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We present the effective temperatures (Teff), metallicities, and colours in Sloan Digital Sky Survey (SDSS), Two Micron All Sky Survey, andWide-field Infrared Survey Explorer filters, of a sample of 3834 late-K and early-M dwarfs selected from the SDSS Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectroscopic survey ASPCAP (APOGEE Stellar Parameters and Chemical Abundances Pipeline) catalogue. We confirm that ASPCAP Teff values between 3550 < Teff < 4200 K are accurate to ~100 K compared to interferometric Teff values. In that same Teff range, ASPCAP metallicities are accurate to 0.18 dex between -1.0 <[M/H]<0.2. For these cool dwarfs, nearly every colour is sensitive to both Teff and metallicity. Notably, we find that g - r is not a good indicator of metallicity for near-solar metallicity early-M dwarfs. We confirm that J - KS colour is strongly dependent on metallicity, and find that W1 - W2 colour is a promising metallicity indicator. Comparison of the late-K and early-M dwarf colours, metallicities, and Teff to those from three different model grids shows reasonable agreement in r - z and J - KS colours, but poor agreement in u - g, g - r, and W1 - W2. Comparison of the metallicities of the KM dwarf sample to those from previous colour-metallicity relations reveals a lack of consensus in photometric metallicity indicators for late-K and early-M dwarfs. We also present empirical relations for Teff as a function of r - z colour combined with either [M/H] or W1 - W2 colour, and for [M/H] as a function of r - z and W1 - W2 colour. These relations yield Teff to ~100 K and [M/H] to ~0.18 dex precision with colours alone, for Teff in the range of 3550-4200 K and [M/H] in the range of -0.5-0.2. [ABSTRACT FROM AUTHOR]

As a major component of the LAMOST Galactic surveys, the LAMOST Spectroscopic Survey of the Galactic Anticentre (LSS-GAC) aims to survey a significant volume of the Galactic thin/thick discs and halo for a contiguous sky area of over 3400 deg2 centred on the Galactic anticentre (|b| ≤ 30°, 150 ≤ l ≤ 210°), and obtain λλ3700–9000 low-resolution (R ∼ 1800) spectra for a statistically complete sample of ∼3 M stars of all colours down to a limiting magnitude of r ∼ 17.8 mag (to 18.5 mag for limited fields). Together with Gaia, the LSS-GAC will yield a unique data set to advance our understanding of the structure and assemblage history of the Galaxy, in particular its disc(s). In addition to the main survey, the LSS-GAC will also target hundreds of thousands objects in the vicinity fields of M 31 and M 33 and survey a significant fraction (over a million) of randomly selected very bright stars (r ≤ 14 mag) in the Northern hemisphere. During the Pilot and the first year Regular Surveys of LAMOST, a total of 1042 586 [750 867] spectra of a signal-to-noise ratio S/N(7450 Å) ≥ 10 [S/N(4650 Å) ≥ 10] have been collected. In this paper, we present a detailed description of the target selection algorithm, survey design, observations and the first data release of value-added catalogues (including radial velocities, effective temperatures, surface gravities, metallicities, values of interstellar extinction, distances, proper motions and orbital parameters) of the LSS-GAC. [ABSTRACT FROM PUBLISHER]

