- ID:
- ivo://CDS.VizieR/J/AJ/147/22
- Title:
- Simultaneous SiO and H2O maser observations. IV.
- Short Name:
- J/AJ/147/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on the simultaneous observational results of SiO and H_2_O masers toward 401 evolved stars, we have performed statistical analyses. We find that the peak and integrated intensities of SiO masers are stronger than those of H_2_O masers in both Mira variables and OH/IR stars at most optical phases. However, the relative intensity ratios of H_2_O to SiO masers in OH/IR stars are larger than those in Mira variables. Moreover, the intensity ratios of H_2_O to SiO masers are found to be increased around the optical phases from 0-0.4. The H_2_O photon luminosities also tend to be more dependent on the optical phase compared with those of SiO masers. These facts suggest that H_2_O masers are more sensitive to expanding the motion of circumstellar envelopes and also shock waves arising from the pulsations of the central star compared with SiO masers. This result may also be related to the differences in the maser location and pumping mechanism between H_2_O and SiO masers. The full width at zero power of SiO masers in Mira variables shows similar values to those of OH/IR stars, while those of H_2_ O masers in OH/IR stars show larger values than those of Mira variables. These differences may originate from the different mass-loss rates and the different location of the two masers. The mean velocity shift of SiO and H_2_O masers with respect to the stellar velocity was investigated as a function of optical phase. The velocity shift of the H_2_O masers shows that the redshifted emission dominates during the phases from 0.3-0.6, while the blueshifted emission appears at phase 0.6 and coexists with the redshifted emission during other phases. These features show an associated pattern with the CO {Delta}V=3 radial velocity curve, which exhibits a typical pulsation motion. On the other hand, the velocity shift of the SiO v=2 maser shows slightly similar features to the H_2_O maser, while that of SiO v=1 does not show these similar features. Finally, the distributions of all 401 observed sources are investigated in the IRAS two-color diagram in relation to the late evolutionary processes of asymptotic giant branch stars.
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- ID:
- ivo://CDS.VizieR/J/A+A/565/A127
- Title:
- SiO masers v=1,2,3 for 4 AGB
- Short Name:
- J/A+A/565/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The v=1 and 2 J=1-0 (43GHz), and v=1 J=2-1 (86GHz) SiO masers are intense in AGB stars and have been mapped using VLBI showing ring-like distributions. Those of the v=1, 2 J=1-0 masers are similar, but the spots are rarely coincident, while the v=1 J=2-1 maser arises from a well separated region farther out. These relative locations can be explained by models including the overlap of two IR lines of SiO and H_2_O. The v=3 J=1-0 line is not directly affected by any line overlap and its spot structure and position, relative to the other lines, will be a good test to the standard pumping models The aims is to gain insight into the properties of the different SiO masers and the general theoretical considerations that can help to understand them. We present single-dish and VLBI simultaneous observations of the v=1, 2, 3 J=1-0 maser transitions of ^28^SiO in several AGB stars. The results are compared with the predictions of radiative models of SiO masers both including and not including the effect of IR line overlap. The spatial distribution of the SiO maser emission in the v=3 J=1-0 transition from AGB stars is systematically composed of a series of spots occupying a ring-like structure (as often found in SiO masers). The overall ring structure is extremely similar to that found in the other 43 GHz transitions, and very different from the structure of the v=1 J=2-1 maser. The positions of the individual spots of the different 43 GHz lines are however very rarely coincident, being in general separated by about 0.3AU (between 1 and 5mas). These results are very difficult to reconcile with standard pumping models, which predict the masers of rotational transitions within a given vibrational state to require very similar excitation conditions (since the levels are placed practically at the same energy from the ground), while the transitions of different vibrational states (which are separated by an energy of 1800K) should appear in different positions. However, models including line overlap tend to predict v=1, 2, 3 J=1-0 population inversion to occur under very similar conditions, while the requirements for v=1 J=2-1 appears clearly different, and are compatible with the observational results.
- ID:
- ivo://CDS.VizieR/V/68A
- Title:
- Stellar Maser Observations
- Short Name:
- V/68A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog contains about 2958 stellar sources. For the searching of the maser emission of the sources listed, 368 were detected in H2O, 209 in SiO, and 713 in OH. In the catalog, one can find information about the stars including alternate names, the 1950 epoch position, velocity (LSR), spectral type, variability type, and period, as well as the references for both the detections and nondetections for each of the three molecules. In this catalog, Table 1 lists all the sources in right ascension order, Table 2 lists the references for all the maser observations for each source, and Table 3 lists the references in code order, i.e., in chronological order.
- ID:
- ivo://CDS.VizieR/J/ApJ/707/1
- Title:
- Water and Methanol masers in NGC 6334I(N)
- Short Name:
- J/ApJ/707/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a high-resolution, multi-wavelength study of the massive protostellar cluster NGC 6334 I(N) that combines new spectral line data from the Submillimeter Array (SMA) and VLA with a re-analysis of archival VLA continuum data, Two Micron All Sky Survey and Spitzer images. As shown previously, the brightest 1.3mm source SMA1 contains substructure at subarcsecond resolution, and we report the first detection of SMA1b at 3.6cm along with a new spatial component at 7mm (SMA1d). We find SMA1 (aggregate of sources a, b, c, and d) and SMA4 to be comprised of free-free and dust components, while SMA6 shows only dust emission. Our 1.5" resolution 1.3mm molecular line images reveal substantial hot-core line emission toward SMA1 and to a lesser degree SMA2. We find CH_3_OH rotation temperatures of 165+/-9K and 145+/-12K for SMA1 and SMA2, respectively. We estimate a diameter of 1400AU for the SMA1 hot-core emission, encompassing both SMA1b and SMA1d, and speculate that these sources comprise a >~800AU separation binary that may explain the previously suggested precession of the outflow emanating from the SMA1 region. Compact line emission from SMA4 is weak, and none is seen toward SMA6. The LSR velocities of SMA1, SMA2, and SMA4 all differ by 1-2km/s. Outflow activity from SMA1, SMA2, SMA4, and SMA6 is observed in several molecules including SiO(5-4) and IRAC 4.5um emission; 24um emission from SMA4 is also detected. Eleven water maser groups are detected, eight of which coincide with SMA1, SMA2, SMA4, and SMA6, while two others are associated with the Sandell source SM2. We also detect a total of 83 Class I CH_3_OH 44GHz maser spots which likely result from the combined activity of many outflows. Our observations paint the portrait of multiple young hot cores in a protocluster prior to the stage where its members become visible in the near-infrared.
