- ID:
- ivo://CDS.VizieR/J/A+A/349/448
- Title:
- Open star clusters. I. NGC 581 (M 103)
- Short Name:
- J/A+A/349/448
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD photometry and a proper motion study of the young open star cluster, NGC 581 (M 103). Fitting isochrones to the colour magnitude diagram, we found an age of 16+/-4Myr and a distance of roughly 3kpc for this cluster. The proper motion study identifies 77 stars of V=14.5mag or brighter to be cluster members. We combine membership determination by proper motions and statistical field star subtraction to derive the IMF of the cluster and find a quite steep slope of {Gamma}=-1.80.
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- ID:
- ivo://CDS.VizieR/J/ApJ/809/59
- Title:
- Ophiuchus stellar stream with PS1 data
- Short Name:
- J/ApJ/809/59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Ophiuchus stream is a recently discovered stellar tidal stream in the Milky Way. We present high-quality spectroscopic data for 14 stream member stars obtained using the Keck and MMT telescopes. We confirm the stream as a fast moving (v_los_~290km/s), kinematically cold group ({sigma}_{nu}_los__<~1km/s) of {alpha}-enhanced and metal-poor stars ([{alpha}/Fe]~0.4dex, [Fe/H]~-2.0dex). Using a probabilistic technique, we model the stream simultaneously in line-of-sight velocity, color-magnitude, coordinate, and proper motion space, and so determine its distribution in 6D phase-space. We find that the stream extends in distance from 7.5 to 9kpc from the Sun; it is 50 times longer than wide, merely appearing highly foreshortened in projection. The analysis of the stellar population contained in the stream suggests that it is ~12Gyr old, and that its initial stellar mass was ~2x10^4^M_{sun}_ (or at least >~7x10^3^M_{sun}_). Assuming a fiducial Milky Way potential, we fit an orbit to the stream that matches the observed phase-space distribution, except for some tension in the proper motions: the stream has an orbital period of ~350Myr, and is on a fairly eccentric orbit (e~0.66) with a pericenter of ~3.5kpc and an apocenter of ~17kpc. The phase-space structure and stellar population of the stream show that its progenitor must have been a globular cluster that was disrupted only ~240Myr ago. We do not detect any significant overdensity of stars along the stream that would indicate the presence of a progenitor, and conclude that the stream is all that is left of the progenitor.
- ID:
- ivo://CDS.VizieR/J/ApJ/876/115
- Title:
- Optical follow-up of ASAS-SN M dwarf flares
- Short Name:
- J/ApJ/876/115
- Date:
- 18 Jan 2022 15:06:46
- Publisher:
- CDS
- Description:
- The All-sky Automated Survey for Supernovae (ASAS-SN) is the only project in existence to scan the entire sky in optical light approximately every day, reaching a depth of g~18mag. Over the course of its first 4yr of transient alerts (2013-2016), ASAS-SN observed 53 events classified as likely M dwarf flares. We present follow-up photometry and spectroscopy of all 53 candidates, confirming flare events on 47 M dwarfs, one K dwarf, and one L dwarf. The remaining four objects include a previously identified T Tauri star, a young star with outbursts, and two objects too faint to confirm. A detailed examination of the 49 flare star light curves revealed an additional six flares on five stars, resulting in a total of 55 flares on 49 objects ranging in V-band contrast from {Delta}V=-1 to -10.2mag. Using an empirical flare model to estimate the unobserved portions of the flare light curve, we obtain lower limits on the V-band energy emitted during each flare, spanning log(E_V_/erg)=32-35, which are among the most energetic flares detected on M dwarfs. The ASAS-SN M dwarf flare stars show a higher fraction of H{alpha} emission, as well as stronger H{alpha} emission, compared to M dwarfs selected without reference to activity, consistent with belonging to a population of more magnetically active stars. We also examined the distribution of tangential velocities, finding that the ASAS-SN flaring M dwarfs are likely to be members of the thin disk and are neither particularly young nor old.