We present 17 high-precision light curves of five transits of the planet Qatar-2 b, obtained from four defocused 2 m-class telescopes. Three of the transits were observed simultaneously in the Sloan g′r′i′z′ passbands using the seven-beam Gamma Ray Burst Optical and Near-Infrared Detector imager on the MPG/ESO 2.2-m telescope. A fourth was observed simultaneously in Gunn grz using the Centro Astronómico Hispano Alemán 2.2-m telescope with Bonn University Simultaneous Camera, and in r using the Cassini 1.52-m telescope. Every light curve shows small anomalies due to the passage of the planetary shadow over a cool spot on the surface of the host star. We fit the light curves with the prism+gemc model to obtain the photometric parameters of the system and the position, size and contrast of each spot. We use these photometric parameters and published spectroscopic measurements to obtain the physical properties of the system to high precision, finding a larger radius and lower density for both star and planet than previously thought. By tracking the change in position of one star-spot between two transit observations, we measure the orbital obliquity of Qatar-2 b to be λ = 4 $_{.}^{\circ}$3 ± 4 $_{.}^{\circ}$5, strongly indicating an alignment of the stellar spin with the orbit of the planet. We calculate the rotation period and velocity of the cool host star to be 11.5 ± 0.2 d and 3.28 ± 0.04 km s−1 at a colatitude of 74°. We assemble the planet's transmission spectrum over the 386–976 nm wavelength range and search for variations of the measured radius of Qatar-2 b as a function of wavelength. Our analysis highlights a possible H2/He Rayleigh scattering in the blue. [ABSTRACT FROM PUBLISHER]

We study the relationship between galaxy colour, stellar mass and local galaxy density in a deep near-infrared imaging survey up to a redshift of using the GOODS (Great Observatories Origins Deep Survey) NICMOS (Near Infrared Camera and Multi-Object Spectrometer) Survey (GNS). The GNS is a deep near-infrared Hubble Space Telescope survey imaging a total of 45 arcmin of the GOODS fields, reaching a stellar mass completeness limit of at . Using these data, we measure galaxy local densities based on galaxy counts within a fixed aperture, as well as the distance to the third, fifth and seventh nearest neighbour. We compare the average rest-frame colour and fraction of blue galaxies in different local densities and at different stellar masses. We find a strong correlation between colour and stellar mass at all redshifts up to . Massive red galaxies are already in place at at the expected location of the red sequence in the colour-magnitude diagram, although they are star forming. We do not find a strong correlation between colour and local density; however, there may be evidence that the highest overdensities are populated by a higher fraction of blue galaxies than average or underdense areas. This could be indicating that the colour-density relation at high redshift is reversed with respect to lower redshifts (), where higher densities are found to have lower blue fractions. Our data suggest that the possible higher blue fraction at extreme overdensities might be due to a lack of massive red galaxies at the highest local densities. [ABSTRACT FROM AUTHOR]

Careful analyses of photometric and star count data available for the nine putative young clusters identified by Camargo et al. at high Galactic latitudes reveal that none of the groups contain early-type stars, and most are not significant density enhancements above the field level. Two-Micron All-Sky Survey (2MASS) colours for stars in the groups match those of unreddened late-type dwarfs and giants, as expected for the contamination by (mostly) thin disc objects. A simulation of one such field using only typical high-latitude foreground stars yields a colour-magnitude diagram that is very similar to those constructed by Camargo et al. as evidence for their young groups as well as the means of deriving their reddenings and distances. Although some of the fields are coincident with clusters of galaxies, one must conclude that there is no evidence that the putative clusters are extremely young stellar groups. [ABSTRACT FROM AUTHOR]

The article presents a study which monitors the open cluster IC4651. Methods and instruments used in the observations of the long period variables (LPVs) in stellar clusters conducted at Mount Stromlo in Australia. Results of the study and several charts are presented showing the light curves of the four variables detected and 2MASS colour-magnitude diagram for sources 10 arcminutes in IC4651.

Long-term JHKLM photometric measurements of the oxygen Mira variables RU Her and RS Vir are presented. Variations of the brightnesses and colors of these stars over the observation period are analyzed, and master light curves and color indices of these stars are derived. A linear trend was present in the mean infrared brightness of RS Vir on a time scale of ∼6000 day, possibly related to changes in the dust shell of the Mira. The results of model calculations of spherically symmetric dust shells of stars based on mean-flux data supplemented by observations from the IRAS and AKARI satellites in the intermediate- and far-IR are presented. The visual optical depth of the dust shell of RU Her, which has a temperature at its inner boundary T = 590 K, is quite low: τ = 0.33. The dust shell of RS Vir is much cooler ( T = 410 K), and has τ = 0.77. The estimated mass-loss rate of RU Her is 6.2 × 10 M/yr, while the mass-loss rate of RS Vir is 7.1 × 10 M/yr. [ABSTRACT FROM AUTHOR]

