J/A+A/563/A13 Horizontal branch stars in M22 (Gratton+, 2014)
The Na-O anticorrelation in horizontal branch stars. IV. M22.
Gratton R.G., Lucatello S., Sollima A., Carretta E., Bragaglia A.,
Momany Y., D'Orazi V., Cassisi S., Salaris M.
<Astron. Astrophys. 563, A13 (2014)>
=2014A&A...563A..13G 2014A&A...563A..13G
ADC_Keywords: Galaxies, nearby ; Clusters, globular ; Abundances ;
Stars, horizontal branch
Keywords: stars: abundances - stars: evolution - stars: Population II -
globular clusters: general - globular clusters: individual: M22
Abstract:
We obtained high-resolution spectra for 94 candidate stars belonging
to the HB of M 22 with FLAMES. Previous works have indicated that this
cluster has split subgiant (SGB) and red giant branches (RGB) and
hosts two different stellar populations, differing in overall metal
abundance and both exhibiting a Na-O anti-correlation. The HB stars we
observed span a restricted temperature range (7800<Teff<11000K),
where about 60% of the HB stars of M 22 are. Within our sample, we can
distinguish three groups of stars segregated (though contiguous) in
colours: Group 1 (49 stars) is metal-poor, N-normal, Na-poor and
O-rich: our abundances for this (cooler) group match very well those
determined for the primordial group of RGB stars (a third of the
total) from previous studies. Group 2 (23 stars) is still metal-poor,
but it is N- and Na-rich, though only very mildly depleted in O. We
can identify this intermediate group as the progeny of the metal-poor
RGB stars that occupy an intermediate location along the Na-O
anti-correlation and include about 10% of the RGB stars. The third
group (20 stars) is metal-rich, Na-rich, and O-rich. This hotter group
likely corresponds to the most O-rich component of the previously
found metal-rich RGB population (a quarter of the total). We did not
observe any severely O-depleted stars and we think that the progeny of
these stars falls on the hotter part of the HB. Furthermore, we found
that the metal-rich population is also over-abundant in Sr, in
agreement with results for corresponding RGB and SGB stars. However,
we do not find any significant variation in the ratio between the sum
of N and O abundances to Fe. We do not have C abundances for our
stars. There is some evidence of an enhancement of He content for
Groups 2 and 3 stars (Y=0.338±0.014±0.05); the error bar due
to systematics is large, but a consistent analysis of data for several
GCs confirms that stars in these groups within M22 are likely
overabundant in He. We conclude that on the whole, our results agree
with the proposition that chemical composition drives the location of
stars along the HB of a GC. Furthermore, we found a number of fast
rotators. They are concentrated in a restricted temperature range
along the HB of M22. Fast rotating stars might be slightly less
massive and bluer than slowly rotating ones, but other interpretations
are possible.
Description:
Tables with basic data and abundances for 92 HB stars in M22.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 102 92 Photometric data
table4.dat 84 92 S/N, radial and rotational velocities
table5.dat 59 92 Atmospheric parameters
table6.dat 99 92 Abundances for individual stars
--------------------------------------------------------------------------------
See also:
J/ApJ/420/612 : Proper motions + radial velocities in M22 (Peterson+ 1994)
J/PASP/107/32 : uvby-hk photometry in M22 (Anthony-Twarog+ 1995)
J/A+A/373/899 : New variables in M22 globular cluster (Kaluzny+, 2001)
J/MNRAS/349/1278 : BVI photometry of M22 (Monaco+, 2004)
J/ApJ/742/37 : Abundances of six RGB stars in M22 (Roederer+, 2011)
J/A+A/541/A15 : Abundances of M22 subgiants (Marino+, 2012)
