Publications (79)
Discovery of Fullerenes in the Shell of Candidate Luminous Blue Variable WRAY 16-232
R. Arun, S. A. Prasoon, Blesson Mathew +5
We report the discovery of fullerene in the circumstellar environment of WRAY~16-232, a strong candidate luminous blue variable. Multiple pointings of archival \textit{Spitzer} IRS…
Be phenomenon in open clusters: Results from a survey of emission-line stars in young open clusters
Blesson Mathew, Annapurni Subramaniam, Bhuwan Chandra Bhatt
Emission-line stars in young open clusters are identified to study their properties, as a function of age, spectral type and their evolutionary state. 207 open star clusters were o…
Detection of X-ray Polarization in the High Synchrotron Peaked Blazar 1ES 1959+650
Athira M. Bharathan, C. S. Stalin, Rwitika Chatterjee +4
We report the measurement of X-ray polarization in the high synchrotron peaked blazar 1ES 1959+650. Of the four epochsof observations from the {\it Imaging X-ray Polarimetry Explor…
Excitation mechanism of OI lines in Herbig Ae/Be stars
Blesson Mathew, P. Manoj, Mayank Narang +7
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…
Spectroscopic study of late-type emission-line stars using the data from LAMOST DR6
D. Edwin, Blesson Mathew, B. Shridharan +5
Low-mass emission-line stars belong to various evolutionary stages, from pre-main-sequence young stars to evolved stars. In this work, we present a catalog of late-type (F0 to M9)…
The curious case of PDS 11: a nearby, >10 Myr old, classical T Tauri binary system
Blesson Mathew, P. Manoj, B. C. Bhatt +3
We present results of our study of PDS 11 binary system, which belongs to a rare class of isolated, high galactic latitude T Tauri stars. Our spectroscopic analysis reveals that PD…
A study of the role of Lyman β fluorescence on OI line strengths in Be stars
Blesson Mathew, Dipankar P. K. Banerjee, Annapurni Subramaniam +1
The possibility of the Lyβ fluorescence mechanism being operational in classical Be stars and thereby contributing to the strength of the OI 8446 à line has been recognized for lo…
What drives the wheels of evolution in NGC 1512? A UVIT study
Thomas Robin, Sreeja S Kartha, Ujjwal Krishnan +4
Environmental and secular processes play a pivotal role in the evolution of galaxies. These can be due to external processes such as interactions or internal processes due to the a…
Emission line star catalogues post-Gaia DR3: A validation of Gaia DR3 data using LAMOST OBA emission catalogue
B. Shridharan, Blesson Mathew, Suman Bhattacharyya +9
Gaia DR3 and further releases have the potential to identify and categorise new emission-line stars in the Galaxy. We perform a comprehensive validation of astrophysical parameters…
Non-Linear Solar EUV-Driven Sodium Release from the Lunar Surface: A Contrast to the Linear PSD Model
A Devaraj, S Narendranath, Sreeja S Kartha +7
The correlation between solar Extreme Ultra-Violet (EUV) radiation above 8.8 eV and the release of sodium from the lunar surface via photon-stimulated desorption (PSD) is investiga…
A multi-epoch spectral and photometric study to understand the nature of the interesting Be star candidate HD 249179
Suman Bhattacharyya, Blesson Mathew, S Muneer +2
HD 249179, a B5 star with unclear classification as either a classical Be star or a high-mass X-ray binary (HMXB) system, is investigated using the first multi-epoch spectral and p…
Infrared studies of the Be star X Per
Blesson Mathew, D. P. K. Banerjee, Sachindra Naik +1
Photometric and spectroscopic results are presented for the Be star X Per/HD 24534 from near-infrared monitoring in 2010-2011. The star is one of a sample of selected Be/X-ray bina…
Discovery of 2716 hot emission-line stars from LAMOST DR5
Shridharan B, Blesson Mathew, Nidhi S +4
We present a catalog of 3339 hot emission-line stars (ELS) identified from 451,695 O, B, and A type spectra, provided by the LAMOST DR5 release. We developed an automated python ro…
