Near-infrared observations of dusty white dwarfs

2019 ◽  
Vol 15 (S357) ◽  
pp. 33-36
Author(s):  
Laura K. Rogers ◽  
Siyi Xu ◽  
Amy Bonsor ◽  
Simon Hodgkin ◽  
Kate Y. L. Su ◽  
...  
Keyword(s):  
Stochastic Process ◽  
White Dwarfs ◽  
Near Infrared ◽  
Dust Emission ◽  
Colour Change ◽  
Infrared Emission ◽  
Tidal Disruption ◽  
Process Variability ◽  
Infrared Observations ◽  
Excess Emission

AbstarctPlanetary material in the atmospheres of white dwarfs is thought to be scattered inwards from outer planetary systems. Dusty emission in the infrared traces the accretion. As the scattering of many small asteroids is a stochastic process, variability in the infrared emission is predicted. We report a 3 year near-infrared (J, H and K) monitoring campaign of 34 dusty, polluted white dwarfs which aims to search for dust emission variability. We find all white dwarfs have consistent near-infrared fluxes, implying the excess emission is stable. This suggests tidal disruption events which lead to large variabilities are rare and quick (<1 year) and become stable within a few years. For WD 0408–041, the system that shows both increases and decreases in dust emission over 11 years, our K band data suggest a potential colour change associated with the dust emission that needs further confirmation.

scholarly journals Near-infrared variability in dusty white dwarfs: tracing the accretion of planetary material

2020 ◽  
Vol 494 (2) ◽  
pp. 2861-2874 ◽  
Author(s):  
Laura K Rogers ◽  
Siyi Xu (许偲艺) ◽  
Amy Bonsor ◽  
Simon Hodgkin ◽  
Kate Y L Su ◽  
...  
Keyword(s):  
Time Scales ◽  
White Dwarf ◽  
White Dwarfs ◽  
Near Infrared ◽  
Dust Emission ◽  
Infrared Emission ◽  
Wide Field ◽  
Infrared Telescope ◽  
Infrared Monitoring ◽  
K Band

ABSTRACT The inwards scattering of planetesimals towards white dwarfs is expected to be a stochastic process with variability on human time-scales. The planetesimals tidally disrupt at the Roche radius, producing dusty debris detectable as excess infrared emission. When sufficiently close to the white dwarf, this debris sublimates and accretes on to the white dwarf and pollutes its atmosphere. Studying this infrared emission around polluted white dwarfs can reveal how this planetary material arrives in their atmospheres. We report a near-infrared monitoring campaign of 34 white dwarfs with infrared excesses with the aim to search for variability in the dust emission. Time series photometry of these white dwarfs from the United Kingdom Infrared Telescope (Wide Field Camera) in the J-, H-, and K-bands was obtained over baselines of up to 3 yr. We find no statistically significant variation in the dust emission in all three near-infrared bands. Specifically, we can rule out variability at ∼1.3 per cent for the 13 white dwarfs brighter than 16th mag in K-band, and at ∼10 per cent for the 32 white dwarfs brighter than 18th mag over time-scales of 3 yr. Although to date two white dwarfs, SDSS J095904.69−020047.6 and WD 1226+110, have shown K-band variability, in our sample we see no evidence of new K-band variability at these levels. One interpretation is that the tidal disruption events that lead to large variabilities are rare occur on short time-scales, and after a few years the white dwarfs return to being stable in the near-infrared.

scholarly journals Carbonaceous nano-dust emission in proto-planetary discs: the aliphatic-aromatic components

2019 ◽  
Vol 623 ◽  
pp. A135 ◽  
Author(s):  
T. Boutéraon ◽  
E. Habart ◽  
N. Ysard ◽  
A. P. Jones ◽  
E. Dartois ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Interstellar Dust ◽  
Near Infrared ◽  
Solid Phase ◽  
Dust Emission ◽  
Emission Spectra ◽  
Infrared Emission ◽  
Constant Intensity ◽  
Aromatic Components ◽  
Nano Grains

