ترغب بنشر مسار تعليمي؟ اضغط هنا

XMM-Newton Spectroscopy of the Highly Polarized and Luminous Broad Absorption Line Quasar CSO 755

540   0   0.0 ( 0 )
 نشر من قبل Ohad Shemmer
 تاريخ النشر 2005
  مجال البحث فيزياء
والبحث باللغة English
 تأليف O. Shemmer




اسأل ChatGPT حول البحث

We present the results from XMM-Newton observations of the highly optically polarized broad absorption line quasar (BALQSO) CSO 755. By analyzing its X-ray spectrum with a total of ~3000 photons we find that this source has an X-ray continuum of `typical radio-quiet quasars, with a photon index of Gamma=1.83^{+0.07}_{-0.06}, and a rather flat (X-ray bright) intrinsic optical-to-X-ray spectral slope of alpha_ox=-1.51. The source shows evidence for intrinsic absorption, and fitting the spectrum with a neutral-absorption model gives a column density of N_H~1.2x10^{22} cm^{-2}; this is among the lowest X-ray columns measured for BALQSOs. We do not detect, with high significance, any other absorption features in the X-ray spectrum. Upper limits we place on the rest-frame equivalent width of a neutral (ionized) Fe Ka line, <=180 eV (<=120 eV), and on the Compton-reflection component parameter, R<=0.2, suggest that most of the X-rays from the source are directly observed rather than being scattered or reflected; this is also supported by the relatively flat intrinsic alpha_ox we measure. The possibility that most of the X-ray flux is scattered due to the high level of UV-optical polarization is ruled out. Considering data for 46 BALQSOs from the literature, including CSO 755, we have found that the UV-optical continuum polarization level of BALQSOs is not correlated with any of their X-ray properties. A lack of significant short- and long-term X-ray flux variations in the source may be attributed to a large black-hole mass in CSO 755. We note that another luminous BALQSO, PG 2112+059, has both similar shallow C IV BALs and moderate X-ray absorption.



قيم البحث

اقرأ أيضاً

91 - Patrick B. Hall 2006
I report the discovery of blueshifted broad absorption line (BAL) troughs in at least six transitions of the Balmer series of hydrogen (Hbeta to H9) and in CaII, MgII and excited FeII in the quasar SDSS J125942.80+121312.6. This is only the fourth ac tive galactic nucleus known to exhibit Balmer absorption, all four in conjunction with low-ionization BAL systems containing excited Fe II. The substantial population in the n=2 shell of H I in this quasars absorber likely arises from Ly-alpha trapping. In an absorber sufficiently optically thick to show Balmer absorption, soft X-rays from the quasar penetrate to large tau_Lyalpha and ionize H I. Recombination then creates Ly-alpha photons that increase the n=2 population by a factor tau_Lyalpha since they require about tau_Lyalpha scatterings to diffuse out of the absorber. Observing Ly-alpha trapping in a quasar absorber requires a large but Compton-thin column of gas along our line of sight which includes substantial H I but not too much dust. Presumably the rarity of Balmer-line BAL troughs reflects the rarity of such conditions in quasar absorbers.
Despite extensive efforts, only two quasars have been found at $z>7$ to date due to a combination of low spatial density and high contamination from more ubiquitous Galactic cool dwarfs in quasar selection. This limits our current knowledge of the su per-massive black hole (SMBH) growth mechanism and reionization history. In this letter, we report the discovery of a luminous quasar at $z=7.021$, DELS J003836.10$-$152723.6 (hereafter J0038$-$1527), selected using photometric data from DESI Legacy imaging Survey (DELS), Pan-STARRS1 (PS1) imaging Survey, as well as Wide-field Infrared Survey Explore ($WISE$) mid-infrared all-sky survey. With an absolute magnitude of $M_{1450}$=$-$27.1 and bolometric luminosity of $L_{rm Bol}$=5.6$times$10$^{13}$ $L_odot$, J0038$-$1527 is the most luminous quasar known at $z>7$. Deep optical to near infrared spectroscopic observations suggest that J0038-1527 hosts a 1.3 billion solar mass BH accreting at the Eddington limit, with an Eddington ratio of 1.25$pm$0.19. The CIV broad emission line of J0038$-$1527 is blue-shifted by more than 3000 km s$^{-1}$ to the systemic redshift. More detailed investigations of the high quality spectra reveal three extremely high velocity CIV broad absorption lines (BALs) with velocity from 0.08 to 0.14 times the speed of light and total balnicity index of more than 5000 km s$^{-1}$, suggesting the presence of relativistic outflows. J0038$-$1527 is the first quasar found at the epoch of reionization (EoR) with such strong outflows and provides a unique laboratory to investigate AGN feedback on the formation and growth of the most massive galaxies in the early universe.
117 - M. Diaz Trigo 2012
We analysed data from five XMM-Newton observations of GX 13+1 to investigate the variability of the photo-ionised absorber present in this source. We fitted EPIC and RGS spectra obtained from the least-variable intervals with a model consisting of di sc-blackbody and blackbody components together with a Gaussian emission feature at ~6.55-6.7 keV modified by absorption due to cold and photo-ionised material. We found a significant correlation between the hard, ~6-10 keV, flux, the ionisation and column density of the absorber and the equivalent width of the broad iron line. We interpret the correlation in a scenario in which a disc wind is thermally driven at large, ~10^{10} cm, radii and the broad line results from reprocessed emission in the wind and/or hot atmosphere. The breadth of the emission line is naturally explained by a combination of scattering, recombination and fluorescence processes. We attribute the variations in the absorption and emission along the orbital period to the view of different parts of the wind, possibly located at slightly different inclination angles. We constrain the inclination of GX 13+1 to be between 60 and 80 degrees from the presence of strong absorption in the line of sight, that obscures up to 80% of the total emission in one observation, and the absence of eclipses. We conclude that the presence of a disc wind and/or a hot atmosphere can explain the current observations of narrow absorption and broad iron emission features in neutron star low mass X-ray binaries as a class.
Broad absorption lines (BALs) in quasar spectra identify high velocity outflows that likely exist in all quasars and could play a major role in feedback to galaxy evolution. Studying the variability in these BALs can help us understand the structure, evolution, and basic physical properties of these outflows. We are conducting a BAL monitoring program, which so far includes 163 spectra of 24 luminous quasars, covering time-scales from sim 1 week to 8 years in the quasar rest-frame. We investigate changes in both the CIV {lambda}1550 and SiIV {lambda}1400 BALs, and we report here on some of the results from this program.
CRTS J084133.15+200525.8 is an optically bright quasar at z=2.345 that has shown extreme spectral variability over the past decade. Photometrically, the source had a visual magnitude of V~17.3 between 2002 and 2008. Then, over the following five year s, the source slowly brightened by approximately one magnitude, to V~16.2. Only ~1 in 10,000 quasars show such extreme variability, as quantified by the extreme parameters derived for this quasar assuming a damped random walk model. A combination of archival and newly acquired spectra reveal the source to be an iron low-ionization broad absorption line (FeLoBAL) quasar with extreme changes in its absorption spectrum. Some absorption features completely disappear over the 9 years of optical spectra, while other features remain essentially unchanged. We report the first definitive redshift for this source, based on the detection of broad H-alpha in a Keck/MOSFIRE spectrum. Absorption systems separated by several 1000 km/s in velocity show coordinated weakening in the depths of their troughs as the continuum flux increases. We interpret the broad absorption line variability to be due to changes in photoionization, rather than due to motion of material along our line of sight. This source highlights one sort of rare transition object that astronomy will now be finding through dedicated time-domain surveys.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا