Kt Paul

Kt Paul
Christ University, Bangalore · Department of Physics

MSc MPhil PhD

About

45
Publications
3,268
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141
Citations

Publications

Publications (45)
Article
We present a follow-up study on the recent detection of two X-ray flaring events by MAXI/Gas Slit Camera observations in soft and hard X-rays from MAXI J0709–159 in the direction of HD 54786 (LY CMa), on 2022 January 25. The X-ray luminosity during the flare was around 1037 erg s−1 (MAXI), which got reduced to 1032 erg s−1 (NuSTAR) after the flare....
Article
Full-text available
We present a follow-up study on the recent detection of two X-ray flaring events by MAXI/Gas Slit Camera observations in soft and hard X-rays from MAXI J0709–159 in the direction of HD 54786 (LY CMa), on 2022 January 25. The X-ray luminosity during the flare was around 10 ³⁷ erg s ⁻¹ (MAXI), which got reduced to 10 ³² erg s ⁻¹ (NuSTAR) after the fl...
Preprint
We present a follow-up study on the recent detection of two X-ray flaring events by MAXI/GSC observations in soft and hard X-rays from MAXI J0709-159 in the direction of HD 54786 (LY CMa), on 2022 January 25. The X-ray luminosity during the flare was around 10^(37) erg/s (MAXI), which got reduced to 10^(32) erg/s (NuSTAR) after the flare. We took l...
Article
Full-text available
Over time, pre-main-sequence (PMS) stars evolve into main-sequence (MS) stars. Stars evolving from PMS to MS phase is a significant subject of research that aims to better understand stellar phases and their properties. Existing literature shows a lack of study of stars in between PMS and MS phase. 'We focused on what belongs in the midst of these...
Preprint
We performed the slitless spectroscopic survey to identify Classical (CBe) stars in open clusters older than 100 Myr. Observing a sample of 71 open clusters, we identified 13 CBe stars in 11 open clusters, one of, which (TYC 2679-432-1) is a new detection. The 13 CBe stars show both H$\alpha$ in emission and IR excess, which confirm that they posse...
Poster
Full-text available
There are two main types of galaxy formation models to explain the observations. The first asserts that massive elliptical galaxies formed in a single, rapid collapse of gas and dark matter, during which virtually all the gas was turned quickly into stars. Afterwards the galaxies changed only slowly as the stars evolved. This is what astronomers ca...
Article
Full-text available
We performed the slitless spectroscopic survey to identify classical Be (CBe) stars in open clusters older than 100 Myr. Observing a sample of 71 open clusters, we identified 13 CBe stars in 11 open clusters, one of, which (TYC 2679-432-1) is a new detection. The 13 CBe stars show both Ha in emission and IR excess, which confirm that they possess g...
Article
Full-text available
We performed the slitless spectroscopic survey to identify classical Be (CBe) stars in open clusters older than 100 Myr. Observing a sample of 71 open clusters, we identified 13 CBe stars in 11 open clusters, one of, which (TYC 2679-432-1) is a new detection. The 13 CBe stars show both H\(\alpha \) in emission and IR excess, which confirm that they...
Presentation
Full-text available
I have presented this talk, "Emission line stars in the transition phase from pre-main sequence to main sequence", at the 7th Regional Astronomers' Meeting through Google Meet Platform, which took place from 8th to 10th of September 2021. Under the sponsorship of IUCAA, Pune, India, it was organized by Mar Thoma College, Chungathara, Kerala, India,...
Preprint
In our earlier work we had discussed the possibility of primordial planets composed entirely of dark matter (DM) to be the main reason for not detecting DM particles. It has been suggested that primordial planets could have formed in the early Universe and the missing baryons in the Universe could be explained by primordial free-floating planets of...
Article
Full-text available
Pre-main sequence (PMS) stars evolve into main sequence (MS) phase over a period of time. Interestingly, we found a scarcity of studies in existing literature that examines and attempts to better understand the stars in PMS to MS transition phase. The purpose of the present study is to detect such rare stars, which we named as ‘Transition Phase’ (T...
Preprint
Full-text available
Pre-main sequence (PMS) stars evolve into main sequence (MS) phase over a period of time. Interestingly, we found a scarcity of studies in existing literature that examines and attempts to better understand the stars in PMS to MS transition phase. The purpose of the present study is to detect such rare stars, which we named as 'Transition Phase' (T...
Article
Full-text available
We report the first systematic study to identify and characterize a sample of classical Ae stars in the Galaxy. The spectra of these stars were retrieved from the A-star catalog using the Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST) survey. We identified the emission-line stars in this catalog from which 159 are confirmed as c...
Preprint
Full-text available
We report the first systematic study to identify and characterize a sample of classical Ae stars in the Galaxy. The spectra of these stars were retrieved from the A-star catalog using the Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST) survey. We identified the emission-line stars in this catalog from which 159 are confirmed as c...
