scholarly journals Single magnetic white dwarfs with Balmer emission lines: a small class with consistent physical characteristics as possible signposts for close-in planetary companions

2020 ◽  
Vol 499 (2) ◽  
pp. 2564-2574
Author(s):  
Boris T Gänsicke ◽  
Pablo Rodríguez-Gil ◽  
Nicola P Gentile Fusillo ◽  
Keith Inight ◽  
Matthias R Schreiber ◽  
...  
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Late Onset ◽  
Spectral Energy Distribution ◽  
Giant Planet ◽  
Line Emission ◽  
Emission Lines ◽  
Spectral Energy ◽  
Common Mechanism ◽  
Small Class

ABSTRACT We report the identification of SDSS J121929.45+471522.8 as the third apparently isolated magnetic (B ≃ 18.5 ± 1.0 MG) white dwarf exhibiting Zeeman-split Balmer emission lines. The star shows coherent variability at optical wavelengths with an amplitude of ≃0.03 mag and a period of 15.26 h, which we interpret as the spin period of the white dwarf. Modelling the spectral energy distribution and Gaia parallax, we derive a white dwarf temperature of 7500 ± 148 K, a mass of 0.649 ± 0.022 M⊙, and a cooling age of 1.5 ± 0.1 Gyr, as well as an upper limit on the temperature of a sub-stellar or giant planet companion of ≃250 K. The physical properties of this white dwarf match very closely those of the other two magnetic white dwarfs showing Balmer emission lines: GD356 and SDSS J125230.93−023417.7. We argue that, considering the growing evidence for planets and planetesimals on close orbits around white dwarfs, the unipolar inductor model provides a plausible scenario to explain the characteristics of this small class of stars. The tight clustering of the three stars in cooling age suggests a common mechanism switching the unipolar inductor on and off. Whereas Lorentz drift naturally limits the lifetime of the inductor phase, the relatively late onset of the line emission along the white dwarf cooling sequence remains unexplained.

scholarly journals Infrared-excess white dwarfs in the Gaia 100 pc sample

2019 ◽  
Author(s):  
A Rebassa-Mansergas ◽  
E Solano ◽  
S Xu(#x8BB8;#x5072;#x827A;) ◽  
C Rodrigo ◽  
F M Jiménez-Esteban ◽  
...  
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Circumstellar Disk ◽  
Infrared Photometry ◽  
Brown Dwarf ◽  
Limited Sample ◽  
Infrared Excess ◽  
A Value

Abstract We analyse the 100 pc Gaia white dwarf volume-limited sample by means of VOSA (Virtual Observatory SED Analyser) with the aim of identifying candidates for displaying infrared excesses. Our search focuses on the study of the spectral energy distribution (SED) of 3,733 white dwarfs with reliable infrared photometry and GBP − GRP colours below 0.8 mag, a sample which seems to be nearly representative of the overall white dwarf population. Our search results in 77 selected candidates, 52 of which are new identifications. For each target we apply a two-component SED fitting implemented in VOSA to derive the effective temperatures of both the white dwarf and the object causing the excess. We calculate a fraction of infrared-excess white dwarfs due to the presence of a circumstellar disk of 1.6±0.2%, a value which increases to 2.6±0.3% if we take into account incompleteness issues. Our results are in agreement with the drop in the percentage of infrared excess detections for cool (<8,000 K) and hot (>20,000 K) white dwarfs obtained in previous analyses. The fraction of white dwarfs with brown dwarf companions we derive is ≃0.1–0.2%.

scholarly journals Investigating the young solar system analog HD 95086

2018 ◽  
Vol 617 ◽  
pp. A76 ◽  
Author(s):  
G. Chauvin ◽  
R. Gratton ◽  
M. Bonnefoy ◽  
A.-M. Lagrange ◽  
J. de Boer ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Near Infrared ◽  
Scattered Light ◽  
Spectral Energy Distribution ◽  
Giant Planet ◽  
Giant Planets ◽  
Dual Band ◽  
Spectral Energy ◽  
Semi Major Axis ◽  
Integral Field Spectrograph

