scholarly journals A survey for low-mass stellar and substellar members of the Hyades open cluster

2018 ◽  
Vol 611 ◽  
pp. A34 ◽  
Author(s):  
Stanislav Melnikov ◽  
Jochen Eislöffel
Keyword(s):  
Proper Motion ◽  
Open Cluster ◽  
Dynamical Evolution ◽  
Mass Function ◽  
Open Clusters ◽  
Cluster Member ◽  
Low Mass Stars ◽  
Hyades Cluster ◽  
Low Mass ◽  
Selection Of

Context. Unlike young open clusters (with ages < 250 Myr), the Hyades cluster (age ~ 600 Myr) has a clear deficit of very low-mass stars (VLM) and brown dwarfs (BD). Since this open cluster has a low stellar density and covers several tens of square degrees on the sky, extended surveys are required to improve the statistics of the VLM/BD objects in the cluster. Aim. We search for new VLM stars and BD candidates in the Hyades cluster to improve the present-day cluster mass function down to substellar masses. Methods. An imaging survey of the Hyades with a completeness limit of 21.m5 in the R band and 20.m5 in the I band was carried out with the 2k × 2k CCD Schmidt camera at the 2 m Alfred Jensch Telescope in Tautenburg. We performed a photometric selection of the cluster member candidates by combining results of our survey with 2MASS JHKs photometry Results. We present a photometric and proper motion survey covering 23.4 deg2 in the Hyades cluster core region. Using optical/IR colour-magnitude diagrams, we identify 66 photometric cluster member candidates in the magnitude range 14.m7 < I < 20.m5. The proper motion measurements are based on several all-sky surveys with an epoch difference of 60–70 yr for the bright objects. The proper motions allowed us to discriminate the cluster members from field objects and resulted in 14 proper motion members of the Hyades. We rediscover Hy 6 as a proper motion member and classify it as a substellar object candidate (BD) based on the comparison of the observed colour-magnitude diagram with theoretical model isochrones. Conclusions. With our results, the mass function of the Hyades continues to be shallow below ~0.15 M⊙ indicating that the Hyades have probably lost their lowest mass members by means of dynamical evolution. We conclude that the Hyades core represents the “VLM/BD desert” and that most of the substeller objects may have already left the volume of the cluster.

scholarly journals Exploring the substellar population in the Hyades open cluster

2018 ◽  
Vol 620 ◽  
pp. A130 ◽  
Author(s):  
A. Pérez-Garrido ◽  
N. Lodieu ◽  
R. Rebolo ◽  
P. Chinchilla
Keyword(s):  
Main Sequence ◽  
Open Cluster ◽  
Spectroscopic Properties ◽  
Mass Function ◽  
Likelihood Method ◽  
Low Mass Stars ◽  
Open Star ◽  
Hyades Cluster ◽  
Low Mass ◽  
Open Star Cluster

Aims. Our aim is to identify substellar members of the nearby Hyades open star cluster to determine the photometric and spectroscopic properties of brown dwarfs at moderately old ages and extend our knowledge of the substellar mass function of the cluster. Methods. We cross-matched the 2MASS and WISE public catalogues and measured proper motions to identify low-mass stars and brown dwarf member candidates in an area of a radius of ten degrees around the central region of the Hyades cluster. We employed astrometric and photometric criteria, Gaia data, and a maximum likelihood method developed by our group to estimate distances. We selected 36 objects that are candidate Hyades members, 21 of which have not been reported previously. Results. We have identified 21 new Hyades member candidates that are placed at the lower end of the main sequence. The photometry of 9 candidates places them in the substellar regime, and 2 are at the L/T transition. We also recovered a number of L dwarfs from earlier surveys. Finally, we calculated the mass function for the low-mass population of the cluster and found that the Hyades cluster might have lost 60%–80% of its substellar members.

scholarly journals Globular Clusters: Low Mass Stars, Still No Brown Dwarfs!

