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تسجيل مستخدم جديدA Sensitive Identification of Warm Debris Disks in the Solar Neighborhood Through Precise Calibration of Saturated WISE Photometry
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Rahul I. Patel
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We present a sensitive search for WISE W3 (12um) and W4 (22um) excesses from warm optically thin dust around Hipparcos main sequence stars within 75pc from the Sun. We use contemporaneously measured photometry from WISE, remove sources of contamination, and derive and apply corrections to saturated fluxes to attain optimal sensitivity to >10um excesses. We use data from the WISE All-Sky Survey Catalog rather than the AllWISE release, because we find that its saturated photometry is better behaved, allowing us to detect small excesses even around saturated stars in WISE. Our new discoveries increase by 45% the number of stars with warm dusty excesses and expand the number of known debris disks (with excess at any wavelength) within 75pc by 29%. We identify 220 Hipparcos debris disk-host stars, 108 of which are new detections at any wavelength. We present the first measurement of a 12um and/or 22um excess for 10 stars with previously known cold (50-100 K) disks. We also find five new stars with small but significant W3 excesses, adding to the small population of known exozodi, and we detect evidence for a W2 excess around HIP96562 (F2V), indicative of tenuous hot (780 K) dust. As a result of our WISE study, the number of debris disks with known 10-30um excesses within 75pc (379) has now surpassed the number of disks with known >30um excesses (289, with 171 in common), even if the latter have been found to have a higher occurrence rate in unbiased samples.
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Using data from the WISE All-Sky Survey, we have found >100 new infrared excess sources around main-sequence Hipparcos stars within 75pc. Our empirical calibration of WISE photospheric colors and removal of non-trivial false-positive sources are resp
onsible for the high confidence (>99.5%) of detections, while our corrections to saturated W1 (3.4um) and W2 (4.6um) photometry have for the first time allowed us to search for new infrared excess sources around bright field stars in WISE. The careful calibration and filtering of the WISE data have allowed us to probe excess fluxes down to roughly 8% of the photospheric emission at 22um around saturated stars in WISE. We expect that the increased sensitivity of our survey will not only aid in understanding the evolution of debris disks, but will also benefit future studies using WISE.
Debris disks around stars are considered as components of planetary systems. Constrain the dust properties of these disks can give crucial information to formation and evolution of planetary systems. As an all-sky survey, textit{InfRared Astronomical
Satellite} (iras) gave great contribution to the debris disk searching which discovered the first debris disk host star (Vega). The iras-detected debris disk sample published by Rhee citep{rhe07} contains 146 stars with detailed information of dust properties. While the dust properties of 45 of them still can not be determined due to the limitations with the iras database (have iras detection at 60 $mu$m only). Therefore, using more sensitivity data of textit{Wide-field Infrared Survey Explorer} (wise), we can better characterize the sample stars: For the stars with iras detection at 60 $mu$m only, we refit the excessive flux densities and obtain the dust temperatures and fractional luminosities; While for the remaining stars with multi-bands iras detections, the dust properties are revised which show that the dust temperatures were over estimated in high temperatures band before. Moreover, we identify 17 stars with excesses at the wise 22 $mu$m which have smaller distribution of distance from Earth and higher fractional luminosities than the other stars without mid-infrared excess emission. Among them, 15 stars can be found in previous works.
(Abridged) Debris disks trace remnant reservoirs of leftover planetesimals in planetary systems. A handful of warm debris disks have been discovered in the last years, where emission in excess starts in the mid-infrared. An interesting subset within
these warm debris disks are those where emission features are detected in mid-IR spectra, which points towards the presence of warm micron-sized dust grains. Given the ages of the host stars, the presence of these grains is puzzling, and questions their origin and survival in time. This study focuses on determining the mineralogy of the dust around 7 debris disks with evidence for warm dust, based on Spitzer/IRS spectroscopic data, in order to provide new insights into the origin of the dust grains. We present a new radiative transfer code dedicated to SED modeling of optically thin disks. We make use of this code on the SEDs of seven warm debris disks, in combination with recent laboratory experiments on dust optical properties. We find that most, if not all, debris disks in our sample are experiencing a transient phase, suggesting a production of small dust grains on relatively short timescales. From a mineralogical point of view, we find that enstatite grains have small abundances compared to crystalline olivine grains. The main result of our study is that we find evidences for Fe-rich crystalline olivine grains (Fe / [Mg + Fe] ~ 0.2) for several debris disks. This finding contrasts with studies of gas-rich protoplanetary disks. The presence of Fe-rich olivine grains, and the overall differences between the mineralogy of dust in Class II disks compared to debris disks suggest that the transient crystalline dust is of a new generation. We discuss possible crystallization routes to explain our results, and comment on the mechanisms that may be responsible for the production of small dust grains.
We used chromospheric activity to determine the ages of 2,820 field stars.. We searched these stars for excess emission at 22 um with the Wide-Field Infrared Survey Explorer. Such excess emission is indicative of a dusty debris disk around a star. We
investigated how disk incidence trends with various stellar parameters, and how these parameters evolve with time. We found 22 um excesses around 98 stars (a detection rate of 3.5%). Seventy-four of these 98 excess sources are presented here for the first time. We also measured the abundance of lithium in 8 dusty stars in order to test our stellar age estimates.
In an earlier study we reported nearly 100 previously unknown dusty debris disks around Hipparcos main sequence stars within 75 pc by selecting stars with excesses in individual WISE colors. Here, we further scrutinize the Hipparcos 75 pc sample to (
1) gain sensitivity to previously undetected, fainter mid-IR excesses and (2) to remove spurious excesses contaminated by previously unidentified blended sources. We improve upon our previous method by adopting a more accurate measure of the confidence threshold for excess detection, and by adding an optimally-weighted color average that incorporates all shorter-wavelength WISE photometry, rather than using only individual WISE colors. The latter is equivalent to spectral energy distribution fitting, but only over WISE band passes. In addition, we leverage the higher resolution WISE images available through the unWISE.me image service to identify contaminated WISE excesses based on photocenter offsets among the W3- and W4-band images. Altogether, we identify 19 previously unreported candidate debris disks. Combined with the results from our earlier study, we have found a total of 107 new debris disks around 75 pc Hipparcos main sequence stars using precisely calibrated WISE photometry. This expands the 75 pc debris disk sample by 22% around Hipparcos main-sequence stars and by 20% overall (including non-main sequence and non-Hipparcos stars).
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