- ID:
- ivo://CDS.VizieR/J/AJ/111/439
- Title:
- Chromospheric emission in late-type stars.
- Short Name:
- J/AJ/111/439
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- More than 800 southern stars within 50pc have been observed for chromospheric emission in the cores of the Ca II H and K lines. Most of the sample targets were selected to be G dwarfs on the basis of colors and spectral types. The bimodal distribution in stellar activity first noted in a sample of northern stars by Vaughan and Preston (1980PASP...92..385V) is confirmed, and the percentage of active stars, about 30%, is remarkably consistent between the northern and southern surveys. This is especially compelling given that we have used an entirely different instrumental setup and stellar sample than used in the previous study. Comparisons to the Sun, a relatively inactive star, show that most nearby solar-type stars have a similar activity level, and presumably a similar age. We identify two additional subsamples of stars -- a very active group, and a very inactive group. The very active group may be made up of young stars near the Sun, accounting for only a few percent of the sample, and appears to be less than ~0.1Gyr old. Included in this high-activity tail of the distribution, however, is a subset of very close binaries of the RS CVn or W UMa types. The remaining members of this population may be undetected close binaries or very young single stars. The very inactive group of stars, contributing ~5%-10% to the total sample, may be those caught during a Maunder Minimum type phase. If the observations of the survey stars are considered to be a sequence of snapshots of the Sun during its life, we might expect that the Sun will spend about 10% of the remainder of its main sequence life in a Maunder Minimum phase.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/414/418
- Title:
- Chromospheric Mg II h+k flux of evolved stars
- Short Name:
- J/MNRAS/414/418
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Of a total of 177 cool G, K and M giants and supergiants, we measured the MgII h+k line emission of extended chromospheres in high-resolution (LWR) International Ultraviolet Explorer (IUE) spectra by using the IUE final data archive at the Space Telescope Science Institute (STScI) and derived the respective stellar surface fluxes. They represent the chromospheric radiative energy losses presumably related to basal heating by the dissipation of acoustic waves, plus a highly variable contribution due to magnetic activity.
- ID:
- ivo://CDS.VizieR/J/A+A/326/249
- Title:
- Chromospheric models of dwarf M stars
- Short Name:
- J/A+A/326/249
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Tables 4 and 5 give the atmospheric parameters for our models of dM stars Gl 588 and Gl 628. The columns give the column mass in g/cm^-2^, the electron temperature in K, the microturbulent velocity in km/s; the continuum optical depth at 5000{AA}; the hydrogen, proton, and electron density in particles per cm^-3^; and the height h (in km) above the level where tau_5000_=1.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A102
- Title:
- CH3SC(O)H observed line frequencies and strengths
- Short Name:
- J/A+A/644/A102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- S-methyl thioformate CH_3_SC(O)H is a monosulfur derivative of methyl formate, a relatively abundant component of the interstellar medium (ISM). S-methyl thioformate being, thermodynamically,the most stable isomer, it can be reasonably proposed for detection in the ISM. This work aims to experimentally study and theoretically analyze the ground and first torsional excited states for CH_3_SC(O)H in a large spectral range for astrophysical use. S-methyl thioformate was synthesized as a result of a reaction of methyl mercaptan with acetic-formic anhydride. The millimeter-wave spectrum was then recorded for the first time from 150 to 660GHz with the solid-state-based spectrometer at Lille. A set of 3545 lines is determined and combined with 54 previously measured lines in the microwave region, belonging to ground state vt=0 as well as 1391 transitions in the first excited state of torsion v18=1. Some 164 lines were also assigned to vt18=2 for the A-species. A global fit was performed using the BELGI-Cs code taking into account the large splitting of A and E lines due to methyl internal rotation motion with a relatively low barrier, V3=127.4846(15)cm^-1^. Using our spectroscopy work, a deep search of S-methyl thioformate was carried out in the IRAM 30m and ALMA data of different high-mass star-forming regions (Orion KL and Sgr B2). We derived an upper limit to the CH_3_SC(O)H column density in these regions.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A167
- Title:
- C2H3SH observed experimental transitions
- Short Name:
- J/A+A/623/A167
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New laboratory investigations of the rotational spectrum of postulated astronomical species are essential to support the assignment and analysis of current astronomical surveys. In particular, considerable interest surrounds sulfur analogs of oxygen-containing interstellar molecules and their isomers. To enable reliable interstellar searches of vinyl mercaptan, the sulfur-containing analog to the astronomical species vinyl alcohol, we investigated its pure rotational spectrum at millimeter wavelengths. We extended the pure rotational investigation of the two isomers syn and anti vinyl mercaptan to the millimeter domain using a frequency-multiplication spectrometer. The species were produced by a radiofrequency discharge in 1,2-ethanedithiol. Additional transitions were remeasured in the centimeter band using Fourier-transform microwave spectroscopy to better determine rest frequencies of transitions with low-J and low-Ka values. Experimental investigations were supported by quantum chemical calculations on the energetics of both the [C_2_,H_4_,S] and [C_2_,H_4_,O] isomeric families. Interstellar searches for both syn and anti vinyl mercaptan as well as vinyl alcohol were performed in the EMoCA spectral line survey carried out toward Sgr B2(N2) with ALMA. Results. Highly accurate experimental frequencies (to better than 100kHz accuracy) for both syn and anti isomers of vinyl mercaptan are measured up to 250GHz; these deviate considerably from predictions based on extrapolation of previous microwave measurements. Reliable frequency predictions of the astronomically most interesting millimeter-wave lines for these two species can now be derived from the best-fit spectroscopic constants. From the energetic investigations, the four lowest singlet isomers of the [C2,H4,S] family are calculated to be nearly isoenergetic, which makes this family a fairly unique test bed for assessing possible reaction pathways. Upper limits for the column density of syn and anti vinyl mercaptan are derived toward the extremely molecule-rich star-forming region Sgr B2(N2) enabling comparison with selected complex organic molecules.
