In the present paper, the CCD time series observations of cluster NGC 1960 and DOLIDZE 14 are per... more In the present paper, the CCD time series observations of cluster NGC 1960 and DOLIDZE 14 are performed to search the short periodic variable stars within them. Absolute photometry via secondary standardization transformation has been used to construct the light curves for the detection of pulsation in stars. A comprehensive study of membership of variable stars is discussed along with their classification. A total of 18 and 4 short periodic variables found in the field of NGC 1960 and DOLIDZE 14 respectively. The period and classification of 18 discovered short periodic type variable stars of NGC 1960 are discussed, which consist of one EB, one Planet transit, one γ − Dor, two δ Scuti − γ − Dor, two LADS, two irregular, two ro-tational, three RRC and four Ellipsoidal type variable stars. In the case of DOLIDZE 14, four discovered variables consist of one miscellaneous, one rotational, two binary type variable stars. A comparative analysis of each short periodic variable star has be...
The stellar enhancement of the cluster NGC 110 is investigated in various optical and infrared (I... more The stellar enhancement of the cluster NGC 110 is investigated in various optical and infrared (IR) bands. The radial density profile of the IR region does not show a stellar enhancement in the central region of the cluster. This stellar deficiency may be occurring by undetected fainter stars due to the contamination effect of massive stars. Since, our analysis is not indicating the stellar enhancement below 16.5 mag of I band, therefore the cluster is assumed to be a group of fainter stars. The proposed magnitude scatter factor would be an excellent tool to understand the characteristic of colour-scattering of stars. The most probable members do not coincide with the model isochronic fitting in the optical bands due to poor data quality of P P MXL catalogue. The different values of the mean proper motions are found for the fainter stars of the cluster and field regions, whereas similar values are obtained for radial zones of the cluster. The symmetrical distribution of fainter star...
The spectroscopic and photometric analysis of sample Am stars are carried out to determine the st... more The spectroscopic and photometric analysis of sample Am stars are carried out to determine the stellar characteristics of each studied star. The CCD photometric analysis of HD 98851 and HD 207561 show clear evidence of pulsation variability of 1.55 hr and 5.8 min respectively. Similarly, a clear evidence of the photometric variability is also found for an Am star HD 73045 which is likely to be pulsating in nature with a period of about 36-min. We are also found dissimilar behaviour of elemental abundances of various ions for HD 113878 and HD 118660. The basic stellar parameters (mass, luminosity, radius, life time, distance, proper-motion etc.) are determined for each sample stars. The tidal radius and boundaries of habitable zone of each star are also computed to search the extra-terrestrial life. Asteroseismic mass scale test shows greater stellar masses compare to the solar mass.
The Fourier-discrete-peridogram are used to identify pulsation modes in variables. We have found ... more The Fourier-discrete-peridogram are used to identify pulsation modes in variables. We have found two pulsation modes in V1 and V2 among 13 new variables as described by Abbas et al.. The five variables V9 to V13 are not shown close to periodic values by analysis of the frequency distribution of multi-band data and also create difficulty to describe their varied nature. The multi-band periodic values of V1 and V6 are matched with known literature values. The scattering of the varied nature of secondary pulsation modes is eliminated by moving average methodology. The phase curve of secondary mode is found to be more smooth compared to a prominent mode of pulsation.
The open star clusters (OSC) are important tracers for understanding the Galactic evolution. The ... more The open star clusters (OSC) are important tracers for understanding the Galactic evolution. The parametric study of these astronomical-objects are crucial task due to the appearing sequence of the members of OSC. These members are defined through the various approaches such as photometric, statistical, kinematics etc. In the present paper, we have been using the photometric colours of the identified stars for categorized them into the blue and red component groups and identification of these groups is possible through (B-V) vs V colour magnitude diagram (CMD). Furthermore, the influence/effect of these groups is also examined in the estimation of cluster parameters. The stellar enhancement of cluster NGC 6866 is found through the blue-component-stars (BCS) and the linear solution of best fitted values of King Models of the radial-density-profile (RDP) gives the core radius as 5.22±0.29 arcmin. The good agreement of present estimated parameters of the cluster with the literature see...