Context. HD 95086 (A8V, 17 Myr) hosts a rare planetary system for which a multi-belt debris disk and a giant planet of 4–5 MJup have been directly imaged. Aims. Our study aims to characterize the global architecture of this young system using the combination of radial velocity and direct imaging observations. We want to characterize the physical and orbital properties of HD 95086 b, search for additional planets at short and wide orbits and image the cold outer debris belt in scattered light. Methods. We used HARPS at the ESO 3.6 m telescope to monitor the radial velocity of HD 95086 over two years and investigate the existence of giant planets at less than 3 au orbital distance. With the IRDIS dual-band imager and the IFS integral field spectrograph of SPHERE at VLT, we imaged the faint circumstellar environment beyond 10 au at six epochs between 2015 and 2017. Results. We do not detect additional giant planets around HD 95086. We identify the nature (bound companion or background contaminant) of all point-like sources detected in the IRDIS field of view. None of them correspond to the ones recently discovered near the edge of the cold outer belt by ALMA. HD 95086 b is resolved for the first time in J-band with IFS. Its near-infrared spectral energy distribution is well fitted by a few dusty and/or young L7–L9 dwarf spectral templates. The extremely red 1–4 μm spectral distribution is typical of low-gravity objects at the L/T spectral type transition. The planet’s orbital motion is resolved between January 2015 and May 2017. Together with past NaCo measurements properly re-calibrated, our orbital fitting solutions favor a retrograde low to moderate-eccentricity orbit e = 0.2+0.3−0.2, with a semi-major axis ~52 au corresponding to orbital periods of ~288 yr and an inclination that peaks at i = 141°, which is compatible with a planet-disk coplanar configuration. Finally, we report the detection in polarimetric differential imaging of the cold outer debris belt between 100 and 300 au, consistent in radial extent with recent ALMA 1.3 mm resolved observations.

scholarly journals The Hα line emission of the Be star β Psc: the last 40 yr

2020 ◽  
Vol 501 (1) ◽  
pp. 747-755
Author(s):  
Ronaldo S Levenhagen ◽  
Marcos P Diaz ◽  
Eduardo B Amôres ◽  
Nelson V Leister
Keyword(s):  
Additional Data ◽  
State Of The Art ◽  
Spectral Energy Distribution ◽  
Line Emission ◽  
Spectral Energy ◽  
Line Profiles ◽  
Gas Density ◽  
Geometric Deformation ◽  
Be Star ◽  
Effects Of Rotation

ABSTRACT A study on the photosphere and disc of the Be star β Psc is presented. We recover almost 40 yr of high-resolution spectroscopic observations and additional data gathered from the BeSS data base. We evaluate the photospheric parameters from the spectral energy distribution (SED) and fittings of state-of-the-art non-LTE model atmospheres to observed helium, carbon, silicon, and magnesium line profiles. Our models include the stellar geometric deformation as well as the co-latitude dependence of temperature and gravity, aiming to derive the effects of rotation on the stellar parameters. We estimate the circumstellar disc parameters from the fitting of models assuming different disc properties, namely its radius and gas density profile. The disc inclination angle i is constrained from the fittings of He i 4471 Å, Mg ii 4481 Å, C ii 4267 Å,  and Si ii 4128, 4132 Å  lines with gravity darkened models. Our findings, based on model fittings, suggest that during the last 40 yr, the disc radius changed within the interval 5.5 ≤ Rd ≤ 7.8 $R/R_{*}\,$, the disc base gas density within 5 × 10−13 ≤ ρ ≤ 1 × 10−12 g cm−3, while the radial power-law density index m assumed values between 2.0 and 2.3. These results are in agreement with recent works dealing with spectroscopic and interferometric measurements of this object.

scholarly journals Tidal circularization of gaseous planets orbiting white dwarfs

2019 ◽  
Vol 489 (2) ◽  
pp. 2941-2953 ◽  
Author(s):  
Dimitri Veras ◽  
Jim Fuller
Keyword(s):  
Phase Space ◽  
White Dwarf ◽  
Metal Pollution ◽  
White Dwarfs ◽  
Thermal Destruction ◽  
Giant Planet ◽  
Giant Planets ◽  
Potential Source ◽  
Mode Excitation ◽  
Coupled Constraints

