Classifying IGR J15038−6021 as a magnetic CV with a massive white dwarf

Section I. Halo White Dwarfs and Galactic Structure. Old Ultracool White Dwarfs as Cosmological Probes. Number counts of white dwarfs: the impact of GAIA. Influence of Metallicity in the Determination of the Age of Halo White Dwarfs. Cool Halo White Dwarfs from GSCII. Dark halo baryons not in ancient white dwarfs? White Dwarfs in 2QZ and Sloan Surveys. White Dwarfs and Cataclysmic in the FBS. White Dwarfs in Globular Clusters. Core/Envelope Symmetry in Pulsating White Dwarfs Stars. A Search for Variability in Cool White Dwarf Stars. Planetary Nebulae and the Galactic Bulge. Section II. Type Ia Supernovae. Type Ia Supernovae and Cosmology. The Progenitors of Type Ia Supernovae. Progenitors of Supernovae Type Ia. Polulation synthesis for progenitors of type Ia supernovae. How far can we trust SNE Ia as Standard Candles? Kirshner on White Dwarfs. Supernovae. and Cosmology. Section III. Cataclysmic Variables and White Dwarf Accretion. Accretion in Cataclysmic Variable Stars. White Dwarfs in Cataclysmic Variables: Probes of Accretion History. Intermediate Polars in Low States. Chemical Abundances of WDs in CVs. AM CVn Stars in the UCT CCD CV Survey. TUG Observations of V2275 Cyg, RW Umi, PX And and FO Per. The Possible Identification of Two Hibernating Novae. Evidence for large superhumps in TX Col and V4742 Sgr. Concluding remarks.

Type Ia supernovae (SNe Ia) play a key role in measuring cosmological parameters, in which the Phillips relation is adopted. However, the origin of the relation is still unclear. Several parameters are suggested, e.g. the relative content of carbon to oxygen (C/O) and the central density of the white dwarf (WD) at ignition. These parameters are mainly determined by the WD's initial mass and its cooling time, respectively. Using the progenitor model developed by Meng & Yang, we present the distributions of the initial WD mass and the cooling time. We do not find any correlation between these parameters. However, we notice that as the range of the WD's mass decreases, its average value increases with the cooling time. These results could provide a constraint when simulating the SN Ia explosion, i.e. the WDs with a high C/O ratio usually have a lower central density at ignition, while those having the highest central density at ignition generally have a lower C/O ratio. The cooling time is mainly determined by the evolutionary age of secondaries, and the scatter of the cooling time decreases with the evolutionary age. Our results may indicate that WDs with a long cooling time have more uniform properties than those with a short cooling time, which may be helpful to explain why SNe Ia in elliptical galaxies have a more uniform maximum luminosity than those in spiral galaxies.

Optical and infrared light-curves of classical novae are approximately homologous among various white dwarf (WD) masses and chemical compositions when free-free emission from optically thin ejecta dominates the continuum flux of novae. Such a homologous template light-curve is called a ``universal decline law.'' The timescale of the light curve depends strongly on the WD mass but weakly on the chemical composition, so we are able to roughly estimate the WD mass from the light-curve fitting. We have applied the universal decline law to the old nova GK Persei 1901 and recent novae that outbursted in 2005. The estimated WD mass is 1.15 M_sun for GK Per, which is consistent with a central value of the WD mass determined from the orbital velocity variations. The other WD masses of 10 novae in 2005 are also estimated to be 1.05 M_sun (V2361 Cyg), 1.15 M_sun (V382 Nor), 1.2 M_sun (V5115 Sgr), 0.7 M_sun (V378 Ser), 0.9 M_sun (V5116 Sgr), 1.25 M_sun (V1188 Sco), 0.7 M_sun (V1047 Cen), 0.95 M_sun (V476 Sct), 0.95 M_sun (V1663 Aql), and 1.30 M_sun (V477 Sct), within a rough accuracy of +- 0.1 M_sun. Four (V382 Nor, V5115 Sgr, V1188 Sco, and V477 Sct) of ten novae in the year 2005 are probably neon novae on an O-Ne-Mg WD. Each WD mass depends weakly on the chemical composition (especially the hydrogen content X in mass weight), i.e., the obtained WD masses increase by +0.5(X-0.35) M_sun for the six CO novae and by +0.5(X-0.55) M_sun for the four neon novae above. Various nova parameters are discussed in relation to its WD mass.

