We present the results of HST/STIS and WFPC2 observations of LkHa 233 and its
environment. LkHa233 is a Herbig Ae/Be star with a collimated bipolar jet. We
investigate optical forbidden lines along the LkHa 233 jet to determine
physical parameters of this jet (electron density n_e, hydrogen ionisation
fraction x_e, electron temperature T_e, and mass density n_H). The knowledge of
these parameters allows us a direct comparison of a jet from a Herbig star with
those from T Tauri stars. The WFPC2 images in broad-band filters clearly show a
dark lane caused either by a circumstellar disk or a dust torus. In the
blueshifted lobe, n_e is close to or above the critical density for [SII] lines
(2.5x10^4 cm^-3) in the first arcsecond and decreases with distance from the
source. The ionisation x_e~0.2-0.6 gently rises for the first 500 AU of the
flow and shows two re-ionisation events further away from the origin. The T_e
varies along the flow between 10^4 K and 3x10^4 K. The (radial) outflow
velocities are ~ 80-160 km s^(-1), and they appear to increase with distance
from the source. In the redshifted lobe, T_e, n_e, x_e, and n_H are all lower
than in the blueshifted lobe, but have the same order of magnitude. All these
derived parameters are just beyond or at the upper limits of those observed for
classical T Tauri star jets. This may indicate that the flows from the higher
mass Herbig stars are indeed scaled-up examples of the same phenomenon as in T
Tauri stars.Comment: 21 pages, 5 figures, accepted for publication in the Astronomy and
  Astrophysic

Bacciotti, Francesca

Eislöffel, Jochen

Locatelli, Ugo

Melnikov, Stanislav Yu.

Ray, Thomas P.

Woitas, Jens

English

arXiv

Context. LkHα 233 is a Herbig Ae/Be star with a collimated bipolar jet. As such, it may be a high-mass analogue to the classical

T Tauri stars and their outflows.

Aims. We investigate optical forbidden lines along the LkHα 233 jet to determine physical parameters of this jet (electron density ne,

hydrogen ionisation fraction xe, electron temperature Te). The knowledge of these parameters allows us a direct comparison of a jet

from a Herbig star with those from T Tauri stars.

Methods. We present the results of HST/STIS and WFPC2 observations of LkHα 233 and its environment. These are the first observations

of this object with a spatial resolution of ≤0.  1 at optical wavelengths. Our STIS data provide spectroscopic maps that allow

us to reconstruct high angular resolution images of the bipolar jet from LkHα 233 covering the first ≈2000 AU from the star in the

blueshifted outflow lobe and ≈4000 AU in the redshifted lobe. These maps are analysed with a diagnostic code that yields ne, xe, Te,

and mass density nH within the jet.

Results. The WFPC2 images in broad-band filters clearly show a dark lane caused either by a circumstellar disk or a dust torus. The

circumstellar environment of LkHα 233 can be interpreted as a conical cavity that was cleared by a bipolar jet. In this interpretation,

the maximum of the optical and near-infrared brightness distribution does not coincide with the star itself which is, in fact, deeply

extincted. In the blueshifted lobe, ne is close to or above the critical density for [SII] lines (2.5 × 104 cm−3) in the first arcsecond

and decreases with distance from the source. The ionisation xe ≈ 0.2−0.6 gently rises for the first 500 AU of the flow and shows two

re-ionisation events further away from the origin. The electron temperature Te varies along the flow between 104 K and 3 × 104 K. The

nH is between 3 × 103 and 105 cm−3, and the mass flux ˙M ≈ 10−8−10−7 M  yr−1. The (radial) outflow velocities are ≈80−160 km s−1,

and they appear to increase with distance from the source. In the redshifted lobe, the excitation conditions are quite different: Te, ne,

xe, and nH are all lower than in the blueshifted lobe, but have the same order of magnitude.

Conclusions. All these derived parameters are just beyond or at the upper limits of those observed for classical T Tauri star jets. This

may indicate that the flows from the higher mass Herbig stars are indeed scaled-up examples of the same phenomenon as in T Tauri

stars

Melkinokov, S

Woitas, J

Eislöffel, J

Bacciotti, F

Locatelli, U

Ray, T

Archivio della Ricerca - Università di Roma Tor vergata

A HST study of the environment of the Herbig Ae/Be star LkHα 233 and its bipolar jet

