Infrared He I 10830 Å, ultra-violet Ca II, and Mg II chromosphere emissions in the spectra of classical Cepheid X Cyg

Andrievsky, S. M.; Kovtyukh, V. V.; Коротин, С. А.

doi:10.1051/0004-6361/202245384

Cited by 2 publications

(2 citation statements)

References 57 publications

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“…However, in 2019, simultaneous data with the HARPS-N and GIANO instruments were secured for a set of five Cepheids, including δ Cep, using the GIARPS (GIAno & haRPS) mode (Claudi et al 2016). Two studies focused on the He I 10830 Å spectral line and the effective temperature determination of Cepheids, respectively (Andrievsky et al 2023;Kovtyukh et al 2023). In this Letter we report the 2019 HARPS-N radial velocity measurements of δ Cep and present clear evidence of the presence of an inner companion (Sect.…”

Section: Introductionmentioning

confidence: 72%

HARPS-N high spectral resolution observations of Cepheids

Nardetto

Gieren

Storm

et al. 2023

A&A

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Context. The Baade-Wesselink (BW) method of distance determination of Cepheids is used to calibrate the distance scale. Various versions of this method are mainly based on interferometry and/or the surface-brightness color relation (SBCR). Aims. We quantify the impact of the SBCR, its slope, and its zero point on the projection factor. This quantity is used to convert the pulsation velocity into the radial velocity in the BW method. We also study the impact of extinction and of a potential circumstellar environment on the projection factor. Methods. We analyzed HARPS-N spectra of η Aql to derive its radial velocity curve using different methods. We then applied the inverse BW method using various SBCRs in the literature in order to derive the BW projection factor. Results. We find that the choice of the SBCR is critical: a scatter of about 8% is found in the projection factor for different SBCRs in the literature. The uncertainty on the coefficients of the SBCR affects the statistical precision of the projection factor only little (1–2%). Confirming previous studies, we find that the method with which the radial velocity curve is derived is also critical, with a potential difference on the projection factor of 9%. An increase of 0.1 in E(B − V) translates into a decrease in the projection factor of 3%. A 0.1 mag effect of a circumstellar envelope (CSE) in the visible domain is rather small on the projection factor, about 1.5%. However, we find that a 0.1 mag infrared excess in the K band due to a CSE can increase the projection factor by about 6%. Conclusions. The impact of the surface-brightness color relation on the BW projection factor is found to be critical. Efforts should be devoted in the future to improve the SBCR of Cepheids empirically, but also theoretically, taking their CSE into account as well.

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Section: Introductionmentioning

confidence: 72%

HARPS-N high spectral resolution observations of Cepheids

Nardetto

Gieren

Storm

et al. 2023

A&A

View full text Add to dashboard Cite

show abstract

“…However, in 2019, simultaneous data with the HARPS-N and GIANO instruments were secured for a set of five Cepheids, including δ Cep, using the GIARPS (GIAno & haRPS) mode (Claudi et al 2016). Two studies focused on the He I 10 830 Å spectral line and the effective temperature determination of Cepheids, respectively (Andrievsky et al 2023;Kovtyukh et al 2023). In this Letter we report the 2019 HARPS-N radial velocity measurements of δ Cep and present clear evidence of the presence of an inner companion (Sect.…”

Section: Introductionmentioning

confidence: 72%

The orbital parameters of theδCep inner binary system determined using 2019 HARPS-N spectroscopic data

Nardetto,

Hocdé,

Kervella

et al. 2024

A&A

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An inner companion has recently been discovered orbiting the prototype of classical Cepheids, delta Cep, whose orbital parameters are still not fully constrained. We collected new precise radial velocity measurements of delta Cep in 2019 using the HARPS-N spectrograph mounted at the Telescopio Nazionale Galileo . Using these radial velocity measurements, we aimed to improve the orbital parameters of the system. We considered a template available in the literature as a reference for the radial velocity curve of the pulsation of the star. We then calculated the residuals between our global dataset (composed of the new 2019 observations plus data from the literature) and the template as a function of the pulsation phase and the barycentric Julian date. This provides the orbital velocity of the Cepheid component. Using a Bayesian tool, we derived the orbital parameters of the system. Considering priors based on already published Gaia constraints, we find for the orbital period a maximum a posteriori probability of $P_ orb $ years (uncertainties correspond to the 95<!PCT!> highest density probability interval), and we obtain an eccentricity $e=0.71_ $, a semimajor axis $a=0.029_ $ arcsecond, and a center-of-mass velocity $V_ among other parameters. In this short analysis we derive the orbital parameters of the delta Cep inner binary system and provide a cleaned radial velocity curve of the pulsation of the star, which will be used to study its Baade-Wesselink projection factor in a future publication.

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Infrared He I 10830 Å, ultra-violet Ca II, and Mg II chromosphere emissions in the spectra of classical Cepheid X Cyg

Cited by 2 publications

References 57 publications

HARPS-N high spectral resolution observations of Cepheids

HARPS-N high spectral resolution observations of Cepheids

The orbital parameters of theδCep inner binary system determined using 2019 HARPS-N spectroscopic data

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Infrared He I 10830 Å, ultra-violet Ca II, and Mg II chromosphere emissions in the spectra of classical Cepheid X Cyg

Cited by 2 publications

References 57 publications

HARPS-N high spectral resolution observations of Cepheids

HARPS-N high spectral resolution observations of Cepheids

The orbital parameters of theδCep inner binary system determined using 2019 HARPS-N spectroscopic data

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Product

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Infrared He I 10830 Å, ultra-violet Ca II, and Mg II chromosphere emissions in the spectra of classical Cepheid X Cyg