- ID:
- ivo://CDS.VizieR/J/AJ/135/1225
- Title:
- Parameters of the local white dwarfs
- Short Name:
- J/AJ/135/1225
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a detailed new survey of the local population of white dwarfs lying within 20pc of the Sun. A new revised catalog of local white dwarfs containing 122 entries (126 individual degenerate stars) is presented. This list contains 27 white dwarfs not included in a previous list from 2002, as well as new and recently published trigonometric parallaxes. In several cases new members of the local white dwarf population have come to light through accurate photometric distance estimates. In addition, a suspected new double degenerate system (WD 0423+120) has been identified. The 20pc sample is currently estimated to be 80% complete. Using a variety of recent spectroscopic, photometric, and trigonometric distance determinations, we re-compute a space density of 4.8+/-0.5x10^-3^pc^-3^ corresponding to a mass density of 3.2+/-0.3x10^-3^M_{sun}_pc^-3^ from the complete portion of the sample within 13pc. We find an overall mean mass for the local white dwarfs of 0.665M_{sun}_, a value larger than most other non-volume-limited estimates. Although the sample is small, we find no evidence of a correlation between mass and temperature in which white dwarfs below 13000K are systematically more massive than those above this temperature. Within 20pc 25% of the white dwarfs are in binary systems (including double degenerate systems). Approximately 6% are double degenerates and 6.5% are Sirius-like systems. The fraction of magnetic white dwarfs in the local population is found to be 13%.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/462/2295
- Title:
- 25 parsec local white dwarf population
- Short Name:
- J/MNRAS/462/2295
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have extended our detailed survey of the local white dwarf population from 20 to 25pc, effectively doubling the sample volume, which now includes 232 stars. In the process, new stars within 20 pc have been added, a more uniform set of distance estimates as well as improved spectral and binary classifications are available. The present 25pc sample is estimated to be about 68 per cent complete (the corresponding 20pc sample is now 86 per cent complete). The space density of white dwarfs is unchanged at 4.8+/-0.5x10^-3^pc^-3^. This new study includes a white dwarf mass distribution and luminosity function based on the 232 stars in the 25pc sample. We find a significant excess of single stars over systems containing one or more companions (74 per cent versus 26 per cent). This suggests mechanisms that result in the loss of companions during binary system evolution. In addition, this updated sample exhibits a pronounced deficiency of nearby 'Sirius-like' systems. 11 such systems were found within the 20pc volume versus only one additional system found in the volume between 20 and 25pc. An estimate of white dwarf birth rates during the last ~8Gyr is derived from individual remnant cooling ages. A discussion of likely ways new members of the local sample may be found is provided.
- ID:
- ivo://CDS.VizieR/J/ApJ/667/1119
- Title:
- Photoionization of H in strong magnetic fields
- Short Name:
- J/ApJ/667/1119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A recently developed computational scheme, based on the complex-rotation method combined with a mixed Slater-Landau basis expansion, has been applied to calculations of photoionization from atomic hydrogen ground and excited states in a strong magnetic field typical of magnetic white dwarf stars. Photoionization cross sections are presented for the twelve states, 1s_0_, 2s_0_, 2p_0_, 2p_-1_, 3s'_0_, 3p_0_, 3p_-1_, 3d'_0_, 3d_-1_, 3d_-2_, 4f_-2_, and 4f_-3_, with magnetic field strengths from 23.5 to 2350MG.
- ID:
- ivo://CDS.VizieR/J/ApJ/742/3
- Title:
- Photometric catalogs for ECDF-S and CDF-N
- Short Name:
- J/ApJ/742/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of deep multiwavelength data for z~0.3-3 starburst galaxies selected by their 70um emission in the Extended-Chandra Deep Field-South and Extended Groth Strip. We identify active galactic nuclei (AGNs) in these infrared sources through their X-ray emission and quantify the fraction that host an AGN. Lastly, we investigate the ratio between the supermassive black hole accretion rate (inferred from the AGN X-ray luminosity) and the bulge growth rate of the host galaxy (approximated as the SFR) and find that, for sources with detected AGNs and star formation (and neglecting systems with low star formation rates to which our data are insensitive), this ratio in distant starbursts agrees well with that expected from the local scaling relation assuming the black holes and bulges grew at the same epoch. These results imply that black holes and bulges grow together during periods of vigorous star formation and AGN activity.
