Blesson Mathew

Blesson Mathew
Tata Institute of Fundamental Research | TIFR · Department of Astronomy and Astrophysics

About

55
Publications
3,240
Reads
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232
Citations
Introduction
Skills and Expertise
Additional affiliations
January 2013 - August 2015
Swinburne University of Technology
Position
  • Sessional Staff
June 2010 - June 2012
Physical Research Laboratory
Position
  • PostDoc Position
January 2004 - January 2010
Indian Institute of Astrophysics
Position
  • PhD Student

Publications

Publications (55)
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
We report the survey and discovery of C60 (buckminsterfullerene) in the circumstellar medium of six Herbig Ae/Be stars using archival Spitzer IRS low-resolution spectra. The two prominent infrared vibrational modes of C60 bands at 17.4 µm and 18.9 µm are detected in the spectra of seven sources. In the case of two Herbig Ae/Be stars, we report the...
Article
We present a catalog of 3339 hot emission-line stars (ELSs) identified from 451 695 O, B and A type spectra, provided by LAMOST Data Release 5 (DR5). We developed an automated Python routine that identified 5437 spectra having a peak between 6561 and 6568 Å. False detections and bad spectra were removed, leaving 4138 good emission-line spectra of 3...
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,...
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
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 routine that identified 5437 spectra having a peak between 6561 and 6568~\AA. False detections and bad spectra were removed, leaving 4138 good emission-line spectra of 3339...
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
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 of 798±9 pc, and has a ”cavity” associated with it. We found that the B0V star HD 216658, which is astrometrically associated with IL Cep, is at the center of the cavity...
Preprint
Full-text available
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 of 798$\pm$9 pc, and has a "cavity" associated with it. We found that the B0V star HD 216658, which is astrometrically associated with IL Cep, is at the center of the ca...
Article
Full-text available
We report the first systematic study to identify and characterize a sample of classical Ae stars in the Galaxy. The spectra of these stars were retrieved from the A-star catalog using the Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST) survey. We identified the emission-line stars in this catalog from which 159 are confirmed as c...
Preprint
Full-text available
We report the first systematic study to identify and characterize a sample of classical Ae stars in the Galaxy. The spectra of these stars were retrieved from the A-star catalog using the Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST) survey. We identified the emission-line stars in this catalog from which 159 are confirmed as c...
Preprint
Full-text available
In this study, we analyze the emission lines of different species present in 118 Galactic field classical Be stars in the wavelength range of 3800 - 9000 \AA. We re-estimated the extinction parameter (A$_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...
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.
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
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...
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
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 speckle interferometric studies whereas NGC 6834(2) may possibly be a γ Cas-like variable. Infrared photometry and spectroscopy from the United Kingdom Infrared Telescope (U...
Article
Full-text available
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. Combining results from our earlier studies with the present observations, it is shown that the equivalent widths and line fluxes of the prominent HI and HeI lines anti-correlate...
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
Full-text available
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 astronomical sources but surprisingly were very prominent in the spectra of two well-known, nova-like variables (V838 Mon and V4332 Sgr) thereby motivating us to explore the physica...
Article
Full-text available
The possibility of the Ly{\beta} fluorescence mechanism being operational in classical Be stars and thereby contributing to the strength of the OI 8446 {\AA} line has been recognized for long. However this supposition needs to be quantified by comparing observed and predicted OI line ratios. In the present work, optical and near-infrared spectra of...
Article
Photometric and spectroscopic results are presented for the Be star X Per/HD 24534 from near-infrared (near-IR) monitoring in 2010–2011. The star is one of a sample of selected Be/X-ray binaries being monitored by us in the near-IR to study correlations between their X-ray and near-IR behaviour. Comparison of the star’s present near-IR magnitudes w...
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
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 cluster NGC 7380, has been variously proposed to be a Be star, a D-type symbiotic and a Herbig Ae/Be star in separate studies. Here we present optical spectroscopy, near-IR...
Article
Full-text available
The spectroscopic observations were done using the Himalayan Faint Object Spectrograph Camera (HFOSC) available with the 2.0m Himalayan Chandra Telescope (HCT), located at Hanle and operated by the Indian Institute of Astrophysics (IIA). (2 data files).
Article
Full-text available
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 day orbital period. This observation campaign is a part of the monitoring programme of selective Be/X-ray binary systems aimed at understanding the X-ray and near-IR prope...
Article
Blazar S5 0716+714 (PKS 0716+71) is highly variable at short and long term timescales in all energy regimes. Recently (ATel # 3700), it is reported to be in flaring state in optical and gamma-rays by Blinov et al (2011). Source is shown to have brightened by one magnitude during three nights with R~ 12.5 on 2011.10.21UT23. Following ATel#3700, we o...
