arXiv subjects

Joseph Huehnerhoff

Publications and source records attributed to Joseph Huehnerhoff.

5 recordsLinked to original sources

arXiv2019

A sub-Neptune sized planet transiting the M2.5-dwarf G 9-40: Validation with the Habitable-zone Planet Finder

We validate the discovery of a 2 Earth radii sub-Neptune-size planet around the nearby high proper motion M2.5-dwarf G 9-40 (EPIC 212048748), using high-precision near-infrared (NIR) radial velocity (RV) observations with the Habitable-zone Planet Finder (HPF), precision diffuser-assisted ground-based photometry with a custom narrow-band photometric filter, and adaptive optics imaging. At a distance of $d=27.9\mathrm{pc}$, G 9-40b is the second closest transiting planet discovered by K2 to date. The planet's large transit depth ($\sim$3500ppm), combined with the proximity and brightness of the host star at NIR wavelengths (J=10, K=9.2) makes G 9-40b one of the most favorable sub-Neptune-sized planet orbiting an M-dwarf for transmission spectroscopy with JWST, ARIEL, and the upcoming Extremely Large Telescopes. The star is relatively inactive with a rotation period of $\sim$29 days determined from the K2 photometry. To estimate spectroscopic stellar parameters, we describe our implementation of an empirical spectral matching algorithm using the high-resolution NIR HPF spectra. Using this algorithm, we obtain an effective temperature of $T_{\mathrm{eff}}=3404\pm73$K, and metallicity of $\mathrm{[Fe/H]}=-0.08\pm0.13$. Our RVs, when coupled with the orbital parameters derived from the transit photometry, exclude planet masses above $11.7 M_\oplus$ with 99.7% confidence assuming a circular orbit. From its radius, we predict a mass of $M=5.0^{+3.8}_{-1.9} M_\oplus$ and an RV semi-amplitude of $K=4.1^{+3.1}_{-1.6}\mathrm{m\:s^{-1}}$, making its mass measurable with current RV facilities. We urge further RV follow-up observations to precisely measure its mass, to enable precise transmission spectroscopic measurements in the future.

astro-ph.EP↗

arXiv2018

Diffuser-assisted Photometric Follow-up Observations of the Neptune-sized Planets K2-28b and K2-100b

We present precision transit observations of the Neptune-sized planets K2-28b and K2-100b, using the Engineered Diffuser on the ARCTIC imager on the ARC 3.5m Telescope at Apache Point Observatory. K2-28b is a $R_{p} = 2.56 R_\oplus$ mini-Neptune transiting a bright (J=11.7) metal-rich M4 dwarf, offering compelling prospects for future atmospheric characterization. K2-100b is a $R_{p} = 3.45 R_\oplus$ Neptune in the Praesepe Cluster and is one of few planets known in a cluster transiting a host star bright enough ($V=10.5$) for precision radial velocity observations. Using the precision photometric capabilities of the diffuser/ARCTIC system, allows us to achieve a precision of $105^{+87}_{-37}$ppm, and $38^{+21}_{-11}$ppm in 30 minute bins for K2-28b, and K2-100b, respectively. Our joint-fits to the K2 and ground-based light-curves give an order of magnitude improvement in the orbital ephemeris for both planets, yielding a timing precision of 2min in the JWST era. Although we show that the currently available broad-band measurements of K2-28b's radius are currently too imprecise to place useful constraints on K2-28b's atmosphere, we demonstrate that JWST/NIRISS will be able to discern between a cloudy/clear atmosphere in a modest number of transit observations. Our light-curve of K2-100b marks the first transit follow-up observation of this challenging-to-observe transit, where we obtain a transit depth of $819 \pm 50 \mathrm{ppm}$ in the SDSS $i^\prime$ band. We conclude that diffuser-assisted photometry can play an important role in the TESS era to perform timely and precise follow-up of the expected bounty of TESS planet candidates.

astro-ph.EP↗

arXiv2017

Towards Space-like Photometric Precision from the Ground with Beam-Shaping Diffusers

