Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Exploring the dimming event of RW Aur A through multi-epoch
  VLT/X-Shooter spectroscopy   RW Aur A is a CTTS that has suddenly undergone three major dimming events
since 2010. We aim to understand the dimming properties, examine accretion
variability, and derive the physical properties of the inner disc traced by the
CO ro-vibrational emission at NIR wavelengths (2.3 mic).
  We compared two epochs of X-Shooter observations, during and after the
dimming. We modelled the rarely detected CO bandhead emission in both epochs to
examine whether the inner disc properties had changed. The SED was used to
derive the extinction properties of the dimmed spectrum and compare the
infrared excess between the two epochs. Lines tracing accretion were used to
derive the mass accretion rate in both states. The CO originates from a region
with physical properties of T=3000 K, N$_{CO}$=1x10$^{21}$ cm$^{-2}$ and
vsini=113 km/s. The extinction properties of the dimming layer were derived
with the effective optical depth ranging from teff 2.5-1.5 from the UV to the
NIR. The inferred mass accretion rate Macc is $1.5x 10^{-8}$ Msun/yr and $\sim
2x 10^{-8}$ Msun/yr after and during the dimming respectively. By fitting the
SED, additional emission is observed in the IR during the dimming event from
dust grains with temperatures of 500-700K. The physical conditions traced by
the CO are similar for both epochs, indicating that the inner gaseous disc
properties do not change during the dimming events. The extinction curve is
flatter than that of the ISM, and large grains of a few hundred microns are
thus required. When we correct for the observed extinction, Macc is constant in
the two epochs, suggesting that the accretion is stable and therefore does not
cause the dimming. The additional hot emission in the NIR is located at about
0.5 au from the star. The dimming events could be due to a dust-laden wind, a
severe puffing-up of the inner rim, or a perturbation caused by the recent
star-disc encounter.

18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
13
The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
28
The categories of this paper are: alg-geom
22
The categories of this paper are: chao-dyn
33
The categories of this paper are: plasm-ph
17
The categories of this paper are: q-fin
8
The categories of this paper are: hep-ex
3
The categories of this paper are: physics
24
The categories of this paper are: dg-ga