A Long Serendipitous XMM-Newton Observation of the Intermediate Polar XY Ari

XY Ari is one of the few known eclipsing intermediate polars. We present results from a detailed analysis of an unpublished archival observation using XMM-Newton EPIC pn and MOS data in a quiescent state of XY Ari. The X-ray orbital modulation and spin pulse variations were investigated for energy dependent modulations in different energy bands. The broad orbital modulation observed with various observations was confirmed with XMM-Newton at hard X-ray (>1.6 keV). The EPIC light curves folded at the spin phases show a double peak profile as expected from two pole accretion. The pulse profile is found to be energy dependent. Hardness ratio variations and energy modulation depth during spin modulation can be explained by photoelectric absorption. The simultaneously fitted EPIC spectra with CEVMKL model yield maximum plasma temperature of $28^{+3.1}_{-2.9}$ keV with an iron abundance $\mathrm{Fe}/\mathrm{Fe}_\odot=0.37^{+0.06}_{-0.05}$. We find two intrinsic partial covering absorption columns of $6.2^{+1.0}_{-0.9} \times 10^{22}$ and $105.3^{+35.4}_{-30.4} \times 10^{22} \,\mathrm{cm^{-2}}$ with covering fractions of $0.53^{+0.05}_{-0.04}$, $0.41^{+0.14}_{-0.13}$ respectively. In addition, a Gaussian emission line at $6.43^{+0.01}_{-0.02}$ keV with an equivalent width of $51^{+12}_{-10}$ eV is required to account for fluorescent emission from neutral iron. The X-ray luminosity of the source is $4.2 \times 10^{32} \,\mathrm{erg \,s^{-1}}$ in the 0.2-10.0 keV energy band.Comment: 12 pages, 9 figures, 2 tables, accepted in MNRA

Ilık soğurganların kataklismik değişkenlerde ve x-ışını çift yıldız sistemlerinde incelenmesi

TÜBİTAK TBAG Proje01.03.2012Our project is mainly on studying warm absorbers and complicated ionized and cold absorption in Cataclysmic Binaries and Low-mass and High mass X-ray binaries. Our other aims was to particularly understand and follow the X-ray evolution of classical novae (subclass of Cataclysmic Variables) during the outburst phases and study how the emission components change in time. A new approach in this project will be to study the white dwarf atmospheric emission during the hot phases of the evolution using the warm absorber and collisionally ionized absorber models. As it stands in the literature the analysis of the high resolution X-ray spectroscopy of Nova in outburst is very inadequate. In addition, in some particularly magnetic Cataclysmic Variables which shows complex absorption characteristics we plan to apply warm absorber models to explain the absorption properties and shed light into the light variations that can not be explained by mass transfer variations. This may well explain the orbital modulations in Intermediate Polar magnetic Cataclysmic Variables. We also plan to study warmabsorbers in Low-mass X-ray binaries by using timing techniques that are newly develped and try to ensemble the location of the absorbers in these systems and also look for any warmabsorber effects in High-mass X-ray binaries. In addition we plan to follow the X-ray evolution of Novae during the outburst stage with the ongoing X-ray missions in large collaborations

The Detection of a 3.5-h Period in the Classical Nova Velorum 1999 (V382 Vel) and the Long Term Behavior of the Nova Light Curve

We present CCD photometry, light curve and time series analysis of the classical nova V382 Vel (N Vel 1999). The source was observed for 2 nights in 2000, 21 nights in 2001 and 7 nights in 2002 using clear filters. We report the detection of a distinct period in the light curve of the nova P=0.146126(18) d (3.5 h). The period is evident in all data sets, and we interpret it as the binary period of the system. We also measured an increase in the amplitude modulation of the optical light (in magnitude) by more than 55% from 2000 to 2001 and about 64% from 2001 to 2002. The pulse profiles in 2001 show deviations from a pure sinusoidal shape which progressively become more sinusoidal by 2002. The main cause of the variations in 2001 and 2002 can be explained with the occultation of the accretion disk by the secondary star. We interpret the observed deviations from a pure sinusoidal shape as additional flux resulting from the aspect variations of the irradiated face of the secondary star.Comment: 16 pages and 4 figures, accepted as it stands to be published in the Astronomical Journal (AJ

Optical Counterparts of ULXs and Their Host Environments in NGC 4490/4485

We report the identification of the possible optical counterparts of five out of seven Ultraluminous X-ray Sources (ULXs) in NGC 4490/4485 galaxy pair. Using archival Hubble Space Telescope ({\it HST}) imaging data, we identified a single optical candidate for two ULXs (X-4 and X-7) and multiple optical candidates for the other three ULXs (X-2, X-3 and X-6) within $\sim$ 0\farcs2 error radius at the 90\% confidence level. Of the two remaining ULXs, X-1 has no {\it HST} imaging data and photometry could not be performed due to the position of X-5 in NGC4490. Absolute magnitudes ($M_{V}$) of the optical candidates lie between $-5.7$ and $-3.8$. Color-Magnitude Diagrams (CMDs) have been used to investigate the properties of counterparts and their environments. The locations of the counterparts of X-2, X-4, and X-6 suggest possible association with nearby group of stars while others have no association with a star cluster or group of stars. For comparison purposes, we analyzed previously unused three archival XMM-Newton observations. The long-term X-ray light curves of the sources (except transient X-7) show variability by a factor of three in a time scale more than a decade. The use of disk blackbody model for the mass of the compact objects indicates that these objects might have masses most likely in the range 10$-$15 M_{\sun}.Comment: 20 pages, 13 figures, submitted to Ap

