The Nainital-Cape Survey

Joshi, Santosh; Martinez, Peter; Chowdhury, S.; Chakradhari, N. K.; Joshi, Y. C.; Heerden, P. van; Medupe, T.; Kumar, Yerra Bharat; Kuhn, Rudolf B.

doi:10.1051/0004-6361/201527242

Cited by 38 publications

(65 citation statements)

References 92 publications

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“…where M V and M I denote absolute magnitudes in V and I band, respectively. We note here that no significant metallicity gradient has been seen across the LMC and SMC (e.g., Grocholski et al 2006;Cioni 2009;Parisi et al 2009;Feast et al 2010;Deb & Singh 2014;Joshi et al 2016) hence any variation in the MCs P-L relations due to metallicity variation is not considered in the present study. Even if we accept any variation in the metallicity at all as reported in some previous studies (e.g., Tammann et al 2003;Carrera et al 2008;Kapakos & Hatzidimitriou 2012;Dobbie et al 2014) the difference in reddening is found to be ∼0.001 mag which is insignificant in comparison of the scatter in the P-L diagrams itself.…”

Section: Methodology Of Reddening Determinationmentioning

confidence: 58%

“…For example, Borissova et al (2004Borissova et al ( , 2006 suggested the existence of homogeneous, old and metal-poor stellar halo in the LMC based on the velocity dispersion of RR Lyrae stars. On the basis of spatial and age distributions of Cepheids reported in the Optical Gravitational Lensing Experiment (OGLE) Phase-III survey, Joshi & Joshi (2014) and Joshi et al (2016) affirmed that a major star formation triggered in these two dwarf galaxies at ≈ 200 ± 50 Myr ago. Choi et al (2018) revealed a significant warp in the south west region of LMC outer disk towards SMC and an off-centered tilted LMC bar which they believe is consistent with a direct collision between the two clouds in agreement with the earlier studies (e.g., Besla et al 2012;Carrera et al 2017;Zivick et al 2018Zivick et al , 2019.…”

Section: Introductionmentioning

confidence: 92%

“…During the last several years, a large number of studies based on different stellar populations have been carried out to understand the structure of the MCs (e.g., Glatt et al 2010;Wagner-Kaiser & Sarajedini 2013;Subramanian & Subramaniam 2013;Joshi & Joshi 2014;Joshi et al 2016;Muraveva et al 2018). In the present study, we have a total of 4251 Cepheids in the LMC and 4546 Cepheids in the SMC, largest sample among any previous studies so far which provides a chance to examine their spatial distributions within the clouds in order to understand the geometry of the disk of these galaxies.…”

Section: Spatial Distributionmentioning

confidence: 99%

“…The MCs provide the ideal laboratory to probe the spatially resolved star formation history (SFH) and dust distributions since these galaxies are not just close enough to be resolved into stars but also moder-⋆ E-mail: yogesh@aries.res.in ⋆⋆ Data used in the present study is only available in the electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr ately affected by the interstellar extinction and foreground Milky Way stars (Rubele et al 2018). In recent times, the distribution of different stellar populations in the MCs has been studied by various authors (e.g., Alcock et al 1999;, 2000Nikolaev et al 2004;Borissova et al 2004Borissova et al , 2006Harris & Zaritsky 2009;Glatt et al 2010;Cioni et al 2011;Subramanian & Subramaniam 2013;Joshi & Joshi 2014;Jacyszyn-Dobrzeniecka et al 2016;Nayak et al 2016;Joshi et al 2016;Rubele et al 2018;Choi et al 2018), among others. For example, Borissova et al (2004Borissova et al ( , 2006 suggested the existence of homogeneous, old and metal-poor stellar halo in the LMC based on the velocity dispersion of RR Lyrae stars.…”

Section: Introductionmentioning

confidence: 99%

“…One can also distinguish the two modes through the Fourier parameters R 21 and φ 21 determined from the shape of their light curves. During the past few decades, many studies have been directed towards the understanding structure and reddening distribution in the MCs em-ploying the Cepheids (e.g., Udalski et al 1999;Nikolaev et al 2004;Subramanian & Subramaniam 2015;Joshi & Joshi 2014;Joshi et al 2016;Inno et al 2016;Scowcroft et al 2016).…”

Section: Introductionmentioning

confidence: 99%

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Reddening map and recent star formation in the Magellanic Clouds based on OGLE IV Cepheids

