Understanding Fundamental Properties and Atmospheric Features of Subdwarfs via a Case Study of SDSS J125637.13-022452.4
Abstract
We present the distance-calibrated spectral energy distribution (SED) of the sdL3.5 subdwarf SDSS J125637.13-022452.4 (J1256-0224) using its Gaia DR2 parallax. We report the bolometric luminosity and semi-empirical fundamental parameters, as well as updated UVW velocities. The SED of J1256-0224 is compared to field-age and low-gravity dwarfs of the same effective temperature (T eff) and bolometric luminosity. In the former comparison, we find that the SED of J1256-0224 is brighter than the field source in the optical, but dims in comparison beyond the J band, where it becomes fainter than the field from the H through W2 bands. Compared to the young source, it is fainter at all wavelengths. We conclude that J1256-0224 is depleted of condensates compared to both objects. A near-infrared band-by-band analysis of the spectral features of J1256-0224 is done and is compared to the equivalent T eff sample. From this analysis, we find a peculiar behavior of the J-band K I doublets whereby the 1.17 μm doublet is stronger than the field or young source, as expected, while the 1.25 μm doublet shows indications of low gravity. In examining a sample of four other subdwarfs with comparable data, we confirm this trend across different subtypes indicating that the 1.25 μm doublet is a poor indicator of gravity for low-metallicity objects. In the K-band analysis of J1256-0224, we detect the 2.29 μm CO line of J1256-0224, previously unseen in the low-resolution SpeX data. We also present fundamental parameters using Gaia parallaxes for nine additional subdwarfs with spectral types M7-L7 for comparison. The 10 subdwarfs are placed in a temperature sequence, and we find a poor linear correlation with spectral type. We present polynomial relations for absolute magnitude in JHKW1W2, effective temperature, and bolometric luminosity versus spectral type for subdwarfs.
This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 2018
- DOI:
- 10.3847/1538-4357/aad3c7
- arXiv:
- arXiv:1807.04794
- Bibcode:
- 2018ApJ...864..100G
- Keywords:
-
- brown dwarfs;
- stars: fundamental parameters;
- stars: individual: SDSS J125637.13-022452.4;
- Gaia DR2 3685444645661181696;
- stars: low-mass;
- subdwarfs;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 24 pages, 14 figures, submitted to ApJ 2/1/2018, accepted 7/12/2018