Article
Full-text available
We present a spectroscopic study of 150 Classical Be stars in 39 open clusters using medium resolution spectra in the wavelength range 3800 - 9000 \AA. One-third of the sample (48 stars in 18 clusters) has been studied for the first time. All these candidates were identified from an extensive survey of emission stars in young open clusters using sl...
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...
Article
Following the Fermi LAT detection of a flare in Gamma-Rays (Atel #3196) and the near-infrared observations of the ongoing NIR flare of BZU J0742+5444 (GB6 J0742+5444) (Atel #3261), we observed the intermediate redshift quasar in J and H-bands on 2011 April 10 (MJD = 55661) with the 1.2m telescope (+ NICS with HAWAII-1 infrared array) at Gurushikhar...
Article
Full-text available
Emission-line stars in young open clusters are identified to study their properties, as a function of age, spectral type and evolutionary state. 207 open star clusters were observed using the slitless spectroscopy method and 157 emission stars were identified in 42 clusters. We have found 54 new emission-line stars in 24 open clusters, out of which...
Article
Classical Be stars (CBe) are rapidly rotating (V_{{sin}i} ˜ 300 km s^{-1}) B-type stars with equatorial circumstellar decretion disks, the production of which is under debate. The Be phenomenon can be understood through the analysis of hydrogen recombination lines in the infrared spectral region. J-band spectroscopy of Be stars is one of the less s...
Article
Following the report of possible outburst of the star FS Aurigae (AAVSO Special Notice #226), the photometric observations were carried out in near-infrared J, H, and K-bands on 2010 December 5.89 UT, 6.87 and 15.86 UT using the 1.2 m Mt. Abu telescope operated by Physical Research Laboratory, Ahmedabad, India. The photometric observations were car...
Article
Following the report of near-infrared (NIR) flaring of the Blazar PMN J2345-1555 by Carraso et al. (ATel #2977), the source was observed in J, H and Ks bands at the MIRO (Mount Abu Infra-Red Observatory) on 28th and 30th October 2010. The source continues to be in the flaring phase. On 28th October 2010 (UT - 17:30), the NIR flux was determined to...
Article
Following the report of increase in the X-ray flux of the Be/X-ray binary pulsar A0535+262 since 2010 October 14 (Atel #2970), the photometric and spectroscopic observations were carried out in near-infrared J, H, and K-bands on 2010 October 28.9 UT and 31.9 UT using the 1.2 m Mt. Abu telescope operated by Physical Research Laboratory, Ahmedabad, I...
Article
Full-text available
We present the spectroscopic study of 5 Herbig Ae/Be stars in young open clusters. These are identified from a survey of emission-line stars in young open clusters. The Herbig Ae/Be stars are found to show a linear correlation in H_alpha equivalent width versus reddening corrected (H-K_s) colour plot, with a clear offset from the distribution of Cl...
Article
A spectroscopic study of 152 Classical Be stars in 42 young open clusters was performed using medium resolution spectra in 3700-9000 Å range, to understand the Be phenomenon. The Balmer decrement is found to have a bimodal distribution which is correlated with the nature of H_beta profile. Classical Be stars with higher Balmer decrement (76%) were...
Article
We present UBVRI CCD photometry in the region of the open clusters NGC 637 and 957. The radii are found to be 4.2 and 4.3 arcmin. Their reddenings E(B−V) are 0.64 ± 0.05 and 0.71 ± 0.05 mag and their distances, from main-sequence fitting are 2.5 ± 0.2 and 2.2 ± 0.2 kpc. Comparison with Z= 0.02 isochrones leads to an age of 10 ± 5 Myr for both clust...
Article
Full-text available
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 observed using slitless spectroscopy method and 157 emission stars were identified in 42 clusters. We have found 54 new emission-line stars in 24 open clusters, out of whi...
Article
Full-text available
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 literature are combined with the 2MASS data to identify the pre-main sequence (pre-MS) stars as stars with near IR excess. We identified 93 pre-MS stars and 9 stars with H$_\alpha...
Article
We identified about 150 stars with H-alpha in emission in 44 open clusters. To study their detailed characteristics, we obtained spectra of these stars in the 3500 -- 9200 AA range. Apart from Balmer lines in emission, spectra of these stars also show Helium, Iron, Calcium triplet, Pashen and Oxygen lines in emission. We have obtained double peaked...
Article
NGC 6834 is a poorly studied cluster and known to be 80 Myr old. We detect 4 early type stars with Halpha in emission, which is a surprising result as these type of stars are not expected in a cluster of this age. We present a complete analysis of the cluster NG 6834 based on UBV CCD data, spectra of 4 stars with Halpha in emission (both obtained u...
Article
Full-text available
We present a photometric and spectroscopic study of the young open cluster NGC 7419, which is known to host a large number of classical Be stars for reasons not well understood. Based on CCD photometric observations of 327 stars in UBV passbands, we estimated the cluster parameters as, reddening [E(B−V)]= 1.65 ± 0.15 mag and distance = 2900 ± 400 p...
Article
Full-text available
NGC 225 is believed to be a 120 Myr old open cluster located at tilda 650 pc. Eight stars with H alphaemission are found to be located around the cluster, of which two are probable Herbig Be stars, indicating a very young age for the cluster. To explore whether the Herbig Be stars, which are pre- main sequence (PMS) stars are part of this cluster,...
Chapter
Full-text available
We summarize a study of emission-line stars in young open clusters. The study was done in two phases. The first phase was the survey, where the emission stars in young open clusters were identified using the slitless spectral images. The identified emission stars were then studied in detail using their slit spectra in the 3700–9000 °A range. The re...

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