ABSTRACT A gas giant planet which survives the giant branch stages of evolution at a distance of many au and then is subsequently perturbed sufficiently close to a white dwarf will experience orbital shrinkage and circularization due to star–planet tides. The circularization time-scale, when combined with a known white dwarf cooling age, can place coupled constraints on the scattering epoch as well as the active tidal mechanisms. Here, we explore this coupling across the entire plausible parameter phase space by computing orbit shrinkage and potential self-disruption due to chaotic f-mode excitation and heating in planets on orbits with eccentricities near unity, followed by weakly dissipative equilibrium tides. We find that chaotic f-mode evolution activates only for orbital pericentres which are within twice the white dwarf Roche radius, and easily restructures or destroys ice giants but not gas giants. This type of internal thermal destruction provides an additional potential source of white dwarf metal pollution. Subsequent tidal evolution for the surviving planets is dominated by non-chaotic equilibrium and dynamical tides which may be well-constrained by observations of giant planets around white dwarfs at early cooling ages.

scholarly journals The frequency of gaseous debris discs around white dwarfs

2020 ◽  
Vol 493 (2) ◽  
pp. 2127-2139 ◽  
Author(s):  
Christopher J Manser ◽  
Boris T Gänsicke ◽  
Nicola Pietro Gentile Fusillo ◽  
Richard Ashley ◽  
Elmé Breedt ◽  
...  
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Signal To Noise Ratio ◽  
Infrared Emission ◽  
Sloan Digital Sky Survey ◽  
Emission Lines ◽  
Occurrence Rate ◽  
Limited Sample ◽  
Sky Survey ◽  
Gaseous Disc

ABSTRACT A total of 1–3 per cent of white dwarfs are orbited by planetary dusty debris detectable as infrared emission in excess above the white dwarf flux. In a rare subset of these systems, a gaseous disc component is also detected via emission lines of the Ca ii 8600 Å triplet, broadened by the Keplerian velocity of the disc. We present the first statistical study of the fraction of debris discs containing detectable amounts of gas in emission at white dwarfs within a magnitude and signal-to-noise ratio limited sample. We select 7705 single white dwarfs spectroscopically observed by the Sloan Digital Sky Survey (SDSS) and Gaia with magnitudes g ≤ 19. We identify five gaseous disc hosts, all of which have been previously discovered. We calculate the occurrence rate of a white dwarf hosting a debris disc detectable via Ca ii emission lines as $0.067\, \pm \, ^{0.042}_{0.025}$ per cent. This corresponds to an occurrence rate for a dusty debris disc to have an observable gaseous component in emission as 4 ± $_{2}^{4}$ per cent. Given that variability is a common feature of the emission profiles of gaseous debris discs, and the recent detection of a planetesimal orbiting within the disc of SDSS J122859.93+104032.9, we propose that gaseous components are tracers for the presence of planetesimals embedded in the discs and outline a qualitative model. We also present spectroscopy of the Ca ii triplet 8600 Å region for 20 white dwarfs hosting dusty debris discs in an attempt to identify gaseous emission. We do not detect any gaseous components in these 20 systems, consistent with the occurrence rate that we calculated.

scholarly journals An ALMA survey of the brightest sub-millimetre sources in the SCUBA-2–COSMOS field

2020 ◽  
Vol 495 (3) ◽  
pp. 3409-3430 ◽  
Author(s):  
J M Simpson ◽  
Ian Smail ◽  
U Dudzevičiūtė ◽  
Y Matsuda ◽  
B-C Hsieh ◽  
...  
Keyword(s):  
Pilot Study ◽  
Flux Density ◽  
Luminosity Function ◽  
Spectral Energy Distribution ◽  
Line Emission ◽  
Spectral Energy ◽  
Complete Sample ◽  
Photometric Redshifts ◽  
Photometric Redshift ◽  
Number Counts

