Abstract
We present a spectroscopic survey of 248 white dwarf candidates within 40 pc of the Sun; of these 244 are in the Southern hemisphere. Observations were performed mostly with the Very Large ...Telescope (X-Shooter) and Southern Astrophysical Research Telescope. Almost all candidates were selected from Gaia Data Release 3 (DR3). We find a total of 246 confirmed white dwarfs, 209 of which had no previously published spectra, and two main-sequence star contaminants. Of these, 100 white dwarfs display hydrogen Balmer lines, 69 have featureless spectra, and two show only neutral helium lines. Additionally, 14 white dwarfs display traces of carbon, while 37 have traces of other elements that are heavier than helium. We observe 35 magnetic white dwarfs through the detection of Zeeman splitting of their hydrogen Balmer or metal spectral lines. High spectroscopic completeness (> 97 per cent) has now been reached, such that we have 1058 confirmed Gaia DR3 white dwarfs out of 1083 candidates within 40 pc of the Sun at all declinations.
ABSTRACT The unprecedented extent of coverage provided by Kepler observations recently revealed outbursts in two hydrogen-atmosphere pulsating white dwarfs (DAVs) that cause hours-long increases in ...the overall mean flux of up to 14%. We have identified two new outbursting pulsating white dwarfs in K2, bringing the total number of known outbursting white dwarfs to four. EPIC 211629697, with = 10,780 140 K and = 7.94 0.08, shows outbursts recurring on average every 5.0 days, increasing the overall flux by up to 15%. EPIC 229227292, with = 11,190 170 K and = 8.02 0.05, has outbursts that recur roughly every 2.4 days with amplitudes up to 9%. We establish that only the coolest pulsating white dwarfs within a small temperature range near the cool, red edge of the DAV instability strip exhibit these outbursts.
The INT Galactic Plane Survey (IGAPS) is the merger of the optical photometric surveys, IPHAS and UVEX, based on data from the
Isaac Newton
Telescope (INT) obtained between 2003 and 2018. Here, we ...present the IGAPS point source catalogue. It contains 295.4 million rows providing photometry in the filters,
i
,
r
, narrow-band H
α
,
g
, and
U
RGO
. The IGAPS footprint fills the Galactic coordinate range, |
b
| < 5° and 30° <
ℓ
< 215°. A uniform calibration, referred to as the Pan-STARRS system, is applied to
g
,
r
, and
i
, while the H
α
calibration is linked to
r
and then is reconciled via field overlaps. The astrometry in all five bands has been recalculated in the reference frame of
Gaia
Data Release 2. Down to
i
∼ 20 mag (Vega system), most stars are also detected in
g
,
r
, and H
α
. As exposures in the
r
band were obtained in both the IPHAS and UVEX surveys, typically a few years apart, the catalogue includes two distinct
r
measures,
r
I
and
r
U
. The
r
10
σ
limiting magnitude is approximately 21, with median seeing of 1.1 arcsec. Between approximately 13th and 19th mag in all bands, the photometry is internally reproducible to within 0.02 mag. Stars brighter than
r
= 19.5 mag are tested for narrow-band H
α
excess signalling line emission, and for variation exceeding |
r
I
−
r
U
| = 0.2 mag. We find and flag 8292 candidate emission line stars and over 53 000 variables (both at > 5
σ
confidence).
A catalogue of white dwarfs in Gaia EDR3 Gentile Fusillo, N. P.; Tremblay, P-E; Cukanovaite, E. ...