Context. In the interstellar medium, carbon (nano-)grains are a major component of interstellar dust. This solid phase is more vulnerable to processing and destruction than its silicate counterpart. It exhibits a complex, size-dependent evolution that is due to interactions within different radiative and dynamical environments. Infrared signatures of these carbon nano-grains are seen in a large number of discs around Herbig HAeBe stars. Aims. We probe the composition and evolution of carbon nano-grains at the surface of (pre-)transitional proto-planetary discs around Herbig stars. Methods. We present spatially resolved infrared emission spectra obtained with the Nasmyth Adaptive Optics System (NAOS) Near-Infrared Imager and Spectrograph (CONICA) at the Very Large Telescope (VLT) in the 3–4 μm range with a spatial resolution of 0.1′′, which allowed us to trace aromatic, olefinic, and aliphatic bands that are attributed to sub-nanometer hydrocarbon grains. We applied a Gaussian fitting to analyse the observed spectral signatures. Finally, we propose an interpretation in the framework of the The Heterogeneous dust Evolution Model of Interstellar Solids (THEMIS). Results. We show the presence of several spatially extended spectral features that are related to aromatic and aliphatic hydrocarbon material in discs around Herbig stars, from ~10 to 50–100 au, and even in inner gaps that are devoid of large grains. The correlation and constant intensity ratios between aliphatic and aromatic CH stretching bands suggests a common nature of the carriers. Given their expected high destruction rates through UV photons, our observations suggest that they are continuously replenished at the disc surfaces.

scholarly journals Multiwavelength modelling of the circumstellar environment of the massive protostar AFGL 2591 VLA 3

2020 ◽  
Vol 498 (4) ◽  
pp. 4721-4744
Author(s):  
F A Olguin ◽  
M G Hoare ◽  
K G Johnston ◽  
F Motte ◽  
H-R V Chen ◽  
...  
Keyword(s):  
Near Infrared ◽  
Dust Emission ◽  
Continuum Emission ◽  
Model Parameters ◽  
Infrared Observations ◽  
Slowing Down ◽  
Stellar Masses ◽  
First Time ◽  
Line Fitting ◽  
Circumstellar Environment

ABSTRACT We have studied the dust density, temperature, and velocity distributions of the archetypal massive young stellar object (MYSO) AFGL 2591. Given its high luminosity ($L=2\times 10^5\, \mbox{L$_{\odot}$}$) and distance (d = 3.3 kpc), AFGL 2591 has one of the highest $\sqrt{L}/d$ ratio, giving better resolved dust emission than any other MYSO. As such, this paper provides a template on how to use resolved multiwavelength data and radiative transfer to obtain a well-constrained 2D axisymmetric analytic rotating infall model. We show for the first time that the resolved dust continuum emission from Herschel 70- μm observations is extended along the outflow direction, whose origin is explained in part from warm dust in the outflow cavity walls. However, the model can only explain the kinematic features from CH3CN observations with unrealistically low stellar masses (&lt;15 M⊙), indicating that additional physical processes may be playing a role in slowing down the envelope rotation. As part of our three-step continuum and line fitting, we have identified model parameters that can be further constrained by specific observations. High-resolution mm visibilities were fitted to obtain the disc mass (6 M⊙) and radius (2200 au). A combination of SED and near-infrared observations were used to estimate the luminosity and envelope mass together with the outflow cavity inclination and opening angles.

scholarly journals The dust content of the Crab Nebula

2019 ◽  
Vol 488 (1) ◽  
pp. 164-182 ◽  
Author(s):  
I De Looze ◽  
M J Barlow ◽  
R Bandiera ◽  
A Bevan ◽  
M F Bietenholz ◽  
...  
Keyword(s):  
Spectral Index ◽  
Near Infrared ◽  
Crab Nebula ◽  
Dust Emission ◽  
Infrared Emission ◽  
Small Contribution ◽  
Dust Extinction ◽  
Dust Mass ◽  
The Crab Nebula ◽  
Dust Condensation

ABSTRACT We have modelled the near-infrared to radio images of the Crab Nebula with a Bayesian SED model to simultaneously fit its synchrotron, interstellar (IS), and supernova dust emission. We infer an IS dust extinction map with an average AV = 1.08 ± 0.38 mag, consistent with a small contribution (${\lesssim }22{{\ \rm per\ cent}}$) to the Crab’s overall infrared emission. The Crab’s supernova dust mass is estimated to be between 0.032 and 0.049 M⊙ (for amorphous carbon grains) with an average dust temperature Tdust = 41 ± 3 K, corresponding to a dust condensation efficiency of 8–12 ${{\ \rm per\ cent}}$. This revised dust mass is up to an order of magnitude lower than some previous estimates, which can be attributed to our different IS dust corrections, lower SPIRE flux densities, and higher dust temperatures than were used in previous studies. The dust within the Crab is predominantly found in dense filaments south of the pulsar, with an average V-band dust extinction of AV = 0.20–0.39 mag, consistent with recent optical dust extinction studies. The modelled synchrotron power-law spectrum is consistent with a radio spectral index αradio = 0.297 ± 0.009 and an infrared spectral index αIR = 0.429 ± 0.021. We have identified a millimetre excess emission in the Crab’s central regions, and argue that it most likely results from two distinct populations of synchrotron emitting particles. We conclude that the Crab’s efficient dust condensation (8–12 ${{\ \rm per\ cent}}$) provides further evidence for a scenario where supernovae can provide substantial contributions to the IS dust budgets in galaxies.

