P. Morris

California Institute of Technology

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J. Cernicharo

Consejo Superior de Investigaciones Científicas

J. R. Houck

Cornell University

T. G. Phillips

Wyle (United States)

D. C. Lis

California Institute of Technology

Maryvonne Gérin

Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères

K. M. Menten

Max Planck Institute for Radio Astronomy

David A. Neufeld

Johns Hopkins University

C. Vastel

Centre National de la Recherche Scientifique

P. Encrenaz

Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères

R. Plume

University of Calgary

Cooperative Institutions

Centre National de la Recherche Scientifique

217

Max Planck Society

150

California Institute of Technology

149

SRON Netherlands Institute for Space Research

127

Max Planck Institute for Radio Astronomy

Jet Propulsion Laboratory

Space Telescope Science Institute

Leiden University

Observatoire de Paris

University College London

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ISO-SWS spectra of Planetary Nebulae with low-mass [WC] central stars: a mixed C- and O-rich dust chemistry

Symposium - International Astronomical Union (1999)

P. Morris L. B. F. M. Waters D. A. Beintema

The timing of PNe formation around low-mass WC stars is unsettled with respect to pulsations early in the post-AGB phase, or later thermal pulses ( e.g. , Tylenda & Gorny 1997). The chemistry of the dust in the nebulae can be used to trace the mass-loss history. Using ISO-SWS spectroscopy, the PNe BD+30°3639 [WC9] and He2–113 [WC11] have been identified by Waters et al. (1998) to exhibit emission from C-rich dust (PAHs) in the surrounding envelopes at λ 15 μm, while O-abundant silicate features are present at longer wavelengths. Figure 1 shows the PAH features, which include additional WCPNe observations to extend the range of stellar spectral subtypes.

10.1017/s0074180900205810

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The neon abundance in WC stars -- I. ISO SWS spectroscopy of WR146 (WC6+O)

Monthly Notices of the Royal Astronomical Society (1997)

A. J. Willis Luc Dessart P. A. Crowther P. Morris A. Maeder

We present infrared spectroscopy in the wavelength range 2.6–20 μm of the WC6+0 binary system WR146 (MR112) obtained with the Short Wavelength Spectrometer (SWS) on the Infrared Space Observatory (ISO). These data are combined with ground-based optical (INT) and near-IR (UKIRT) spectroscopy and theoretical continuum distributions revealing E(B — V) = 2.8 mag, a continuum optical light ratio (WR:O) = 1:2 ± 1, a probable O8.5V companion and a distance of 750 pc. We obtain C/He=0.15 by number for the WC6 star from an analysis of near-IR recombination lines, a factor of 2 higher than previously estimated by Eenens & Williams. We find a WC6 terminal wind velocity of 2700 km s−1 from the observed [Ne iii] 15.5-μm profile, while results from test WCE model atmospheric calculations and radio flux measurements imply M = 2.6 × 10−5 M⊙ yr−1. An analysis of the [Ne iii] 15.5-μm line yields a lower limit to the neon abundance of Ne/He = 3.4 × 10−3 by number. Our ISO spectra show no wind emission in either [Ne ii] 12.81 μm or [Ne v] 14.32 μm from which we estimate Ne iv/Ne iii ≤ 1. The resulting bound on the neon abundance in the WC6 star is thus 3.4 × 10−3 ≤ Ne/He ≤ 6.8 × 10−3. This result is in close accord with the predicted value of Ne/ He ∼ 6 × 10−3; from stellar evolution models of WC stars, during which the products of interior nuclear burning are revealed at the stellar surface.

Line (geometry)

10.1093/mnras/290.2.371

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Citations (28)

Spectroscopic signatures of the vanishing natural coronagraph of Eta Carinae

Monthly Notices of the Royal Astronomical Society (2021)

