- ID:
- ivo://CDS.VizieR/J/A+A/592/A76
- Title:
- VY CMa ALMA NaCl images
- Short Name:
- J/A+A/592/A76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- At the end of their lives, most stars lose a significant amount of mass through a stellar wind. The specific physical and chemical circumstances that lead to the onset of the stellar wind for cool luminous stars are not yet understood. Complex geometrical morphologies in the circumstellar envelopes prove that various dynamical and chemical processes are interlocked and that their relative contributions are not easy to disentangle. We aim to study the inner-wind structure (R<250R*) of the well-known red supergiant VY CMa, the archetype for the class of luminous red supergiant stars experiencing high mass loss. Specifically, the objective is to unravel the density structure in the inner envelope and to examine the chemical interaction between gas and dust species. We analyse high spatial resolution (~0.24"x0.13") ALMA Science Verification (SV) data in band 7, in which four thermal emission lines of gaseous sodium chloride (NaCl) are present at high signal-to-noise ratio.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/437/532
- Title:
- VY CMa molecular line spectra
- Short Name:
- J/MNRAS/437/532
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the far-infrared and submillimetre molecular emission-line spectrum of the luminous M-supergiant VY CMa, observed with the Spectral and Photometric Imaging Receiver (SPIRE) and Photodetector Array Camera and Spectrometer for Herschel spectrometers aboard the Herschel Space Observatory. Over 260 emission lines were detected in the 190-650{mu}m SPIRE Fourier Transform Spectrometer spectra, with one-third of the observed lines being attributable to H_2_O. Other detected species include CO, ^13^CO, H_2_O, SiO, HCN, SO, SO2, CS, H_2_S and NH_3_. Our model fits to the observed ^12^CO and ^13^CO line intensities yield a ^12^C/^13^C ratio of 5.6+/-1.8, consistent with measurements of this ratio for other M-supergiants, but significantly lower than previously estimated for VY CMa from observations of lower-J lines. The spectral line energy distribution for 20 SiO rotational lines shows two temperature components: a hot component at ~1000K, which we attribute to the stellar atmosphere and inner wind, plus a cooler ~200K component, which we attribute to an origin in the outer circumstellar envelope. We fit the line fluxes of ^12^CO, ^13^CO, H_2_O and SiO, using the smmol non-local thermodynamic equilibrium (LTE) line transfer code, with a mass-loss rate of 1.85x10^-4^M_{sun}_/yr between 9R* and 350R*. We also fit the observed line fluxes of ^12^CO, ^13^CO, H_2_O and SiO with smmol non-LTE line radiative transfer code, along with a mass-loss rate of 1.85x10^-4^M_{sun}_/yr. To fit the high rotational lines of CO and H_2_O, the model required a rather flat temperature distribution inside the dust condensation radius, attributed to the high H_2_O opacity. Beyond the dust condensation radius the gas temperature is fitted best by an r-0.5 radial dependence, consistent with the coolant lines becoming optically thin. Our H_2_O emission-line fits are consistent with an ortho:para ratio of 3 in the outflow.
- ID:
- ivo://CDS.VizieR/J/AJ/146/162
- Title:
- Wolf-Rayet and RSG stars in M101. I. HST photometry
- Short Name:
- J/AJ/146/162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Assembling a catalog of at least 10000 Wolf-Rayet (W-R) stars is an essential step in proving (or disproving) that these stars are the progenitors of Type Ib and Type Ic supernovae. To this end, we have used the Hubble Space Telescope (HST) to carry out a deep, HeII optical narrowband imaging survey of the ScI spiral galaxy M101. Almost the entire galaxy was imaged with the unprecedented depth and resolution that only the HST affords. Differenced with archival broadband images, the narrowband images allow us to detect much of the W-R star population of M101. We describe the extent of the survey and our images, as well as our data reduction procedures. A detailed broadband-narrowband imaging study of a field east of the center of M101, containing the giant star-forming region NGC5462, demonstrates our completeness limits, how we find W-R candidates, their properties and spatial distribution, and how we rule out most contaminants. We use the broadband images to locate luminous red supergiant (RSG) candidates. The spatial distributions of the W-R and RSG stars near NGC 5462 are strikingly different. W-R stars dominate the complex core, while RSGs dominate the complex halo. Future papers in this series will describe and catalog more than a thousand W-R and RSG candidates that are detectable in our images, as well as spectra of many of those candidates.
- ID:
- ivo://CDS.VizieR/J/AJ/141/17
- Title:
- 5-year spectroscopy and photometry of Deneb
- Short Name:
- J/AJ/141/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Deneb is often considered the prototypical A-type supergiant and is one of the visually most luminous stars in the Galaxy. A-type supergiants are potential extragalactic distance indicators, but the variability of these stars needs to be better characterized before this technique can be considered reliable. We analyzed 339 high-resolution echelle spectra of Deneb obtained over the five-year span of 1997 through 2001 as well as 370 Stroemgren photometric measurements obtained during the same time frame. Our spectroscopic analysis included dynamical spectra of the H{alpha} profile, H{alpha} equivalent widths, and radial velocities measured from SiII {lambda}{lambda} 6347, 6371.
- ID:
- ivo://CDS.VizieR/J/ApJ/703/441
- Title:
- Yellow supergiants in M31
- Short Name:
- J/ApJ/703/441
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The yellow supergiant (F- and G-type) content of nearby galaxies can provide a critical test of stellar evolution theory, bridging the gap between the hot, massive stars and the cool red supergiants. But, this region of the color-magnitude diagram is dominated by foreground contamination, requiring membership to somehow be determined. Fortunately, the large negative systemic velocity of M31, coupled to its high rotation rate, provides the means for separating the contaminating foreground dwarfs from the bona fide yellow supergiants within M31. We obtained radial velocities of ~2900 individual targets within the correct color-magnitude range corresponding to masses of 12M_{sun}_ and higher. A comparison of these velocities to those expected from M31's rotation curve reveals 54 rank-1 (near certain) and 66 rank-2 (probable) yellow supergiant members, indicating a foreground contamination >=96%. We expect some modest contamination from Milky Way halo giants among the remainder, particularly for the rank-2 candidates, and indeed follow-up spectroscopy of a small sample eliminates four rank 2's while confirming five others.
