5 research outputs found
A Mass-Magnitude Relation for Low-mass Stars Based on Dynamical Measurements of Thousands of Binary Star Systems
Stellar mass is a fundamental parameter that is key to our understanding of
stellar formation and evolution, as well as the characterization of nearby
exoplanet companions. Historically, stellar masses have been derived from
long-term observations of visual or spectroscopic binary star systems. While
advances in high-resolution imaging have enabled observations of systems with
shorter orbital periods, stellar mass measurements remain challenging, and
relatively few have been precisely measured. We present a new statistical
approach to measuring masses for populations of stars. Using Gaia astrometry,
we analyze the relative orbital motion of wide binary systems
comprising low-mass stars to establish a Mass-Magnitude relation in the Gaia
band spanning the absolute magnitude range
, corresponding to a mass range of
~M~M. This relation is directly
applicable to million stars in the Gaia catalog. Based on comparison to
existing Mass-Magnitude relations calibrated for 2MASS magnitudes, we
estimate that the internal precision of our mass estimates is 10. We
use this relation to estimate masses for a volume-limited sample of
18,200 stars within 50~pc of the Sun and the present-day field mass
function for stars with ~M, which we find peaks at
0.16~M. We investigate a volume-limited sample of wide binary systems
with early K dwarf primaries, complete for binary mass ratios , and
measure the distribution of at separations ~au. We find that our
distribution of is not uniformly distributed, rather decreasing towards
.Comment: 13 pages, 8 figure
Improving the Thermal Stability of a CCD Through Clocking
Modern precise radial velocity spectrometers are designed to infer the
existence of planets orbiting other stars by measuring few-nm shifts in the
positions of stellar spectral lines recorded at high spectral resolution on a
large-area digital detector. While the spectrometer may be highly stabilized in
terms of temperature, the detector itself may undergo changes in temperature
during readout that are an order of magnitude or more larger than the other
opto-mechanical components within the instrument. These variations in detector
temperature can translate directly into systematic measurement errors. We
explore a technique for reducing the amplitude of CCD temperature variations by
shuffling charge within a pixel in the parallel direction during integration.
We find that this "dither clocking" mode greatly reduces temperature variations
in the CCDs being tested for the NEID spectrometer. We investigate several
potential negative effects this clocking scheme could have on the underlying
spectral data.Comment: Submitted to JATIS, special issue from the ISPA 2018 conference. 11
pages, 9 figure
The HD 217107 planetary system: Twenty years of radial velocity measurements
The hot Jupiter HD 217107 b was one of the first exoplanets detected using the radial velocity (RV) method, originally reported in the literature in 1999. Today, precise RV measurements of this system span more than 20 years, and there is clear evidence of a longer-period companion, HD 217107 c. Interestingly, both the short-period planet (Pb ∼ 7.13 d) and long-period planet (Pc ∼ 5059 d) have significantly eccentric orbits (eb ∼ 0.13 and ec ∼ 0.40). We present 42 additional RV measurements of this system obtained with the MINERVA telescope array and carry out a joint analysis with previously published RV measurements from four different facilities. We confirm and refine the previously reported orbit of the long-period companion. HD 217107 b is one of a relatively small number of hot Jupiters with an eccentric orbit, opening up the possibility of detecting the precession of the planetary orbit due to general relativistic effects and perturbations from other planets in the system. In this case, the argument of periastron, ω, is predicted to change at the level of ∼0.8∘ century-1. Despite the long time baseline of our observations and the high quality of the RV measurements, we are only able to constrain the precession to be ω̇<65.9∘ century-1. We discuss the limitations of detecting the subtle effects of precession in exoplanet orbits using RV data