scholarly journals OISTER optical and near-infrared observations of the super-Chandrasekhar supernova candidate SN 2012dn: Dust emission from the circumstellar shell

2016 ◽  
Vol 68 (5) ◽  
pp. 68 ◽  
Author(s):  
Masayuki Yamanaka ◽  
Keiichi Maeda ◽  
Masaomi Tanaka ◽  
Nozomu Tominaga ◽  
Koji S. Kawabata ◽  
...  
Keyword(s):  
Near Infrared ◽  
Dust Emission ◽  
Infrared Observations ◽  
Circumstellar Shell

scholarly journals Physical and chemical modeling of the starless core L 1512

2020 ◽  
Vol 635 ◽  
pp. A188
Author(s):  
Sheng-Jun Lin ◽  
Laurent Pagani ◽  
Shih-Ping Lai ◽  
Charlène Lefèvre ◽  
François Lique
Keyword(s):  
Near Infrared ◽  
Dust Emission ◽  
Core Formation ◽  
Chemical Modeling ◽  
Infrared Observations ◽  
Peak Density ◽  
Star Forming ◽  
Physical Conditions ◽  
Multiple Line ◽  
Physical And Chemical

Context. The deuterium fractionation in starless cores gives us a clue to estimate their lifetime scales, thus allowing us to distinguish between dynamical theories of core formation. Cores also seem to be subject to a differential N2 and CO depletion, which was not expected from the models. Aims. We aim to create a survey of ten cores to estimate their lifetime scales and depletion profiles in detail. After describing L 183, located in Serpens, we present the second cloud of the series, L 1512, from the star-forming region Auriga. Methods. To constrain the lifetime scale, we performed chemical modeling of the deuteration profiles across L 1512 based on dust extinction measurements from near-infrared observations and nonlocal thermal equilibrium radiative transfer with multiple line observations of N2H+, N2D+, DCO+, C18O, and 13CO, plus H2D+ (110–111). Results. We find a peak density of 1.1 × 105 cm−3 and a central temperature of 7.5 ± 1 K, which are higher and lower, respectively, compared with previous dust emission studies. The depletion factors of N2H+ and N2D+ are 27−13+17 and 4−1+2 in L 1512, which are intermediate between the two other more advanced and denser starless core cases, L 183 and L 1544. These factors also indicate a similar freeze-out of N2 in L 1512, compared to the two others despite a peak density one to two orders of magnitude lower. Retrieving CO and N2 abundance profiles with the chemical model, we find that CO has a depletion factor of ~430–870 and the N2 profile is similar to that of CO unlike that toward L 183. Therefore, L 1512 has probably been living long enough so that N2 chemistry has reached steady state. Conclusions. N2H+ modeling is necessary to assess the precise physical conditions in the center of cold starless cores, rather than dust emission. L 1512 is presumably older than 1.4 Myr. Therefore, the dominating core formation mechanism should be ambipolar diffusion for this source.

scholarly journals Cool white dwarfs as standards for infrared observations

2019 ◽  
Vol 491 (3) ◽  
pp. 3613-3623 ◽  
Author(s):  
Nicola Pietro Gentile Fusillo ◽  
Pier-Emmanuel Tremblay ◽  
Ralph C Bohlin ◽  
Susana E Deustua ◽  
Jason S Kalirai
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Near Infrared ◽  
Hubble Space Telescope ◽  
Pure Hydrogen ◽  
Metal Line ◽  
Infrared Observations ◽  
Photometric Calibration ◽  
Primary Standards ◽  
Cool White Dwarfs

ABSTRACT In the era of modern digital sky surveys, uncertainties in the flux of stellar standards are commonly the dominant systematic error in photometric calibration and can often affect the results of higher level experiments. The Hubble Space Telescope (HST) spectrophotometry, which is based on computed model atmospheres for three hot (Teff$\gt 30\, 000$ K) pure hydrogen (DA) white dwarfs, is currently considered the most reliable and internally consistent flux calibration. However, many next-generation facilities (e.g. Harmoni on E-ELT, Euclid, and JWST) will focus on IR observations, a regime in which white dwarf calibration has not yet been robustly tested. Cool DA white dwarfs have energy distributions that peak close to the optical or near-infrared, do not have shortcomings from UV metal line blanketing, and have a reasonably large sky density (≃4 deg−2 at G &lt; 20), making them, potentially, excellent calibrators. Here, we present a pilot study based on STIS + WFC3 observations of two bright DA white dwarfs to test whether targets cooler than current hot primary standards (Teff$\lt 20\, 000$ K) are consistent with the HST flux scale. We also test the robustness of white dwarf models in the IR regime from an X-shooter analysis of Paschen lines and by cross-matching our previously derived Gaia white dwarf catalogue with observations obtained with 2MASS, UKIDSS, VHS, and WISE.

