scholarly journals Spectroscopic classification and Gaia DR2 parallaxes of new nearby white dwarfs among selected blue proper motion stars

2018 ◽  
Vol 619 ◽  
pp. A31 ◽  
Author(s):  
R.-D. Scholz ◽  
H. Meusinger ◽  
A. Schwope ◽  
H. Jahreiß ◽  
I. Pelisoli
Keyword(s):  
Proper Motion ◽  
White Dwarfs ◽  
Near Infrared ◽  
Galactic Halo ◽  
Link Type ◽  
Halo Stars ◽  
Sky Survey ◽  
Low Mass ◽  
Gaia Dr2 ◽  
Calar Alto

Aims. With our low-resolution spectroscopic observing programme for selected blue proper motion stars, we tried to find new white dwarfs (WDs) in the solar neighbourhood. Methods. We used the Lépine & Shara Proper Motion (LSPM) catalogue with a lower proper motion limit of 150 mas yr−1 and the Second US Naval Observatory CCD Astrograph Catalog (UCAC2) for proper motions down to about 90 mas yr−1. The LSPM and UCAC2 photometry was combined with Two Micron All Sky Survey (2MASS) near-infrared (NIR) photometry. Targets selected according to their blue optical-to-NIR and NIR colours were observed mainly at Calar Alto. The spectra were classified by comparison with a large number of already known comparison objects, including WDs, simultaneously observed within our programme. Gaia DR2 parallaxes and colours were used to confirm or reject spectroscopic WD candidates and to derive improved effective temperatures. Results. We found ten new WDs at distances between 24.4 pc and 79.8 pc, including six hot DA WDs: GD 221 (DA2.0), HD 166435 B (DA2.2), GD 277 (DA2.2), 2MASS J19293865+1117523 (DA2.4), 2MASS J05280449+4105253 (DA3.6), and 2MASS J05005185-0930549 (DA4.2). The latter is rather bright (G ≍ 12.6) and with its Gaia DR2 parallax of ≍14 mas it appears overluminous by about 3 mag compared to the WD sequence in the Gaia DR2 colour-magnitude diagram. It may be the closest extremely low mass (ELM) WD to the Sun. We further classified 2MASS J07035743+2534184 as DB4.1. With its distance of 25.6 pc it is the second nearest known representative of its class. With GD 28 (DA6.1), LP 740-47 (DA7.5), and LSPM J1919+4527 (DC10.3) three additional cool WDs were found. Gaia DR2 parallaxes show that four of our candidates, but also two previously supposed WDs (WD 1004+665 and LSPM J1445+2527) are in fact distant Galactic halo stars with high tangential velocities. Among our rejected WD candidates, we identified a bright (G = 13.4 mag) G-type carbon dwarf, LSPM J0937+2803, at a distance of 272 pc.

scholarly journals Astrometric detection and characterization of brown dwarfs

2007 ◽  
Vol 3 (S248) ◽  
pp. 30-35
Author(s):  
R.-D. Scholz ◽  
M. J. McCaughrean ◽  
S. Röser ◽  
E. Schilbach
Keyword(s):  
Proper Motion ◽  
Near Infrared ◽  
Critical Mass ◽  
Brown Dwarfs ◽  
Solar Neighborhood ◽  
Sky Survey ◽  
Nearby Stars ◽  
Rare Class ◽  
Low Mass

AbstractAs a result of failed star formation, brown dwarfs (BDs) do not reach the critical mass to ignite the fusion of hydrogen in their cores. Different from their low-mass stellar brothers, the red dwarfs, BDs cool down with their lifetime to very faint magnitudes. Therefore, it was only about 10 to 20 years ago that such ultracool objects began to be detected. Accurate astrometry can be used to detect them indirectly as companions to stars by the signature of the so-called astrometric wobble. Resolved faint BD companions of nearby stars can be identified by their common proper motion (CPM). A direct astrometric detection of the hidden isolated BDs in the Solar neighborhood is possible with deep high proper motion (HPM) surveys. This technique led to the discovery of the first free-floating BD, Kelu 1, and of the nearest BD, ε Indi B. Both were meanwhile found to be binary BDs. The astrometric orbital monitoring of ε Indi Ba+Bb, for which we know an accurate distance from the Hipparcos measurement of its primary, ε Indi A, will allow the determination of individual masses of two low-mass BDs. Hundreds of BDs have been identified for the last decade. Deep optical sky survey (SDSS) and near-infrared sky surveys (DENIS, 2MASS), played a major role in the search mainly based on colours, since BDs emit most of their light at longer wavelengths. However, alternative deep optical HPM surveys based on archival photographic data are not only sensitive enough to detect some of the nearest representatives, they do also uncover many of the rare class of ultracool halo objects crossing the Solar neighborhood at large velocities. SSSPM 1444, with the extremely large proper motion of 3.5 arcsec/yr, is one of the nearest among these subdwarfs with masses at the substellar boundary. We present preliminary parallax results for this and two other ultracool subdwarfs (USDs) from the Calar Alto Omega 2000 parallax program.

