Normal Stars

Drilling, J. S.; Landolt, A. U.

doi:10.1007/978-1-4612-1186-0_15

Cited by 159 publications

(237 citation statements)

References 19 publications

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“…(1) Dreizler et al (1990); (2) luminosity classes I-V to be significantly different from those given for "normal" stars by Drilling and Landolt (1999), even though the stars in the present paper probably have much lower masses and luminosities.…”

Section: Calibrationscontrasting

confidence: 61%

An MK-like system of spectral classification for hot subdwarfs

Drilling

Jeffery

Heber

et al. 2013

A&A

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An MK (Morgan-Keenan)-like system of spectral classification for hot subdwarfs is presented. We find that a three-dimensional spectral type, consisting of a "spectral" class, a "luminosity" class, and a "helium" class, is necessary to classify the sdO (subdwarf O) and sdB (subdwarf B) stars. In addition, the helium-strong stars appear to form two parallel spectral sequences: one showing strong lines of CII, CIII, or CIV, and the other with these same lines weak or absent. We also give a preliminary calibration of the new spectral types in terms of effective temperature, surface gravity, and surface helium-to-hydrogen abundance ratio, and show the relation between the new spectral types and the natural groups defined by the Palomar-Green (PG) survey.

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Section: Calibrationscontrasting

confidence: 61%

An MK-like system of spectral classification for hot subdwarfs

Drilling

Jeffery

Heber

et al. 2013

A&A

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“…The extinction in the K s band can be estimated as A Ks = 0.062 × A V ∼ 2.6 mag (Nishiyama et al 2008). Using the tables of Drilling & Landolt (2000) and Tokunaga (2000) suggests that the survey of Mauerhan et al (2009) should have enabled the detection of an O/B supergiant (K s ∼ 11 mag), as well as a main sequence star with spectral type earlier than B3V. Since most known HMXBs have donor stars with spectral types from O9V-B2V (Negueruela 1998), XMM J174457-2850.3 is not likely to be an HMXB unless the source is more distant than 8 kpc.…”

Section: Xmm J174457-28503: a Wind-fed System?mentioning

confidence: 99%

“…All of these systems show both long-and short-term X-ray variability and are characterized by 2-10 keV luminosities ranging between ∼10 32−35 erg s −1 , although one object shows more intense X-ray emission of L X ∼ 10 36−37 erg s −1 (e.g., Masetti et al 2007). However, for the extinction towards XMM J174457-2850.3 and a distance of 8 kpc, an M-type giant would have a magnitude of K s ∼ 11−13 mag (Drilling & Landolt 2000;Tokunaga 2000). The lack of a counterpart with K s < ∼ 15.6 mag (Mauerhan et al 2009) therefore renders this scenario unlikely as well unless the source is located at a larger distance than 8 kpc.…”

Section: Xmm J174457-28503: a Wind-fed System?mentioning

confidence: 99%

A four-year baselineSwiftstudy of enigmatic X-ray transients located near the Galactic center

Degenaar

Wijnands

2010

A&A

108

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We report on continued monitoring observations of the Galactic center carried out by the X-ray telescope aboard the Swift satellite in 2008 and 2009. This campaign revealed activity of the five known X-ray transients AX J1745.6-2901, CXOGC J174535.5-290124, GRS 1741-2853, XMM J174457-2850.3 and CXOGC J174538.0-290022. All these sources are known to undergo very faint X-ray outbursts with 2-10 keV peak luminosities of L X,peak ∼ 10 34−36 erg s −1 , although the two confirmed neutron star low-mass X-ray binaries AX J1745.6-2901 and GRS 1741-2853 can also become brighter (L X,peak ∼ 10 36−37 erg s −1 ). We discuss the observed longterm lightcurves and X-ray spectra of these five enigmatic transients. In 2008, AX J1745.6-2901 returned to quiescence following an unusually long accretion outburst of more than 1.5 years. GRS 1741-2853 was active in 2009 and displayed the brightest outburst ever recorded for this source, reaching up to a 2-10 keV luminosity of L X ∼ 1 × 10 37 (D/7.2 kpc) 2 erg s −1 . This system appears to undergo recurrent accretion outbursts approximately every 2 years. Furthermore, we find that the unclassified transient XMM J174457-2850.3 becomes bright only during short episodes (days) and is often found active in between quiescence (L X ∼ 10 32 erg s −1 ) and its maximum outburst luminosity of L X ∼ 10 36 erg s −1 . CXOGC J174535.5-290124 and CXOGC J174538.0-290022, as well as three other veryfaint X-ray transients that were detected by Swift monitoring observations in 2006, have very low time-averaged mass-accretion rates of Ṁ long < ∼ 2 × 10 −12 M yr −1 . Despite having obtained two years of new data in 2008 and 2009, no new X-ray transients were detected.

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“…They adopted T e = 6600 K, and log(g) = 4.2, very close to recent tabulations for mid-F dwarfs (cf. Drilling & Landolt 1999). The authors of P1 were aware of the unusual nature of the Balmer lines in HD 101065, but had no solution to the riddle of the sharp cores of Hα and Hβ.…”

Section: Introductionmentioning

confidence: 99%

The core-wing anomaly of cool Ap stars

Cowley

Hubrig²,

Ryabchikova³

et al. 2001

A&A

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Abstract. The profiles of Hα in a number of cool Ap stars are anomalous. Broad wings, indicative of temperatures in the range 7000-8000 K end abruptly in narrow cores. The widths of these cores are compatible with those of dwarfs with temperatures of 6000 K or lower. This profile has been known for Przybylski's star, but it is seen in other cool Ap stars. The Hβ profile in several of these stars shows a similar core-wing anomaly (CWA). In Przybylski's star, the CWA is probably present at higher Balmer members. We are unable to account for these profiles within the context of LTE and normal dwarf atmospheres. We conclude that the atmospheres of these stars are not "normal". This is contrary to a notion that has long been held.

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Normal Stars

Cited by 159 publications

References 19 publications

An MK-like system of spectral classification for hot subdwarfs

An MK-like system of spectral classification for hot subdwarfs

A four-year baselineSwiftstudy of enigmatic X-ray transients located near the Galactic center

The core-wing anomaly of cool Ap stars

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