scholarly journals Development of a Southern Vilnius Standard Photometric System

2021 ◽  
Author(s):  
◽  
Murray Charles Forbes
Keyword(s):  
Local System ◽  
Standard System ◽  
Physical Parameters ◽  
Atmospheric Effects ◽  
Photometric System ◽  
Open Star Clusters ◽  
Cluster Membership ◽  
Open Star ◽  
Solar Metallicity ◽  
The Individual

<p>The Vilnius Standard Photometric System is said to have several advantages over other photometric systems; reduction procedures free of systematic errors, a homogeneous set of standard stars, accurate dereddening, spectral classification and calibration of physical parameters for normal stars, and a good detection rate of abnormal stars. To investigate these, two southern, open star clusters (Omicron Velorum and Kappa Crucis) have been measured in the Vilnius system. The observations were used to derive astrophysical parameters such as age ((45 plus-minus l5)x106 and (10 plus-minus 3)x10 6 years respectively), composition (both solar metallicity), distance to the clusters (m-M = 5m.94 plus-minus 0.02 and 12m.18 plus-minus 0.05), interstellar reddening along our light of sight to the clusters (Ey-v = 0m.00 plus-minus 0.02 and 0m.31 plus-minus 0.09), and cluster membership probabilities for the individual stars. These compared favorably with the consensus of similar analyses made by observers using other photometric systems, with one exception being the distance to Kappa Crucis ( = 11m.59). As no stars further south than declination -26 degrees have been measured in the (original) Vilnius System, it was necessary to calibrate the local system to the standard system by measuring equatorial stars common to both. To alleviate this problem in the future, suitable southern stars were measured to form a southern standard system. Initially bright stars evenly spread across the sky were calibrated - this will ensure any future observing programme will have nearby standards. The next phase of the programme was to calibrate the E-region stars - this is a set of stars in common use as southern standards in other photometric systems. The final phase was to calibrate a sequence of stars near the south celestial pole - producing a set of stars so that the same standards can be observed at any time during the year. This southern standard system could not be completely established in the time available (it is approximately 50% finished), due to the larger than expected uncertainties in the measurements largely caused by the atmospheric effects of the Mount Pinatubo eruption.</p>

scholarly journals Development of a Southern Vilnius Standard Photometric System

2021 ◽  
Author(s):  
◽  
Murray Charles Forbes
Keyword(s):  
Local System ◽  
Standard System ◽  
Physical Parameters ◽  
Atmospheric Effects ◽  
Photometric System ◽  
Open Star Clusters ◽  
Cluster Membership ◽  
Open Star ◽  
Solar Metallicity ◽  
The Individual

<p>The Vilnius Standard Photometric System is said to have several advantages over other photometric systems; reduction procedures free of systematic errors, a homogeneous set of standard stars, accurate dereddening, spectral classification and calibration of physical parameters for normal stars, and a good detection rate of abnormal stars. To investigate these, two southern, open star clusters (Omicron Velorum and Kappa Crucis) have been measured in the Vilnius system. The observations were used to derive astrophysical parameters such as age ((45 plus-minus l5)x106 and (10 plus-minus 3)x10 6 years respectively), composition (both solar metallicity), distance to the clusters (m-M = 5m.94 plus-minus 0.02 and 12m.18 plus-minus 0.05), interstellar reddening along our light of sight to the clusters (Ey-v = 0m.00 plus-minus 0.02 and 0m.31 plus-minus 0.09), and cluster membership probabilities for the individual stars. These compared favorably with the consensus of similar analyses made by observers using other photometric systems, with one exception being the distance to Kappa Crucis ( = 11m.59). As no stars further south than declination -26 degrees have been measured in the (original) Vilnius System, it was necessary to calibrate the local system to the standard system by measuring equatorial stars common to both. To alleviate this problem in the future, suitable southern stars were measured to form a southern standard system. Initially bright stars evenly spread across the sky were calibrated - this will ensure any future observing programme will have nearby standards. The next phase of the programme was to calibrate the E-region stars - this is a set of stars in common use as southern standards in other photometric systems. The final phase was to calibrate a sequence of stars near the south celestial pole - producing a set of stars so that the same standards can be observed at any time during the year. This southern standard system could not be completely established in the time available (it is approximately 50% finished), due to the larger than expected uncertainties in the measurements largely caused by the atmospheric effects of the Mount Pinatubo eruption.</p>

scholarly journals Photometric and kinematic study of the three intermediate age open clusters NGC 381, NGC 2360, and Berkeley 68

2020 ◽  
Vol 494 (4) ◽  
pp. 4713-4729 ◽  
Author(s):  
Jayanand Maurya ◽  
Y C Joshi
Keyword(s):  
Relaxation Times ◽  
Outer Region ◽  
Mass Function ◽  
Open Clusters ◽  
Open Star Clusters ◽  
Low Mass Stars ◽  
Cluster Membership ◽  
Open Star ◽  
Solar Metallicity ◽  
Mass Segregation

