arXiv subjects

Grzegorz Pietrzyński

Publications and source records attributed to Grzegorz Pietrzyński.

At least 19 recordsLinked to original sources

arXiv2026

Interstellar extinction of classical Cepheids from neighboring stars I. Methodology and application to 16 Galactic Cepheids

Galactic Cepheid variable stars are fundamental calibrators of the cosmic distance scale through their Period-Luminosity (PL) relation. The high-precision parallaxes expected from Gaia Data Release 4 (DR4) will enable a calibration of the Milky Way PL relation with unprecedented precision. This will place stringent requirements on interstellar extinction corrections, which remain a dominant source of uncertainty. We strive to derive highly accurate extinction values for Galactic Cepheids. We present an innovative methodology relying on the analysis of neighboring field stars and apply it to a pilot sample of 16 Cepheids. We identify physically near field stars using Gaia DR3 astrometry. For these stars, we determine atmospheric parameters from medium- to high-resolution VLT/FLAMES spectroscopy. Fixing these parameters, we derive individual extinctions by fitting spectral energy distributions constructed from Gaia XP spectra and infrared photometry. We then reconstruct the three-dimensional distribution of extinction and interpolate extinction to the Cepheid position. We report extinction Av, total-to-selective extinction ratio Rv, and color excess E(B-V) for all 16 Cepheids. Our method achieves a mean precision of approximately 5%, improving upon typical literature values, with no significant systematic offset detected. We demonstrate that using field stars bypasses uncertainties associated with Cepheid variability and can provide robust extinction estimates for Galactic Cepheids.

astro-ph.GA↗

arXiv2026

HALO II: Constraining Hubble constant $H_{0}$ through continuum delay fitting of Fairall 9

The Hubble tension remains one of the most significant unresolved problems in modern cosmology. A key question is whether it may arise from underestimated systematic uncertainties in the different measurement techniques. In this context, new independent methods are of exceptional importance. We therefore pursue a novel approach to determining the Hubble constant, $H_{0}$ based on continuum time delay and spectral energy distribution (SED) modeling in active galactic nuclei (AGNs). Unlike conventional techniques, this method is entirely independent of the cosmic distance ladder and does not require cross-calibration against other distance indicators. As a result, it enables a direct determination of $H_{0}$, free from the arbitrary normalizations that often affect indirect measurements. We conducted a dedicated monitoring campaign of the Seyfert galaxy Fairall 9 and further developed the {\tt H0RIZON-AGN} model to interpret the resulting observations. The model incorporates the effects of radiation reprocessing in the surrounding cold accretion disk, enabling a more realistic description of the observed continuum delays. Through the simultaneous modeling of the continuum lag-spectrum and the broadband SED of Fairall 9, we derived a Hubble constant of $H_{0}=72.4_{-3.7}^{+3.4} \, \rm km \, s^{-1} \, Mpc^{-1}$. Achieving a measurement precision of approximately 5% from a single source demonstrates the considerable potential of this method for independent determinations of the Hubble constant. Our determination of $H_{0}$ is broadly consistent, within the current uncertainties, with both early- and late-Universe measurements. Future applications of the method to larger datasets, particularly those provided by the Vera Rubin Observatory, are expected to reduce the uncertainty to below 1%, thereby establishing this approach as a powerful independent probe of the Hubble tension.

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arXiv2026

Period-Luminosity Relations, projection factor and radii of Anomalous Cepheids

Anomalous Cepheids are radially pulsating stars observed in dwarf galaxies, the Galactic bulge and halo, and globular clusters. Similarly to other radially pulsating stars, they can be used as distance indicators through their Period-Luminosity Relations (PLRs) and the geometrical Baade-Wesselink (BW) method. We aim to calibrate the zero-point of the distance scale of Anomalous Cepheids using nearby representatives of this class of pulsating stars. We collected optical and near-infrared photometry and spectra for a sample of nearby Anomalous Cepheids with twotelescopes located at the Rolf Chini Cerro Murphy Observatory and optical telescopes offered by the Las Cumbres Observatory, and with instruments hosted and operated by the European Southern Observatory. Using parallaxesmeasured by the Gaia space mission and mean magnitudes from our new photometry, we calibrate the zero-point of the PLRs in Johnson B, V, 2MASS J, H, KS , and Pan-STARRS g, r, i passbands and selected Wesenheit indices. Using the surface brightness-colour relation version of the BW technique, we also determined the projection factors and mean radii of three nearby Anomalous Cepheids. Precision of the measured zero-points is at the level of 0.04-0.05mag and their systematic uncertainty is estimated to about 0.1mag. We used our zero-points and literature photometry of the Large Magellanic Cloud Anomalous Cepheids to measure the distance modulus of this galaxy and obtained a value of 18.454$\pm$0.045(statistical) mag, in a very good agreement with the most accurate value from eclipsing binaries. The obtained projection factors are 1.38$\pm$0.13, 1.59$\pm$0.21 and 1.35$\pm$0.14 for V716 Oph, XX Vir and UY Eri, respectively. The radii measured for V716 Oph and UY Eri are in agreement with the period-radius relation obtained from the Large Magellanic Cloud Anomalous Cepheids.

