVs, which are no longer distorted by the RM effect. Otherwise, when geometry of the RM effect is ignored in the calculation of the initial guess, the LSDBinary algorithm delivers an RV curve that contains contributions from both the orbital motion of the star and spectral line distortions due to the RM effect. Results. In this study, we provide an extensive test of the LSDBinary software package on simulated spectra of artificial binaries resembling Algol-type systems and detached binaries with similar components. We study the effects of signal-to-noise ratios (S/N) of input spectra, the resolving power of the instrument, uncertain atmospheric parameters of stars, and orbital properties of the binary system on the resulting LSD profiles and RVs measured from them. We find that atmospheric parameters have a negligible effect on the shape of the computed LSD profiles while affecting mostly their global scaling. High-resolution (R 60 000) spectroscopic observations are required in order to investigate the RM effect in detail, although a medium resolving power of R ≈25 000-30 000 might suffice when the amplitude of the effect is large. Our results are barely sensitive to the S/N of the input spectra provided they contain a sufficient number of spectral lines, such as in A-type and later stars. Finally, the orbital inclination angle and the components' radii ratio are found to have the largest effect on the shapes of the LSD profiles and RV curves extracted from them. Conclusions. The LSDBinary algorithm is ...

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Spectroscopic time-series analysis of R Canis Majoris

Cited by 15 publications

References 54 publications

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

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

Spectroscopic long-term monitoring of RZ Cas

Pushing least-squares deconvolution to the next level: Application to binary stars

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