J/A+A/696/A123 lambda Boo stars in binary systems spectra (Alacoria+, 2025)
Searching for lambda Boo stars in binary systems.
Alacoria J., Saffe C., Collado A., Alejo A., Calvo D., Miquelarena P.,
Gonzalez E., Flores M., Jaque Arancibia M., Gunella F.
<Astron. Astrophys. 696, A123 (2025)>
=2025A&A...696A.123A 2025A&A...696A.123A (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Stars, peculiar ; Abundances ;
Spectra, optical
Keywords: stars: abundances - binaries: general - stars: chemically peculiar
Abstract:
The origin of λ Boo stars is currently unknown. Very few of
them are known as members of multiple systems, which could provide
benchmark laboratories to study their origin.
Our goal is to find new candidate λ Boo stars that belong to
binary systems. Then, a detailed abundance determination of some
candidates could confirm their true λ Boo nature, while the
composition of any late-type companions could be used as a proxy for
the initial composition of the λ Boo stars.
We cross-matched a homogeneous list of candidate λ Boo stars
with a recent Gaia eDR3 catalog of resolved binaries. Then we carried
out a detailed abundance determination via spectral synthesis of three
of these systems that host a candidate λ Boo star and a
late-type companion: HD 98069 + UCAC4 431-054639;
HD 87304 + CD-33 6615B; HD 153747 + TYC 7869-2003-1. The stellar
parameters were estimated by fitting the observed spectral energy
distributions (SEDs) with a grid of model atmospheres using the online
tool VOSA, together with Gaia eDR3 parallaxes and the PARAM 1.3
interface. Then the abundances were determined iteratively for 31
different species by fitting synthetic spectra using the SYNTHE
program together with local thermodynamic equilibrium (LTE) ATLAS12
model atmospheres. Specific opacities were calculated for each star,
depending on its arbitrary composition and microturbulence velocity,
vmicro, through the opacity sampling (OS) method. The abundances of
the light elements C and O were corrected by non-LTE effects. The
complete chemical patterns of the stars were then compared to those of
the λ Boo stars.
We obtained a group of 19 newly identified binary systems that contain
a candidate λ Boo star, allowing us to approximately double the
number of λ Boo stars currently known in multiple systems. This
important group could be used in further studies of λ Boo
stars. For the first time we performed a detailed abundance analysis
of three of these binary systems that include a candidate λ Boo
star and a late-type companion. We confirmed the true λ Boo
nature of the three early-type stars (HD 87304, HD 98069, and
HD 153747), and obtained mostly a solar-like composition for their
late-type components. Adopting as a proxy the late-type stars, we
showed that the three λ Boo stars were initially born with a
solar-like composition. This is an important constraint for any
scenario trying to explain the origin of λ Boo stars. The
present work provides three numerical examples of possible starting
and ending compositions to test formation models of λ Boo
stars. In addition, the solar-like composition of the late-type stars
supports the idea that λ Boo stars are Population I objects;
however, we caution that other explanations are also possible.
We performed, for the first time, a detailed abundance analysis of
binary systems including a λ Boo star and a late-type
companion. We obtained a solid indication that λ Boo stars were
born from a solar-like composition and established an important
constraint to test the formation models of λ Boo stars.
Description:
We performed a detailed abundance analysis of three binary systems
which include a candidate lambda Boo star and a late-type companion.
We confirmed the true lambda Boo nature of the three early-type stars
(HD 87304, HD 98069 and HD 153747), and obtained mostly a solar-like
composition for their late-type components. We showed that the lambda
Boo stars were initially born with a solar-like composition. Also, the
solar-like composition of the late-type stars supports the idea that
lambda Boo stars are Population I objects, however, we caution that
other explanations are also possible.
Reduced spectra (FITS files) for the stars (HD 87304, HD 98069,
HD 153747, CD -33 6615B, TYC7 869-2003-1 and UCAC 4431-054639)
in this work.
Objects:
----------------------------------------------------------------------
RA (2000) DE Designation(s)
----------------------------------------------------------------------
17 02 53.82 -38 27 36.8 HD 153747 = V* V922 Sco
10 03 23.45 -33 41 02.5 HD 87304 = CD-33 6615
11 16 44.62 -03 56 34.5 HD 98069 = BD-03 3086
10 03 23.07 -33 40 57.4 CD-33 6615B = TIC 29632798
17 02 38.73 -38 23 07.2 TYC 7869-2003-1 = 2MASS J17023873-3823073
11 16 48.06 -03 56 54.3 UCAC 4431-054639 = EPIC 201206607
----------------------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 120 6 List of spectra
fits/* . 6 Individual fits spectra
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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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- 40 A10 "datime" Obs.date Observation date
42- 48 F7.2 0.1nm blambda Lower value of wavelength interval
50- 57 F8.2 0.1nm Blambda Upper value of wavelength interval
59- 67 F9.7 0.1nm dlambda Wavelength resolution
69- 71 I3 Kibyte size Size of FITS file
73- 94 A22 --- FileName Name of FITS file, in subdirectory fits
96-120 A25 --- Title Title of the FITS file
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Acknowledgements:
Carlos Saffe, saffe.carlos(at)gmail.com
(End) Patricia Vannier [CDS] 17-Mar-2025