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arXiv2025

RR Lyrae stars with variable mean magnitudes

Context. A number of RR Lyrae stars show variable mean magnitudes in the OGLE survey light curves of the Galactic bulge. Hitherto this phenomenon was not studied, as it was generally assumed to be related to problems with the photometry. Aims. We investigate whether the mean magnitude variability of RR Lyrae variables is due to genuine astrophysical phenomena. Methods. We make use of the extended, and in many cases overlapping, light curves from multiple microlensing surveys, to study RR Lyrae stars with apparent mean-magnitude variations. A modified Fourier-series based fitting method is introduced to analyze the light curves showing mean-magnitude variations. Data from infrared surveys are also used to construct spectral energy distributions (SEDs). Results. 72 stars are presented where the mean-magnitude variations are most probably of genuine astrophysical origin, and not the result of problems with the photometry. The ratio of variation between the V and I bands is compatible with variable extinction by dust in most cases, but no infrared excess is detected in the SEDs. The occurrence rate of the phenomenon, after correcting for selection effects, is $\sim0.9\%$ among RR Lyrae variables in the OGLE bulge fields.

astro-ph.SR↗

arXiv2025

HALO I: Photometric continuum reverberation mapping of Fairall 9

We investigate the origin of inter-band continuum time delays in active galactic nuclei (AGNs) to study the structure and properties of their accretion disks. We aim to measure the inter-band continuum time delays through photometric monitoring of Seyfert galaxy Fairall 9 to construct the lag-spectrum. Additionally, we explain the observed features in the Fairall 9 lag-spectrum and discuss the potential drivers behind them, based on our newly collected data from the Obserwatorium Cerro Murphy (OCM) telescope. We initiated a long-term, continuous AGN photometric monitoring program in 2024, titled 'Hubble constant constraints through AGN Light curve Observations' (HALO) using intermediate and broad band filters. Here, we present the first results from HALO, focusing on photometric light curves and continuum time-delay measurements for Fairall 9. To complement these observations and extend the wavelength coverage of the lag-spectrum, we also reanalyzed archival Swift light curves and spectroscopic data available in the literature. Using HALO and Swift light curves, we measured inter-band continuum delays to construct the lag-spectrum of Fairall 9. Excess lags appear in the $u$ and $U$ bands (Balmer continuum contamination) and in the $I$ band (Paschen jump/dust emission from the torus). Overall, the lag-spectrum deviates significantly from standard disk model predictions. We find that inter-band delays deviate from the power-law, $τ_λ \propto λ^β$ due to BLR scattering, reprocessing, and dust contributions at longer wavelengths. Power-law fits are therefore not well suited for characterizing the nature of the time delays.

astro-ph.GA↗

arXiv2025

Distance to the Globular Cluster M 3 from the Infrared Surface Brightness Technique applied to RR Lyrae stars

The Infrared Surface Brightness (IRSB) technique is a specific application of the Baade-Wesselink method. Given a proper calibration, well covered optical and near-infrared photometry, as well as radial velocity curves, it allows for estimation of distances to individual pulsating stars and determination of their mean radii. The technique is fully empirical and does not depend on stellar atmosphere models. The goal of the work is to test the precision of distance determinations to individual RR Lyrae stars and to their host system as a whole using the IRSB technique for a relatively distant globular cluster M 3 (NGC 5272). We also aim to determine mean radii and period-radius relations for these stars in order to compare them with the existing theoretical prediction and empirical estimations for the field stars from the solar neighborhood. We use data available in the literature and the calibration of the IRSB technique based on the RR Lyrae stars from the solar neighborhood we published previously in order to determine distances to 14 RR Lyrae stars in the globular cluster M 3. We study the impact of the selection of the fitting procedure (bisector v.s. the LS fit) on the results. We apply five different empirical surface brightness-color relations from the literature in the analysis. We obtained a mean distance to M 3 of $r_{M3} = (10.07 \pm 0.19 \pm 0.29) \,kpc$ that corresponds to a distance modulus $μ_{M3} = (15.015 \pm 0.041 \pm 0.063) \,mag$ and a $7\%$ scatter of individual stellar distances for 14 RR Lyrae stars in M 3. We received a very good agreement between the two fitting techniques. We also determined mean stellar radii for pulsators from the sample with a precision of $0.5\%$ and obtained excellent agreement with a theoretical prediction of the period-radius relation for RRab stars available in the literature.

