Hydrogen lines in LAMOST low resolution spectra of RR Lyrae stars

Abstract

The LAMOST spectroscopic survey for Galactic structure and evolution has been in operation since October 2012, following a one-year pilot survey. The pilot survey produced a data release containing over 600,000 stellar spectra. By cross-checking with a large time series photometric database of RR Lyrae stars in high Galactic latitude regions, we found a total number of 157 stars that have been observed with LAMOST. In this sample, we successfully captured three RR Lyrae stars in the fast expansion phase, all of them showing significant hypersonic shock wave features in the spectra. By fitting the Hα line shape, we determine that the emission features seen within the broader Hα absorption line suggest hypersonic relative motions in the atmospheres of these three objects. With a further LAMOST survey of millions of stars, we will capture a large sample of RR Lyrae stars in their hypersonic expansion phase, and therefore provide a large database for the study of the internal structure and pulsation mechanism of RR Lyrae stars.

17 pages, 3 figures, Accepted by New Astronomy

References in corpus (7)

• The Milky Way's Circular Velocity Curve to 60 kpc and an Estimate of the Dark Matter Halo Mass from Kinematics of ~2400 SDSS Blue Horizontal Branch Stars
• LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) The survey science plan
• Probing the Outer Galactic halo with RR Lyrae from the Catalina Surveys
• Template RR Lyrae H alpha, H beta, and H gamma Velocity Curves
• The selection of LEGUE disk targets for LAMOST's pilot survey
• The LEGUE High Latitude Bright Survey Design for the LAMOST Pilot Survey
• The LEGUE Input Catalogue for Dark Night Observing in the LAMOST Pilot Survey

Cited by in corpus (7)

• LAMOST Spectroscopic Survey of the Galactic Anti-centre (LSS-GAC): target selection and the first release of value-added catalogues
• The Bulge Radial Velocity Assay for RR Lyrae stars (BRAVA-RR) DR2: a Bimodal Bulge?
• A new catalogue of radial velocity standard stars from the APOGEE data
• Solar and Stellar Photospheric Abundances
• Possible evidence of hydrogen emission in the first-overtone and multi-mode RR Lyrae variables
• Spectral Identification of the u-band Variable Sources in Two LAMOST fields
• Blueshifted hydrogen emission and shock wave of RR Lyrae variables in SDSS and LAMOST