Ground-based astronomical spectra are contaminated by the Earth's atmosphere to varying degrees in all spectral regions. We present a Python code that can accurately fit a model to the telluric absorption spectrum present in astronomical data, with residuals of ∼ 3 − 5% of the continuum for moderately strong lines. We demonstrate the quality of the correction by fitting the telluric spectrum in a nearly featureless A0V star, HIP 20264, as well as to a series of dwarf M star spectra near the 819 nm sodium doublet. We directly compare the results to an empirical telluric correction of HIP 20264 and find that our model-fitting procedure is at least as good and sometimes more accurate. The telluric correction code, which we make freely available to the astronomical community, can be used as a replacement for telluric standard star observations for many purposes.

Transiting planets around rapidly rotating stars are not amenable to precise radial velocity observations, such as are used for planet candidate validation, as they have wide, rotationally broadened stellar lines. Such planets can, however, be observed using Doppler tomography, wherein the stellar absorption line profile distortions during transit are spectroscopically resolved. This allows the validation of transiting planet candidates and the measurement of the stellar spin-planetary orbit (mis)alignment, an important statistical probe of planetary migration processes. We present Doppler tomographic observations which provide a direct confirmation of the hot Jupiter Kepler-13 Ab, and also show that the planet has a prograde, misaligned orbit, with λ = 58.6 • ± 2.0 • . Our measured value of the spin-orbit misalignment is in significant disagreement with the value of λ = 23 • ± 4 • previously measured by Barnes et al. (2011) from the gravity-darkened Kepler lightcurve. We also place an upper limit of 0.75M ⊙ (95% confidence) on the mass of Kepler-13 C, the spectroscopic companion to Kepler-13 B, the proper motion companion of the planet host star Kepler-13 A.

We present a mass determination for the transiting super-Earth ρ 1 Cancri e based on nearly 700 precise radial velocity (RV) measurements. This extensive RV data set consists of data collected by the McDonald Observatory planet search and published data from Lick and Keck observatories. We obtained 212 RV measurements with the Tull Coudé Spectrograph at the Harlan J. Smith 2.7 m Telescope and combined them with a new Doppler reduction of the 131 spectra that we have taken in 2003-2004 with the High-Resolution Spectrograph (HRS) at the Hobby-Eberly Telescope for the original discovery of ρ 1 Cancri e. Using this large data set we obtain a five-planet Keplerian orbital solution for the system and measure an RV semi-amplitude of K = 6.29 ± 0.21 m s −1 for ρ 1 Cnc e and determine a mass of 8.37 ± 0.38 M ⊕. The uncertainty in mass is thus less than 5%. This planet was previously found to transit its parent star, which allowed them to estimate its radius. Combined with the latest radius estimate from Gillon et al., we obtain a mean density of ρ = 4.50 ± 0.20 g cm −3. The location of ρ 1 Cnc e in the mass-radius diagram suggests that the planet contains a significant amount of volatiles, possibly a water-rich envelope surrounding a rocky core.

Binary stars and higher-order multiple systems are an ubiquitous outcome of star formation, especially as the system mass increases. The companion mass-ratio distribution is a unique probe into the conditions of the collapsing cloud core and circumstellar disk(s) of the binary fragments. Inside a ∼ 1000 AU the disks from the two forming stars can interact, and additionally companions can form directly through disk fragmentation. We should therefore expect the mass-ratio distribution of close companions (a 100 AU) to differ from that of wide companions. This prediction is difficult to test using traditional methods, especially with intermediate-mass primary stars, for a variety of observational reasons. We present the results of a survey searching for companions to A-and B-type stars using the direct spectral detection method, which is sensitive to late-type companions within ∼ 1 of the primary and which has no inner working angle. We estimate the temperatures and surface gravity of most of the 341 sample stars, and derive their masses and ages. We additionally estimate the temperatures and masses of the 64 companions we find, 23 of which are new detections. We find that the mass-ratio distribution for our sample has a maximum near q ∼ 0.3. Our mass-ratio distribution has a very different form than in previous work, where it is usually well-described by a power law, and indicates that close companions to intermediate-mass stars experience significantly different accretion histories or formation mechanisms than wide companions.

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