- ID:
- ivo://CDS.VizieR/J/A+A/558/A112
- Title:
- Dimethyl ether-13C lab spectra up to 1.5THz
- Short Name:
- J/A+A/558/A112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The interpretation of astronomical observations depends on the knowledge of accurate rest frequencies and intensities. The objective of this work is to provide spectroscopic data for the two ^13^C-isotopologues of dimethyl ether in the vibrational ground state. High-resolution rotational-torsional spectra of dimethyl ether-^13^C1 and dimethyl ether-^13^C2 have been measured in the laboratory covering frequencies up to 1.5THz. The analysis is based on an effective rotational Hamiltonian for molecules with two large amplitude motions.
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- ID:
- ivo://CDS.VizieR/J/A+A/504/635
- Title:
- Dimethyl ether laboratory spectra up to 2.1THz
- Short Name:
- J/A+A/504/635
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dimethyl ether (CH_3_OCH_3_) is one of the largest organic molecules detected in the interstellar medium. As an asymmetric top molecule with two methyl groups which undergo large amplitude motions and a dipole moment of mu_b_=1.3D it conveys a dense spectrum throughout the terahertz region and contributes to the spectral line confusion in astronomical observations at these frequencies. Rotational spectra of dimethyl ether in its ground vibrational states are presented in this paper, which have been measured in the laboratory and analyzed covering frequencies up to 2.1THz. The analysis is based on an effective Hamiltonian for a symmetric two-top rotor and includes experimental data published so far. Frequency predictions are presented up to 2.5THz for astronomical applications with accuracies better than 1MHz.
- ID:
- ivo://CDS.VizieR/J/ApJ/500/1059
- Title:
- Dimethyl ether transitions frequencies
- Short Name:
- J/ApJ/500/1059
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dimethyl ether (CH_3_OCH_3_) is a well-known interstellar molecule with a large abundance in hot core regions. We have measured many rotational-torsional transition lines of this molecule in the 100-550GHz frequency range using two experimental techniques: a klystron-based traditional millimeter-wave spectrometer and a new fast scan spectrometer (designated "FASSST") with a voltage-tunable backward wave oscillator. The lines arising from the ground vibrational state have been combined with previous data, mainly at lower frequencies, to form a global data set consisting of over 1600 lines that have been assigned and fitted by an effective Hamiltonian method. The spectral constants obtained from the fit allow us to predict the frequencies of almost 6000 additional lines of dimethyl ether through 600GHz.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A49
- Title:
- Dimming event of RW Aurigae A
- Short Name:
- J/A+A/625/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- RW Aur A is a classical T Tauri star that has suddenly undergone three major dimming events since 2010. The reason for these dimming events is still not clear. The two epochs of observations uploaded here are on the deep dimming events (2015) and immediate after the dimmin event (2016).
- ID:
- ivo://CDS.VizieR/J/PAZh/38/108
- Title:
- 3D interstellar extinct. map within nearest kpc
- Short Name:
- J/PAZh/38/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The product of the previously constructed 3D maps of stellar reddening (Gontcharov, 2010AstL...36..584G, Cat. J/PAZh/36/615) and Rv variations (Gontcharov, 2012AstL...38...12G, J/PAZh/38/15) has allowed us to produce a 3D interstellar extinction map within the nearest kiloparsec from the Sun with a spatial resolution of 100pc and an accuracy of 0.2m. This map is compared with the 2D reddening map by Schlegel et al. (1998ApJ...500..525S), the 3D extinction map at high latitudes by Jones et al. (2011AJ....142...44J), and the analytical 3D extinction models by Arenou et al. (1992A&A...258..104A) and Gontcharov (2009AstL...35..780G). In all cases, we have found good agreement and show that there are no systematic errors in the new map everywhere except the direction toward the Galactic center. We have found that the map by Schlegel et al. (1998ApJ...500..525S) reaches saturation near the Galactic equator at E(B-V)>0.8m, has a zero-point error and systematic errors gradually increasing with reddening, and among the analytical models those that take into account the extinction in the Gould Belt are more accurate. Our extinction map shows that it is determined by reddening variations at low latitudes and Rv variations at high ones. This naturally explains the contradictory data on the correlation or anticorrelation between reddening and Rv available in the literature. There is a correlation in a thin layer near the Galactic equator, because both reddening and Rv here increase toward the Galactic center. There is an anticorrelation outside this layer, because higher values of Rv correspond to lower reddening at high and middle latitudes. Systematic differences in sizes and other properties of the dust grains in different parts of the Galaxy manifest themselves in this way. The largest structures within the nearest kiloparsec, including the Local Bubble, the Gould Belt, the Great Tunnel, the Scorpius, Perseus, Orion, and other complexes, have manifested themselves in the constructed map. Also the data of the Rv from Gontcharov (2012AstL...38...12G, Cat. J/PAZh/38/15) and E(B-V) from Gontcharov (2010AstL...36..584G, Cat. J/PAZh/36/615) 3D maps are added. The error of the E(B-V) is 0.04mag. The error of the Rv is about 0.2.
- ID:
- ivo://CDS.VizieR/J/AJ/122/1383
- Title:
- DIRECT BVI photometry in M31
- Short Name:
- J/AJ/122/1383
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- DIRECT is a project to directly obtain the distances to two important galaxies in the cosmological distance ladder, M31 and M33, using detached eclipsing binaries and Cepheids. As part of our search for these variables, we have obtained photometry and positions for thousands of stellar objects within the monitored fields, covering an area of 557.8arcmin^2^. Here we present the equatorial coordinates and BVI photometry for 26,712 stars in the M31 galaxy, along the eastern arm and in the vicinity of the star-forming region NGC 206.
