Is HE 0436-4717 Anemic? A deep look at a bare Seyfert 1 galaxy

A multi-epoch, multi-instrument analysis of the Seyfert 1 galaxy HE 0436-4717 is conducted using optical to X-ray data from XMM-Newton and Swift (including the BAT). Fitting of the UV-to-X-ray spectral energy distribution shows little evidence of extinction and the X-ray spectral analysis does not confirm previous reports of deep absorption edges from OVIII. HE 0436-4717 is a "bare" Seyfert with negligible line-of-sight absorption making it ideal to study the central X-ray emitting region. Three scenarios were considered to describe the X-ray data: partial covering absorption, blurred reflection, and soft Comptonization. All three interpretations describe the 0.5-10.0 keV spectra well. Extrapolating the models to 100 keV results in poorer fits for the the partial covering model. When also considering the rapid variability during one of the XMM-Newton observations, the blurred reflection model appears to describe all the observations in the most self-consistent manner. If adopted, the blurred reflection model requires a very low iron abundance in HE 0436-4717. We consider the possibilities that this is an artifact of the fitting process, but it appears possible that it is intrinsic to the object.Comment: 7 tables, 11 figures, 16 pages; accepted for publication in MNRAS 17 Feb. 201

Properties of AGN coronae in the NuSTAR era

The focussing optics of NuSTAR have enabled high signal-to-noise spectra to be obtained from many X-ray bright Active Galactic Nuclei (AGN) and Galactic Black Hole Binaries (BHB). Spectral modelling then allows robust characterization of the spectral index and upper energy cutoff of the coronal power-law continuum, after accounting for reflection and absorption effects. Spectral-timing studies, such as reverberation and broad iron line fitting, of these sources yield coronal sizes, often showing them to be small and in the range of 3 to 10 gravitational radii in size. Our results indicate that coronae are hot and radiatively compact, lying close to the boundary of the region in the compactness - temperature diagram which is forbidden due to runaway pair production. The coincidence suggests that pair production and annihilation are essential ingredients in the coronae of AGN and BHB and that they control the shape of the observed spectra.Comment: 11 pages, 8 figures, accepted for publication in MNRA

A Killing tensor for higher dimensional Kerr-AdS black holes with NUT charge

In this paper, we study the recently discovered family of higher dimensional Kerr-AdS black holes with an extra NUT-like parameter. We show that the inverse metric is additively separable after multiplication by a simple function. This allows us to separate the Hamilton-Jacobi equation, showing that geodesic motion is integrable on this background. The separation of the Hamilton-Jacobi equation is intimately linked to the existence of an irreducible Killing tensor, which provides an extra constant of motion. We also demonstrate that the Klein-Gordon equation for this background is separable.Comment: LaTeX, 14 pages. v2: Typo corrected and equation added. v3: Reference added, introduction expanded, published versio

The power output of local obscured and unobscured AGN: crossing the absorption barrier with Swift/BAT and IRAS

The Swift/BAT 9-month catalogue of active galactic nuclei (AGN) provides an unbiased census of local supermassive black hole accretion, and probes to all but the highest levels of absorption in AGN. We explore a method for characterising the bolometric output of both obscured and unobscured AGN by combining the hard X-ray data from Swift/BAT (14-195keV) with the reprocessed IR emission as seen with the IRAS all-sky surveys. This approach bypasses the complex modifications to the SED introduced by absorption in the optical, UV and 0.1-10 keV regimes and provides a long-term, average picture of the bolometric output of these sources. We broadly follow the approach of Pozzi et al. for calculating the bolometric luminosities by adding nuclear IR and hard X-ray luminosities, and consider different approaches for removing non-nuclear contamination in the large-aperture IRAS fluxes. Using mass estimates from the M_BH-L_bulge relation, we present the Eddington ratios \lambda_Edd and 2-10 keV bolometric corrections for a subsample of 63 AGN (35 obscured and 28 unobscured) from the Swift/BAT catalogue, and confirm previous indications of a low Eddington ratio distribution for both samples. Importantly, we find a tendency for low bolometric corrections (typically 10-30) for the obscured AGN in the sample (with a possible rise from ~15 for \lambda_Edd<0.03 to ~32 above this), providing a hitherto unseen window onto accretion processes in this class of AGN. This finding is of key importance in calculating the expected local black hole mass density from the X-ray background since it is composed of emission from a significant population of such obscured AGN. Analogous studies with high resolution IR data and a range of alternative models for the torus emission will form useful future extensions to this work. (Abridged)Comment: 19 pages, 16 figures, 2 tables. Accepted for publication in MNRA