Type Ia supernovae (SNe Ia) are the thermonuclear explosions of carbon-oxygen white dwarfs in binary systems with another white dwarf, or a main sequence or red giant star. The nature of the stellar companion star, and the mechanism by which the white dwarf explodes are some of the long-lasting mysteries in astrophysics. To probe their nature, we are exploring the dynamically-driven double-degenerate double detonation model. In this proposed model, a carbon-oxygen (CO) white dwarf in a binary system with another CO white dwarf with thin surface helium shells can lead to a surface helium detonation. This surface detonation in turn can lead to the detonation of the carbon in the core. I explore three-dimensional hydrodynamical simulations of the D6 model using the Eulerian grid code FLASH. Additionally, I have turned to the observations of the late-time light curves of SNe Ia to put constraints on the nature of the progenitors. From the late-time (> 300 days) observations of SNe Ia light curves, the rate of decay of the light-curve slows. An extra source of energy is thought to arise from the radioactive decay of the neutron-rich isotope 57Ni, which is a long-lived neutron-rich radioisotope that can be used to distinguish between a Chandrasekhar mass (MCh) white dwarf and a sub-Chandrasekhar mass (sub-MCh) white dwarf progenitor. In this work, we have compared nucleosynthetic yields of 57Ni from simulations spanning a wide range of parameter space of MCh and sub-MCh models and compared these against the yields inferred from five SNe Ia.

Recent discovery of several overluminous type Ia supernovae (SNe Ia) indicates that the explosive masses of white dwarfs may significantly exceed the canonical Chandrasekhar mass limit. Rapid differential rotation may support these massive white dwarfs. Based on the single-degenerate scenario, and assuming that the white dwarfs would differentially rotate when the accretion rate $\dot{M}>3\times 10^{-7}M_{\odot}\rm yr^{-1}$, employing Eggleton's stellar evolution code we have performed the numerical calculations for $\sim$ 1000 binary systems consisting of a He star and a CO white dwarf (WD). We present the initial parameters in the orbital period - helium star mass plane (for WD masses of $1.0 M_{\odot}$ and $1.2 M_{\odot}$, respectively), which lead to super-Chandrasekhar mass SNe Ia. Our results indicate that, for an initial massive WD of $1.2 M_{\odot}$, a large number of SNe Ia may result from super-Chandrasekhar mass WDs, and the highest mass of the WD at the moment of SNe Ia explosion is 1.81 $M_\odot$, but very massive ($>1.85M_{\odot}$) WDs cannot be formed. However, when the initial mass of WDs is $1.0 M_{\odot}$, the explosive masses of SNe Ia are nearly uniform, which is consistent with the rareness of super-Chandrasekhar mass SNe Ia in observations.

Recent observational and theoretical progress has favored merging and helium-accreting sub-Chandrasekhar mass white dwarfs in the double-degenerate and the double-detonation channels, respectively, as the most promising progenitors of normal Type Ia supernovae (SNe Ia). Thus the fate of rapidly-accreting Chandrasekhar mass white dwarfs in the single-degenerate channel remains more mysterious then ever. In this paper, we clarify the nature of ignition in Chandrasekhar-mass single-degenerate SNe Ia by analytically deriving the existence of a characteristic length scale which establishes a transition from central ignitions to buoyancy-driven ignitions. Using this criterion, combined with data from three-dimensional simulations of convection and ignition, we demonstrate that the overwhelming majority of ignition events within Chandrasekhar-mass white dwarfs in the single-degenerate channel are buoyancy-driven, and consequently lack a vigorous deflagration phase. We thus infer that single-degenerate SNe Ia are generally expected to lead to overluminous 1991T-like SNe Ia events. We establish that the rates predicted from both the population of supersoft X-ray sources and binary population synthesis models of the single-degenerate channel are broadly consistent with the observed rates of overluminous SNe Ia, and suggest that the population of supersoft X-ray sources are the dominant stellar progenitors of SNe 1991T-like events. We further demonstrate that the single-degenerate channel contribution to the normal and failed 2002cx-like rates is not likely to exceed 1% of the total SNe Ia rate. We conclude with a range of observational tests of overluminous SNe Ia which will either support or strongly constrain the single-degenerate scenario.

