The Two Micron All Sky Survey (2MASS): Overview and Status

Skrutskie, M. F.; Schneider, S. E.; Stiening, R.; Strom, S. E.; Weinberg, Martin D.; Beichman, C.; Chester, T. J.; Cutri, R. M.; Lonsdale, C. J.; Elias, J. H.; Elston, R.; Capps, R. W.; Carpenter, J. Richard; Huchra, J. P.; Liebert, James; Monet, D. G.; Price, S. D.; Seitzer, Patrick

doi:10.1007/978-94-011-5784-1_3

Cited by 245 publications

(137 citation statements)

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“…At a distance of 7.9 kpc, this corresponds to a projected distance of ∼1.1 pc. In this context, we note that the Two Micron All Sky Survey point source catalogue (2MASS, Skrutskie et al 1997) does not reveal any concentration of sources around WR 20a that could hint towards a heavily obscured group of (proto-) stars.…”

Section: Wr 20a As a Member Of Westerlundmentioning

confidence: 81%

The spectrum of the very massive binary system WR 20a (WN6ha + WN6ha): Fundamental parameters and wind interactions

Rauw¹,

Crowther

Becker³

et al. 2005

A&A

137

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Abstract. We analyse the optical spectrum of the very massive binary system WR 20a (WN6ha + WN6ha). The most prominent emission lines, Hα and He  λ 4686, display strong phase-locked profile variability. From the variations of their equivalent widths and from a tomographic analysis, we find that part of the line emission probably arises in a wind interaction region between the stars. Our analysis of the optical spectrum of WR 20a indicates a reddening of A V 6.0 mag and a distance of ∼7.9 kpc, suggesting that the star actually belongs to the open cluster Westerlund 2. The location of the system at ∼1.1 pc from the cluster core could indicate that WR 20a was gently ejected from the core via dynamical interactions. Using a non-LTE model atmosphere code, we derive the fundamental parameters of each component: T eff = 43 000 ± 2000 K, log L bol /L 6.0,Ṁ = 8.5 × 10 −6 M yr −1 (assuming a clumped wind with a volume filling factor f = 0.1). Nitrogen is enhanced in the atmospheres of the components of WR 20a, while carbon is definitely depleted. Finally, the position of the binary components in the Hertzsprung-Russell diagram suggests that they are core hydrogen burning stars in a pre-LBV stage and their current atmospheric chemical composition probably results from rotational mixing that might be enhanced in a close binary compared to a single star of same age.

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Section: Wr 20a As a Member Of Westerlundmentioning

confidence: 81%

The spectrum of the very massive binary system WR 20a (WN6ha + WN6ha): Fundamental parameters and wind interactions

Rauw¹,

Crowther

Becker³

et al. 2005

A&A

137

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“…Very briefly, T eff is derived from broadband colors, taking the mean estimates deduced from the de-reddened V À K and V À J colors, where the infrared colors are from the Two Micron All Sky Survey (2MASS; Skrutskie et al 1997). The corrections due to slight differences in filter bandpasses between the 2MASS and the CIT JHK systems are small ( 0.02 mag; Carpenter 2001), and we ignore them.…”

Section: Stellar Parametersmentioning

confidence: 99%

Abundances In Very Metal‐Poor Dwarf Stars

Cohen

Christlieb

McWilliam

et al. 2004

ApJ

181

277

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We discuss the detailed composition of 28 extremely metal-poor (EMP) dwarfs, 22 of which are from the Hamburg / ESO Survey (HES), based on Keck echelle spectra. Our sample has a median [Fe/H] of À2.7 dex, extends to À3.5 dex, and is somewhat less metal-poor than was expected from [Fe/H](HK, HES) determined from low-resolution spectra. Our analysis supports the existence of a sharp decline in the distribution of halo stars with metallicity below ½Fe=H ¼ À3:0 dex. So far no additional turnoff stars with ½Fe=H < À3:5 have been identified in our follow-up efforts. For the best-observed elements between Mg and Ni, we find that the abundance ratios appear to have reached a plateau, i.e., [X/Fe] is approximately constant as a function of [Fe/H], except for Cr, Mn, and Co, which show trends of abundance ratios varying with [Fe/H]. These abundance ratios at low metallicity correspond approximately to the yield expected from Type II supernovae (SNe) with a narrow range in mass and explosion parameters; high-mass Type II SN progenitors are required. The dispersion of [X/Fe] about this plateau level is surprisingly small and is still dominated by measurement errors rather than intrinsic scatter. These results place strong constraints on the characteristics of the contributing SNe. The dispersion in neutron-capture elements and the abundance trends for Cr, Mn, and Co are consistent with previous studies of evolved EMP stars. We find halo-like enhancements for the -elements Mg, Ca, and Ti, but solar Si / Fe ratios for these dwarfs. This contrasts with studies of EMP giant stars, which show Si enhancements similar to other -elements. Sc/ Fe is another case where the results from EMP dwarfs and from EMP giants disagree; our Sc/ Fe ratios are enhanced compared to the solar value by $0.2 dex. Although this conflicts with the solar Sc/ Fe values seen in EMP giants, we note that -like Sc/ Fe ratios have been claimed for dwarfs at higher metallicity. Two dwarfs in the sample are carbon stars, while two others have significant C enhancements, all with 12 C/ 13 C $7 and with C/ N between 10 and 150. Three of these C-rich stars have large enhancements of the heavy neutron capture elements, including lead, which implies a strong s-process contribution, presumably from binary mass transfer; the fourth shows no excess of Sr or Ba.

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“…from the 2 Micron All Sky Survey (2MASS; Skrutskie et al 1997). For a search redius of 10 , three QSOs and one Seyfert 1 were identified with 2MASS-sources.…”

Section: Red Qsosmentioning

confidence: 99%

A QSO survey via optical variability and zero proper motion in the M 92 field

Meusinger¹,

Brunzendorf²

2001

A&A

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Abstract. The combination of variability and proper motion constraints (VPM search) is believed to provide an efficient yet unconventional search strategy for QSOs with selection effects quite different from conventional optical QSO surveys. We performed a VPM QSO search in a 10 square degrees field around M 92 on 162 selected digitised Schmidt plates in the Johnson B band with a time-baseline of more than three decades. In Paper I, we constructed a sample of VPM QSO candidates with B ≤ 19.7. The spectroscopic follow-up observations revealed 58 QSOs and 7 Seyfert 1 galaxies as well as 27 narrow-emission line galaxies. We present the lowresolution spectra and the data for the QSOs and Seyfert galaxies: AGN types, accurate positions, redshifts, mean B magnitudes, and colour indices, along with the selection parameters of the VPM search, i.e., indices for variability, proper motion, and image structure. The redshifts cover the interval 0 < ∼ z < ∼ 3; absolute magnitudes are in the range −21 < ∼ MB < ∼ −29. The statistical properties of the resulting QSO sample are studied in detail. No significant differences were found between our VPM QSO sample and published QSO samples from multicolour or spectroscopic surveys. The fraction of QSOs with unusual colours is estimated to be less than 5 per cent within the magnitude range B ≤ 19.7.

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The Two Micron All Sky Survey (2MASS): Overview and Status

Cited by 245 publications

References 1 publication

The spectrum of the very massive binary system WR 20a (WN6ha + WN6ha): Fundamental parameters and wind interactions

The spectrum of the very massive binary system WR 20a (WN6ha + WN6ha): Fundamental parameters and wind interactions

Abundances In Very Metal‐Poor Dwarf Stars

A QSO survey via optical variability and zero proper motion in the M 92 field

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