اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدBayesian Characterization of Main Sequence Binaries in the Old Open Cluster NGC 188
103
0
0.0
(
0
)
تأليف
Roger E. Cohen
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
The binary fractions of open and globular clusters yield powerful constraints on their dynamical state and evolutionary history. We apply publicly available Bayesian analysis code to a $UBVRIJHK_{S}$ photometric catalog of the old open cluster NGC 188 to detect and characterize photometric binaries along the cluster main sequence. This technique has the advantage that it self-consistently handles photometric errors, missing data in various bandpasses, and star-by-star prior constraints on cluster membership. Simulations are used to verify uncertainties and quantify selection biases in our analysis, illustrating that among binaries with mass ratios >0.5, we recover the binary fraction to better than 7% in the mean, with no significant dependence on binary fraction and a mild dependence on assumed mass ratio distribution. Using our photometric catalog, we recover the majority (65%$pm$11%) of spectroscopically identified main sequence binaries, including 8 of the 9 with spectroscopically measured mass ratios. Accounting for incompleteness and systematics, we derive a mass ratio distribution that rises toward lower mass ratios (within our $q >$0.5 analysis domain). We observe a raw binary fraction for solar-type main sequence stars with mass ratios $q >$0.5 of 42%$pm$4%, independent of the assumed mass ratio distribution to within its uncertainties, consistent with literature values for old open clusters but significantly higher than the field solar-type binary fraction. We confirm that the binaries identified by our method are more concentrated than single stars, in agreement with previous studies, and we demonstrate that the binary nature of those candidates which remain unidentified spectroscopically is strongly supported by photometry from Gaia DR2.
قيم البحث
اقرأ أيضاً
This paper provides a detailed comparison of the differences in parameters derived for a star cluster from its color-magnitude diagrams depending on the filters and models used. We examine the consistency and reliability of fitting three widely-used
stellar evolution models to fifteen combinations of optical and near-IR photometry for the old open cluster NGC 188. The optical filter response curves match those of the theoretical systems and are thus not the source of fit inconsistencies. NGC 188 is ideally suited to the present study thanks to a wide variety of high-quality photometry and available proper motions and radial velocities which enable us to remove non-cluster members and many binaries. Our Bayesian fitting technique yields inferred values of age, metallicity, distance modulus, and absorption as a function of the photometric band combinations and stellar models. We show that the historically-favored three band combinations of UBV and VRI can be meaningfully inconsistent with each other and with longer baseline datasets such as UBVRIJHKs. Differences among model sets can also be substantial. For instance, fitting Yi et al. (2001) and Dotter et al. (2008) models to UBVRIJHKs photometry for NGC 188 yields the following cluster parameters: age={5.78+ 0.03, 6.45+-0.04} Gyr, [Fe/H]={+0.125+-0.003, -0.077+-0.003} dex, m-M={11.441+-0.007, 11.525+-0.005} mag, and Av={0.162+-0.003, 0.236+-0.003} mag, respectively. Within the formal fitting errors, these two fits are substantially and statistically different. Such differences amongst fits using different filters and models are a cautionary tale regarding our current ability to fit star cluster color-magnitude diagrams. Additional modeling of this kind, with more models and star clusters, and future GAIA parallaxes are critical for isolating and quantifying the most relevant uncertainties in stellar evolutionary models.
We present the UV photometry of the old open cluster NGC188 obtained using images acquired with Ultraviolet Imaging Telescope (UVIT) on board the ASTROSAT satellite, in two far-UV (FUV) and one near-UV (NUV) filters. UVIT data is utilised in combinat
ion with optical photometric data to construct the optical and UV colour-magnitude diagrams (CMDs). In the FUV images, we detect only hot and bright blue straggler stars (BSSs), one hot subdwarf, and one white dwarf (WD) candidate. In the NUV images, we detect members up to a faintness limit of ~22 mag including 21 BSSs, 2 yellow straggler stars (YSSs), and one WD candidate. This study presents the first NUV-optical CMDs, and are overlaid with updated BaSTI-IAC isochrones and WD cooling sequence, which are found to fit well to the observed CMDs. We use spectral energy distribution (SED) fitting to estimate the effective temperatures, radii, and luminosities of the UV-bright stars. We find the cluster to have an HB population with three stars (Teff = 4750 - 21000 K). We also detect two yellow straggler stars, with one of them with UV excess connected to its binarity and X-ray emission.
In this paper, we present our results for the photometric and kinematical studies of old open cluster NGC 188. We determined various astrophysical parameters like limited radius, core and tidal radii, distance, luminosity and mass functions, total ma
ss, relaxation time etc. for the cluster using 2MASS catalog. We obtained the clusters distance from the Sun as 1721+/-41 pc and log (age)= 9.85+/-0.05 at Solar metallicity. The relaxation time of the cluster is smaller than the estimated cluster age which suggests that the cluster is dynamically relaxed. Our results agree with the values mentioned in the literature. We also determined the clusters apex coordinates as (281.88 deg, -44.76 deg) using AD-diagram method. Other kinematical parameters like space velocity components, cluster center and elements of Solar motion etc. have also been computed.
In this paper we present time series photometry of 104 variable stars in the cluster region NGC 1893. The association of the present variable candidates to the cluster NGC 1893 has been determined by using $(U-B)/(B-V)$ and $(J-H)/(H-K)$ two colour d
iagrams, and $V/(V-I)$ colour magnitude diagram. Forty five stars are found to be main-sequence variables and these could be B-type variable stars associated with the cluster. We classified these objects as $beta$ Cep, slowly pulsating B stars and new class variables as discussed by Mowlavi et al. (2013). These variable candidates show $sim$0.005 to $sim$0.02 mag brightness variations with periods of $<$ 1.0 d. Seventeen new class variables are located in the $H-R$ diagram between the slowly pulsating B stars and $delta$ Scuti variables. Pulsation could be one of the causes for periodic brightness variations in these stars. The X-ray emission of present main-sequence variables associated with the cluster lies in the saturated region of X-ray luminosity versus period diagram and follows the general trend by Pizzolato et al. (2003).
We present results of multi-epoch (fourteen nights during 2007-2010) $V$-band photometry of the cluster NGC 1893 region to identify photometric variable stars in the cluster. The study identified a total of 53 stars showing photometric variability. T
he members associated with the region are identified on the basis of spectral energy distribution, $J-H/H-K$ two colour diagram and $V/V-I$ colour-magnitude diagram. The ages and masses of the majority of pre-main-sequence sources are found to be $lesssim$ 5 Myr and in the range 0.5 $lesssim$ $M/M_{odot}$ $lesssim$ 4, respectively. These pre-main-sequence sources hence could be T Tauri stars. We also determined the physical parameters like disk mass and accretion rate from the spectral energy distribution of these T Tauri stars. The periods of majority of the T Tauri stars range from 0.1 to 20 day. The brightness of Classical T Tauri stars is found to vary with larger amplitude in comparison to Weak line T Tauri stars. It is found that the amplitude decreases with increase in mass, which could be due to the dispersal of disks of massive stars.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
