- ID:
- ivo://CDS.VizieR/J/AJ/159/114
- Title:
- Magnetic CVs spectra & other variable objects II.
- Short Name:
- J/AJ/159/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second paper of a series presenting our search for magnetic cataclysmic variables (mCVs) among candidates selected mostly from the Catalina Real-Time Transient Survey. We present the identification spectra, obtained at the SOAR Telescope, as well as magnitudes and Gaia distances for 45 objects. Of these, 39 objects are identified as CVs, from which 8 targets show observational characteristics of mCVs, being 7 polars and 1 intermediate polar. The remaining 31 CVs in our sample are probably non-magnetic systems, in low (22 systems) or high (9 systems) accretion states. Six targets of the sample are not CVs (5 active galactic nuclei and 1 T-Tauri star). Among the 8 objects with mCV spectra, 6 are new classifications. Three polars were observed in low-accretion state, either revealing photospheric features of the secondary star and allowing the estimation of their spectral type, or presenting H{beta} Zeeman components associated to the white dwarf (WD) magnetic field. In addition to the results obtained in the first paper of the series, and depending on the confirmation of these classifications by observational follow-up, our results would increase the sample of known polars by about 9%.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/154/140
- Title:
- MALT90 kinematic distances to molecular clumps
- Short Name:
- J/AJ/154/140
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using molecular-line data from the Millimetre Astronomy Legacy Team 90 GHz Survey (MALT90), we have estimated kinematic distances to 1905 molecular clumps identified in the ATLASGAL 870 {mu}m continuum survey over the longitude range 295{deg}<l<350{deg}. The clump velocities were determined using a flux-weighted average of the velocities obtained from Gaussian fits to the HCO^+^, HNC, and N_2_H^+^ (1-0) transitions. The near/far kinematic distance ambiguity was addressed by searching for the presence or absence of absorption or self-absorption features in 21 cm atomic hydrogen spectra from the Southern Galactic Plane Survey. Our algorithm provides an estimation of the reliability of the ambiguity resolution. The Galactic distribution of the clumps indicates positions where the clumps are bunched together, and these locations probably trace the locations of spiral arms. Several clumps fall at the predicted location of the far side of the Scutum-Centaurus arm. Moreover, a number of clumps with positive radial velocities are unambiguously located on the far side of the Milky Way at galactocentric radii beyond the solar circle. The measurement of these kinematic distances, in combination with continuum or molecular-line data, now enables the determination of fundamental parameters such as mass, size, and luminosity for each clump.
- ID:
- ivo://CDS.VizieR/J/A+A/380/665
- Title:
- Massive dense cores with ^13^CO J=1-0 lines
- Short Name:
- J/A+A/380/665
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper reports ^13^CO J=1-0 line observations toward 107 IRAS or H2O maser sources with the 13.7m telescope of the Purple Mountain Observatory (PMO). Parameters of emission components are obtained and the profile characteristics are identified. Table1 lists the observed results. It contains source name and its coordinates. ^13^CO line parameters and profile characteristics are given out. Distance, IRAS color indices and bolometric luminosity are also presented.
- ID:
- ivo://CDS.VizieR/J/A+A/403/943
- Title:
- Mass-loss rates of galactic AGB stars
- Short Name:
- J/A+A/403/943
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We are using the 2002 data-release from the Japanese space experiment IRTS to investigate the spatial distribution of galactic mass-losing (>2x10^-8_M_{sun}_/yr) AGB stars and the relative contribution of C-rich and O-rich ones to the replenishment of the ISM. Our sample contains 126 C-rich and 563 O-rich sources which are sorted on the basis of the molecular bands observed in the range 1.4-4.0{mu}m, and for which we estimate distances and mass loss rates from near-infrared photometry (K and L'). There is a clear dependence on galactocentric distance, with O-rich sources outnumbering C-rich ones for {tau}_GC_<8kpc, and the reverse for {tau}_GC_>10kpc. The contribution to the replenishment of the ISM by O-rich AGB stars relative to C-rich ones follows the same trend. Although they are rare (~10% in our sample), sources with 10^-6^M_{sun}_/yr<dM/dt<10^-5^M_{sun}_/yr dominate the replenishment of the ISM by contributing to ~50% of the total of the complete sample. We find 2 carbon stars at more than 1kpc from the Galactic Plane, that probably belong to the halo of our Galaxy.
- ID:
- ivo://CDS.VizieR/J/A+A/333/897
- Title:
- Mass segregation in open clusters
- Short Name:
- J/A+A/333/897
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- On the basis of the best available member list and duplicity information, we have studied the radial structure of Praesepe and of the very young open cluster NGC 6231. We have found mass segregation among the cluster members and between binaries and single stars, which is explained by the greater average mass of the multiple systems. However, the degree of mass segregation for stars between 1.5 and 2.3M_{sun}_ is less pronounced in Praesepe than in the Pleiades. Furthermore, mass segregation is already present in the very young open cluster NGC 6231 although this cluster is likely still not dynamically relaxed. We discuss the implications of these results and propose a qualitative scenario for the evolution of mass segregation in open clusters. In Praesepe the mass function of single stars and primaries appears to be significantly different, like in the Pleiades. We observe an absence of ellipticity of the outer part of Praesepe.
