- ID:
- ivo://CDS.VizieR/J/A+A/485/95
- Title:
- Velocities of F-G-K stars in Blanco 1
- Short Name:
- J/A+A/485/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The nearby open cluster Blanco 1 is of considerable astrophysical interest for formation and evolution studies of open clusters because it is the third highest Galactic latitude cluster known. It has been observed often, but so far no definitive and comprehensive membership determination is readily available. An observing programme was carried out to study the stellar population of Blanco 1, and especially the membership and binary frequency of the F5-K0 dwarfs. We obtained radial-velocities with the CORAVEL spectrograph in the field of Blanco 1 for a sample of 148 F-G-K candidate stars in the magnitude range 10<V<14. New proper motions and UBVI CCD photometric data from two extensive surveys were obtained independently and are used to establish reliable cluster membership assignments in concert with radial-velocity data. The membership of 68 stars is confirmed on the basis of proper motion, radial velocity, and photometric criteria. Fourteen spectroscopic- and suspected binaries (2 SB2s, 9 SB1s, 3SB?) have been discovered among the confirmed members. Thirteen additional stars are located above the main sequence or close to the binary ridge, with radial velocities and proper motions supporting their membership. These are probable binaries with wide separations. Nine binaries (7 SB1 and 2 SB2) were detected among the field stars. The spectroscopic binary frequency among members is 20% (14/68); however, the overall binary rate reaches 40% (27/68) if one includes the photometric binaries. The cluster mean heliocentric radial velocity is +5.53+/-0.11km/s based on the most reliable 49 members. The Vsini distribution is similar to that of the Pleiades, confirming the age similarities between the two clusters.
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- ID:
- ivo://CDS.VizieR/J/AJ/147/150
- Title:
- Velocities of globular clusters in M104
- Short Name:
- J/AJ/147/150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained radial velocity measurements for 51 new globular clusters around the Sombrero galaxy. These measurements were obtained using spectroscopic observations from the AAOmega spectrograph on the Anglo-Australian Telescope and the Hydra spectrograph at WIYN. Combining our own past measurements and velocity measurements obtained from the literature, we have constructed a large database of radial velocities that contains a total of 360 confirmed globular clusters. Previous studies' analyses of the kinematics and mass profile of the Sombrero globular cluster system have been constrained to the inner ~9' (~24kpc or ~5R_e_), but our new measurements have increased the radial coverage of the data, allowing us to determine the kinematic properties of M104 out to ~15' (~41kpc or ~9R_e_). We use our set of radial velocities to study the GC system kinematics and to determine the mass profile and V-band mass-to-light profile of the galaxy. We find that M/L_V_ increases from 4.5 at the center to a value of 20.9 at 41kpc (~9R_e_ or 15'), which implies that the dark matter halo extends to the edge of our available data set. We compare our mass profile at 20kpc (~4R_e_or ~7.4') to the mass computed from X-ray data and find good agreement. We also use our data to look for rotation in the globular cluster system as a whole, as well as in the red and blue subpopulations. We find no evidence for significant rotation in any of these samples.
- ID:
- ivo://CDS.VizieR/J/ApJ/676/1109
- Title:
- Velocities of stars in the Orion Nebula Cluster
- Short Name:
- J/ApJ/676/1109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from 1351 high-resolution spectra of 1215 stars in the Orion Nebula Cluster (ONC) and the surrounding Orion 1c association, obtained with the Hectochelle multiobject echelle spectrograph on the 6.5m MMT. We confirmed 1111 stars as members, based on their radial velocity and/or H{alpha} emission. The radial velocity distribution of members shows a dispersion of {sigma}=3.1km/s. We found a substantial north-south velocity gradient and spatially coherent structure in the radial velocity distribution, similar to that seen in the molecular gas in the region. We also identified several binary and high velocity stars, a region exhibiting signs of triggered star formation, and a possible foreground population of stars somewhat older than the ONC.
- ID:
- ivo://CDS.VizieR/J/AJ/156/300
- Title:
- Velocity and light curve analysis of three PPNe
- Short Name:
- J/AJ/156/300
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained contemporaneous light, color, and radial velocity data for three proto-planetary nebulae (PPNe) over the years 2007 to 2015. The light and velocity curves of each show similar periods of pulsation, with photometric periods of 42 and 50 days for IRAS 17436+5003, 102 days for IRAS 18095+2704, and 35 days for IRAS 19475+3119. The light and velocity curves are complex with multiple periods and small, variable amplitudes. Nevertheless, at least over limited time intervals, we were able to identify dominant periods in the light, color, and velocity curves and compare the phasing of each. The color curves appear to peak with or slightly after the light curves while the radial velocity curves peak about a quarter of a cycle before the light curves. Similar results were found previously for two other PPNe, although for them the light and color appeared to be in phase. Thus, it appears that PPNe are brightest when smallest and hottest. These phase results differ from those found for classical Cepheid variables, where the light and velocity differ by half a cycle, and are hottest at about average size and expanding. However, they do appear to have similar phasing to the larger-amplitude pulsations seen in RV Tauri variables. Presently, few pulsation models exist for PPNe, and these do not fit the observations well, especially the longer periods observed. Model fits to these new light and velocity curves would allow masses to be determined for these post-AGB objects, and thereby provide important constraints to post-AGB stellar evolution models of low- and intermediate-mass stars.