The hard X-ray perspective on the soft X-ray excess

The X-ray spectra of many active galactic nuclei (AGN) exhibit a `soft excess' below 1keV, whose physical origin remains unclear. Diverse models have been suggested to account for it, including ionised reflection of X-rays from the inner part of the accretion disc, ionised winds/absorbers, and Comptonisation. The ionised reflection model suggests a natural link between the prominence of the soft excess and the Compton reflection hump strength above 10keV, but it has not been clear what hard X-ray signatures, if any, are expected from the other soft X-ray candidate models. Additionally, it has not been possible up until recently to obtain high-quality simultaneous measurements of both soft and hard X-ray emission necessary to distinguish these models, but upcoming joint XMM-NuSTAR programmes provide precisely this opportunity. In this paper, we present an extensive analysis of simulations of XMM+NuSTAR observations, using two candidate soft excess models as inputs, to determine whether such campaigns can disambiguate between them by using hard and soft X-ray observations in tandem. The simulated spectra are fit with the simplest "observer's model" of a black body and neutral reflection to characterise the strength of the soft and hard excesses. A plot of the strength of the hard excess against the soft excess strength provides a diagnostic plot which allows the soft excess production mechanism to be determined in individual sources and samples using current state-of-the-art and next generation hard X-ray enabled observatories. This approach can be straightforwardly extended to other candidate models for the soft excess.Comment: 12 pages, 11 figures, accepted for publication in ApJ. Added reference

Hidden Symmetry of Higher Dimensional Kerr-NUT-AdS Spacetimes

It is well known that 4-dimensional Kerr-NUT-AdS spacetime possesses the hidden symmetry associated with the Killing-Yano tensor. This tensor is "universal" in the sense that there exist coordinates where it does not depend on any of the free parameters of the metric. Recently the general higher dimensional Kerr-NUT-AdS solutions of the Einstein equations were obtained. We demonstrate that all these metrics with arbitrary rotation and NUT parameters admit a universal Killing-Yano tensor. We give an explicit presentation of the Killing-Yano and Killing tensors and briefly discuss their properties.Comment: 4 pages, some discussion and references are adde