Star formation around three co-moving HAeBe stars in the Cepheus Flare
Piyali Saha, Maheswar G., Blesson Mathew +1
The presence of three more Herbig Ae/Be (HAeBe) stars in the Cepheus Flare within a 1.5 radius centered on HD 200775 suggests that star formation is prevalent in a wider…
The A-X infrared bands of Aluminum Oxide in stars: search and new detections
D. P. K. Banerjee, W. P. Varricatt, Blesson Mathew +2
We describe a search for the A-X infrared bands of AlO with a view to better understand the characteristics of this radical. These bands are infrequently encountered in astronomica…
Identification of new Classical Ae stars in the Galaxy using LAMOST DR5
R. Anusha, Blesson Mathew, B. Shridharan +6
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 us…
Insights on the Optical and Infrared Nature of MAXI J0709-159: Implications for High-Mass X-ray Binaries
Suman Bhattacharyya, Blesson Mathew, Gourav Banerjee +4
In our previous study (Bhattacharyya et al., 2022), HD~54786, the optical counterpart of the MAXI J0709-159 system, was identified to be an evolved star, departing from the main se…
Study of the transient nature of classical Be stars using multi-epoch optical spectroscopy
Gourav Banerjee, Blesson Mathew, K. T. Paul +8
Variability is a commonly observed property of classical Be stars (CBe) stars. In extreme cases, complete disappearance of the Hα emission line occurs, indicating a disc-less stat…
Discovery of a possible symbiotic binary in the Large Magellanic Cloud
Blesson Mathew, Warren A. Reid, R. E. Mennickent +1
We report the discovery of a possible symbiotic star, in the Large Magellanic Cloud (LMC). The object under consideration here, designated as RP 870, was detected during the course…
Detection of a new sample of Galactic White Dwarfs in the direction of the Small Magellanic Cloud
A. V. Sidharth, B. Shridharan, Blesson Mathew +7
In this study, we demonstrate the efficacy of the Ultraviolet Imaging Telescope (UVIT) in identifying and characterizing white dwarfs (WDs) within the Milky Way Galaxy. Leveraging…
Optical Spectroscopy of Classical Be Stars in Old Open Clusters
Madhu Kashyap Jagadeesh, Blesson Mathew, K. T. Paul +4
We performed the optical spectroscopy of 16 classical Be stars in 11 open clusters older than 100 Myr. Ours is the first spectroscopic study of classical Be stars in open clusters…
Clustering of low mass stars around Herbig Be star IL Cep -- Evidence of "Rocket Effect" using Gaia EDR3 ?
R. Arun, Blesson Mathew, G. Maheswar +7
We study the formation and the kinematic evolution of the early type Herbig Be star IL Cep and its environment. The young star is a member of the Cep OB3 association, at a distance…
A statistical search for Star-Planet Interaction in the UltraViolet using GALEX
Gayathri Viswanath, Mayank Narang, P. Manoj +2
Most (~82%) of the over 4000 confirmed exoplanets known today orbit very close to their host stars, within 0.5 au. Planets at such small orbital distances can result in significant…
Decoding the X-ray flare from MAXI J0709-159 using optical spectroscopy and multi-epoch photometry
Suman Bhattacharyya, Blesson Mathew, Savithri H Ezhikode +10
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 (…
Investigation of the correlation between optical and -ray flux variation in the blazar Ton 599
Bhoomika Rajput, Amit Kumar Mandal, Ashwani Pandey +3
The correlation between optical and -ray flux variations in blazars reveals a complex behaviour. In this study, we present our analysis of the connection between changes in opt…
The Interaction Jigsaw: Investigating star formation in interacting galaxies
Thomas Robin, Sreeja S Kartha, Akhil Krishna R +5
Interaction between galaxies play a pivotal role in their evolution. Ongoing star formation in spiral galaxies can be affected by these processes. We select a sample of interacting…
Quasar catalogue for the astrometric calibration of the forthcoming ILMT survey
