arXiv subjects

Blesson Mathew

Publications and source records attributed to Blesson Mathew.

At least 37 records · Page 2Linked to original sources

arXiv2024

Detection of high-frequency pulsation in WR 135: investigation of stellar wind dynamics

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 $6^{th}$ order are detected from the integrated photometric flux variations while the comparatively weaker $8^{th}$ harmonic is detected from the strengths of the emission lines. We investigate the driving source of the stratified winds of WR\,135 using the radiative transfer modeling code, CMFGEN, and find the physical conditions that can explain the propagation of such pulsations. From our study, we find that the optically thick sub-sonic layers of the atmosphere are close to the Eddington limit and are launched by the Fe-opacity. The outer optically thin super-sonic winds ($τ_{ross}=0.1-0.01$) are launched by the He\,$\textsc{ii}$ and C\,$\textsc{iv}$ opacities. The stratified winds above the sonic point undergo velocity perturbation that can lead to clumps. In the optically thin supersonic winds, dense clumps of smaller size ($f_{VFF}=0.27-0.3$, where $f_{VFF}$ is the volume filling factor) pulsate with higher-order harmonics. The larger clumps ($f_{VFF}=0.2$) oscillate with lower-order harmonics of the pulsation and affect the overall wind variability.

astro-ph.SR↗

arXiv2024

Detection of a new sample of Galactic White Dwarfs in the direction of the Small Magellanic Cloud

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 the UVIT point source catalogue towards SMC and crossmatching with Gaia DR3 data, we identified 43 single WDs (37 new detections), 13 new WD+main sequence (MS) candidates and 161 UV bright MS stars by analysing their Spectral Energy Distributions (SED). Using the WD evolutionary models, we determine the masses, effective temperatures, and cooling ages of these identified WDs. Masses of these WDs range from 0.2 to 1.3 M$_{\odot}$ and effective temperatures (T$_{eff}$) between 10000 K to 15000 K, with cooling ages spanning 0.1 to 2 Gyr. Notably, we detect hotter WDs compared to literature values, which is attributed to the sensitivity of UVIT. Furthermore, we report the detection of 20 new extremely low-mass (ELM) candidates from our analysis. Future spectroscopic studies of the ELM candidates will help us understand the formation scenarios of these exotic objects. Despite limitations in Gaia DR3 distance measurements for optically faint WDs, we provide a crude estimate of the WD space density within 1kpc as 1.3 $\times$ 10$^{-3}$ pc$^{-3}$, which is higher than previous estimates in the literature. Our results underscore the instrumental capabilities of UVIT and anticipate the forthcoming UV missions like INSIST for systematic WD discovery. Our methodology sets a precedent for future analyses in other UVIT fields to find more WDs and perform spectroscopic studies to verify their candidacy.

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arXiv2024

Insights on the Optical and Infrared Nature of MAXI J0709-159: Implications for High-Mass X-ray Binaries

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 sequence, based on comparisons with non-X-ray binary systems. In this paper, using color-magnitude diagram (CMD) analysis for High-Mass X-ray Binaries (HMXBs) and statistical t-tests, we found evidence supporting HD 54786's potential membership in both Be/X-ray binaries (BeXRBs) and supergaint X-ray binaries (SgXBs) populations of HMXBs. Hence, our study points towards dual optical characteristics of HD~54786, as an X-ray binary star and also belonging to a distinct evolutionary phase from BeXRB towards SgXB. Our further analysis suggests that MAXI J0709-159, associated with HD 54786, exhibits low-level activity during the current epoch and possesses a limited amount of circumstellar material. Although similarities with the previously studied BeXRB system LSI +61$^{\circ}$ 235 (Coe et al., 1994) are noted, continued monitoring and data collection are essential to fully comprehend the complexities of MAXI J0709-159 and its evolutionary trajectory within the realm of HMXBs.

