7 research outputs found
Merging Filaments and Hub Formation in the G083.09703.270 Molecular Complex
We uncover a hub-filament system associated with massive star formation in
the G083.09703.270. Diagnosed with simultaneous CO, CO, and
CO line observations, the region is found to host two distinct and
elongated filaments having separate velocity components, interacting spatially
and kinematically, that appear to have seeded the formation of a dense hub at
the intersection. A large velocity spread at the hub in addition to clear
bridging feature connecting the filaments in velocity are indicating merging of
filaments. Along the filaments axis, the velocity gradient reveals a global gas
motion with an increasing velocity dispersion inward to the hub signifying
turbulence. Altogether, the clustering of Class I sources, a high excitation
temperature, a high column density, and presence of a massive outflow at the
central hub suggest enhanced star formation. We propose that merging of
large-scale filaments and velocity gradients along filaments are the driving
factors in the mass accumulation process at the hub that have sequentially led
to the massive star formation. With two giant filaments merging to coincide
with a hub therein with ongoing star formation, this site serves as a benchmark
for the `filaments to clusters' star-forming paradigm.Comment: 12 pages, 7 figures, 1 table, accepted for publication in Ap
Dissecting the morphology of star forming complex S193
We have studied a star-forming complex S193 using near-infrared (NIR)
observations and other archival data covering optical to radio wavelengths. We
identified stellar clusters in the complex using the NIR photometric data and
estimated the membership and distance of the clusters. Using the mid-infrared
(MIR) and far-infrared (FIR) images, the distribution of the dust emission
around H\,{\sc ii} regions is traced in the complex. The column
density and temperature maps analysis reveal 16 cold dust clumps in the
complex. The H image and 1.4 GHz radio continuum emission map are
employed to study the ionised gas distribution and infer the spectral type and
the dynamical age of each H\,{\sc ii} region/ionised clump in the complex. The
CO(J =32) and CO(J =10) molecular line data hint at the
presence of two velocity components around [-43,-46] and [-47,-50] km/s, and
their spatial distribution reveals two overlapping zones toward the complex. By
investigating the immediate surroundings of the central cluster [BDS2003]57 and
the pressure calculations, we suggest that the feedback from the massive stars
seems responsible for the observed velocity gradient and might have triggered
the formation of the central cluster [BDS2003]57.}Comment: Accepted for publication in MNRAS, 20 pages, 15 figure
Post-outburst evolution of bonafide FUor V2493 Cyg: A Spectro-photometric monitoring
We present here the results of eight years of our near-simultaneous
optical/near-infrared spectro-photometric monitoring of bonafide FUor candidate
`V2493 Cyg' starting from 2013 September to 2021 June. During our optical
monitoring period (between October 16, 2015 and December 30, 2019), the V2493
Cyg is slowly dimming with an average dimming rate of 26.6 5.6
mmag/yr in V band. Our optical photometric colors show a significant reddening
of the source post the second outburst pointing towards a gradual expansion of
the emitting region post the second outburst. The mid infra-red colors, on the
contrary, exhibits a blueing trend which can be attributed to the brightening
of the disc due to the outburst. Our spectroscopic monitoring shows a dramatic
variation of the H line as it transitioned from absorption feature to
the emission feature and back. Such transition can possibly be explained by the
variation in the wind structure in combination with accretion. Combining our
time evolution spectra of the Ca II infra-red triplet lines with the previously
published spectra of V2493 Cyg, we find that the accretion region has
stabilised compared to the early days of the outburst. The evolution of the O I
7773 \AA~ line also points towards the stabilization of the
circumstellar disc post the second outburst.Comment: 34 pages, 12 figures, 6 tables, accepted for publication in Ap
Search for variable stars in the young open cluster Stock 18
We have carried out multi-epoch deep I band photometry of the open cluster Stock 18 to search for variable stars in star forming regions. In the present study, we report identification of 28 periodic and 165 non-periodic variables stars. The periods of most of the periodic variables are in between 2 to 20 hours and their magnitude varies between 0.05 to 0.6 mag. We have derived spectral energy distributions for 48 probable pre-main sequence variables and the average age and mass is found to be 2.7 ± 0.3 Myrs and 2.7 ± 0.2 M⊙, respectively