Optical observations of ultraviolet objects - II. Classification and photometry (l = 0 to 145 )

Dworetsky, M. M.; Whitelock, P. A.; Carnochan, D. J.

doi:10.1093/mnras/201.4.901

Cited by 23 publications

(17 citation statements)

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“…The XMM-Newton data also showed a periodicity at 19.2 s (with a statistical significance of 3.2σ) pointing to the pres-E-mail: sandro@iasf-milano.inaf.it ence of a compact companion. However, no evidence for a binary nature had been reported in the literature (Faÿ et al 1973;Kaufmann & Theil 1980;Dworetsky et al 1982) and a recent campaign of high-resolution optical spectroscopy did not reveal radial velocity variations (Heber et al 2014). This means that either the orbital plane has a very small inclination and/or the orbital period is of the order of months, or that BD +37 • 442 is indeed a single star and the reported signal was spurious.…”

Section: Introductionmentioning

confidence: 99%

The lack of X-ray pulsations in the extreme helium star BD+37°442 and its possible stellar wind X-ray emission

Mereghetti

Palombara

Tiengo

et al. 2016

Mon. Not. R. Astron. Soc.

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We report the results of a new XMM-Newton observation of the helium-rich hot subdwarf BD +37 • 442 carried out in February 2016. The possible periodicity at 19 s seen in a 2011 shorter observation is not confirmed, thus dismissing the evidence for a binary nature. This implies that the observed soft X-ray emission, with a luminosity of a few 10 31 erg s −1 , originates in BD +37 • 442 itself, rather than in an accreting neutron star companion. The X-ray spectrum is well fit by thermal plasma emission with a temperature of 0.22 keV and nonsolar element abundances. Besides the overabundance of He, C and N already known from optical/UV studies, the X-ray spectra indicate also a significant excess of Ne. The soft X-ray spectrum and the ratio of X-ray to bolometric luminosity, L X /L BOL ∼ 2 × 10 −7 , are similar to those observed in massive early type stars. This indicates that the mechanisms responsible for plasma shock-heating can work also in the weak stellar winds (mass loss ratesṀ W 10 −8 M yr −1 ) of low-mass hot stars.

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Section: Introductionmentioning

confidence: 99%

The lack of X-ray pulsations in the extreme helium star BD+37°442 and its possible stellar wind X-ray emission

Mereghetti

Palombara

Tiengo

et al. 2016

Mon. Not. R. Astron. Soc.

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“…The high-ionization absorptionline measurement methods are discussed in°4. A brief Blaauw & van Albada 1963 ;(16) Savage et al 1985 ;(17) Karlsson 1969 ;(18) Houk 1982 ;(19) Garrison et al 1977 ;(20) McConnell & Bidelman 1976 ;(21) Thackeray & Andrews 1974 ;(22) Ryans et al 1997a ;(23) Roberts 1962 ;(24) Walborn, Fitzpatrick, & Nichols-Bohlin 1990 ;(25) Ryans et al 1997b ;(26) Conti et al 1983 ;(27) Walborn 1982 ;(28) Schild 1970 ;(29) Hill, Kilkenny, & van Breda 1974 ;(30) Hiltner, Garrison, & Schild 1969 ;(31) Little et al 1995 ;(32) Dworetsky, Whitelock, & Carnochan 1982 ;(33) Balona 1975 ;(34) Thackeray, Tritton, & Walker 1973 ;(35) Conlon et al 1988 ;(36) Schild, Hiltner, & Sanduleak 1969 ;(37) Balona 1992 ;(38) Sembach, Savage, & Massa 1991 ;(39) Savage, Sembach, & Massa 1990 ;(40) Walker 1957 ;(41) Tripp et al 1993 ;(42) Kendall et al 1994 ;(43) Hiltner 1951 ;…”