- ID:
- ivo://CDS.VizieR/J/A+A/632/A60
- Title:
- CH 2THz spectra towards 7 molecular clouds
- Short Name:
- J/A+A/632/A60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Despite being a commonly observed feature, the modification of the velocity structure in spectral line profiles by hyperfine structure complicates the interpretation of spectroscopic data. This is particularly true for observations of simple molecules such as CH and OH toward the inner Galaxy, which show a great deal of velocity crowding. In this paper, we investigate the influence of hyperfine splitting on complex spectral lines, with the aim of evaluating canonical abundances by decomposing their dependence on hyperfine structures. This is achieved from first principles through deconvolution. We present high spectral resolution observations of the rotational ground state transitions of CH near 2THz seen in absorption toward the strong FIR-continuum sources AGAL010.62-00.384, AGAL034.258+00.154, AGAL327.293- 00.579, AGAL330.954-00.182, AGAL332.826-00.549, AGAL351.581-00.352 and SgrB2(M). These were observed with the GREAT instrument on board SOFIA. The observed line profiles of CH were deconvolved from the imprint left by the lines' hyperfine structures using the Wiener filter deconvolution, an optimised kernel acting on direct deconvolution. The quantitative analysis of the deconvolved spectra first entails the computation of CH column densities. Reliable N(CH) values are of importance owing to the status of CH as a powerful tracer for H_2_ in the diffuse regions of the interstellar medium. The N(OH)/N(CH) column density ratio is found to vary within an order of magnitude with values ranging from one to 10, for the individual sources that are located outside the Galactic centre. Using CH as a surrogate for H_2_, we determined the abundance of the OH molecule to be X(OH)=1.09x10^-7^ with respect to H_2_. The radial distribution of CH column densities along the sightlines probed in this study, excluding SgrB2(M), showcase a dual peaked distribution peaking between 5 and 7 kpc. The similarity between the correspondingly derived column density profile of H_2_ with that of the CO-dark H_2_ gas traced by the cold neutral medium component of [CII] 158um emission across the Galactic plane, further emphasises the use of CH as a tracer for H_2_.
- ID:
- ivo://CDS.VizieR/J/A+A/612/A37
- Title:
- CH 149um spectra of 4 molecular clouds
- Short Name:
- J/A+A/612/A37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The methylidyne radical CH is commonly used as a proxy for molecular hydrogen in the cold, neutral phase of the interstellar medium. The optical spectroscopy of CH is limited by interstellar extinction, whereas far-infrared observations provide an integral view through the Galaxy. While the HF ground state absorption, another H_2_ proxy in diffuse gas, frequently suffers from saturation, CH remains transparent both in spiral-arm crossings and high-mass star forming regions, turning this light hydride into a universal surrogate for H_2_. However, in slow shocks and in regions dissipating turbulence its abundance is expected to be enhanced by an endothermic production path, and the idea of a "canonical" CH abundance needs to be addressed. The N=2<-1 ground state transition of CH at {lambda}149um has become accessible to high-resolution spectroscopy thanks to GREAT, the German Receiver for Astronomy at Terahertz Frequencies aboard the Stratospheric Observatory for Infrared Astronomy, SOFIA. Its unsaturated absorption and the absence of emission from the star forming regions makes it an ideal candidate for the determination of column densities with a minimum of assumptions. Here we present an analysis of four sightlines towards distant Galactic star forming regions, whose hot cores emit a strong far-infrared dust continuum serving as background signal. Moreover, if combined with the sub-millimeter line of CH at {lambda}560um, environments forming massive stars can be analyzed. For this we present a case study on the "proto-Trapezium" cluster W3 IRS5. While we confirm the global correlation between the column densities of HF and those of CH, both in arm and interarm regions, clear signposts of an over-abundance of CH are observed towards lower densities. However, a significant correlation between the column densities of CH and HF remains. A characterization of the hot cores in the W3 IRS5 proto-cluster and its envelope demonstrates that the sub-millimeter/far-infrared lines of CH reliably trace not only diffuse but also dense, molecular gas. In diffuse gas, at lower densities a quiescent ion-neutral chemistry alone cannot account for the observed abundance of CH. Unlike the production of HF, for CH^+^ and CH, vortices forming in turbulent, diffuse gas may be the setting for an enhanced production path. However, CH remains a valuable tracer for molecular gas in environments reaching from diffuse clouds to sites of high-mass star formation.
