Site Map
Contacts
Follow us on Facebook Follow us on Twitter YouTube channel
Centro de Astrofísica da Universidade do Porto

Ring-like features around young B stars

M. S. N. Kumar, T. Velusamy, C. J. Davis, W. P. Varricatt, L. K. Dewangan

Abstract
Aims. To investigate the nature of two targets namely IRAS20293+3952 and IRAS05358+3843, which display, well defined H2 emission rings around young intermediate mass stars.
Methods. Hi-Res deconvolution of finely sampled 3.6–8.0 µm Spitzer-IRAC images of IRAS20293+3952 and IRAS05358+3843 are carried out. Continuum-subtracted 2.122 µm H2 1-0 S(1) narrow-band images of both targets and HK band spectrum of two main stars in IRAS20293+3952 is presented. The Spectral energy distibutions (SED) of the stars enclosed in the H2 rings are constructed using photometry from the literature and combining with newly obtained Spitzer-MIPS 70 µm photometry. The SEDs are modelled using a popular grid of radiative transfer models to obtain estimates of the star, disk and envelope physical parameters.
Results. The Hi-Res processed Spitzer-IRAC images and the the continuum-subtracted narrow-band images reveal ring-like structures surrounding isolated young B-type stars. The modelling attributes a mass and age of ∼7M and ∼0.1 Myr respectively to the young stars, in agreement with other observational indicators. The HK band spectra of I20293 display the Brackett series of HI recombination lines, localised on the young star in this source. The ring around I20293 appears as a single well defined ellipse with the inner parts shining brightly in the Spitzer broad band images and the outer parts displaying strong H2 emission. In the source I05358, at least two ring’s are found, one circumscribing the other. The emission in the Spitzer bands and the H2 emission are mostly coincident for the inner ring. The outer ring is visible partly in the Spitzer bands and partly in H2 emission. The rings in both the sources, I20293 and I05358, have diameters of ∼25000-30000AU. The envelope sizes estimated by the SED modelling is consistent with the size of the rings estimated using the imaging data. The spectrum of H2 ring in I20293 is suggestive of flourescent excitation. In the source I05358, the inner ring display a combination of PAH and H2 line emission with excess PAH emission closer to the star.

Keywords
stars: formation - stars: emission-line, stars: rotation - HII region

Astronomy and Astrophysics
Volume 519, Page A99_1
September 2010

>> PDF>> ADS>> DOI

Institute of Astrophysics and Space Sciences

Institute of Astrophysics and Space Sciences (IA) is a new but long anticipated research infrastructure with a national dimension. It embodies a bold but feasible vision for the development of Astronomy, Astrophysics and Space Sciences in Portugal, taking full advantage and fully realizing the potential created by the national membership of the European Space Agency (ESA) and the European Southern Observatory (ESO). IA resulted from the merging the two most prominent research units in the field in Portugal: the Centre for Astrophysics of the University of Porto (CAUP) and the Center for Astronomy and Astrophysics of the University of Lisbon (CAAUL). It currently hosts more than two-thirds of all active researchers working in Space Sciences in Portugal, and is responsible for an even greater fraction of the national productivity in international ISI journals in the area of Space Sciences. This is the scientific area with the highest relative impact factor (1.65 times above the international average) and the field with the highest average number of citations per article for Portugal.

Proceed on CAUP's website|Go to IA website