- ID:
- ivo://CDS.VizieR/J/A+A/631/A48
- Title:
- rho Cas differential BVRI photometry
- Short Name:
- J/A+A/631/A48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to explore the variable photometric and stellar properties of four yellow hypergiants (YHGs), HR 8752, HR 5171A, rho Cas, and HD 179821, and their pulsations of hundreds of days, and long-term variations (LTVs) of years. We also aim to explore light and colour curves for characteristics betraying evolutionary loops and eruptive episodes and to investigate trends of quasi-periods and the possible need for distance revisions. We tackled multi-colour and visual photometric data sets, looked for photometric indications betraying eruptions or enhanced mass-loss episodes, calculated stellar properties mainly using a previously published temperature calibration, and investigated the nature of LTVs and their influence on quasi-periods and stellar properties. Based on driven one-zone stellar oscillation models, the pulsations can be characterised as 'weakly chaotic'. The BV photometry revealed a high-opacity layer in the atmospheres. When the temperature rises the mass loss increases as well, consequently, as the density of the high-opacity layer. As a result, the absorption in B and V grow. The absorption in B, presumably of the order of one to a few 0.1mag, is always higher than in V. This difference renders redder and variable (B-V) colour indexes, but the absorption law is unknown. This property of YHGs is unpredictable and explains why spectroscopic temperatures (reddening independent) are always higher than photometric ones, but the difference decreases with the temperature. A new (weak) eruption of rho Cas has been identified. We propose shorter distances for rho Cas and HR 5171A than the accepted ones. Therefore, a correction to decrease the blue luminescence of HR 5171A by polycyclic aromatic hydrocarbon (PAH) molecules is necessary, and HR 5171A would no longer be a member of the cluster Gum48d. HR 5171A is only subject to one source of light variation, not by two as the literature suggests. Eruptive episodes (lasting one to two years), of YHGs prefer relatively cool circumstances when a red evolutionary loop (RL) has shifted the star to the red on the HR diagram. After the eruption, a blue loop evolution (BL) is triggered lasting one to a few decades. We claim that in addition to HR 8752, also the other three YHGs have shown similar cycles over the last 70 years. This supports the suspicion that HD 179821 might be a YHG (with a possible eruptive episode between 1925 and 1960). The range in temperature of these cyclic Teff variations is 3000K-4000K. LTVs mainly consist of such BL and RL evolutions, which are responsible for a decrease and increase, respectively, of the quasi-periods. The reddening episode of HR 5171A between 1960 and 1974 was most likely due to a red loop evolution, and the reddening after the 1975 eruption was likely due to a shell ejection, taking place simultaneously with a blue loop evolution.
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- ID:
- ivo://CDS.VizieR/J/ApJS/112/109
- Title:
- Rho Oph Near-IR Positions and Photometry
- Short Name:
- J/ApJS/112/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog contains the tabulated results from a three-color (JHK) near-Infrared imaging survey of the Rho Ophiuchi star-forming cloud core. The NIR imaging observations were acquired using the SQIID instrument on the Kitt Peak 1.3m telescope from June 4-10, 1993 and April 23-28, 1994. The survey covered one square degree (2.2pc by 2.2pc). The catalog contains 4495 sources with both J2000.0 and B1950.0 coordinates for each source and its J, H, and K magnitudes and/or upper their limits. The Rho Ophiuchi clouds are of great interest for star formation studies, since they include the nearest example of a currently forming star cluster. The absolute positions in RA and Dec were determined for each individual source by using a centering algorithm in the IRAF package APPHOT to obtain center positions in pixels which were then merged into a single common positional grid. Absolute stellar coordinates were determined by comparing the authors positional database with the positions of 36 HST Guide Star Catalog stars spread out over the survey field. These were used to determine a plate scale and rotation which was used to generate the final list of source positions. The position determination technique and the photometric data reduction and calibration is discussed in detail in the source reference.
