2003MNRAS.341.1141S

2003MNRAS.341.1141S - Mon. Not. R. Astron. Soc., 341, 1141-1150 (2003/June-1)

Spectral response of the pulsationally induced shocks in the atmosphere of BW Vulpeculae.

BW Vulpeculae (BW Vul) is remarkable for exciting an extremely strong radial pulsation mode which grows through its outer envelope and forms visible shock features in the atmosphere. Material propelled upwards by the shock returns violently to the lower photosphere where it creates a second shock just before the start of the next cycle. We have obtained three nights of echelle data for this star over about five pulsation cycles (P=0.201d) in 2000 September in order to investigate the effects of atmospheric shocks on important lines in the optical red spectrum. These lines include Heiλ5875 and λ6678, Ciiλλ6578-83 doublet, and other moderate and high excitation lines. To these data we have added 37 archival IUE/SWP echelle spectra obtained in 1994. We have investigated the equivalent widths and shapes of the optical lines for evidence of inter alia lags and have compared our results to the IUE fluxes extracted from the far-ultraviolet continuum, Heiiλ1640, and several resonance lines.

A comparison of Heiλ5875 and λ6678 line profiles during the peak of the infall activity suggests that differences in the development of a second blue lobe in the profile at this time are due to heating and a short-lived formation of an optically thin layer above the region compressed by the infall. This discovery and the well-known decreases in equivalent widths of the Cii doublet at the two shock phases further suggest that shock heating flattens the atmospheric temperature gradient.

Except for evidence of wind absorption in the far blue wings of the ultraviolet resonance lines, we find no evidence for a shock delay arriving at different photospheric strata (i.e., a `Van Hoof effect'). Line-to-line differences in the relative strengths of double lobes can be false indicators arising from varying degrees of desaturation of multiple lines, such as for the red Hei lines.

Journal keyword(s): line: formation - line: profiles - shock waves - stars: individual: BW Vul - stars: variables: other

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	V* BW Vul	bC*	20 54 22.3947588600	+28 31 19.190976132	5.47	6.40	6.54			B2IIIv	301	0

Identifier

Otype

ICRS (J2000)
RA

ICRS (J2000)
DEC

Mag U

Mag B

Mag V

Mag R

Mag I

Sp type

#ref
1850 - 2026

#notes

V* BW Vul

bC*

20 54 22.3947588600

+28 31 19.190976132

5.47

6.40

6.54

B2IIIv

301

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`HD 199140`	`HGAM 963`	`ROT 3052`	*`V BW Vul`**
`AG+28 2353`	`HIC 103191`	`SAO 89265`	`WEB 18741`
`ALS 14834`	`HIP 103191`	`SKY# 39690`	`WISEA J205422.40+283119.0`
`AN 226.1937`	`HR 8007`	`TD1 27433`	`WISE J205422.39+283119.1`
`BD+27 3909`	`IRAS 20522+2819`	`TIC 419354107`	`YZ 28 11893`
`GC 29171`	`2MASS J20542238+2831192`	`TYC 2183-2731-1`	`AAVSO 2050+28`
`GCRV 13125`	`MCW 957`	`UBV 21418`	`Gaia DR3 1845911110565337472`
`GEN# +1.00199140`	`N30 4627`	`UBV M 25259`	`Gaia DR2 1845911110565337472`
`GSC 02183-02731`	`PPM 112113`	`uvby98 100199140`

`HD 199140`	`AG+28 2353`	`ALS 14834`	`BD+27 3909`	`GSC 02183-02731`
`HIC 103191`	`HIP 103191`	`HR 8007`	`IRAS 20522+2819`	`2MASS J20542238+2831192`
`PPM 112113`	`SAO 89265`	`TD1 27433`	`TYC 2183-2731-1`	`uvby98 100199140`
*`V BW Vul`**	`WISEA J205422.40+283119.0`	`WISE J205422.39+283119.1`	`Gaia DR3 1845911110565337472`	`Gaia DR2 1845911110565337472`