An ancient F-type subdwarf from the halo crossing the Galactic plane

Scholz RD, Heber U, Heuser C, Ziegerer E, Geier S, Niederhofer F (2015)

Publication Status: Published

Publication Type: Journal article

Publication year: 2015

Journal

Astronomy & Astrophysics EDP Sciences

Publisher: EDP SCIENCES S A

Book Volume: 574

Article Number: ARTN A96

DOI: 10.1051/0004-6361/201425471

Abstract

Aims. We selected the bluest object, WISE J0725-2351, from Luhman's new high proper motion (HPM) survey based on observations with the Wide-field Infrared Survey Explorer (WISE) for spectroscopic follow-up observations. Our aim was to unravel the nature of this relatively bright (V similar to 12, J similar to 11) HPM star (mu = 267 mas/yr).Methods. We obtained low-and medium-resolution spectra with the European Southern Observatory (ESO) New Technology Telescope (NTT)/EFOSC2 and Very Large Telescope (VLT)/X-Shooter instruments, investigated the radial velocity and performed a quantitative spectral analysis that allowed us to determine physical parameters. The fit of the spectral energy distribution based on the available photometry to low-metallicity model spectra and the similarity of our target to a metal-poor benchmark star (HD 84937) allowed us to estimate the distance and space velocity.Results. As in the case of HD 84937, we classified WISE J0725-2351 as sdF5: or a metal-poor turnoff star with [Fe/H] = -2.0 +/- 0.2, T-eff = 6250 +/- 100 K, log g = 4.0 +/- 0.2, and a possible age of about 12 Gyr. At an estimated distance of more than 400 pc, its proper motion translates to a tangential velocity of more than 500 km s(-1). Together with its constant (on timescales of hours, days, and months) and large radial velocity (about +240 km s(-1)), the resulting Galactic restframe velocity is about 460 km s(-1), implying a bound retrograde orbit for this extreme halo object that currently crosses the Galactic plane at high speed.

Authors with CRIS profile

Ulrich Heber Professur für Astronomie und Astrophysik Christian Heuser Dr.Karl-Remeis-Sternwarte Bamberg, Astronomisches Institut Eva Ziegerer Dr.Karl-Remeis-Sternwarte Bamberg, Astronomisches Institut

Involved external institutions

European Southern Observatory (ESO) DE Germany (DE) Leibniz Institute for Astrophysics Potsdam / Leibniz-Institut für Astrophysik Potsdam DE Germany (DE)

How to cite

APA:

Scholz, R.-D., Heber, U., Heuser, C., Ziegerer, E., Geier, S., & Niederhofer, F. (2015). An ancient F-type subdwarf from the halo crossing the Galactic plane. Astronomy & Astrophysics, 574. https://doi.org/10.1051/0004-6361/201425471

MLA:

Scholz, R. -D., et al. "An ancient F-type subdwarf from the halo crossing the Galactic plane." Astronomy & Astrophysics 574 (2015).

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