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PDF, on the Incidence of Wise Infrared Excess Among Solar The Astrophysical Journal, 837:15 (11pp), 2017 March 1 doi:10.3847/1538-4357/837/1/15 © 2017. The American Astronomical Society. All rights reserved. On the Incidence of Wise Infrared Excess Among Solar Analog, Twin, and Sibling Stars A. D. Da Costa1, B. L. Canto Martins1, I. C. Leão2, J. E. Lima Jr1, D. Freire da Silva1, D. B. de Freitas3, and J. R. De Medeiros1 1 Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Campus Universitário, Natal, RN, 59072-970, Brazil; dgerson@fisica.ufrn.br 2 European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching, Germany 3 Departamento de Física, Universidade Federal do Ceará, Caixa Postal 6030, Campus do Pici, 60455-900, Fortaleza, Ceará, Brazil Received 2016 April 25; revised 2016 November 3; accepted 2016 November 6; published 2017 February 27 Abstract This study presents a search for infrared (IR) excess in the 3.4, 4.6, 12, and 22 μm bands in a sample of 216 targets, composed of solar sibling, twin, and analog stars observed by the Wide-field Infrared Survey Explorer (WISE) mission. In general, an IR excess suggests the existence of warm dust around a star. We detected 12 μm and/or 22 μm excesses at the 3σ level of confidence in five solar analog stars, corresponding to a frequency of 4.1% of the entire sample of solar analogs analyzed, and in one out of 29 solar sibling candidates, confirming previous studies. The estimation of the dust properties shows that the sources with IR excesses possess circumstellar material with temperatures that, within the uncertainties, are similar to that of the material found in the asteroid belt in our solar system. No photospheric flux excess was identified at the W1 (3.4 μm) and W2 (4.6 μm) WISE bands, indicating that, in the majority of stars of the present sample, no detectable dust is generated. Interestingly, among the 60 solar twin stars analyzed in this work, no WISE photospheric flux excess was detected. However, a null-detection excess does not necessarily indicate the absence of dust around a star because different causes, including dynamic processes and instrument limitations, can mask its presence. Key words: circumstellar matter – infrared: stars – stars: individual (HD 86087) – stars: solar-type Supporting material: extended figure, machine-readable table 1. Introduction 2006; Wyatt et al. 2007; Meyer et al. 2008; Trilling et al. 2008; Urban et al. 2012; Montesinos et al. 2016). For instance, about The search for stellar infrared (IR) excesses may offer 20% of the nearby Sun-like stars in the referred spectral range important constraints for our understanding of the nature and host dusty disks above the current detection limits (Habing evolution of circumstellar dust disks, which are the most clear et al. 2001; Trilling et al. 2008; Eiroa et al. 2013; Gáspár et al. sign of other planetary systems. These structures may be 2013). Among the stars with detected disks, approximately indicative of perturbing forces, revealing the presence of 10% have ages from 10 Myr to 1 Gyr (Bryden et al. 2006; Chen planets that would otherwise remain undetected, or of other ) fl et al. 2006; Meyer et al. 2008 , with a clear disappearance of in uences, including the presence of remnant gas, that may disks among stars older than 300–400 Myr (Habing et al. 1999; sculpt the starlight-scattering materials in these systems into ) ( ) ( Wyatt 2008 . More recently, Sierchio et al. 2014 have shown ring-like morphologies e.g., Aumann et al. 1984; Zuckerman that, among solar-type stars within the spectral type range F4 to & Song 2004; Chen et al. 2009, 2014; Lagrange et al. 2009; K2, about 13% of the stars younger than 5 Gyr have dust disks, Melis et al. 2013; Su & Rieke 2014; Vican & Schneider 2014; while stars most older than 5 Gyr do not. ) Meshkat et al. 2015 . For instance, in the solar system zodiacal The Wide-field Infrared Survey Explorer, WISE, (Wright cloud, Earth has cleared out a region in its vicinity as a result of et al. 2010), which made observations centered at wavelengths ( ) resonant tidal interactions Dermott et al. 1994 . The current of 3.4, 4.6, 12, and 22 μm (known as the W1, W2, W3, and W4 literature reports debris disks composed of belts of rocks and bands, respectively), offers a unique laboratory to search for dust around hundreds of solar-type stars (e.g., Aumann mid-IR excess in different stellar families. The 3.4–4.6 μm et al. 1984; Oudmaijer et al. 1992; Mannings & Barlow 1998; wavelength range is a good diagnostic of the presence of a Chen et al. 2006, 2014; Cruz-Saenz de Miera et al. 2014; Patel near-IR excess, whereas the 12–22 μm range is an indicator of et al. 2014), with some studies indicating that planets may be the presence of cooler dust. Indeed, these latter wavelengths are frequent in debris disks (e.g., Morales et al. 2011; Ballering very sensitive to thermal emission from sources at temperatures et al. 2013). Among these stars, a few dozen are also known to comparable to the Earth, approximately 300 K, and to our harbor planets (Lawler & Gladman 2012; Morales et al. 2012; asteroid belt and interior zodiacal cloud, approximately Bonsor et al. 2013). 