Astrophysics in 1997

Trimble, Virginia; McFadden, L. A.

doi:10.1086/316143

Cited by 9 publications

(3 citation statements)

References 830 publications

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“…We concur with Trimble & McFadden (1998) who claim: `A new class of subdwarf B (sdB) stars with p‐mode oscillations. Here is science as it ought to operate!…”

Section: Introductionsupporting

confidence: 83%

The EC 14026 stars -- XII. PG 1219+534, PG 0911+456: successes and new challenges for the Fe driving mechanism

Koen

O’Donoghue

Pollacco

et al. 1999

Monthly Notices of the Royal Astronomical Society

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A B S T R A C TWe report the discovery of short-period oscillations in the sdB stars PG 0911+456 and PG 1219+534, establishing them as members of the EC 14026 stars, a recently discovered class of sdB pulsators. The atmospheric parameters for both stars are also determined. The results are: periods of (148.8, 143.7, 133.5, 128.1 s), T eff 32 800 6 300 K and log g 5:76 6 0:04 for PG 1219+534; and periods of (165.7, 161.5, 155.8 s), T eff 31 900 6 200 K and log g 5:82 6 0:02 for PG 0911+456.The pulsation periods of the 11 well-studied EC 14026 stars are compared with envelope models from the recent work of Charpinet et al. With the exception of PB8783, the longest period in each star is close to the periods of the lowest-order modes in the models. Arguments are given that this is also true for PB8783, involving an increase in its surface gravity over the value derived in an earlier paper.`Correcting' the observed periods for the effects of differing surface gravity from star to star, comparison is made with pulsation models of constant surface gravity and varying effective temperature. Reasonable agreement in the width of the instability strip is demonstrated, as well as properties of its cool boundary. Overall, the class properties of the EC 14026 stars are in impressive agreement with those predicted from models based on the Fe driving mechanism.PG 1219+534 has an atmosphere much richer in He than most sdB stars and all EC 14026 pulsators seen so far. As the Fe driving mechanism operates if suf®cient heavy elements accumulate at the appropriate layer in the stellar envelope, the mechanisms (gravitational settling, radiative levitation, weak stellar winds) that give rise to this must simultaneously be able to provide large differences in the abundance of photospheric He.

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“…We concur with Trimble & McFadden (1998) who claim: `A new class of subdwarf B (sdB) stars with p‐mode oscillations. Here is science as it ought to operate!…”

Section: Introductionsupporting

confidence: 83%

The EC 14026 stars -- XII. PG 1219+534, PG 0911+456: successes and new challenges for the Fe driving mechanism

Koen

O’Donoghue

Pollacco

et al. 1999

Monthly Notices of the Royal Astronomical Society

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“…The question whether pulsars free precess was raised soon after pulsars were identified as rotating neutron stars. However, more than twenty years later most astronomers would agree with Trimble and McFadden's (1998) somewhat humorous reference to our paper suggesting that Earth is the only known free precessing body in the Universe. We believe that pulsar free precession has evaded detection and/or identification for two main reasons.…”

Section: Discussionsupporting

confidence: 64%

Crab pulsar photometry and the signature of free precession

Čadež

Vidrih

Galicic

et al. 2001

A&A

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“…The real value of the Hubble constant has been a hot topic for a long time. In the past few years, some advances have been achieved (for more details, see Aschwanden 1999, Trimble andMcFadden 1998). An exciting result of observation by HST led to H 0 = 80 ± 17kms −1 M pc −1 (Freedman et al 1994).…”

mentioning

confidence: 99%

A Simple Method of Determining the Hubble Constant

Qin

1999

Mod. Phys. Lett. A

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Bidirectional relativistic proper motions of radio components of nearby extragalactic sources give a strong constraint on the determination of the Hubble constant H 0 . Under the assumption that the real velocity of radio components of extragalactic sources is not less than that of Galactic sources, the value of H 0 can be estimated at a high level of accuracy. The assumption is reasonable due to the general belief that the activity in the core of galaxies must be more powerful than that of stars. This method is simple and with only one uncertainty -the real velocity of components. This uncertainty is related to the value of the real velocity of componenets of Galactic sources and the latter is always well-determined (note that the determination is independent of H 0 and the distance of Galactic sources can be directly measured at a rather high level of accuracy). Hopefully the method will play an important role in future research to fix the value of H 0 . With the data of the three sources available so far and the assumption that the real velocity of componenets of at least one of the sources is not less than a known velocity of componenets of a Galactic source, the constant is estimated to be within 27.08kms

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Astrophysics in 1997

Cited by 9 publications

References 830 publications

The EC 14026 stars -- XII. PG 1219+534, PG 0911+456: successes and new challenges for the Fe driving mechanism

The EC 14026 stars -- XII. PG 1219+534, PG 0911+456: successes and new challenges for the Fe driving mechanism

Crab pulsar photometry and the signature of free precession

A Simple Method of Determining the Hubble Constant

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