We present constraints on Type Ia supernovae (SNe Ia) progenitors through an analysis of the environments found at the explosion sites of 102 events within star-forming host galaxies. Hα and Galaxy Evolution Explorer near-ultraviolet (UV) images are used to trace on-going and recent star formation (SF), while broad-band B, R, J, K imaging is also analysed. Using pixel statistics we find that SNe Ia show the lowest degree of association with Hα emission of all supernova (SN) types. It is also found that they do not trace near-UV emission. As the latter traces SF on time-scales less than 100 Myr, this rules out any extreme ‘prompt’ delay times as the dominant progenitor channel of SNe Ia. SNe Ia best trace the B-band light distribution of their host galaxies. This implies that the population within star-forming galaxies is dominated by relatively young progenitors. Splitting SNe by their (B − V) colours at maximum light, ‘redder’ events show a higher degree of association with H ii regions and are found more centrally within hosts. We discuss possible explanations of this result in terms of line-of-sight extinction and progenitor effects. No evidence for correlations between SN stretch and environment properties is observed. [ABSTRACT FROM PUBLISHER]

Stellar evolutionary models simulate well binary stars when individual stellar mass and system metallicity are known. The mass can be derived directly from observations only in the case of multiple stellar systems, mainly binaries. Yet, the number of such stars for which accurate stellar masses are available is rather small. The main goal of this project is to provide realistic mass estimates for a homogeneous sample of about a thousand FGK single stars, using four different methods and techniques. We present the masses inferred according to each one of these methods as well as a final mass estimate consisting in the median of the four mass estimates. The procedures evaluated here include the use of stellar evolutionary models, mass–luminosity relation and surface gravity spectroscopic observations. By combining the results obtained with different methods, we determine the best mass value for each individual star, as well as the associated error budget. Our results confirm the expected consistency between the different mass estimation methods. None the less, for masses above 1.2 M⊙, the spectroscopic surface gravities seem to overestimate the mass. This result may be a consequence of the spectroscopic surface gravities used in this analysis. Nevertheless, this problem is minimized by the fact that we have several approaches available for deriving stellar masses. Moreover, we suggest an empirical procedure to overcome this issue. [ABSTRACT FROM AUTHOR]

We report the discovery in the Rossi X-Ray Timing Explorer data of GRS 1915+105 of a second quasi-periodic oscillation at 34 Hz, simultaneous with that observed at 68 Hz in the same observation. The data corresponded to those observations from 2003 where the 68 Hz oscillation was very strong. The significance of the detection is 4.2σ. These observations correspond to a very specific position in the colour–colour diagram for GRS 1915+105, corresponding to a harder spectrum compared to those where a 41 Hz oscillation was discovered. We discuss the possible implications of the new pair of frequencies comparing them with the existing theoretical models. [ABSTRACT FROM AUTHOR]