Context. The binary system SDSS J1257+5428 consists of an extremely low-mass white dwarf (WD) with a mass ranging from ∼0.1 to ∼0.24 M⊙, along with a more massive WD companion of approximately 1 M⊙ that is significantly hotter. Recently, a tertiary WD orbiting this binary was discovered, setting a lower limit for the total age (∼4 Gyr) of the triple and providing further constraints on SDSS J1257+5428 that could be used to constrain its formation pathways. Up to now, the existence of this system has been described as paradoxical since tested models for its formation cannot account for its properties. Aims. Here we investigate under which conditions SDSS J1257+5428 could be understood as a descendant of a cataclysmic variable with an evolved donor star, which is a scenario that has never been explored in detail. Methods. We used the rapid BSE code for pre-common-envelope (CE) evolution and the detailed MESA code for post-CE evolution to carry out binary evolution simulations and searched for potential formation pathways for SDSS J1257+5428 that lead to its observed characteristics. For the post-CE evolution, we adopted a boosted version of the CARB model, which has been successfully used to explain the properties of close binary stars hosting evolved solar-type stars. Results. We find that SDSS J1257+5428 can be explained as a post-cataclysmic-variable system if (i) the progenitor of the extremely low-mass WD was initially a solar-type star that evolved into a subgiant before the onset of mass transfer and underwent hydrogen shell flashes after the mass transfer stopped, (ii) the massive WD was highly or entirely rejuvenated during the cataclysmic variable evolution, and (iii) magnetic braking was strong enough to make the evolution convergent. In this case, the torques due to magnetic braking need to be stronger than those provided by the CARB model by a factor of ∼100. Conclusions. We conclude that SDSS J1257+5428 can be reasonably well explained as having originated from a cataclysmic variable that hosted an evolved donor star and should no longer be regarded as paradoxical. If our formation channel is correct, our findings provide further support that stronger magnetic braking acts on progenitors of (i) close detached WD binaries, (ii) close detached millisecond pulsar with extremely low-mass WDs, (iii) AM CVn binaries, and (iv) ultra-compact X-ray binaries, in comparison to the magnetic braking strength required to explain binaries hosting main-sequence stars and single main-sequence stars.

Context. The disc instability model (DIM) has been very successful in explaining the dwarf nova outbursts observed in cataclysmic variables. When, as in intermediate polars, the accreting white dwarf is magnetised, the disc is truncated at the magnetospheric radius, but for mass-transfer rates corresponding to the thermal-viscous instability such systems should still exhibit dwarf-nova outbursts. Yet, the majority of intermediate polars, in which the magnetic field is not large enough to completely disrupt the accretion disc, seem to be stable, and the rare observed outbursts, in particular in systems with long orbital periods, are much shorter than normal dwarf-nova outbursts. Aims. We investigate the predictions of the disc instability model for intermediate polars in order to determine which of the observed properties of these systems can be explained by the DIM. Methods. We use our numerical code for the time evolution of accretion discs, modified to include the effects of the magnetic field, with constant or variable mass transfer from the secondary star. Results. We show that intermediate polars have mass transfer low enough and magnetic fields large enough to keep the accretion disc stable on the cold equilibrium branch. We show that the infrequent and short outbursts observed in long-period systems, such as, for example, TV Col, cannot be attributed to the thermal-viscous instability of the accretion disc, but instead have to be triggered by an enhanced mass-transfer from the secondary, or, more likely, by some instability coupling the white dwarf magnetic field with that generated by the magnetorotational instability operating in the accretion disc. Longer outbursts (a few days) could result from the disc instability.

Type Ia supernovae (SNe Ia) often show high-velocity absorption features (HVFs) in their early phase spectra; however the origin of the HVFs is unknown. We show that a near-Chandrasekhar-mass white dwarf (WD) develops a silicon-rich layer on a carbon-oxygen (CO) core before it explodes as an SN Ia. We calculated the nuclear yields in successive helium shell flashes for 1.0 $M_\odot$, 1.2 $M_\odot$, and 1.35 $M_\odot$ CO WDs accreting helium-rich matter with several mass-accretion rates ranging from $1 \times 10^{-7}~M_\odot$ yr$^{-1}$ to $7.5 \times 10^{-7}~M_\odot$ yr$^{-1}$. For the $1.35~M_\odot$ WD with the accretion rate of $1.6 \times 10^{-7}~M_\odot$ yr$^{-1}$, the surface layer developed as helium burning ash and consisted of 40% $^{24}$Mg, 33% $^{12}$C, 23% $^{28}$Si, and a few percent of $^{20}$Ne by weight. For a higher mass accretion rate of $7.5 \times 10^{-7}~M_\odot$ yr$^{-1}$, the surface layer consisted of 58% $^{12}$C, 31% $^{24}$Mg, and 0.43% $^{28}$Si. For the $1.2~M_\odot$ WDs, silicon is produced only for lower mass accretion rates (2% for $1.6 \times 10^{-7}~M_\odot$ yr$^{-1}$). No substantial silicon ($< 0.07%$) is produced on the $1.0~M_\odot$ WD independently of the mass-accretion rate. If the silicon-rich surface layer is the origin of Si II HVFs, its characteristics are consistent with that of mass increasing WDs. We also discuss possible Ca production on very massive WDs ($ \gtrsim 1.38~M_\odot$).