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arXiv2024

Study of the Balmer decrements for Galactic classical Be stars using the Himalayan Chandra Telescope of India

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 Telescope (HCT) facility located at Ladakh, India. This paper presents our further exploration of these stars to estimate the electron density in their discs. Our study using Balmer decrement values indicate that their discs are generally optically thick in nature with electron density (n_e) in their circumstellar envelopes (CEs) being in excess of 10^13 cm^-3 for around 65% of the stars. For another 19% stars, the average n_e in their discs probably range between 10^12 cm^-3 and 10^13 cm^-3. We noticed that the nature of the Hα and H\b{eta} line profiles might not influence the observed Balmer decrement values (i.e. D_34 and D_54) of the sample of stars. Interestingly, we also found that around 50% of the Be stars displaying D_34 greater than 2.7 are of earlier spectral types, i.e. within B0 -B3.

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arXiv2024

Beyond the Rings: Polar Ring Galaxy NGC 4262 and its Globular Cluster System

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 study explores the globular cluster system (GCS) and its properties in the nearest PRG, NGC4262, serving as a pilot investigation to study GCS in nearby PRGs. We utilize wide and deep field observations of the CFHT as part of the NGVS to investigate the GCS of NGC4262. We presented the first optical image of NGC4262 with an optically faint ring component. The photometric analysis of the GCS displays a distinct color bimodality. We estimate the total number of GCs for NGC4262 to be 266$\pm$16 GCs with a specific frequency of 4.2$\pm$0.8 and a specific mass of 0.23$\pm$0.01, which is relatively high compared to other galaxies of similar mass and environmental conditions. The spatial and azimuthal distributions of subpopulations reveal strong evidence of previous interactions within the host galaxy. The color distribution of GCS in NGC4262 shows a gradient of -0.05$\pm$0.01 within 5.5\arcmin, supporting the notion of past interactions and evolutionary transitions. PRG NGC4262 conforms to the overall trend of the GCS mass with respect to the halo mass. Furthermore, our investigation of the global scaling relations between GCS and host galaxy parameters provides further support for the hypothesis that PRGs are an intermediate phase connecting ongoing mergers and quiescent galaxies.

astro-ph.GA↗

arXiv2024

Chandra X-ray Analysis of Herbig Ae/Be Stars

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 matter of discussion and not settled yet. X-ray emission is not expected in HAeBe stars, as they lack the sub-surface convective zone. In this study, we retrieved observations from the Chandra archive for 62 HAeBe stars, among which 44 sources (detection fraction $\sim$71%) were detected in X-rays, with 7 being new detections. We use this sample as a test bed to conduct a comparative analysis of the X-ray properties of HAeBe stars and their low-mass counterparts, T Tauri Stars (TTSs). Further, we compare the X-ray properties of HAeBe stars and TTSs with optical and IR properties to constrain the X-ray emission mechanism in HAeBe stars. We found no correlation between X-ray emission and disk properties of HAeBe stars, confirming that X-rays are not related to accretion shocks. About 56% of HAeBe stars without any known sub-arcsec companions have lower plasma temperatures (kT $\leq$ 2 keV). We observe flaring/variability in HAeBe stars with confirmed low-mass companions. These stars show plasma temperatures > 2 keV, similar to TTSs. Guided by this information we discuss the role of a T Tauri companion for X-ray emission seen in our sample of HAeBe stars. From the results obtained in this paper, we suggest that X-ray emission from HAeBe stars may not be related to accretion shocks or hidden TTS, but rather can be due to magnetically driven coronal emission.

