Magnetic inflation and stellar mass. IV. four low-mass kepler eclipsing binaries consistent with non-magnetic stellar evolutionary models

Low-mass eclipsing binaries (EBs) show systematically larger radii than model predictions for their mass, metallicity, and age. Prominent explanations for the inflation involve enhanced magnetic fields generated by rapid rotation of the star that inhibit convection and/or suppress flux from the star via starspots. However, derived masses and radii for individual EB systems often disagree in the literature. In this paper, we continue to investigate low-mass EBs observed by NASA’s Kepler spacecraft, deriving stellar masses and radii using high-quality spacebased light curves and radial velocities from high-resolution infrared spectroscopy. We report masses and radii for three Kepler EBs, two of which agree with previously published masses and radii (KIC 11922782 and KIC 9821078). For the third EB (KIC 7605600), we report new masses and show the secondary component is likely fully convective (M2 = 0.17 ± 0.01M☉ and = - ☉ + R2 0.199 0.002R 0.001 ). Combined with KIC 10935310 from Han et al., we find that the masses and radii for four low-mass Kepler EBs are consistent with modern stellar evolutionary models for M dwarf stars and do not require inhibited convection by magnetic fields to account for the stellar radii.Published versio

Magnetic inflation and stellar mass. III. revised parameters for the component stars of NSVS 07394765

We perform a new analysis of the M-dwarf–M-dwarf eclipsing binary system NSVS 07394765 in order to investigate the reported hyper-inflated radius of one of the component stars. Our analysis is based on archival photometry from the Wide Angle Search for Planets, new photometry from the 32 cm Command Module Observatory telescope in Arizona and the 70 cm telescope at Thacher Observatory in California, and new high-resolution infrared spectra obtained with the Immersion Grating Infrared Spectrograph on the Discovery Channel Telescope. The masses and radii we measure for each component star disagree with previously reported measurements. We show that both stars are early M-type main-sequence stars without evidence for youth or hyper-inflation ( = - ☉ M M + 1 0.661 0.036 0.008 , = - ☉ M M + 2 0.608 0.028 0.003 , = - ☉ + R1 0.599 0.019 R 0.032 , = - ☉ + R2 0.625 0.027 R 0.012 ), and we update the orbital period and eclipse ephemerides for the system. We suggest that the likely cause of the initial hyper-inflated result is the use of moderate-resolution spectroscopy for precise radial velocity measurements.Published versio

The Masses of Transition Circumstellar Disks: Observational Support for Photoevaporation Models

We report deep Sub-Millimeter Array observations of 26 pre-main-sequence (PMS) stars with evolved inner disks. These observations measure the mass of the outer disk (r ~20-100 AU) across every stage of the dissipation of the inner disk (r < 10 AU) as determined by the IR spectral energy distributions (SEDs). We find that only targets with high mid-IR excesses are detected and have disk masses in the 1-5 M_Jup range, while most of our objects remain undetected to sensitivity levels of M_DISK ~0.2-1.5 M_Jup. To put these results in a more general context, we collected publicly available data to construct the optical to millimeter wavelength SEDs of over 120 additional PMS stars. We find that the near-IR and mid-IR emission remain optically thick in objects whose disk masses span 2 orders of magnitude (~0.5-50 M_Jup). Taken together, these results imply that, in general, inner disks start to dissipate only after the outer disk has been significantly depleted of mass. This provides strong support for photoevaporation being one of the dominant processes driving disk evolution.Comment: Accepted for publication by ApJL, 4 pages and 3 figure

A Pre-Protostellar Core in L1551

Large field surveys of NH3, C2S, 13CO and C18O in the L1551 dark cloud have revealed a prolate, pre-protostellar molecular core (L1551-MC) in a relatively quiescent region to the northwest of the well-known IRS 5 source. The kinetic temperature is measured to be 9K, the total mass is ~2Msun, and the average particle density is 10^4-10^5 cm^(-3). L1551-MC is 2.25' x 1.11' in projection oriented at a position angle of 133deg. The turbulent motions are on the order of the sound speed in the medium and contain 4% of the gravitational energy, E_{grav}, of the core. The angular momentum vector is projected along the major axis of L1551-MC corresponding to a rotational energy of 2.5E-3(sin i)^(-2)|E_{grav}|. The thermal energy constitutes about a third of |E_{grav}| and the virial mass is approximately equal to the total mass. L1551-MC is gravitationally bound and in the absence of strong, ~160 microgauss, magnetic fields will likely contract on a ~0.3 Myr time scale. The line profiles of many molecular species suggest that the cold quiescent interior is surrounded by a dynamic, perhaps infalling envelope which is embedded within the ambient molecular gas of L1551.Comment: 27 pages, 7 figures, ApJ accepte

Kepler-445, Kepler-446 And The Occurrence Of Compact Multiples Orbiting Mid-M Dwarf Stars

