Identifying a new intermediate polar using XMM-Newton and INTEGRAL

Abstract

The bright X-ray source 2XMMi J180438.7−145647 is fortunate to have long baseline observations in INTEGRAL that complement observations taken by other missions. Optical spectroscopy of this object has suggested a distance of ∼7 kpc and an identification with a low-mass X-ray binary. We instead use the X-ray data from 0.3 to 40 keV to identify the source as a bright intermediate polar (IP) with an estimate for the white dwarf mass of ∼0.60 M . This identification is supported by the presence of an iron triplet, the component lines of which are some of the strongest seen in IPs, and the signature of the spin period of the white dwarf at ∼24 min. We note that the lack of broad-band variability may suggest that this object is a stream-fed IP, similar in many respects to the well-studied IP, V2400 Oph. Phase binning has allowed us to create spectra corresponding to the peaks and troughs of the light curve from which we determine that the spectra appear harder in the troughs, consistent with the behaviour of other IPs binned on their spin periods. This work strongly suggests a misidentification in the optical due to the presence of large columns of enshrouding material. We instead propose a distance to the source of <2.5 kpc to be consistent with the luminosities of other IPs in the dim, hard state. The considerable flux of the source together with the strength of the iron lines may, in future, allow the source to be used to diagnose the properties of the shock-heated plasma and the reflected component of the emission.

A Broadband Look at the Old and New ULXs of NGC 6946

“…IPs can possess hard spectra like that we find for ULX-4, but they are also expected to exhibit iron features (e.g. Kuulkers et al 2006;Middleton et al 2012) which we do not see in this source. In addition, the lack of an obvious foreground star detection limits any possible Galactic optical counterpart to dwarf stars.…”

Investigation of some physical properties of accretion induced collapse in producing millisecond pulsars

“…where the minimum spin period of the standard WD (de Jager et al (1994); Middleton et al (2011)) taking value ∼ 30 s, R N S = 10 km and R W D = 1000 km (see Eqn 1) , giving…”

“…Bhattacharya and van den Heuvel (1991); Lorimer (2008); Wang et al (2011)). The required conditions for the formation of an AIC in the case of a steady accretion were summarized in Nomoto (1984Nomoto ( , 1987, Isern and Hernanz (1994) and in two recent works Chen et al (2011) and Taani et al (2012). However, unless the accretion rates are very high (> 10 −7 M ⊙ yr −1 ), the accreted (Hydrogen) matter will not go into steady nuclear burning on the surface of the WD, and hence its mass will never grow.…”

“…Cataclysmic variables (CVs) are short-period binary systems consisting of massive white dwarfs (WDs) primary that is accreting material via Roche-lobe overflow from low-mass secondary stars (see i. e. Warner (1995); Warner and Woudt (2002); Middleton et al (2011)), so Accretion Induced Collapse (AIC) is favorable in these systems (van den Heuvel (2004)). …”

INTEGRAL view on Cataclysmic Variables and Symbiotic Binaries

“…Based on the relation (3) we estimated WD masses in three systems, the polar IGR J14536-5522, and the two IPs, IGR J16167-4957 and 2XMMi J180438.7-145647) with well determined bremsstrahlung temperatures. Worth mentioning is the estimated mass for the AM Her type system V1432 Aql (see Table 2) that is Note: * -discovered by INTEGRAL, IP -an intermediate polar, AM -a polar, type AM Her, a -the WD masses from [30], b -kT br from [56], c -kT br from [55], d -kT br taken from [82], e -the WD masses obtained using INTEGRAL observations. The corresponding references are shown in the last column.…”