Monthly notices of the Royal Astronomical Society,
10/2021, Letnik:
508, Številka:
3
Journal Article
Recenzirano
We present a catalogue of white dwarf candidates selected from Gaia Early Data Release 3 (EDR3). We applied several selection criteria in absolute magnitude, colour, and Gaia quality flags to remove ...objects with unreliable measurements while preserving most stars compatible with the white dwarf locus in the Hertzsprung–Russell diagram. We then used a sample of over 30 000 spectroscopically confirmed white dwarfs and contaminants from the Sloan Digital Sky Survey (SDSS) to map the distribution of these objects in the Gaia absolute magnitude–colour space. Finally, we adopt the same method presented in our previous work on Gaia Data Release 2 (DR2) to calculate a probability of being a white dwarf (PWD) for ≃1.3 million sources that passed our quality selection. The PWD values can be used to select a sample of ${\simeq} 359\,000$ high-confidence white dwarf candidates. We calculated stellar parameters (effective temperature, surface gravity, and mass) for all these stars by fitting Gaia astrometry and photometry with synthetic pure-H, pure-He, and mixed H–He atmospheric models. We estimate an upper limit of 93 per cent for the overall completeness of our catalogue for white dwarfs with G ≤ 20 mag and effective temperature (Teff) > 7000 K, at high Galactic latitudes (|b| > 20°). Alongside the main catalogue we include a reduced proper motion extension containing ${\simeq} 10\,200$ white dwarf candidates with unreliable parallax measurements that could, however, be identified on the basis of their proper motion. We also performed a cross-match of our catalogues with SDSS Data Release 16 (DR16) spectroscopy and provide spectral classification based on visual inspection for all resulting matches.
The 40 pc sample of white dwarfs from Gaia O’Brien, Mairi W; Tremblay, P-E; Klein, B L ...
Monthly notices of the Royal Astronomical Society,
11/2023, Letnik:
527, Številka:
3
Journal Article
Recenzirano
Odprti dostop
ABSTRACT
We present a comprehensive overview of a volume-complete sample of white dwarfs located within 40 pc of the Sun, a significant proportion of which were detected in Gaia Data Release 3 (DR3). ...Our DR3 sample contains 1076 spectroscopically confirmed white dwarfs, with just five candidates within the volume remaining unconfirmed (> 99 per cent spectroscopic completeness). Additionally, 28 white dwarfs were not in our initial selection from Gaia DR3, most of which are in unresolved binaries. We use Gaia DR3 photometry and astrometry to determine a uniform set of white dwarf parameters, including mass, effective temperature, and cooling age. We assess the demographics of the 40 pc sample, specifically magnetic fields, binarity, space density, and mass distributions.
Aims.
We present the first detailed analysis of the astrophysical parameters of the poorly studied Sco-Cen member HD 152384 and its circumstellar environment.
Methods.
We analyse newly obtained ...optical-near-IR X-shooter spectra, as well as archival TESS data, of HD 152384. In addition, we use literature photometric data to construct a detailed spectral energy distribution (SED) of the star.
Results.
The photospheric absorption lines in the spectrum of HD 152384 are characteristic of an A0 V star, for which we derive a stellar mass of 2.1 ± 0.1
M
⊙
and a stellar age > 4.5 Myr. Superimposed on the photospheric absorption, the optical spectrum also displays double-peaked emission lines of Ca
II
, Fe
I
, Mg
I
, and Si
I
, typical of circumstellar disks. Notably, all hydrogen and helium lines appear strictly in absorption. A toy model shows that the observed emission line profiles can be reproduced by emission from a compact (radius < 0.3 au) disk seen at an inclination of ∼24°. Further evidence for the presence of circumstellar material comes from the detection of a moderate IR excess in the SED, similar to those found in extreme debris disk systems.
Conclusions.
We conclude that HD 152384 is surrounded by a tenuous circumstellar disk that, although rich in refractory elements, is highly depleted of volatile elements. To the best of our knowledge, such a disk is unique among young stars. However, it is reminiscent of the disks seen in some white dwarfs, which have been attributed to the disruption of rocky planets. We suggest that the disk around HD 152384 may have a similar origin and may be due to collisions in a newly formed planetary system.
Cataclysmic Variables (CVs) are binaries in which a white dwarf accretes from a low-mass companion star. CVs are the best-suited laboratories to test our understanding of the evolution of compact, ...interacting binaries as they are numerous, relatively bright, and both stellar components are structurally simple. Nonetheless, while a large fraction (≃40-80%) of the present-day Galactic CV population is expected to be old, highly evolved and to host brown dwarf companions, yet very few of these so-called “period bouncers” have been identified so far. The lack of these systems in the observed Galactic CV population possibly suggests that the physical mechanisms driving CV evolution (such as the common envelope phase, the mechanisms of angular momentum loss and/or the response of the companions to the mass loss) are still not completely understood.