We confirm and characterize the exoplanetary systems Kepler-445 and Kepler-446: two mid-M dwarf stars, each with multiple, small, short-period transiting planets. Kepler-445 is a metal-rich ([ Fe/H] = + 0.25 0.10) M4 dwarf with three transiting planets, and Kepler-446 is a metal-poor ([ Fe/H] = -0.30 0.10) M4 dwarf also with three transiting planets. Kepler-445c is similar toGJ 1214b: both in planetary radius and the properties of the host star. The Kepler-446 system is similar to the Kepler-42 system: both are metal-poor with large galactic space velocities and three short-period, likely rocky transiting planets that were initially assigned erroneously large planet-to-star radius ratios. We independently determined stellar parameters from spectroscopy and searched for and fitted the transit light curves for the planets, imposing a strict prior on stellar density in order to remove correlations between the fitted impact parameter and planet-to-star radius ratio for short-duration transits. Combining Kepler-445, Kepler-446, and Kepler-42, and isolating all mid-M dwarf stars observed by Kepler with the precision necessary to detect similar systems, we calculate that 21+ 7 -5 % of mid-M dwarf stars host compact multiples ( multiple planets with periods of less than 10 days) for a wide range of metallicities. We suggest that the inferred planet masses for these systems support highly efficient accretion of protoplanetary disk metals by mid-M dwarf protoplanets.NSF DGE1144152, AST-1005313NASA NAS5-26555NASA Office of Space Science NNX13AC07GAstronom

The gold standard: accurate stellar and planetary parameters for eight Kepler M dwarf systems enabled by parallaxes

We report parallaxes and proper motions from the Hawaii Infrared Parallax Program for eight nearby M dwarf stars with transiting exoplanets discovered by Kepler. We combine our directly measured distances with mass-luminosity and radius–luminosity relationships to significantly improve constraints on the host stars’ properties. Our astrometry enables the identification of wide stellar companions to the planet hosts. Within our limited sample, all the multi-transiting planet hosts (three of three) appear to be single stars, while nearly all (four of five) of the systems with a single detected planet have wide stellar companions. By applying strict priors on average stellar density from our updated radius and mass in our transit fitting analysis, we measure the eccentricity probability distributions for each transiting planet. Planets in single-star systems tend to have smaller eccentricities than those in binaries, although this difference is not significant in our small sample. In the case of Kepler-42bcd, where the eccentricities are known to be ≃0, we demonstrate that such systems can serve as powerful tests of M dwarf evolutionary models by working in L⋆ − ρ⋆ space. The transit-fit density for Kepler- 42bcd is inconsistent with model predictions at 2.1σ (22%), but matches more empirical estimates at 0.2σ (2%), consistent with earlier results showing model radii of M dwarfs are underinflated. Gaia will provide high-precision parallaxes for the entire Kepler M dwarf sample, and TESS will identify more planets transiting nearby, late-type stars, enabling significant improvements in our understanding of the eccentricity distribution of small planets and the parameters of late-type dwarfs.Support for Program number HST-HF2-51364.001-A was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.Some of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX09AF08G and by other grants and contracts. This paper includes data collected by the Kepler mission. Funding for the Kepler mission is provided by the NASA Science Mission directorate. The authors acknowledge the Texas Advanced Computing Center (TACC) at The University of Texas at Austin for providing HPC resources that have contributed to the research results reported within this paper. URL: http://www.tacc.utexas.edu. (HST-HF2-51364.001-A - NASA through Space Telescope Science Institute; NAS5-26555 - NASA; NNX09AF08G - NASA Office of Space Science; NASA Science Mission directorate

Magnetic Inflation and Stellar Mass. I. Revised Parameters for the Component Stars of the Kepler Low-mass Eclipsing Binary T-Cyg1-12664

Several low-mass eclipsing binary stars show larger than expected radii for their measured mass, metallicity, and age. One proposed mechanism for this radius inflation involves inhibited internal convection and starspots caused by strong magnetic fields. One particular eclipsing binary, T-Cyg1-12664, has proven confounding to this scenario. Çakırlı et al. measured a radius for the secondary component that is twice as large as model predictions for stars with the same mass and age, but a primary mass that is consistent with predictions. Iglesias-Marzoa et al. independently measured the radii and masses of the component stars and found that the radius of the secondary is not in fact inflated with respect to models, but that the primary is, which is consistent with the inhibited convection scenario. However, in their mass determinations, Iglesias-Marzoa et al. lacked independent radial velocity measurements for the secondary component due to the star's faintness at optical wavelengths. The secondary component is especially interesting, as its purported mass is near the transition from partially convective to a fully convective interior. In this article, we independently determined the masses and radii of the component stars of T-Cyg1-12664 using archival Kepler data and radial velocity measurements of both component stars obtained with IGRINS on the Discovery Channel Telescope and NIRSPEC and HIRES on the Keck Telescopes. We show that neither of the component stars is inflated with respect to models. Our results are broadly consistent with modern stellar evolutionary models for main-sequence M dwarf stars and do not require inhibited convection by magnetic fields to account for the stellar radii