- ID:
- ivo://CDS.VizieR/J/AJ/128/1825
- Title:
- Photometry identification of cool white dwarfs
- Short Name:
- J/AJ/128/1825
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the use of a narrowband DDO51 filter for photometric identification of cool white dwarfs. We report photometric observations of 30 known cool white dwarfs with temperatures ranging from 10,000K down to very cool temperatures (<=3500K). Follow-up spectroscopic observations of a sample of objects selected using this filter and our photometric observations show that DDO51 filter photometry can help select cool white dwarf candidates for follow-up multiobject spectroscopy by rejecting 65% of main-sequence stars with the same broadband colors as the cool white dwarfs. This technique is not selective enough to efficiently feed single-object spectrographs. We present the white dwarf cooling sequence using this filter. Our observations show that very cool white dwarfs form a sequence in the r-DDO versus r-z color-color diagram and demonstrate that significant improvements are needed in white dwarf model atmospheres.
- ID:
- ivo://CDS.VizieR/J/A+A/651/A14
- Title:
- PM J22299+3024 and LP 119-10 light curves
- Short Name:
- J/A+A/651/A14
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We continued our ground-based observing project with the season-long observations of ZZ Ceti stars at the Konkoly Observatory. Our present targets are the newly discovered PM J22299+3024 and the already known LP 119-10 variables. LP 119-10 was also observed by the TESS space telescope in 120-second cadence mode. Our main aims are to characterise the pulsation properties of the targets and extract pulsation modes from the data for asteroseismic investigations. We performed a standard Fourier analysis of the daily, weekly, and entire data sets, together with test data of different combinations of weekly observations. We then performed asteroseismic fits utilising the observed and the calculated pulsation periods. For the calculations of model grids necessary for the fits, we applied the 2018 version of the White Dwarf Evolution Code. We derived six possible pulsation modes for PM J22299+3024 and five plus two TESS pulsation frequencies for LP 119-10. We note that further pulsation frequencies may be present in the data sets, but we found their detection ambiguous, so we omitted them from the final frequency list. Our asteroseismic fits of PM J22299+3024 give 11400K and 0.46M_{sun}_ for the effective temperature and the stellar mass, respectively. The temperature is ~800K higher, while the mass of the model star is exactly the same as was earlier derived by spectroscopy. Our model fits of LP 119-10 put the effective temperature in the range of 11800-11900K, which is again higher than the spectroscopic 11290K value. Moreover, our best model solutions give M*=0.70M_{sun}_ mass for this target, which is near to the spectroscopic value of 0.65M_{sun}_ and likewise in the case of PM J22299+3024. The seismic distances of our best-fit model stars agree with the Gaia astrometric distances of PM J22299+3024 and LP 119-10 within the errors, validating our model results.
- ID:
- ivo://CDS.VizieR/J/A+A/513/L7
- Title:
- Post common envelope binaries from SDSS. VIII
- Short Name:
- J/A+A/513/L7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a large survey of post common envelope binaries (PCEBs) among white dwarf/main sequence (WDMS) binaries from the SDSS that allows to determine the fraction of PCEBs as a function of secondary star mass and therewith to ultimately test the disrupted magnetic braking hypothesis. We obtained multiple spectroscopic observations spread over at least two nights of 589 WDMS binaries. Using mostly the NaI 8183.27,8194.81 absorption doublet we determined the corresponding radial velocities.
