6 research outputs found
Herschel Planetary Nebula Survey (HerPlaNS) - First Detection of OH+ in Planetary Nebulae
We report the first detections of OH emission in planetary nebulae (PNe).
As part of an imaging and spectroscopy survey of 11 PNe in the far-IR using the
PACS and SPIRE instruments aboard the Herschel Space Observatory, we performed
a line survey in these PNe over the entire spectral range between 51 and
672m to look for new detections. OH rotational emission lines at
152.99, 290.20, 308.48, and 329.77m were detected in the spectra of three
planetary nebulae: NGC 6445, NGC 6720, and NGC 6781. Excitation temperatures
and column densities derived from these lines are in the range of 27 to 47 K
and 210 to 4 10 cm, respectively. In PNe,
the OH+ rotational line emission appears to be produced in the
photodissociation region (PDR) in these objects. The emission of OH+ is
observed only in PNe with hot central stars (T > 100000 K), suggesting
that high-energy photons may play a role in the OH+ formation and its line
excitation in these objects, as it seems to be the case for ultraluminous
galaxies.Comment: 9 pages, 7 figures; accepted for publication in A&
The Red Rectangle: Its Shaping Mechanism and its Source of Ultraviolet Photons
The proto-planetary Red Rectangle nebula is powered by HD 44179, a
spectroscopic binary (P = 318 d), in which a luminous post-AGB component is the
primary source of both luminosity and current mass loss. Here, we present the
results of a seven-year, eight-orbit spectroscopic monitoring program of HD
44179, designed to uncover new information about the source of the
Lyman/far-ultraviolet continuum in the system as well as the driving mechanism
for the bipolar outflow producing the current nebula. Our observations of the
H-alpha line profile around the orbital phase of superior conjunction reveal
the secondary component to be the origin of the fast (max. v~560^{-1}\sun_{max} \ge 17,0002 -
5\times10^{-5}\sun^{-1}\sun$, about 5% of the
luminosity of the entire system. (abridged)Comment: Accepted for publication in Ap
High-latitude supergiants: anomalies in the spectrum of LN Hya in 2010
High-resolution echelle spectra taken with the 6-m telescope in 2003-2011 are
used to study features of the optical spectrum and the velocity field in the
atmosphere of the semiregular variable LN Hya in detail. The weak symmetric
photospheric absorptions indicate radial velocity variations from night to
night (by as much as 3 km/s), resulting from small pulsations. Peculiarities
and profile variations were found for strong lines of FeI, FeII, BaII, SiII,
etc. The profiles of these lines were asymmetric: their short-wave wings were
extended and their cores were either split or distorted by emission. During the
2010 observing season, the position and depth of the Halpha absorption
component, the intensities of the short and long-wave emission components, and
the intensity ratio of the latter components varied from spectrum to spectrum.
Weak emissions of neutral atoms (VI, MnI, CoI, NiI, FeI) appeared in the
spectrum of June 1, 2010. All these spectral peculiarities, recorded for the
first time, suggest that we have detected rapid changes in the physical
conditions in the upper atmospheric layers of LN Hya in 2010.Comment: 17 pages, 5 figures, 3 table
A massive parsec-scale dust ring nebula around the yellow hypergiant Hen 3-1379
On the basis of far-infrared images obtained by the Herschel Space Observatory, we report the discovery of a large and massive dust shell around the yellow hypergiant Hen 3-1379. The nebula appears as a detached ring of 1 pc diameter which contains 0.17 M[SUB]&sun;[/SUB] of dust. We estimate the total gas mass to be 7 M[SUB]&sun;[/SUB], ejected some 1.6 × 10[SUP]4[/SUP] years ago. The ring nebula is very similar to nebulae found around luminous blue variables (LBVs) except it is not photoionized. We argued that Hen 3-1379 is in a pre-LBV stage, providing direct evidence that massive LBV ring nebulae can be ejected during the red supergiant phase