2002ApJ...567.1121E


C.D.S. - SIMBAD4 rel 1.7 - 2021.01.28CET10:28:35

2002ApJ...567.1121E - Astrophys. J., 567, 1121-1130 (2002/March-2)

Polaris: amplitude, period change, and companions.

EVANS N.R., SASSELOV D.D. and SHORT C.I.

Abstract (from CDS):

Polaris has presented us with the rare phenomenon of a Cepheid with a pulsation amplitude that has decreased over the last 50 yr. In this study we have used this property to see whether the amplitude decrease during the last 15 yr has had any effect on upper atmosphere heating. We obtained IUE high- and low-resolution spectra but found no change in either the Mg II chromospheric emission or the flux at 1800 Å between 1978 and 1993 when the pulsation amplitude dropped by 50% (from 2.8 to 1.6 km.s–1). The energy distribution from 1700 Å through V, B, R(KC), and I(KC) is like that of a nonvariable supergiant of the same color rather than a full amplitude Cepheid in that it has more flux at 1800 Å than the full amplitude Cepheid δ Cep. Polaris also has a rapidly changing period (3.2 s.yr–1), in common with other overtone pulsators. We argue that this is a natural consequence of the different envelope locations that dominate pulsation growth rates in fundamental and overtone pulsation. In fundamental mode pulsators, the deeper envelope is more important in determining growth rates than for overtone pulsators. For fundamental mode pulsators, evolutionary changes in the radius produce approximately linear changes in period. In overtone pulsators, pulsation reacts to small evolutionary changes in a more unstable way because the modes are more sensitive to high envelope features such as opacity bumps, and the growth rates for the many closely spaced overtone modes change easily. Finally, the upper limit to the X-ray flux from an Einstein observation implies that the companion in the astrometric orbit is earlier than F4 V. The combination of upper and lower limits on the companion from IUE and Einstein respectively catch the companion mass between 1.7 and 1.4 M. The X-ray limit is consistent with the more distant companion α UMi B being a physical companion in a hierarchal triple system. However the X-ray limits require that the even more distant companions α UMi C and D are too old to be physically associated with Polaris.

Abstract Copyright:

Journal keyword(s): Stars: Binaries: Visual - Stars: Variables: Cepheids - Stars: Atmospheres - stars: individual (Polaris, α Ursae Minoris) - Stars: Oscillations

Simbad objects: 34

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Number of rows : 34

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 * alf UMi B V* 02 30 36.0767975155 +89 15 39.204342239   8.69 8.20     F3V 32 0
2 UCAC3 359-247 * 02 30 44.3499682105 +89 14 29.697895265       14.07   ~ 10 0
3 * alf UMi cC* 02 31 49.09456 +89 15 50.7923 3.00 2.62 2.02 1.53 1.22 F8Ib 618 2
4 UCAC3 359-258 * 02 35 12.0586757382 +89 15 45.146655369       14.34   ~ 9 0
5 V* SU Cas cC* 02 51 58.7508894403 +68 53 18.601570075 6.92 6.44 5.80     F5.5III+ 411 1
6 * alf Per V* 03 24 19.3700924 +49 51 40.245455 2.64 2.27 1.79     F5Ib 805 1
7 Cl Melotte 20 OpC 03 26 42 +48 48.0           ~ 765 0
8 V* SZ Tau cC* 04 37 14.7778803229 +18 32 34.929341041 7.65 7.13 6.37     F6.7:Ib 290 0
9 * bet Cam * 05 03 25.0896309 +60 26 32.089527 5.57 4.95 4.02 3.33 2.86 G1Ib 167 0
10 * bet Lep ** 05 28 14.7231588 -20 45 33.987791 4.13 3.66 2.84 2.19 1.75 G5II-IIIa: 229 0
11 * bet Dor cC* 05 33 37.5125319201 -62 29 23.323100433 5.13 4.58 3.76 3.55 3.12 F8/G0Ib 351 0
12 * alf Car * 06 23 57.10988 -52 41 44.3810 -0.49 -0.59 -0.74 -0.96 -1.13 A9II 420 0
13 HD 47180 * 06 37 11.6578528540 -04 37 49.321702482   10.36 10.12     A0IV 3 0
14 * eps Gem V* 06 43 55.9262590 +25 07 52.051484 5.85 4.39 2.98 2.01 1.40 G8Ib 380 0
15 * zet Gem cC* 07 04 06.5307903 +20 34 13.073871 5.20 4.58 3.79   3.082 G1Ib 540 0
16 * j Pup * 07 56 51.5389962 -22 52 48.433986   4.900 4.184     F7/8II 100 0
17 * rho Pup dS* 08 07 32.6488235 -24 18 15.567946 3.43 3.24 2.81 2.46 2.25 F5IIkF2IImF5II 280 0
18 V* Y Car cC* 10 33 10.8510871240 -58 29 55.077771331   8.75 8.16     F0/3 132 0
19 HD 102350 Ce* 11 46 30.8225717 -61 10 42.236355   5.01 4.10     G5Ib/II 64 0
20 * bet Crv PM* 12 34 23.2348393 -23 23 48.337453 4.17 3.52 2.64 2.03 1.59 G5IIBa0.3 242 0
21 * del TrA * 16 15 26.2697841 -63 41 08.449198   4.943 3.839     G2Ib-IIa 98 0
22 * bet Dra * 17 30 25.9616959 +52 18 04.999351 4.43 3.79 2.81 2.12 1.64 G2Ib-IIa 394 0
23 * iot01 Sco s*y 17 47 35.0811299 -40 07 37.189349   3.492 2.992     F2Ia 105 0
24 V* Y Oph cC* 17 52 38.7021149511 -06 08 36.875163136 8.62 7.61 6.21     G3Ia 346 0
25 * d Dra * 18 32 34.5219746437 +57 02 44.141592388   5.380 4.761     F8Ib-II 134 0
26 V* V367 Sct cC* 18 33 35.2353194475 -10 25 38.130057884   13.34 11.580     ~ 155 0
27 * eps Sct * 18 43 31.2554790878 -08 16 30.805110638   5.998 4.889     G8IIb 84 0
28 V* V473 Lyr cC* 19 15 59.4894683081 +27 55 34.683764506 7.18 6.770 6.153     F8Ib-II 206 0
29 * bet Aql PM* 19 55 18.7925630 +06 24 24.342501 5.040 4.560 3.710 3.05 2.56 G8IV 518 0
30 * bet Aqr * 21 31 33.5317148 -05 34 16.232006 4.27 3.71 2.89 2.29 1.84 G0Ib 433 0
31 * 9 Peg V* 21 44 30.6958139 +17 21 00.057062 6.48 5.52 4.35 3.53 2.98 G5Ib 261 0
32 * alf Aqr * 22 05 47.0359315 -00 19 11.456766 4.65 3.90 2.94 2.27 1.76 G2Ib 423 0
33 * del Cep cC* 22 29 10.2650184 +58 24 54.713856 4.71 4.35 3.75   3.219 F5Iab:+B7-8 686 0
34 V* Z Lac cC* 22 40 52.1456104219 +56 49 46.083960286   9.71 8.57   7.164 F6Ib 212 0

    Equat.    Gal    SGal    Ecl

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2021.01.28-10:28:35

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