The radial density profile (RDP) of cluster DOLIDZE 14 provides the radius of 9.8 arcmin, it is b... more The radial density profile (RDP) of cluster DOLIDZE 14 provides the radius of 9.8 arcmin, it is based on consideration of first plateau region of RDP. This value is less than the radius which comes through consideration of the second plateau region. The stars, which are inside of the cluster radius, are used to estimate the distance-modulus and E(I-R) by fitting theoretical isochrone on the colour-magnitude diagram (CMD). The best fitted stellar isochrone of solar matellacity provides these values as 11.15 mag and 0.25 mag, respectively. These results are used to estimate the mass-function slope of the cluster, which comes to be different that of Salpeter-Value. The enhancement of brighter stars does not found within the cluster region which indicates its old age. The Mass-Segregation phenomena of cluster is found between massive and lighter stars but not found in fainter stars, having magnitude greater than 15 mag in I-band. The relaxation-time is very little in the comparison of i...
The photometric analysis of sample Am stars is carried out to determine the stellar characteristi... more The photometric analysis of sample Am stars is carried out to determine the stellar characteristics and to constrain the stellar dynamics. The spectroscopic analysis of the studied Am stars confirms their general characteristics of Am stars. The available data on elemental abundances for HD 113878 and HD 118660 have shown different characteristics during different epochs of observations. The basic stellar parameters (mass, luminosity, radius, life time, distance, proper-motion, etc.) are also determined to identify the stellar habitat zones for earth like exoplanet. Such information is important to identify suitable planets for human settlement in the near future. In this connection, the tidal radius and boundaries of the habitable zone of each star have been computed to support the search of an extra-terrestrial life around them. Asteroseismic mass scale test shows greater stellar masses comparable to the solar mass.
We have been represented the collective information of estimation procedures of parameters of the... more We have been represented the collective information of estimation procedures of parameters of the open clusters and put them together for showing the importance of clusters to understand their role in stellar evolution phenomenon. Moreover, we have been discussed about analytic techniques to determine the structural and dynamical properties of galactic clusters. The members of clusters provide unique opportunity to determine their basic parameters such as: age, metallicity, distance, reddening etc. The membership probabilities of stars of clusters is assigned through the various approaches and each approach provides different number of probable members of the cluster. Here, we have been briefly discussed about various approaches to determine the stellar membership within clusters.
The total-to-selective extinction RV in the direction of a cluster is found to be 3.12 +/- 0.2 (c... more The total-to-selective extinction RV in the direction of a cluster is found to be 3.12 +/- 0.2 (close to its normal value). We derive the luminosity and mass functions for the cluster main sequence stars. The mass function slope is found to be -2.29 +/- 0.20 which is close to Salpeter value. We find evidence of mass segregation process in the cluster which is not yet dynamically relaxed. We have performed time series photometric observations to detect variable stars within star cluster NGC 1960. The DAOPHOT-II package is utilized to estimate the apparent stellar magnitudes of stars. The secondary standardization method is applied to the transformation of these apparent magnitudes into standard values. The magnitude-time diagrams (light curves) of stars are constructed to identify possible variability nature within them. The stars, having sufficient magnitude variation with time, are considered to be variable stars and their period values have computed through PERIOD04 package. These...
The photometric data reduction procedure is the fundamental step to get the signal information of... more The photometric data reduction procedure is the fundamental step to get the signal information of stellar objects. These signals are collected through the CCD camera; the brief notes have been given about the character and work function of the CCD camera. Here, we are briefly discussing about the reduction procedure of the UBVRI photometric system, which is worldwide utilizing for stellar study from last two or three decades. Moreover, the procedure of standardization has been given for the captured CCD images. Presently, there are several databases/catalogues, which are supplemented by the various surveys; these databases are effective to analysis the properties of any interested stellar objects. The associated web-service of these databases/catalogues is effective to improve the scientific knowledge of the Society, and provide an opportunity to study of the stellar dynamics and associated evolution. We have been listed their brief information and importance in the Scientific Socie...