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arXiv2024

Gas kinematics and dynamics of Carina Pillars: A case study of G287.76-0.87

We study the kinematics of a pillar, namely G287.76-0.87, using three rotational lines of $^{12}$CO(5-4), $^{12}$CO(8-7), $^{12}$CO(11-10), and a fine structure line of [OI] $63\,μ$m Southern Carina observed by SOFIA/GREAT. This pillar is irradiated by the associated massive star cluster Trumpler 16, which includes $η$~Carina. Our analysis shows that the relative velocity of the pillar with respect to this ionization source is small, $\sim 1\,\rm km\,s^{-1}$, and the gas motion in the tail is more turbulent than in the head. We also performed analytical calculations to estimate the gas column density in local thermal equilibrium (LTE) conditions, which yields $N_{\rm CO}$ as $(\sim 0.2 -5)\times 10^{17}\,\rm cm^{-2}$. We further constrain the gas's physical properties in non-LTE conditions using RADEX. The non-LTE estimations result in $n_{\rm H_{2}} \simeq 10^{5}\,\rm cm^{-3}$ and $N_{\rm CO} \simeq 10^{16}\,\rm cm^{-2}$. We found that the thermal pressure within the G287.76-0.87 pillar is sufficiently high to make it stable for the surrounding hot gas and radiation feedback if the winds are not active. While they are active, stellar winds from the clustered stars sculpt the surrounding molecular cloud into pillars within the giant bubble around $η$~Carina.

astro-ph.GA↗

arXiv2024

Optical Spectroscopy of Classical Be Stars in Old Open Clusters

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 older than 100 Myr. We found that the H alpha emission strength of most of the stars is less than 40 Angstrom, in agreement with previous studies. Our analysis further suggests that one of the stars, KW97 35 12, might be a weak H alpha emitter in nature, showing H alpha equivalent width of negative 0.5 Angstrom. Interestingly, we also found that the newly detected classical Be star LS III 47 37b might be a component of the possible visual binary system LS III 47 37, where the other companion is also a classical Be star. Hence, the present study indicates the possible detection of a binary Be system. Moreover, it is observed that all 16 stars exhibit a lesser number of emission lines compared to classical Be stars younger than 100 Myr. Furthermore, the spectral type distribution analysis of B type and classical Be stars for the selected clusters points out that the existence of CBe stars can depend on the spectral type distribution of B type stars present in these clusters.

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arXiv2024

A uGMRT search for radio emission from planets around evolved stars

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 $α$~Tau, $β$~UMi, and $β$~Gem. Both $α$~Tau and $β$~UMi host massive $\sim$ 6 $M_J$ mass planets at about $\sim$1.4 au from the central star, while $β$~Gem is host to a 2.9 $M_J$ mass planet at 1.7 au from the host star. We observe $α$~Tau and $β$~ UMi at two u(upgraded)GMRT bands; band~3 (250-500~MHz) and band~4 (550-900~MHz). We also analyzed the archival observations from $β$ Gem at 150~MHz from GMRT. We did not detect any radio signals from these systems. At 400~MHz, the 3$σ$ upper limit is 87 $μ$Jy/beam for $α$~Tau~{b} and 77.4 $μ$Jy/beam for $β$~UMi~{b}. From our observations at 650~MHz, we place a 3$σ$ upper limit of 28.2 $μ$Jy/beam for $α$~Tau~b and 33.6 $μ$Jy/beam for $β$~UMi~b. For $β$ Gem b, at 150~MHz, we place an upper limit of 2.5 mJy. At 400~MHz and 650~MHz, our observations are the deepest radio images for any exoplanetary system.

astro-ph.EP↗

arXiv2024

Multi-wavelength spectral modelling of the candidate neutrino blazar PKS 0735+178

The BL Lac object PKS 0735+178 was in its historic $γ$-ray brightness state during December 2021. This period also coincides with the detection of a neutrino event IC211208A, which was localized close to the vicinity of PKS 0735+178. We carried out detailed $γ$-ray timing and spectral analysis of the source in three epochs (a) quiescent state ($E_{1}$), (b) moderate activity state ($E_{2}$) and (c) high activity state ($E_{3}$) coincident with the epoch of neutrino detection. During the epoch of neutrino detection ($E_{3}$), we found the largest variability amplitude of 95%. The $γ$-ray spectra corresponding to these three epochs are well fit by the power law model and the source is found to show spectral variations with a softer when brighter trend. In the epoch $E_{3}$, we found the shortest flux doubling/halving time of 5.75 hrs. Even though the spectral energy distribution in the moderate activity state and in the high activity state could be modeled by the one-zone leptonic emission model, the spectral energy distribution in the quiescent state required an additional component of radiation over and above the leptonic component. Here we show that a photo-meson process was needed to explain the excess $γ$-ray emission in the hundreds of GeV which could not be accounted for by the synchrotron self-Compton process.

