Evidence for the White Dwarf Nature of Mira B

Sokoloski, J. L.; Bildsten, Lars

doi:10.1088/0004-637x/723/2/1188

Cited by 229 publications

(42 citation statements)

References 60 publications

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“…This model suggests that even if the red giant does not fill its Roche lobe, its wind can and it is therefore focused toward the L1 point of the orbit, further increasing the likelihood of the formation of an accretion disk around the white dwarf. Sokoloski & Bildsten (2010), however, found no evidence that this mechanism is enhancing the accretion rate onto the white dwarf in this binary relative to the rate expected from pure Bondi-Hoyle wind-accretion.…”

Section: Introductionmentioning

confidence: 55%

Symbiotic stars in X-rays

Luna

Sokoloski

Mukai

et al. 2013

A&A

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Until recently, symbiotic binary systems in which a white dwarf accretes from a red giant were thought to be mainly a soft X-ray population. Here we describe the detection with the X-ray Telescope (XRT) on the Swift satellite of nine white dwarf symbiotics that were not previously known to be X-ray sources and one that had previously been detected as a supersoft X-ray source. The nine new X-ray detections were the result of a survey of 41 symbiotic stars, and they increase the number of symbiotic stars known to be X-ray sources by approximately 30%. The Swift/XRT telescope detected all of the new X-ray sources at energies greater than 2 keV. Their X-ray spectra are consistent with thermal emission and fall naturally into three distinct groups. The first group contains those sources with a single, highly absorbed hard component that we identify as probably coming from an accretion-disk boundary layer. The second group is composed of those sources with a single, soft X-ray spectral component that probably originates in a region where low-velocity shocks produce X-ray emission, i.e., a colliding-wind region. The third group consists of those sources with both hard and soft X-ray spectral components. We also find that unlike in the optical, where rapid, stochastic brightness variations from the accretion disk typically are not seen, detectable UV flickering is a common property of symbiotic stars. Supporting our physical interpretation of the two X-ray spectral components, simultaneous Swift UV photometry shows that symbiotic stars with harder X-ray emission tend to have stronger UV flickering, which is usually associated with accretion through a disk. To place these new observations in the context of previous work on X-ray emission from symbiotic stars, we modified and extended the α/β/γ classification scheme for symbiotic-star X-ray spectra that was introduced by Muerset et al. based upon observations with the ROSAT satellite, to include a new δ classification for sources with hard X-ray emission from the innermost accretion region. Because we have identified the elusive accretion component in the emission from a sample of symbiotic stars, our results have implications for the understanding of wind-fed mass transfer in wide binaries, and the accretion rate in one class of candidate progenitors of type Ia supernovae.

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Section: Introductionmentioning

confidence: 55%

Symbiotic stars in X-rays

Luna

Sokoloski

Mukai

et al. 2013

A&A

Self Cite

118

175

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“…Together with Mira B (VZ Ceti), which is possibly a white dwarf (Sokoloski & Bildsten 2010), they form the symbiotic binary system Mira AB. Mira A is the prototype of Mira variables.…”

Section: Introductionmentioning

confidence: 99%

Resolving the extended atmosphere and the inner wind of Mira (oCeti) with long ALMA baselines

