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J/ApJ/784/19   Orphan stream high-resolution spectroscopic study  (Casey+, 2014)

Hunting the parent of the Orphan stream. II. The first high-resolution spectroscopic study. Casey A.R., Keller S.C., Da Costa G., Frebel A., Maunder E. <Astrophys. J., 784, 19 (2014)> =2014ApJ...784...19C (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, halo ; Equivalent widths ; Abundances Keywords: Galaxy: halo - Galaxy: structure - stars: abundances - stars: late-type - stars: Population II Abstract: We present the first high-resolution spectroscopic study on the Orphan stream for five stream candidates, observed with the Magellan Inamori Kyocera Echelle spectrograph on the Magellan Clay telescope. The targets were selected from the low-resolution catalog of Casey et al. (2013ApJ...764...39C): three high-probability members, one medium, and one low-probability stream candidate were observed. Our analysis indicates that the low- and medium-probability targets are metal-rich field stars. The remaining three high-probability targets range over ∼1 dex in metallicity, and are chemically distinct compared to the other two targets and all standard stars: low [α/Fe] abundance ratios are observed, and lower limits are ascertained for [Ba/Y], which sit well above the Milky Way trend. These chemical signatures demonstrate that the undiscovered parent system is unequivocally a dwarf spheroidal galaxy, consistent with dynamical constraints inferred from the stream width and arc. As such, we firmly exclude the proposed association between NGC 2419 and the Orphan stream. A wide range in metallicities adds to the similarities between the Orphan stream and Segue 1, although the low [α/Fe] abundance ratios in the Orphan stream are in tension with the high [α/Fe] values observed in Segue 1. Open questions remain before Segue 1 could possibly be claimed as the "parent" of the Orphan stream. The parent system could well remain undiscovered in the southern sky. Description: High-resolution spectra for five Orphan stream candidates and seven well-studied standard stars have been obtained with the Magellan Inamori Kyocera Echelle spectrograph (Bernstein et al. 2003SPIE.4841.1694B) on the Magellan Clay telescope. These objects were observed in 2011 March using a 1" wide slit in mean seeing of 0.9". This slit configuration provides continuous spectral coverage from 333 nm to 915 nm, with a spectral resolution of R=25000 in the blue arm and R=28000 in the red arm. A minimum of 10 exposures of each calibration type (biases, flat fields, and diffuse flats) were observed in the afternoon of each day, with additional flat-field and Th-Ar arc lamp exposures performed throughout the night to ensure an accurate wavelength calibration. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 87 12 Observations table2.dat 103 499 Equivalent Widths for Standard and Program Stars table6.dat 48 280 Abundance Uncertainties Due to Stellar Parameters
See also: J/AJ/120/1841 : Abundances and Kinematics of Halo and Disk Stars (Fulbright 2000) J/ApJ/698/865 : Halo streams in the SDSS-DR7 (Klement+, 2009) J/ApJ/711/573 : Detailed abundances in a halo stellar stream (Roederer+, 2010) J/ApJ/776/26 : RRab stars in the Orphan stream distances (Sesar+, 2013) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 8 A8 --- Name Star identifier (HD NNNNNN, OSS-NN) 10 A1 --- n_Name [LMH] Note on Name (1) 12- 13 I2 h RAh Hour of Right Ascension (J2000) 15- 16 I2 min RAm Minute of Right Ascension (J2000) 18- 21 F4.1 s RAs Second of Right Ascension (J2000) 23 A1 --- DE- Sign of the Declination (J2000) 24- 25 I2 deg DEd Degree of Declination (J2000) 27- 28 I2 arcmin DEm Arcminute of Declination (J2000) 30- 33 F4.1 arcsec DEs Arcsecond of Declination (J2000) 35- 39 F5.2 mag Vmag [5.86/17.82] V-band magnitude (2) 41- 50 A10 "date" Date UT Date of observation 52- 59 A8 "h:m:s" Time UT Time of observation 61- 64 F4.2 --- Airmass [1.01/2.0] Airmass 66- 72 A7 s Exp Exposure time 74- 76 I3 --- S/N [31/335] Signal-to-noise ratio (3) 79- 83 F5.1 km/s HV [-38.2/297.8] Heliocentric velocity 85- 87 F3.1 km/s e_HV [0.9/1.3] Heliocentric velocity error
Note (1): Probability of membership (low, medium, high) listed for the Orphan stream candidates as defined by Casey et al. (2013ApJ...764...39C). Note (2): V-band magnitudes for the Orphan stream targets are estimated to be equivalent to g-band magnitudes. Note (3): S/N measured per pixel (∼0.09 Å/pixel) at 600 nm for each target.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 8 F8.3 nm Wave Wavelength 10- 13 F4.1 --- Species [8.0/63.1] Species identifier 15- 18 F4.2 eV chi Excitation potential 20- 26 F7.3 [-] log(gf) Log of the oscillator strength 28- 33 F6.2 10-13m HD41667 ? HD 41667 equivalent width (1) 35- 40 F6.2 10-13m HD44007 ? HD 44007 equivalent width (1) 42- 47 F6.2 10-13m HD76932 ? HD 76932 equivalent width (1) 49- 54 F6.2 10-13m HD136316 ? HD 136316 equivalent width (1) 56- 61 F6.2 10-13m HD141531 ? HD 141531 equivalent width (1) 63- 68 F6.2 10-13m HD142948 ? HD 142948 equivalent width (1) 70- 75 F6.2 10-13m OSS-3 ? OSS 3 equivalent width (1) 77- 82 F6.2 10-13m OSS-6 ? OSS 6 equivalent width (1) 84- 89 F6.2 10-13m OSS-8 ? OSS 8 equivalent width (1) 91- 96 F6.2 10-13m OSS-14 ? OSS 14 equivalent width (1) 98-103 F6.2 10-13m OSS-18 ? OSS 18 equivalent width (1)
Note (1): In units of milli-Angstroms.
Byte-by-byte Description of file: table6.dat
Bytes Format Units Label Explanations
1- 8 A8 --- Name Star identifier (HD NNNNNN, OSS-NN) 11- 15 A5 --- Species Species identifier 17- 21 F5.2 [-] DATeff Abundance uncertainty from Teff 23- 27 F5.2 [-] DAlogg Abundance uncertainty from log(g) 29- 33 F5.2 [-] DAvt Abundance uncertainty from microturbulence 35- 38 F4.2 [-] SEDrand Abundance random standard error about the mean 40- 43 F4.2 [-] e_[X/H] Total [X/H] abundance uncertainty 45- 48 F4.2 [-] e_[X/Fe] ? Total [X/Fe] abundance uncertainty
History: From electronic version of the journal References: Casey et al., Paper I, 2013ApJ...764...39C
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 27-Jun-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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