The search of secondary pulsations is carried out to understand the possible relations among the ... more The search of secondary pulsations is carried out to understand the possible relations among the known parameters of variables of the cluster, NGC 6866. These pulsations arise due to the various ongoing physical phenomena of the variables. Moreover, pulsations of the variables are identified through the visual inspection of their frequency-amplitude distributions. A total of 18 variables among the 28 known variables are showing the secondary pulsation modes. Furthermore, these pulsation modes do not occur for PV, EA, EB, Elliptical and semi-regular. In addition, the field variables seem to be the red-component-stars (RCS) for the studied cluster. The smoothness of the frequency-amplitude curves, signal to noise ratio and the significant limits are play major role for deciding the real peak or frequency values. We are not rejected those amplitude peak of parabolic patterns, for which, the amplitude is greater than then significant limit of variables. The weight of pulsation frequenci...
We present here the detailed optical and infra-red photometric analysis of the open star cluster ... more We present here the detailed optical and infra-red photometric analysis of the open star cluster IC 361. On studying the radial density profile, radial extent of the cluster is found to be 8.0 +/- 0.5 arcmin. The basic physical parameters of the cluster such as E(B-V) = 0.56 +/- 0.10 mag, E(V-K) = 1.72+/-0.12 mag, log(Age)=9.10+/-0.05, and (m-M)0 = 12.54 +/-.05 mag are obtained using the color-color and color-magnitude diagrams. IC 361 is found to be located at a distance of 3.22 +/- 0.07 kpc. Using the archival proper motion catalogues, we estimate mean proper motions of IC 361 as 4.97+/-0.17 mas yr-1 and -5.80+/-0.18 mas yr-1 in the direction of RA and DEC, respectively. We derive the luminosity and mass functions for the cluster main sequence stars. The mass function slope is found to be -1.06+/-0.09 which is too low compare than Salpeter value.
In the present paper, the CCD time series observations of cluster NGC 1960 and DOLIDZE 14 are per... more In the present paper, the CCD time series observations of cluster NGC 1960 and DOLIDZE 14 are performed to search the short periodic variable stars within them. Absolute photometry via secondary standardization transformation has been used to construct the light curves for the detection of pulsation in stars. A comprehensive study of membership of variable stars is discussed along with their classification. A total of 18 and 4 short periodic variables found in the field of NGC 1960 and DOLIDZE 14 respectively. The period and classification of 18 discovered short periodic type variable stars of NGC 1960 are discussed, which consist of one EB, one Planet transit, one γ − Dor, two δ Scuti − γ − Dor, two LADS, two irregular, two ro-tational, three RRC and four Ellipsoidal type variable stars. In the case of DOLIDZE 14, four discovered variables consist of one miscellaneous, one rotational, two binary type variable stars. A comparative analysis of each short periodic variable star has be...
The stellar enhancement of the cluster NGC 110 is investigated in various optical and infrared (I... more The stellar enhancement of the cluster NGC 110 is investigated in various optical and infrared (IR) bands. The radial density profile of the IR region does not show a stellar enhancement in the central region of the cluster. This stellar deficiency may be occurring by undetected fainter stars due to the contamination effect of massive stars. Since, our analysis is not indicating the stellar enhancement below 16.5 mag of I band, therefore the cluster is assumed to be a group of fainter stars. The proposed magnitude scatter factor would be an excellent tool to understand the characteristic of colour-scattering of stars. The most probable members do not coincide with the model isochronic fitting in the optical bands due to poor data quality of P P MXL catalogue. The different values of the mean proper motions are found for the fainter stars of the cluster and field regions, whereas similar values are obtained for radial zones of the cluster. The symmetrical distribution of fainter star...