astro-ph.HE↗

arXiv2024

Disentangling the association of PAH molecules with star formation : Insights from JWST and UVIT

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 ultraviolet (UV) emission from the young massive stars directly traces the star formation activity in a galaxy. The James Webb Space Telescope (JWST), along with the UltraViolet Imaging Telescope (UVIT), opened up a new window of opportunity to make a better understanding of the properties of the PAH molecules associated with the star-forming regions. In this study, we investigate how the resolved scale properties of PAH molecules in nearby galaxies are affected by star-formation. We analyze the PAH features observed at 3.3, 7.7, and 11.3 μm using F335M, F770W, and F1130W images obtained from JWST. Additionally, we utilize UVIT images to assess the star formation associated with these PAH emitting regions. Our study focuses on three galaxies, namely NGC 628, NGC 1365, and NGC 7496, selected based on the availability of both JWST and UVIT images. Based on the resolved scale study on the PAH bright regions using JWST and UVIT images, we found that the fraction of ionized PAH molecules is high in the star-forming regions with high ΣSFR. We observed that emission from smaller PAH molecules is more in the star-forming regions with higher ΣSFR. Our study suggests that the PAH molecules excited by the photons from SF regions with higher ΣSFR are dominantly smaller and ionized molecules. UV photons from the star-forming regions could be the reason for a higher fraction of the ionized PAHs. We suggest that the effect of high temperature in the star-forming regions and the formation of smaller PAH molecules in the star-forming regions might also be resulting in the higher fraction of emission in the F335MPAH band.

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arXiv2023

Investigation of the correlation between optical and $γ$-ray flux variation in the blazar Ton 599

The correlation between optical and $γ$-ray flux variations in blazars reveals a complex behaviour. In this study, we present our analysis of the connection between changes in optical and $γ$-ray emissions in the blazar Ton 599 over a span of approximately 15 years, from August 2008 to March 2023. Ton 599 reached its highest flux state across the entire electromagnetic spectrum during the second week of January 2023. To investigate the connection between changes in optical and $γ$-ray flux, we have designated five specific time periods, labeled as epochs A, B, C, D, and E. During periods B, C, D, and E, the source exhibited optical flares, while it was in its quiescent state during period A. The $γ$-ray counterparts to these optical flares are present during periods B, C, and E, however during period D, the $γ$-ray counterpart is either weak or absent. We conducted a broadband spectral energy distribution (SED) fitting by employing a one-zone leptonic emission model for these epochs. The SED analysis unveiled that the optical-UV emission primarily emanated from the accretion disk in quiescent period A, whereas synchrotron radiation from the jet dominated during periods B, C, D, and E. Diverse correlated patterns in the variations of optical and $γ$-ray emissions, like correlated optical and $γ$-ray flares, could be accounted for by changes in factors such as the magnetic field, bulk Lorentz factor, and electron density. On the other hand, an orphan optical flare could result from increased magnetic field and bulk Lorentz factor.

astro-ph.HE↗

arXiv2023

Identifying the population of T-Tauri stars in Taurus: UV-optical synergy

With the third data release of the Gaia mission $Gaia$ DR3 with its precise photometry and astrometry, it is now possible to study the behaviour of stars at a scale never seen before. In this paper, we developed new criteria to identify T-Tauri stars (TTS) candidates using UV and optical CMDs by combining the GALEX and Gaia surveys. We found 19 TTS candidates and 5 of them are newly identified TTS in the Taurus Molecular Cloud (TMC), not catalogued before as TMC members. For some of the TTS candidates, we also obtained optical spectra from several Indian telescopes. We also present the analysis of the distance and proper motion of young stars in the Taurus using data from $Gaia$ DR3. We found that the stars in Taurus show a bimodal distribution with distance, having peaks at $130.17_{-1.24}^{1.31}$ pc and $156.25_{-5.00}^{1.86}$ pc. The reason for this bimodality, we think, is due to the fact that different clouds in the TMC region are at different distances. We further show that the two populations have similar ages and proper motion distribution. Using the $Gaia$ DR3 colour-magnitude diagram, we show that the age of Taurus is consistent with 1 Myr.