scholarly journals A low-mass triple system with a wide L/T transition brown dwarf component: NLTT 51469AB/SDSS 2131−0119

2019 ◽  
Vol 487 (1) ◽  
pp. 1149-1159 ◽  
Author(s):  
B Gauza ◽  
V J S Béjar ◽  
A Pérez-Garrido ◽  
N Lodieu ◽  
R Rebolo ◽  
...  
Keyword(s):  
Spectral Type ◽  
Proper Motion ◽  
Near Infrared ◽  
Close Binary ◽  
Mass Star ◽  
X Rays ◽  
Brown Dwarf ◽  
Uv Excess ◽  
Low Mass ◽  
Gaia Dr2

Abstract We demonstrate that the previously identified L/T transition brown dwarf SDSS J213154.43−011939.3 (SDSS 2131−0119) is a widely separated (82${^{\prime\prime}_{.}}$3, ∼3830 au) common proper motion companion to the low-mass star NLTT 51469, which we reveal to be a close binary itself, separated by 0${^{\prime\prime}_{.}}$64 ± 0${^{\prime\prime}_{.}}$01 (∼30 au). We find the proper motion of SDSS 2131−0119 of μαcos δ = −100 ± 20 mas yr−1 and μδ = −230 ± 20 mas yr−1 consistent with the proper motion of the primary provided by Gaia DR2: μαcos δ = −95.49 ± 0.96 mas yr−1 and μδ = −239.38 ± 0.96 mas yr−1. Based on optical and near-infrared spectroscopy, we classify the primary NLTT 51469A as an M3 ± 1 dwarf, estimate photometrically the spectral type of its close companion NLTT 51469B at ∼M6, and confirm the spectral type of the brown dwarf to be L9 ± 1. Using radial velocity, proper motion, and parallax, we derived the UVW Galactic space velocities of NLTT 51469A, showing that the system does not belong to any known young stellar moving group. The high V, W velocities, lack of a 670.8 nm Li i absorption line, and absence of H α emission, detected X-rays, or UV excess, indicate that the system is likely a member of the thin disc population and is older than 1 Gyr. For the parallactic distance of 46.6 ± 1.6 pc from Gaia DR2, we determined luminosities of $-1.50^{+0.02}_{-0.04}$ and −4.4 ± 0.1 dex of the M3 and L9, respectively. Considering the spectrophotometric estimation, which yields a slightly lower distance of $34^{+10}_{-13}$ pc, the obtained luminosities are $-1.78^{+0.02}_{-0.04}$ and $-4.7^{+0.3}_{-0.5}$ dex. We also estimated their effective temperatures and masses, and obtained 3410$^{+140}_{-210}$ K and 0.42 ± 0.02 M⊙ for the primary, and 1400–1650 K and 0.05–0.07 M⊙ for the wide companion. For the ∼M6 component, we estimated Teff = 2850 ± 200 K and m = 0.10$^{+0.06}_{-0.01}$ M⊙.

scholarly journals White Dwarf Stars

2017 ◽  
Vol 45 ◽  
pp. 1760023
Author(s):  
S. O. Kepler ◽  
Alejandra Daniela Romero ◽  
Ingrid Pelisoli ◽  
Gustavo Ourique
Keyword(s):  
White Dwarf ◽  
Final Stage ◽  
White Dwarfs ◽  
Sloan Digital Sky Survey ◽  
Dwarf Stars ◽  
Multiple Systems ◽  
White Dwarf Stars ◽  
Sky Survey ◽  
Data Release ◽  
Low Mass

White dwarf stars are the final stage of most stars, born single or in multiple systems. We discuss the identification, magnetic fields, and mass distribution for white dwarfs detected from spectra obtained by the Sloan Digital Sky Survey up to Data Release 13 in 2016, which lead to the increase in the number of spectroscopically identified white dwarf stars from 5[Formula: see text]000 to 39[Formula: see text]000. This number includes only white dwarf stars with [Formula: see text], i.e., excluding the Extremely Low Mass white dwarfs, which are necessarily the byproduct of stellar interaction.

