J/A+A/693/A98 The lithium-rich giant stars puzzle (de la Reza, 2025)
On the lithium-rich giant stars puzzle:
New observational trends for a general mass loss scenario.
de la Reza R.
<Astron. Astrophys. 693, A98 (2025)>
=2025A&A...693A..98D 2025A&A...693A..98D (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Stars, peculiar ; Photometry, infrared
Keywords: stars: chemically peculiar - stars: evolution - stars: interiors -
stars: mass loss - stars: winds - outflows
Abstract:
The existence of one percent of lithium-rich giant stars
among normal, lithium-poor giant stars continues to be poorly
explained. By merging two catalogues - one containing 10535
lithium-rich giant stars with lithium abundances ranging from 1.5 to
4.9dex, and the other detecting infrared sources - we have found 421
clump giant stars and 196 first-ascending giant stars with infrared
excesses indicating stellar mass losses. The clump stars are the most
lithium-rich. Approximately 5.8 percent of these stars appear to
episodically lose mass in periods of approximately 104 years or
less, while the remaining stars have ceased their mass loss and have
maintained their lithium for nearly 107 years. We propose a scenario
in which all giant stars with masses below two solar masses undergo
prompt lithium enrichment with mass ejection episodes. We suggest that
the mass loss results from internal angular momentum transport. It is
possible that a transitory instability, perhaps of magnetic origin,
rapidly transports the nuclear material responsible for the lithium
enrichment to the stellar surface and triggers shell ejections.
Additionally, the strong mass loss in some lithium-rich stars during
their evolution activates their chromospheres, as observed in
ultraviolet spectra. Furthermore, intense episodical mass losses in
these stages lead to the observable formation of complex organic and
inorganic particles, as detected in near-infrared spectra. In contrast
to first-ascending giant stars, helium flashes during the clump can
contribute to additional lithium enrichment alongside the
aforementioned process. The combination of these two lithium sources
may explain the much higher observed lithium abundances in clump stars
as well as their observed infrared excesses. If our scenario, based on
a universal and rapid lithium enrichment episode process, is correct,
it could explain the rarity of lithium-rich giant stars.
Description:
Stellar parameters of RC and RGB giant stars presenting IR excesses.
These are the stellar identification, right ascension (RA),
declination (DEC), effective temperature (Teff), surface gravity
(logg), metallicity ([Fe/H]), lithium abundance (A(Li)), IR excess
(IR), the WISE confusion flag, and the WISE photometric flag. The
notes indicate the classification of IR sources based on the
photometric flag (see text) and Class the evolutionary stage RC or
RGB.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 84 617 Stellar parameters of RC and RGB giant stars
presenting IR excesses
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See also:
V/156 : LAMOST DR7 catalogs (Luo+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Name LAMOST identification (JHHMMSS.ss+DDMMSS.s)
21- 22 I2 h RAh Right ascension (J2000)
24- 25 I2 min RAm Right ascension (J2000)
27- 31 F5.2 s RAs Right ascension (J2000)
33 A1 --- DE- Declination sign (J2000)
34- 35 I2 deg DEd Declination (J2000)
37- 38 I2 arcmin DEm Declination (J2000)
40- 43 F4.1 arcsec DEs Declination (J2000)
45- 48 I4 K Teff Effective temperature
50- 52 F3.1 [cm/s2] logg logarithm of surface gravity
54- 57 F4.1 [Sun] [Fe/H] Metallicity
59- 61 F3.1 [-] A(Li) Lithium Abundance
63- 68 F6.4 --- IR IR excess
70- 73 A4 --- CCflag WISE confusion flag (1)
75- 78 A4 --- Phq WISE photometric flag (2)
80 I1 --- Note [1/3] IR sources (3)
82- 84 A3 --- Stage Evolutionary stage (4)
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Note (1): WISE CC-flag is the confusion flag set to 0000 corresponding to the
four WISE magnitude colors W1, W2, W3 and W4 (written 00 in the table).
For a color different than 0 the WISE manual must be consulted.
Note (2): Ph-qual is the photometric WISE quality flag set to AAAA.
Note (3): the last Ph-qual symbol can have values as follows:
1 = for snr larger than 10
2 = for snr smaller than 10
3 = for snr smaller than 3
Note (4): Taking into account the evolutionary stage as follows:
RC = red clump giant stars
RGB = ascending giant stars
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Acknowledgements:
Ramiro de la Reza, ramirodelareza (at) yahoo.com
(End) Patricia Vannier [CDS] 26-Nov-2024