The 100 pc White Dwarf Sample in the SDSS Footprint

Kilic, Mukremin; Bergeron, P.; Kosakowski, Alekzander; Brown, Warren R.; Agüeros, Marcel A.; Blouin, Simon

doi:10.3847/1538-4357/ab9b8d

Cited by 136 publications

(163 citation statements)

References 65 publications

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“…By analysing the phase-resolved spectra (Extended Data All WDs B >100 MG 2 MG < B <100 MG B <2 MG ZTF J1901+1458 Figure 1: Gaia CMD. Gaia color-magnitude diagram for the white dwarfs that are within 100 pc from Earth and within the SDSS footprint 22 . Solid lines show theoretical cooling tracks for white dwarfs with masses between 0.6 M (top) and 1.28 M (bottom), equally spaced in mass; the atmosphere is assumed to be hydrogen-dominated 23 and the interior composition to be carbonoxygen 24 for M < 1.1 M and oxygen-neon 25 for M > 1.1 M .…”

Section: Israelmentioning

confidence: 99%

A highly magnetized and rapidly rotating white dwarf as small as the Moon

Caiazzo

Burdge

Fuller

et al. 2021

Nature

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in binaries [1][2][3] . If the orbital period of the binary is short enough, energy losses from gravitational wave radiation can shrink the orbit until the two white dwarfs come into contact and merge 4 . Depending on the masses of the coalescing white dwarfs, the merger can lead to a supernova of type Ia, or it can give birth to a massive white dwarf 5 . In the latter case, the white dwarf remnant is expected to be highly magnetised 6,7 due to the strong dynamo that may arise during the merger, and rapidly rotating due to conservation of the orbital angular momentum of the binary 8 . Here we report the discovery of a white dwarf, ZTF J190132.9+145808.7, which presents all these properties, but to an extreme: a rotation period of 6.94 minutes, one of the shortest measured for an isolated white dwarf 9, 10 , a magnetic field ranging between 600 MG and 900 MG over its surface, one of the highest fields ever detected on a white dwarf 11 , and a stellar radius of 1810 km, slightly larger than the radius of the Moon. Such a small radius implies the star's mass is the closest ever detected to the white dwarf maximum mass, or Chandrasekhar mass 12 . In fact, as the white dwarf cools and its composition stratifies, it may become unstable and collapse due to electron capture, exploding into a thermonuclear supernova or collapsing into a neutron star. Neutron stars born in this fashion could account for ∼10% of their total population.The Zwicky Transient Facility [13][14][15] (ZTF) is a synoptic optical survey that uses the 48-inch Samuel Oschin Telescope of the Palomar Observatory to image the Northern sky on a regular basis.We discovered ZTF J190132.9+145808.7 (hereafter ZTF J1901+1458) during a search for fast variability in massive white dwarfs. To this end, we selected objects in a white dwarf catalogue 16 that lie below the main white dwarf cooling sequence in the Gaia 17 color-magnitude diagram (CMD,

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Section: Israelmentioning

confidence: 99%

A highly magnetized and rapidly rotating white dwarf as small as the Moon

Caiazzo

Burdge

Fuller

et al. 2021

Nature

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“…(1) the crystallization bump is predicted to start too early and (2) the amplitude of the pile-up is significantly underestimated (see also Kilic et al 2020). These problems are a source of concern for the use of white dwarfs as cosmochronometers (Winget et al 1987;Oswalt et al 1996;Fontaine et al 2001;Kalirai 2012;Hansen et al 2013;Tremblay et al 2014;Kilic et al 2017;Isern 2019;Fantin et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Toward precision cosmochronology

Blouin

Daligault

Saumon

et al. 2020

A&A

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The continuous cooling of a white dwarf is punctuated by events that affect its cooling rate. The most significant of these events is the crystallization of its core, a phase transition that occurs once the C/O interior has cooled down below a critical temperature. This transition releases latent heat, as well as gravitational energy due to the redistribution of the C and O ions during solidification, thereby slowing down the evolution of the white dwarf. The unambiguous observational signature of core crystallization–a pile-up of objects in the cooling sequence–was recently reported. However, existing evolution models struggle to quantitatively reproduce this signature, casting doubt on their accuracy when used to measure the ages of stellar populations. The timing and amount of the energy released during crystallization depend on the exact form of the C/O phase diagram. Using the advanced Gibbs–Duhem integration method and state-of-the-art Monte Carlo simulations of the solid and liquid phases, we obtained a very accurate version of this phase diagram that allows a precise modeling of the phase transition. Despite this improvement, the magnitude of the crystallization pile-up remains underestimated by current evolution models. We conclude that latent heat release and O sedimentation alone are not sufficient to explain the observations, and that other unaccounted physical mechanisms, possibly 22Ne phase separation, play an important role.

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“…2), and the WD masses from the fitting relation 𝑀 wd = (0.796 ± 0.008) + 0.383𝑀 Ni (Kushnir et al 2020) which assumes pure detonations, in agreement with Steigerwald & Tejeda (2021). Once we have the SN Ia explosion masses, we determine the PBH mass scale according to Steigerwald & Tejeda (2021) assuming the WD mass function of Kilic et al (2020). As conservative assumptions, we adopt the detonability parameter 𝛼 = 1 (see Steigerwald & Tejeda 2021) and detonation speed 𝑣 CJ at nuclear-statistical equilibrium (NSE, Gamezo et al 1999).…”

Section: Discussionmentioning

confidence: 91%

Type Ia Supernova Magnitude Step from the local Dark Matter Environment

Steigerwald,

Rodrigues,

Profumo

et al. 2021

Preprint

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Residuals in the Hubble diagram at optical wavelengths and host galaxy stellar mass are observed to correlate in Type Ia supernovae (SNe Ia) ('magnitude step'). Among possible progenitor channels for the associated explosions, those based on dark matter (DM) have attracted significant attention, including our recent proposal that 'normal' SNe Ia from bare detonations in sub-Chandrasekhar white dwarf stars are triggered by the passage of asteroid-mass primordial black holes (PBHs): the magnitude step could then originate from a brightness dependence on stellar properties, on DM properties, or both. Here, we present a method to estimate the local DM density and velocity dispersion of the environment of SN Ia progenitors. We find a luminosity step of 0.52 ± 0.11 mag corresponding to bins of high vs low DM density in a sample of 222 low-redshift events from the Open Supernova Catalog. We investigate whether the magnitude step can be attributed to local DM properties alone, assuming asteroid-mass PBHs. Given the inverse correlation between SN Ia brightness and PBH mass, an intriguing explanation is a spatially-inhomogeneous PBH mass function. If so, a strong mass segregation in the DM density-dependent PBH mass scale is needed to explain the magnitude step. While mass segregation is observed in dense clusters, it is unlikely to be realized on galactic scales. Therefore, if DM consists of asteroid-mass PBHs, the magnitude step is more likely to exist, and dominantly to be attributed to local stellar properties.

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The 100 pc White Dwarf Sample in the SDSS Footprint

Cited by 136 publications

References 65 publications

A highly magnetized and rapidly rotating white dwarf as small as the Moon

A highly magnetized and rapidly rotating white dwarf as small as the Moon

Toward precision cosmochronology

Type Ia Supernova Magnitude Step from the local Dark Matter Environment

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