Amit Kumar Mandal, Bikram Pradhan, Jean Surdej +3
Quasars are ideal targets to use for astrometric calibration of large scale astronomical surveys as they have negligible proper motion and parallax. The forthcoming 4-m Internation…
Near-infrared Observations of Be/X-ray Binary Pulsar A0535+262
Sachindra Naik, Blesson Mathew, D. P. K. Banerjee +2
We present results obtained from an extensive near-infrared spectroscopic and photometric observations of the Be/X-ray binary A0535+262/HDE 245770 at different phases of its ~111 d…
Fullerenes in the circumstellar medium of Herbig Ae/Be stars: Insights from the Spitzer mid-infrared spectral catalog
R. Arun, Blesson Mathew, P. Manoj +4
This study presents the largest mid-infrared spectral catalog of Herbig Ae/Be stars to date, containing the Spitzer Infrared Spectrograph spectra of 126 stars. Based on the catalog…
Serendipitous detection of an intense X-ray flare in the weak-line T Tauri star KM Ori with SRG/eROSITA
Savithri H. Ezhikode, Hema Anilkumar, R. Arun +8
Weak-line T Tauri stars (WTTS) exhibit X-ray flares, likely resulting from magnetic reconnection that heats the stellar plasma to very high temperatures. These flares are difficult…
Dust Reverberation Mapping of Z229-15
Amit Kumar Mandal, Suvendu Rakshit, C. S. Stalin +6
We report results of the dust reverberation mapping (DRM) on the Seyfert 1 galaxy Z229-15 at z = 0.0273. Quasi-simultaneous photometric observations for a total of 48 epochs were a…
Optical spectroscopy of Classical Be stars in open clusters
Blesson Mathew, Annapurni Subramaniam
We present a spectroscopic study of 150 Classical Be stars in 39 open clusters using medium resolution spectra in the wavelength range 3800 - 9000 Ã . One-third of the sample (48 s…
Optical spectroscopy of Galactic field Classical Be stars
Gourav Banerjee, Blesson Mathew, K. T. Paul +3
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 Ã . We re-estimated the ex…
The broadband spectral energy distribution of candidate neutrino blazars
Athira M Bharathan, C. S. Stalin, Markus Böttcher +3
Blazars, the jet dominated class of AGN comprising flat spectrum radio quasars (FSRQs) and BL Lac objects (BL Lacs) are now increasingly identified as potential sources of high ene…
Kinematic Study of Molecular Gas in Cometary Globule -- LBN 437
S. Aardra, Namitha Issac, Archana Soam +2
Bright-rimmed, cometary-shaped star-forming globules, associated with HII regions, are remnants of compressed molecular shells exposed to ultraviolet radiation from central OB-type…
Identifying the population of T-Tauri stars in Taurus: UV-optical synergy
Prasanta K. Nayak, Mayank Narang, Manoj Puravankara +9
With the third data release of the Gaia mission DR3 with its precise photometry and astrometry, it is now possible to study the behaviour of stars at a scale never seen befo…
Long-term optical and ray variability of the blazar PKS~1222+216
Savithri H. Ezhikode, Amit Shukla, Gulab C. Dewangan +4
The ray emission from flat-spectrum radio quasars (FSRQs) is thought to be dominated by the inverse Compton scattering of the external sources of photon fields, e.g., accretio…
A census of young stellar population associated with the Herbig Be star HD 200775
Piyali Saha, Maheswar G., Kamath U. S. +4
The region surrounding the well-known reflection nebula, NGC 7023, illuminated by a Herbig Be star, HD 200775, located in the dark cloud L1174 is studied in this work. Based on the…
Understanding the secular evolution of NGC 628 using UVIT
K. Ujjwal, Sreeja S. Kartha, Smitha Subramanian +3
Secular and environmental effects play a significant role in regulating the star formation rate and hence the evolution of the galaxies. Since UV flux is a direct tracer of the sta…
Spectroscopic study of Herbig Ae/Be stars in the Galactic Anti-center region from LAMOST DR5
S. Nidhi, Blesson Mathew, B. Shridharan +3
We study a sample of 119 Herbig Ae/Be stars in the Galactic anti-center direction using the spectroscopic data from Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOS…
