Erratum: “The Araucaria Project: First Cepheid Distance to the Sculptor Group Galaxy NGC 7793 From Variables Discovered in a Wide-Field Imaging Survey” (2010, Aj, 140, 1475)

Pietrzyński, G.; Gieren, W.; Hamuy, M.; Pignata, G.; Soszyński, I.; Udalski, A.; Walker, A. R.; Fouqué, P.; Bresolin, Fabio; Kudritzki, Rolf‐Peter; García-Varela, A.; Szewczyk, O.; Szymański, M. K.; Kubiak, M.; Wyrzykowski, Ł.

doi:10.1088/0004-6256/142/5/178

Cited by 17 publications

(25 citation statements)

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“…The LMC distance modulus of 18.45 ± 0.04 is only slightly shorter than the "canonical" value of 18.50 ± 0.10 as adopted by Freedman et al (2001) and by the ARAUCARIA project (Gieren et al 2005b;Pietrzyński et al 2010a), and slightly longer than the value of 18.39 ±0.01(random)±0.07(systematic) suggested by Freedman & Madore (2010) in their recent review. It is thus in good agreement with most recent results, as would be expected considering that we (see Paper I) have calibrated the IRSB method to match the distances to nine Milky Way Cepheids with direct parallaxes from Benedict et al (2007).…”

Section: Discussionmentioning

confidence: 52%

Calibrating the Cepheid period-luminosity relation from the infrared surface brightness technique

Storm

Gieren

Fouqué

et al. 2011

A&A

109

111

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Context. The extragalactic distance scale builds directly on the Cepheid period-luminosity (PL) relation as delineated by the sample of Cepheids in the Large Magellanic Cloud (LMC). However, the LMC is a dwarf irregular galaxy, quite different from the massive spiral galaxies used for calibrating the extragalactic distance scale. Recent investigations suggest that not only the zero-point but also the slope of the Milky Way PL relation differ significantly from that of the LMC, casting doubts on the universality of the Cepheid PL relation. Aims. We want to make a differential comparison of the PL relations in the two galaxies by delineating the PL relations using the same method, the infrared surface brightness method (IRSB), and the same precepts. We furthermore extend the metallicity baseline for investigating the zero-point dependence, by applying the method to five SMC Cepheids as well. Methods. The IRSB method is a Baade-Wesselink type method to determine individual distances to Cepheids. We apply a newly revised calibration of the method as described in an accompanying paper (Paper I) to 36 LMC and five SMC Cepheids and delineate new PL relations in the V, I, J, & K bands as well as in the Wesenheit indices in the optical and near-IR. Results. We present 509 new and accurate radial velocity measurements for a sample of 22 LMC Cepheids, enlarging our earlier sample of 14 stars to include 36 LMC Cepheids. The new calibration of the IRSB method is directly tied to the recent HST parallax measurements to ten Milky Way Cepheids, and we find a LMC barycenter distance modulus of 18.45 ± 0.04 (random error only) from the 36 individual LMC Cepheid distances. In the J, K bands we find identical slopes for the LMC and Milky Way PL relations and only a weak letallicity effect on the zero points (consistent with a zero effect), metal poor stars being fainter. In the optical we find the Milky Way slopes are slightly shallower than the LMC slopes (but again consistent with no difference in the slopes) and small effects on the zero points. However, the important Wesenheit index in V, (V − I) shows a metallicity effect on the slope and on the zero point which is likely to be significant. Conclusions. We find a significant metallicity effect on the W VI index γ(W VI ) = −0.23 ± 0.10 mag dex −1 as well as an effect on the slope. The K-band PL relation on the other hand is found to be an excellent extragalactic standard candle being metallicity insensitive in both slope and zero-point and at the same time being reddening insensitive and showing the least internal dispersion.