PSR J1811−1736 (Ps = 104 ms) is an old (∼1.89 Gyr) binary pulsar (Porb = 18.8 d) in a highly eccentric orbit (e = 0.828) with an unidentified companion. Interestingly, the pulsar timing solution yields an estimated companion mass of 0.93 M⊙ ≤ MC ≤ 1.5 M⊙, compatible with that of a neutron star. As such, it is possible that PSR J1811−1736 is a double neutron star (DNS) system, one of the very few discovered so far. This scenario can be investigated through deep optical/infrared (IR) observations. We used J- H- and K-band images, obtained as part of the UK Infrared Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS), and available in the recent Data Release 9 Plus, to search for the undetected companion of the PSR J1811−1736 binary pulsar. We detected a possible companion star to PSR J1811−1736 within the 3σ radio position uncertainty (1.32 arcsec), with magnitudes J = 18.61 ± 0.07, H = 16.65 ± 0.03 and K = 15.46 ± 0.02. The star colours are consistent with either a main sequence (MS) star close to the turn-off or a lower red giant branch (RGB) star, at a pulsar distance of ∼5.5 kpc and with a reddening of E(B − V) ∼ 4.9. The star mass and radius would be compatible with the constraints on the masses and orbital inclination of the binary system inferred from the mass function and with the lack of radio eclipses near superior conjunction. Thus, it is possible that it is the companion to PSR J1811−1736. However, based on the star density in the field, we estimated quite a large chance coincidence probability of ∼0.27 between the pulsar and the star, which makes the association unlikely. No other star is detected within the 3σ pulsar radio position down to J ∼ 20.5, H ∼ 19.4 and K ∼ 18.6, which allows us to rule out a MS companion star earlier than a mid-to-late M spectral type. [ABSTRACT FROM PUBLISHER]

ABSTRACT In the current models of galaxy formation and evolution, AGN feedback is crucial to reproduce galaxy luminosity function, colour-magnitude relation and M•-σ relation. However, whether AGN feedback can indeed expel and heat up significant amount of cool molecular gas and consequently quench star formation is yet to be demonstrated observationally. Only in four cases so far (Cen A, NGC 3801, NGC 6764 and Mrk 6), X-ray observations have found evidences of jet-driven shocks heating the ISM. We chose the least explored galaxy NGC 3801, and present the first ultraviolet imaging and stellar population analysis of this galaxy from GALEX data. We find this merger-remnant early-type galaxy to have an intriguing spiral wisp of young star-forming regions (age ranging from 100 to 500 Myr). Taking clues from dust/PAH, H i and CO emission images, we interpret NGC 3801 to have a kinematically decoupled core or an extremely warped gas disc. From the HST data, we also show evidence of ionized gas outflow similar to that observed in H i and molecular gas (CO) data, which may have caused the decline of star formation leading to the red optical colour of the galaxy. However, from these panchromatic data, we interpret that the expanding shock shells from the young (∼2.4 Myr) radio jets are yet to reach the outer gaseous regions of the galaxy. It seems we observe this galaxy at a rare stage of its evolutionary sequence where post-merger star formation has already declined and new powerful jet feedback is about to affect the gaseous star-forming outer disc within the next 10 Myr, to further transform it into a red-and-dead early-type galaxy. [ABSTRACT FROM AUTHOR]

ABSTRACT The stellar haloes of galaxies can currently be studied either through observations of resolved halo stars or through surface photometry. Curiously, the two methods appear to give conflicting results, as a number of surface photometry measurements have revealed integrated colours that are too red to be reconciled with the halo properties inferred from the study of resolved stars. Several explanations for this anomaly have been proposed - including dust photoluminescence, extinction of extragalactic background light and a bottom-heavy stellar initial mass function. A decisive test is, however, still lacking. Here, we explain how observations of the halo of a nearby galaxy, involving a combination of both surface photometry and bright star counts, can be used to distinguish between the proposed explanations. We derive the observational requirements for this endeavour and find that star counts in filters VI and surface photometry in filters VIJ appear to be the optimal strategy. Since the required halo star counts are already available for many nearby galaxies, the most challenging part of this test is likely to be the optical surface photometry, which requires several nights of exposure time on a 4-8 m telescope, and the near-infrared surface photometry, which is most readily carried out using the upcoming James Webb Space Telescope. [ABSTRACT FROM AUTHOR]

