2015MNRAS.447.2378O

2015MNRAS.447.2378O - Mon. Not. R. Astron. Soc., 447, 2378-2386 (2015/March-1)

Pulsations in B-type supergiants with masses M<20M_☉ before and after core helium ignition.

Evolutionary tracks and pulsational analysis of models with masses of 13-18M_☉ are presented. We address two important questions. The first one deals with one of the most unresolved problems in astrophysics, i.e. the existence of a blue loop after core helium ignition; the so-called to loop or not to loop problem. We show that inward overshooting from the outer convective zone in the red giant phase is prerequisite for the development of the blue loop. Our second question concerns pulsational instability of models in the core helium burning phase. We present for the first time that models on the blue loop can have unstable modes driven by the κ mechanism operating in the Z-bump. Contrary to post-main-sequence models in the shell hydrogen burning phases, pulsational instability of the blue loop models depends mainly on effective temperature and metallicity is of secondary importance. Finally, we try to interpret the oscillation spectrum of the blue supergiant HD 163899, the only member of the slowly pulsating B-type supergiant class and to get some clue on the evolutionary status of the star.

N	Identifier	Otype	ICRS (J2000) RA	ICRS (J2000) DEC	Mag U	Mag B	Mag V	Mag R	Mag I	Sp type	#ref 1850 - 2026	#notes
1	HD 163899	Pu*	17 59 56.3483552352	-33 53 26.956220568	7.88	8.51	8.31	9.17	8.59	B2Ib/II	53	0

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`HD 163899`	`GSC 07386-01636`	`TD1 21320`	`[SC95] M 174`
`ALS 4522`	`Hbg 1515`	`TIC 263573669`	`[SC96] GC 308`
`CD-33 12697`	`LS 4522`	`TYC 7386-1636-1`	`[SC96] Mis 853`
`CPC 17 9618`	`2MASS J17595635-3353269`	`UBV M 22505`	`Gaia DR2 4042411609752563200`
`CPD-33 4748`	`PPM 297102`	`UCAC2 17570275`	`Gaia DR3 4042411609752563200`
`DENIS J175956.4-335327`	`RAVE J175956.3-335327`	`UCAC4 281-150145`	`Gaia DR1 4042411605403632896`
`GEN# +1.00163899`	`SAO 209568`	`uvby98 100163899`

`HD 163899`	`ALS 4522`	`CD-33 12697`	`CPD-33 4748`	`DENIS J175956.4-335327`
`GSC 07386-01636`	`LS 4522`	`2MASS J17595635-3353269`	`PPM 297102`	`RAVE J175956.3-335327`
`SAO 209568`	`TD1 21320`	`TYC 7386-1636-1`	`UCAC2 17570275`	`UCAC4 281-150145`
`uvby98 100163899`	`Gaia DR2 4042411609752563200`	`Gaia DR3 4042411609752563200`	`Gaia DR1 4042411605403632896`