- ID:
- ivo://CDS.VizieR/B/ocl
- Title:
- Optically visible open clusters and Candidates
- Short Name:
- B/ocl
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have compiled a new catalogue of open clusters in the Galaxy which updates the previous catalogues of Lynga (1987, Cat. VII/92) and of Mermilliod (1995, in Information and On-Line Data in Astronomy, ed. D. Egret & M. A. Albrecht (Dordrecht: Kluwer), 127) (included in the WEBDA database, http://obswww.unige.ch/webda). New objects and new data, in particular, data on kinematics (proper motions) that were not present in the old catalogues, have been included. Virtually all the clusters (2167) presently known were included, which represents an increment of about 986 objects relative to the Lynga (1987, VII/92) catalogue. The catalogue is presented in a single table containing all the important data, which makes it easy to use. In total, 99.7% of the objects have estimates of their apparent diameters, and 74.5% have distance, E(B-V) and age determinations. Concerning the data on kinematics, 54.7% have their mean proper motions listed, 25% their mean radial velocities, and 24.2% have both information simultaneously.
- ID:
- ivo://CDS.VizieR/J/ApJ/872/42
- Title:
- Opt. spectroscopy of redback ms pulsar binaries
- Short Name:
- J/ApJ/872/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first optical spectroscopy of five confirmed (or strong candidate) redback millisecond pulsar binaries, obtaining complete radial velocity curves for each companion star. The properties of these millisecond pulsar binaries with low-mass, hydrogen-rich companions are discussed in the context of the 14 confirmed and 10 candidate field redbacks. We find that the neutron stars in redbacks have a median mass of 1.78+/-0.09M_{sun}_ with a dispersion of {sigma}=0.21+/-0.09. Neutron stars with masses in excess of 2M_{sun}_ are consistent with, but not firmly demanded by, current observations. Redback companions have median masses of 0.36+/-0.04M_{sun}_ with a scatter of {sigma}=0.15+/-0.04M_{sun}_, and a tail possibly extending up to 0.7-0.9M_{sun}_. Candidate redbacks tend to have higher companion masses than confirmed redbacks, suggesting a possible selection bias against the detection of radio pulsations in these more massive candidate systems. The distribution of companion masses between redbacks and the less massive black widows continues to be strongly bimodal, which is an important constraint on evolutionary models for these systems. Among redbacks, the median efficiency of converting the pulsar spin-down energy to {gamma}-ray luminosity is ~10%.
- ID:
- ivo://CDS.VizieR/J/ApJ/725/L186
- Title:
- Orbital eccentricities of 31535 G-dwarfs
- Short Name:
- J/ApJ/725/L186
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We test four competing models that aim to explain the nature of stars in spiral galaxies that are well away (>1kpc) from the midplane, the so-called thick disk: the stars may have gotten there through orbital migration, through satellite mergers and accretion, or through heating of pre-existing thin disk stars. The eccentricity distribution of thick disk stars has recently been proposed as a diagnostic to differentiate between these mechanisms. Drawing on SDSS-DR7, we have assembled a sample of 31535 G-dwarfs with six-dimensional phase-space information and metallicities and have derived the orbital eccentricities for them.
- ID:
- ivo://CDS.VizieR/J/ApJS/214/17
- Title:
- Orbital monitoring of AstraLux binaries
- Short Name:
- J/ApJS/214/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Orbital monitoring of M-type binaries is essential for constraining their fundamental properties. This is particularly useful in young systems, where the extended pre-main-sequence evolution can allow for precise isochronal dating. Here, we present the continued astrometric monitoring of the more than 200 binaries of the AstraLux Large Multiplicity Survey, building both on our previous work, archival data, and new astrometric data spanning the range of 2010-2012. The sample is very young overall --all included stars have known X-ray emission, and a significant fraction (18%) of them have recently also been identified as members of young moving groups in the solar neighborhood. We identify ~30 targets that both have indications of being young and for which an orbit either has been closed or appears possible to close in a reasonable time frame (a few years to a few decades). One of these cases, GJ 4326, is, however, identified as probably being substantially older than has been implied from its apparent moving group membership, based on astrometric and isochronal arguments. With further astrometric monitoring, these targets will provide a set of empirical isochrones, against which theoretical isochrones can be calibrated, and which can be used to evaluate the precise ages of nearby young moving groups.
