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2201. Rotational spectrum of ethyl isocyanate
ID:
ivo://CDS.VizieR/J/A+A/616/A173
Title:
Rotational spectrum of ethyl isocyanate
Short Name:
J/A+A/616/A173
Date:
21 Oct 2021
Publisher:
CDS
Description:
Relatively high abundances of methyl isocyanate (CH_3_NCO), a methyl derivative of isocyanic acid (HNCO), found in the Orion KL and Sgr B2 molecular clouds suggest that its ethyl derivative, ethyl isocyanate (CH_3_CH_2_NCO), may also be present. The aim of this work is to provide accurate experimental frequencies of ethyl isocyanate in its ground and excited vibrational states in the millimeter wave region to support searches for it in the interstellar medium. The rotational spectrum of ethyl isocyanate was recorded at room temperature from 80 to 340GHz using the millimeter wave spectrometer in Valladolid. Assigned rotational transitions were analyzed using the S-reduced semirigid-rotor Hamiltonian. More than 1100 distinct frequency lines were analyzed for the ground vibrational state of the cis conformer as well as for three vibrational satellites corresponding to successive excitation of the lowest-energy C-N torsional mode. Newly determined rotational and centrifugal distortion constants were used for searches of spectral features of ethyl isocyanate in Orion KL and Sgr B2 clouds. Upper limits to CH_3_CH_2_NCO in these high-mass star-forming regions were obtained.
2202. Rotational spectrum of methoxyacetaldehyde
ID:
ivo://CDS.VizieR/J/A+A/619/A67
Title:
Rotational spectrum of methoxyacetaldehyde
Short Name:
J/A+A/619/A67
Date:
21 Oct 2021
Publisher:
CDS
Description:
Methoxyacetaldehyde belongs to a group of structural isomers with the general formula C_3_H_6_O_2_, of which methyl acetate and ethyl formate are known interstellar molecules. Rotational data available for methoxyacetaldehyde are limited to 40GHz, which makes predictions at higher frequencies rather uncertain. The aim of this work is to provide accurate experimental frequencies of methoxyacetaldehyde in the millimeter-wave region to support its detection in the interstellar medium. The rotational spectrum of methoxyacetaldehyde was recorded at room-temperature from 75 to 120GHz and from 170 to 310GHz using the millimeter-wave spectrometer in Valladolid. Additional measurements were also performed at conditions of supersonic expansion from 6 to 18GHz. The assigned rotational transitions were analyzed using the S-reduced semirigid-rotor Hamiltonian. We newly assigned over 1000 lines for the most stable conformer of methoxyacetaldehyde in its ground state and five lowest excited vibrational states, and precise sets of spectroscopic constants were obtained. We searched for spectral features of methoxyacetaldehyde in the high-mass star-forming regions Orion KL and Sagittarius B2, as well as in the cold dark cloud Barnard 1 (B1-b). No lines belonging to methoxyacetaldehyde were detected above the detection limit of our data. We provide upper limits to the methoxyacetaldehyde colum density in these sources.
2203. Rotational spectrum of methoxyamine
ID:
ivo://CDS.VizieR/J/A+A/609/A24
Title:
Rotational spectrum of methoxyamine
Short Name:
J/A+A/609/A24
Date:
21 Oct 2021
Publisher:
CDS
Description:
Methoxyamine is a potential interstellar amine that has been predicted by gas-grain chemical models for the formation of complex molecules. The aim of this work is to provide direct experimental frequencies of its ground-vibrational state in the millimeter and submillimeter-wave regions to achieve its detection in the interstellar medium. Methoxyamine was chemically liberated from its hydrochloride salt, and its rotational spectrum was recorded at room temperature from 75 to 480GHz using the millimeter-wave spectrometer in Valladolid. Many observed transitions revealed A-E splitting caused by the internal rotation of the methyl group, which had to be treated with specific internal rotation codes. Over 400 lines were newly assigned for the most stable conformer of methoxyamine, and a precise set of spectroscopic constants was obtained. Spectral features of methoxyamine were then searched for in the Orion KL, Sgr B2, B1-b, and TMC-1 molecular clouds. Upper limits to the column density of methoxyamine were derived.