Beyond the Rings: Polar Ring Galaxy NGC 4262 and its Globular Cluster System
Akhil Krishna R, Sreeja S Kartha, Blesson Mathew
In the context of the hierarchical model of galaxy evolution, polar ring galaxies (PRGs) are considered the intermediate phase between ongoing mergers and quiescent galaxies. This…
Identification of emission-line stars in transition phase from pre-main sequence to main sequence
Suman Bhattacharyya, Blesson Mathew, Gourav Banerjee +3
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 att…
Disentangling the association of PAH molecules with star formation : Insights from JWST and UVIT
K. Ujjwal, Sreeja S Kartha, Akhil Krishna R +4
Polycyclic Aromatic Hydrocarbons (PAHs) are ubiquitous complex molecules in the interstellar medium and are used as an indirect indicator of star-formation. On the other hand the u…
Study of correlation between optical flux and polarization variations in BL Lac objects
Bhoomika Rajput, Ashwani Pandey, C. S. Stalin +1
Polarized radiation from blazars is one key piece of evidence for synchrotron radiation at low energy, which also shows variations. We present here our results on the correlation a…
Pre-main sequence stars, emission stars and recent star formation in the Cygnus Region
Bhavya B, Blesson Mathew, Annapurni Subramaniam
The recent star formation history in the Cygnus region is studied using 5 clusters (IC 4996, NGC 6910, Berkeley 87, Biurakan 2 and Berkeley 86). The optical data from the literatur…
Multi-wavelength spectral modelling of the candidate neutrino blazar PKS 0735+178
Athira M Bharathan, C. S. Stalin, S. Sahayanathan +2
The BL Lac object PKS 0735+178 was in its historic -ray brightness state during December 2021. This period also coincides with the detection of a neutrino event IC211208A, whic…
Estimation of the size and structure of the broad line region using Bayesian approach
Amit Kumar Mandal, Suvendu Rakshit, C. S. Stalin +3
Understanding the geometry and kinematics of the broad line region (BLR) of active galactic nuclei (AGN) is important to estimate black hole masses in AGN and study the accretion p…
Changing look AGN Mrk 590: Broad line region and black hole mass from photometric reverberation mapping
Amit Kumar Mandal, Malte Schramm, Suvendu Rakshit +9
We present the results of photometric reverberation mapping observations on the changing look active galactic nucleus Mrk 590 at z = 0.026. The observations were carried out from J…
DES J024008.08-551047.5:A new member of the polar ring galaxy family
Krishna R. Akhil, Sreeja S Kartha, Blesson Mathew +3
During the visual observations of optical imaging data obtained from the DECaLS, a serendipitous discovery emerged, revealing the presence of a ringed galaxy, DES J024008.08-551047…
Study of the Balmer decrements for Galactic classical Be stars using the Himalayan Chandra Telescope of India
Gourav Banerjee, Blesson Mathew, Suman Bhattacharyya +3
In a recent study, Banerjee et al. (2021) produced an atlas of all major emission lines found in a large sample of 115 Galactic field Be stars using the 2-m Himalayan Chandra Teles…
NGC 7419: A young open cluster with a number of very young intermediate mass pre-MS stars
Annapurni Subramaniam, Blesson Mathew, Bhuwan Chandra Bhatt +1
We present a photometric and spectroscopic study of the young open cluster NGC 7419, which is know to host a large number of classical Be stars for reasons not well understood. Bas…
Optical/IR studies of Be stars in NGC 6834 with emphasis on two specific stars
Blesson Mathew, Watson P. Varricatt, Annapurni Subramaniam +2
We present optical and infrared photometric and spectroscopic studies of two Be stars in the 70--80-Myr-old open cluster NGC 6834. NGC 6834(1) has been reported as a binary from sp…
Disentangling the two sub-populations of early Herbig Be stars using VLT/X-Shooter spectra
B. Shridharan, Blesson Mathew, R. Arun +5