ABSTRACT Using two different spectrographs, High Accuracy Radial velocity Planet Search (HARPS) (European Southern Observatory) and SOPHIE (Observatoire de Haute Provence), we have measured v sin i for a sample of dK5 stars. These are the first measurements of v sin i for most of the stars studied here. We measured v sin i to an accuracy of 0.3 km s−1 and a detection limit of about 0.5-1 km s−1. All our targets have similar ( R − I)c colour. This is an advantage and facilitates the determination of the narrowest line profiles for v sin i ∼ 0. In our total sample, we detected rotation for 22 stars (three dK5e and 19 dK5 stars), and we did not detect rotation in a further 22 stars. This result shows that there are many dK5 slow rotators, and many more than for dM1 stars. We also report on a newly discovered dK5e star, McC 522, which is also the fastest rotator in our sample. We determine radii and effective temperatures for all our target stars. The effective temperatures were derived using the ( R − I)c colour and empirical far-red colour-effective temperature correlations, and the radii were derived from the standard formulae relating Mbol, bolometric correction and Teff. We find that the distribution of P/sin i (the projected rotation period) is rather homogeneous, i.e. the distribution of the 22 detected stars as a function of P/sin i is approximately flat and does not show any maximum, unlike for dM1 stars, a close spectral type. We find that the distribution in v sin i is bimodal, as in dM1 stars, with fast dK5e rotators and slower dK5 rotators. [ABSTRACT FROM AUTHOR]

We present the discovery of only the second radio-selected z ~ 6 quasar. We identified SDSS J222843.54+011032.2 (z = 5.95) by matching the optical detections of the deep Sloan Digital Sky Survey Stripe 82 with their radio counterparts in the Stripe 82 Very Large Array Survey. We also matched the Canadian-France-Hawaiian Telescope Legacy Survey Wide with the Faint Images of the Radio Sky at Twenty cm survey but have yet to find any z ~ 6 quasars in this survey area. The discovered quasar is optically faint, z = 22.3 and M1450 ~ -24.5, but radio bright, with a flux density of f1.4GHz,peak = 0.31 mJy and a radio loudness of R ~ 1100 (where R - f5GHz/f2500). The i - z color of the discovered quasar places it outside the color selection criteria for existing optical surveys. We conclude by discussing the need for deeper wide-area radio surveys in the context of high-redshift quasars. [ABSTRACT FROM AUTHOR]

The potential of combining Adaptive Optics (AO) and Lucky Imaging (LI) to achieve high-precision astrometry and differential photometry in the optical is investigated by conducting observations of the close 0.1 arcsec brown dwarf binary GJ569Bab. We took 50 000 -band images with our LI instrument FastCam attached to NAOMI, the 4.2-m William Herschel Telescope (WHT) AO facility. In order to extract the most of the astrometry and photometry of the GJ569Bab system we have resorted to a PSF fitting technique using the primary star GJ569A as a suitable PSF reference which exhibits an -band magnitude of . The AO+LI observations at WHT were able to resolve the binary system GJ569Bab located at arcsec from GJ569A. We measure a separation of mas and -band magnitudes of and and colours of 2.72 0.08 and 2.83 0.08 for the Ba and Bb components, respectively. Our study rules out the presence of any other companion to GJ569A down to magnitude at distances larger than 1 arcsec. The colours measured are consistent with M8.5-M9 spectral types for the Ba and Bb components. The available dynamical, photometric and spectroscopic data are consistent with a binary system with Ba being slightly (10-20 per cent) more massive than Bb. We obtain new orbital parameters which are in good agreement with those in the literature. [ABSTRACT FROM AUTHOR]