ABSTRACT We present UBVRcIc photometric study of three intermediate age open star clusters NGC 381, NGC 2360, and Berkeley 68 (Be 68). We examine the cluster membership of stars using recently released Gaia DR2 proper motions and obtain a total of 116, 332, and 264 member stars in these three clusters. The mean reddening of E(B − V) = 0.36 ± 0.04, 0.08 ± 0.03, and 0.52 ± 0.04 mag is found in the direction of these clusters where we observe an anomalous reddening towards NGC 381. We fitted the solar metallicity isochrones to determine age and distance of the clusters which are found to be log(Age) = 8.65 ± 0.05, 8.95 ± 0.05, and 9.25 ± 0.05 yr with the respective distance of 957 ± 152, 982 ± 132, and 2554 ± 387 pc for the clusters NGC 381, NGC 2360, and Be 68. A two-stage power law in the mass function (MF) slope is observed in the cluster NGC 381, however, we observe only a single MF slope in the clusters NGC 2360 and Be68. To study a possible spatial variation in the slope of MF, we estimate slopes separately in the inner and the outer regions of these clusters and notice a steeper slope in outer region. The dynamic study of these clusters reveals deficiency of low-mass stars in their inner regions suggesting the mass segregation process in all these clusters. The relaxation times of 48.5, 78.9, and 87.6 Myr are obtained for the clusters NGC 381, NGC 2360, and Be 68, respectively, which are well below to their respective ages. This suggests that all the clusters are dynamically relaxed.

Double degenerate candidates in the open cluster NGC 6633

2019 ◽  
Vol 15 (S357) ◽  
pp. 20-23
Author(s):  
Joseph W. Barnett ◽  
Kurtis A. Williams
Keyword(s):  
White Dwarfs ◽  
Binary Star ◽  
Open Cluster ◽  
Star Clusters ◽  
Sequence Evolution ◽  
Total System ◽  
Open Star Clusters ◽  
Low Mass Stars ◽  
Cluster Membership ◽  
Open Star

AbstractThe study of white dwarfs, the end stage of stellar evolution for more than 95% of stars, is critical to bettering our understanding of the late stages of the lives of low mass stars. In particular, the post main sequence evolution of binary star systems is complex, and the identification and analysis of double degenerate systems is a crucial step in constraining models of binary star systems. Binary white dwarfs in open star clusters are particularly useful because cluster parameters such as distance, metal content, and total system age are more tightly constrained than for field double degenerates. Here we use the precision astrometry from the Gaia Data Release 2 catalog to study two other white dwarfs which were identified as candidate double degenerates in the field of the open star cluster NGC 6633. One of the two objects, LAWDS 4, is found to have astrometric properties fully consistent with that of the cluster. In such a case, the object is significantly overluminous for a single white dwarf, strongly indicating binarity. The second candidate binary, LAWDS 7, appears to be inconsistent with cluster membership, though a more thorough analysis is necessary to properly quantify the probability. At present we are proceeding to model the photometric and spectroscopic data for both objects as if they were cluster member double degenerates. Results of this latter analysis are forthcoming. Our results will add crucial data to the study of binary star evolution in open star clusters.

scholarly journals Point-Spread Function (PSF) Photometric Analysis of Open Clusters: Melotte 72 & NGC 2158

2015 ◽  
Vol 12 (4) ◽  
Author(s):  
Muhammad Mirza ◽  
Zain Rahim
Keyword(s):  
Point Spread Function ◽  
Stellar System ◽  
Open Clusters ◽  
Sloan Digital Sky Survey ◽  
Physical Parameters ◽  
Open Star Clusters ◽  
Open Star ◽  
Point Spread ◽  
Sky Survey ◽  
Spread Function

Point Spread Function (PSF) photometry of open star clusters Melotte 72 and NGC 2158 was performed using g and r band data from the Sloan digital Sky Survey (SDSS) Data Release 7. Instrumental magnitudes of stars in both bands were transformed into calibrated magnitudes using standard equation. Color-Magnitude (CM) diagrams were produced and compared with the SDSS isochrones for AB stellar system for different ages and/or metallicities. The objective of this study was to determine the physical parameters (age, distance, metallicity, reddening) of open clusters from CM diagrams. The best fit isochrones were used to estimate cluster parameters. The observed parameters were then compared with the WEBDA data base. KEYWORDS: PSF Photometry, Melotte 72, SDSS, NGC 2158, Isochrone Fitting, IRAF

scholarly journals Screening for Early Signs of Paternal Perinatal Affective Disorder in Expectant Fathers: A Cluster Analysis Approach