- ID:
- ivo://CDS.VizieR/J/A+A/605/A82
- Title:
- Rosette Nebula globules
- Short Name:
- J/A+A/605/A82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Rosette nebula is an HII region ionized mainly by the stellar cluster NGC 2244. Elephant trunks, globules, and globulettes are seen at the interface where the HII region and the surrounding molecular shell meet. We have observed a field in the northwestern part of the Rosette nebula where we study the small globules protruding from the shell. Our aim is to measure their properties and study their star-formation history in continuation of our earlier study of the features of the region. We imaged the region in broadband near-infrared (NIR) JsHKs filters and narrowband H_2_ 1-0 S(1), P{beta}, and continuum filters using the SOFI camera at the ESO/NTT. The imaging was used to study the stellar population and surface brightness, create visual extinction maps, and locate star formation. Mid-infrared (MIR) Spitzer IRAC and WISE and optical NOT images were used to further study the star formation and the structure of the globules. The NIR and MIR observations indicate an outflow, which is confirmed with CO observations made with APEX.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A123
- Title:
- Rotational spectroscopy of CH_2_OH
- Short Name:
- J/A+A/644/A123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The hydroxymethyl radical (CH_2_OH) is one of the two structural isomers, together with the methoxy radical (CH_3_O), that can be produced by abstraction of a hydrogen atom from methanol (CH_3_OH). In the interstellar medium (ISM), both CH_2_OH and CH_3_O are suspected to be intermediate species in many chemical reactions, including those of formation and destruction of methanol. The determination of the CH_3_O/CH_2_OH ratio in the ISM would bring important information concerning the formation processes of these species in the gas and solid phases. Interestingly, only CH_3_O has been detected in the ISM so far, despite the recent first laboratory measurement of the CH_2_OH rotation-tunneling spectrum. This lack of detection is possibly due to the non-observation in the laboratory of the most intense rotational-tunneling transitions at low temperature. To support further searches for the hydroxymethyl radical in space, we have performed a thorough spectroscopic study of its rotation-tunneling spectrum, with particular focus on transitions involving the lowest quantum numbers of the species. We have recorded the rotation-tunneling spectrum of CH_2_OH at room temperature in the millimeter-wave domain using a frequency multiplication chain spectrometer associated to a fluorine-induced H-abstraction method. The radical was produced from methanol precursor. About 180 transitions were observed including those involving the lowest N and Ka quantum numbers, predicted intense under cold astrophysical conditions. These transitions were fitted together with available millimeter-wave lines from the literature. The systematic observation of all components of the rotational transitions yields a large improvement of the spectroscopic parameters which now allow confident searches of the hydroxymethyl radical in cold to warm environments of the ISM.
- ID:
- ivo://CDS.VizieR/J/ApJ/714/1120
- Title:
- Rotational spectrum and DCOOCH_3_ in Orion
- Short Name:
- J/ApJ/714/1120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New centimeter-wave (7-80GHz) and submillimeter-wave (580-661GHz) spectra of a deuterated species of methyl formate (DCOOCH_3_) have been measured. Transitions with a maximum value of J=64 and K=36 have been assigned and fitted together with previous measurements. The internal rotation of this compound was treated using the so-called rho axis method (RAM). A total of 1703 transitions were fitted using this method. Only 24 parameters were employed in the final fit, which has an rms deviation of 94.2kHz. The dipole moment and the nuclear quadrupole coupling constants of the deuterated species have also been obtained. This new study has permitted a tentative detection of DCOOCH_3_ in Orion with the IRAM 30m telescope based on the observation of more than 100 spectral features with low blending effects among the 400 lines expected in the observed frequency domain (for which over 300 are heavily blended with other species). These 100 transitions are above noise and confusion limited without heavy blending and cannot be assigned to any other species. Moreover, none of the strongest unblended transitions is missing. The derived source-averaged total column density for DCOOCH_3_ is 7.8x10^14^cm^-2^ and the DCOOCH_3_/HCOOCH_3_ column density ratio varies between 0.02 and 0.06 in the different cloud components of Orion. This value is consistent with the deuteration enhancement found for other species in this cloud.
- ID:
- ivo://CDS.VizieR/J/A+A/538/A51
- Title:
- Rotational spectrum of CH_3_CH(NH_2_)CN
- Short Name:
- J/A+A/538/A51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- No chiral molecule has been detected in the interstellar medium (ISM) so far. A good candidate for an interstellar detection is 2-aminopropionitrile (CH_3_CH(NH_2_)CN), a chiral and the simplest molecule with a C_3_H_6_N_2_ formula. The first member of this series, aminoacetonitrile (H_2_NCH_2_CN), was recently detected, demonstrating that at least one aminonitrile exist in the ISM. Experimental spectra of 2-aminopropionitrile have been recorded in the microwave and sub-mm energy range (8-80GHz, 150-660GHz). An unbiased spectral survey of the 80-116GHz atmospheric window performed with the IRAM 30m telescope is used to search for this molecule in the hot core Sgr B2(N). This survey is analysed in the local thermodynamical equilibrium (LTE) approximation. The emission of 2-aminopropionitrile is modeled simultaneously with the emission of all molecules known in Sgr B2(N), which allows to properly take into account line blending and avoid mis-assignments. Only 10 groups of transitions of 2-aminopropionitrile are not severely affected by line blending in the Sgr B2(N) spectrum. Six of them could be considered as tentatively detected but the LTE predictions of the four remaining groups are not (or only marginally) consistent with the observed spectrum. Therefore, only an upper limit of 1.7*10^16^cm^-2^ can be securely derived for the column density of 2-aminopropionitrile toward Sgr B2(N).