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Section: Discussionmentioning

confidence: 52%

Calibrating the Cepheid period-luminosity relation from the infrared surface brightness technique

Storm

Gieren

Fouqué

et al. 2011

A&A

109

111

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“…Finally, we summarise our conclusions in Section 7. Throughout this work, we adopt a distance to NGC 7793 of 3.5 Mpc (Pietrzyński et al 2010). …”

Section: Introductionmentioning

confidence: 99%

Super-Eddington accretion on to the neutron star NGC 7793 P13: Broad-band X-ray spectroscopy and ultraluminous X-ray sources

Walton

Fürst

Harrison

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present a detailed, broadband X-ray spectral analysis of the ULX pulsar NGC 7793 P13, a known super-Eddington source, utilizing data from the XMM-Newton, NuSTAR and Chandra observatories. The broadband XMM-Newton+NuSTAR spectrum of P13 is qualitatively similar to the rest of the ULX sample with broadband coverage, suggesting that additional ULXs in the known population may host neutron star accretors. Through time-averaged, phaseresolved and multi-epoch studies, we find that two non-pulsed thermal blackbody components with temperatures ∼0.5 and 1.5 keV are required to fit the data below 10 keV, in addition to a third continuum component which extends to higher energies and is associated with the pulsed emission from the accretion column. The characteristic radii of the thermal components appear to be comparable, and are too large to be associated with the neutron star itself, so the need for two components likely indicates the accretion flow outside the magnetosphere is complex. We suggest a scenario in which the thick inner disc expected for super-Eddington accretion begins to form, but is terminated by the neutron star's magnetic field soon after its onset, implying a limit of B 6 × 10 12 G for the dipolar component of the central neutron star's magnetic field. Evidence of similar termination of the disc in other sources may offer a further means of identifying additional neutron star ULXs. Finally, we examine the spectrum exhibited by P13 during one of its unusual 'off' states. These data require both a hard powerlaw component, suggesting residual accretion onto the neutron star, and emission from a thermal plasma, which we argue is likely associated with the P13 system.

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“…As such, Cepheids are used to measure distances to other galaxies (e.g. Pietrzyński et al 2010), and cosmological parameters (Freedman et al 2001;Riess et al 2009Riess et al , 2011, but the Leavitt law must be calibrated using Galactic (e.g. Turner 2010) and Large Magellanic Cloud (LMC) Cepheids (e.g.…”

Section: Introductionmentioning

confidence: 99%

Cepheid limb darkening, angular diameter corrections, and projection factor from static spherical model stellar atmospheres

Neilson

Nardetto

Ngeow

et al. 2012

A&A

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Context. One challenge for measuring the Hubble constant using classical Cepheids is the calibration of the Leavitt law or periodluminosity relationship. The Baade-Wesselink method for distance determination to Cepheids relies on the ratio of the measured radial velocity and pulsation velocity, the so-called projection factor and the ability to measure the stellar angular diameters. Aims. We use spherically-symmetric model stellar atmospheres to explore the dependence of the p-factor and angular diameter corrections as a function of pulsation period. Methods. Intensity profiles are computed from a grid of plane-parallel and spherically-symmetric model stellar atmospheres using the SAtlas code. Projection factors and angular diameter corrections are determined from these intensity profiles and compared to previous results. Results. Our predicted geometric period-projection factor relation including previously published state-of-the-art hydrodynamical predictions is not with recent observational constraints. We suggest a number of potential resolutions to this discrepancy. The model atmosphere geometry also affects predictions for angular diameter corrections used to interpret interferometric observations, suggesting corrections used in the past underestimated Cepheid angular diameters by 3-5%. Conclusions. While spherically-symmetric hydrostatic model atmospheres cannot resolve differences between projection factors from theory and observations, they do help constrain underlying physics that must be included, including chromospheres and mass loss. The models also predict more physically-based limb-darkening corrections for interferometric observations.

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Erratum: “The Araucaria Project: First Cepheid Distance to the Sculptor Group Galaxy NGC 7793 From Variables Discovered in a Wide-Field Imaging Survey” (2010, Aj, 140, 1475)

Cited by 17 publications

References 0 publications

Calibrating the Cepheid period-luminosity relation from the infrared surface brightness technique

Calibrating the Cepheid period-luminosity relation from the infrared surface brightness technique

Super-Eddington accretion on to the neutron star NGC 7793 P13: Broad-band X-ray spectroscopy and ultraluminous X-ray sources

Cepheid limb darkening, angular diameter corrections, and projection factor from static spherical model stellar atmospheres

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