The completeness of Gaia-selected samples of white dwarfs

2019 ◽  
Vol 15 (S357) ◽  
pp. 170-174
Author(s):  
Terry D. Oswalt ◽  
Jay B. Holberg ◽  
Edward M. Sion
Keyword(s):  
White Dwarf ◽  
Proper Motion ◽  
White Dwarfs ◽  
Color Index ◽  
Apparent Magnitude ◽  
Order Of Magnitude ◽  
Gaia Dr2 ◽  
Photometric Color

AbstractThe Gaia DR2 has dramatically increased the ability to detect faint nearby white dwarfs. The census of the local white dwarf population has recently been extended from 25 pc to 50 pc, effectively increasing the sample by roughly an order of magnitude. Here we examine the completeness of this new sample as a function of variables such as apparent magnitude, distance, proper motion, photometric color index, unresolved components, etc.

A Search for Brown Dwarfs in the Alpha Persei Cluster

2003 ◽  
Vol 211 ◽  
pp. 179-180
Author(s):  
Nicolas Lodieu ◽  
Mark McCaughrean ◽  
Jérôme Bouvier ◽  
David Barrado y Navascués ◽  
John R. Stauffer
Keyword(s):  
Near Infrared ◽  
Open Cluster ◽  
Brown Dwarfs ◽  
Wide Field ◽  
Brown Dwarf ◽  
Young Open Cluster ◽  
Low Mass ◽  
Alpha Persei ◽  
Calar Alto ◽  
Infrared Survey

We present preliminary results from a deep near-infrared survey of a ~ 1 square degree area in the young open cluster Alpha Persei using the wide-field Omega-Prime camera on the Calar Alto 3.5m telescope, yielding a list of new low-mass cluster members, including brown dwarf candidates.

scholarly journals Search for Stellar Streams in The Galactic Halo From Gaia DR2, GALAH DR2, RAVE DR5 and LAMOST DR4 Data

2020 ◽  
Vol 240 ◽  
pp. 07012
Author(s):  
Ni Made Kartika Wijayanti ◽  
Mochamad Ikbal Arifyanto ◽  
Nur Annisa
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Wavelet Transformation ◽  
High Probability ◽  
Galactic Halo ◽  
Tidal Force ◽  
3D Kinematics ◽  
Halo Stars ◽  
Stellar Streams ◽  
Gaia Dr2

Stellar streams are stars which are trapped in the same potensial caused by dynamical resonance or tidal force. We aim to analyze kinematic sub- structures (streams) in the Galactic halo by V vs √ U2+ 2V 2 planes of Arifyanto & Fuchs. We crossmatched data from Gaia DR2, GALAH DR2, RAVE DR5 and LAMOST DR4 based on positions. We have 3D kinematics and metallicity data of halo stars selected from kinematics criteria from ratio of probability of thick disk (TD) over halo (H) less than 0.01. Substructures are detected by using wavelet transformation and corrected using 15 Monte Carlo simulations. We obtained four kinematic structures on V vs √U2 + 2V 2 plane which two of them are associated to BB17-1 and BB17-2 streams. All the streams had a high probability from the extragalactic origin.

scholarly journals Discovery of a Tight Brown Dwarf Companion to the Low Mass Star LHS 2397a

2003 ◽  
Vol 211 ◽  
pp. 261-264 ◽  
Author(s):  
Melanie Freed ◽  
Laird M. Close ◽  
Nick Siegler
Keyword(s):  
Adaptive Optics ◽  
Spectral Type ◽  
Proper Motion ◽  
Near Infrared ◽  
Mass Star ◽  
Infrared Photometry ◽  
Brown Dwarf ◽  
Dynamical Mass ◽  
Low Mass ◽  
Adaptive Optics System

Using the adaptive optics system, Hōkūpa'a, at Gemini-North, we have directly imaged a companion around the UKIRT faint standard M8 star, LHS 2397a (FS 129) at a separation of 2.96 AU. Near-Infrared photometry obtained on the companion has shown it to be an L7.5 brown dwarf and confirmed the spectral type of the primary to be an M8. We also derive a substellar mass of the companion of 0.068M⊙, although masses in the range (0.061 – 0.069) are possible, and the primary mass as 0.090M⊙ (0.089 – 0.094). Reanalysis of archival imaging from HST has confirmed the secondary as a common proper motion object. This binary represents the first clear example of a brown dwarf companion within 4 AU of a low mass star, and should be the first L7.5 to have a dynamical mass. As part of a larger survey of M8-M9 stars, this object may indicate that there is no “brown dwarf desert” around low mass primaries.

