The MEarth project: searching for transiting habitable super-Earths around nearby M-dwarfs

Due to their small radii, M-dwarfs are very promising targets to search for transiting super-Earths, with a planet of 2 Earth radii orbiting an M5 dwarf in the habitable zone giving rise to a 0.5% photometric signal, with a period of two weeks. This can be detected from the ground using modest-aperture telescopes by targeting samples of nearby M-dwarfs. Such planets would be very amenable to follow-up studies due to the brightness of the parent stars, and the favourable planet-star flux ratio. MEarth is such a transit survey of ~2000 nearby M-dwarfs. Since the targets are distributed over the entire (Northern) sky, it is necessary to observe them individually, which will be done by using 8 independent 0.4m robotic telescopes, two of which have been in operation since December 2007 at the Fred Lawrence Whipple Observatory (FLWO) located on Mount Hopkins, Arizona. We discuss the survey design and hardware, and report on the current status of the survey, and preliminary results obtained from the commissioning data.Comment: 7 pages, 5 figures. To appear in the Proceedings of the 253rd IAU Symposium: "Transiting Planets", May 2008, Cambridge, M

An empirical calibration to estimate cool dwarf fundamental parameters from H-band spectra

Interferometric radius measurements provide a direct probe of the fundamental parameters of M dwarfs, but is within reach for only a limited sample of nearby, bright stars. We use interferometrically-measured radii, bolometric luminosities, and effective temperatures to develop new empirical calibrations based on low-resolution, near-infrared spectra. We use H-band Mg and Al features to derive calibrations for effective temperature, radius and log luminosity; the standard deviations in the residuals of our best fits are, respectively, 73K, 0.027Rsun, and 0.049 dex (11% error on luminosity). These relationships are valid for mid K to mid M dwarf stars, roughly corresponding to temperatures between 3100 and 4800K. We apply our calibrations to M dwarfs targeted by the MEarth transiting planet survey and to the cool Kepler Objects of Interest (KOIs). We independently validate our calibrations by demonstrating a clear relationship between our inferred parameters and the absolute K magnitudes of the MEarth stars, and we identify objects with magnitudes too bright for their estimated luminosities as candidate multiple systems. We also use our inferred luminosities to address the applicability of near-infrared metallicity calibrations to mid and late M dwarfs. The temperatures we infer for the KOIs agree remarkably well with those from the literature; however, our stellar radii are systematically larger than those presented in previous works that derive radii from model isochrones. This results in a mean planet radius that is 15% larger than one would infer using the stellar properties from recent catalogs. Our results confirm those of previous in-depth studies of Kepler-42, Kepler-45, and Kepler-186.Comment: Accepted to ApJ. Tables 4 and 5, and machine readable versions of Tables 5 and 7 are available in the ApJ journal articl

How SME owners' characteristics influence external advice and access to finance

Objectives: This paper aims to investigate the linkage between the use of external advice and access to finance for small and medium-sized enterprises (SMEs) in the UK, with particular consideration of differences in personal characteristics: gender, ethnicity and education. Prior work: There is little evidence on gender, ethnic and educational differentials in obtaining external advice, with the exception of a paper by Barrett (1995) comparing the use of external advice by men and women. In the UK an extensive programme of research into the use of external advice has been undertaken, primarily by Robert Bennett and Paul Robson drawing from the Cambridge Centre for Business Research survey of SMEs in manufacturing and business services. A large number of other articles investigate business advice, but few attempt to make comparisons by personal characteristics. Approach: The approach adopted for the research is a telephone survey conducted by the Barclays small business research team in late 2005 on behalf of the authors. These data are quantitative in nature and involve a large sample of 400 SMEs with specific questions analysed by gender, ethnicity and education level. The approach adopted is robust and empirically sound and is a long established research methodology. Results: We find that there appears to be a correlation between the provision of external advice and the ability to raise bank finance. Furthermore, there are clear gender, ethnic and educational differentials in the use of particular sources of advice which are explored in detail in the paper. Implications: The study is of much relevance to policy-makers and providers of external advice (whether private sector or Government backed sources of advice) in that it provides insight into differences by personal characteristics, and secondly into the correlation between business advice and accessing finance. Value: The paper is the first that compares sources of external advice by gender, ethnicity and educational level and is therefore a major contribution to the already highly-developed literature on external business advic