astro-ph.SR↗

arXiv2023

DES J024008.08-551047.5:A new member of the polar ring galaxy family

During the visual observations of optical imaging data obtained from the DECaLS, a serendipitous discovery emerged, revealing the presence of a ringed galaxy, DES J024008.08-551047.5 (DJ0240). We performed one dimensional isophotal and two-dimensional GALFIT analysis to confirm the orthogonal nature of the ring galaxy and identify distinct components within the host galaxy. We discovered the galaxy DJ0240 as a potential PRG candidate with a ring component positioned almost perpendicular to the host galaxy. The position angles of the ring and host components have been determined to be 80 and 10 degrees, respectively, indicating that they are nearly orthogonal to each other. We observed that the ring component extends three times more than the host galaxy and shows a distinct colour separation, being bluer than the host. The estimated g - r colour values of host and ring components are 0.86+/-0.02 and 0.59+/-0.10 mag, respectively. The colour value of the ring component is similar to typical spiral galaxies. The host galaxy`s colour and the presence of a bulge and disk components indicate the possibility of the host galaxy being a lenticular type. Based on the comparison of photometric properties between the PRGs and other ring-type galaxies (RTGs), our findings reveal a subtle, yet noticeable, colour difference between the host and ring components. We observed that both host and ring components of DJ0240 align more closely with PRGs than with RTGs. Furthermore, we compared the sersic index values of the ring component (nring) of galaxy DJ0240 with a selected sample of PRGs and Hoag-type galaxies. The results showed DJ0240 had a remarkably low nring value of 0.13, supporting the galaxy`s classification as a PRG. Hence, we suggest that the ring galaxy DJ0240 is a highly promising candidate for inclusion in the family of PRGs.

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arXiv2023

What drives the wheels of evolution in NGC 1512? A UVIT study

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 action of bar, bulge and spiral structures. Ongoing star formation in spiral galaxies can be affected by these processes. Studying the star formation in the galaxy can give insights into the evolution of the galaxy. The ongoing interaction between barred-spiral galaxy NGC 1512 and its satellite NGC 1510 offers an opportunity to investigate how galactic interactions and the presence of a galactic bar influence the evolution of NGC 1512. We aim to understand the recent star formation activity in the galaxy pair and thus gain insight into the evolution of NGC 1512. The UltraViolet Imaging Telescope (UVIT) onboard AstroSat enables us to study the star-forming regions in the galaxy with a spatial resolution of ~85 pc in the galaxy rest frame. We identified and studied 175 star-forming regions in UVIT FUV image of NGC 1512 and correlated with the neutral hydrogen (HI) distribution. We detected localized regions of star formation enhancement and distortions in the galactic disk. This is consistent with HI distribution in the galaxy. This is evidence of past and ongoing interactions affecting the star formation properties of the galaxy. We studied the properties of the inner ring. We find that the regions of the inner ring show maximum star formation rate density (log(SFRDmean[Msolaryr-1kpc-2]) ~ -1.7) near the major axis of the bar, hinting at a possible crowding effect in these regions. The region of the bar in the galaxy is also depleted of UV emission. This absence suggests that the galactic bar played an active role in the redistribution of gas and quenching of star formation inside identified bar region. Hence, we suggest that both the secular and environmental factors might influence the evolution of NGC 1512.

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arXiv2023

Optical spectroscopy of Gaia detected protostars with DOT: can we probe protostellar photospheres?

