Fundamental parameters and infrared excesses of Tycho–Gaia stars

McDonald, Iain; Zijlstra, A. A.; Watson, R. A.

doi:10.1093/mnras/stx1433

Cited by 108 publications

(93 citation statements)

References 126 publications

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“…On the other hand, T eff and log 10 g of the stars providing the bestfitting templates are ≈ 4500 ± 50 K, ≈3.0 in HD 175545 (Koleva & Vazdekis 2012;McDonald, Zijlstra & Watson 2017) and ≈ 4900 ± 50 K, ≈3.4 in HD 165438 (Prugniel, Vauglin & Koleva 2011;Jones et al 2011;Reffert et al 2015;Luck 2017), respectively. Those values of log 10 g are significantly closer to the range of ≈3.4-3.6 of the possible models (Section 3).…”

Section: Model-independent Constraintsmentioning

confidence: 95%

The X-ray binary GX 339–4/V821 Ara: the distance, inclination, evolutionary status, and mass transfer

Zdziarski

Ziółkowski

Mikołajewska

2019

Monthly Notices of the Royal Astronomical Society

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We consider constraints on the distance, inclination and component masses in the X-ray binary GX 339-4 resulting from published works, and then construct detailed evolutionary models for the donor. From both considerations, and assuming the black-hole nature for the compact object (i.e., its mass > 3M ), the possible donor mass is ≈0.5-1.4M , the inclination is ≈ 40 • -60 • and the distance is ≈8-12 kpc. The corresponding mass of the compact object is ≈4-11M . We then confirm a previous estimate that the theoretical conservative mass transfer rate in GX 339-4 is 10 −9 M yr −1 . This is 10 times lower than the average mass accretion rate estimated from the long-term X-ray light curve. We show that this discrepancy can be solved in two ways. One solution invokes irradiation of the donor by X-rays from accretion, which can temporarily enhance the mass transfer rate. We found that absorption of a ∼1 per cent of the irradiating luminosity results in the transfer rate equal to the accretion rate. The time scale at which the transfer rate will vary is estimated to be ∼10 yr, which appears consistent with the observations. The other solution invokes non-conservative mass transfer. This requires that ≈70 per cent of the transferred mass escapes as a strong outflow and carries away the specific angular momentum comparable to that of the donor.

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Section: Model-independent Constraintsmentioning

confidence: 95%

The X-ray binary GX 339–4/V821 Ara: the distance, inclination, evolutionary status, and mass transfer

Zdziarski

Ziółkowski

Mikołajewska

2019

Monthly Notices of the Royal Astronomical Society

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“…Figure 2 shows SEDs of two examples from our debris disk candidates. HD 65372 and HD 99022 are newly confirmed as debris disks, although they have been reported as mid-infrared excess candidates (McDonald et al, 2012). Table 1 summarizes the number of sample stars, the number of debris disks, and σ for samples A and B.…”

Section: Resultsmentioning

confidence: 99%

Search for Debris Disks by Akari and Irsf

Takeuchi¹,

Ishihara²,

Kaneda³

et al. 2017

Publications of The Korean Astronomical Society

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Debris disks are important observational clues to understanding on-going planetary system formation. They are usually identified by significant mid-infrared excess on top of the photospheric emission of a central star on the basis of prediction from J-, H-, and Ks-band fluxes and the stellar model spectra. For bright stars, 2MASS near-infrared fluxes suffer large uncertainties due to the near-infrared camera saturation. Therefore we have performed follow-up observations with the IRSF 1.4 m near-infrared telescope located in South Africa to obtain accurate J-, H-, and Ks-band fluxes of the central stars. Among 754 main-sequence stars which are detected in the AKARI 18 µm band, we have performed photometry for 325 stars with IRSF. As a result, we have successfully improved the flux accuracy of the central stars from 9.2 % to 0.5 % on average. Using this dataset, we have detected 18 µm excess emission from 57 stars in our samples with a 3σ level. We find that some of them have high ratios of the excess to the photospheric emission even around very old stars, which cannot be explained by the current planet-formation theories.

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“…Several stars were observed by more than one satellite. However, in this work we only show results from the data set with the McDonald et al (2017). For our target stars the uncertainties are typically ±125 K for the effective temperature and 5-10% for the luminosity.…”

Section: The Target Samplementioning

confidence: 99%

Stellar masses from granulation and oscillations of 23 bright red giants observed by BRITE-Constellation

Kallinger

Beck

Hekker

et al. 2019

A&A

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Context. The study of stellar structure and evolution depends crucially on accurate stellar parameters. The photometry from space telescopes has provided superb data that allowed asteroseismic characterisation of thousands of stars. However, typical targets of space telescopes are rather faint and complementary measurements are difficult to obtain. On the other hand, the brightest, otherwise well-studied stars, are lacking seismic characterization. Aims. Our goal is to use the granulation and/or oscillation time scales measured from photometric time series of bright red giants (1.6 ≤ V mag ≤ 5.3) observed with BRITE -Constellation to determine stellar surface gravities and masses. Methods. We use probabilistic methods to characterize the granulation and/or oscillation signal in the power density spectra and the autocorrelation function of the BRITE -Constellation time series. Results. We detect a clear granulation and/or oscillation signal in 23 red giant stars and extract the corresponding time scales from the power density spectra as well as the autocorrelation function of the BRITE -Constellation time series. To account for the recently discovered non-linearity of the classical seismic scaling relations, we use parameters from a large sample of Kepler stars to re-calibrate the scalings of the high-and low-frequency components of the granulation signal. We develop a method to identify which component is measured if only one granulation component is statistically significant in the data. We then use the new scalings to determine the surface gravity of our sample stars, finding them to be consistent with those determined from the autocorrelation signal of the time series. We further use radius estimates from the literature to determine the stellar masses of our sample stars from the measured surface gravities. We also define a statistical measure for the evolutionary stage of the stars. Conclusions. Our sample of stars covers low-mass stars on the lower giant branch to evolved massive supergiants and even though we can not verify our mass estimates with independent measurements from the literature they appear to be at least good enough to seperate high-mass from low-mass stars. Given the large known but usually not considered systematic uncertainties in the previous model-based mass estimates, we prefer our model-independent measurements.

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Fundamental parameters and infrared excesses of Tycho–Gaia stars

Cited by 108 publications

References 126 publications

The X-ray binary GX 339–4/V821 Ara: the distance, inclination, evolutionary status, and mass transfer

The X-ray binary GX 339–4/V821 Ara: the distance, inclination, evolutionary status, and mass transfer

Search for Debris Disks by Akari and Irsf

Stellar masses from granulation and oscillations of 23 bright red giants observed by BRITE-Constellation

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