- ID:
- ivo://CDS.VizieR/J/A+A/389/795
- Title:
- Vertical structure of edge-on galaxies
- Short Name:
- J/A+A/389/795
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To analyze the vertical structure of edge-on galaxies, we have used images of a large uniform sample of flat galaxies that have been taken during the 2MASS all-sky survey. The photometric parameters, such as the radial scale length, the vertical scale height, and the deprojected central surface brightness of galactic disks have been obtained. We find a strong correlation between the central surface brightness and the ratio of the vertical scale height to the vertical scale length: the thinner the galaxy, the lower the central surface brightness of its disk. The vertical scale height does not increase systematically with the distance from the galaxy center in the frames of this sample.
- ID:
- ivo://CDS.VizieR/J/ApJS/225/26
- Title:
- Very Low-Luminosity Objects (VeLLOs) from 1.25-850um
- Short Name:
- J/ApJS/225/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for Very Low-Luminosity Objects (VeLLOs) in the Gould Belt (GB) clouds using infrared and sub-millimeter (sub-mm) data from 1.25 to 850{mu}m and our N_2_H^+^(J=1-0) observations. We modified the criteria by Dunham et al. (2008, J/ApJS/179/249) to select the VeLLOs in the GB clouds, finding 95 VeLLO candidates, 79 of which are newly identified in this study. Out of 95 sources, 44 were detected in both sub-mm continuum and N_2_H^+^ emission and were classified as Group A (the VeLLOs), and 51 sources detected in either sub-mm emission or N_2_H^+^ emission were classified with Group B as candidate VeLLOs. We find that these VeLLOs and the candidates are forming in environments different from those of the likely VeLLOs. Seventy-eight sources are embedded within their molecular clouds, and thus are likely VeLLOs forming in a dense environment. The remaining 17 sources are located in low-level extinction regions (A_V_<1) connected to the clouds, and can be either background sources or candidate substellar objects forming in an isolated mode. The VeLLOs and the candidates are likely more luminous and their envelopes tend to be more massive in denser environments. The VeLLOs and the candidates are more populous in the clouds where more YSOs form, indicating that they form in a manner similar to that of normal YSOs. The bolometric luminosities and temperatures of the VeLLOs are compared to predictions of episodic accretion models, showing that the low luminosities for most VeLLOs can be well explained by their status in the quiescent phases of a cycle of episodic mass accretion.
- ID:
- ivo://CDS.VizieR/J/A+A/515/A13
- Title:
- Very low mass objects in ONC
- Short Name:
- J/A+A/515/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Angular momentum (J) loss requires magnetic interaction between the forming star and both the circumstellar disk and the magnetically driven outflows. In order to test these predictions many authors have investigated a rotation-disk connection in pre-main sequence objects with masses larger than about 0.4M_{sun}_. For brown dwarfs (BDs) this connection was not investigated as yet because there are very few samples available. We aim to extend this investigation well down into the substellar regime for our large sample of ~~80 BDs in the Orion Nebula Cluster, for which we have recently measured rotational periods.
- ID:
- ivo://CDS.VizieR/J/A+A/510/A27
- Title:
- Very low mass stars in Praesepe
- Short Name:
- J/A+A/510/A27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Determination of the mass functions of open clusters of different ages allows us to infer the efficiency with which brown dwarfs are evaporated from clusters to populate the field. In this paper we present the results of a photometric survey to identify low mass and brown dwarf members of the old open cluster Praesepe (age 590^+150^_-120_Myr, distance 190^+6.0^_-5.8_pc) from which we estimate its mass function and compare this with that of other clusters. We performed an optical (Ic-band) and near-infrared (J and Ks-band) photometric survey of Praesepe covering 3.1{deg}^2^. With 5sigma detection limits of Ic=23.4 and J=20.0, our survey is predicted to be sensitive to objects with masses from 0.6 to 0.05M_{sun}.
- ID:
- ivo://CDS.VizieR/J/AJ/136/1372
- Title:
- Very low-mass YSOs in NGC 1333
- Short Name:
- J/AJ/136/1372
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a deep near-infrared (NIR) imaging survey searching for very low mass young stellar objects (YSOs) in the embedded cluster associated with the Perseus molecular cloud. Our observations cover an area of ~5'x5' in the NGC 1333-S region at J-, H-, and Ks-bands. The 10{sigma} limiting magnitudes exceed 18mag in all three bands. Based on NIR color-color diagrams, embedded YSO candidates were identified using NIR excesses.
- ID:
- ivo://CDS.VizieR/J/ApJ/713/615
- Title:
- Very metal-poor Cepheid models
- Short Name:
- J/ApJ/713/615
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Classical Cepheids are primary distance indicators playing a fundamental role in the calibration of the extragalactic distance scale. The possible dependence of their characteristic period-luminosity (PL) relation on chemical composition is still debated in the literature, and the behavior of these pulsators at very low metallicity regimes is almost unexplored. In order to derive constraints on the application of the PL relation at low metal abundances, we investigate the properties of the few ultra-low metallicity (Z~0.0004) Cepheids recently discovered in the Blue Compact Dwarf galaxy IZw18. To this purpose, we have computed an updated and extended set of nonlinear convective models for Z=0.0004 and Y=0.24, spanning a wide range of stellar masses, and taking into account the evolutionary constraints for selected luminosity levels. As a result, we are able to predict the topology of the instability strip, the variations of all the relevant quantities along the pulsation cycle, including the morphology of the light curves, the theoretical period-luminosity-color, period-Wesenheit, and PL relations at such a low metallicity.