- ID:
- ivo://CDS.VizieR/J/PASP/122/162
- Title:
- Direct imaging of exoplanets
- Short Name:
- J/PASP/122/162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-contrast imaging can find and characterize gas giant planets around nearby young stars and the closest M stars, complementing radial velocity and astrometric searches by exploring orbital separations inaccessible to indirect methods. Ground-based coronagraphs are already probing within 25AU of nearby young stars to find objects as small as 3M_{Jup}_. This paper contrasts near-term and future ground-based capabilities with high-contrast imaging modes of the James Webb Space Telescope (JWST). Monte Carlo modeling reveals that JWST can detect planets with masses as small as 0.2M_{Jup}_ across a broad range of orbital separations. We present new calculations for planet brightness as a function of mass and age for specific JWST filters and extending to 0.1M_{Jup}_.
- ID:
- ivo://CDS.VizieR/J/A+A/601/A76
- Title:
- DIRECT lightcurves of 21 luminous YSGs in M33
- Short Name:
- J/A+A/601/A76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The evolution of massive stars surviving the red supergiant (RSG) stage remains unexplored due to the rarity of such objects. The yellow hypergiants (YHGs) appear to be the warm counterparts of post-RSG classes located near the Humphreys-Davidson upper luminosity limit, which are characterized by atmospheric instability and high mass-loss rates. We aim to increase the number of YHGs in M33 and thus to contribute to a better understanding of the pre-supernova evolution of massive stars. Optical spectroscopy of five dust-enshrouded YSGs selected from mid-IR criteria was obtained with the goal of detecting evidence of extensive atmospheres. We also analyzed BVIc photometry for 21 of the most luminous YSGs in M33 to identify changes in the spectral type. To explore the properties of circumstellar dust, we performed SED-fitting of multi-band photometry of the 21 YSGs. We find three luminous YSGs in our sample to be YHG candidates, as they are surrounded by hot dust and are enshrouded within extended, cold dusty envelopes. Our spectroscopy of star 2 shows emission of more than one H{alpha} component, as well as emission of CaII, implying an extended atmospheric structure. In addition, the long-term monitoring of the star reveals a dimming in the visual light curve of amplitude larger than 0.5mag that caused an apparent drop in the temperature that exceeded 500K. We suggest the observed variability to be analogous to that of the Galactic YHG {rho} Cas. Five less luminous YSGs are suggested as post-RSG candidates showing evidence of hot or/and cool dust emission. We demonstrate that mid-IR photometry, combined with optical spectroscopy and time-series photometry, provide a robust method for identifying candidate YHGs. Future discovery of YHGs in Local Group galaxies is critical for the study of the late evolution of intermediate-mass massive stars.
- ID:
- ivo://CDS.VizieR/J/AJ/121/2032
- Title:
- Direct variables in M33A field
- Short Name:
- J/AJ/121/2032
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- DIRECT is a project to directly obtain the distances to two Local Group galaxies, M31 and M33, which occupy a crucial position near the bottom of the cosmological distance ladder. As the first step of the DIRECT project, we have searched for detached eclipsing binaries (DEBs) and new Cepheids in the M31 and M33 galaxies with 1 m class telescopes. In this paper, we present a catalog of variable stars discovered in the data from the follow-up observations of the DEB system D33J013346.2+304439.9 in field M33A (RA=23.55{deg}, DE=30.72{deg}; J2000.0), collected with the Kitt Peak National Observatory's 2.1 m telescope. In our search covering an area of 108arcmin^2^, we have found 434 variable stars: 63 eclipsing binaries, 305 Cepheids, and 66 other periodic, possible long-period, or nonperiodic variables. Of these variables, 280 are newly discovered, mainly short-period and/or faint Cepheids. Their light curves were extracted using the ISIS image subtraction package. For 85% of the variables, we present light curves in standard V and B magnitudes, with the remaining 15% expressed in units of differential flux. We have discovered a population of first-overtone Cepheid candidates, and for eight of them we present strong arguments in favor of this interpretation. We also report on the detection of a nonlinearity in the KPNO T2KA and T1KA cameras.
- ID:
- ivo://CDS.VizieR/J/AJ/122/2477
- Title:
- DIRECT variables in M33B field
- Short Name:
- J/AJ/122/2477
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- DIRECT is a project to obtain directly the distances to two Local Group galaxies, M31 and M33, which occupy a crucial position near the bottom of the cosmological distance ladder. As the first step of the DIRECT project we have searched for detached eclipsing binaries (DEBs) and new Cepheids in the M31 and M33 galaxies with 1m class telescopes. In this eighth paper we present a catalog of variable stars discovered in the data from the follow-up observations of DEB system D33J013337.0+303032.8 in field M33B [(RA,DE)=(23.48{deg}, 30.57{deg}), J2000.0], collected with the Kitt Peak National Observatory 2.1m telescope. In our search covering an area of 108arcmin^2^ we have found 895 variable stars: 96 eclipsing binaries, 349 Cepheids, and 450 other periodic, possibly long-period or nonperiodic variables. Of these variables 612 are newly discovered. Their light curves were extracted using the ISIS image subtraction package. For 77% of the variables we present light curves in standard V and B magnitudes, with the remaining 23% expressed in units of differential flux. We have discovered a population of first-overtone Cepheid candidates, and for six of them we present strong arguments in favor of this interpretation. The catalog of variables, as well as their photometry (about 9.2x10^4^ BV measurements) and finding charts, is available electronically via anonymous ftp and the World Wide Web. The complete set of the CCD frames is available upon request.