The spectroscopic and photometric analysis of sample Am stars are carried out to determine the st... more The spectroscopic and photometric analysis of sample Am stars are carried out to determine the stellar characteristics of each studied star. The CCD photometric analysis of HD 98851 and HD 207561 show clear evidence of pulsation variability of 1.55 hr and 5.8 min respectively. Similarly, a clear evidence of the photometric variability is also found for an Am star HD 73045 which is likely to be pulsating in nature with a period of about 36-min. We are also found dissimilar behaviour of elemental abundances of various ions for HD 113878 and HD 118660. The basic stellar parameters (mass, luminosity, radius, life time, distance, proper-motion etc.) are determined for each sample stars. The tidal radius and boundaries of habitable zone of each star are also computed to search the extra-terrestrial life. Asteroseismic mass scale test shows greater stellar masses compare to the solar mass.
The Fourier-discrete-peridogram are used to identify pulsation modes in variables. We have found ... more The Fourier-discrete-peridogram are used to identify pulsation modes in variables. We have found two pulsation modes in V1 and V2 among 13 new variables as described by Abbas et al.. The five variables V9 to V13 are not shown close to periodic values by analysis of the frequency distribution of multi-band data and also create difficulty to describe their varied nature. The multi-band periodic values of V1 and V6 are matched with known literature values. The scattering of the varied nature of secondary pulsation modes is eliminated by moving average methodology. The phase curve of secondary mode is found to be more smooth compared to a prominent mode of pulsation.
The open star clusters (OSC) are important tracers for understanding the Galactic evolution. The ... more The open star clusters (OSC) are important tracers for understanding the Galactic evolution. The parametric study of these astronomical-objects are crucial task due to the appearing sequence of the members of OSC. These members are defined through the various approaches such as photometric, statistical, kinematics etc. In the present paper, we have been using the photometric colours of the identified stars for categorized them into the blue and red component groups and identification of these groups is possible through (B-V) vs V colour magnitude diagram (CMD). Furthermore, the influence/effect of these groups is also examined in the estimation of cluster parameters. The stellar enhancement of cluster NGC 6866 is found through the blue-component-stars (BCS) and the linear solution of best fitted values of King Models of the radial-density-profile (RDP) gives the core radius as 5.22±0.29 arcmin. The good agreement of present estimated parameters of the cluster with the literature see...
The radial density profile (RDP) of cluster DOLIDZE 14 provides the radius of 9.8 arcmin, it is b... more The radial density profile (RDP) of cluster DOLIDZE 14 provides the radius of 9.8 arcmin, it is based on consideration of first plateau region of RDP. This value is less than the radius which comes through consideration of the second plateau region. The stars, which are inside of the cluster radius, are used to estimate the distance-modulus and E(I-R) by fitting theoretical isochrone on the colour-magnitude diagram (CMD). The best fitted stellar isochrone of solar matellacity provides these values as 11.15 mag and 0.25 mag, respectively. These results are used to estimate the mass-function slope of the cluster, which comes to be different that of Salpeter-Value. The enhancement of brighter stars does not found within the cluster region which indicates its old age. The Mass-Segregation phenomena of cluster is found between massive and lighter stars but not found in fainter stars, having magnitude greater than 15 mag in I-band. The relaxation-time is very little in the comparison of i...
The photometric analysis of sample Am stars is carried out to determine the stellar characteristi... more The photometric analysis of sample Am stars is carried out to determine the stellar characteristics and to constrain the stellar dynamics. The spectroscopic analysis of the studied Am stars confirms their general characteristics of Am stars. The available data on elemental abundances for HD 113878 and HD 118660 have shown different characteristics during different epochs of observations. The basic stellar parameters (mass, luminosity, radius, life time, distance, proper-motion, etc.) are also determined to identify the stellar habitat zones for earth like exoplanet. Such information is important to identify suitable planets for human settlement in the near future. In this connection, the tidal radius and boundaries of the habitable zone of each star have been computed to support the search of an extra-terrestrial life around them. Asteroseismic mass scale test shows greater stellar masses comparable to the solar mass.