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arXiv2025

Secondary standards in the UKIRT faint standard fields

We present precise J- and K-band photometric measurements for 128 near-infrared secondary standard stars, located in the 19 UKIRT/MKO primary faint standard fields. The data were collected over more than 50 nights, covering a decade of observations between 2008 and 2018 at the ESO La Silla Observatory, using the New Technology Telescope (NTT) equipped with the SOFI NIR camera. Presented magnitudes are calibrated onto the MKO photometric system. The J- and K-band magnitudes range from 10 to 15.8 mag, with median values of $\tilde{J}$ = 13.5 and $\tilde{K}$ = 13 mag. The selection process ensured high photometric quality, with a precision better than 0.01 mag for all stars. The catalog excludes stars with close neighbors, high proper motion, or variable stars. Using these fields for standardization can improve the precision and accuracy of photometric calibrations without increasing the observational time cost.

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arXiv2024

The Infrared Surface Brightness technique applied to RR Lyrae stars from the solar neighborhood

The Baade-Wesselink method allows us to estimate distances to individual pulsating stars. Accurate geometric parallaxes obtained by the Gaia mission serve us in the calibration of the method and in the determination of its precision. The method also provides a way of determining mean radii of pulsating stars. The main aim of this work is to determine the scatter and possible dependence of p- factors of RR Lyrae stars on their pulsation periods. The secondary objective is to determine mean radius - period relations for these stars. Our calibrations for RR Lyrae stars are based on photometric data gathered at the Cerro Murphy Observatory. We obtained spectroscopic data specifically for this project using high resolution spectrographs. We use the Infrared Surface Brightness (IRSB) version of the method that relies on a surface brightness - color relation dependent on the (V-K) color. We obtain the spread of p- factors of around 0.07-0.08 for our sample of 9 RR Lyrae stars from the solar neighborhood. However, we also find relations between the p-factor and the pulsation period for RRab stars with the rms scatter around the relation of around 0.05, but with relatively large uncertainty of relations' parameters. We present relations between the mean radius and period for RR Lyrae pulsating in the fundamental mode with the rms scatter around the relation of $0.012R_{\odot}$. We observe a clear offset between p- factors obtained using the IRSB technique (with mean p between 1.39 and 1.45) and values inferred by Bras et al. (2024) using the SPIPS tool (Mérand et al. 2015). On the other hand, we obtain a similar scatter of p of as observed by Bras et al. (2024). Our period-radius relations are in a good agreement with both the inference of Bras et al. (2024) based on SPIPS and theoretical predictions of Marconi et al. (2005, 2015)

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arXiv2024

Projection factor and radii of Type II Cepheids

Type II Cepheids are old pulsating stars that can be used to trace the distribution of an old stellar population and to measure distances to globular clusters and galaxies within several megaparsecs. One method that can be used to measure the distances of Type II Cepheids relies on period-luminosity relations, which are quite widely explored in the literature. The semi-geometrical Baade-Wesselink technique is another method that allows distances of radially pulsating stars, such as Type II Cepheids, to be measured if the so-called projection factor is known. Using the surface brightness-colour relation version of the Baade-Wesselink technique, we determined the projection factors and radii of eight nearby BL Her type stars. We adopted accurate distances of target stars from Gaia Data Release 3. Time series photometry in the V and K bands have been collected with two telescopes located at the Rolf Chini Cerro Murphy Observatory, while spectroscopic data have been obtained with instruments hosted by the European Southern Observatory. The measured projection factors for the stars with good quality data are in the range between 1.21 and 1.36. The typical uncertainty of projection factors is 0.1. The mean value is 1.330$\pm$0.058, which gives the uncertainty of $\sim$4%. The main sources of uncertainty on the p-factors are statistical errors of the Baade-Wesselink fit and parallax. In the case of radii, the biggest contribution to the error budget comes from the K band photometry systematic uncertainty and parallax. The determined radii allowed us to construct the period-radius relation for BL Her stars. Our period-radius relation is in good agreement with the previous empirical calibration, while two theoretical calibrations found in the literature agree with our relation within 2$σ$. We also confirm that BL Her and RR Lyr stars obey an apparent common period-radius relation.