J/A+A/559/A101 : NGC6656 spectroscopy of 71 blue HB stars (Salgado+, 2013)
J/A+A/534/A123 : Horizontal branch stars in NGC 2808 (Gratton+, 2011)
J/A+A/539/A19 : Horizontal branch stars in NGC 1851 (Gratton+, 2012)
J/A+A/549/A41 : Horizontal branch stars in 47 Tuc and M5 (Gratton+, 2013)
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Star [1/129] Star designation
5- 6 I2 h RAh Right ascension (J2000.0)
8- 9 I2 min RAm Right ascension (J2000.0)
11- 16 F6.3 s RAs Right ascension (J2000.0)
18 A1 --- DE- Declination sign (J2000.0)
19- 20 I2 deg DEd Declination (J2000.0)
22- 23 I2 arcmin DEm Declination (J2000.0)
25- 29 F5.2 arcsec DEs Declination (J2000.0)
31- 36 F6.3 mag Vmag V magnitude
38- 42 F5.3 mag e_Vmag rms uncertainty on Vmag
44- 49 F6.3 mag Bmag B magnitude
51- 55 F5.3 mag e_Bmag rms uncertainty on Bmag
57- 62 F6.3 mag Imag I magnitude
64- 68 F5.3 mag e_Imag rms uncertainty on Imag
70- 75 F6.3 mag Kmag ? 2MASS Ks magnitude
77- 82 F6.3 mag ymag ? Stromgren y magnitude
84- 89 F6.3 mag bmag ? Stromgren b magnitude
91- 96 F6.3 mag vmag ? Stromgren v magnitude
98-102 F5.3 mag E(B-V) Interstellar redenning
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Star [1/129] Star designation
4- 6 I3 --- S/N3 ? S/N with HR03 set up
7- 10 I4 --- S/N12 ? S/N with HR12 set up
11- 14 I4 --- S/N19 ? S/N with HR19 set up
15- 22 F8.1 km/s RV03 ? Radial velocity with HR03 set up
23- 30 F8.1 km/s RV12 ? Radial velocity with HR12 set up
31- 38 F8.1 km/s RV19 Radial velocity with HR19 set up
39- 46 F8.1 km/s Average radial velocity
47- 51 F5.1 km/s e_ ? r.m.s. of radial velocities
52- 57 F6.1 km/s FWHM3 ? FWHM with HR03 set up
58- 63 F6.1 km/s FWHM12 ? FWHM with HR12 set up
64- 69 F6.1 km/s FWHM19 ? FWHM with HR19 set up
70- 75 F6.1 km/s Average FWHM of spectral lines
76- 80 F5.1 km/s e_ ? r.m.s. of FWHM
82 A1 --- l_vsini [<] Limit flag on vsini
83- 84 I2 km/s vsini [5/50] Rotational velocity
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Star [1/129] Star designation
4- 9 I6 K Te(B-V) Effective temperature from B-V
10- 15 I6 K Te(V-I) Effective temperature from V-I
16- 21 I6 K Te(b-y) ? Effective temperature from b-y
22- 27 I6 K Te(v-y) ? Effective temperature from v-y
28- 33 I6 K Te(V-K) ? Effective temperature from V-K
34- 39 I6 K Te(phot) Effective temperature from phot
40- 43 I4 K e_Te Error on effective temperature
44- 49 I6 K Te(Hd) ? Effective temperature from Hδ
50- 54 F5.2 [cm/s2] logg log surface gravity
55- 59 F5.2 km/s vt Microturbulence velocity
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Star [1/129] Star designation
4- 9 F6.2 --- YNLTE [0.2/0.5]? NLTE He abundance
10- 16 F7.2 --- e_YNLTE [0.0/0.1]? error on YNLTE
17- 24 F8.2 [Sun] [Fe/H]I ? Abundance Fe/HI
25- 32 F8.2 [Sun] [Fe/H]II ? Abundance Fe/HII
33- 40 F8.2 [Sun] [Fe/H] ? Mean Fe/H abundance
41- 47 F7.2 [Sun] [N/Fe] ? Abundance N/Fe
48- 54 F7.2 [Sun] [O/Fe] ? Abundance O/Fe
55- 62 F8.2 [Sun] [Na/Fe] Abundance Na/Fe
63- 69 F7.2 [Sun] [Mg/Fe]I ? Abundance Mg/FeI
70- 75 F6.2 [Sun] [Mg/Fe]II ? Abundance Mg/FeII
76- 82 F7.2 [Sun] [Si/Fe] ? Abundance Si/FeII
83- 89 F7.2 [Sun] [Ti/Fe] ? Abundance Ti/FeII
90- 97 F8.2 [Sun] [Sr/Fe] ? Abundance Sr/FeII
99 A1 --- Gr [ABC] Group designation (see section 4)
--------------------------------------------------------------------------------
Acknowledgements:
Raffaele Gratton, raffaele.gratton(at)oapd.inaf.it
References:
Gratton et al., Paper I 2011A&A...534A.123G 2011A&A...534A.123G, Cat. J/A+A/534/A123
Gratton et al., Paper II 2012A&A...539A..19G 2012A&A...539A..19G, Cat. J/A+A/539/A19
Gratton et al., Paper III 2013A&A...549A..41G 2013A&A...549A..41G, Cat. J/A+A/549/A41
(End) Patricia Vannier [CDS] 28-Jan-2014