Download Abundance of Elements

NIR High Resolution Stellar
Spectroscopic Studies
Prospective Abundance Study on M dwarfs with IGRINS
Sang Gak Lee
(Seoul National University , Department of Physics and Astronomy, Astronomy
Program
Cosmic Abundance
a) the large abundances of H and He;
b) the deep “hole” corresponding to
Li/Be/B;
c) a series of peaks, particularly
prominent for the α nuclei, corresponding to
the products of stellar burning between mass
12 and mass ∼ 40;
d) a mass peak near Fe, A ∼ 56-60;
e) rare heavier elements, but with mass peaks
near A ∼ 130 and A ∼ 195.
Signitures of Nucleosynthesis
 A) 1H ~ 0.75
4He ~ 0.25

 B) 6Li ~ 7.75E-10
7Li ~ 1.13E -8 (BB)

9Be ~ 3.13E-10

10B ~ 5.22E-10

11B ~ 2.30E -9

 Li, Be, B :
 1. produced in the ISM when energetic cosmic-ray protons collide with elements like C, N.
&O
 2. synthesized by core-collapse SN, by the interactions of neutrinos in the carbon shells of
such stars
 3 fragile ~ T > 2.0E6 (6Li), 2.5E6 (7Li), 3.5E6 (9Be), 5.3E6 (10B) 5.0E6 (11B)
Signitures of Nucleosynthesis
 C) a-elements : C, N, O, Ne, Mg, & Si ; tightly bound, thermodynamically-favored






products of nuclear burning.
12C ∼ 3.87E-3
14N ∼ 0.94E-3
16O ∼ 8.55E-3
20Ne ∼ 1.34E-3
24Mg ∼ 0.58E-3
28Si ∼ 0.75E-3
 D) iron-peak elements :near Fe & Ni ; largest binding energy/nucleon
 E) the heavy elements, A > 100 :very rare, several abundance peaks ;each peak is actually a
double peak, with the two components splits by ~ 10 mass units.
  (n,g) reactions :
 produced in ordinary stars with relatively weak neutron sources = s-process,
 Under explosive conditions (SN or neutron star collision) = r-process
Cosmic Chemical Evolution
Are the Abundance Patterns of all stars
same ?
 Can we scale down or up the solar abundance pattern by using
metallicity ? NO!!
 What is the meaning of the different abundance pattern?
  Is star formation rate constant?
  Is the stellar luminosity function same all the time?
  Chemical Evolution of the Universe ?
  High Resolution Stellar Spectra (Large Telescopes) with
fundamental physical parameters, such as gf values for absorption
lines of elements
For Better Abundances, improvements in
last 30 years
 Telescope : factor of 3 light-collecting area
 Detectors : factor of 50 more efficient
 Computers : factor of 103 rapid
 Algorithms : factor of 100 faster
 Atomic and molecular data : 1-2 order of quality improved

