<i>Gaia</i> DR2 white dwarfs in the Hercules stream

Torres, Santiago; Cantero, C.; Camisassa, María E.; Antoja, T.; Rebassa‐Mansergas, A.; Althaus, Leandro Gabriel; Thelemaque, Thomas; Cánovas, H.

doi:10.1051/0004-6361/201936244

Cited by 9 publications

(7 citation statements)

References 45 publications

(50 reference statements)

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“…There are only seven isolated white dwarfs and two common proper motion pairs that are halo candidates, corresponding to less than 0.3% of the respective samples. While this result is just a factor of three smaller than the halo fraction identified by Torres et al (2019b) in their analysis of the 100 pc Gaia DR2 white dwarf sample, pre-Gaia results by Pauli et al (2006) and Richter et al (2007) found 2% and <5%, respectively, halo members in the SPY sample. A Gaia DR2 update on this sample leveled down the estimate to about 1% (Dimpel 2018).…”

Section: Kinematic and Dynamic Propertiesmentioning

confidence: 53%

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Kinematic properties of white dwarfs

Raddi

Torres

Rebassa‐Mansergas

et al. 2022

A&A

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Context. Kinematic and chemical tagging of stellar populations have both revealed much information on the past and recent history of the Milky Way, including its formation history, merger events, and mixing of populations across the Galactic disk and halo. Aims. We present the first detailed 3D kinematic analysis of a sample of 3133 white dwarfs that used Gaia astrometry plus radial velocities, which were measured either by Gaia or by ground-based spectroscopic observations. The sample includes either isolated white dwarfs that have direct radial velocity measurements, or white dwarfs that belong to common proper motion pairs that contain nondegenerate companions with available radial velocities. A subset of common proper motion pairs also have metal abundances that have been measured by large-scale spectroscopic surveys or by our own follow-up observations. Methods. We used the white dwarfs as astrophysical clocks by determining their masses and total ages through interpolation with dedicated evolutionary models. We also used the nondegenerate companions in common proper motions to chemically tag the population. Combining accurate radial velocities with Gaia astrometry and proper motions, we derived the velocity components of our sample in the Galactic rest frame and their Galactic orbital parameters. Results. The sample is mostly located within ∼300 pc from the Sun. It predominantly contains (90–95%) thin-disk stars with almost circular Galactic orbits, while the remaining 5–10% of stars have more eccentric trajectories and belong to the thick disk. We identified seven isolated white dwarfs and two common proper motion pairs as halo members. We determined the age – velocity dispersion relation for the thin-disk members, which agrees with previous results that were achieved from different white dwarf samples without published radial velocities. The age – velocity dispersion relation shows signatures of dynamical heating and saturation after 4–6 Gyr. We observed a mild anticorrelation between [Fe/H] and the radial component of the average velocity dispersion, showing that dynamical mixing of populations takes place in the Galactic disk, as was detected through the analysis of other samples of FGK stars. Conclusions. We have shown that a white dwarf sample with accurate 3D kinematics and well-measured chemical compositions enables a wider understanding of their population in the solar neighborhood and its connection with the Galactic chemodynamics. The legacy of existing spectroscopic surveys will be boosted by the availability of upcoming larger samples of white dwarfs and common proper motion pairs with more uniform high-quality data.

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Section: Kinematic and Dynamic Propertiesmentioning

confidence: 53%

“…The random forest classification of the 100 pc sample presented by Torres et al (2019b) used Gaia DR2 astrometry and ages, but did not include radial velocities. Three of their halo candidates are isolated white dwarfs in our sample (numbers 0703, 1461, and 2014) and were also classified as halo members above.…”

Section: Kinematic and Dynamic Propertiesmentioning

confidence: 99%

Kinematic properties of white dwarfs

Raddi

Torres

Rebassa‐Mansergas

et al. 2022

A&A

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“…For Hercules stream, it has three substructures. The age distribution is peaked at 4 Gyr and extend to very old age for Hercules a and Hercules b; and Hercules c has a more uniform age distribution from ∼ 2 − 10 Gyr (Torres et al 2019).…”

