2015A&A...581A..75K


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.08CEST03:47:09

2015A&A...581A..75K - Astronomy and Astrophysics, volume 581A, 75-75 (2015/9-1)

Interplay between pulsations and mass loss in the blue supergiant 55 Cygnus = HD 198478.

KRAUS M., HAUCKE M., CIDALE L.S., VENERO R.O.J., NICKELER D.H., NEMETH P., NIEMCZURA E., TOMIC S., ARET A., KUBAT J., KUBATOVA B., OKSALA M.E., CURE M., KAMINSKI K., DIMITROV W., FAGAS M. and POLINSKA M.

Abstract (from CDS):

Blue supergiant stars are known to display photometric and spectroscopic variability that is suggested to be linked to stellar pulsations. Pulsational activity in massive stars strongly depends on the star's evolutionary stage and is assumed to be connected with mass-loss episodes, the appearance of macroturbulent line broadening, and the formation of clumps in the wind. To investigate a possible interplay between pulsations and mass-loss, we carried out an observational campaign of the supergiant 55 Cyg over a period of five years to search for photospheric activity and cyclic mass-loss variability in the stellar wind. We modeled the H, HeI, SiII, and SiIII lines using the nonlocal thermal equilibrium atmosphere code FASTWIND and derived the photospheric and wind parameters. In addition, we searched for variability in the intensity and radial velocity of photospheric lines and performed a moment analysis of the line profiles to derive frequencies and amplitudes of the variations. The Hα line varies with time in both intensity and shape, displaying various types of profiles: PCygni, pure emission, almost complete absence, and double or multiple peaked. The star undergoes episodes of variable mass-loss rates that change by a factor of 1.7-2 on different timescales. We also observe changes in the ionization rate of SiII and determine a multiperiodic oscillation in the HeI absorption lines, with periods ranging from a few hours to 22.5-days. We interpret the photospheric line variations in terms of oscillations in p-, g-, and strange modes. We suggest that these pulsations can lead to phases of enhanced mass loss. Furthermore, they can mislead the determination of the stellar rotation. We classify the star as a post-red supergiant, belonging to the group of α Cyg variables.

Abstract Copyright:

Journal keyword(s): stars: early-type - supergiants - stars: winds, outflows - stars: mass-loss - stars: individual: 55 Cygnus - stars: activity

Simbad objects: 11

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Number of rows : 11

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 * bet Ori s*b 05 14 32.27210 -08 12 05.8981 -0.56 0.10 0.13 0.13 0.15 B8Iae 726 0
2 HD 50064 Em* 06 51 34.1060183287 +00 17 50.465846394 8.75 9.06 8.30 7.51 6.88 B6Ie 82 1
3 * alf Leo PM* 10 08 22.31099 +11 58 01.9516 0.88 1.24 1.40 1.37 1.47 B8IVn 807 1
4 HD 163899 Pu* 17 59 56.3484038559 -33 53 26.958683912 7.88 8.51 8.31 9.17 8.59 B2Ib/II 44 0
5 * zet Aql PM* 19 05 24.6080155 +13 51 48.518212 2.99 3.00 2.99 2.98 2.98 A0IV-Vnn 320 0
6 * 27 Vul * 20 37 04.6730582107 +26 27 43.000207301   5.528 5.583     B8V 61 0
7 * alf Cyg sg* 20 41 25.91514 +45 16 49.2197 1.11 1.34 1.25 1.14 1.04 A2Ia 716 0
8 * 55 Cyg s*b 20 48 56.2911163453 +46 06 50.883966851 4.83 5.28 4.86 4.41 4.10 B4Ia 470 0
9 HD 199478 s*b 20 55 49.8044819063 +47 25 03.561837777 5.79 6.12 5.64 5.16 4.78 B8Ia 212 0
10 Ass Cyg OB 7 As* 21 08 +47.6           ~ 193 0
11 * sig Cyg sg* 21 17 24.9524404 +39 23 40.852798 3.98 4.37 4.24 4.06 3.92 A0Ia 250 0

    Equat.    Gal    SGal    Ecl

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2020.07.08-03:47:09

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