We have been represented the collective information of estimation procedures of parameters of the... more We have been represented the collective information of estimation procedures of parameters of the open clusters and put them together for showing the importance of clusters to understand their role in stellar evolution phenomenon. Moreover, we have been discussed about analytic techniques to determine the structural and dynamical properties of galactic clusters. The members of clusters provide unique opportunity to determine their basic parameters such as: age, metallicity, distance, reddening etc. The membership probabilities of stars of clusters is assigned through the various approaches and each approach provides different number of probable members of the cluster. Here, we have been briefly discussed about various approaches to determine the stellar membership within clusters.
The total-to-selective extinction RV in the direction of a cluster is found to be 3.12 +/- 0.2 (c... more The total-to-selective extinction RV in the direction of a cluster is found to be 3.12 +/- 0.2 (close to its normal value). We derive the luminosity and mass functions for the cluster main sequence stars. The mass function slope is found to be -2.29 +/- 0.20 which is close to Salpeter value. We find evidence of mass segregation process in the cluster which is not yet dynamically relaxed. We have performed time series photometric observations to detect variable stars within star cluster NGC 1960. The DAOPHOT-II package is utilized to estimate the apparent stellar magnitudes of stars. The secondary standardization method is applied to the transformation of these apparent magnitudes into standard values. The magnitude-time diagrams (light curves) of stars are constructed to identify possible variability nature within them. The stars, having sufficient magnitude variation with time, are considered to be variable stars and their period values have computed through PERIOD04 package. These...
The photometric data reduction procedure is the fundamental step to get the signal information of... more The photometric data reduction procedure is the fundamental step to get the signal information of stellar objects. These signals are collected through the CCD camera; the brief notes have been given about the character and work function of the CCD camera. Here, we are briefly discussing about the reduction procedure of the UBVRI photometric system, which is worldwide utilizing for stellar study from last two or three decades. Moreover, the procedure of standardization has been given for the captured CCD images. Presently, there are several databases/catalogues, which are supplemented by the various surveys; these databases are effective to analysis the properties of any interested stellar objects. The associated web-service of these databases/catalogues is effective to improve the scientific knowledge of the Society, and provide an opportunity to study of the stellar dynamics and associated evolution. We have been listed their brief information and importance in the Scientific Socie...
The search of secondary pulsations is carried out to understand the possible relations among the ... more The search of secondary pulsations is carried out to understand the possible relations among the known parameters of variables of the cluster, NGC 6866. These pulsations arise due to the various ongoing physical phenomena of the variables. Moreover, pulsations of the variables are identified through the visual inspection of their frequency-amplitude distributions. A total of 18 variables among the 28 known variables are showing the secondary pulsation modes. Furthermore, these pulsation modes do not occur for PV, EA, EB, Elliptical and semi-regular. In addition, the field variables seem to be the red-component-stars (RCS) for the studied cluster. The smoothness of the frequency-amplitude curves, signal to noise ratio and the significant limits are play major role for deciding the real peak or frequency values. We are not rejected those amplitude peak of parabolic patterns, for which, the amplitude is greater than then significant limit of variables. The weight of pulsation frequenci...
We present here the detailed optical and infra-red photometric analysis of the open star cluster ... more We present here the detailed optical and infra-red photometric analysis of the open star cluster IC 361. On studying the radial density profile, radial extent of the cluster is found to be 8.0 +/- 0.5 arcmin. The basic physical parameters of the cluster such as E(B-V) = 0.56 +/- 0.10 mag, E(V-K) = 1.72+/-0.12 mag, log(Age)=9.10+/-0.05, and (m-M)0 = 12.54 +/-.05 mag are obtained using the color-color and color-magnitude diagrams. IC 361 is found to be located at a distance of 3.22 +/- 0.07 kpc. Using the archival proper motion catalogues, we estimate mean proper motions of IC 361 as 4.97+/-0.17 mas yr-1 and -5.80+/-0.18 mas yr-1 in the direction of RA and DEC, respectively. We derive the luminosity and mass functions for the cluster main sequence stars. The mass function slope is found to be -1.06+/-0.09 which is too low compare than Salpeter value.
Uploads
Papers by Gireesh Joshi