scholarly journals A RADIO SEARCH FOR PULSAR COMPANIONS TO SLOAN DIGITAL SKY SURVEY LOW-MASS WHITE DWARFS

2009 ◽  
Vol 697 (1) ◽  
pp. 283-287 ◽  
Author(s):  
Marcel A. Agüeros ◽  
Fernando Camilo ◽  
Nicole M. Silvestri ◽  
S. J. Kleinman ◽  
Scott F. Anderson ◽  
...  
Keyword(s):  
White Dwarfs ◽  
Sloan Digital Sky Survey ◽  
Sky Survey ◽  
Low Mass

scholarly journals 2MASS J10274572+0629104: the very short period young M6 dwarf binary system identified in K2 data

2019 ◽  
Vol 486 (3) ◽  
pp. 4144-4148
Author(s):  
R R Paudel ◽  
J E Gizis ◽  
A J Burgasser ◽  
C Hsu
Keyword(s):  
Infrared Spectroscopy ◽  
Binary System ◽  
Light Curve ◽  
Near Infrared ◽  
Rotation Periods ◽  
Beat Pattern ◽  
Short Period ◽  
Low Mass ◽  
Periodic Signals ◽  
Gaia Dr2

ABSTRACT We report the identification of a very low mass new binary system 2MASS J10274572+0629104, based on Kepler K2 photometry and Gaia DR2 astrometry. It is located at a distance of 90.0 ± 2.9 pc. The K2 light curve is consistent with a beat pattern of two periodic signals, and using Lomb–Scargle periodogram, we find two rotation periods of 0.2114 ± 0.0002 and 0.2199 ± 0.0003 d. We conclude that these rotation periods arise from two stars with similar spectral types of M6, and have nearly equal luminosity. It is the first ultracool binary system to be identified based on beat patterns in the light curve. Near-infrared spectroscopy yields RV = −9.8 ± 0.6 km s−1, v sin i = 21.5 ± 1.1 km s−1, Teff = 3110 ± 40 K, and log g = 5.2 ± 0.2. The motions are consistent with a young age, as are the rotation periods, but the source does not appear to be part of any known moving group. Furthermore, we detected three strong white light flares in the K2 light curve, with estimated total (UV/optical/IR) energies of 2.6 × 1033, 5.0 × 1033, and 3.5 × 1033 erg, respectively.

scholarly journals The disintegrating old open cluster Czernik 3

2020 ◽  
Vol 498 (2) ◽  
pp. 2309-2322
Author(s):  
Saurabh Sharma ◽  
Arpan Ghosh ◽  
D K Ojha ◽  
R Pandey ◽  
T Sinha ◽  
...  
Keyword(s):  
Proper Motion ◽  
Near Infrared ◽  
Open Cluster ◽  
Mass Range ◽  
Mass Function ◽  
Optical Telescope ◽  
Motion Data ◽  
Tidal Interactions ◽  
Mass Segregation ◽  
Gaia Dr2

ABSTRACT We have performed a detailed analysis of the Czernik 3 (Cz3) open cluster by using deep near-infrared photometry taken with TIRCAM2 on the 3.6 m Devasthal optical telescope along with the recently available high-quality proper motion data from the Gaia DR2 and deep photometric data from Pan-STARRS1. The cluster has a highly elongated morphology with fractal distribution of stars. The core and cluster radii of the cluster are estimated as 0.5 and 1.2 pc, respectively. We have identified 45 stars as cluster members using the Gaia proper motion data. The distance and age of the cluster are found to be 3.5 ± 0.9 kpc and $0.9^{+0.3}_{-0.1}$ Gyr, respectively. The slope of the mass function `Γ′ in the cluster region, in the mass range ∼0.95 <M/M⊙ < 2.2, is found to be −1.01 ± 0.43. The cluster shows the signatures of mass segregation and is dynamically relaxed (dynamical age = 10 Myr). This along with its small size, big tidal radius, low density/large separation of stars, and elongated and distorted morphology indicates that the Cz3 is a loosely bound disintegrating cluster under the influence of external tidal interactions.

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