Echelle Long‐Slit Optical Spectroscopy of Evolved Stars

Abstract

We present echelle long-slit optical spectra of a sample of objects evolving off the asymptotic giant branch (AGB), most of them in the preplanetary nebula ( PPN ) phase, obtained with the ESI and MIKE spectrographs at the 10 m Keck II and 6.5 m Magellan-I telescopes, respectively. The total wavelength range covered with ESI (MIKE) is $3900Y10900 8 ($3600Y7200 8). In this paper, we focus our analysis mainly on the H profiles. Prominent H emission is detected in half of the objects, most of which show broad H wings (with total widths of up to $4000 km s À1 ). In the majority of the H -emission sources, fast, post-AGB winds are revealed by P-Cygni profiles. In $37% of the objects H is observed in absorption. In almost all cases, the absorption profile is partially filled with emission, leading to complex, structured profiles that are interpreted as an indication of incipient post-AGB mass loss. The rest of the objects ($13%) are H nondetections. We investigate correlations between the H profile and different stellar and envelope parameters. All sources in which H is seen mainly in absorption have F-G type central stars, whereas sources with intense H emission span a larger range of spectral types from O to G, with a relative maximum around B, and also including very late C types. Shocks may be an important excitation/ionization agent of the close stellar surroundings for objects with late type central stars. Sources with pure emission or P Cygni H profiles have larger J À K color excess than objects with H mainly in absorption, which suggests the presence of warm dust near the star in the former. The two classes of profile sources also segregate in the IRAS color-color diagram in a way that intense H -emitters have dust grains with a larger range of temperatures. Spectral classification of the central stars in our sample is presented. For a subsample (13 objects), the stellar luminosity has been derived from the analysis of the O i 7771Y7775 8 infrared triplet. The location in the HR diagram of most of these targets, which represent $30% of the whole sample, is consistent with relatively high final (and, presumably, initial) masses in the range M f $ 0:6 Y0:9 M (M i $ 3Y 8 M ).

The peculiar nova V1309 Scorpii/nova Scorpii 2008

“…The line profiles observed in the late epochs spectra and the strongest emission lines observed for all epochs, are consistent with the line forming region being an optically thick slow wind which ejects material either in subsequent multiple layers or in an axis-symmetric partially collimated outflow, similarly to the case of PPN and PAGB stars (Sanchez-Contreras et al 2008). In particular, we can explain the observation of absorption lines superimposed on broader emission by a slowly expanding shell which is denser in its equatorial plane.…”

“…This type of profile has been observed in PPN and AGB stars, too (see e.g. Sanchez-Contreras et al 2008). The forbidden lines are a-symmetric showing a more extended blue wing (Fig.…”

“…The absorption lines superposed on the emission, together with the broad extended wings (see text below) compose a profile which is somehow similar to that seen in pre-PN (PPN) and young PN or post AGB stars (e.g. Sanchez-Contreras et al 2008). Close inspection reveals that the Hα and Hβ Balmer lines show minor absorption and emission components as well as extended wings.…”

Time-resolved spectroscopy of BD+46°442: Gas streams and jet creation in a newly discovered evolved binary with a disk

“…The Hα profiles discussed here are not uncommon among post-AGB stars (Waters et al 1993b;Pollard et al 1997;Maas et al 2005;Sánchez Contreras et al 2008), but their variabilities have not been systematically studied as a function of orbital phase. We are aware of four other disk systems in which strong blueshifted absorption was noted to develop during the giant's superior conjunction: HR 4049 with P orb = 430 d , a sin i = 0.6 AU, i ≥ 60 • , and e = 0.3 (Waelkens et al 1991;Van Winckel et al 1995;Bakker et al 1998); HD 44179 (the central star of the Red Rectangle nebula) with P orb = 318 d , a sin i = 0.5 AU, i "effective" = 35 • , and e = 0.4 (Waelkens et al 1996;Witt et al 2009); IRAS 08544−4431 with P orb = 508 d , a sin i = 0.4 AU, i ∼ 60 • , and e = 0.2 (Maas et al 2003;Deroo et al 2007;Van Winckel et al 2009); and IRAS 19135+3937 with P orb = 127 d , a sin i = 0.2 AU, and e ∼ 0.3 (Gorlova et al 2012).…”

Deep into the Water Fountains

“…Moreover, the main excitation mechanism of the H 2 rovibrational lines detected, either UV-pumped or shock-excited, can be constrained using the flux ratios of the detected H 2 spectral features. In particular, K-band integral field spectroscopy has yielded important results towards late-type sources at different evolutionary stages, from those young post-AGB sources (T e f f < 1.5 × 10 4 K) which are not hot enough to photoionize the innermost layers of their CSEs (Sánchez Contreras et al 2008;, to the so called "hot post-AGB" sources, detected in both near infrared (Gledhill & Forde 2015) and radio wavelengths (Cerrigone et al 2008(Cerrigone et al , 2011.…”