2204. Rotational spectrum of propiolamide
ID:
ivo://CDS.VizieR/J/A+A/647/A55
Title:
Rotational spectrum of propiolamide
Short Name:
J/A+A/647/A55
Date:
21 Oct 2021
Publisher:
CDS
Description:
For all the amides detected in the interstellar medium (ISM), the corresponding nitriles or isonitriles have also been detected in the ISM, some of which have relatively high abundances. Among the abundant nitriles for which the corresponding amide has not yet been detected is cyanoacetylene (HCCCN), whose amide counterpart is propiolamide (HCCC(O)NH_2_). With the aim of supporting searches for this amide in the ISM, we provide a complete rotational study of propiolamide from 6GHz to 440GHz. Time-domain Fourier transform microwave (FTMW) spectroscopy under supersonic expansion conditions between 6GHz and 18GHz was used to accurately measure and analyze ground-state rotational transitions with resolved hyperfine structure arising from nuclear quadrupole coupling interactions of the 14N nucleus. We combined this technique with the frequency-domain roomtemperature millimeter wave and submillimeter wave spectroscopies from 75GHz to 440GHz in order to record and assign the rotational spectrain the ground state and in the low-lying excited vibrational states. We used the ReMoCA spectral line survey performed with the Atacama Large Millimeter/submillimeter Array toward the star-forming region Sgr B2(N) to search for propiolamide. We identified and measured more than 5500 distinct frequency lines of propiolamide in the laboratory. These lines were fitted using an effective semi-rigid rotor Hamiltonian with nuclear quadrupole coupling interactions taken into consideration. We obtained accurate sets of spectroscopic parameters for the ground state and the three low-lying excited vibrational states. We report the nondetection of propiolamide toward the hot cores Sgr B2(N1S) and Sgr B2(N2). We find that propiolamide is at least 50 and 13 times less abundant than acetamide in Sgr B2(N1S) and Sgr B2(N2), respectively, indicating that the abundance difference between both amides is more pronounced by at least a factor of 8 and 2, respectively, than for their corresponding nitriles. Although propiolamide has yet to be included in astrochemical modeling networks, the observed upper limit to the ratio of propiolamide to acetamide seems consistent with the ratios of related species as determined from past simulations. The comprehensive spectroscopic data presented in this paper will aid future astronomical searches.
2205. Rotational transition frequencies of HCOOCH_3_
ID:
ivo://CDS.VizieR/J/ApJS/205/9
Title:
Rotational transition frequencies of HCOOCH_3_
Short Name:
J/ApJS/205/9
Date:
21 Oct 2021
Publisher:
CDS
Description:
The cis-methyl formate molecule (HCOOCH_3_) is a well known molecule found in interstellar space. Recently, rotational lines of methyl formate in the first CH_3_ torsional excited state were observed in Orion KL and W51e2. It is quite natural to observe methyl formate in even higher vibrational states considering the temperature estimated in Orion KL and W51e2. Maeda et al. (2008JMoSp.251..293M) reported results on the laboratory spectroscopy of methyl formate including the spectral analysis in its second CH_3_ torsional state. Their assignments were limited to a series of a-type R-branch lines and low K_a_ b-type R-branch transitions, and many assigned lines are excluded in the least-squares analysis. In the present study, we extended the line assignments of both the A- and E-species transitions in the second CH_3_ torsional state especially in the frequency region below the 120GHz region. By combining the present assignments and those made by Maeda et al., 1951 transitions in total for the second CH_3_ torsional state, 1096 A-species transitions up to J=39, and K_a_=15 and 855 E-species transitions up to J=35 and K_a_=13, were least-squares analyzed by using the pseudo-principal-axis-method Hamiltonian with 42 parameters consisting of rotational, centrifugal distortion, and internal rotational constants in the second CH_3_ torsional state. In addition, 1012 transitions out of 1096 A-species transitions could also be least-squares analyzed by using Watson's A-reduced Hamiltonian with 43 parameters, which can serve to calculate the energy levels of the A-species lines of molecules with the CH_3_ internal rotation conveniently.
2206. rotational transitions of cyanoacetamide
ID:
ivo://CDS.VizieR/J/A+A/644/A3
Title:
rotational transitions of cyanoacetamide
Short Name:
J/A+A/644/A3
Date:
21 Oct 2021
Publisher:
CDS
Description:
Cyanoacetamide is a branched chain -CN bearing molecule which is also an amide derivative target molecule in the interstellar medium. The aim of our investigation is to analyze the feasibility of a plausible formation process of protonated cyanoacetamide under interstellar conditions and to provide direct experimental frequencies of the ground vibrational state of the neutral form in the microwave region in order to enable its eventual identification in the interstellar medium. We used high-level theoretical computations to study the formation process of protonated cyanoacetamide. Furthermore, we employed a high resolution laser ablation molecular beam Fourier transform (LA-MB-FTMW) spectroscopic technique to measure the frequencies of the neutral form. We report the first rotational characterization of cyanoacetamide and a precise set of the relevant rotational spectroscopic constants have been determined as a first step to identify the molecule in the interstellar medium. We performed full exploration of the Potential Energy Surface (PES) to study a gas-phase reaction on the formation process of protonated cyanoacetamide. We found an exothermic process with no net activation barrier initiated by the high-energy isomer of protonated hydroxylamine, which leads to protonated cyanoacetamide.