ABSTRACT We present an ALMA study of the ∼180 brightest sources in the SCUBA-2 850-μm map of the COSMOS field from the S2COSMOS survey, as a pilot study for AS2COSMOS – a full survey of the ∼1000 sources in this field. In this pilot study, we have obtained 870-μm continuum maps of an essentially complete sample of the brightest 182 sub-millimetre sources ($S_{850\, \mu \rm m}\gt $ 6.2 mJy) in COSMOS. Our ALMA maps detect 260 sub-millimetre galaxies (SMGs) spanning a range in flux density of $S_{870\, \mu \rm m}$ = 0.7–19.2 mJy. We detect more than one SMG counterpart in 34 ± 2 per cent of sub-millimetre sources, increasing to 53 ± 8 per cent for SCUBA-2 sources brighter than $S_{850\, \mu \rm m}\gt $ 12 mJy. We estimate that approximately one-third of these SMG–SMG pairs are physically associated (with a higher rate for the brighter secondary SMGs, $S_{870\, \mu \rm m}\gtrsim$ 3 mJy), and illustrate this with the serendipitous detection of bright [C ii] 157.74-μm line emission in two SMGs, AS2COS 0001.1 and 0001.2 at z = 4.63, associated with the highest significance single-dish source. Using our source catalogue, we construct the interferometric 870-μm number counts at $S_{870\, \mu \rm m}\gt $ 6.2 mJy. We use the extensive archival data of this field to construct the multiwavelength spectral energy distribution of each AS2COSMOS SMG, and subsequently model this emission with magphys to estimate their photometric redshifts. We find a median photometric redshift for the $S_{870\, \mu \rm m}\gt $ 6.2 mJy AS2COSMOS sample of z = 2.87 ± 0.08, and clear evidence for an increase in the median redshift with 870-μm flux density suggesting strong evolution in the bright end of the 870-μm luminosity function.

scholarly journals Hint of curvature in the orbital motion of the exoplanet 51 Eridani b using 3 yr of VLT/SPHERE monitoring

2019 ◽  
Vol 624 ◽  
pp. A118 ◽  
Author(s):  
A.-L. Maire ◽  
L. Rodet ◽  
F. Cantalloube ◽  
R. Galicher ◽  
W. Brandner ◽  
...  
Keyword(s):  
Orbital Motion ◽  
Rotation Axis ◽  
Spectral Energy Distribution ◽  
Giant Planet ◽  
Spectral Energy ◽  
Spin Orbit ◽  
Stellar Rotation ◽  
Semi Major Axis ◽  
Primary Star ◽  
Orbital Parameters

Context. The 51 Eridani system harbors a complex architecture with its primary star forming a hierarchical system with the binary GJ 3305AB at a projected separation of 2000 au, a giant planet orbiting the primary star at 13 au, and a low-mass debris disk around the primary star with possible cold and warm components inferred from the spectral energy distribution. Aims. We aim to better constrain the orbital parameters of the known giant planet. Methods. We monitored the system over three years from 2015 to 2018 with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument at the Very Large Telescope (VLT). Results. We measure an orbital motion for the planet of ~130 mas with a slightly decreasing separation (~10 mas) and find a hint of curvature. This potential curvature is further supported at 3σ significance when including literature Gemini Planet Imager (GPI) astrometry corrected for calibration systematics. Fits of the SPHERE and GPI data using three complementary approaches provide broadly similar results. The data suggest an orbital period of 32−9+17 yr (i.e., 12−2+4 au in semi-major axis), an inclination of 133−7+14 deg, an eccentricity of 0.45−0.15+0.10, and an argument of periastron passage of 87−30+34 deg [mod 180°]. The time at periastron passage and the longitude of node exhibit bimodal distributions because we do not yet detect whether the planet is accelerating or decelerating along its orbit. Given the inclinations of the orbit and of the stellar rotation axis (134–144°), we infer alignment or misalignment within 18° for the star–planet spin-orbit. Further astrometric monitoring in the next 3–4 yr is required to confirm at a higher significance the curvature in the motion of the planet, determine if the planet is accelerating or decelerating on its orbit, and further constrain its orbital parameters and the star–planet spin-orbit.

scholarly journals Properties of LBGs with [OIII] detection at z ∼ 3.5

2019 ◽  
Vol 631 ◽  
pp. A123 ◽  
Author(s):  
Fang-Ting Yuan ◽  
Denis Burgarella ◽  
David Corre ◽  
Veronique Buat ◽  
Médéric Boquien ◽  
...  
Keyword(s):  
Physical Properties ◽  
Emission Line ◽  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Line Emission ◽  
Stellar Mass ◽  
Spectral Energy ◽  
Emission Data ◽  
The Impact