The CHANDRA observation of the first resolved and detected classical nova shell in X-rays: The shell of Nova Persei 1901 (GK Per)

I present the CHANDRA ACIS-S data of the classical nova shell of Nova Persei (1901). The X-ray nebula is detected with a count rate of 0.10+/-0.003 c s(-1). It is asymmetric with bulk of emission on the southwestern quadrant. The X-ray emission from the vicinity of the radio ridge is detected as an arc that covers from west to south of the central source. The X-ray spectrum consists at least of two components of emission. The lower temperature component (below 2 keV) has kT 0.15+/-0.02 keV with an X-ray flux of 6.5x10(-13) erg cm(-2) s(-1). There is also a high temperature, kT > 15 keV, embedded, N-H=1.7+/-0.2x10(22) cm(-2), component prominent above 2 keV. The unabsorbed X-ray flux from this component is 1.1x10(-12) erg cm(-2) s(-1). A distinct emission line of Neon [NeIX] is detected with a flux of 1.5x10(-14) erg cm(-2) s(-1). Enhancement in the elemental abundances of Ne and N compared to their solar mass fractions are detected as 6-9 and 3-6 respectively. The X-ray luminosities indicate that the shock is adiabatic and the remnant is most likely in an early phase of evolution

A study of selected low-mass X-ray binary dip sources observed with INTEGRAL

I present archival data of the dipping LMXB systems, XB 1916-053, XB 1323-619, X1624-490, and 4U 1746-371obtained by the ISGRI and JEM-X detectors on-board the INTEGRAL Observatory. The spectral parameters derived from the fits to the data are consistent with hot coronal regions in these systems where the electron temperatures are in a range 4.9-18.8 keV with the exception of XB 1323-62 having an unbounded temperature. The optical depth to Compton scattering, tau is low and consistent with electron densities n(e) < 10 x 10(15) cm(-3). We interpret that the three of the dipping LMXBs in the scope of this work host hot extended large coronal structures which constitute a symmetric region on the disk responsible for the Comptonization in the systems. We find absorption differences between dipping and non-dipping intervals for XB 1916-053 and X 1624-490 in the JEM-X energy range. The dip and non-dip spectra in the ISGRI energy range (above 20 keV) show no significant difference four the sources. Fits including an additional photo-ionized absorber model for the two sources show that XB 1916-053 has the highest ionized absorber

Pre-outburst Chandra observations of the recurrent nova T Pyxidis

Aims. I study the spectral, temporal, and spatial characteristics of the quiescent X-ray emission (not in outburst) of the recurrent nova T Pyx

Accretion flows in nonmagnetic white dwarf binaries as observed in X-rays

Cataclysmic Variables (CVs) are compact binaries with white dwarf (WD) primaries. CVs and other accreting WD binaries (AWBs) are useful laboratories for studying accretion flows, gas dynamics, outflows, transient outbursts, and explosive nuclear burning under different astrophysical plasma conditions. They have been studied over decades and are important for population studies of galactic X-ray sources. Recent space-and ground-based high resolution spectral and timing studies, along with recent surveys indicate that we still have observational and theoretical complexities yet to answer. I review accretion in nonmagnetic AWBs in the light of X-ray observations. I present X-ray diagnostics of accretion in dwarf novae and the disk outbursts, the nova-like systems, and the state of the research on the disk winds and outflows in the nonmagnetic CVs together with comparisons and relations to classical and recurrent nova systems, AM CVns and Symbiotic systems. I discuss how the advective hot accretion flows (ADAF-like) in the inner regions of accretion disks (merged with boundary layer zones) in nonmagnetic CVs explain most of the discrepancies and complexities that have been encountered in the X-ray observations. I stress how flickering variability studies from optical to X-rays can be probes to determine accretion history and disk structure together with how the temporal and spectral variability of CVs are related to that of LMXBs and AGNs. Finally, I discuss the nature of accretion in nonmagnetic WDs in terms of ADAF-like accretion flows, and elaborate on the solu-tions it brings and its complications, constructing an observational framework to motivate new theoretical calculations that introduce this flow-type in disks, outflow and wind models together with disk-instability models of outbursts and nova outbursts in AWBs and WD physics, in general. (C) 2020 COSPAR. Published by Elsevier Ltd. All rights reserved