We demonstrate a path to hitherto unachievable differential photometric precisions from the ground, both in the optical and near-infrared (NIR), using custom-fabricated beam-shaping diffusers produced using specialized nanofabrication techniques. Such diffusers mold the focal plane image of a star into a broad and stable top-hat shape, minimizing photometric errors due to non-uniform pixel response, atmospheric seeing effects, imperfect guiding, and telescope-induced variable aberrations seen in defocusing. This PSF reshaping significantly increases the achievable dynamic range of our observations, increasing our observing efficiency and thus better averages over scintillation. Diffusers work in both collimated and converging beams. We present diffuser-assisted optical observations demonstrating $62^{+26}_{-16}$ppm precision in 30 minute bins on a nearby bright star 16-Cygni A (V=5.95) using the ARC 3.5m telescope---within a factor of $\sim$2 of Kepler's photometric precision on the same star. We also show a transit of WASP-85-Ab (V=11.2) and TRES-3b (V=12.4), where the residuals bin down to $180^{+66}_{-41}$ppm in 30 minute bins for WASP-85-Ab---a factor of $\sim$4 of the precision achieved by the K2 mission on this target---and to 101ppm for TRES-3b. In the NIR, where diffusers may provide even more significant improvements over the current state of the art, our preliminary tests have demonstrated $137^{+64}_{-36}$ppm precision for a $K_S =10.8$ star on the 200" Hale Telescope. These photometric precisions match or surpass the expected photometric precisions of TESS for the same magnitude range. This technology is inexpensive, scalable, easily adaptable, and can have an important and immediate impact on the observations of transits and secondary eclipses of exoplanets.

astro-ph.IM↗

arXiv2014

The Tenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Apache Point Observatory Galactic Evolution Experiment

The Sloan Digital Sky Survey (SDSS) has been in operation since 2000 April. This paper presents the tenth public data release (DR10) from its current incarnation, SDSS-III. This data release includes the first spectroscopic data from the Apache Point Observatory Galaxy Evolution Experiment (APOGEE), along with spectroscopic data from the Baryon Oscillation Spectroscopic Survey (BOSS) taken through 2012 July. The APOGEE instrument is a near-infrared R~22,500 300-fiber spectrograph covering 1.514--1.696 microns. The APOGEE survey is studying the chemical abundances and radial velocities of roughly 100,000 red giant star candidates in the bulge, bar, disk, and halo of the Milky Way. DR10 includes 178,397 spectra of 57,454 stars, each typically observed three or more times, from APOGEE. Derived quantities from these spectra (radial velocities, effective temperatures, surface gravities, and metallicities) are also included.DR10 also roughly doubles the number of BOSS spectra over those included in the ninth data release. DR10 includes a total of 1,507,954 BOSS spectra, comprising 927,844 galaxy spectra; 182,009 quasar spectra; and 159,327 stellar spectra, selected over 6373.2 square degrees.

astro-ph.IM↗

arXiv2013

A Study of the Unusual Z Cam Systems IW Andromedae and V513 Cassiopeia

The Z Cam stars IW And and V513 Cas are unusual in having outbursts following their standstills in contrast to the usual Z Cam behavior of quiescence following standstills. In order to gain further understanding of these little-studied systems, we obtained spectra correlated with photometry from the AAVSO throughout a 3-4 month interval in 2011. In addition, time-resolved spectra were obtained in 2012 that provided orbital periods of 3.7 hrs for IW And and 5.2 hrs for V513 Cas. The photometry of V513 Cas revealed a regular pattern of standstills and outbursts with little time at quiescence, while IW And underwent many excursions from quiescence to outburst to short standstills. The spectra of IW And are similar to normal dwarf novae, with strong Balmer emission at quiescence and absorption at outburst. In contrast, V513 Cas shows a much flatter/redder spectrum near outburst with strong HeII emission and prominent emission cores in the Balmer lines. Part of this continuum difference may be due to reddening effects. While our attempts to model the outburst and standstill states of IW And indicate a mass accretion rate near 3E-9 solar masses per year, we could find no obvious reason why these systems behave differently following standstill compared to normal Z Cam stars.

astro-ph.SR↗