- ID:
- ivo://CDS.VizieR/J/AJ/159/245
- Title:
- Xinglong optical spectra of UGC3223 in 4 epochs
- Short Name:
- J/AJ/159/245
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The discovery of spectral type transition of active galactic nuclei (AGNs), the so-called "changing-look" (CL) phenomenon, challenges the widely accepted AGN paradigm, not only in the orientation-based unified model, but also in the standard disk model. In past decades, only a couple of nearby repeat changing-look active galactic nuclei (CL-AGNs) have been identified. Here we report spectroscopic observations of UGC3223 over the course of 18yr, from 2001 onwards. Combining the spectrum taken in 1987 by Stirpe, we have witnessed its type transitions from 1.5 to 2.0 to 1.8 over 32yr, and captured a long-lived (at least 10 yr) thorough "turn-off" state with a spectrum typical of a Seyfert 2 galaxy. The long-term thorough turn-off state probably suggests a once-dormant and an awakening central engine in UGC3223. We argue that the (dis)appearance of the broad Balmer emission lines can be explained by the disk-wind broad-line region model given the evolution of the calculated Eddington ratio of accretion of the supermassive black hole.
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- ID:
- ivo://CDS.VizieR/J/ApJ/887/15
- Title:
- Xinglong spectra of two changing-look SDSS AGNs
- Short Name:
- J/ApJ/887/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a spectroscopic identification of two new changing-look active galactic nuclei (CL-AGNs): SDSSJ104705.16+544405.8 and SDSSJ120447.91+170256.8, both with a "turn-off" type transition from type-1 to type-1.8/1.9. The identification is arrived at through a follow-up spectroscopic observation of the five CL-AGNs candidates that are extracted from the sample recently released in MacLeod+ (2019, J/ApJ/874/8). The candidates are extracted by the authors from the Sloan Digit Sky Survey Data Release 7, and are spectroscopically confirmed quasars with large amplitude variability. By compiling a sample of 26 previously identified CL-AGNs, we confirm the claim by MacLeod+ that CL-AGNs tend to be biased against a low Eddington ratio, and identify an overlap between the CL-AGNs at their dim state and the so-called intermediate-type AGNs. The overlap implies that there two populations of the intermediate-type AGNs with different origins. One is due to the torus orientation effect, and the other to the intrinsic change of the accretion rate of the central supermassive black holes.
- ID:
- ivo://CDS.VizieR/J/A+A/594/A55
- Title:
- xi Tau UBV and MOST light curves
- Short Name:
- J/A+A/594/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Compact hierarchical systems are important because the effects caused by the dynamical interaction among its members occur ona human timescale. These interactions play a role in the formation of close binaries through Kozai cycles with tides. One such system is xi Tauri: it has three hierarchical orbits: 7.14d (eclipsing components Aa, Ab), 145d (components Aa+Ab, B), and 51yr (components Aa+Ab+B, C). We aim to obtain physical properties of the system and to study the dynamical interaction between its components. Our analysis is based on a large series of spectroscopic photometric (including space-borne) observations and long-baseline optical and infrared spectro-interferometric observations. We used two approaches to infer the system properties: a set of observation-specific models, where all components have elliptical trajectories, and an N-body model, which computes the trajectory of each component by integrating Newton's equations of motion.
- ID:
- ivo://CDS.VizieR/J/A+A/539/A48
- Title:
- XMM AGN optical-UV luminosities
- Short Name:
- J/A+A/539/A48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Active galactic nuclei (AGN) emit radiation over a wide range of wavelengths, with a peak of emission in the far-UV region of the electromagnetic spectrum, a spectral region that is historically difficult to observe. Using optical, GALEX UV, and XMM-Newton data we derive the spectral energy distribution (SED) from the optical/UV to X-ray regime of a sizeable sample of AGN. The principal motivation is to investigate the relationship between the optical/UV emission and the X-ray emission and provide bolometric corrections to the hard X-ray (2-10keV) energy range, k_bol_, the latter being a fundamental parameter in current physical cosmology.