Star-galaxy classification is one of the most fundamental data-processing tasks in survey astronomy and a critical starting point for the scientific exploitation of survey data. Star-galaxy classification for bright sources can be done with almost complete reliability, but for the numerous sources close to a survey's detection limit each image encodes only limited morphological information about the source. In this regime, from which many of the new scientific discoveries are likely to come, it is vital to utilize all the available information about a source, both from multiple measurements and from prior knowledge about the star and galaxy populations. This also makes it clear that it is more useful and realistic to provide classification probabilities than decisive classifications. All these desiderata can be met by adopting a Bayesian approach to star-galaxy classification, and we develop a very general formalism for doing so. An immediate implication of applying Bayes's theorem to this problem is that it is formally impossible to combine morphological measurements in different bands without using colour information as well; however, we develop several approximations that disregard colour information as much as possible. The resultant scheme is applied to data from the UKIRT Infrared Deep Sky Survey (UKIDSS) and tested by comparing the results to deep Sloan Digital Sky Survey (SDSS) Stripe 82 measurements of the same sources. The Bayesian classification probabilities obtained from the UKIDSS data agree well with the deep SDSS classifications both overall (a mismatch rate of 0.022 compared to 0.044 for the UKIDSS pipeline classifier) and close to the UKIDSS detection limit (a mismatch rate of 0.068 compared to 0.075 for the UKIDSS pipeline classifier). The Bayesian formalism developed here can be applied to improve the reliability of any star-galaxy classification schemes based on the measured values of morphology statistics alone. [ABSTRACT FROM AUTHOR]

In order to investigate factors necessary for reproducing actual star images in a planetarium, for this article, the authors conducted a psychophysical experiment using projection stimuli generated by changing three parameters of the stars: color, luminance, and size. A reference projection pattern was designed to be faithful to the actual starry sky perceptually (rather than physically) by an experienced group with abundant astronomical observation experience. A reproduction system was constructed to project ten types of star image patterns to a planetarium dome using different parameters. Then, evaluation experiments with twenty observers were conducted. The results of the experiment indicate that the intensity of the stars was sensitive to the fidelity of the reproduction, and in either case of change (whether the star was bright or dark compared to the reference pattern), the result was a loss of fidelity. In addition, although the fidelity was improved when the size of the projected star was small, for stars that were projected larger than the reference pattern, the result was remarkably negative. As for differences in color, the evaluation results suggested that the tolerance to loss of fidelity was wide. [ABSTRACT FROM AUTHOR]

We present a UBVI CCD photometric study of two open star clusters Ruprecht 25 and Czernik 6 using the data taken with 104-cm Sampurnanand telescope, ARIES, Nainital, India. The optical CCD data for these clusters are obtained for the first time. The clusters radii are found to be 2′.4 and 1′.5. Using two colour ( U − B ) versus ( B − V ) diagram we have estimated the reddening as E ( B − V ) = 0.55 ± 0.05 mag for Ruprecht 25 and 0.48 ± 0.05 mag for Czernik 6, while the corresponding distances are 5.8 ± 0.5 and 5.0 ± 0.3 kpc. Ages of 800 ± 80 Myr for Ruprecht 25 and 40 ± 10 Myr for Czernik 6 are determined using the stellar isochrones of metallicity Z = 0.019 . We have also determined the relaxation time for the clusters Ruprecht 25 and Czernik 6. Our analysis indicates that both clusters are dynamically relaxed. This may be due to the dynamical evolution or imprint of star formation itself or both. [ABSTRACT FROM AUTHOR]

The stellar content in and around Sh2-311 region have been studied using the deep optical observations as well as near-infrared (NIR) data from 2MASS. The region contains three clusters, viz. NGC 2467, Haffner 18 and Haffner 19. We have made an attempt to distinguish the stellar content of these individual regions as well as to re-determine their fundamental parameters such as distance, reddening, age, onto the basis of a new and more extended optical and infrared photometric data set. NGC 2467 and Haffner 19 are found to be located in the Perseus arm at the distances of 5.0 ± 0.4 kpc and 5.7 ± 0.4 kpc, respectively, whereas Haffner 18 is located at the distance of 11.2 ± 1.0 kpc. The clusters NGC 2467 and Haffner 19 might have formed from the same molecular cloud, whereas the cluster Haffner 18 is located in the outer galactic arm, i.e. the Norma–Cygnus arm. We identify 8 class II young stellar objects (YSOs) using the NIR ( J - H ) / ( H - K ) two colour diagram. We have estimated the age and mass of the YSOs identified in the present work and those by Snider et al. (2009) using the V / ( V - I ) colour-magnitude diagram. The estimated ages and mass range of the majority of the YSOs are ≲ 1 Myr and ∼0.4–3.5 M ⊙ , respectively, indicating that these sources could be T-Tauri stars or their siblings. Spatial distribution of the YSOs shows that some of the YSOs are distributed around the H ii region Sh2-311, suggesting a triggered star formation at its periphery. [ABSTRACT FROM AUTHOR]