Section: Introductionmentioning

confidence: 99%

“…b References for B and V measurements : (1) Deutschmann et al 1976 ; ( Johnson & Morgan 1953 ;(8) Nicolet 1978 ;(9) Lutz 1971 ;(10) Sharpless 1962 ;(11) Walker 1969 ;(12) Vogt 1976 ;(13) Hill & Lynas-Gray 1977 ;(14) Johnson et al 1966 ;(15) Walker 1956 ;(16) Oja 1985 ;(17) Schild et al 1983 ;(18) Landolt 1983 ;(19) Thackeray & Andrews 1974 ;(20) Klemola 1962 ;(21) Feinstein 1964 ;(22) Feinstein, Marraco, & Muzzio 1973 ;(23) Massey & Johnson 1993 ;(24) Guetter 1974 ;(25) Humphreys 1973 ;(26) Kilkenny 1974 ;(27) Lynga & Wramdemark 1973 ;(28) Kilkenny et al 1985 ;(29) Hill et al 1974 ;(30) Crawford, Golson, & Landolt 1971 ;(31) GutierrezMoreno & Moreno 1968 ;(32) Fernie 1983 ;(33) Dworetsky et al 1982 ;(34) Cousins & Stoy 1962 ;(35) Penston 1973 ;(36) Schild et al 1969 ;(37) Feinstein & Ferrer 1968 ;(38) Crampton 1971 ;…”

Section: Introductionmentioning

confidence: 99%

IUE Absorption‐Line Observations of the Moderately and Highly Ionized Interstellar Medium toward 164 Early‐Type Stars

Savage

Meade

Sembach

2001

ASTROPHYS J SUPPL S

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We present measurements of Galactic interstellar Al III, Si IV, and C IV absorption recorded in highresolution archival ultraviolet spectra of 164 hot early-type stars observed by the International Ultraviolet Explorer (IUE) satellite. The objects studied were drawn from the list of hot stars scheduled to be observed with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite as part of observing programs designed to investigate absorption by O VI in the Galactic disk and halo. Multiple IUE echelle-mode integrations have been combined to produce a single ultraviolet (1150È1900 spectrum of each star A ) with a spectral resolution of D25 km s~1 (FWHM). Selected absorption-line proÐles are presented for each star along with plots of the apparent column density per unit velocity for each line of the Al III, Si IV, and C IV doublets. We report absorption-line equivalent widths, absorption velocities, and integrated column densities based on the apparent optical depth method of examining interstellar absorption lines. We also determine column densities and Doppler parameters from single-component curve-ofgrowth analyses. The scientiÐc analysis of these observations will be undertaken after the FUSE satellite produces similar measurements for absorption by interstellar O IV, Fe III, S III, and other ions.

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“…Its temperature, luminosity, surface gravity, and mass-loss properties are very similar to those of HD 49798. Contrary to this star, however, for BD +37 ∘ 442 there was no evidence for a binary companion (Fay et al 1973;Kaufmann & Theil 1980;Dworetsky et al 1982); also recently high-resolution spectroscopical observations did not reveal any radial velocity variations ). In 2011 we observed this star with XMM-Newton and detected a soft X-ray emission.…”

Section: New Results On Hd 49798: Pulsar Spin-up and Intrinsic X-ray mentioning

confidence: 55%

News on the X-ray emission from hot subdwarf stars

Palombara

Mereghetti

2017

Open Astronomy

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Abstract:In latest years, the high sensitivity of the instruments on-board the XMM-Newton and Chandra satellites allowed us to explore the properties of the X-ray emission from hot subdwarf stars. The small but growing sample of X-ray detected hot subdwarfs includes binary systems, in which the X-ray emission is due to wind accretion onto a compact companion (white dwarf or neutron star), as well as isolated sdO stars, in which X-rays are probably due to shock instabilities in the wind. X-ray observations of these low-mass stars provide information which can be useful for our understanding of the weak winds of this type of stars and can lead to the discovery of particularly interesting binary systems. Here we report the most recent results we have recently obtained in this research area.

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Optical observations of ultraviolet objects - II. Classification and photometry (l = 0 to 145 )

Cited by 23 publications

References 0 publications

The lack of X-ray pulsations in the extreme helium star BD+37°442 and its possible stellar wind X-ray emission

The lack of X-ray pulsations in the extreme helium star BD+37°442 and its possible stellar wind X-ray emission

IUE Absorption‐Line Observations of the Moderately and Highly Ionized Interstellar Medium toward 164 Early‐Type Stars

News on the X-ray emission from hot subdwarf stars

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