- ID:
- ivo://CDS.VizieR/J/A+A/544/A26
- Title:
- CI Aql spectra during 2000 outburst
- Short Name:
- J/A+A/544/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High- and low-resolution optical spectra of CI Aql were obtained during the outburst in 2000. Multiple absorption components of HI and FeII lines were detected at the early decline stage. Their radial velocities were roughly -2500km/s, -2200km/s , -1700km/s, and -1400km/s, among which only the last components were likely still accelerating during the early decline stage. Prominent emission lines of [OIII] and [NII] appeared about one month after light maximum. The duration of the nebular stage, however, was only one month and a few weeks. The ejected gas shells seem to have started to shrink about 70 days after light maximum. The amount of interstellar extinction is estimated to be E(B-V)=0.92+/-0.15 from the equivalent widths of the diffuse interstellar absorption bands. The helium abundance in the ejecta is estimated to be N(He)=0.19+/-0.05 and the mass of the ejecta to be about 2x10^-6^M_{sun}_. This object has been classified as a U Sco type recurrent nova, but its spectral evolution during the outburst resembled those of T Pyx type recurrent novae. It is doubtful whether the peak of m_V_~9mag on 2000 May 5 was the true light maximum or an earlier brighter peak had been overlooked, because the spectral data suggest that the ejections of gas shells occurred prior to the discovery of the outburst on 2000 April 28.
- ID:
- ivo://CDS.VizieR/J/MNRAS/399/2139
- Title:
- CI Cyg BVRcIc light curves
- Short Name:
- J/MNRAS/399/2139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we discuss the early phases of the ongoing outburst that CI Cyg, a prototype symbiotic star, is currently undergoing after 30-year quiescence. We have tightly monitored CI Cyg in B V R_C_ I_C_ bands, starting a whole year before the onset of the outburst, and in addition we obtained numerous Echelle high- and low-resolution absolutely flux-calibrated spectra. The outburst started while the accreting white dwarf (WD) was being eclipsed by the Roche lobe filling M giant companion, and it was discovered during the egress phase on the second half of 2008 August. The system reached peak V-band brightness in early 2008 October and has been characterized by amplitudes {delta}B=1.9, {delta}V=1.5, {delta}R_C_=0.9, {delta}I_C_=0.4mag. At maximum V-band brightness, the outbursting WD had expanded to closely resemble an F3 II/Ib star, with MV=-3.5, Teff~6900K and R=28R_{sun}_. The high-ionization emission lines ([NeV], [FeVII], HeII) disappeared and only lower ionization lines were visible. Balmer and He I emission lines declined in equivalent width but increased in absolute flux. The output radiated by the hot component during the outburst corresponds to nuclear burning proceeding at a 2x10^-8^M_{sun}_/yr rate.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A122
- Title:
- CIELO-RGS, soft X-ray ionized emission lines catalog
- Short Name:
- J/A+A/625/A122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution X-ray spectroscopy has advanced our understanding of the hot Universe by revealing physical properties like kinematics, temperature, and abundances of the astrophysical plasmas. Despite technical and scientific achievements, the lack of scientific products at a level higher than count spectra is hampering complete scientific exploitation of high-quality data. This paper introduces the Catalog of Ionized Emission Lines Observed by the Reflection Grating Spectrometer (CIELO-RGS) onboard the XMM-Newton space observatory. The CIELO-RGS catalog aims to facilitate the exploitation of emission features in the public RGS spectra archive. In particular, we aim to analyze the relationship between X-ray spectral diagnostics parameters and measurements at other wavelengths. This paper focuses on the methodology of catalog generation, describing the automated line-detection algorithm. A moderate sample (~2400 observations) of high-quality RGS spectra available at XMM-Newton Science Archive is used as our starting point. A list of potential emission lines is selected based on a multi-scale peak-detection algorithm in a uniform and automated way without prior assumption on the underlying astrophysical model. The candidate line list is validated via spectral fitting with simple continuum and line profile models. We also compare the catalog content with published literature results on a small number of exemplary sources. We generate a catalog of emission lines (1.2x10^4^) detected in ~1600 observations toward stars, X-ray binaries, supernovae remnants, active galactic nuclei, and groups and clusters of galaxies. For each line, we report the observed wavelength, broadening, energy and photon flux, equivalent width, and so on.