astro-ph.SR↗

arXiv2024

Cepheids with giant companions. II. Spectroscopic confirmation of nine new double-lined binary systems composed of two Cepheids

Binary Cepheids with giant companions are crucial for studying the physical properties of Cepheid variables, providing the best means to measure their masses. Systems composed of two Cepheids are even more important but to date, only one such system in the Large Magellanic Cloud (LMC) was known. Our current aim is to increase the number of these systems tenfold and provide their basic characteristics. The final goal is to obtain the physical properties of the component Cepheids, including their masses and radii, and to learn about their evolution in the multiple systems, also revealing their origin. We started a spectroscopic monitoring of nine unresolved pairs of Cepheids from the OGLE catalog, to check if they are gravitationally bound. Two of these so-called double Cepheids are located in the LMC, five in the Small Magellanic Cloud (SMC), and two in the Milky Way (MW). We report the spectroscopic detection of binarity of all 9 of these double Cepheids with orbital periods from 2 to 18 years. This increases the number of known binary double (BIND) Cepheids from 1 to 10 and triples the number of all confirmed double-lined binary (SB2) Cepheids. For five BIND Cepheids disentangled pulsational light curves of the components show anti-correlated phase shifts due to orbital motion. We show the first empirical evidence that typical period-luminosity relations (PLRs) are rather binary Cepheid PLRs that include the companion's light. The statistics of pulsation period ratios of BIND Cepheids do not agree with those expected for pairs of the same-age Cepheids. These ratios together with the mass ratios far from unity suggest merger-origin of at least one component for about half of the systems. The SMC and MW objects are the first found in SB2 systems composed of giants in their host galaxies. The Milky Way BIND Cepheids are also the closest such systems, being located at about 11 and 26 kpc.

astro-ph.SR↗

arXiv2024

The Baade-Wesselink projection factor of RR Lyrae stars -- Calibration from OHP/SOPHIE spectroscopy and Gaia DR3 parallaxes

The application of the parallax of pulsation (PoP) technique to determine distances of pulsating stars implies the use of a scaling parameter, the projection factor (p-factor), required to transform disc-integrated radial velocities (RVs) into photospheric expansion velocities. The value of the p-factor is poorly known and debated. Most PoP applications assume a constant p-factor. However, it may actually depend on the physical parameters of each star. We aim to calibrate p-factors for RR Lyrae stars (RRLs) and compare them with classical Cepheids (CCs). Due to their higher surface gravity, RRLs have more compact atmospheres, and provide a valuable comparison with their supergiant siblings. We determined the p-factor of 17 RRLs using the SPIPS code, constrained by Gaia DR3 parallaxes, photometry, and new RVs from the OHP/SOPHIE spectrograph. We carefully examine the different steps of the PoP technique, particularly the method to determine RV from spectra using the classical cross-correlation function (CCF) approach. The method employed for RV extraction from the CCF has a strong impact on the p-factor, of up to 10%. However, this choice of method results in a global scaling of the p-factor, marginally affecting the scatter within the sample for a given method. Over our RRL sample, we find a mean value of $p = 1.248 \pm 0.022$ for RVs derived using a Gaussian fit of the CCF. There is no evidence for a different value of the p-factor of RRLs, although its distribution for RRLs appears significantly less scattered than that for CCs. The p-factor does not appear to depend in a simple way on fundamental stellar parameters. We argue that large-amplitude dynamical phenomena occurring in the atmospheres of RRLs and CCs during their pulsation affect the relative velocity of the spectral line-forming regions compared to the velocity of the photosphere.

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arXiv2023

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 $1.5$ 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 $JHK_s$ bands and the $W_{JK}$ 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 $0.070\pm 0.042$ mag/dex ($J-$ band) to $0.087 \pm 0.031$ mag/dex ($W_{JK}$ 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.

astro-ph.SR↗

arXiv2023

Synthetic population of binary Cepheids. I. The effect of metallicity and initial parameter distribution on characteristics of Cepheids' companions

