2016A&A...587A.117B


C.D.S. - SIMBAD4 rel 1.7 - 2021.01.17CET14:48:23

2016A&A...587A.117B - Astronomy and Astrophysics, volume 587A, 117-117 (2016/3-1)

Observational calibration of the projection factor of Cepheids. II. Application to nine Cepheids with HST/FGS parallax measurements.

BREITFELDER J., MERAND A., KERVELLA P., GALLENNE A., SZABADOS L., ANDERSON R.I. and LE BOUQUIN J.-B.

Abstract (from CDS):

The distance to pulsating stars is classically estimated using the parallax-of-pulsation (PoP) method, which combines spectroscopic radial velocity (RV) measurements and angular diameter (AD) estimates to derive the distance of the star. A particularly important application of this method is the determination of Cepheid distances in view of the calibration of their distance scale. However, the conversion of radial to pulsational velocities in the PoP method relies on a poorly calibrated parameter, the projection factor (p-factor). We aim to measure empirically the value of the p-factors of a homogeneous sample of nine bright Galactic Cepheids for which trigonometric parallaxes were measured with the Hubble Space Telescope (HST) Fine Guidance Sensor. We use the SPIPS algorithm, a robust implementation of the PoP method that combines photometry, interferometry, and radial velocity measurements in a global modeling of the pulsation of the star. We obtained new interferometric angular diameter measurements using the PIONIER instrument at the Very Large Telescope Interferometer (VLTI), completed by data from the literature. Using the known distance as an input, we derive the value of the p-factor of the nine stars of our sample and study its dependence with the pulsation period. We find the following p-factors: p=1.20±0.12 for RT Aur, p=1.48±0.18 for T Vul, p=1.14±0.10 for FF Aql, p=1.31±0.19 for Y Sgr, p=1.39±0.09 for X Sgr, p=1.35±0.13 for W Sgr, p=1.36±0.08 for β Dor, p=1.41±0.10 for ζ Gem, and p=1.23±0.12 for l Car. The values of the p-factors that we obtain are consistently close to p=1.324±0.024. We observe some dispersion around this average value, but the observed distribution is statistically consistent with a constant value of the p-factor as a function of the pulsation period (χ2=0.669). The error budget of our determination of the p-factor values is presently dominated by the uncertainty on the parallax, a limitation that will soon be waived by Gaia.

Abstract Copyright:

Journal keyword(s): stars: variables: Cepheids - techniques: interferometric - methods: observational - stars: distances

Simbad objects: 26

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Number of rows : 26

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 5821 1
2 OGLE LMC-CEP-227 cC* 04 52 15.6982549282 -70 14 31.242341027     15.317   14.438 ~ 47 0
3 V* R Aur S* 05 17 17.6843537275 +53 35 10.022023539   7.8 6.5     M6.5-8.5e 220 0
4 HD 35199 * 05 18 43.9264159136 -62 59 05.812299983   8.63 7.20     K3III 11 0
5 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 15112 1
6 * bet Dor cC* 05 33 37.5125319201 -62 29 23.323100433 5.13 4.58 3.76 3.55 3.12 F8/G0Ib 350 0
7 HD 39608 * 05 49 36.4588461030 -60 40 34.656424199   8.91 7.35     K5III 14 0
8 * 48 Aur cC* 06 28 34.0875086 +30 29 34.914168 6.73 6.23 5.55   4.777 F5.5-G0Ib 363 0
9 HD 50607 * 06 54 39.7756889236 +15 50 16.595251486   7.49 6.55     G8III 8 0
10 * 37 Gem * 06 55 18.6667052671 +25 22 32.503802377   6.343 5.748     G0V 186 0
11 * zet Gem cC* 07 04 06.5307903 +20 34 13.073871 5.20 4.58 3.79   3.082 G1Ib 539 0
12 * 45 Gem PM* 07 08 22.0391813881 +15 55 50.435504329   6.507 5.476     G8III 46 0
13 * k Car * 09 20 56.8132949358 -62 24 16.681094270   5.733 4.800     G6III 37 0
14 HD 81502 * 09 23 27.3221863617 -60 18 08.332170463   7.758 6.265     K1/2II/III 21 0
15 * l Car cC* 09 45 14.8112246 -62 30 28.451894   4.33 3.40     G5Iab/b 293 1
16 HD 89805 * 10 19 42.0296617363 -65 08 14.052992414   7.88 6.30     K2II 13 0
17 * 32 Sco PM* 17 21 41.5617157118 -24 54 21.973256546   7.76 6.36     K3III 14 0
18 V* X Sgr cC* 17 47 33.6241002643 -27 49 50.848981593 5.84 5.34 4.54 6.03 3.661 F7II 312 0
19 * gam01 Sgr cC* 18 05 01.2265190154 -29 34 48.303215344 5.99 5.47 4.69   3.869 G0Ib/II 329 0
20 HD 166295 * 18 11 05.2169828438 -25 45 44.191159228   8.12 6.68     K2III/IV 13 0
21 * 1 Sgr * 18 11 43.3334213210 -23 42 04.434585800   6.03 4.98     K0III 38 0
22 V* Y Sgr cC* 18 21 22.9864295 -18 51 36.001763 7.31 6.69 5.75   4.810 F8II 272 0
23 HD 170499 * 18 30 53.6674235265 -27 57 06.320324920   9.58 7.73     K4III 10 0
24 V* FF Aql cC* 18 58 14.7482217777 +17 21 39.295590199 6.61 6.18 5.38     F6Ib 346 0
25 V* T Vul cC* 20 51 28.2382502598 +28 15 01.816605372 6.89 6.49 5.77   5.061 F5Ib+A0.8V 322 0
26 * del Cep cC* 22 29 10.2650184 +58 24 54.713856 4.71 4.35 3.75   3.219 F5Iab:+B7-8 685 0

    Equat.    Gal    SGal    Ecl

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2021.01.17-14:48:23

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