2003 ◽  
Vol 211 ◽  
pp. 215-222
Author(s):  
Guido De Marchi
Keyword(s):  
Globular Clusters ◽  
Functional Form ◽  
Dynamical Evolution ◽  
Mass Function ◽  
Brown Dwarf ◽  
Low Mass Stars ◽  
Homogeneous Sample ◽  
Original Mass ◽  
Low Mass ◽  
The Imf

In spite of all the attempts to find them, no one has yet detected any brown dwarf in a globular cluster. Although powerful instruments such as the VLT and Advanced Camera could further push the frontiers of this search, globular clusters will probably hold tight to their secrets for a while longer. Nonetheless, the search for very low mass stars in globular clusters has taught us a lot about their original mass distribution (IMF) and its evolution in time. I shall review the results of an investigation carried out over what is presently the largest, most homogeneous sample, and discuss the reasons suggesting that: 1. dynamical evolution (internal and external) has reshaped the cluster mass function over time, but the imprint of the IMF is still visible; 2. the IMF appears to vary very little from cluster to cluster; 3. the most likely functional form of the IMF is that of a power law that rises to a peak at ˜ 0.3 M⊙ and tapers off at smaller masses.

Complex study of the open cluster NGC 2281

2017 ◽  
Vol 12 (S330) ◽  
pp. 273-274
Author(s):  
Jaroslav Velčovský ◽  
Jan Janík
Keyword(s):  
Radial Velocity ◽  
Proper Motion ◽  
Open Cluster ◽  
Open Clusters ◽  
Ccd Photometry ◽  
Complex Study ◽  
Colour Excess ◽  
Dynamical Parameters ◽  
Astrometric Data ◽  
Selection Of

AbstractWe present the complex study of the open cluster NGC 2281 where both traditional and newly developed methods for study of open clusters have been used. Morphological and dynamical parameters of the cluster were obtained from the accepted astrometric data. The new method “Superposition of Gaussian surfaces” along with proper motion of stars was used to determine membership probabilities which were helpful in selection of stars for further analysis. Metallicity and radial velocity of the cluster were obtained from spectroscopic measurements. Age, colour excess, and distance of the cluster were determined using absolute CCD photometry combined with previous results. The results were compared with those of previous studies.

scholarly journals Brown dwarfs and very low mass stars in the Praesepe open cluster: a dynamically unevolved mass function?

2010 ◽  
Vol 510 ◽  
pp. A27 ◽  
Author(s):  
S. Boudreault ◽  
C. A. L. Bailer-Jones ◽  
B. Goldman ◽  
T. Henning ◽  
J. A. Caballero
Keyword(s):  
Open Cluster ◽  
Brown Dwarfs ◽  
Mass Function ◽  
Low Mass Stars ◽  
Low Mass ◽  
Cluster A

scholarly journals Brown dwarfs and very low mass stars in the Hyades cluster: a dynamically evolved mass function

2008 ◽  
Vol 481 (3) ◽  
pp. 661-672 ◽  
Author(s):  
J. Bouvier ◽  
T. Kendall ◽  
G. Meeus ◽  
L. Testi ◽  
E. Moraux ◽  
...  
Keyword(s):  
Brown Dwarfs ◽  
Mass Function ◽  
Low Mass Stars ◽  
Hyades Cluster ◽  
Low Mass ◽  
Cluster A

scholarly journals Low Mass Stars and White Dwarfs in NGC 6397

1995 ◽  
Vol 164 ◽  
pp. 408-408
Author(s):  
Guido De Marchi ◽  
Francesco Paresce ◽  
Martino Romaniello
Keyword(s):  
White Dwarf ◽  
Luminosity Function ◽  
Main Sequence ◽  
Dynamical Evolution ◽  
Mass Function ◽  
Initial Mass Function ◽  
Low Mass Stars ◽  
Hydrogen Burning ◽  
Low Mass ◽  
Counting Statistics