Early Herbig Be (HBe) stars are massive, young stars accreting through the Boundary Layer mechanism. However, given the rapid ( 2 Myr) evolution of early Herbig stars to the mai…
REMAP: Determination of the inner edge of the dust torus in AGN by measuring time delays
Amit Kumar Mandal, Suvendu Rakshit, Indrani Pal +3
Active galactic nuclei (AGN) are high luminosity sources powered by accretion of matter onto SMBHs located at the centres of galaxies. The SMBH is surrounded by a broad emission li…
On the mass accretion rate and infrared excess in Herbig Ae/Be Stars
R. Arun, Blesson Mathew, P. Manoj +5
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 Gai…
Studies of the Be star X Persei during a bright infrared phase
Blesson Mathew, D. P. K. Banerjee, Sachindra Naik +1
We present multi-epoch photometric and spectroscopic near-infrared observations of the Be star X Persei in the JHK bands covering the wavelength range 1.08 to 2.35 micron. Combinin…
Estimation of Stellar Parameters and Mass Accretion Rate of Classical T Tauri Stars from LAMOST DR6
S. Nidhi, Blesson Mathew, B. Shridharan +3
Classical T Tauri stars are low-mass pre-main sequence stars with an active circumstellar environment. In this work we present the identification and study of 260 Classical T Tauri…
Polycyclic Aromatic Hydrocarbons in the circumstellar medium of Herbig Ae/Be stars
R. Arun, Blesson Mathew, B. Shridharan +4
We present a comprehensive mid-infrared spectroscopic survey of 124 Herbig Ae/Be stars using newly processed Spitzer/IRS spectra from the newly released CASSISjuice database. Based…
UVIT view of Centaurus A; a detailed study on positive AGN feedback
Prajwel Joseph, P. Sreekumar, C. S. Stalin +4
$\require{mediawiki-texvc}$ Supermassive black holes at the centre of active galactic nuclei (AGN) produce relativistic jets that can affect the star formation characteristics of t…
Long term optical and infrared variability characteristics of Fermi Blazars
P. Z. Safna, C. S. Stalin, Suvendu Rakshit +1
We present long term optical and near infrared flux variability analysis of 37 blazars detected in the -ray band by the {\it Fermi Gamma-Ray Space Telescope}. Among them, 30 ar…
UVIT/AstroSat observation of TW Hya
Prasanta K. Nayak, Mayank Narang, P. Manoj +7
The paper demonstrates the spectroscopic and photometric capabilities of the Ultra-Violet Imaging Telescope (UVIT) to study T-Tauri stars (TTSs). We present the first UVIT/Far-UV (…
Simultaneous X-ray and optical polarization observations of the blazar Mrk 421
Athira M. Bharathan, C. S. Stalin, S. Sahayanathan +7
We present near-simultaneous X-ray and optical polarization measurements in the high synchrotron peaked (HSP) blazar Mrk 421. The X-ray polarimetric observations were carried out u…
Analysis of membership probability in nearby young moving groups with Gaia DR2
K. Ujjwal, Sreeja S. Kartha, Blesson Mathew +2
We analyze the membership probability of young stars belonging to nearby moving groups with DR2 data. The sample of 1429 stars were identified from 'The Catalog of…
In search of radio emission from exoplanets: GMRT observations of the binary system HD~41004
Mayank Narang, Manoj P, C. H. Ishwara Chandra +6
This paper reports Giant Metrewave Radio Telescope (GMRT) observations of the binary system HD 41004 that are among the deepest images ever obtained at 150~MHz and 400 MHz in the s…
Optical and near-IR photometric study of the open cluster NGC 637 and NGC 957
R. K. S. Yadav, Brijesh Kumar, A. Subramaniam +2
We present UBVRI CCD photometry in the region of the open clusters NGC 637 and NGC 957. The radii are found to be 4.2 arcmin and 4.3 arcmin. Their reddenings E(B-V) are 0.64+/-0.05…
A uGMRT search for radio emission from planets around evolved stars
Mayank Narang, P. Manoj, Ishwara Chandra +8
In this work, we present the results from a study using the Giant Meterwave Radio Telescope (GMRT) to search for radio {emission} from planets around three evolved stars namely $α…