Joshi

Panchal

2019

A&A

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Context. The reddening maps of the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) are constructed using the Cepheid Period-Luminosity (P-L) relations. Aims. We examine reddening distribution across the LMC and SMC through largest data on Classical Cepheids provided by the OGLE Phase IV survey. We also investigate the age and spatio-temporal distributions of Cepheids to understand the recent star formation history in the LMC and SMC. Methods. The V and I band photometric data of 2476 fundamental mode (FU) and 1775 first overtone mode (FO) Cepheids in the LMC and 2753 FU and 1793 FO Cepheids in the SMC are analyzed for their P-L relations. We convert period of FO Cepheids to corresponding period of FU Cepheids before combining the two modes of Cepheids. Both galaxies are divided into small segments and combined FU and FO P-L diagrams are drawn in two bands for each segment. The reddening analysis is performed on 133 segments covering a total area of about 154.6 deg 2 in the LMC and 136 segments covering a total area of about 31.3 deg 2 in the SMC. By comparing with well calibrated P-L relations of these two galaxies, we determine reddening E(V − I) in each segment and equivalent reddening E(B − V) assuming the normal extinction law. The period-age relations are used to derive the age of the Cepheids.Results. Using reddening values in different segments across the LMC and SMC, reddening maps are constructed. We find clumpy structures in the reddening distributions of the LMC and SMC. From the reddening map of the LMC, highest reddening of E(V − I) = 0.466 mag is traced in the region centered at α ∼ 85 o .13, δ ∼ −69 o .34 which is in close vicinity of the star forming HII region 30 Doradus. In the SMC, maximum reddening of E(V − I) = 0.189 mag is detected in the region centered at α ∼ 12 o .10, δ ∼ −73 o .07. The mean reddening values in the LMC and SMC are estimated as E(V − I) LMC = 0.113 ± 0.060 mag, E(B − V) LMC = 0.091 ± 0.050 mag, E(V − I) S MC = 0.049 ± 0.070 mag, and E(B − V) S MC = 0.038 ± 0.053 mag.Conclusions. The LMC reddening map displays heterogeneous distribution having small reddening in the central region and higher reddening towards eastern side of the LMC bar. The SMC have relatively small reddening in peripheral regions but larger reddening towards south-west region. In these galaxies, we see an evidence of a common enhanced Cepheid population at around 200 Myr ago which appears to have occurred due to close encounter between the two clouds.

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Section: Methodology Of Reddening Determinationmentioning

confidence: 58%

Section: Introductionmentioning

confidence: 92%

Section: Spatial Distributionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Reddening map and recent star formation in the Magellanic Clouds based on OGLE IV Cepheids

Joshi

Panchal

2019

A&A

Self Cite

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A study of pulsation & rotation in a sample of A-K type stars in the Kepler field

Chowdhury

Joshi

Engelbrecht

et al. 2018

Astrophys Space Sci

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We present the results of time-series photometric analysis of 15106 A-K type stars observed by the Kepler space mission. We identified 513 new rotational variables and measured their starspot rotation periods as a function of spectral type and discuss the distribution of their amplitudes. We examined the well-established period-color relationship that applies to stars of spectral types F5-K for all of these rotational variables and, interestingly, found that a similar period-color relationship appears to extend to stars of spectral types A7 to early-F too. This result is not consistent with the very foundation of the period-color relationship. We have characterized 350 new non-radial pulsating variables such as A- and F-type candidate Scuti, Doradus and hybrid stars, which increases the known candidate non-radial pulsators in the Kepler field significantly, by ∼20%. The relationship between two recently constructed observables, and , was also studied for the large sample of non-radial pulsators, which shows that the distribution in the logarithm of () can be used as a potential tool to distinguish between the non-radial pulsators, to some extent. Through visual inspection of the light curves and their corresponding frequency spectra, we found 23 new candidate red giant solar-like oscillators not previously reported in the literature. The basic physical parameters such as masses, radii and luminosities of these solar-like oscillators were also derived using asteroseismic relations.Electronic Supplementary MaterialThe online version of this article (10.1007/s10509-018-3480-1) contains supplementary material, which is available to authorized users.

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Pulsation of chemically peculiar stars

Paunzen

2022

Proc. IAU

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This paper reviews our current knowledge about pulsating chemically peculiar (CP) stars. CP stars are slowly rotating upper main-sequence objects, efficiently employing diffusion in their atmospheres. They can be divided into magnetic and non-magnetic objects. Magnetic activity significantly influence their pulsational characteristics. Only a handful of magnetic, classical pulsating objects are now known. The only exceptions are about 70 rapidly oscillating Ap stars, which seem to be located within a very tight astrophysical parameter space. Still, many observational and theoretical efforts are needed to understand all important physical aspects and their interrelationships. The most important steps to reach these goals are reviewed.

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The Nainital-Cape Survey

Cited by 38 publications

References 92 publications

Reddening map and recent star formation in the Magellanic Clouds based on OGLE IV Cepheids

Reddening map and recent star formation in the Magellanic Clouds based on OGLE IV Cepheids

A study of pulsation & rotation in a sample of A-K type stars in the Kepler field

Pulsation of chemically peculiar stars

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