We present a detailed model atmosphere analysis of massive white dwarfs with M > 0.9 M ⊙ and T eff ≥ 11,000 K in the Montreal White Dwarf Database 100 pc sample and the Pan-STARRS footprint. We obtained follow-up optical spectroscopy of 109 objects with no previous spectral classification in the literature. Our spectroscopic follow-up is now complete for all 204 objects in the sample. We find 118 normal DA white dwarfs, including 45 massive DAs near the ZZ Ceti instability strip. There are no normal massive DBs: the six DBs in the sample are strongly magnetic and/or rapidly rotating. There are 20 massive DQ white dwarfs in our sample, and all are found in the crystallization sequence. In addition, 66 targets are magnetic (32% of the sample). We use magnetic white dwarf atmosphere models to constrain the field strength and geometry using offset dipole models. We also use magnetism, kinematics, and rotation measurements to constrain the fraction of merger remnant candidates among this population. The merger fraction of this sample increases from 25% for 0.9–1 M ⊙ white dwarfs to 49% for 1.2–1.3 M ⊙. However, this fraction is as high as 78−7+4 % for 1.1–1.2 M ⊙ white dwarfs. Previous works have demonstrated that 5%–9% of high-mass white dwarfs stop cooling for ∼8 Gyr due to the 22Ne distillation process, which leads to an overdensity of Q-branch stars in the solar neighborhood. We demonstrate that the overabundance of the merger remnant candidates in our sample is likely due to the same process.

Accurate apparent and intrinsic luminosities of objects are very important in astronomy, for without them we cannot calculate accurate distances or scale the energy budget of physical models. This dissertation deals with observations of two of the most widely used astronomical standard (or standardizable) candles. The Sloan Digital Sky Survey (SDSS) is an important survey presently being carried out, which will provide photometry of roughly 10 objects over a 10,000 square degree area of sky (D. G. York et al. 2000, AJ, 120, 1579). One million spectra of galaxies will be obtained, and many high-redshift quasars will be discovered (see, e.g., X. Fan et al. 1999, AJ, 118, 1). Many new candidate variable stars in our Galaxy will also be identified, amongst them RR Lyrae stars (roughly one per square degree). Distances and velocities of a large number of such objects will allow us to refine models of the Galaxy’s halo and to measure the Galaxy’s mass. We observed a number of types of objects of interest in SDSS filters (RR Lyrae stars, Cepheids, cataclysmic variables, carbon stars, and asteroids) and showed to what extent these objects can be identified solely on the basis of their SDSS colors. Details can be found in a paper already published in this journal (K. Krisciunas, B. Margon, & P. Szkody 1998, PASP, 110, 1342). In particular, Figure 12 of that paper shows the color locus of bona fide RR Lyrae stars. We have observed one dozen RR Lyrae candidates identified from SDSS commissioning data and proved beyond a shadow of a doubt that all are RR Lyrae stars. Light curves of six candidates identified by B. Willman and S. Anderson are to be found in Z. Ivezic et al. (2000, AJ, 120, 963). Five of the other confirmed RR Lyrae stars are objects 5, 9, 134, 141, and 144 from Table 2 of Ivezic et al. Figure 1 shows the folded light curve of star 144. Owing to their luminosities ( at maximum), Type M ≈ 19.4 V Ia supernovae (SNe) are the most important standardizable candle used in extragalactic astronomy because they can be seen halfway across the visible universe. We use the word “standardizable” because, unlike RR Lyrae stars of identical metallicity, Type Ia SNe do not all have the same intrinsic luminosity. Those which rise faster and subsequently decline faster are intrinsically fainter at maximum compared to those which rise more slowly and decline more slowly. See M. M. Phillips et al. (1999, AJ, 118, 1766). As to an explosion mechanism, the favorite scenario is the deflagration of a carbonoxygen white dwarf which reaches the Chandrasekhar limit due to mass infall from a companion star (M. Livio 2000, preprint, astro-ph/0005344). Deflagration is a type of rapid, but subsonic, combustion in which the flame front is driven by turbulent heat exchange. It is also possible that some Type Ia SNe are due to a sub–Chandrasekhar-mass detonation of an accreted surface helium layer on a C-O white dwarf (P. Pinto, R. G. Eastman, & T. Rogers 2000, preprint, astro-ph/0008330). One of the potentially significant sources of error in determining the distance to a Type Ia SN is the contribution of extinction by dust in the host galaxy. What we need is a “wellbehaved” color index with the largest possible wavelength baseline. Since V) for standard Galactic dust, the A ≈ 3.1 # E(B V uncertainties in the color excess and the scale factor can lead to significant uncertainties in the extinction correction. J. H. Elias et al. (1985, ApJ, 296, 379) already showed that Type Ia SNe exhibit some degree of uniform V K color evolution, while B H photometry such as that of B. Leibundgut (1988, Ph.D. dissertation, Univ. Basel) is not as well behaved. Since K), the potential for A ≈ 1.21 # E(V H) ≈ 1.13 # E(V V smaller uncertainties for using V minus near-infrared colors AV was encouraging. New optical and near-infrared (JHK) photometry of Type Ia SNe, especially data obtained before B-band maximum, was needed. Y. D. Mayya et al. (1998, IAU Circ. 6907), S. Jha et al. (1999, ApJS, 125, 73), and P. Meikle (2000, MNRAS, 314, 782) have published data for the spectroscopically normal SN 1998bu, the distance of the host of which has also been measured with HST using Cepheids. We have obtained optical and infrared data for the spectroscopically normal Type Ia SNe 1999cl, 1999cp, 2000bk, and 2000ce and for the overluminous, slowly declining, spectroscopically peculiar SNe 1999aa, 1999gp, and 2000cx. Data for three of these have already been published (K. Krisciunas et al. 2000, ApJ, 539, 658).