Aims.We present a technique to measure lightcurves of time-variable point sources on a spatially structured background from imaging data. The technique was developed to measure lightcurves of SNLS supernovae in order to infer their distances. This photometry technique performs simultaneous point spread function (PSF) photometry at the same sky position on an image series. Methods. We describe two implementations of the method: one that resamples images before measuring fluxes, and one which does not. In both instances, we sketch the key algorithms involved and present the validation using semi-artificial sources introduced in real images in order to assess the accuracy of the supernova flux measurements relative to that of surrounding stars. We describe the methods required to anchor these PSF fluxes to calibrated aperture catalogs, in order to derive SN magnitudes. Results. We find a marginally significant bias of 2 mmag of the after-resampling method, and no bias at the mmag accuracy for the non-resampling method. Given surrounding star magnitudes, we determine the systematic uncertainty of SN magnitudes to be less than 1.5 mmag, which represents about one third of the current photometric calibration uncertainty affecting SN measurements. The SN photometry delivers several by-products: bright star PSF flux measurements which have a repeatability of about 0.6%, as for aperture measurements; we measure relative astrometric positions with a noise floor of 2.4 mas for a single-image bright star measurement; we show that in all bands of the MegaCam instrument, stars exhibit a profile linearly broadening with flux by about 0.5% over the whole brightness range. [ABSTRACT FROM AUTHOR]

Specifications of a new Apogee Alta U47 CCD camera mounted at the Kyiv meridian axial circle (MAC) are presented. The camera is based on the 1024 × 1024 pxl e2v CCD47-10 with pixel sizes of 13 × 13 μm. Observations are carried out in the scan-drift mode with an effective exposure time of 77 s for equatorial stars. The MAC photometric system answers the standard Johnson V band, the MAC limiting magnitude V is 17. The test MAC observations of 2009 give positional accuracy and V magnitude errors equal to approximately 0.1″ and 0.09, respectively, for Tycho-2 stars. The telescope is used for observations of equatorial stars with the purpose of detecting their positions, proper motion, and brightness. [ABSTRACT FROM AUTHOR]

The high-precision data available from the Kepler satellite allows us to study the complex outer convective envelopes of solar-type stars. We use a seismic diagnostic, specialized for investigating the outer layers of solar-type stars, to infer the impact of the ionization processes on the oscillation spectrum, for a sample of Kepler stars. These stars, of spectral type F, cover all of the observational seismic domain of the acoustic oscillation spectrum in solar-type stars. They also cover the range between a cool F-dwarf (∼6000 K) and a hotter F-star (∼6400 K). Our study reveals the existence of two relevant ionization regions. One of these regions, which is located closer to the surface of the star, is commonly associated with the second ionization of helium, although other chemical species also contribute to ionization. The second region, located deeper in the envelope, is linked with the ionization of heavy elements. Specifically, in this study, we analyze the elements carbon, nitrogen, oxygen, neon, and iron. Both regions can be related to the K electronic shell. We show that, while for cooler stars like the Sun, the influence of this second region on the oscillation frequencies is small; in hotter stars, its influence becomes comparable to the influence of the region of the second ionization of helium. This can guide us in the study of the outer layers of F-stars, specifically with the understanding of phenomena related to rotation and magnetic activity in these stars. [ABSTRACT FROM AUTHOR]