48 research outputs found
Two Practical Methods for Coronal Intensity Determination
Determining the relative brightness of the solar corona is one of the most
critical stages in solar eclipse studies. For this purpose, images taken with
different exposures and polarization angles in white-light observations are
used. The composite image of each polarization angle is produced by combining
the images of different exposures. With the help of the intensity calibration
function of these images, the relative intensity of the corona can be
calculated. The total brightness of the solar corona is calculated using Stokes
parameters obtained from intensity values of three polarization angles. In this
study, two methods are presented: the first is used to obtain the intensity
calibration function of the photographic material using calibration images, and
the second is used to calculate the combined intensity values of images taken
with different polarization angles.Comment: 15 pages, including 13 figures and 5 tables, accepted for publication
in Solar Physic
A New Approach to Calculate Coronal Electron Density: Simplified van de Hulst's Method
Determining the electron density is a challenging task in solar corona
studies, as it requires certain assumptions to be made, such as symmetric,
homogeneous and radial distribution, thermal equilibrium, etc. In such studies,
the observed corona brightness is based on the coronal electron density. An
important paper on the calculation of electron density was published in 1950 by
van de Hulst in an article titled "The Electron Density of the Solar Corona".
The author developed a method with some assumptions to calculate the electron
density from the observed corona brightness. We presented here, a new
simplified calculation method for the coronal electron density is presented.
The integral equation solution given by van de Hulst is interpreted from a
different perspective and the coronal electron density is calculated using
only observational data without making any additional adjustments such as
successive approximations and multiple attempts.Comment: 14 pages, 9 figures and 7 tables, accepted for publication in Physics
and Astronomy Report
Population types of cataclysmic variables in the solar neighborhood
The Galactic orbital parameters of 159 cataclysmic variables in the Solar neighbourhood are calculated, for the first time, to determine their population types using published kinematical parameters. Population analysis shows that about 6 per cent of cataclysmic variables in the sample are members of the thi
ck disc component of the Galaxy. This value is consistent with the fraction obt
ained from star count analysis. The rest of the systems in the sample are found to be in the thin disc component of the Galaxy. Our analysis revealed no halo CVs in the Solar vicinity. About 60 per cent of the thick disc CVs have orbital periods be low the orbital period gap. This result is roughly consistent with the predictions of population synthesis models developed for cataclysmic variables. A kinematical age of 13 Gyr is obtained using total space velocity dispersion of the most probable thick disc CVs which is consistent with the age of thick disc component of the Galaxy
CCD UBVRI photometry of the open cluster Berkeley 8
The poorly studied Berkeley 8 (Be8) open cluster is analysed from CCD UBVRI
photometric data taken with the 0.90 m telescope at the Sierra Nevada
Observatory. The Z = +0.008 PARSEC isochrone gave us a reddening of E(B-V) =
0.69 +- 0.03, a distance of 3410 +- 300 pc and an age of 2.8 +- 0.2 Gyr. Its
median Gaia DR2 distance, d = 3676 +- 810 pc is in good agreement with our
photometric distances, 3410 - 3620 pc within the uncertainties. The kinematic
parameters of five likely members of Be 8 with the circular orbits, ecc =
[0.23, 0.30] reflect the properties of the Galactic thin disc, which is also
consistent with what is expected of its metal content ([M/H] = -0.27). Be8 with
R > 9 kpc (co-rotation gap at 9 kpc) may have been originating from different
galactic radius or different star formation region.Comment: 16 pages, including 15 figures and 6 table, accepted for publication
in Turkish Journal of Physic
Turfgrass species response exposed to increasing rates of glyphosate application
To investigate the response of nine turfgrass species exposed to increasing rates of glyphosate application, the dry matter production, visual leaf injury symptoms (e.g., chlorosis and necrosis) and the concentrations of shikimate and mineral nutrients were determined in shoots. The rates of foliar glyphosate application were 0%, 5% (1.58 mM), and 20% (6.32mM) of the recommended application rate for weed control. In general, there was a negative and weak correlation between the intensity of visual injury and relative decreases in shoot dry matter production caused by glyphosate application. The decreases in shoot dry matter production and the severity of leaf damage pronounced by increasing glyphosate rate showed a substantial variation among the turfgrass species. Of the turfgrass species tested, Festuca arundinacea ‘Falcon’ and Buchloe dactyloides ‘Bowie’were selected as the most tolerant and sensitive species to applied sublethal rates of glyphosate as judged from visual injury ratings, respectively. At the highest glyphosate rate, shoot dryweightwas decreased by 4-fold in Bowie and only 1.6-fold in Falcon. When glyphosatewas
not applied, shoot shikimate concentration of all species was very low and below 2.8mol g−1 FW (fresh weight). Glyphosate applications resulted in increases in shoot shikimate concentration with substantial
variations among species. At 6.32mM glyphosate treatment, shikimate concentration ranged between 156.1mol g−1 (F. rubra, Ambrose) and 16.5mol g−1 FW (F. rubra, Cindy Lou). However, the highly sensitive and the tolerant genotypes were not different in shoot shikimate concentrations. Even, in the case of some genotypes, high glyphosate tolerance is accompanied by higher shoot concentrations of shikimate. Depending on the turfgrass species and mineral nutrients tested, increasing glyphosate application either
did not affect or reduced mineral nutrient concentrations. In the case of decreases in shoot concentration of mineral nutrients, the decreases in Ca, Mg, Mn and Fe were most distinct. The results obtained indicate existence of a large genetic variation in tolerance to glyphosate toxicity among the turfgrass
species. This differential variation in tolerance to glyphosate could not be explained by the changes in shoot concentrations of shikimate and mineral nutrients
Enlem-Boylam Şebekesi Yardımıyla Doğru Alan Hesabı: Gökcisimlerinin Gözlenen Yüzeyi İçin Bir Yaklaşım
A Dynamical Evolution Study of the Open Clusters: Berkeley 10, Berkeley 81, Berkeley 89 and Ruprecht 135
By utilising Gaia EDR3 photometric / astrometric data, we studied the
dynamical evolution from the obtained astrophysical, structural and dynamical
parameters of the open clusters (OCs), Berkeley 10 (Be 10), Berkeley 81 (Be
81), Berkeley 89 (Be 89), and Ruprecht 135 (Ru 135). The Gaia EDR3 photometric
distances from the isochrone fitting method are smaller than the ones of Gaia
EDR2. The relaxation times of four OCs are smaller than their ages, in this
regard, they are dynamically relaxed. Their steep overall mass function slopes
mean that their low mass stars outnumber their massive ones. Their large
/ relatively small values imply an advanced mass segregation.
Therefore, they seem to have lost their low-mass stars much to the field. Be
89's outer parts indicate an expansion with time. However, Be 10 and Be 81 show
the relatively shrinkage core/cluster radii due to dynamical evolution. Ru 135
(1.0 Gyr) may have a primordial origin, instead of shrinking in size and mass
with time. Be 89's tidal radius is less than its cluster radius. This means
that its member stars lie within its tidal radius, in the sense it is
gravitationally bound to the cluster. For the rest OCs, the cluster members
beyond their tidal radii are gravitationally unbound to the clusters, which are
more influenced by the potential of the Galaxy.Comment: 30 pages, 33 figures and 6 tables. Accepted for publication in New
Astronom