We use a simple dynamical scheme to simulate the ejecta of type Ia supernova (SN Ia) scenarios with two exploding white dwarfs (WDs) and find that the velocity distribution of the ejecta has difficulties accounting for bimodal emission line profiles with a large separation between the two emission peaks. The essence of the dynamical code is in including the fact that the ejecta does not leave the system instantaneously. We find that the final separation velocity between the centers of masses of the two WDs' ejecta is $\simeq 80 \%$ of the pre-explosion WDs' orbital velocity, i.e., we find separation velocities of $4200-5400 \km \s^{-1}$ for two WDs of masses $M_1=M_2=0.94 M_\odot$. The lower separation velocities we find challenge scenarios with two exploding WDs to explain bimodal emission line profiles with observed velocity separations of up to $\simeq 7000 \km \s^{-1}$. Only the mass in the ejecta of one WD with an explosion velocity lower than the separation velocity contributes to one peak of the bimodal profile; this is the inner ejecta. We find the inner ejecta to be only $\lesssim 15\%$ of the ejecta mass in energetic explosions. Less energetic explosions yield higher inner mass but lower separation velocities. We encourage searching for alternative explanations of bimodal line profiles.

We explore the potential of lunar-based gravitational-wave detectors to broaden the multimessenger astrophysics landscape by detecting mergers of massive (M 1, M 2 &gt; 1M ⊙) double white dwarf (WD) binaries. These systems are potential progenitors of Type Ia supernovae and could serve as independent probes of cosmic expansion. We examine two proposed lunar gravitational-wave detector concepts operating in the subhertz band (0.1–1 Hz): the Gravitational-Wave Lunar Observatory for Cosmology (a proxy for suspended test mass detectors) and the Lunar Gravitational-Wave Antenna (a proxy for seismic array detectors). We estimate that these detectors could reach distances of up to ∼1 Gpc for the most massive mergers. We show that lunar detectors could observe up to dozens of massive WD mergers annually, including those originating from globular clusters. Lunar detectors would constrain the masses of these WDs with an unprecedented accuracy of one part in a million. Furthermore, these detectors would provide early warnings weeks before mergers, including sky-localization of square arcminute resolution, enabling a new era of coordinated multimessenger follow-up of electromagnetic transients—whether they evolve into Type Ia supernovae or accretion-induced collapse events.