Thyroid Dysfunction in Chronic Renal Failure

INTRODUCTION: “The world is facing a global pandemic of chronic kidney disease. As the morbidity and mortality from infectious diseases decline, life expectancy increases and chronic degenerative diseases have become more prevalent. CKD is unique amongst the chronic non-infectious illnesses…..”. It has been estimated from population survey data that atleast 6% of the adult population in the United States has CKD at stages 1 and 2. An unknown subset of this group will progress to more advanced stages of CKD. An additional 4.5% of the U.S. population is estimated to have stages 3 and 4 CKD. The most frequent cause of CKD is diabetic Nephropathy, most often secondary to Type 2 DM. India being the diabetic capital of the world, diabetic Nephropathy is the commonest cause of CKD. There are about 7.85 million CKD patients in India. Patients with End Stage Renal Disease display a variety of endocrine disturbances. However the evidence of endocrine dysfunction commonly consists only of laboratory abnormalities, many of which are not associated with apparent clinical signs and symptoms of the disease.4 Among which Thyroid function has been extensively evaluated in patients with CRF. CRF is a widely recognised cause of nonthyroidal illness causing thyroid dysfunction, ie, alteration in thyroid hormones in the absence of underlying intrinsic thyroid disorder. Chronic renal failure affects thyroid function in multiple ways, including low circulating thyroid hormone concentration, altered peripheral hormone metabolism, disturbed binding to carrier proteins, possible reduction in tissue thyroid content and increased iodine stores in thyroid glands. TT3, TT4, FT3 are decreased more commonly in patients with CRF. But FT4, TSH levels are normal in these patients and indicate euthyroid status. We speculate that the low thyroid state in uremia serves to defend against protein wasting and misguided attempts to replete thyroid hormone stores may worsen protein malnutrition. Some studies showed an increased incidence of subclinical hypothyroidism in CKD patients and higher prevalence of hypothyroidism in patients with terminal renal failure. It has been estimated that primary hypothyroidism may occur in upto 9.5% of ESRD patients when compared to 0.6 to 1.1% of general population. When hypothyroidism becomes more severe it can cause reduced cardiac function and lead to progressively worsening kidney function. Thus the prevalence of subclinical hypothyroidism in patients with CKD might be a risk factor for both cardiovascular disease and progressive kidney disease. This study is designed to determine the prevalence of thyroid dysfunction in CRF patients in order to intervene at an early stage depending upon the hormone abnormalities and reduce both the cardiovascular risk and progressive worsening of kidney function. AIM OF THE STUDY: 1. To determine the prevalence of thyroid dysfunction in chronic renal failure patients in stages 3,4 and 5. 2. To correlate the prevalence of thyroid hormone abnormalities with increasing degrees of renal insufficiency. MATERIALS AND METHODS: Subjects: Patients admitted in the Department of Medicine and Nephrology who fulfilled the Inclusion and Exclusion Criteria. Study design: Cross sectional study. Study setting: Govt. Rajaji Hospital, Madurai. Study Duration: August 2008 to October 2009. Study Criteria: Inclusion Criteria: Newly detected CRF patients with chronic renal insufficiency defined as; 1. An estimated creatinine clearance of < 60 ml/mt. (Stages 3,4 & 5), 2. USG evidence of chronic renal failure. Exclusion Criteria: 1. Previously known hypothyroid patients, 2. Patients on high dose of frusemide therapy > 100 mg/day, 3. On heparin therapy, 4. On steroid therapy, 5. On antiepileptics like phenytoin, phenobarbitone, 6. On sulphonylureas, 7. On propranolol. RESULTS: Most of the patients in the sample were in the age group of 51-60 years. The range was from 23 to 75 years. Of the 40 patients in the sample 30 patients were males, and 10 patients were females. Of the 40 patients with CRF, 11 patients (27.5%) were diabetic. Of the 40 patients with CRF, 8 patients (20%) only were symptomatic and majority (80%) were asymptomatic. Of the 40 patients with CRF, 7 patients (17.5%) had goiter. Of the 40 patients in this sample, 6 patients belonged to stage 3, 11 patients to stage 4 and 23 patients to stage 5. The Table shows that symptoms of hypothyroidism are prominent with advanced stages of renal failure. Of the 40 patients in this sample, 3 patients (7.5%) had hypothyroidism, 6 patients (15%) had subclinical hypothyroidism, 17 patients (42.5) had some thyroid hormone abnormalities. Totally 26 patients (65%) had some thyroid dysfunction. Of the 40 patients in this study group 23 patients had stage 5CKD. The prevalence of goiter was 0% in stage 3 CKD, 9.1% in stage 4 CKD and 26.1% in stage 5 CKD. The higher the stage of CKD, the higher was the prevalence of goiter. CONCLUSION: In our study, the overall prevalence of thyroid dysfunction is 65% in patients with chronic kidney disease. • 7.5% of CKD patients had hypothyroidism. • 15% had subclinical hypothyrodism. • 42.5% had some thyroid hormone abnormalities. • 17.5% of CKD patients had goiter. There was a significant correlation between the prevalence of thyroid dysfunction and the stage of chronic kidney disease. • Higher the degree of renal insufficiency, the higher was the prevalence of thyroid hormone abnormalities