2020 ◽  
Vol 11 (1) ◽  
pp. 10
Author(s):  
Sonia Mangialavori ◽  
Michele Giannotti ◽  
Marco Cacioppo ◽  
Federico Spelzini ◽  
Franco Baldoni
Keyword(s):  
Perceived Stress ◽  
Behavioral Problems ◽  
Marital Adjustment ◽  
Risky Behaviors ◽  
Perinatal Period ◽  
Dyadic Adjustment ◽  
Male Population ◽  
Cluster Membership ◽  
Expectant Fathers ◽  
The Individual

Previous studies documented gender-related differences in the expression of Perinatal Affective Disorders. However, little attention has been paid to screening the male population during the perinatal period. This study was based on three aims: (1) to investigate the mental health of expectant fathers based on their levels of depression, anxiety, addiction, anger attacks/hostility, and somatization, identifying psychological profiles; (2) to analyze the association between these profiles and the individual variable of perceived stress; (3) and to examine the association between these profiles and the couple’s variable of marital adjustment. A total of 350 Italian expectant fathers in the last trimester of pregnancy were asked to fill in questionnaires concerning perceived stress, dyadic adjustment, psychiatric symptomatology, and depression. Three different clusters were found: “psychologically healthy men” (68%) with low levels of symptoms on all the scales; “men at risk of externalized behavioral problems” (17.1%), characterized by one or more addictive or risky behaviors and moderate levels of scales scores; and “men experiencing psychological distress” (14.9%), with the highest scores on all the scales. A significant association emerged among the perceived stress, marital adjustment, and cluster membership. These results highlight the importance of screening fathers in perinatal health services, which are still predominantly mother-centered, and underscore the necessity to create tailored and personalized interventions.

scholarly journals Massive open star clusters using the VVV survey

2012 ◽  
Vol 545 ◽  
pp. A54 ◽  
Author(s):  
A.-N. Chené ◽  
J. Borissova ◽  
J. R. A. Clarke ◽  
C. Bonatto ◽  
D. J. Majaess ◽  
...  
Keyword(s):  
Star Clusters ◽  
Open Star Clusters ◽  
Open Star

Photometric study of open star clusters in II quadrant: Teutsch 1 and Riddle 4

New Astronomy ◽  
2016 ◽  
Vol 42 ◽  
pp. 66-77 ◽  
Author(s):  
D. Bisht ◽  
R.K.S. Yadav ◽  
A.K. Durgapal
Keyword(s):  
Star Clusters ◽  
Photometric Study ◽  
Open Star Clusters ◽  
Open Star

scholarly journals A study of spatial structure of galactic open star clusters

2002 ◽  
Vol 383 (1) ◽  
pp. 153-162 ◽  
Author(s):  
Nilakshi ◽  
R. Sagar ◽  
A. K. Pandey ◽  
V. Mohan
Keyword(s):  
Spatial Structure ◽  
Star Clusters ◽  
Open Star Clusters ◽  
Open Star

scholarly journals Orbits of Open Star Clusters NGC 6067, NGC 2506 ANG IC 465

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Geeta Rangwal ◽  
R. K. S. Yadav ◽  
Alok K. Durgapal
Keyword(s):  
Proper Motion ◽  
Star Clusters ◽  
Open Star Clusters ◽  
Motion Data ◽  
Open Star ◽  
Galactic Clusters

The studies of the orbits of star clusters are very important to understand the evolution of these objects. The survival or dissolution of star clusters in galactic tides within which they orbit depends on their orbit history. The orbits of three galactic clusters namely NGC 6067, NGC 2506 and IC 4651 are calculated using newly available proper motion data taken from GAIA data. These orbits are traced backwards in time which is equal to the age of the clusters. The main parameters of the orbits such as eccentricity, apogalactic distance and perigalactic distance are calculated.

scholarly journals Effect of Variable Viscosity and Gravity Modulation on Linear and Non-Linear Rayleigh-Benard Convection in Viscoelastic Ferromagnetic Liquids

2020 ◽  
Vol 9 (3) ◽  
pp. 3482-3488
Keyword(s):  
Stability Analysis ◽  
Heat Transport ◽  
Linear Stability ◽  
Linear Stability Analysis ◽  
Variable Viscosity ◽  
Low Frequency ◽  
Physical Parameters ◽  
Gravity Modulation ◽  
Non Linear ◽  
The Individual

The combined effect of various parameters of gravity modulation on the onset of ferroconvection is studied for both linear and non-linear stability. The effect of various parameters of ferroconvection is studied for linear stability analysis. The resulting seven-mode generalized Lorenz model obtained in non-linear stability analysis is solved using Runge -Kutta-Felberg 45 method to analyze the heat transfer. Consequently the individual effect of gravity modulation on heat transport has been investigated. Further, the effect of physical parameters on heat transport has been analyzed and depicted graphically. The low-frequency gravity modulation is observed to get an effective influence on the stability of the system. Therefore ferro convection can be advanced or delayed by controlling different governing parameters. It shows that the influence of gravity modulation stabilizes system.

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