Deep WFPC2 images in wide bands centered at 606 and 802 nm were taken with the HST 5.6 arcminutes from the center of the galactic globular cluster NGC 6397. The images were used to accurately position ~ 2120 stars detected in the field on a color magnitude diagram down to a limiting magnitude m814 ≃ mI ≃ 26 determined reliably and solely by counting statistics. A white dwarf sequence and a rich, narrow cluster main sequence are detected for the first time, the latter stretching from m814 = 18.5 to m814 = 24.0 where it becomes indistinguishable from the field population. Two changes of slope of the main sequence at m814 ≃ 20 and m814 ≃ 22.5 are evident. The corresponding luminosity function increases slowly from M814 ≃ 6.5 to 8.5 as expected from ground based observations but then drops sharply from there down to the measurement limit. The corresponding mass function obtained by using the only presently available mass-luminosity function for the cluster's metallicity rises to a plateau between ~ 0.25 and~ 0.15 M⊙, but drops towards the expected mass limit of the normal hydrogen burning main sequence at about 0.1 M⊙. This result is in clear contrast to that obtained from the ground and implies either a substantial modification of the cluster's initial mass function due to dynamical evolution in its lifetime, or that very low mass stars are not produced in any dynamically significant amount by clusters of this type. The white dwarf sequence is in reasonable agreement with a cooling sequence of models of mass 0.5 M⊙ at the canonical distance of NGC 6397 with a scatter that is most likely due to photometric errors, but may also reflect real differences in mass or chemical composition.

scholarly journals Rotational Evolution of Intermediate and Low Mass Main Sequence Stars

2004 ◽  
Vol 215 ◽  
pp. 127-135
Author(s):  
John R. Stauffer
Keyword(s):  
Main Sequence ◽  
Massive Stars ◽  
Rotational Velocity ◽  
Open Cluster ◽  
Open Clusters ◽  
Solar Mass ◽  
Low Mass Stars ◽  
Cluster Data ◽  
Rotational Evolution ◽  
Low Mass

Bob Kraft (1967) showed that there is a break in the mean rotational velocity of stars at about spectral type F5, with more massive stars generally being rapid rotators and less massive stars generally being slow rotators. He also showed that in the late F spectral range at least, there is an evolution with time on the main sequence, with younger F stars being more rapidly rotating. Kraft's observational database extended only to about one solar mass due to the sensitivy limitations of photographic plates. Modern observations of low mass stars in open clusters, extending down in mass to nearly the hydrogen burning mass limit in a few clusters, have since been used to show that rotational spindown is the common feature of stars less massive than the sun but that there is a wide spread in rotational velocities when stars arrive on the ZAMS. I will review what is known empirically concerning the rotational velocities of intermediate and low mass field stars, using the open cluster data to place the field star observations in context.

scholarly journals Ages of Galactic and Extragalactic Star Clusters of Various Abundances

1983 ◽  
Vol 6 ◽  
pp. 109-117 ◽  
Author(s):  
R.D. Cannon
Keyword(s):  
Star Clusters ◽  
Magellanic Clouds ◽  
Open Clusters ◽  
Simultaneous Solution ◽  
Low Mass Stars ◽  
Cluster Systems ◽  
Distant Cluster ◽  
Low Mass

In this review I shall concentrate mainly on globular star clusters in our Galaxy since these are the objects for which most work has been done recently, both observationally and theoretically. However, I shall also discuss briefly the oldest open clusters and clusters in the Magellanic Clouds. Little can be said about more distant cluster systems, since the only observations available are of integrated colours or spectra and these seem to be rather unreliable indicators of age. It is perhaps worth pointing out that the title may be slightly misleading; the problem is not so much to determine the ages of clusters of known abundances, as to obtain the best simultaneous solution for both age and composition, since some of the most important abundances (notably helium and oxygen) are virtually unobservable in little-evolved low mass stars.

scholarly journals MOTION VERIFIED RED STARS (MoVeRS): A CATALOG OF PROPER MOTION SELECTED LOW-MASS STARS FROMWISE, SDSS, AND 2MASS

2016 ◽  
Vol 151 (2) ◽  
pp. 41 ◽  
Author(s):  
Christopher A. Theissen ◽  
Andrew A. West ◽  
Saurav Dhital
Keyword(s):  
Proper Motion ◽  
Low Mass Stars ◽  
Low Mass
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