2015A&A...583A..49H


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.10CEST03:03:01

2015A&A...583A..49H - Astronomy and Astrophysics, volume 583A, 49-49 (2015/11-1)

The role of binaries in the enrichment of the early Galactic halo. I. r-process-enhanced metal-poor stars.

HANSEN T.T., ANDERSEN J., NORDSTROEM B., BEERS T.C., YOON J. and BUCHHAVE L.A.

Abstract (from CDS):

The detailed chemical composition of most metal-poor halo stars has been found to be highly uniform, but a minority of stars exhibit dramatic enhancements in their abundances of heavy neutron-capture elements and/or of carbon. The key question for Galactic chemical evolution models is whether these peculiarities reflect the composition of the natal clouds, or if they are due to later (post-birth) mass transfer of chemically processed material from a binary companion. If the former case applies, the observed excess of certain elements was implanted within selected clouds in the early ISM from a production site at interstellar distances. Our aim is to determine the frequency and orbital properties of binaries among these chemically peculiar stars. This information provides the basis for deciding whether local mass transfer from a binary companion is necessary and sufficient to explain their unusual compositions. This paper discusses our study of a sample of 17 moderately (r-I) and highly (r-II) r-process-element enhanced VMP and EMP stars. High-resolution, low signal-to-noise spectra of the stars were obtained at roughly monthly intervals over eight years with the FIES spectrograph at the Nordic Optical Telescope. From these spectra, radial velocities with an accuracy of ∼100m/s were determined by cross-correlation against an optimized template. Fourteen of the programme stars exhibit no significant radial-velocity variation over this temporal window, while three are binaries with orbits of typical eccentricity for their periods, resulting in a normal binary frequency of ∼18±6% for the sample. Our results confirm our preliminary conclusion from 2011, based on partial data, that the chemical peculiarity of the r-I and r-II stars is not caused by any putative binary companions. Instead, it was imprinted on the natal molecular clouds of these stars by an external, distant source. Models of the ISM in early galaxies should account for such mechanisms.

Abstract Copyright:

Journal keyword(s): stars: abundances - stars: chemically peculiar - binaries: spectroscopic - Galaxy: halo - ISM: structure

Simbad objects: 31

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Number of rows : 31

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 HD 20 Pe* 00 05 15.3243774125 -27 16 18.141386481   9.65 9.40 8.865 8.377 F2V 56 0
2 BPS CS 29497-0004 Pe* 00 28 06.9155330651 -26 03 04.268822971   14.76 14.07 13.583 13.116 ~ 42 0
3 HD 3765 PM* 00 40 49.2699101367 +40 11 13.819725965   8.30   6.8   K2V 234 0
4 BPS CS 22183-0031 Pe* 01 09 05.0899437519 -04 43 21.344131594   14.24 13.62 13.178 12.724 ~ 39 0
5 BPS CS 31082-0001 Pe* 01 29 31.1311330115 -16 00 45.496485322 12.527 12.427 11.642 11.189 10.713 CEMP 243 0
6 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 5669 1
7 HE 0432-0923 Pe* 04 34 25.6711776469 -09 16 50.513666136     15.165   14.140 ~ 12 0
8 HE 0442-1234 Pe* 04 44 51.7051525378 -12 28 45.536189519     12.914   11.672 ~ 13 0
9 HE 0524-2055 Pe* 05 27 04.4443497290 -20 52 42.097158461     14.013   12.937 ~ 10 0
10 HD 38230 PM* 05 46 01.8856610139 +37 17 04.737324425   8.19   6.8   K0V 140 0
11 HD 79210 Fl* 09 14 22.7754519714 +52 41 11.792840757   9.388   6.8   K7V 251 0
12 HE 1044-2509 Pe* 10 47 16.4778888479 -25 25 18.271783217   15.011 14.345 13.877 13.399 ~ 7 0
13 HE 1105+0027 Pe* 11 07 49.5058676910 +00 11 38.347372568   16.038 15.646 15.358 15.018 CEMP-s 23 0
14 HE 1127-1143 Pe* 11 29 50.6276751880 -12 00 12.580350655     15.885 15.434 15.002 ~ 11 0
15 HE 1219-0312 Pe* 12 21 34.1430157283 -03 28 39.635608057     15.940   15.043 ~ 31 0
16 HD 115444 Pe* 13 16 42.4591800169 +36 22 52.695481224   9.77 8.97 8.3 7.88 G9V 224 0
17 HD 115404 PM* 13 16 51.0517063595 +17 01 01.840304856   7.69 6.66     K2V 254 0
18 HD 122563 Pe* 14 02 31.8456299772 +09 41 09.942736952 7.47 7.10 6.19 5.37 4.79 G8:III:Fe-5 746 0
19 HD 122653 * 14 02 50.3188208822 +17 59 16.229439851 7.448 9.55 8.06 5.616   K0 12 0
20 HE 1430+0053 Pe* 14 33 16.5345011818 +00 40 48.884048356   14.280 13.663 13.252 12.813 ~ 14 0
21 HE 1523-0901 Pe* 15 26 01.0697794752 -09 11 38.882076152   12.37 11.50 10.476 9.863 CEMP 61 0
22 HD 151541 PM* 16 42 38.5768818637 +68 06 07.792148115   8.32   7.1   K1 111 0
23 HD 182488 PM* 19 23 34.0133626629 +33 13 19.074920892       5.8   K0V 244 1
24 HD 197076 PM* 20 40 45.1407864181 +19 56 07.928511642 7.14 7.06 6.44 5.95 5.61 G5V 220 0
25 BPS CS 22892-0052 Pe* 22 17 01.6558480594 -16 39 27.051900047   14.03 13.20 13.06 12.19 KIIvw 410 0
26 HE 2224+0143 Pe* 22 27 23.1215444901 +01 58 33.065892787   14.54 13.83 13.208 12.733 ~ 18 0
27 HE 2244-1503 Pe* 22 47 25.8322418837 -14 47 30.211664776     15.351   14.483 ~ 7 0
28 HD 221170 Pe* 23 29 28.8087923676 +30 25 57.847432750 9.43 8.74 7.66     G2IV 263 0
29 HE 2327-5642 Pe* 23 30 37.0896402813 -56 26 14.384633079   14.590 13.881 13.425 12.948 ~ 27 0
30 BPS CS 30315-0029 Pe* 23 34 26.6960736693 -26 42 14.004570680   14.56 13.64 13.092 12.518 ~ 15 0
31 LP 584-32 Pe* 23 57 18.9066877816 -00 52 47.436819958   16.366 15.636 15.141 14.673 ~ 26 0

    Equat.    Gal    SGal    Ecl

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2020.07.10-03:03:01

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