The Compact binary HIgh CAdence Survey (CHiCaS) is a high cadence photometric survey performing three hours of uninterrupted time series photometry at one minute cadence over 136 square degrees of sky with JAST/T80Cam. CHiCaS aims to unambiguously identify the predicted large population of period-bounce CVs via detection of binary eclipses, thus providing an observational support for the current evolutionary models of all kind of compact binaries, such as black hole binaries, X-ray transients, double degenerates or SN Ia progenitors. Moreover, CHiCaS will deliver high cadence light curves along with full-colour information for about 2.5 million sources, thus identifying several hundred thousand variable stars, including eclipsing and contact binaries, pulsating and flaring stars, which will provide a significant legacy value.
Context. One-opposition near-Earth asteroids (NEAs) are growing in number, and they must be recovered to prevent loss and mismatch risk, and to improve their orbits, as they are likely to be too ...faint for detection in shallow surveys at future apparitions. Aims. We aimed to recover more than half of the one-opposition NEAs recommended for observations by the Minor Planet Center (MPC) using the Isaac Newton Telescope (INT) in soft-override mode and some fractions of available D-nights. During about 130 h in total between 2013 and 2016, we targeted 368 NEAs, among which 56 potentially hazardous asteroids (PHAs), observing 437 INT Wide Field Camera (WFC) fields and recovering 280 NEAs (76% of all targets). Methods. Engaging a core team of about ten students and amateurs, we used the THELI, Astrometrica, and the Find_Orb software to identify all moving objects using the blink and track-and-stack method for the faintest targets and plotting the positional uncertainty ellipse from NEODyS. Results. Most targets and recovered objects had apparent magnitudes centered around V ~ 22.8 mag, with some becoming as faint as V ~ 24 mag. One hundred and three objects (representing 28% of all targets) were recovered by EURONEAR alone by Aug. 2017. Orbital arcs were prolonged typically from a few weeks to a few years; our oldest recoveries reach 16 years. The O−C residuals for our 1854 NEA astrometric positions show that most measurements cluster closely around the origin. In addition to the recovered NEAs, 22 000 positions of about 3500 known minor planets and another 10 000 observations of about 1500 unknown objects (mostly main-belt objects) were promptly reported to the MPC by our team. Four new NEAs were discovered serendipitously in the analyzed fields and were promptly secured with the INT and other telescopes, while two more NEAs were lost due to extremely fast motion and lack of rapid follow-up time. They increase the counting to nine NEAs discovered by the EURONEAR in 2014 and 2015. Conclusions. Targeted projects to recover one-opposition NEAs are efficient in override access, especially using at least two-meter class and preferably larger field telescopes located in good sites, which appear even more efficient than the existing surveys.
The INT/WFC Photometric Hα Survey of the Northern Galactic Plane (IPHAS) is a 1800 deg2 imaging survey covering Galactic latitudes |b| < 5° and longitudes ℓ = 30°–215° in the r, i, and Hα filters ...using the Wide Field Camera (WFC) on the 2.5-m Isaac Newton Telescope (INT) in La Palma. We present the first quality-controlled and globally calibrated source catalogue derived from the survey, providing single-epoch photometry for 219 million unique sources across 92 per cent of the footprint. The observations were carried out between 2003 and 2012 at a median seeing of 1.1 arcsec (sampled at 0.33 arcsec pixel−1) and to a mean 5σ depth of 21.2 (r), 20.0 (i), and 20.3 (Hα) in the Vega magnitude system. We explain the data reduction and quality control procedures, describe and test the global re-calibration, and detail the construction of the new catalogue. We show that the new calibration is accurate to 0.03 mag (root mean square) and recommend a series of quality criteria to select accurate data from the catalogue. Finally, we demonstrate the ability of the catalogue's unique (r − Hα, r − i) diagram to (i) characterize stellar populations and extinction regimes towards different Galactic sightlines and (ii) select and quantify Hα emission-line objects. IPHAS is the first survey to offer comprehensive CCD photometry of point sources across the Galactic plane at visible wavelengths, providing the much-needed counterpart to recent infrared surveys.
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