Detection of high-frequency pulsation in WR 135: investigation of stellar wind dynamics
Subhajit Kar, Ramkrishna Das, Blesson Mathew +2
We report the detection of high-frequency pulsations in WR\,135 from short cadence (10\,minutes) optical photometric and spectroscopic time series surveys. The harmonics up to $6^{…
Studies of a possible new Herbig Ae/Be star in the open cluster NGC 7380
Blesson Mathew, D. P. K. Banerjee, N. M. Ashok +3
We present a study of the star 2MASS J22472238+5801214 with the aim of identifying its true nature which has hitherto been uncertain. This object, which is a member of the young cl…
Study of Classical Be stars in open clusters older than 100 Myr
Madhu Kashyap Jagadeesh, Blesson Mathew, K. T. Paul +3
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 s…
Analysis of Forbidden Neon Emission lines in HAeBe Stars using Spitzer IRS spectra
D. Akhila, Blesson Mathew, S. Nidhi +7
We analyzed high-resolution mid-infrared spectra of 78 well-known Herbig Ae/Be (HAeBe) stars using Spitzer InfraRed Spectrograph data, focusing on the detection of [Ne {\sc II}] an…
Clues on the X-ray emission mechanism of blazars PKS 2155304 and 3C 454.3 through polarization studies
Athira M Bharathan, C S Stalin, Sunder Sahayanathan +1
X-ray polarization measurable with the imaging X-ray Polarimetry Explorer (\textit{IXPE}) could constrain the long-debated leptonic versus hadronic origin of the high-energy compon…
Gas kinematics and dynamics of Carina Pillars: A case study of G287.76-0.87
Ngo-Duy Tung, Le Ngoc Tram, Archana Soam +4
We study the kinematics of a pillar, namely G287.76-0.87, using three rotational lines of CO(5-4), CO(8-7), CO(11-10), and a fine structure line of [OI] $63\,Î…
Discovery of an M-type Companion to the Herbig Ae Star V1787 Ori
R. Arun, Blesson Mathew, Sridharan Rengaswamy +4
The intermediate mass Herbig Ae star V1787 Ori is a member of the L1641 star-forming region in the Orion A molecular cloud. We report the detection of an M-type companion to V1787…
Probing the resolved K-S relation in nearby galaxies: Insights from UVIT and ALMA observations
K Sruthi, Sreeja S Kartha, Blesson Mathew +3
This study examines the resolved Kennicutt Schmidt (rKS) relation, defined as the connection between the star formation rate surface density (Sigma SFR) and the molecular gas mass…
Connecting the dots: Tracing the evolutionary pathway of Polar Ring Galaxies in the cases of NGC 3718, NGC 2685, and NGC 4262
Krishna R. Akhil, Sreeja S Kartha, Ujjwal Krishnan +4
Polar Ring Galaxies (PRGs) are a unique class of galaxies characterised by a ring of gas and stars orbiting nearly orthogonal to the main body. This study delves into the evolution…
Optical spectroscopy of Gaia detected protostars with DOT: can we probe protostellar photospheres?
Mayank Narang, Manoj Puravankara, Himanshu Tyagi +7
Optical spectroscopy offers the most direct view of the stellar properties and the accretion indicators. Standard accretion tracers, such as , , and, Ca II triplet lines,…
Determination of the size of the dust torus in H0507+164 through optical and infrared monitoring
Amit Kumar Mandal, Suvendu Rakshit, Kshama S. Kurian +6
The time delay between flux variations in different wavelength bands can be used to probe the inner regions of active galactic nuclei (AGN). Here, we present the first measurements…
Chandra X-ray Analysis of Herbig Ae/Be Stars
Hema Anilkumar, Blesson Mathew, V. Jithesh +4
Herbig Ae/Be (HAeBe) stars are intermediate-mass pre-main sequence stars, characterized by infrared excess and emission lines. They are observed to emit X-rays, whose origin is a m…
HI line analysis of Herbig Ae/Be stars using X-Shooter spectra
B. Shridharan, Blesson Mathew, R. Arun +1
Herbig Ae/Be stars are intermediate-mass pre-main sequence stars undergoing accretion through their circumstellar disk. The optical and infrared (IR) spectra of HAeBe stars show HI…