2023A&A...671A..21J


Query : 2023A&A...671A..21J

2023A&A...671A..21J - Astronomy and Astrophysics, volume 671A, 21 (2023/3-1)

Cannibals in the thick disk II. Radial-velocity monitoring of the young α-rich stars.

JOFRE P., JORISSEN A., AGUILERA-GOMEZ C., VAN ECK S., TAYAR J., PINSONNEAULT M., ZINN J., GORIELY S. and VAN WINCKEL H.

Abstract (from CDS):

Context. Determining ages of stars for reconstructing the history of the Milky Way remains one of the most difficult tasks in astrophysics. This involves knowing when it is possible to relate the stellar mass with its age and when it is not. The young α-rich (YAR) stars present such a case in which we are still not sure about their ages because they are relatively massive, implying young ages, but their abundances are α-enhanced, which implies old ages.
Aims. We report the results from new observations from a long-term radial-velocity-monitoring campaign complemented with high-resolution spectroscopy, as well as new astrometry and seismology of a sample of 41 red giants from the third version of APOKASC, which includes YAR stars. The aim is to better characterize the YAR stars in terms of binarity, mass, abundance trends, and kinematic properties.
Methods. The radial velocities of HERMES, APOGEE, and Gaia were combined to determine the binary fraction among YAR stars. In combination with their mass estimate, evolutionary status, chemical composition, and kinematic properties, it allowed us to better constrain the nature of these objects.
Results. We found that stars with M < 1 M were all single, whereas stars with M > 1 M could be either single or binary. This is in agreement with theoretical predictions of population synthesis models. Studying their [C/N], [C/Fe], and [N/Fe], trends with mass, it became clear that many YAR stars do not follow the APOKASC stars, favoring the scenario that most of them are the product of mass transfer. Our sample further includes two likely undermassive stars, that is to say of such as low mass that they cannot have reached the red clump within the age of the Universe, unless their low mass is the signature of mass loss in previous evolutionary phases. These stars do not show signatures of currently being binaries. Both YAR and undermassive stars might show some anomalous APOGEE abundances for the elements N, Na, P, K, and Cr; although, higher-resolution optical spectroscopy might be needed to confirm these findings.
Conclusions. Considering the significant fraction of stars that are formed in pairs and the variety of ways that makes mass transfer possible, the diversity in properties in terms of binarity, and chemistry of the YAR and undermassive stars studied here implies that most of these objects are likely not young.

Abstract Copyright: © The Authors 2023

Journal keyword(s): stars: abundances - stars: atmospheres - binaries: close - stars: evolution - Galaxy: stellar content - Galaxy: evolution

VizieR on-line data: <Available at CDS (J/A+A/671/A21): table1.dat tableb3.dat>

Status at CDS : Tables of objects will be appraised for possible ingestion in SIMBAD.

