2018ApJ...853...55B


C.D.S. - SIMBAD4 rel 1.7 - 2019.10.18CEST02:00:05

2018ApJ...853...55B - Astrophys. J., 853, 55-55 (2018/January-3)

Hubble Space Telescope trigonometric parallax of Polaris B, companion of the nearest Cepheid.

BOND H.E., NELAN E.P., EVANS N.R., SCHAEFER G.H. and HARMER D.

Abstract (from CDS):

Polaris, the nearest and brightest Cepheid, is a potential anchor point for the Leavitt period-luminosity relation. However, its distance is a matter of contention, with recent advocacy for a parallax of ∼10 mas, in contrast with the Hipparcos measurement of 7.54 ± 0.11 mas. We report an independent trigonometric parallax determination, using the Fine Guidance Sensors (FGS) on the Hubble Space Telescope. Polaris itself is too bright for FGS, so we measured its eighth-magnitude companion Polaris B, relative to a network of background reference stars. We converted the FGS relative parallax to absolute, using estimated distances to the reference stars from ground-based photometry and spectral classification. Our result, 6.26 ± 0.24 mas, is even smaller than that found by Hipparcos. We note other objects for which Hipparcos appears to have overestimated parallaxes, including the well-established case of the Pleiades. We consider possible sources of systematic error in the FGS parallax, but find no evidence they are significant. If our "long" distance is correct, the high luminosity of Polaris indicates that it is pulsating in the second overtone of its fundamental mode. Our results raise several puzzles, including a long pulsation period for Polaris compared to second-overtone pulsators in the Magellanic Clouds, and a conflict between the isochrone age of Polaris B (∼2.1 Gyr) and the much younger age of Polaris A. We discuss possibilities that B is not a physical companion of A, in spite of the strong evidence that it is, or that one of the stars is a merger remnant. These issues may be resolved when Gaia provides parallaxes for both stars.

Abstract Copyright: © 2018. The American Astronomical Society. All rights reserved.

Journal keyword(s): astrometry - stars: distances - stars: evolution - stars: individual: Polaris - stars: variables: Cepheids - stars: variables: Cepheids

Simbad objects: 17

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Number of rows : 17

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 9089 1
2 NAME Polaris Cirrus Cloud MoC 01 52 29.6 +87 40 31           ~ 69 0
3 * alf UMi B V* 02 30 33.534 +89 15 38.90   8.69 8.20     F3V 32 0
4 * alf UMi D * 02 30 44.3499682105 +89 14 29.697895265     12.1 14.07   ~ 10 0
5 * alf UMi cC* 02 31 49.09456 +89 15 50.7923 3.00 2.62 2.02 1.53 1.22 F8Ib 601 2
6 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 5375 1
7 Cl Melotte 22 OpC 03 47 00 +24 07.0           ~ 2908 0
8 V* SY Aur cC* 05 12 39.2271412155 +42 49 54.415802821   9.97 9.05   7.851 F5III 111 0
9 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 14324 1
10 V* CO Aur cC* 06 00 28.5064814052 +35 18 43.856781674   8.34 7.73     F5Ib 83 0
11 V* SS CMa cC* 07 26 07.1974608016 -25 15 26.439068915   10.99 9.84     ~ 87 0
12 V* RS Pup cC* 08 13 04.2157137938 -34 34 42.691837063 8.89 8.00 6.70   5.453 F8Iab 309 1
13 HD 84937 PM* 09 48 56.09801 +13 44 39.3237 8.49 8.68 8.32 7.97 7.70 F8Vm-5 705 0
14 NAME Polaris Flare MoC 11 00 14.8 +86 10 52           ~ 157 1
15 V* RT Vir AB* 13 02 37.9836301550 +05 11 08.360733054 10.07 9.07 7.41     M8III 292 0
16 * kap Pav WV* 18 56 57.0309200480 -67 14 00.566631622   5.08 4.40     G5Iab/b 116 0
17 V* V473 Lyr cC* 19 15 59.4894683081 +27 55 34.683764506 7.18 6.770 6.153     F8Ib-II 202 0

    Equat.    Gal    SGal    Ecl

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2019.10.18-02:00:05

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