150–250 K. For instance, Lawler & Gladman (2012) analyzed IR excess in main-sequence Sun-like stars is believed to the IR WISE behavior for hundreds of Kepler objects, including result from the production of collisional dust during the final stars with confirmed planets and stars with planet candidates, stages of planet formation, at least for relatively young stars, or and they identified eight stars with mid-IR excesses. Morales produced around older stars as long as dust is liberated in et al. (2012) performed an analysis for a sample composed of higher-speed collisions (Wyatt 2008; Krivov 2010). The 591 stars with confirmed planets, listed in the Extrasolar Planet incidence of debris disks around main-sequence stars of Encyclopedia (Schneider et al. 2011), from which nine stars spectral types A, F, G, and K, based on the detection of IR revealed excess mid-IR emission. More recently, Cotten & excess, is reported by different authors (Habing et al. 2001; Song (2016) presented a large census of IR excess in main- Rieke et al. 2005; Bryden et al. 2006; Chen et al. 2006; Su et al. sequence stars, amounting to approximately 1750 nearby and 1 The Astrophysical Journal, 837:15 (11pp), 2017 March 1 Da Costa et al. bright stars, most of which were revealed for the first time by WISE observations. The primary aim of this study is to determine the incidence of mid-IR excess at wavelengths of 3.4, 4.6, 12, and 22 μm based on homogeneous procedures for analyses of the WISE observations for a stellar sample composed of 216 solar sibling, twin, and analog stars selected from the literature. Solar siblings refer to stars that were born simultaneously with the Sun. By definition, these stars must have a solar chemical composition because they essentially came from the same gas cloud and are, consequently, the age of the Sun. However, solar siblings do not need to present physical parameters, such as effective temperature, mass, luminosity, surface gravity, or rotation, similar to those of the Sun. Solar twins refer to stars with high-resolution, high signal-to-noise ratio (S/N) spectra that are identical to the spectrum of the Sun, regardless of their origin (e.g., Cayrel de Strobel 1996; Porto de Mello & da Silva 1997; Melendez & Ramírez 2007; Ramírez et al. 2011). Solar Figure 1. Distribution of metallicity for the 206 Sun-like stars analyzed in this analogs refer to those stars that are spectroscopically similar to work. The canonical solar value is presented by the red dashed line. the Sun and that are known to have stellar properties close to solar values (e.g., Cayrel de Strobel 1996). the J, H, and Ksbands, from 2MASS. Nevertheless, for our The most straightforward approach for this study is to relate study, we cross-correlated the selected sample by using the properties of debris disks around the referred stars to 2MASS coordinates with the WISE all-sky data catalog, identifying regions similar in temperature to our solar system. considering only those WISE sources located within a 2 We revisit the search for the incidence of debris disks in 216 arcsecond radius for which the S/N is larger than 3 in all WISE main-sequence stars of our sample, some of which have IR bands, excluding stars with photometry corresponding to upper excess already reported in the literature, searching for WISE IR limits, as well as those with saturated fluxes. As a check of the excess. For a solid control on the reliability of the IR excess, level of saturation, for each source, we compared the WISE we applied a homogeneous diagnostic consisting of the magnitudes with the saturation thresholds defined by the ( ) identification of traces of IR excess in the color–color diagram, AllWISE data release Cutri et al. 2013 , according to which, the determination of the spectral energy distributions (SEDs), for sources with brightness larger than approximately 2.0, 1.5, and image inspections for each star. The remainder of this −3.0, and −4.0 mag in W1, W2, W3, and W4, respectively, the paper is organized as follows. Section 2 presents the data set reliability and completeness of WISE photometric measure- used in our study and discusses the methods applied to identify ments degrade because there are too few non-saturated pixels mid-IR excess and to visually inspect the WISE images.
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