We analyze the evolution of binary stars to calculate synthetic rates and delay times of the most promising Type Ia Supernovae (SNe Ia) progenitors. We present and discuss evolutionary scenarios in which a white dwarf (WD) reaches the Chandrasekhar mass and potentially explodes in a SNe Ia. We consider Double Degenerate (DDS; merger of two WDs), Single Degenerate (SDS; WD accreting from H-rich companion), and AM Canum Venaticorum (AM CVn; WD accreting from He-rich companion) scenarios. The results are presented for two different star formation histories: burst (elliptical-like galaxies) and continuous (spiral-like galaxies). It is found that delay times for the DDS in our standard model (with common envelope efficiency αCE = 1) follow a power-law distribution. For the SDS we note a wide range of delay times, while AM CVn progenitors produce a short burst of SNe Ia at early times. The DDS median delay time falls between ∼0.5 and 1 Gyr; the SDS between ∼2 and 3 Gyr; and the AM CVn between ∼0.8 and 0.6 Gyr depending on the assumed αCE. For a Milky-Way-like (MW-like) galaxy, we estimate the rates of SNe Ia arising from different progenitors as: ∼10−4 yr−1 for the SDS and AM CVn, and ∼10−3 yr−1 for the DDS. We point out that only the rates for two merging carbon–oxygen WDs, the only systems found in the DDS, are consistent with the observed rates for typical MW-like spirals. We also note that DDS progenitors are the dominant population in elliptical galaxies. The fact that the delay time distribution for the DDS follows a power law implies more SNe Ia (per unit mass) in young rather than in aged populations. Our results do not exclude other scenarios, but strongly indicate that the DDS is the dominant channel generating SNe Ia in spiral galaxies, at least in the framework of our adopted evolutionary models. Since it is believed that WD mergers cannot produce a thermonuclear explosion given the current understanding of accreting WDs, either the evolutionary calculations along with accretion physics are incorrect, or the explosion calculations are inaccurate and need to be revisited.

Aims. We performed a systematic analysis of X-ray point sources within 1.°5 of the Galactic centre using archival XMM-Newton data. While doing so, we discovered Fe Kα complex emission and pulsation in two highly variable sources, 4XMM J174917.7–283329 and 4XMM J174954.6–294336. In this work we report the findings of the X-ray spectral and timing studies. Methods. We performed detailed spectral modelling of the sources and searched for pulsation in the light curves using Fourier timing analysis. We also searched for multi-wavelength counterparts for the characterization of the sources. Results. The X-ray spectrum of 4XMM J174917.7–283329 shows the presence of complex Fe K emission in the 6–7 keV band. The equivalent widths of the 6.4 and 6.7 keV lines are 99−72+84 and 220−140+160 eV, respectively. The continuum is fitted by a partially absorbed apec model with a plasma temperature of kT = 13−2+10 keV. The inferred mass of the white dwarf (WD) is 0.9−0.2+0.3 M⊙. We detected pulsations with a period of 1212 ± 3 s and a pulsed fraction of 26 ± 6%. The light curves of 4XMM J174954.6–294336 display an asymmetric eclipse and dipping behaviour. To date, this is only the second known intermediate polar to show a total eclipse in X-rays. The spectrum of the sources is characterized by a power-law model with photon index Γ = 0.4 ± 0.2. The equivalent widths of the iron fluorescent (6.4 keV) and Fe XXV (6.7 keV) lines are 171−79+99 and 136−81+89 eV, respectively. The continuum is described by emission from optically thin plasma with a temperature of kT ∼ 35 keV. The inferred mass of the WD is 1.1−0.3+0.2 M⊙. We detect coherent pulsations from the source with a period of 1002 ± 2 s. The pulsed fraction is 66 ± 15%. Conclusions. The spectral modelling indicates the presence of intervening clouds with a high absorbing column density in front of both sources. The detected periodic modulations in the light curves are likely associated with the spin period of WDs in magnetic cataclysmic variables. The measured spin period, hard photon index, and equivalent width of the fluorescent Fe Kα line are consistent with the values found in intermediate polars. 4XMM J174954.6–294336 has already been classified as an intermediate polar, and we suggest that 4XMM J174917.7–283329 is a new intermediate polar. The X-ray eclipses in 4XMM J174954.6–294336 are most likely caused by a low-mass companion star obscuring the central X-ray source. The asymmetry in the eclipse is likely caused by a thick bulge that intercepts the line of sight during the ingress phase but not during the egress phase located behind the WD along the line of sight.