- ID:
- ivo://CDS.VizieR/J/A+A/587/A152
- Title:
- Rotational spectrum of ^13^C methylamine
- Short Name:
- J/A+A/587/A152
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Methylamine (CH_3_NH_2_) is a light molecule of astrophysical interest, which has an intensive rotational spectrum that extends in the submillimeter wave range and far beyond, even at temperatures characteristic for the interstellar medium. It is likely for ^13^C isotopologue of methylamine to be identified in astronomical surveys, but there is no information available for the ^13^CH_3_NH_2_ millimeter and submillimeter wave spectra. In this context, to provide reliable predictions of ^13^CH_3_NH_2_ spectrum in millimeter and submillimeter wave ranges, we have studied rotational spectra of the 13C methylamine isotopologue in the frequency range from 48 to 945GHz. The spectrum of ^13^C methylamine was recorded using conventional absorption spectrometers in Lille and Kharkov. The analysis of the rotational spectrum of ^13^C methylamine in the ground vibrational state was performed on the basis of the group- theoretical high-barrier tunneling Hamiltonian that was developed for methylamine by Ohashi and Hougen. The available multiple observations of the parent methylamine species toward Sgr B2(N) at 1, 2, and 3mm using the Submillimeter Telescope and the 12 m antenna of the Arizona Radio Observatory were used to make a search for interstellar ^13^CH_3_NH_2_. In the recorded spectra, we have assigned 2721 rotational transitions that belong to the ground vibrational state of the ^13^CH_3_NH_2_. These measurements were fitted to the Hamiltonian model that uses 75 parameters to achieve an overall weighted rms deviation of 0.73. On the basis of these spectroscopic results, predictions of transition frequencies in the frequency range up to 950GHz with J<50 and Ka<20 are presented. The search for interstellar ^13^C methylamine in available observational data was not successful and therefore only an upper limit of 6.5x10^14^cm^-2^ can be derived for the column density of ^13^CH_3_NH_2_ toward Sgr B2(N), assuming the same source size, temperature, linewidth, and systemic velocity as for parent methylamine isotopic species.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/500/1109
- Title:
- Rotational spectrum of HCOO^13^CH_3_
- Short Name:
- J/A+A/500/1109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Laboratory measurements and analysis of the microwave and millimeter-wave spectra of potential interstellar molecules are a prerequisite for their subsequent identification by radioastronomical techniques. The spectral analysis provides spectroscopic parameters that are used in the assignment procedure of the laboratory spectra, and that also predict the frequencies of transitions not measured in the laboratory with a high degree of precision. An experimental laboratory study and its theoretical analysis is presented for ^13^C_2_-methyl formate (HCOO^13^CH_3_) allowing a search for this isotopologue in the Orion molecular cloud. The ^13^C_1_-methyl formate (H^13^COOCH_3_) molecule was also searched for in this interstellar cloud, using previously published spectroscopic data.
- ID:
- ivo://CDS.VizieR/J/ApJS/190/315
- Title:
- Rotational spectrum of H^13^COOCH_3_
- Short Name:
- J/ApJS/190/315
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A compilation of the available spectroscopic millimeter- and submillimeter-wave data of the ground and first excited states of ^13^C_1_-methyl formate (H^13^COOCH_3_) has been carried out. The exhaustive analysis of the available transition lines of H^13^COOCH_3_ has led to the assignment of 7457 spectral lines by means of a global fit of 45 parameters, using the Rho-Axis Method (RAM) and the BELGI-Cs code, with a resulting unitless standard deviation of 0.57. Over 1600 lines are included for the first time in the fit. In addition, the line strengths of spectral lines are also calculated using the most recent experimental measurement of the electric dipole moment. In conclusion, the present study represents a notable improvement with respect to previous H^13^COOCH_3_ spectral analyses. Therefore, the better accuracy of the present analysis may help the future identification of new H^13^COOCH_3_ lines in the interstellar and circumstellar media, and may contribute to decrease some of the spectral confusion due to these species in astronomical surveys.