- ID:
- ivo://CDS.VizieR/J/MNRAS/435/2077
- Title:
- Properties of Sirius-like binary systems
- Short Name:
- J/MNRAS/435/2077
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Approximately 70% of the nearby white dwarfs appear to be single stars, with the remainder being members of binary or multiple star systems. The most numerous and most easily identifiable systems are those in which the main-sequence companion is an M star, since even if the systems are unresolved the white dwarf either dominates or is at least competitive with the luminosity of the companion at optical wavelengths. Harder to identify are systems where the non-degenerate component has a spectral type earlier than M0 and the white dwarf becomes the less luminous component. Taking Sirius as the prototype, these latter systems are referred to here as 'Sirius like'. There are currently 98 known Sirius-like systems. Studies of the local white dwarf population within 20pc indicate that approximately 8 percent of all white dwarfs are members of Sirius-like systems, yet beyond 20pc the frequency of known Sirius-like systems declines to between 1 and 2 percent, indicating that many more of these systems remain to be found. Estimates are provided for the local space density of Sirius-like systems and their relative frequency among both the local white dwarf population and the local population of A to K main-sequence stars. The great majority of currently unidentified Sirius-like systems will likely turn out to be closely separated and unresolved binaries. Ways to observationally detect and study these systems are discussed.
- ID:
- ivo://CDS.VizieR/J/ApJS/232/23
- Title:
- 27 pulsating DA WDs follow-up observations
- Short Name:
- J/ApJS/232/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present photometry and spectroscopy for 27 pulsating hydrogen-atmosphere white dwarfs (DAVs; a.k.a. ZZ Ceti stars) observed by the Kepler space telescope up to K2 Campaign 8, an extensive compilation of observations with unprecedented duration (>75 days) and duty cycle (>90%). The space-based photometry reveals pulsation properties previously inaccessible to ground- based observations. We observe a sharp dichotomy in oscillation mode line widths at roughly 800s, such that white dwarf pulsations with periods exceeding 800s have substantially broader mode line widths, more reminiscent of a damped harmonic oscillator than a heat-driven pulsator. Extended Kepler coverage also permits extensive mode identification: we identify the spherical degree of 87 out of 201 unique radial orders, providing direct constraints of the rotation period for 20 of these 27 DAVs, more than doubling the number of white dwarfs with rotation periods determined via asteroseismology. We also obtain spectroscopy from 4m-class telescopes for all DAVs with Kepler photometry. Using these homogeneously analyzed spectra, we estimate the overall mass of all 27 DAVs, which allows us to measure white dwarf rotation as a function of mass, constraining the endpoints of angular momentum in low- and intermediate-mass stars. We find that 0.51-0.73M{sun} white dwarfs, which evolved from 1.7-3.0M{sun} ZAMS progenitors, have a mean rotation period of 35hr with a standard deviation of 28hr, with notable exceptions for higher-mass white dwarfs.
- ID:
- ivo://CDS.VizieR/J/A+A/638/A131
- Title:
- Radial velocities of 643 DA white dwarfs
- Short Name:
- J/A+A/638/A131
- Date:
- 14 Jan 2022 08:18:09
- Publisher:
- CDS
- Description:
- Close double degenerate binaries are one of the favoured progenitor channels for type Ia supernovae, but it is unclear how many suitable systems there are in the Galaxy. We report results of a large radial velocity survey for double degenerate (DD) binaries using the UVES spectrograph at the ESO VLT (ESO SNIa Progenitor surveY - SPY). Exposures taken at different epochs are checked for radial velocity shifts indicating close binary systems.We observed 689 targets classified as DA (displaying hydrogen-rich atmospheres), of which 46 turned out to possess a cool companion. We measured radial velocities (RV) of the remaining 643 DA white dwarfs.We managed to secure observations at two or more epochs for 625 targets, supplemented by eleven objects meeting our selection criteria from literature. The data reduction and analysis methods applied to the survey data are described in detail. The sample contains 39 double degenerate binaries, only four of which were previously known. 20 are double-lined systems, in which features from both components are visible, the other 19 are single-lined binaries. We provide absolute RVs transformed to the heliocentric system suitable for kinematic studies. Our sample is large enough to sub-divide by mass: 16 out of 44 low mass targets (<=0.45M_{sun}_) are detected as DDs, while just 23 of the remaining 567 with multiple spectra and mass >0.45M_{sun}_ are double. Although the detected fraction amongst the low mass objects (36.4+/-7.3%) is significantly higher than for the higher-mass, carbon/oxygen-core dominated part of the sample (3.9+/-0.8%), it is lower than the detection efficiency based upon companion star masses of 0.05M_{sun}_ or higher and a 100% binary fraction. This suggests either companion stars of mass below 0.05M_{sun}_ or some of the low mass white dwarfs are single.