A. Damineli Felipe Navarete D. J. Hillier A. F. J. Moffat M. F. Corcoran

Eta Carinae is a massive interacting binary system shrouded in a complex circumstellar environment whose evolution is the source of the long-term brightening observed during the last 80 years. An occulter, acting as a natural coronagraph, impacts observations from our perspective, but not from most other directions. Other sight-lines are visible to us through studies of the Homunculus reflection nebula. The coronagraph appears to be vanishing, decreasing the extinction towards the central star, and causing the star's secular brightening. In contrast, the Homunculus remains at an almost constant brightness. The coronagraph primarily suppresses the stellar continuum, to a lesser extent the wind lines, and not the circumstellar emission lines. This explains why the absolute values of equivalent widths (EWs) of the emission lines in our direct view are larger than those seen in reflected by the Homunculus, why the direct view absolute EWs are decreasing with time, and why lower-excitation spectral wind lines formed at larger radii (e.g. FeII 4585A) decrease in intensity at a faster pace than higher excitation lines that form closer to the star (e.g. H\delta). Our main result is that the star, despite its 10-fold brightening over two decades, is relatively stable. A vanishing coronagraph that can explain both the large flux evolution and the much weaker spectral evolution. This is contrary to suggestions that the long-term variability is intrinsic to the primary star that is still recovering from the Great Eruption with a decreasing mass-loss rate and a polar wind that is evolving at a slower pace than at the equator.

Coronagraph

10.1093/mnras/stab1398

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Interstellar CH absorption in the diffuse interstellar medium along the sight-lines to G10.6–0.4 (W31C), W49N, and W51

Astronomy and Astrophysics (2010)

Maryvonne Gérin M. De Luca J. R. Goicoechea Eric Herbst É. Falgarone

We report the detection of the ground state N,J = 1,3/2 1,1/2 doublet of the methylidyne radical CH at ~532 GHz and ~536 GHz with the Herschel/HIFI instrument along the sight-line to the massive star-forming regions G10.6–0.4 (W31C), W49N, and W51. While the molecular cores associated with these massive star-forming regions show emission lines, clouds in the diffuse interstellar medium are detected in absorption against the strong submillimeter background. The combination of hyperfine structure with emission and absorption results in complex profiles, with overlap of the different hyperfine components. The opacities of most of the CH absorption features are linearly correlated with those of CCH, CN, and HCO^{+^{in the same velocity intervals. In specific narrow velocity intervals, the opacities of CN and HCO^{+^{deviate from the mean trends, giving rise to more opaque absorption features. We propose that CCH can be used as another tracer of the molecular gas in the absence of better tracers, with [CCH]/[ H_{2_{] ~ 3.2±1.1×10^{-8^{. The observed [CN]/[CH], [CCH]/[CH] abundance ratios suggest that the bulk of the diffuse matter along the lines of sight has gas densities n_{H_{= n(H) + 2n(H_{2_{) ranging between 100 and 1000 cm^{-3^.}}}}}}}}}}}}}

Opacity

Line-of-sight

Line (geometry)

10.1051/0004-6361/201015115

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Citations (92)

Herschel/HIFI In-flight Commissioning and Performance

HAL (Le Centre pour la Communication Scientifique Directe) (2010)

D. Teyssier C. Risacher P. Dieleman W. M. Laauwen A. de Jonge

The Herschel Space Observatory was successfully launched on the 14th of May, 2009, lifting into space the Heterodyne Instrument for the Far-Infrared (HIFI). After the standard early orbit operations on the Space-craft, the instrument was switched on for the first time on the 24th of May, kicking off an instrument Commissioning period of more than a month and a half. We present here the outcome of this Commissioning campaign, including the measured in-flight performance of the instrument. Among the challenges encountered during this period was the need to optimize the stability of the signal provided by the Local Oscillator (LO) chains in some of the frequency bands, in particular that covering the singly Ionized Carbon (C+) line at the upper edge of the HIFI range, and one of the backbones of the science program of the instrument. The same concept also allowed significant improvements in the upper end of the 3b LO chain. Another noticeable achievement was the very good co-alignment measured between the mixer beams in the respective H and V polarizations offered by HIFI, allowing for more than a simple build-in redundancy, as the observing efficiency will really benefits from the combination of the two mixers.

Heterodyne (poetry)

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Water content and wind acceleration in the envelope around the oxygen-rich AGB star IK Tauri as seen byHerschel/HIFI

Astronomy and Astrophysics (2010)

L. Decin K. Justtanont E. De Beck R. Lombaert A. de Koter

During their asymptotic giant branch, evolution low-mass stars lose a significant fraction of their mass through an intense wind, enriching the interstellar medium with products of nucleosynthesis. We observed the nearby oxygen-rich asymptotic giant branch star IK Tau using the high-resolution HIFI spectrometer onboard Herschel. We report on the first detection of H_2^{16}O and the rarer isotopologues H_2^{17}O and H_2^{18}O in both the ortho and para states. We deduce a total water content (relative to molecular hydrogen) of 6.6x10^{-5}, and an ortho-to-para ratio of 3:1. These results are consistent with the formation of H_2O in thermodynamical chemical equilibrium at photospheric temperatures, and does not require pulsationally induced non-equilibrium chemistry, vaporization of icy bodies or grain surface reactions. High-excitation lines of 12CO, 13CO, 28SiO, 29SiO, 30SiO, HCN, and SO have also been detected. From the observed line widths, the acceleration region in the inner wind zone can be characterized, and we show that the wind acceleration is slower than hitherto anticipated.