scholarly journals The Luminosity of the Central Parsec of the Galaxy

1989 ◽  
Vol 136 ◽  
pp. 423-436
Author(s):  
M. W. Werner ◽  
J. A. Davidson
Keyword(s):  
Near Infrared ◽  
Galactic Center ◽  
Thermal Emission ◽  
Large Magellanic Cloud ◽  
Infrared Emission ◽  
Infrared Observations ◽  
The Galaxy ◽  
Infrared Wavelengths ◽  
Central Parsec ◽  
30 Doradus

The luminosity of the central 5 pc of the Galaxy -encompassing the inner regions of the rotating ring of dust and gas which surrounds the galactic center - emerges primarily at infrared wavelengths in the form of thermal emission from heated dust. The nature and location of the sources which heat the dust can be inferred from the spatial and temperature distribution of the thermal infrared emission (λ>20um), from studies of the ionized gas in this region, and from direct imaging in the near infrared. These observations show that the principal heating sources within this 5-pc region are concentrated within the central parsec of the Galaxy and indicate that the luminosity of these sources is within a factor of two of 107 LO. The near-infrared observations of the compact sources at the galactic center do not reveal a single dominant source but suggest instead that the several components of the IRS-16 complex, taken together, may contribute the bulk of the luminosity; however, the data also permit a single object to dominate the energetics of this region. We draw attention to the striking morphological similarities between the galactic center and the innermost regions of the 30 Doradus nebula in the Large Magellanic Cloud and speculate that the luminosity sources in the galactic center may resemble the early-type supergiants in 30 Doradus.

scholarly journals Infrared Emission from AGN

1999 ◽  
Vol 194 ◽  
pp. 25-38
Author(s):  
D. B. Sanders
Keyword(s):  
Near Infrared ◽  
High Redshift ◽  
Dust Emission ◽  
Far Infrared ◽  
Infrared Emission ◽  
Substantial Fraction ◽  
Bolometric Luminosity ◽  
Submillimeter Wavelengths ◽  
Infrared Background ◽  
X Ray Background

Infrared observations of complete samples of active galactic nuclei (AGN) have shown that a substantial fraction of their bolometric luminosity is emitted at wavelengths ˜8–1000μm. In radio-loud and Blazar-like objects much of this emission appears to be direct non-thermal synchrotron radiation. However, in the much larger numbers of radio-quiet AGN it is now clear that thermal dust emission is responsible for the bulk of radiation from the near-infrared through submillimeter wavelengths. Luminous infrared-selected AGN are often surrounded by powerful nuclear starbursts, both of which appear to be fueled by enormous supplies of molecular gas and dust funneled into the nuclear region during the strong interaction/merger of gas rich disks. All-sky surveys in the infrared show that luminous infrared AGN are at least as numerous as optically-selected AGN of comparable bolometric luminosity, suggesting that AGN may spend a substantial fraction of their lifetime in a dust-enshrouded phase. The space density of luminous infrared AGN at high redshift may be sufficient to account for much of the X-Ray background, and for a substantial fraction of the far-infrared background as well. These objects plausibly represent a major epoch in the formation of spheroids and massive black holes (MBH).

scholarly journals Infrared Observations of the Galactic Nucleus

1980 ◽  
Vol 5 ◽  
pp. 163-169 ◽  
Author(s):  
J. H. Lacy
Keyword(s):  
Stellar Population ◽  
Near Infrared ◽  
Line Emission ◽  
Far Infrared ◽  
Infrared Emission ◽  
Ionized Gas ◽  
Infrared Observations ◽  
Cool Stars ◽  
Infrared Sources ◽  
Near Infrared Emission

AbstractInfrared observations of the galactic nucleus and conclusions regarding the nature of the objects present there are reviewed. Observations of three sources of infrared radiation are discussed: near-infrared emission from cool stars, mid- and far-infrared emission from dust, and line emission from ionized gas. These observations provide information about the mass distribution, the stellar population, and the origin and ionization of the compact mid-infrared sources. The possibility of the existence of a massive central black hole is discussed.

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