Spectral energy distributions of classical cepheids in the Magellanic Clouds. (arXiv:2307.07559v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Groenewegen_M/0/1/0/all/0/1">Martin Groenewegen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lub_J/0/1/0/all/0/1">Jan Lub</a>
(abridged) In this study, we constructed spectral energy distributions (SEDs)
for a sample of 142 LMC and 77 SMC fundamental-mode classical Cepheids (CCs)
using photometric data from the literature. When possible, the data were taken
to be representative of mean light or averaged over the light curve. The sample
was built from stars that either have a metallicity determination from
high-resolution (HR) spectroscopy or have been used in Baade-Wesselink types of
analyses, or have a radial velocity curve published in Gaia DR3 or have
Walraven photometry, or have their light- and radial-velocity curves modelled
by pulsation codes. The SEDs were fitted with stellar photosphere models to
derive the best-fitting luminosity and effective temperature. Only one star
with a significant infrared excess was found in the LMC and none in the SMC,
suggesting that IR excess may be more prominent in MW cepheids than in the
Magellanic Clouds. For the large majority of stars, the position in the
Hertzsprung-Russell diagram is consistent with theoretical instability strips.
Period-luminosity (PL) and period-radius relations were derived and compared to
these relations in the MW. For a fixed slope, the zero point of the bolometric
PL relation does not depend on metallicity, contrary to recent findings of a
significant metallicity term when considering the PL relation in different
photometric bands. An intriguing result concerns the flux-weighted gravity
(FWG, a quantity derived from gravity and Teff) and its relation to period and
luminosity. Both relations agree with theory, with the results for the MW, and
with the independent estimates from the six known LMC eclipsing binaries that
contain CCs. However, the FWG (as determined from dedicated HR spectroscopy for
the sample) is too low by about 0.8 dex in 90 percent of the cases.
(abridged) In this study, we constructed spectral energy distributions (SEDs)
for a sample of 142 LMC and 77 SMC fundamental-mode classical Cepheids (CCs)
using photometric data from the literature. When possible, the data were taken
to be representative of mean light or averaged over the light curve. The sample
was built from stars that either have a metallicity determination from
high-resolution (HR) spectroscopy or have been used in Baade-Wesselink types of
analyses, or have a radial velocity curve published in Gaia DR3 or have
Walraven photometry, or have their light- and radial-velocity curves modelled
by pulsation codes. The SEDs were fitted with stellar photosphere models to
derive the best-fitting luminosity and effective temperature. Only one star
with a significant infrared excess was found in the LMC and none in the SMC,
suggesting that IR excess may be more prominent in MW cepheids than in the
Magellanic Clouds. For the large majority of stars, the position in the
Hertzsprung-Russell diagram is consistent with theoretical instability strips.
Period-luminosity (PL) and period-radius relations were derived and compared to
these relations in the MW. For a fixed slope, the zero point of the bolometric
PL relation does not depend on metallicity, contrary to recent findings of a
significant metallicity term when considering the PL relation in different
photometric bands. An intriguing result concerns the flux-weighted gravity
(FWG, a quantity derived from gravity and Teff) and its relation to period and
luminosity. Both relations agree with theory, with the results for the MW, and
with the independent estimates from the six known LMC eclipsing binaries that
contain CCs. However, the FWG (as determined from dedicated HR spectroscopy for
the sample) is too low by about 0.8 dex in 90 percent of the cases.
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