Section: Kinematic Ages Of Planet Host Stars In the Galactic Diskmentioning

confidence: 92%

Planets Across Space and Time (PAST). I. Characterizing the Memberships of Galactic Components and Stellar Ages: Revisiting the Kinematic Methods and Applying to Planet Host Stars

Chen,

Xie,

Zhou

et al. 2021

Preprint

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Over 4,000 exoplanets have been identified and thousands of candidates are to be confirmed. The relations between the characteristics of these planetary systems and the kinematics, Galactic components, and ages of their host stars have yet to be well explored. Aiming to addressing these questions, we conduct a research project, dubbed as PAST (Planets Across Space and Time). To do this, one of the key steps is to accurately characterize the planet host stars. In this paper, the Paper I of the PAST series, we revisit the kinematic method for classification of Galactic components and extend the applicable range of velocity ellipsoid from ∼ 100 pc to ∼ 1, 500 pc from the sun in order to cover most known planet hosts. Furthermore, we revisit the Age-Velocity dispersion Relation (AVR), which allows us to derive kinematic age with a typical uncertainty of 10-20% for an ensemble of stars. Applying the above revised methods, we present a catalog of kinematic properties (i.e. Galactic positions, velocities, the relative membership probabilities among the thin disk, thick disk, Hercules stream, and the halo) as well as other basic stellar parameters for 2,174 host stars of 2,872 planets by combining data from Gaia, LAMOST, APOGEE, RAVE, and the NASA exoplanet archive. The revised kinematic method and AVR as well as the stellar catalog of kinematic properties and ages lay foundation for future studies on exoplanets from two dimensions of space and time in the Galactic context.

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“…Despite the biases that this assumption may induce, (e.g. Pauli et al 2006;Torres et al 2019a) some of the clustering properties of the sample can remain unaltered (Fuchs & Dettbarn 2011;Torres et al 2019b). In this sense, we use the integral of motion space as an appropriate tool for analyzing our sample (e.g Helmi et al 2006).…”

Section: Kinematics Of the Halo White Dwarf Samplementioning

confidence: 99%

The Gaia DR2 halo white dwarf population: the luminosity function, mass distribution, and its star formation history

Torres

Rebassa‐Mansergas

Camisassa

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We analyse the volume-limited nearly complete 100 pc sample of 95 halo white dwarf candidates identified by the second data release of Gaia. Based on a detailed population synthesis model, we apply a method that relies on Gaia astrometry and photometry to accurately derive the individual white dwarf parameters. This method is tested with 25 white dwarfs of our sample for which we took optical spectra and performed spectroscopic analysis. We build and analyse the halo white dwarf luminosity function, for which we find for the first time possible evidences of the cut-off, leading to an age estimate of ${\simeq}12\pm 0.5$ Gyr. The mass distribution of the sample peaks at $0.589\, \mathrm{ M}_{\odot }$, with $71{{\ \rm per\ cent}}$ of the white dwarf masses below $0.6\, \mathrm{ M}_{\odot }$ and just two massive white dwarfs of more than $0.8\, \mathrm{ M}_{\odot }$. From the age distribution, we find three white dwarfs with total ages above 12 Gyr, of which J1312−4728 is the oldest white dwarf known with an age of $12.41\pm 0.22\,$ Gyr. We prove that the star formation history is mainly characterized by a burst of star formation that occurred from 10 to 12 Gyr in the past, but extended up to 8 Gyr. We also find that the peak of the star formation history is centred at around 11 Gyr, which is compatible with the current age of the Gaia-Enceladus encounter. Finally, $13{{\ \rm per\ cent}}$ of our halo sample is contaminated by high-speed young objects (total age <7 Gyr). The origin of these white dwarfs is unclear but their age distribution may be compatible with the encounter with the Sagittarius galaxy.

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Gaia DR2 white dwarfs in the Hercules stream

Cited by 9 publications

References 45 publications

Kinematic properties of white dwarfs

Kinematic properties of white dwarfs

Planets Across Space and Time (PAST). I. Characterizing the Memberships of Galactic Components and Stellar Ages: Revisiting the Kinematic Methods and Applying to Planet Host Stars

The Gaia DR2 halo white dwarf population: the luminosity function, mass distribution, and its star formation history

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