13 research outputs found
Synthetic Population of Binary Cepheids. II. The effect of companion light on the extragalactic distance scale
Because of their period-luminosity relation (PLR), classical Cepheids play a
key role in the calibration of the extragalactic distance scale and the
determination of the Hubble-Lema\^{i}tre constant . Recent findings show
that the majority of classical Cepheids should be in binary or multiple
systems, which might undermine their accuracy, as the extra -- and unaccounted
for -- light from the companions of Cepheids causes a shift in the PLR. We
quantify this shift using synthetic populations of binary Cepheids that we
developed for this purpose, as described in Paper I of this series. We find
that while all PLRs are shifted toward brighter values due to the excess light
from the companions, the bias in the relative distance modulus between two
galaxies hosting binary Cepheids can be either positive or negative, depending
on the percentage of binary Cepheids in them. If the binarity percentage in the
two galaxies is similar, the effect of binarity is canceled. Otherwise, it
introduces a shift in the distance modulus of the order of millimags in the
near-infrared passbands and Wesenheit indices, and tens of millimags in the
visual domain; its exact value depends on the variant of the synthetic
population (a unique combination of metallicity, star formation history, shape
and location of the instability strip, and initial parameter distributions).
Such shifts in distance moduli to type Ia supernova host galaxies introduce an
additional statistical error on , which however does not prevent measuring
with a precision of 1%.Comment: 16 pages, 11 figures, accepted for publication in The Astrophysical
Journa
Period-Luminosity Relations for Galactic classical Cepheids in the Sloan bands
We present the first period-luminosity (PL) and period-Wesenheit (PW)
relations in the Sloan-Pans-STARRS gP1rP1iP1 bands for classical fundamental
mode Cepheids in the Milky Way. We used a relatively modest number of 76 stars
for the PL and 84-85 stars for the PW relations calibration. The data for the
project were collected with the network of 40-cm telescopes of Las Cumbres
Observatory, and Gaia Data Release 3 parallaxes were used for the calculations.
These gri-band PL and PW relations calibrations will be a useful tool for
distance determinations in the era of large sky surveys using the Sloan
photometric system, especially with the near-future start of the Large Synoptic
Survey of Space and Time (LSST).Comment: 31 pages, 7 figures, 3 tables, Accepted for publication in Ap
Cepheids with giant companions. I. Revealing a numerous population of double-lined binary Cepheids
Masses of classical Cepheids of 3 to 11 M are predicted by theory but
those measured, clump between 3.6 and 5 M. As a result, their
mass-luminosity relation is poorly constrained, impeding our understanding of
basic stellar physics and the Leavitt Law. All Cepheid masses come from the
analysis of 11 binary systems, including only 5 double-lined and well-suited
for accurate dynamical mass determination. We present a project to analyze a
new, numerous group of Cepheids in double-lined binary (SB2) systems to provide
mass determinations in a wide mass interval and study their evolution. We
analyze a sample of 41 candidate binary LMC Cepheids spread along the P-L
relation, that are likely accompanied by luminous red giants, and present
indirect and direct indicators of their binarity. In a spectroscopic study of a
subsample of 18 brightest candidates, for 16 we detected lines of two
components in the spectra, already quadrupling the number of Cepheids in SB2
systems. Observations of the whole sample may thus lead to quadrupling all the
Cepheid mass estimates available now. For the majority of our candidates,
erratic intrinsic period changes dominate over the light travel-time effect due
to binarity. However, the latter may explain the periodic phase modulation for
4 Cepheids. Our project paves the way for future accurate dynamical mass
determinations of Cepheids in the LMC, Milky Way, and other galaxies, which
will potentially increase the number of known Cepheid masses even 10-fold,
hugely improving our knowledge about these important stars.Comment: 12 pages, 7 figures, 3 tables, accepted for publication in Ap
Discovery of a binary-origin classical Cepheid in a binary system with a 59-day orbital period
We report the discovery of a surprising binary configuration of the
double-mode Cepheid OGLE-LMC-CEP-1347 pulsating in the first (P_1=0.690d) and
second overtone (P_2=0.556d) modes. The orbital period (P_orb=59d) of the
system is five times shorter than the shortest known to date (310d) for a
binary Cepheid. The Cepheid itself is also the shortest-period one ever found
in a binary system and the first double-mode Cepheid in a spectroscopically
double-lined binary. OGLE-LMC-CEP-1347 is most probably on its first crossing
through the instability strip, as inferred from both its short period and fast
period increase, consistent with evolutionary models, and from the short
orbital period (not expected for binary Cepheids whose components have passed
through the red giant phase). Our evolutionary analysis yielded a
first-crossing Cepheid with a mass in a range of 2.9-3.4 Msun (lower than any
measured Cepheid mass), consistent with observations. The companion is a stable
star, at least two times fainter and less massive than the Cepheid (preliminary
mass ratio q=0.55), while also redder and thus at the subgiant or more advanced
evolutionary stage. To match these characteristics, the Cepheid has to be a
product of binary interaction, most likely a merger of two less massive stars,
which makes it the second known classical Cepheid of binary origin. Moreover,
further evolution of the components may lead to another binary interaction.Comment: 6 pages, 4 figures, 1 table, published in The Astrophysical Journal
Letter
The Araucaria Project. Distances to Nine Galaxies Based on a Statistical Analysis of their Carbon Stars (JAGB Method)
International audienceOur work presents an independent calibration of the J-region Asymptotic Giant Branch (JAGB) method using Infrared Survey Facility photometric data and a custom luminosity function profile to determine JAGB mean magnitudes for nine galaxies. We determine a mean absolute magnitude of carbon stars of MLMC = -6.212 ± 0.010 (stat.) ±0.030 (syst.) mag. We then use near-infrared photometry of a number of nearby galaxies, originally obtained by our group to determine their distances from Cepheids using the Leavitt law, in order to independently determine their distances with the JAGB method. We compare the JAGB distances obtained in this work with the Cepheid distances resulting from the same photometry and find very good agreement between the results from the two methods. The mean difference is 0.01 mag with an rms scatter of 0.06 mag after taking into account seven out of the eight analyzed galaxies that had their distances determined using Cepheids. The very accurate distance to the Small Magellanic Cloud based on detached eclipsing binaries is also in very good agreement with the distance obtained from carbon stars
New Near-Infrared Period-Luminosity-Metallicity Relations for Galactic RR Lyrae Stars Based on Gaia EDR3 Parallaxes
We present new period-luminosity and period-luminosity-metallicity relations
for Galactic RR Lyrae stars based on a sample of 28 pulsators located at
distances up to kpc from the Sun. Near-infrared photometry was obtained
at the Cerro Armazones Observatory and parallaxes were taken from the Gaia
Early Data Release 3. Relations were determined for the 2MASS bands and
the Wesenheit index. We compare our results with other calibrations
available in the literature and obtain very good agreement with the photometry
of RR Lyraes from the Large Magellanic Cloud anchored using the distance to the
Cloud, which based on detached eclipsing binaries. We find that the dependence
of absolute magnitudes on metallicity of mag/dex ( band)
to mag/dex ( index) for the population of fundamental
pulsators (RRab) that is in agreement with previously published
phenomenological works. We perform a refined determination of distance to the
LMC based on our new calibration and photometry from Szewczyk et al. (2008). We
study the dependence of the fitted parameters of fiducial relations and the LMC
distance on the systematic parallax offset.Comment: 32 pages, 9 figures, 9 tables. Accepted for publication in Ap
A Distance Determination to the Small Magellanic Cloud with an Accuracy of Better than Two Percent Based on Late-type Eclipsing Binary Stars
International audienc