Preprint
Full-text available
In this study, we analyze the emission lines of different species present in 118 Galactic field classical Be stars in the wavelength range of 3800 - 9000 \AA. We re-estimated the extinction parameter (A$_V$) for our sample stars using the newly available data from Gaia DR2 and suggest that it is important to consider A$_V$ while measuring the Balme...
Article
Full-text available
In this study, we analyze the emission lines of different species present in 118 Galactic field classical Be stars in the wavelength range of 3800 - 9000 Å. We re-estimated the extinction parameter (AV) for our sample stars using the newly available data from Gaia DR2 and suggest that it is important to consider AV while measuring the Balmer decrem...
Article
The underlying nature of the process of star formation quenching in the central regions of barred disc galaxies that is due to the action of stellar bar is not fully understood. We present a multi-wavelength study of four barred galaxies using the archival data from optical, ultraviolet, infrared, CO, and HI imaging data on star formation progressi...
Preprint
The underlying nature of the process of star formation quenching in the central regions of barred disc galaxies that is due to the action of stellar bar is not fully understood. We present a multi-wavelength study of four barred galaxies using the archival data from optical, ultraviolet, infrared, CO, and HI imaging data on star formation progressi...
Presentation
Full-text available
I presented this talk titled "Optical Spectroscopy of Galactic Field Classical Be Stars" in the Regional Astronomers' Meeting-VI during July 9-10, 2020. It was held by the initiative of WMO College, Wayanad, Kerala, India through Google Meet Platform under the sponsorship of IUCAA, Pune, India.
Article
Full-text available
A popular level article providing fundamental idea about the properties of Be stars and what kind of research is being carried out at CHRIST (Deemed to be University), Bangalore currently.
Article
The suppression of star formation in the inner kiloparsec regions of barred disk galaxies due to the action of bars is known as bar quenching. We investigate here the significance of bar quenching in the global quenching of star formation in the barred galaxies and their transformation to passive galaxies in the local Universe. We do this by measur...
Preprint
The suppression of star formation in the inner kiloparsec regions of barred disk galaxies due to the action of bars is known as bar quenching. We investigate here the significance of bar quenching in the global quenching of star formation in the barred galaxies and their transformation to passive galaxies in the local Universe. We do this by measur...
Article
Full-text available
The present study makes use of the unprecedented capability of the Gaia mission to obtain the stellar parameters such as distance, age, and mass of HAeBe stars. The accuracy of Gaia DR2 astrometry is demonstrated from the comparison of the Gaia DR2 distances of 131 HAeBe stars with the previously estimated values from the literature. This is one of...
Preprint
Full-text available
The present study makes use of the unprecedented capability of the Gaia mission to obtain the stellar parameters such as distance, age, and mass of HAeBe stars. The accuracy of Gaia DR2 astrometry is demonstrated from the comparison of the Gaia DR2 distances of 131 HAeBe stars with the previously estimated values from the literature. This is one of...
Poster
Full-text available
Taking advantage of the latest release of Gaia data, Gaia DR2, we extracted the distances to 131 HAeBe stars in our sample. Also, we estimated the age and mass of a sample of 110 HAeBe stars, using MIST isochrones and evolutionary tracks. We computed the mass accretion rates for HAeBe stars using the refined stellar masses and distances. We found e...
Article
The physical processes related to the eect of bars in the quenching of star formation in the region between the nuclear/central subkiloparsec region and the ends of the bar (bar region) of spiral galaxies is not fully understood. It is hypothesized that the bar can either stabilize the gas against collapse, inhibiting star formation, or eciently co...
Preprint
The physical processes related to the effect of bar in the quenching of star formation in the region between the nuclear/central sub-kpc region and the ends of the bar (bar-region) of spiral galaxies is not fully understood. It is hypothesized that the bar can either stabilize the gas against collapse, inhibiting star formation or efficiently consu...
Article
Full-text available
We have investigated the role of a few prominent excitation mechanisms viz. collisional excitation, recombination, continuum fluorescence and Lyman beta fluorescence on the OI line spectra in Herbig Ae/Be stars. The aim is to understand which of them is the central mechanism that explains the observed OI line strengths. The study is based on an ana...
Poster
Full-text available
Pre-Main Sequence (PMS) Stars are a class of Young Stellar Objects (YSOs) which form a crucial stage in the star formation process. Characterized by their masses, T-Tauri Stars (< 2 Mʘ) & Herbig Ae/Be stars (2 – 8 Mʘ) are observed during the PMS evolutionary phase. The protoplanetary disks of these stars serve as formation sites of planetary system...
Thesis