- ID:
- ivo://CDS.VizieR/J/AJ/126/2421
- Title:
- 2MASS-Selected sample of ultracool dwarfs
- Short Name:
- J/AJ/126/2421
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the initial results of our effort to create a statistically robust, volume-limited sample of ultracool dwarfs from the Two Micron All Sky Survey Second Incremental Data Release (<II/241>). We are engaged in a multifaceted search for nearby late-type objects, and this is the first installment of our search using purely photometric selection. The goal of this work is a determination of the low-mass star and brown dwarf luminosity function in the infrared. Here we outline the construction of the sample, dubbed 2MU2, and present our first results, including the discovery of 186 M7-L6 dwarfs, 47 of which are likely to be within 20pc of the Sun. These results represent 66% of the ultracool candidates in our sample yet constitute a 127% increase in the number of ultracool dwarfs known within the volume searched (covering 40% of the sky out to 20pc). In addition, we have identified 10 M4-M6.5 objects that are likely to be within 20pc (or within 1{sigma}). Finally, based on these initial data, we present a preliminary luminosity function and discuss several interesting features of the partial sample presented here. Once our sample is complete, we will use our measured luminosity function to constrain the mass function of low-mass stars and brown dwarfs.
- ID:
- ivo://CDS.VizieR/J/AJ/154/124
- Title:
- M dwarfs-long-term photometric variability
- Short Name:
- J/AJ/154/124
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report findings from a long-term photometric variability study of M dwarfs carried out at the SMARTS 0.9 m telescope at the Cerro Tololo Inter-American Observatory. As part of a multi-faceted effort to investigate the range of luminosities of M dwarfs of a given color on the Hertzsprung-Russell Diagram, 76 M dwarfs have been observed for 3-17 years in the Johnson-Kron-Cousins V band. We find that stars elevated above the center of the main sequence distribution tend to have higher levels of variability, likely caused by magnetic activity, than their fainter counterparts below the center. This study provides insight into how the long-term magnetic activity of these stars may be affecting their sizes, luminosities, and thus positions on the H-R Diagram.
- ID:
- ivo://CDS.VizieR/J/MNRAS/463/1844
- Title:
- M dwarfs rotation-activity relation
- Short Name:
- J/MNRAS/463/1844
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the relation between stellar rotation and magnetic activity for a sample of 134 bright, nearby M dwarfs observed in the Kepler Two-Wheel (K2) mission during campaigns C0 to C4. The K2 lightcurves yield photometrically derived rotation periods for 97 stars (79 of which without previous period measurement), as well as various measures for activity related to cool spots and flares. We find a clear difference between fast and slow rotators with a dividing line at a period of ~10d at which the activity level changes abruptly. All photometric diagnostics of activity (spot cycle amplitude, flare peak amplitude and residual variability after subtraction of spot and flare variations) display the same dichotomy, pointing to a quick transition between a high-activity mode for fast rotators and a low-activity mode for slow rotators. This unexplained behavior is reminiscent of a dynamo mode-change seen in numerical simulations that separates a dipolar from a multipolar regime. A substantial number of the fast rotators are visual binaries. A tentative explanation is accelerated disk evolution in binaries leading to higher initial rotation rates on the main-sequence and associated longer spin-down and activity lifetimes. We combine the K2 rotation periods with archival X-ray and UV data. X-ray, FUV and NUV detections are found for 26, 41, and 11 stars from our sample, respectively. Separating the fast from the slow rotators, we determine for the first time the X-ray saturation level separately for early- and for mid-M stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/812/3
- Title:
- MEarth mid-to-late M dwarfs rotation & kinematics
- Short Name:
- J/ApJ/812/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using spectroscopic observations and photometric light curves of 238 nearby M dwarfs from the MEarth exoplanet transit survey, we examine the relationships between magnetic activity (quantified by H{alpha} emission), rotation period, and stellar age. Previous attempts to investigate the relationship between magnetic activity and rotation in these stars were hampered by the limited number of M dwarfs with measured rotation periods (and the fact that v sin i measurements probe only rapid rotation). However, the photometric data from MEarth allows us to probe a wide range of rotation periods for hundreds of M dwarf stars (from shorter than one to longer than 100 days). Over all M spectral types that we probe, we find that the presence of magnetic activity is tied to rotation, including for late-type, fully convective M dwarfs. We also find evidence that the fraction of late-type M dwarfs that are active may be higher at longer rotation periods compared to their early-type counterparts, with several active, late-type, slowly rotating stars present in our sample. Additionally, we find that all M dwarfs with rotation periods shorter than 26 days (early-type; M1-M4) and 86 days (late-type; M5-M8) are magnetically active. This potential mismatch suggests that the physical mechanisms that connect stellar rotation to chromospheric heating may be different in fully convective stars. A kinematic analysis suggests that the magnetically active, rapidly rotating stars are consistent with a kinematically young population, while slow-rotators are less active or inactive and appear to belong to an older, dynamically heated stellar population.
- ID:
- ivo://CDS.VizieR/J/AJ/159/166
- Title:
- Membership & properties of moving groups with Gaia
- Short Name:
- J/AJ/159/166
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the membership probability of young stars belonging to nearby moving groups with Gaia DR2 data. The sample of 1429 stars was identified from "The Catalog of Suspected Nearby Young Moving Group Stars" (CSNYMGS; see Riedel+, J/AJ/153/95). Good-quality parallax and proper motion values were retrieved for 890 stars from the Gaia DR2 database. The analysis for membership probability is performed in the framework of the LACEwING algorithm (Riedel 2016IAUS..314...33R). From the analysis it is confirmed that 279 stars do not belong to any of the known moving groups. We estimated the U, V, W space velocity values for 250 moving group members, which were found to be more accurate than previous values listed in the literature. The velocity ellipses of all the moving groups are well constrained within the "good box," a widely used criterion to identify moving group members. The age of moving group members are uniformly estimated from the analysis of the Gaia color-magnitude diagram with MIST isochrones. We found a spread in the age distribution of stars belonging to some moving groups, which needs to be understood from further studies.