2207. Rotational transitions of Methyl carbamate
ID:
ivo://CDS.VizieR/J/ApJS/169/28
Title:
Rotational transitions of Methyl carbamate
Short Name:
J/ApJS/169/28
Date:
21 Oct 2021
Publisher:
CDS
Description:
The rotational-torsional spectrum of the syn conformer of methyl carbamate [CH_3_OC(:O)NH_2_], an isomer of the essential amino acid glycine [NH_2_CH_2_C(:O)OH], has been recorded at room temperature in the spectral region from 79 to 371GHz. Methyl carbamate possesses a methyl group internal rotor, which gives rise to A and E torsional substates, and associated splittings in the rotational spectrum. Almost 6000 new rotational transitions arising from the vibrational ground state have been assigned, about half of them belonging to the E torsional substate. The Fast Scan Submillimeter-wave Spectroscopic Technique (FASSST) spectrometer at the Ohio State University was used for the present measurements
2208. Rotational Velocities of Intermediate-mass MS Stars
ID:
ivo://CDS.VizieR/J/PASP/109/759
Title:
Rotational Velocities of Intermediate-mass MS Stars
Short Name:
J/PASP/109/759
Date:
21 Oct 2021
Publisher:
CDS
Description:
(from Publ. Astron. Soc. Pac. 109, 759 (1997)) We analyze these rotation rates for a dependence on both mass and age. We compare the average rotation speeds of the field stars with mean velocities for young stars in Orion, the {Alpha} Persei cluster, the Pleiades, and the Hyades. The average rotation speeds of stars more massive than ~1.6 Msol experience little or no change during the evolutionary lifetimes of these stars on the zero age main sequence (ZAMS) or within the ZAMS band. Less massive stars in the range between 1.6 Msol and 1.3 Msol also show little decline in mean rotation rate while they are on the main sequence, and at most a factor of two decrease in velocity as they evolve off the main sequence. The e-folding time for the loss of angular momentum by the latter group of stars is at least 1-2 billion years. This inferred characteristic time scale for spindown is far longer than the established rotational braking time for solar-type stars with masses below ~1.3 Msol. We conclude from a comparison of the trends in rotation with trends in chromospheric and coronal activity that the overall decline in mean rotation speed along the main sequence, from ~2 Msol down to ~1.3 Msol, is imposed during the pre-main-sequence phase of evolution, and that this pattern changes little thereafter while the star resides on the main sequence. The magnetic activity must therefore play only a minor role in determining the rotation rates of the intermediate-mass stars, either because a solar-like dynamo is weak or absent, or else the geometry of the magnetic field is appreciably less effective in removing angular momentum from these stars.
2209. Rotational Velocities of 373 OB stars
ID:
ivo://CDS.VizieR/J/MNRAS/284/265
Title:
Rotational Velocities of 373 OB stars
Short Name:
J/MNRAS/284/265
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalogue of homogeneous measures of the linewidth parameter, v_e_.sin(i), for 373 O-type stars and early supergiants (including the separate components of 25 binary and triple systems), produced by cross-correlating high-resolution, short-wavelength IUE spectra against a `template' spectrum of {tau} Sco. We also tabulate terminal velocities. There are no O supergiants in our sample with v_e_.sin(i)<65km/s, and only one supergiant earlier than B5 has v_e_.sin(i)<50km/s, confirming that an important line broadening mechanism in addition to rotation must be present in these objects. A calibration of the area under the cross-correlation peak against spectral type is used to obtain estimates of continuum intensity ratios of the components in 28 spectroscopically binary or multiple systems. At least seven SB2 systems show evidence for the `Struve-Sahade effect', a systematic variation in relative line strength as a function of orbital phase. The stellar wind of the most rapid rotator in our sample, the O9III:n* star HD 191423 (v_e_.sin(i)<=436km/s), show it to have a `wind-compressed disc' similar to that of HD 93521; this star and other rapid rotators are good candidates for studies of non-radial pulsation.
2210. Rotation curves of early-type galaxies
ID:
ivo://CDS.VizieR/J/AJ/114/2402
Title:
Rotation curves of early-type galaxies
Short Name:
J/AJ/114/2402
Date:
21 Oct 2021
Publisher:
CDS
Description:
Optical long-slit rotation curves have been studied for 304 northern Sb-Sc galaxies from the Courteau-Faber (CF) sample designed for Tully-Fischer (TF) applications; r-band photometry exists also for each galaxy of the sample. The procedure of rotation curve (RC) extraction and construction of optical profiles are analogous to 21cm integrated linewidths. More than 20% of the galaxies were observed twice or more, allowing for a proper determination of systematic errors. Various measures of maximum rotational velocity to be used as input in the TF relation are tested on the basis of their repeatability, minimization of TF scatter, and match with 21cm linewidths. The best measure of TF velocity, V2.2 is given at the location of peak rotational velocity of a pure exponential disk. An alternative measure to V2.2 which makes no assumption about the luminosity profile or shape of the rotation curve is Vhist, the 20% width of the velocity histogram, though the match with 21cm linewidths is not good. The paper shows that optical TF calibrations yield internal scatter comparable to, if not smaller than, the best calibrations based on single-dish 21cm radio linewidths. Tables 6 and 7 contain the values of the parameters fitting the rotation curves of two samples of galaxies: the CF (Courteau-Faber) sample (table6) and the MAT (Mathewson et al., 1992ApJS...81..413M) sample (table7). Two fitting models were used: the ArcTan function (Model 1) where the velocity varies as v(r) = v(0) + K . arctan(R) (R being (r-r_0_)/r_t_) and a multi-parameter function (Model 2) modelling the rotation curve close to a solid-body close to the rotation center, and close to a flat rotation at large distances (see section 5 of the paper).

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