Context. Nebular emission lines are critical to measure physical properties in the ionized gas (e.g., metallicity, the star formation rate, or dust attenuation). They also account for a significant fraction of broadband fluxes, in particular at the highest redshifts, and therefore can strongly affect the determination of other physical properties, such as the stellar mass, which are crucial in shaping our understanding of galaxy formation and evolution. Aims. We investigate a sample of 51 Lyman break galaxies at 3.0 <  zspec <  3.8 with detected [OIII] line emissions and estimated the physical properties of these galaxies to examine the impact of including nebular emission data in the Spectral energy distribution (SED) fitting. Methods. We used the Code Investigating GALaxy Emission (CIGALE) to fit the rest-frame ultraviolet-to-near-infrared SEDs of these galaxies and their emission line data simultaneously. We ran CIGALE with and without the nebular model or the emission line data, and compare the results to show the importance of including the nebular emission line data in the SED fitting. Results. We find that without the nebular model, the SED fitting overestimates the stellar mass due to the strong [OIII] lines that are redshifted to the Ks-band, which is consistent with previous results. The emission line data are necessary to constrain the nebular model in the SED fitting. We examine the Ks-band excess, which is mostly used to estimate the emissions of the [OIII]+Hβ lines when there is no spectral data, and we find that the estimation and observation are statistically consistent. However, the difference can reach up to more than 1 dex in some catastrophic cases, which shows the importance of obtaining spectroscopic measurements for these lines. We also estimate the equivalent width of the Hβ absorption and find it negligible compared to the Hβ emission. Conclusions. Line emission is important to constrain the nebular models and to obtain reliable estimates of the physical properties of galaxies. These data should be taken into account in the SED fitting.

The Complete Spectral Energy Distribution and the Atmospheric Properties of the Helium-Rich White Dwarf MCT 0501−2858

1998 ◽  
Vol 500 (1) ◽  
pp. L41-L44 ◽  
Author(s):  
Stéphane Vennes ◽  
Jean Dupuis ◽  
Pierre Chayer ◽  
Elisha F. Polomski ◽  
William Van Dyke Dixon ◽  
...  
Keyword(s):  
Energy Distribution ◽  
White Dwarf ◽  
Spectral Energy Distribution ◽  
Spectral Energy

scholarly journals The ‘Red Radio Ring’: ionized and molecular gas in a starburst/active galactic nucleus at z ∼ 2.55

2019 ◽  
Vol 488 (2) ◽  
pp. 1489-1500 ◽  
Author(s):  
Kevin C Harrington ◽  
A Vishwas ◽  
A Weiß ◽  
B Magnelli ◽  
L Grassitelli ◽  
...  
Keyword(s):  
Fine Structure ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Line Emission ◽  
Far Infrared ◽  
Spectral Energy ◽  
Molecular Gas ◽  
H Ii Regions ◽  
Galaxy Assembly ◽  
Dust Attenuation

ABSTRACT We report the detection of the far-infrared (FIR) fine-structure line of singly ionized nitrogen, [N ii] 205 $\mu$m , within the peak epoch of galaxy assembly, from a strongly lensed galaxy, hereafter ‘The Red Radio Ring’; the RRR, at z = 2.55. We combine new observations of the ground-state and mid-J transitions of CO (Jup = 1, 5, 8), and the FIR spectral energy distribution (SED), to explore the multiphase interstellar medium (ISM) properties of the RRR. All line profiles suggest that the H ii regions, traced by [N ii] 205 $\mu$m , and the (diffuse and dense) molecular gas, traced by CO, are cospatial when averaged over kpc-sized regions. Using its mid-IR-to-millimetre (mm) SED, we derive a non-negligible dust attenuation of the [N ii] 205 $\mu$m line emission. Assuming a uniform dust screen approximation results a mean molecular gas column density &gt;1024 cm−2, with a molecular gas-to-dust mass ratio of 100. It is clear that dust attenuation corrections should be accounted for when studying FIR fine-structure lines in such systems. The attenuation corrected ratio of $L_{\rm N\,{\small II}205} / L_{\rm IR(8\!-\!1000\, \mu m)} = 2.7 \times 10^{-4}$ is consistent with the dispersion of local and z &gt; 4 SFGs. We find that the lower limit, [N ii] 205 $\mu$m -based star formation rate (SFR) is less than the IR-derived SFR by a factor of 4. Finally, the dust SED, CO line SED, and $L_{\rm N\,{\small II}205}$ line-to-IR luminosity ratio of the RRR is consistent with a starburst-powered ISM.

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