Classical Be stars are B−type stars in the main sequence that exhibit line emission over the photospheric spectrum attributed to a gaseous circumstellar disk. This disk formation, commonly known as the Be phenomenon, is one of the unsolved problems regarding Be stars. One of the possible solutions could be due to optically invisible companions (Por...
Article
Full-text available
With better understanding of the working physics behind the formation and evolution of stars, it has become increasingly important for observers to use an appropriate set of stellar evolutionary tracks and isochrones with respect to the objects of interest. We present a comparative study of three widely used competent stellar models -- MIST, PARSEC...
Article
Full-text available
Astronomy has seen unprecedented growth in the past century, due to the rise in multiwavelength observations. The foundation for multiwavelength astronomy is given by Astrometry; the science of position and motion determination of celestial bodies. We present a technique of determining equatorial coordinates of celestial bodies from their pixel coo...
Article
Magellanic Clouds are the nearby galaxies which are ideal to study the properties of metal poor stellar population. In this study, we explore the near-IR properties of optically identified classical Be stars in 19 star clusters in the Magellanic clouds. From an optically identified sample of 835 Be stars we obtained the J, H, K magnitudes of 389 st...
Conference Paper
Full-text available
We present the preliminary results from Near­Infrared spectroscopic (NIR) study of a sample of 23 Classical Be stars observed during 2015-­2016 using 2 m Himalayan Chandra Telescope (HCT), Hanle. NIR spectroscopy provides a powerful tool to understand the changes in the inner circumstellar disk of Be stars since HI emission lines in this spectral w...
Poster
Full-text available
We present the preliminary results of the spectroscopic study of few Classical Be Stars. A Classical Be star is defined as a non-supergiant B-type star whose spectrum has, or had at sometime, one or more Balmer lines in emission. The emission lines originate from a circumstellar disk which is formed by the material ejected from the star and the act...
Article
We present the optical spectroscopic study of two Classical Be stars, 59 Cyg and OT Gem obtained over a period of few months in 2009. We detected a rare triple-peak H$\alpha$ emission phase in 59 Cyg and a rapid decrease in the emission strength of H$\alpha$ in OT Gem, which are used to understand their circumstellar disks. We find that 59 Cyg is l...
Conference Paper
Full-text available
We present the preliminary results of high resolution spectroscopic study of 17 Classical Be stars observed using the echelle spectrograph at 2.3m Vainu Bappu Telescope, VBO, Kavalur. All the stars were observed in the wavelength range of 4100 ­ 10800Å during 2010 and 2011. We obtained a total of 44 spectra of resolution ~ 27000. Classical Be stars...
Article
We present an optical spectroscopic study based on 41 spectra of 4 Her and 32 spectra of 88 Her, obtained over a period of 6 months. We estimate the rotational velocity of these stars from HeI lines in the blue spectral region (4000–4500 Å). We find that these stars are likely to be rotating at a fractional critical rotation of ~0.80. We measure th...
Conference Paper
Full-text available
We present preliminary results of the spectroscopic study of two Be Stars, 4 Her and 88 Her. The time series spectra of these Be stars were obtained using the 1.02m reflector of Vainu Bappu Observatory, Kavalur, India. We obtained a total of 41 spectra for 4 Her and 32 spectra for 88 Her during February to July 2009, with 1Å resolution at Hα. The r...
Article
Full-text available
Catalogues of Be star candidates in the SMC and the LMC as identified by Mennickent et al. (2002A&A...393..887M) (~1000 stars) and Sabogal et al. (2005, Cat. J/MNRAS/361/1055) (2446 stars), respectively, were used. In order to obtain their NIR properties, we used the NIR IRSF catalogue (Kato et al. 2007, Cat. II/288) which has JHKs photometric data...
Article
Mennickent et al.and Sabogal et al.identified a large number of Classical Be (CBe) candidates in the L&SMC based on their photometric variability using the OGLEII database. They classified these stars into four different groups based on the appearance of their variability. We studied the infrared properties of the sample as well as the spectroscopi...
Article
Full-text available
Mennickent et al. (2002) presented a catalogue of 1056 Be star candidates in the Small Magellanic cloud (SMC) by studying light curve variation using OGLE II data base. They classified these Be star candidates of the SMC in four categories: Type 1 stars showing outbursts (139 stars); Type 2 stars showing sudden luminosity jumps (154 stars); Type 3...
Conference Paper
We estimate the duration of star formation in young clusters of the Small and Large Magellanic Clouds (SMC and LMC). It is estimated as the difference between Post- main sequence (Post-MS) age and Pre- main sequence (PMS) age. The present study aims to determine the PMS ages of clusters by combining optical and near-IR data. Prelimnary results of t...

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Projects

Projects (3)
Project
Using Gaia to refine the stellar parameters of Herbig Ae/Be stars
Archived project
To learn on the evolution of PMS stars in open clusters.