The Nature of the Hard X‐Ray–Emitting Symbiotic Star RT Cru

Luna, G. J. M.; Sokoloski, J. L.

doi:10.1086/522576

Cited by 50 publications

(97 citation statements)

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“…When we used the average BAT spectrum instead, again with the average XRT spectrum, the results were similar except that the cross-normalization factor was ∼2, and the parameter values had larger errors. While better data are necessary for a definitive fit, these results are consistent with those on wellstudied δ-type symbiotic stars (see, e.g., Luna & Sokoloski 2007;Smith et al 2008). …”

Section: X-ray Spectrumsupporting

confidence: 80%

SU Lyncis, a hard X-ray bright M giant: clues point to a large hidden population of symbiotic stars

Mukai

Luna

Cusumano

et al. 2016

Monthly Notices of the Royal Astronomical Society: Letters

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110

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Symbiotic star surveys have traditionally relied almost exclusively on low resolution optical spectroscopy. However, we can obtain a more reliable estimate of their total Galactic population by using all available signatures of the symbiotic phenomenon. Here we report the discovery of a hard X-ray source, 4PBC J0642.9+5528, in the Swift hard X-ray all-sky survey, and identify it with a poorly studied red giant, SU Lyn, using pointed Swift observations and ground-based optical spectroscopy. The X-ray spectrum, the optical to UV spectrum, and the rapid UV variability of SU Lyn are all consistent with our interpretation that it is a symbiotic star containing an accreting white dwarf. The symbiotic nature of SU Lyn went unnoticed until now, because it does not exhibit emission lines strong enough to be obvious in low resolution spectra. We argue that symbiotic stars without shell-burning have weak emission lines, and that the current lists of symbiotic stars are biased in favor of shell-burning systems. We conclude that the true population of symbiotic stars has been underestimated, potentially by a large factor.

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Section: X-ray Spectrumsupporting

confidence: 80%

SU Lyncis, a hard X-ray bright M giant: clues point to a large hidden population of symbiotic stars

Mukai

Luna

Cusumano

et al. 2016

Monthly Notices of the Royal Astronomical Society: Letters

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110

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“…The temperature inferred from a single-temperature fit will be lower than k T max . The plasma temperatures from single temperature fits to boundary layer emission in Kennea et al (2009) from RT Cru, T CrB, CH Cyg, and SS73 17 are lower than the maximum temperatures determined from cooling flow fits in RT Cru (Luna & Sokoloski 2007), T CrB (Luna et al 2008), and SS73 17 (Eze et al 2010). The higher absorbing column in front of the hard component is consistent with this component being closer to the central engine than the lower temperature plasma.…”

Section: Discussionmentioning

confidence: 76%

“…In contrast, almost all symbiotic stars detected in X-rays show spectra absorbed by columns densities of a few times 10 21 -10 23 cm 2 (e.g., Luna & Sokoloski 2007;Kennea et al 2009). …”

Section: Discussionmentioning

confidence: 99%

DETECTION OF X-RAYS FROM THE SYMBIOTIC STAR V1329 Cyg

Stute¹,

Luna²,

Sokoloski³

2011

ApJ

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We report the detection of X-ray emission from the symbiotic star V1329 Cyg with XMM-Newton. The spectrum from the EPIC pn, MOS1, and MOS2 instruments consists of a two-temperature plasma with k T 1 = 0.11 +0.02 −0.02 keV and k T 2 = 0.93 +0.12 −0.14 keV. Unlike the vast majority of symbiotic stars detected in X-rays, the soft component of the spectrum seems to be absorbed only by interstellar material. The shock velocities corresponding to the observed temperatures are about 300 km s −1 and about 900 km s −1 . We did not find either periodic or aperiodic X-ray variability, with upper limits on the amplitudes of such variations being 46% and 16% (rms), respectively. We also did not find any ultraviolet variability with an rms amplitude of more than approximately 1%. The derived velocities and the unabsorbed nature of the soft component of the X-ray spectrum suggest that some portion of the high energy emission could originate in shocks within a jet and beyond the symbiotic nebula. The lower velocity is consistent with the expansion velocity of the extended structure present in Hubble Space Telescope observations. The higher velocity could be associated with an internal shock at the base of the jet or with shocks in the accretion region.

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“…Mauche et al (1995); Baskill et al (2005)) confirm these predictions. Accretion onto white dwarfs in some symbiotics presents similar soft X-ray emissions (Luna & Sokoloski 2007;Luna et al 2008;Kennea et al 2009) because of the large mass accretion rates in these systems. At low mass accretion rate (or during dwarf nova quiescence), as the density is much decreased, the BL becomes optically thin and emits in the hard X-ray band with T ≈ 10 8 K (Narayan & Popham 1993) (see below for observational evidence of such optically thin BLs).…”

Section: The Boundary Layermentioning

confidence: 94%

XMM-NEWTONOBSERVATIONS OF THE DWARF NOVA RU Peg IN QUIESCENCE: PROBE OF THE BOUNDARY LAYER

Balman

Godon

Sion

et al. 2011

ApJ

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We present an analysis of X-ray and UV data obtained with the XMM-Newton Observatory of the long period dwarf nova RU Peg. RU Peg contains a massive white dwarf, possibly the hottest white dwarf in a dwarf nova, it has a low inclination, thus optimally exposing its X-ray emitting boundary layer, and has an excellent trigonometric parallax distance.We modeled the X-ray data using XSPEC assuming a multi-temperature plasma emission model built from the MEKAL code (i.e., CEVMKL). We obtained a maximum temperature of 31.7 keV, based on the EPIC MOS1, 2 and pn data, indicating that RU Peg has an X-ray spectrum harder than most dwarf novae, except U Gem. This result is consistent with and indirectly confirms the large mass of the white dwarf in RU Peg. The X-ray luminosity we computed corresponds to a boundary layer luminosity for a mass accretion rate of 2 × 10 −11 M ⊙ /yr (assuming M wd = 1.3M ⊙ ), in agreement with the expected quiescent accretion rate. The modeling of the O viii emission line at 19Å as observed by the RGS implies a projected stellar rotational velocity v rot sin i =695 km s −1 , i.e. the line is emitted from material rotating at ∼936-1245 km s −1 (i ∼ 34 • − 48 • ) or about 1/6 of the Keplerian speed; this velocity is much larger than the rotation speed of the white dwarf inferred from the Far Ultraviolet Spectroscopic Explorer (FUSE) spectrum. Cross-correletion analysis yielded an undelayed (time lag ∼ 0) component and a delayed component of 116±17 sec where the X-ray variations/fluctuations lagged the UV variations. This indicates that the UV fluctuations in the inner disk are propagated into the X-ray emitting region in about 116 sec. The undelayed component may be related to irradiation effects.

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The Nature of the Hard X‐Ray–Emitting Symbiotic Star RT Cru

Cited by 50 publications

References 50 publications

SU Lyncis, a hard X-ray bright M giant: clues point to a large hidden population of symbiotic stars

SU Lyncis, a hard X-ray bright M giant: clues point to a large hidden population of symbiotic stars

DETECTION OF X-RAYS FROM THE SYMBIOTIC STAR V1329 Cyg

XMM-NEWTONOBSERVATIONS OF THE DWARF NOVA RU Peg IN QUIESCENCE: PROBE OF THE BOUNDARY LAYER

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