XMM-Newtonobservations of RR Telescopii: evidence for wind signatures and shocked gas emission

Abstract

RR Telescopii is the prototype of the symbiotic novae class. Since its outburst in 1944, it has been slowly fading, and its emission-line spectrum has evolved significantly. In this paper we discuss XMM-Newton observations of RR Tel taken in April 2009. These are the first X-ray high-resolution spectra of this system, and they provide important information about the physical conditions of the emitting gas. We have estimated the temperature and the luminosity of the hot star to be 154 kK and 5000 L , respectively, from the comparison of model atmospheres with the X-ray spectra. Normalisation of the models with the far ultraviolet flux leads to similar values. Both the shape of the low-resolution X-ray spectrum and the spectral diagnostics that make use of the emission lines present in the RGS spectrum indicate the existence of collisionally ionised gas. At least two components are present, with temperatures of ≈0.6 and 1.7 MK. The existence of a wind from the hot star is unequivocally confirmed by HST-STIS observations taken in 2000, which showed displaced absorption components for the N V 1240 Å and C IV 1550 Å doublets. These components have terminal velocities of the order of 400 km s −1 , which is consistent with the temperature of the gas detected in X-rays.

The calibration of read-out-streak photometry in theXMM–NewtonOptical Monitor and the construction of a bright-source catalogue

“…Shortward of 1500 Å, the UV flux of RR Tel is thought to be dominated by the central star, while longward of 1800 Å the UV flux is likely to be dominated by nebular emission (Nussbaumber & Dumm, 1997). In a study of the X-ray and ultraviolet emission from RR Tel, based on an XMM-Newton observation taken in 2009, González-Riestra, Selvelli & Cassatella (2013) show that the 2009 XMM-OM photometry through the UVW2 and UVM2 filters are consistent with an extrapolation of the exponential decay seen in International Ultraviolet Explorer (IUE) data between 1978and 1995. However, González-Riestra, Selvelli & Cassatella (2013 describe the XMM-OM UVW1 photometry as uncertain, because it is subject to a large degree of coincidence loss.…”

Raman-scattered O vi Features in the Symbiotic Nova RR Telescopii

“…Here, a is the binary separation, L H is the H-ionizing photon number luminosity, α B is the case B recombination coefficient for H I, and m H is the proton mass. In this work, we adopt the values of a = 56 au, L H = 7 × 10 47 s −1 that were used in previous works (Hinkle et al 2013;González-Riestra et al 2013).…”

“…Meanwhile, the effective temperature of the WD has continued to rise from T ∼ 6750 K in May 1949 (Pottasch & Varsavsky 1960) and it has exceeded > 140000 K after 1978 (e.g., Hayes & Nussbaumer 1996;Jordan et al 1994). Based on the recent X-ray observations with XMM-Newton, González-Riestra et al (2013) estimated its temperature T ∼ 154000 K and luminosity L ∼ 5000 L assuming a distance of 2.6 kpc. The orbital period of this object is still quite uncertain but it is believed to exceed several decades (Lee & Park 1999;Schmid & Schild 2002).…”

Photometry of Symbiotic Stars - XIV

“…The accreting WD represents a strong source of the supersoft X-ray to UV radiation (T WD > ∼ 10 5 K, L WD ∼ 10 1 −10 4 L ⊙ ) in the binary (Muerset et al, 1991;Skopal, 2005;Skopal et al, 2009;González-Riestra et al, 2013;Ramsay et al, 2016;Skopal et al, 2017b) that ionizes a fraction of the wind from the giant giving rise to the nebular emission (e.g. Boyarchuk et al, 1966;Seaquist et al, 1984;Kenyon & Webbink, 1984;Nussbaumer & Vogel, 1987).…”

“…Sometimes symbiotic stars experience unpredictable outbursts characterized by ∼ 1−3 mag (multiple) brightening(s) in the optical, observed on the timescale of a few months to years/decades (see e.g., historical LCs of FN Sgr, Z And, AX Per of Brandi et al, 2005;Leibowitz & Formiggini, 2008;Skopal et al, 2011) with signatures of a mass-outflow (e.g., Fernandez-Castro et al, 1995;Esipov et al, 2000;Skopal, 2006;McKeever et al, 2011;González-Riestra et al, 2013). Outbursts of symbiotic stars are called 'Z And-type' outbursts, as they were observed in the past for a prototype of the class of symbiotic stars -Z And (Kenyon, 1986).…”