Characterizing the Cool KOIs. IV. Kepler-32 as a Prototype for the Formation of Compact Planetary Systems throughout the Galaxy

The Kepler space telescope has opened new vistas in exoplanet discovery space by revealing populations of Earth-sized planets that provide a new context for understanding planet formation. Approximately 70% of all stars in the Galaxy belong to the diminutive M dwarf class, several thousand of which lie within Kepler's field of view, and a large number of these targets show planet transit signals. The Kepler M dwarf sample has a characteristic mass of 0.5 M_☉ representing a stellar population twice as common as Sun-like stars. Kepler-32 is a typical star in this sample that presents us with a rare opportunity: five planets transit this star, giving us an expansive view of its architecture. All five planets of this compact system orbit their host star within a distance one-third the size of Mercury's orbit, with the innermost planet positioned a mere 4.3 stellar radii from the stellar photosphere. New observations limit possible false positive scenarios, allowing us to validate the entire Kepler-32 system making it the richest known system of transiting planets around an M dwarf. Based on considerations of the stellar dust sublimation radius, a minimum mass protoplanetary nebula, and the near period commensurability of three adjacent planets, we propose that the Kepler-32 planets formed at larger orbital radii and migrated inward to their present locations. The volatile content inferred for the Kepler-32 planets and order of magnitude estimates for the disk migration rates suggest that these planets may have formed beyond the snow line and migrated in the presence of a gaseous disk. If true, then this would place an upper limit on their formation time of ~10 Myr. The Kepler-32 planets are representative of the full ensemble of planet candidates orbiting the Kepler M dwarfs for which we calculate an occurrence rate of 1.0 ± 0.1 planet per star. The formation of the Kepler-32 planets therefore offers a plausible blueprint for the formation of one of the largest known populations of planets in our Galaxy

Synchronised transcranial magnetic stimulation for substance use-disordered Veterans: protocol for the pilot sham-controlled acceptability trial

Introduction: Substance use disorders (SUDs) take an enormous toll on US Veterans and civilians alike. Existing empirically supported interventions vary by substance and demonstrate only moderate efficacy. Non-invasive brain stimulation represents an innovative treatment for SUDs, yet aspects of traditional neurostimulation may hinder its implementation in SUD populations. Synchronised transcranial magnetic stimulation (sTMS) uses rotating rare earth magnets to deliver low-field stimulation synchronised to an individual\u27s alpha peak frequency that is safe for at-home administration. The current trial aims to assess the acceptability and feasibility of sTMS, as well as the safety of at-home sTMS administration for substance-disordered Veterans. Methods and analysis: Sixty Veterans in substance treatment at the Providence Veterans Affairs will be randomised to receive 6 weeks of active or sham sTMS treatment. Eligibility will be confirmed by meeting Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition criteria for an alcohol, cocaine or opioid use disorder. Daily supervised sTMS treatment will occur either in clinic or at home through video monitoring. Clinical and self-report assessments will be completed at baseline, end of treatment and 1-month follow-up. Urine drug screening will occur once per week during the treatment phase. Primary outcomes include treatment adherence/retention and satisfaction to evaluate sTMS feasibility and acceptability in Veterans with SUDs. The safety of at-home sTMS administration will be assessed via adverse event monitoring. Ethics and dissemination: The sTMS device received a significant risk determination for at-home use by the Food and Drug Administration in July 2021. Ethics approval was obtained in August 2021 from the Providence Veterans Affairs institutional review board and research and development committee. Data collection began in September 2021 and is planned to continue through December 2023. Findings will be disseminated at national conferences and in peer-reviewed journals. Results will serve to inform the development of large-scale clinical trials of sTMS efficacy for substance-disordered Veterans. Trial registration number ClinicalTrials.gov Registry (NCT04336293)

Design, motivation, and on-sky tests of an efficient fiber coupling unit for 1-meter class telescopes

We present the science motivation, design, and on-sky test data of a high-throughput fiber coupling unit suitable for automated 1-meter class telescopes. The optical and mechanical design of the fiber coupling is detailed and we describe a flexible controller software designed specifically for this unit. The system performance is characterized with a set of numerical simulations, and we present on-sky results that validate the performance of the controller and the expected throughput of the fiber coupling. This unit was designed specifically for the MINERVA array, a robotic observatory consisting of multiple 0.7 m telescopes linked to a single high-resolution stabilized spectrograph for the purpose of exoplanet discovery using high-cadence radial velocimetry. However, this unit could easily be used for general astronomical purposes requiring fiber coupling or precise guiding