- ID:
- ivo://CDS.VizieR/J/MNRAS/474/2479
- Title:
- Orbital parameters of globular clusters
- Short Name:
- J/MNRAS/474/2479
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the effects of collisional dynamics on the formation and detectability of cold tidal streams. A semi-analytical model for the evolution of the stellar mass function was implemented and coupled to a fast stellar stream simulation code, as well as the synthetic cluster evolution code EMACSS for the mass evolution as a function of a globular cluster orbit. We find that the increase in the average mass of the escaping stars for clusters close to dissolution has a major effect on the observable stream surface density. As an example, we show that Palomar 5 would have undetectable streams (in an SDSS-like survey) if it was currently three times more massive, despite the fact that a more massive cluster loses stars at a higher rate. This bias due to the preferential escape of low-mass stars is an alternative explanation for the absence of tails near massive clusters, than a dark matter halo associated with the cluster. We explore the orbits of a large sample of Milky Way globular clusters and derive their initial masses and remaining mass fraction. Using properties of known tidal tails, we explore regions of parameter space that favour the detectability of a stream. A list of high-probability candidates is discussed.
- ID:
- ivo://CDS.VizieR/J/AJ/156/194
- Title:
- Orbits of double-lined pairs in multiple stars
- Short Name:
- J/AJ/156/194
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectroscopic orbits are computed for inner pairs in nine hierarchical multiple systems (HIP 19639, 60845, 75663, 76816, 78163, 78416, 80448, 84789, and HD 105080) and for one simple binary HIP 61840. All subsystems are double-lined, and their periods range from 2.27 to 30.4 days. Five spectroscopic binaries are twins with equal masses. Each hierarchical system is discussed individually, providing estimates of outer periods, masses, orbital inclination, and axial rotation. For systems with three resolved visual components (HIP 60845 and 80448), the outer and inner visual orbits are determined, complementing the description of their architecture. The radial velocities of HIP 75663A, 76816B, and 78163B are found to be variable with long periods, implying that these hierarchies are 2 + 2 quadruples. The period-eccentricity relation for spectroscopic subsystems is discussed.
- ID:
- ivo://CDS.VizieR/J/MNRAS/399/2146
- Title:
- Orbits of open clusters in the Galaxy
- Short Name:
- J/MNRAS/399/2146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present and analyse the kinematics and orbits for a sample of 488 open clusters (OCs) in the Galaxy. The velocity ellipsoid for our present sample is derived as ({sigma}(U),{sigma}(V),{sigma}(W)) = (28.7, 15.8, 11.0)km/s which represents a young thin-disc population. We also confirm that the velocity dispersions increase with the age of a cluster subsample. The orbits of OCs are calculated with three Galactic gravitational potential models. The errors of orbital parameters are also calculated considering the intrinsic variation of the orbital parameters and the effects of observational uncertainties. The observational uncertainties dominate the errors of derived orbital parameters. The vertical motions of clusters calculated using different Galactic disc models are rather different. The observed radial metallicity gradient of clusters is derived with a slope of b=-0.070+/-0.011dex/kpc. The radial metallicity gradient of clusters based on their apogalactic distances is also derived with a slope of b=-0.082+/-0.014dex/kpc. The distribution of derived orbital eccentricities for OCs is very similar to that derived for the field population of dwarfs and giants in the thin disc.
