The re-analysis of theROSATdata of Nova Mus 1983 using white dwarf atmosphere emission models

Abstract. We have numerically evaluated how effective selected potential measures would be for reducing the impact of road dust on ambient air particulate matter (PM10). The selected measures included a reduction of the use of studded tyres on light-duty vehicles and a reduction of the use of salt or sand for traction control. We have evaluated these measures for a street canyon located in central Helsinki for four years (2007–2009 and 2014). Air quality measurements were conducted in the street canyon for two years, 2009 and 2014. Two road dust emission models, NORTRIP (NOn-exhaust Road TRaffic Induced Particle emissions) and FORE (Forecasting Of Road dust Emissions), were applied in combination with the Operational Street Pollution Model (OSPM), a street canyon dispersion model, to compute the street increments of PM10 (i.e. the fraction of PM10 concentration originating from traffic emissions at the street level) within the street canyon. The predicted concentrations were compared with the air quality measurements. Both road dust emission models reproduced the seasonal variability of the PM10 concentrations fairly well but under-predicted the annual mean values. It was found that the largest reductions of concentrations could potentially be achieved by reducing the fraction of vehicles that use studded tyres. For instance, a 30 % decrease in the number of vehicles using studded tyres would result in an average decrease in the non-exhaust street increment of PM10 from 10 % to 22 %, depending on the model used and the year considered. Modelled contributions of traction sand and salt to the annual mean non-exhaust street increment of PM10 ranged from 4 % to 20 % for the traction sand and from 0.1 % to 4 % for the traction salt. The results presented here can be used to support the development of optimal strategies for reducing high springtime particulate matter concentrations originating from road dust.

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Spitzer planet limits around a pulsating white dwarf

Journal of Physics Conference Series ◽

10.1088/1742-6596/172/1/012056 ◽

2009 ◽

Vol 172 ◽

pp. 012056 ◽

Cited By ~ 1

Author(s):

Fergal Mullally

Keyword(s):

White Dwarf

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Optical and Radio Transients after the Collapse of Super-Chandrasekhar White Dwarf Merger Remnants

The Astrophysical Journal ◽

10.3847/2041-8213/aaf960 ◽

2019 ◽

Vol 870 (2) ◽

pp. L23 ◽

Cited By ~ 4

Author(s):

Yun-Wei Yu ◽

Aming Chen ◽

Bo Wang

Keyword(s):

White Dwarf ◽

Radio Transients

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The Crab nebula variability at short time-scales with the Cherenkov telescope array

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3599 ◽

2020 ◽

Vol 501 (1) ◽

pp. 337-346

Author(s):

E Mestre ◽

E de Oña Wilhelmi ◽

D Khangulyan ◽

R Zanin ◽

F Acero ◽

...

Keyword(s):

Gamma Ray ◽

Crab Nebula ◽

Spectral Energy Distribution ◽

Spectral Energy ◽

Telescope Array ◽

Cherenkov Telescopes ◽

Cherenkov Telescope ◽

Emission Models ◽

Short Time ◽

The Crab Nebula

ABSTRACT Since 2009, several rapid and bright flares have been observed at high energies (>100 MeV) from the direction of the Crab nebula. Several hypotheses have been put forward to explain this phenomenon, but the origin is still unclear. The detection of counterparts at higher energies with the next generation of Cherenkov telescopes will be determinant to constrain the underlying emission mechanisms. We aim at studying the capability of the Cherenkov Telescope Array (CTA) to explore the physics behind the flares, by performing simulations of the Crab nebula spectral energy distribution, both in flaring and steady state, for different parameters related to the physical conditions in the nebula. In particular, we explore the data recorded by Fermi during two particular flares that occurred in 2011 and 2013. The expected GeV and TeV gamma-ray emission is derived using different radiation models. The resulting emission is convoluted with the CTA response and tested for detection, obtaining an exclusion region for the space of parameters that rule the different flare emission models. Our simulations show different scenarios that may be favourable for achieving the detection of the flares in Crab with CTA, in different regimes of energy. In particular, we find that observations with low sub-100 GeV energy threshold telescopes could provide the most model-constraining results.

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WD 1856 b: a close giant planet around a white dwarf that could have survived a common envelope phase

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3703 ◽

2020 ◽

Vol 501 (1) ◽

pp. 676-682

Author(s):

F Lagos ◽

M R Schreiber ◽

M Zorotovic ◽

B T Gänsicke ◽

M P Ronco ◽

...

Keyword(s):

White Dwarf ◽

Evolutionary History ◽

Giant Planet ◽

Asymptotic Giant Branch ◽

Orbital Energy ◽

Current Position ◽

Recombination Energy ◽

Additional Energy ◽

Common Envelope ◽

History Of

ABSTRACT The discovery of a giant planet candidate orbiting the white dwarf WD 1856+534 with an orbital period of 1.4 d poses the questions of how the planet reached its current position. We here reconstruct the evolutionary history of the system assuming common envelope evolution as the main mechanism that brought the planet to its current position. We find that common envelope evolution can explain the present configuration if it was initiated when the host star was on the asymptotic giant branch, the separation of the planet at the onset of mass transfer was in the range 1.69–2.35 au, and if in addition to the orbital energy of the surviving planet either recombination energy stored in the envelope or another source of additional energy contributed to expelling the envelope. We also discuss the evolution of the planet prior to and following common envelope evolution. Finally, we find that if the system formed through common envelope evolution, its total age is in agreement with its membership to the Galactic thin disc. We therefore conclude that common envelope evolution is at least as likely as alternative formation scenarios previously suggested such as planet–planet scattering or Kozai–Lidov oscillations.

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Mass transfer in double white dwarf binaries

New Astronomy Reviews ◽

10.1016/j.newar.2008.03.019 ◽

2008 ◽

Vol 51 (10-12) ◽

pp. 878-883 ◽

Cited By ~ 2

Author(s):

Juhan Frank

Keyword(s):

Mass Transfer ◽

White Dwarf

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