The majority of classical Cepheids are binary stars, yet the contribution of companions' light to the total brightness of the system has been assumed negligible and lacked a thorough, quantitative evaluation. We present an extensive study of synthetic populations of binary Cepheids, that aims to characterize Cepheids' companions (e.g. masses, evolutionary and spectral types), quantify their contribution to the brightness and color of Cepheid binaries, and assess the relevance of input parameters on the results. We introduce a collection of synthetic populations, which vary in metal content, initial parameter distribution, location of the instability strip edges, and star formation history. Our synthetic populations are free from the selection bias, while the percentage of Cepheid binaries is controlled by the binarity parameter. We successfully reproduce recent theoretical and empirical results: the percentage of binary Cepheids with main sequence (MS) companions, the contrast-mass ratio relation for binary Cepheids with MS companions, the appearance of binary Cepheids with giant evolved companions as outlier data points above the period-luminosity relation. Moreover, we present the first estimation of the percentage of binary Cepheids in the Large Magellanic Cloud and announce the quantification of the effect of binarity on the slope and zero-point of multiband period-luminosity relations, which will be reported in the next paper of this series.

astro-ph.SR↗

arXiv2023

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-Lemaître constant $H_0$. 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 $H_0$, which however does not prevent measuring $H_0$ with a precision of 1%.

astro-ph.GA↗

arXiv2022

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.

astro-ph.SR↗

arXiv2021

An absolute calibration of the near-infrared Period-Luminosity Relations of Type II Cepheids in the Milky Way and in the Large Magellanic Cloud

We present time-series photometry of 21 nearby Type II Cepheids in the near-infrared J, H and Ks passbands. We use this photometry, together with the Third Gaia Early Data Release parallaxes, to determine for the first time period-luminosity relations (PLRs) for Type II Cepheids from field representatives of these old pulsating stars in the near-infrared regime. We found PLRs to be very narrow for BL Herculis stars, which makes them candidates for precision distance indicators. We then use archival photometry and the most accurate distance obtained from eclipsing binaries to recalibrate PLRs for Type II Cepheids in the Large Magellanic Cloud (LMC). Slopes of our PLRs in the Milky Way and in the LMC differ by slightly more than 2σ and are in a good agreement with previous studies of the LMC, Galactic Bulge and Galactic Globular Clusters Type II Cepheids samples. We use PLRs of Milky Way Type II Cepheids to measure the distance to the LMC and we obtain a distance modulus of 18.540$\pm$0.026(stat.)$\pm$0.034(syst.)mag in the WJKs Wesenheit index. We also investigate the metallicity effect within our Milky Way sample and we find rather significant value of about -0.2mag/dex in each band meaning that more metal-rich Type II Cepheids are intrinsically brighter than their more metal-poor counterparts, in agreement with the value obtained from Type II Cepheids in Galactic Globular Clusters. The main source of systematic error on our Milky Way PLRs calibration and the LMC distance is the current uncertainty of the Gaia parallax zero point.

astro-ph.SR↗

arXiv2021

Studies of RR Lyrae Variables in Binary Systems. I.: Evidence of a Trimodal Companion Mass Distribution

We present 87 candidates for RR Lyrae variable stars in binary systems, based on our new search using the light-travel time effect (LTTE) and observed - calculated ($O-C$) diagrams in the Galactic bulge time-series photometry of the Optical Gravitational Lensing Experiment. Out of these, 61 are new candidates, while 26 have been announced previously. Furthermore, 12 stars considered as binary candidates in earlier works are discarded from the list, either as they were found to have $O-C$ diagrams incompatible with the LTTE or because their long-term periodicity is definitely caused by the Blazhko effect. This sample of RR Lyrae binary candidates allows us to draw the first firm conclusions about the population of such objects: no candidate has an orbital period below 1000 days, while their occurrence rate steadily increases with increasing period, and peaks between 3000 and 4000 days; however, the decrease in the number of stars toward even longer periods is probably the result of observational biases. The eccentricities show a very significant concentration between 0.25 and 0.3, with a quarter of candidates found in this single bin, overlaid on an otherwise flat distribution between 0.05 and 0.6. Only six stars have higher inferred eccentricities above 0.6. Lastly, the distribution of the mass functions is highly peculiar, exhibiting strong trimodality. We interpret these modes as the presence of three distinct groups of companions, with typical inferred masses of $\sim0.6$, $\sim0.2$, and $\sim0.067\,\mathrm{M}_\odot$, which can be associated with populations of white dwarf and main sequence, red dwarf, and brown dwarf companions, respectively.

astro-ph.SR↗

arXiv2021

The Araucaria Project. Distances to Nine Galaxies Based on a Statistical Analysis of their Carbon Stars (JAGB Method)

Our work presents an independent calibration of the J-region Asymptotic Giant Branch (JAGB) method using Infrared Survey Facility (IRSF) 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 $M_{LMC}=-6.212 \pm 0.010$ (stat.) $\pm 0.030$ (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 (SMC) based on detached eclipsing binaries (Graczyk et al. 2020) is also in very good agreement with the distance obtained from carbon stars.

astro-ph.GA↗