Effects of ultrasound on the growth and function of bone and periodontal ligament cells <i>in vitro</i>

The effects of therapeutic ultrasound (US) on tissue healing processes in vivo are likely to involve US-induced changes in key cellular functions. However, these have not yet been clearly delineated and the present study has, therefore, examined the effects of a single 5-min CW exposure of 3.00-MHz US on the growth and functional activity of a human osteoblast-like cell line (MG63 cells) and human periodontal ligament (PDL) cells in vitro. Although cell proliferation was found to be largely unaffected by spatial average intensity (ISA) values of between 140–990 mW/cm2, flow cytometry (FCM) analysis showed that there were pronounced and differential effects on cell function. Thus, bone-associated proteins were down-regulated, whereas collagen type I (COL I) was unaffected and fibronectin (FN) was up-regulated at low intensities in MG63 cells. In contrast, bone protein expression was found to be dose-dependent, and FN and COL I were down-regulated in PDL cells. These results show that US has potentially important effects on the functional activities of connective tissue cells in vitro, which could markedly influence tissue repair and regeneration processes in vivo

Trigonometric Parallaxes for 1,507 Nearby Mid-to-Late M-dwarfs

The MEarth survey is a search for small rocky planets around the smallest, nearest stars to the Sun as identified by high proper motion with red colors. We augmented our planetary search time series with lower cadence astrometric imaging and obtained two million images of approximately 1800 stars suspected to be mid-to-late M dwarfs. We fit an astrometric model to MEarth's images for 1507 stars and obtained trigonometric distance measurements to each star with an average precision of 5 milliarcseconds. Our measurements, combined with the 2MASS photometry, allowed us to obtain an absolute K_s magnitude for each star. In turn, this allows us to better estimate the stellar parameters than those obtained with photometric estimates alone and to better prioritize the targets chosen to monitor at high cadence for planetary transits. The MEarth sample is mostly complete out to a distance of 25 parsecs for stars of type M5.5V and earlier, and mostly complete for later type stars out to 20 parsecs. We find eight stars that are within ten parsecs of the Sun for which there did not exist a published trigonometric parallax distance estimate. We release with this work a catalog of the trigonometric parallax measurements for 1,507 mid-to-late M-dwarfs, as well as new estimates of their masses and radii.Comment: ApJ, accepted. 36 pages, 8 figures, 2 tables. Please find our data table here: http://www.cfa.harvard.edu/MEarth/DataDR2.htm

Barriers faced by SMEs in raising bank finance

Purpose – The purpose of this paper is to use univariate statistical analysis to investigate barriers to raising bank finance faced by UK small and medium‐sized enterprises (SMEs), specifically the impact of personal characteristics (ethnicity, gender and education). Design/methodology/approach – A conceptual model was developed and the results of a telephone survey of 400 SMEs conducted (before the “credit crunch”) by the Barclays Bank small business research team were analysed. The survey was based on a large stratified random sample drawn from the Bank's entire SME population. Findings – It was found that education made little difference to sources of finance, except that those educated to A‐level more frequently used friends and family and remortgaged their homes. However, graduates had the least difficulties raising finance. Though statistically insignificant, women respondents found it easier to raise finance than men. The survey confirmed that – and this finding was statistically significant – ethnic minority businesses, particularly black owner‐managers, had the greatest problem raising finance and hence relied upon “bootstrapping” as a financing strategy. Practical implications – The study makes an important contribution to filling a research gap, given the critical need of policy‐makers to understand differentials between different types of owner‐managers. It brings new insights into its field – access to finance – and with respect, especially, to marginalised groups. Originality/value – The paper adopts a different approach than many prior studies, with a large sample and robust analysis, to explore a critical need‐to‐know area in a new way – both for policy‐makers and academics in the field of SME finance