Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userMeasuring the masses of Intermediate Polars with NuSTAR: V709 Cas, NY Lup and V1223 Sgr
92
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The X-ray spectra of intermediate polars can be modelled to give a direct measurement of white dwarf mass. Here we fit accretion column models to NuSTAR spectra of three intermediate polars; V709 Cas, NY Lup and V1223 Sgr in order to determine their masses. From fits to 3-78 keV spectra, we find masses of $M_{rm WD}=0.88^{+0.05}_{-0.04}M_{odot}$, $1.16^{+0.04}_{-0.02}M_{odot}$ and $0.75pm0.02M_{odot}$ for V709 Cas, NY Lup and V1223 Sgr, respectively. Our measurements are generally in agreement with those determined by previous surveys of intermediate polars, but with typically a factor $sim2$ smaller uncertainties. This work paves the way for an approved NuSTAR Legacy Survey of white dwarf masses in intermediate polars.
rate research
Read More
We report on high time resolution, high signal/noise, photo-polarimetry of the intermediate polars NY Lup and IGRJ1509-6649. Our observations confirm the detection and colour dependence of circular polarization from NY Lup and additionally show a clear white dwarf, spin modulated signal. From our new high signal/noise photometry we have unambiguously detected wavelength dependent spin and beat periods and harmonics thereof. IGRJ1509-6649 is discovered to also have a particularly strong spin modulated circularly polarized signal. It appears double peaked through the I filter and single peaked through the B filter, consistent with cyclotron emission from a white dwarf with a relatively strong magnetic field. We discuss the implied accretion geometries in these two systems and any bearing this may have on the possible relationship with the connection between polars and soft X-ray-emitting IPs. The relatively strong magnetic fields is also suggestive of them being polar progenitors.
We present the broadband phase averaged spectrum of one of the brightest intermediate polars V1223 Sgr, obtained with INTEGRAL and RXTE observatories (3-100 keV). Good statistical quality of the spectrum in a hard X-ray energy band (INTEGRAL/IBIS and RXTE/HEXTE) allowed us to disentangle contributions of a direct optically thin plasma emission and a reflected component to the spectrum of V1223 Sgr. The obtained measurement of the post-shock temperature of the accreting matter give us the information about the mass of the white dwarf and the inclination of the system.
The hard X-ray spectrum of magnetic cataclysmic variables can be modelled to provide a measurement of white dwarf mass. This method is complementary to radial velocity measurements, which depend on the (typically rather uncertain) binary inclination. Here we present results from a Legacy Survey of 19 magnetic cataclysmic variables with NuSTAR. We fit accretion column models to their 20-78 keV spectra and derive the white dwarf masses, finding a weighted average $bar{M}_{rm WD}=0.77pm0.02$ $M_{odot}$, with a standard deviation $sigma=0.10$ $M_{odot}$, when we include the masses derived from previous NuSTAR observations of seven additional magnetic cataclysmic variables. We find that the mass distribution of accreting magnetic white dwarfs is consistent with that of white dwarfs in non-magnetic cataclysmic variables. Both peak at a higher mass than the distributions of isolated white dwarfs and post-common-envelope binaries. We speculate as to why this might be the case, proposing that consequential angular momentum losses may play a role in accreting magnetic white dwarfs and/or that our knowledge of how the white dwarf mass changes over accretion-nova cycles may also be incomplete.
We present an analysis of a ~160 ks NuSTAR observation of the nearby bright Seyfert galaxy IC4329A. The high-quality broadband spectrum enables us to separate the effects of distant reflection from the direct coronal continuum, and to therefore accurately measure the high-energy cutoff to be $E_{cut}=178^{+74}_{-40}$ keV. The coronal emission arises from accretion disk photons Compton up-scattered by a thermal plasma, with the spectral index and cutoff being due to a combination of the finite plasma temperature and optical depth. Applying standard Comptonization models, we measure both physical properties independently using the best signal-to-noise obtained to date in an AGN over the 3-79 keV band. We derive $kT_e=37^{+7}_{-6}$ keV with $tau=1.25^{+0.20}_{-0.10}$ assuming a slab geometry for the plasma, and $kT_e=33^{+6}_{-6}$ keV with $tau=3.41^{+0.58}_{-0.38}$ for a spherical geometry, with both having an equivalent goodness-of-fit.
Gamma Cas and its dozen analogs comprise a small but distinct class of X-ray sources. They are early Be-type stars with an exceptionally hard thermal X-ray emission. The X-ray production mechanism has been under intense debate. Two competing ideas are (i) the magnetic activities in the Be star and its disk and (ii) the mass accretion onto the unidentified white dwarf (WD). We adopt the latter as a working hypothesis and apply physical models developed to describe the X-ray spectra of classical WD binaries containing a late-type companion. Models of non-magnetic and magnetic accreting WDs were applied to gamma Cas and its brightest analog HD110432 using the Suzaku and NuSTAR data. The spectra were fitted by the two models, including the Fe I fluorescence and the Compton reflection in a consistent geometry. The derived physical parameters, such as the WD mass and mass accretion rate, are in a reasonable range in comparison to their classical WD binary counterparts. Additional pieces of evidence in the X-ray spectra (partial covering, Fe L lines, and Fe I fluorescence) were not conclusive enough to classify these two sources into a sub-class of accreting WD binaries. We discuss further observations, especially long-term temporal behaviors, which are important to elucidate the nature of these sources more if indeed they host accreting WDs.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
