اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدSpitzer/IRAC Photometry of the Eta Chameleontis Association
69
0
0.0
(
0
)
تأليف
S. T. Megeath
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We present IRAC 3.6, 4.5, 5.8 and 8 micron photometry for the 17 A, K and M type members of the Eta Chameleontis association. These data show infrared excesses toward six of the 15 K and M stars, indicating the presence of circumstellar disks around 40% of the stars with masses of 0.1-1 solar mass. The two A-stars show no infrared excesses. The excess emission around one of the stars is comparable to the median excess for classical T Tauri stars in the Taurus association; the remaining five show comparatively weak excess emission. Taking into account published Halpha spectroscopy that shows that five of the six stars are accreting, we argue that the disks with weak mid-infrared excesses are disks in which the inner disks have been largely depleted of small grains by grain growth, or, in one case, the small grains have settled to the midplane. This suggests that Eta Cha has a much higher fraction of disks caught in the act of transitioning into optically thin disks than that measured in younger clusters and associations.
قيم البحث
اقرأ أيضاً
We develop a new photometry algorithm that is optimized for $Spitzer$ time series in crowded fields and that is particularly adapted to faint and/or heavily blended targets. We apply this to the 170 targets from the 2015 $Spitzer$ microlensing campai
gn and present the results of three variants of this algorithm in an online catalog. We present detailed accounts of the application of this algorithm to two difficult cases, one very faint and the other very crowded. Several of $Spitzer$s instrumental characteristics that drive the specific features of this algorithm are shared by $Kepler$ and $WFIRST$, implying that these features may prove to be a useful starting point for algorithms designed for microlensing campaigns by these other missions.
We present the results of a morphological study performed to a sample of Ultracompact (UC) HII regions with Extended Emission (EE) using Spitzer--IRAC imagery and 3.6 cm VLA conf. D radio-continuum (RC) maps. Some examples of the comparison between m
aps and images are presented. Usually there is an IR point source counterpart to the peak(s) of RC emission, at the position of the UC source. We find that the predominant EE morphology is the cometary, and in most cases is coincident with IR emission at 8.0 $mu$m. Preliminary results of Spitzer--IRAC photometry of a sub-sample of 13 UC HII regions with EE based on GLIMPSE legacy data are also presented. Besides, individual IRAC photometry was performed to 19 UC sources within these 13 regions. We show that UC sources lie on specific locus, both in IRAC color-color and AM-product diagnostic diagrams. Counts of young stellar sources are presented for each region, and we conclude that a proportion of ~ 2%, ~10%, and ~88% of sources in the UC HII regions with EE are, in average, Class I, II, and III, respectively.
We present a new method employing machine learning techniques for measuring astrophysical features by correcting systematics in IRAC high precision photometry using Random Forests. The main systematic in IRAC light curve data is position changes due
to unavoidable telescope motions coupled with an intrapixel response function. We aim to use the large amount of publicly available calibration data for the single pixel used for this type of work (the sweet spot pixel) to make a fast, easy to use, accurate correction to science data. This correction on calibration data has the advantage of using an independent dataset instead of using the science data on itself, which has the disadvantage of including astrophysical variations. After focusing on feature engineering and hyperparameter optimization, we show that a boosted random forest model can reduce the data such that we measure the median of ten archival eclipse observations of XO-3b to be 1459 +- 200 parts per million. This is a comparable depth to the average of those in the literature done by seven different methods, however the spread in measurements is 30-100% larger than those literature values, depending on the reduction method. We also caution others attempting similar methods to check their results with the fiducial dataset of XO-3b as we were also able to find models providing initially great scores on their internal test datasets but whose results significantly underestimated the eclipse depth of that planet.
We describe the first data release from the Spitzer-IRAC Equatorial Survey (SpIES); a large-area survey of 115 deg^2 in the Equatorial SDSS Stripe 82 field using Spitzer during its warm mission phase. SpIES was designed to probe sufficient volume to
perform measurements of quasar clustering and the luminosity function at z > 3 to test various models for feedback from active galactic nuclei (AGN). Additionally, the wide range of available multi-wavelength, multi-epoch ancillary data enables SpIES to identify both high-redshift (z > 5) quasars as well as obscured quasars missed by optical surveys. SpIES achieves 5{sigma} depths of 6.13 {mu}Jy (21.93 AB magnitude) and 5.75 {mu}Jy (22.0 AB magnitude) at 3.6 and 4.5 microns, respectively - depths significantly fainter than WISE. We show that the SpIES survey recovers a much larger fraction of spectroscopically-confirmed quasars (98%) in Stripe 82 than are recovered by WISE (55%). This depth is especially powerful at high-redshift (z > 3.5), where SpIES recovers 94% of confirmed quasars, whereas WISE only recovers 25%. Here we define the SpIES survey parameters and describe the image processing, source extraction, and catalog production methods used to analyze the SpIES data. In addition to this survey paper, we release 234 images created by the SpIES team and three detection catalogs: a 3.6 {mu}m-only detection catalog containing 6.1 million sources, a 4.5 {mu}m-only detection catalog containing 6.5 million sources, and a dual-band detection catalog containing 5.4 million sources.
We present here the first observation of galactic AGB stars with the InfraRed Array Camera (IRAC) onboard the Spitzer Space Telescope. Our sample consists of 48 AGB stars of different chemical signature, mass loss rate and variability class. For each
star we have measured IRAC photometry and colors. Preliminary results shows that IRAC colors are sensitive to spectroscopic features associated to molecules and dust in the AGB wind. Period is only loosely correlated to the brightness of the stars in the IRAC bands. We do find, however, a tight period-color relation for sources classified as semiregular variables. This may be interpreted as the lack of warm dust in the wind of the sources in this class, as opposed to Mira variables that show higher infrared excess in all IRAC bands.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