Wong

Kamiński

Menten

et al. 2016

A&A

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Context. High angular resolution (sub)millimetre observations of asymptotic giant branch (AGB) stars, now possible with the Atacama Large Millimeter/submillimeter Array (ALMA), allow direct imaging of these objects' photospheres. The physical properties of the molecular material around these regions, which until now has only been studied by imaging of maser emission and spatially unresolved absorption spectroscopy, can be probed with radiative transfer modelling and compared to hydrodynamical model predictions. The prototypical Mira variable, o Cet (Mira), was observed as a Science Verification target in the 2014 ALMA Long Baseline Campaign, offering the first opportunity to study these physical conditions in detail. Aims. With the longest baseline of 15 km, ALMA produces clearly resolved images of the continuum and molecular line emission/absorption at an angular resolution of ∼30 mas at 220 GHz. Models are constructed for Mira's extended atmosphere to investigate the physics and molecular abundances therein. Methods. We imaged the data of 28 SiO = 0, 2 J = 5−4 and H 2 O v 2 = 1 J Ka,Kc = 5 5,0 −6 4,3 transitions and extracted spectra from various lines of sight towards Mira's extended atmosphere. In the course of imaging the emission/absorption, we encountered ambiguities in the resulting images and spectra that appear to be related to the performance of the CLEAN algorithm when applied to a combination of extended emission, and compact emission and absorption. We addressed these issues by a series of tests and simulations. We derived the gas density, kinetic temperature, molecular abundance, and outflow/infall velocities in Mira's extended atmosphere by modelling the SiO and H 2 O lines. Results. We resolve Mira's millimetre continuum emission and our data are consistent with a radio photosphere with a brightness temperature of 2611 ± 51 K. In agreement with recent results obtained with the Very Large Array, we do not confirm the existence of a compact region (<5 mas) of enhanced brightness. Our modelling shows that SiO gas starts to deplete beyond 4 R and at a kinetic temperature of 600 K. The inner dust shells are probably composed of grain types other than pure silicates. During this ALMA observation, Mira's atmosphere generally exhibited infall motion with a shock front of velocity 12 km s −1 outside the radio photosphere. Despite the chaotic nature of Mira's atmosphere, the structures predicted by the hydrodynamical model, codex, can reproduce the observed spectra in astonishing detail, while some other models fail when confronted with the new data. Conclusions. For the first time, millimetre-wavelength molecular absorption against the stellar continuum has been clearly imaged. Combined with radiative transfer modelling, the ALMA data successfully demonstrates the ability to reveal the physical conditions of the extended atmospheres and inner winds of AGB stars in unprecedented detail. Long-term monitoring of oxygen-rich evolved stars will be the key to understanding the unsolved problem of dust ...

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“…It actually belongs to a detached binary system (Mira AB) in which mass transfer by wind interaction is taking place. Sokolski & Bildsten (2010) found evidence pointing towards a white dwarf nature of Mira B, while o Ceti (Mira A) shows clear signs of stellar asymmetry (Karovska et al 1997;Reid & Menten 2007). o Ceti and its companion Mira B are separated by only ∼0.5 ′′ (Karovska et al 1997), corresponding to ∼46 AU.…”

Section: The Authorsmentioning

confidence: 94%

Recurring OH Flares towards o Ceti: I. location and structure of the 1990s’ and 2010s’ events

Etoka

Gérard

Richards

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present the analysis of the onset of the new 2010s' OH flaring event detected in the OH ground-state main line at 1665 MHz towards o Ceti and compare its characteristics with those of the 1990s' flaring event. This is based on a series of complementary single-dish and interferometric observations both in OH and H 2 O obtained with the Nançay Radio telescope (NRT), the Medicina and Effelsberg Telescopes, the European VLBI Network (EVN), and (e)Multi-Element Radio Linked Interferometer Network ((e)MERLIN). We compare the overall characteristics of o Ceti's flaring events with those which have been observed towards other thin-shell Miras, and explore the implication of these events with respect to the standard OH circumstellar-envelope model. The role of binarity in the specific characteristics of o Ceti's flaring events is also investigated. The flaring regions are found to be less than ∼400±40 mas (i.e., ≤ 40 ± 4 AU) either side of o Ceti, with seemingly no preferential location with respect to the direction to the companion Mira B. Contrary to the usual expectation that the OH maser zone is located outside the H 2 O maser zone, the coincidence of the H 2 O and OH maser velocities suggests that both emissions arise at similar distances from the star. The OH flaring characteristics of Mira are similar to those observed in various Mira variables before, supporting the earlier results that the regions where the transient OH maser emission occurs are different from the standard OH maser zone.

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Evidence for the White Dwarf Nature of Mira B

Cited by 229 publications

References 60 publications

Symbiotic stars in X-rays

Symbiotic stars in X-rays

Resolving the extended atmosphere and the inner wind of Mira (oCeti) with long ALMA baselines

Recurring OH Flares towards o Ceti: I. location and structure of the 1990s’ and 2010s’ events

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