Simbad objects: 44

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Number of rows : 44
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 NGC 104 GlC 00 24 05.359 -72 04 53.20     4.09     ~ 3922 0
2 * alf Boo RG* 14 15 39.67207 +19 10 56.6730 2.46 1.18 -0.05 -1.03 -1.68 K1.5IIIFe-0.5 2322 1
3 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 14463 0
4 2MASS J18521894+4116496 RG* 18 52 18.9459855432 +41 16 49.521283248           ~ 22 0
5 2MASS J18540578+4520474 RG* 18 54 05.7760158024 +45 20 47.469332688           K5II 26 0
6 2MASS J18553092+4042447 HB* 18 55 30.9209322984 +40 42 44.671799880           ~ 26 0
7 2MASS J18592488+4556131 HB* 18 59 24.8818056792 +45 56 13.133730552           G9IIIb 18 0
8 TYC 3132-924-1 HB* 19 02 34.8344204976 +44 44 08.771438148   11.93 10.87     ~ 25 0
9 TYC 3120-1371-1 HB* 19 02 43.0466794632 +38 54 59.337624384   10.71 9.56     ~ 32 0
10 2MASS J19025410+4957320 RG* 19 02 54.1148092968 +49 57 32.091226020           ~ 16 0
11 2MASS J19031115+4753540 RG* 19 03 11.1576896280 +47 53 54.074887332           K0II 23 0
12 2MASS J19032243+4547495 HB* 19 03 22.4332337952 +45 47 49.515065124           K0III 29 0
13 TYC 3120-641-1 RG* 19 05 04.9314767064 +38 39 00.546345720   13.29 11.30     ~ 21 0
14 2MASS J19052572+4437508 RG* 19 05 25.7224413624 +44 37 50.926532700           ~ 23 0
15 2MASS J19052620+4921373 HB* 19 05 26.2030695168 +49 21 37.307260728           K1III 22 0
16 TYC 3120-1202-1 HB* 19 05 54.6516306192 +37 35 05.309077812   12.96 12.38     G8IV-V 26 0
17 2MASS J19070280+4530112 RG* 19 07 02.8058609184 +45 30 11.218149648           K1IV 25 0
18 TYC 3124-640-1 RG* 19 08 17.1693797784 +39 24 58.374039168   13.15 11.89     K1IV 43 0
19 TYC 3132-1453-1 RG* 19 08 31.5261680304 +43 21 54.257096052   12.77 12.13     G9IIIb 30 0
20 UCAC4 684-065062 RG* 19 08 36.1588752720 +46 41 21.253098480   13.228 12.216 12.051   ~ 40 0
21 TYC 3132-1585-1 HB* 19 08 43.5537948912 +43 17 58.592509944   13.14 11.68     ~ 29 0
22 TYC 3542-868-1 RG* 19 09 38.0164418112 +46 35 25.278158436   13.42 11.94     ~ 27 0
23 TYC 3550-530-1 HB* 19 09 40.0087056648 +49 13 39.329796972   12.98 12.03     G8IV 31 0
24 TYC 3121-1613-1 HB* 19 10 11.5398709320 +39 14 58.306278192   12.85 12.16     ~ 31 0
25 TYC 3546-1967-1 HB* 19 10 21.3462763128 +47 43 19.394938092   11.78 11.04     ~ 30 0
26 2MASS J19151828+4736422 HB* 19 15 18.2841494352 +47 36 42.181833456           K0III 24 0
27 TYC 3543-646-1 HB* 19 19 33.5627319888 +46 48 25.825215420   12.88 11.51     ~ 20 0
28 TYC 3543-2244-1 HB* 19 19 45.7859280000 +46 19 27.540401808   12.32 11.90     G5IV 23 0
29 Cl* NGC 6791 MJP 2 HB* 19 21 17.1375347448 +37 48 03.942201528   14.172 12.6863     ~ 26 0
30 TYC 2666-241-1 RG* 19 25 49.8550150032 +37 01 02.845959816   13.83 12.57     ~ 24 0
31 TYC 3556-813-1 RG* 19 31 36.7121134032 +45 32 50.046044604   12.64 12.23     ~ 27 0
32 2MASS J19355053+5030152 RG* 19 35 50.5374404328 +50 30 15.274190340           K1.5III 22 0
33 2MASS J19370398+3954132 HB* 19 37 03.9759583464 +39 54 13.184305776           ~ 21 0
34 TYC 3135-468-1 RG* 19 37 45.7037223720 +38 35 35.637269388   12.13 11.39     K2IIIb 39 0
35 2MASS J19382435+3847454 RG* 19 38 24.3519329784 +38 47 45.336253992           ~ 22 0
36 TYC 3564-3001-1 HB* 19 41 12.8057337384 +50 09 27.971511300   13.79 12.00     ~ 26 0
37 TYC 3556-3195-1 RG* 19 41 14.2463602752 +46 01 48.146898612   13.00 11.45     K1.5III 29 0
38 TYC 3136-677-1 RG* 19 41 57.5245481304 +38 45 04.416110748   12.67 12.40     ~ 18 0
39 TYC 3565-661-1 HB* 19 45 52.9229247240 +50 02 30.462826812   12.61 11.33     ~ 30 0
40 2MASS J19460251+4913014 HB* 19 46 02.5171839672 +49 13 01.423275096           ~ 23 0
41 2MASS J19464438+5002378 RG* 19 46 44.3946698496 +50 02 37.754174004           K0 20 0
42 TYC 3557-1587-1 HB* 19 51 33.4475846040 +46 17 49.804403316   12.64 11.39     ~ 26 0
43 BD+47 2947 HB* 19 53 45.4190003904 +47 42 44.150180040   11.17 10.36     G5V: 21 0
44 TYC 3562-1082-1 HB* 19 55 12.3212336664 +48 17 34.408074948   12.00 11.04     ~ 28 0

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