Context. LkHα 233 is a Herbig Ae/Be star with a collimated bipolar
 jet. As such, it may be a high-mass analogue to the classical T Tauri stars
 and their outflows.
        Aims. We investigate optical forbidden lines along the LkHα 233 jet to
 determine physical parameters of this jet (electron density $n_{{\rm e}}$, hydrogen ionisation fraction $x_{{\rm e}}$, electron temperature Te). The knowledge of these parameters allows us a direct comparison of a jet from a Herbig star with those from T Tauri stars.
        Methods. We present the results of HST/STIS and WFPC2 observations of
 LkHα 233 and its environment. These are the first
 observations of this object with a spatial resolution of ≤$0\farcs1$ at
 optical wavelengths. Our STIS data provide spectroscopic maps that allow us
 to reconstruct high angular resolution images of the bipolar jet from
 LkHα 233 covering the first ≈2000 AU from the star in the
 blueshifted outflow lobe and ≈4000 AU in the redshifted
 lobe. These maps are analysed with a diagnostic code that yields
 $n_{{\rm e}}$, $x_{{\rm e}}$, Te, and mass density $n_{{\rm H}}$
 within the jet.
        Results. The WFPC2 images in broad-band filters clearly show a dark
 lane caused either by a circumstellar disk or a dust torus. The
 circumstellar environment of LkHα 233 can be interpreted as a conical
 cavity that was cleared by a bipolar jet. In this interpretation, the
 maximum of the optical and near-infrared brightness distribution does not
 coincide with the star itself which is, in fact, deeply extincted. In the
 blueshifted lobe, ne is close to or above the critical density for [SII] lines (2.5 $\times$ $10^4~{\rm cm}^{-3}$) in the first arcsecond and
 decreases with distance from the source. The ionisation $x_{\rm e} \approx 0.2{-}0.6$ gently rises for the first 500 AU of the flow and shows two
 re-ionisation events further away from the origin. The electron temperature $T_{{\rm e}}$ varies along the flow between $10^4~{\rm K}$ and 3 $\times$ $10^4~{\rm K}$. The $n_{{\rm H}}$ is between 3 $\times$ 103 and $10^5~{\rm cm}^{-3}$, and the mass flux $\dot{M}\approx 10^{-8}{-}10^{-7}~{M}_{\odot}~{\rm yr}^{-1}$. The (radial) outflow velocities
 are ≈$80{-}160~{\rm km}\,{\rm s}^{-1}$, and they appear to 
 increase with distance from the source. In the redshifted lobe, the excitation
 conditions are quite different: $T_{{\rm e}}$, $n_{{\rm e}}$,
 $x_{{\rm e}}$, and $n_{{\rm H}}$ are all lower than in the blueshifted
 lobe, but have the same order of magnitude.
        Conclusions. All these derived parameters are just beyond or at the upper limits of those
 observed for classical T Tauri star jets. This may indicate that the flows
 from the higher mass Herbig stars are indeed scaled-up examples of the same
 phenomenon as in T Tauri stars

S. Melnikov

J. Woitas

J. Eislöffel

F. Bacciotti

U. Locatelli

T. P. Ray

EDP Sciences OAI-PMH repository (1.2.0)

A HST study of the environment of the Herbig Ae/Be star

Context. LkHα 233 is a Herbig Ae/Be star with a collimated bipolar jet. As such, it may be a high-mass analogue to the classical
T Tauri stars and their outflows.
Aims. We investigate optical forbidden lines along the LkHα 233 jet to determine physical parameters of this jet (electron density ne,
hydrogen ionisation fraction xe, electron temperature Te). The knowledge of these parameters allows us a direct comparison of a jet
from a Herbig star with those from T Tauri stars.
Methods. We present the results of HST/STIS and WFPC2 observations of LkHα 233 and its environment. These are the first observations
of this object with a spatial resolution of ≤0.  1 at optical wavelengths. Our STIS data provide spectroscopic maps that allow
us to reconstruct high angular resolution images of the bipolar jet from LkHα 233 covering the first ≈2000 AU from the star in the
blueshifted outflow lobe and ≈4000 AU in the redshifted lobe. These maps are analysed with a diagnostic code that yields ne, xe, Te,
and mass density nH within the jet.
Results. The WFPC2 images in broad-band filters clearly show a dark lane caused either by a circumstellar disk or a dust torus. The
circumstellar environment of LkHα 233 can be interpreted as a conical cavity that was cleared by a bipolar jet. In this interpretation,
the maximum of the optical and near-infrared brightness distribution does not coincide with the star itself which is, in fact, deeply
extincted. In the blueshifted lobe, ne is close to or above the critical density for [SII] lines (2.5 × 104 cm−3) in the first arcsecond
and decreases with distance from the source. The ionisation xe ≈ 0.2−0.6 gently rises for the first 500 AU of the flow and shows two
re-ionisation events further away from the origin. The electron temperature Te varies along the flow between 104 K and 3 × 104 K. The
nH is between 3 × 103 and 105 cm−3, and the mass flux ˙M ≈ 10−8−10−7 M  yr−1. The (radial) outflow velocities are ≈80−160 km s−1,
and they appear to increase with distance from the source. In the redshifted lobe, the excitation conditions are quite different: Te, ne,
xe, and nH are all lower than in the blueshifted lobe, but have the same order of magnitude.
Conclusions. All these derived parameters are just beyond or at the upper limits of those observed for classical T Tauri star jets. This
may indicate that the flows from the higher mass Herbig stars are indeed scaled-up examples of the same phenomenon as in T Tauri
stars

Ray, T.

LOCATELLI, UGO

http://www.aanda.org/articles/aa/pdf/2008/19/aa8457-07.pdf

A HST study of the environment of the Herbig Ae/Be star LkHa 233 and its
  bipolar jet

A HST study of the environment of the Herbig Ae/Be star LkHa 233 and its bipolar jet

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