Optical spectroscopy offers the most direct view of the stellar properties and the accretion indicators. Standard accretion tracers, such as $Hβ$, $Hα$, and, Ca II triplet lines, and most photospheric features, fall in the optical wavelengths. However, these tracers are not readily observable from deeply embedded protostars because of the large line of sight extinction (Av $\sim$ 50-100 mag) toward them. In some cases, however, it is possible to observe protostars at optical wavelengths if the outflow cavity is aligned along the line-of-sight that allows observations of the photosphere, or the envelope is very tenuous and thin such that the extinction is low. In such cases, we can not only detect these protostars at optical wavelengths but also follow up spectroscopically. We have used the HOPS catalog (Furlan et al. 2016) of protostars in Orion to search for optical counterparts for protostars in the Gaia DR3 survey. Out of the 330 protostars in the HOPS sample, an optical counterpart within 2" is detected for 62 of the protostars. For 17 out of 62 optically detected protostars, we obtained optical spectra { (between 5500 to 8900 $Å$) using the Aries-Devasthal Faint Object Spectrograph \& Camera (ADFOSC) on the 3.6-m Devasthal Optical Telescope (DOT) and Hanle Faint Object Spectrograph Camera (HFOSC) on 2-m Himalayan Chandra Telescope (HCT)}. We detect strong photospheric features, such as the TiO bands in the spectra {(of 4 protostars)}, hinting that photospheres can form early on in the star formation process. We further determined the spectral types of protostars, which show photospheres similar to a late M-type. Mass accretion rates derived for the protostars are similar to those found for T-Tauri stars, in the range of 10$^{-7}$ to 10$^{-8}$ $M_\odot$/yr.

astro-ph.SR↗

arXiv2023

Spectroscopic study of Herbig Ae/Be stars in the Galactic Anti-center region from LAMOST DR5

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 (LAMOST) survey program. Emission lines of hydrogen belonging to the Balmer and Paschen series, and metallic lines of species such as FeII, OI, CaII triplet are identified. A moderate correlation is observed between the emission strengths of H$α$ and FeII 5169 Å, suggesting a possible common emission region for FeII lines and one of the components of H$α$. We explored a technique for the extinction correction of the HAeBe stars using diffuse interstellar bands present in the spectrum. We estimated the stellar parameters such as age and mass of these HAeBe stars, which are found to be in the range 0.1 -- 10 Myr and 1.5 -- 10 $M_{\odot}$, respectively. We found that the mass accretion rate of the HAeBe stars in the Galactic anti-center direction follows the relation $\dot{M}_{acc}$ $\propto$ $M_{*}^{3.12^{+0.21}_{-0.34}}$, which is similar to the relation derived for HAeBe stars in other regions of the Galaxy. The mass accretion rate of HAeBe stars is found to have a functional form of $\dot{M}_{acc} \propto t^{-1.1 \pm 0.2}$ with age, in agreement with previous studies.

astro-ph.SR↗

arXiv2023

Disentangling the two sub-populations of early Herbig Be stars using VLT/X-Shooter spectra

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 main-sequence phase, studying the evolution of the circumstellar medium around these stars can be a cumbersome exercise. In this work, we study the sample of early (B0-B5) HBe stars using the correlation between H$α$ emission strength and near--infrared excess, complemented by the analysis of various emission features in the X-Shooter spectra. We segregate the sample of 37 early HBe stars based on the median values of H$α$ equivalent width (EW) and near--infrared index (n(J$-$H)) distributions. The stars with |H$α$ EW| $>$ 50 Å and n(J$-$H) $>$ -2 are classified as intense HBe stars and stars with |H$α$ EW| $<$ 50 Å and n(J$-$H) $<$ -2 as weak HBe stars. Using the VLT/X--Shooter spectra of five intense and eight weak HBe stars, we visually checked for the differences in intensity and profiles of various H{\sc I} and metallic emission lines commonly observed in Herbig stars. We propose that the intense HBe stars possess an inner disk close to the star (as apparent from the high near-infrared excess) and an active circumstellar environment (as seen from high H$α$ EW value and presence of emission lines belonging to Fe{\sc II}, Ca{\sc II}, O{\sc I} and [O{\sc I}]). However, for weak HBe stars, the inner disk has cleared, and the circumstellar environment appears more evolved than for intense HBe stars. Furthermore, we compiled a sample of $\sim$58,000 emission-line stars published in \textit{Gaia DR3} to identify more intense HBe candidates. Further spectroscopic studies of these candidates will help us to understand the evolution of the inner ($\sim$a few au) disk in early HBe stars.

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