J/A+A/643/A22 UVES spectra of Feige 46 and LSIV -14 116 (Dorsch+, 2020)
Heavy-metal enrichment of intermediate He-sdOB stars:
the pulsators Feige 46 and LS IV -14 116 revisited.
Dorsch M., Latour M., Heber U., Irrgang A., Charpinet S., Jeffery C.S.
<Astron. Astrophys. 643, A22 (2020)>
=2020A&A...643A..22D 2020A&A...643A..22D (SIMBAD/NED BibCode)
ADC_Keywords: Stars, subdwarf ; Spectra, ultraviolet
Keywords: stars: abundances - stars: chemically peculiar - stars: oscillations -
subdwarfs - stars: individual: LS IV-14 116 -
stars: individual: Feige 46
Abstract:
Hot subdwarf stars of spectral types O and B represent a poorly
understood phase in the evolution of low-mass stars, in particular of
close compact binaries.
A variety of phenomena are observed, which make them important tools
for several astronomical disciplines.
For instance, the richness of oscillations of many subdwarfs are
important for asteroseismology.
Furthermore, hot subdwarfs are among the most chemically peculiar
stars known. Two intermediate He-rich hot subdwarf stars, LSIV -14 116
and Feige 46, are particularly interesting, because they show extreme
enrichments of heavy elements such as Ge, Sr, Y, and Zr, strikingly
similar in both stars.
In addition, both stars show light oscillations at periods
incompatible with standard pulsation theory and form the class of V366
Aqr variables. We investigate whether the similar chemical
compositions extend to more complete abundance patterns in both stars
and validate the pulsations in Feige 46 using its recent TESS light
curve. High-resolution optical and near-ultraviolet spectroscopy are
combined with non-local-thermodynamical-equilibrium model atmospheres
and synthetic spectra calculated with Tlusty and Synspec to determine
detailed metal abundance patterns in both stars consistently.
Many previously unidentified lines are identified for the first time
with transitions originating from GaIII, GeIII-IV, SeIII, KrIII,
SrII-III, YIII, ZrIII-IV, and SnIV, most of which have not been
observed so far in any star. The abundance patterns of 19 metals in
both stars are almost identical, light metals being only slightly more
abundant in Feige 46 while Zr, Sn, and Pb are slightly less enhanced
compared to LSIV -14 116. Both abundance patterns are distinctively
different from those of normal He-poor hot subdwarfs of similar
temperature. The extreme enrichment in heavy metals of more than 4 dex
compared to the Sun is likely the result of strong atmospheric
diffusion processes that operate similarly in both stars while their
similar patterns of C, N, O, and Ne abundances might provide clues to
their as yet unclear evolutionary history. Finally, we find that the
periods of the pulsation modes in Feige 46 are stable to better than
dP/dt~=10-8s/s. This is is not compatible with dP/dt predicted for
pulsations driven by the epsilon-mechanism and excited by helium-shell
flashes in a star which is evolving, for example, onto the extended
horizontal branch.
Description:
Stacked UVES spectra used in our analysis of LSIV -14 116 and Feige
46.
As described in the paper, two UVES spectra were stacked for Feige 46,
while a large number of short exposures were stacked for LSIV-14 116.
Both stacked spectra are corrected for the respective radial velocity.
The spectrum of LSIV-14 116 was additionally normalised to match the
continuum of the final synthetic spectrum and telluric lines were
removed. Both UVES spectra should not be used to determine atmospheric
parameters from broad (H/He) lines since they are not well normalised.
Objects:
---------------------------------------------------------
RA (2000) DE Designation(s)
---------------------------------------------------------
11 37 26.37 +14 10 14.1 Feige 46 = NSV 18813
20 57 38.87 -14 25 44.0 LSIV -14 116 = V* V366 Aqr
---------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 82 2 List of fits spectra
fits/* . 2 Individual fits spectra
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 h RAh Right Ascension (J2000)
4- 5 I2 min RAm Right Ascension (J2000)
7- 11 F5.2 s RAs Right Ascension (J2000)
12 A1 --- DE- Declination sign (J2000)
13- 14 I2 deg DEd Declination (J2000)
16- 17 I2 arcmin DEm Declination (J2000)
19- 22 F4.1 arcsec DEs Declination (J2000)
24- 29 I6 --- Nx Number of pixels along X-axis
31- 34 I4 Kibyte size Size of FITS file
36- 54 A19 --- FileName Name of FITS file, in subdirectory fits
56- 82 A27 --- Title Title of the FITS file
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Acknowledgements:
Matti Dorsch, matti.dorsch(at)fau.de
(End) Patricia Vannier [CDS] 14-Sep-2020