 High-resol & high-S/N spectra for 105 stars (cf few stars 30 years
ago)
Abandunce errors
 Earlier scatter reflects uncertainties in observed data, fundamental parameters, &
standard mode atm.
 Now could be due to different attempts to handle convection, inhomogeneities, &
non-LTE
 Uncertainties in fundamental parameters (Teff, log g, [Fe/H] etc)  typical error
of 0.1 dex in abundance rel to H and rel to the solar abundances
 Errors in measurements : similar
 Error due to non-LTE in and LTE treatment or uncertainties in collision cross
sections : 0.1 -0.2 dex for early type main sequence and solar type stars
 Error due to inhomogeneities and 3-D convection : typically 0.1-0.2 dex for solar
types and 2 times larger or even more for certain elements for Pop II stars of similar
temperature
 In general strongly time-dependent lines imply larger errors
a-elements
 [X/Fe] : Si, Ca, C, O, Mg, Ti
Odd Z elements, Na & Al
 Na & Al
Fe-peak
Elements
 Co, Cr, Mn, Ni, Cu, Zn
K, Sc, V, N
 K, Sc, V, N
Neutron Capture Elements
 Eu & Ba
Late Dwarf Stars
Prospective Abundance Study on M
dwarfs with IGRINS
M dwarfs : Scientific Justification
 most numerous stars in the Galaxy
 lifetime on main sequence is longer than the age of universe
  the chemical evolution of the universe
 intrinsic faint brightness and the complex optical spectra
 brightness peaks around the near IR, IGRINS will be the best
instruments for chemical abundance study of M dwarfs
Pros
 They are cool to have peak intensity around near IR
 For abundance study, the continuum is better fitted in IR
than in visual to provide the more accurate abundances of
elements
 Their main sequence lifetime is long enough to give solid
information about the chemical evolution of the Galaxy, since
their surface abundances would represent the material they
were formed.
SUMMARY
 We examined the abundances of 15 elements for 52 G-type samples ( PHSs :
34 )
 [Mn/Fe] is high for PHSs
 The more Mn & Zn lines have to be added
 The synthetic spectrum with hyperfine structure
 [Sc/Fe] and [Ti/Fe] tend to increase for PHSs in [Fe/H] < 0
 Need more samples in [Fe/H] < 0
 [Ba/Fe] of single-planet system is higher than that of multi-planet system
 [Zn/Fe] of single-planet system is ~solar, higher scatter of [Zn /Fe] of multi-
planet system .
Sample of M dwarfs
 within 10 pc there are 246 M stars : RECONS(www.recons.org)
 Within 25 pc, 67 M dwarf systems are added (Riedel et al.,
2010, AJ, 140, 897)
H band
 H band
N. Ryde et al
H & K Band spectra
 H band : CO ( v=3), OH, Mg, Al , Si
 K band : CO(v=2), Na, Ca, Si, Al, Mg, Ti
H & K band
 arXiv:0707.2610v1, Cunha et al.
Fine Abundance Analysis
 Stellar atmospheric parameters :
 Teff, log g , [Fe/H], xt
I. Derive the stellar parameters of M dwarfs using the synthetic spectra in
the long wavelength region of the optical spectra (over 8000 Å), which
is relatively less contaminated by molecular lines as well as telluric lines.
Test the synthetic spectrum for K2 III type star : HD 110014
(강원석 & 이상각, 2011)
 Kurucz ATLAS9 model grid and SYNTHE code (by Fiorella Castelli)
 •Wavelength region : 8300 – 8850 Å - Ca I triplet (strong lines) and many Fe/Ti lines
 •Find the best fit using least-χ2 method - Using [Fe/H] = -1.0 model grids with vtur =
0.0 km/s (no turbulence )
Test the synthetic spectrum for K2 III type star
Target : HD 110014 ( observed with BOES at BOAO on
29 Apr 2011 ) :
 Wavelength : 8300 – 8850 Å
 Results : Teff = 4556 K, log g = 1.99 dex From fine analysis
(Fe I/Fe II lines) :Teff = 4410 K, log g = 2.24 dex (Kang, 2011)
Line data
 8300 – 8700 A
Log g : Wilson –Bappu
Relation
G, K, M type stars ( I, II, III, IV, V)
박선경, 이정은 , 이상각 & 강원석 2012
a SpT-Te relation
 not valid for Te<2800K & not valid for >M6.
the zTiO/CaH metallicity index
 The optical and near infrared spectra of
M dwarfs and subdwarfs are dominated
by molecular absorption bands of metal
oxides and hydrides, most prominently
bands of TiO and CaH (Bessel 1991).
The ratio between the strength of the
oxide and hydride bands has long been
known as a metallicity diagnostic (Bessel
1982).
 The current classification system of cool
(spectral subtypes K5-M6) and ultracool (subtypesM7-M9) low-mass stars
distinguishes three broad metallicity
classes:
 the dwarfs (K5- M9, or dK5-dM9), the
metal-poor subdwarfs (sdK5-sdM9),
and the very metal-poor extreme
subdwarfs (esdK5-esdM9).
Lepine et al 2007
Metallicity
4-classes
Lepine et al 2007
Synthetic spectra
 the NextGen model atmosphere grid of
Hauschildt, Allard, & Baron (1999).
 Synthetic spectra for cool stars were
retrieved from the website of the
PHOENIX project( http://www.hs.unihamburg.de/EN/For/ThA/phoenix)
 critical metallicity calibration has now been
initiated based on atmospheric modeling of
Fe lines using high resolution spectra of
bright (mostly early-type)M dwarfs and
subdwarfs (Woolf & Wallerstein 2005,
2006; Bean et al. 2006).
Teff, [Fe/H]
 Ratio : Ca II 8498, 8542 & 8622 / KI 7699
Conclusion
 Spectroscopic abundance analysis in the H & K band
( IGRINS) is reliable for determining the metallicity for M
dwarfs and for individual elements abundance
determinations.
 Elemental abundance study for a large sample of M dwarfs
covering lower as well as higher metallicities, will provide
important clues to the chemical evolution of the Galaxy.
감사합니다.
이상각