Isotopologue

Asymptotic giant branch

10.1051/0004-6361/201015069

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A submillimeter study of CH in Orion KL

The Molecular Universe (2011)

John C. Pearson H. M. Sen Gupta P. Morris Maryvonne Gérin Edwin A. Bergin

Orion Nebula

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ISO-SWS observations of infrared absorption bands of the diffuse interstellar medium: The 6.2 mu m feature of aromatic compounds

Astronomy and Astrophysics (1998)

W. A. Schutte K. A. van der Hucht D. C. B. Whittet A. C. A. Boogert A. G. G. M. Tielens

We present ISO-SWS spectroscopy of eight strong infrared sources with large extinction through the diffuse interstellar medium. These are five late-type Wolf-Rayet stars, the blue hypergiant Cyg OB2 #12 and the Galactic Center Sources 3 and 4. The spectra show a number of absorption features that can be ascribed to interstellar dust and gas. Features at 3.0, 3.4, 4.66 and 5.95 mu m were already known from ground and airborne observations, while features at 4.27 and 6.21 mu m are for the first time observed by ISO. We ascribe the 3.0, 4.27 and 4.66 mu m features to H(2)O ice, CO(2) ice and gaseous CO, respectively, located in dense clouds along four lines-of-sight in our study. Based on an excellent correspondence with the well-known emission feature observed in many other objects, the 6.2 mu m absorption band is identified with aromatic materials. The profile of the feature indicates that its carriers are PAHs or PAH clusters containing up to a few thousand carbon atoms. The lack of strong infrared features of hydroxy (OH), carbonyl (C=O) and aromatic CH groups towards the objects of the present study shows that the carbonaceous dust material in the diffuse ISM is poor in oxygen as well as hydrogen.

Extinction (optical mineralogy)

Absorption band

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CO, Water, and Tentative Methanol in η Carinae Approaching Periastron

The Astrophysical Journal Letters (2020)

P. Morris Steven B. Charnley M. F. Corcoran Martin Cordiner A. Damineli

In circumstellar gas, the complex organic molecule methanol has been found almost exclusively around young stellar objects, and is thus regarded as a signpost of recent star formation. Here we report the first probable detection of methanol around an evolved high-mass star, in the complex circumstellar environment around the Luminous Blue Variable $\eta$ Carinae, while using ALMA to investigate molecular cloud conditions traced by CO (2-1) in an orbit phase of the massive binary preceding the 2020 periastron. Favoring methanol over a $^{13}$CS alternative, the emission originates from hot ($T_{\rm{gas}} \simeq$ 700 K) material, $\sim$2$''$ (0.02 pc) across, centered on the dust-obscured binary in contrast to the CO which traces inner layers of the extended massive equatorial torus, and is accompanied by prominent absorption in a cooler ($T_{\rm{gas}} \simeq$ 110 K) layer of gas. We also report detections of water in $Herschel$/HIFI observations at 557 GHz and 988 GHz. The methanol abundance is several to 50 times higher than observed towards several lower mass stars, while water abundances are similar to those observed in cool, dense molecular clouds. The very high methanol:water abundance ratio in the core of $\eta$ Carinae may suggest methanol formation processes similar to Fischer-Tropsch-type catalytic reactions on dust grains. These observations prove that complex molecule formation can occur in the chemically evolved environments around massive stars in the end stages of their evolution, given sufficient gas densities and shielding conditions as may occur in material around massive interacting companions and merger remnants.

10.3847/2041-8213/ab784a

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Polarisation observations of H₂OJ_{K_-1} K₁= 5₃₂− 4₄₁620.701 GHz maser emission withHerschel/HIFI in Orion KL

Astronomy and Astrophysics (2014)

Scott C. Jones Martin Houde Martin Harwit M. Kidger A. Kraus

Context. The high intensities and narrow bandwidths exhibited by some astronomical masers make them ideal tools for studying star-forming giant molecular clouds. The water maser transition JK-1K1 = 532−441 at 620.701 GHz can only be observed from above Earth’s strongly absorbing atmosphere; its emission has recently been detected from space.

10.1051/0004-6361/201323267

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Citations (1)