Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Variability of the transitional T Tauri star T Chamaeleontis   We characterize the physical properties of T Chamaeleontis, a transitional T
Tauri star showing UX Ori-type variability, and of its associated disc, and
probe possible effects of disc clearing processes. Different spectral
diagnostics are examined, based on a rich collection of optical high- and
low-resolution spectra. We determine radial and projected rotational
velocities, and measure equivalent widths of the Li I (6708 A) line and of the
most prominent emission lines (e.g. Ha, Hb and [OI] 6300A); we analyse shape
changes of photospheric lines via bisector-method, while variability in Ha and
Hb is inspected through line-profile correlation matrices. The strength of the
Ha and Hb emission is highly variable and well correlated with that of the [OI]
lines, as well as with Av variations of over three magnitudes. Variations up to
nearly 10 km/s in the radial velocity of the star are measured on analogous
time-scale, but with no apparent periodicity. SED modelling confirms the
existence of a gap in the disc. Variable circumstellar extinction is pointed
out as responsible for the conspicuous variations observed in the stellar
continuum flux and for concomitant changes in the emission features by contrast
effect. Clumpy structures, incorporating large dust grains and orbiting the
star within a few tenths of AU, obscure episodically the star and, eventually,
part of the inner circumstellar zone, while the bulk of the hydrogen lines
emitting zone and outer low-density wind region traced by the [OI] remain
unaffected. Coherently with this scenario, the detected radial velocity changes
are also explainable in terms of clumpy materials transiting and partially
obscuring the star.

18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc
0
The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph
13
The categories of this paper are: quant-ph
2
The categories of this paper are: math
11
The categories of this paper are: hep-lat
8
The categories of this paper are: hep-ex
22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th