- ID:
- ivo://CDS.VizieR/J/PAZh/42/313
- Title:
- 3XMM-DR4 QSO candidates at 3<z<5.5
- Short Name:
- J/PAZh/42/313
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalog of quasar candidates at redshifts 3<z<5.5 is presented. These candidates have been selected among X-ray sources in the XMM-Newton Serendipitous Source Catalog (3XMM-DR4) in the 0.5-2keV band, located at high galactic latitudes |b|>20deg in the Sloan Digital Sky Survey (SDSS) area. The total overlapping area is about 300 sq. deg. The SDSS, 2MASS and WISE photometric catalogs were used. Only SDSS point sources were considered. X-ray sources having an optical counterpart with magnitude error in SDSS z band of less than 0.2 and color i-z<0.6 were chosen. Their photometric redshifts were determined with the EAZY code using a library of spectral templates. A sample of quasar candidates with photometric redshifts in the range 2.75<z<5.5 has been composed. Objects whose spectral energy distributions are better described by stellar templates have been excluded. The selection completeness of known quasars is about 80%. The normalized median absolute deviation of the differences between the photometric and spectroscopic redshifts of known quasars is 0.07 (with 9% outliers). The sky density of quasar candidates in our sample is 1.5 times that of the spectroscopic SDSS sample in the same fields. Follow-up spectroscopy should clarify the purity of the sample.
- ID:
- ivo://CDS.VizieR/J/PAZh/45/464
- Title:
- 3XMM-DR4 QSO candidates optical spectroscopy
- Short Name:
- J/PAZh/45/464
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We present the results of optical spectroscopy for 58 quasar candidates at photometric redshifts z>~3, 57 of which enter into the Khorunzhev et al. (2016, Cat. J/PAZh/42/313) catalog (K16). This is a catalog of quasar candidates and known type 1 quasars selected among the X-ray sources of the 3XMM-DR4 catalog of the XMM-Newton serendipitous survey. At first we have performed spectroscopy for a quasi-random sample of 19 candidates at the 1.6-m AZT-33IK telescope of the Sayan Solar Observatory and the 6-m BTA telescope of the Special Astrophysical Observatory (SAO RAS). Then we have continued the observation for 39 X-ray bright candidates that could be used for the X-ray luminosity function construction (see Khorunzhev et al. 2018AstL...44..500K). The spectra at AZT-33IK were taken with the new low- and medium-resolution ADAM spectrograph that was produced and installed on the telescope in 2015. One of the most distant (z=5.08) optically bright (i=21) quasars ever detected in X-ray surveys has been discovered.
- ID:
- ivo://CDS.VizieR/J/A+A/527/A126
- Title:
- 2XMMi/SDSS DR7 cross-correlation
- Short Name:
- J/A+A/527/A126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Survey Science Centre of the XMM-Newton satellite released the first incremental version of the 2XMM catalogue in August 2008. Containing more than 220000 X-ray sources, the 2XMMi was at that time the largest catalogue of X-ray sources ever published and thus constitutes an unprecedented resource for studying the high-energy properties of various classes of X-ray emitters such as AGN and stars. Thanks to the high throughput of the EPIC cameras on board XMM-Newton accurate positions, fluxes, and hardness ratios are available for a substantial fraction of the X-ray detections. The advent of the 7th release of the Sloan Digital Sky Survey offers the opportunity to cross-match two major surveys and extend the spectral energy distribution of many 2XMMi sources towards the optical bands. This implies building extensive homogeneous samples with a statistically controlled rate of spurious matches and completeness. We here present a cross-matching algorithm based on the classical likelihood ratio estimator. The method developed has the advantage of providing true probabilities of identifications without resorting to heavy Monte-Carlo simulations.
- ID:
- ivo://CDS.VizieR/J/A+A/490/879
- Title:
- XMM-LSS field optical identifications
- Short Name:
- J/A+A/490/879
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The XMM-Large Scale Structure survey field (XMM-LSS) is an extragalactic window surveyed in the X-ray with the XMM-Newton satellite. It has also been observed in the optical with the Canada-France Hawaii Telescope (CFHTLS survey), and in the infrared with the Spitzer Space Telescope (SWIRE survey). These surveys have been carried out to study the structure and evolution of both baryonic and dark matter on cosmological scales. In two previous papers, we presented deep low frequency radio surveys of the XMM-LSS field, with limiting flux density levels of ~4 and ~1.5mJy/beam at 325 and 610MHz respectively (5{sigma}). These radio surveys were motivated by the need to understand the various connections between the host galaxies of radio sources and their environments. In this paper, we identify optical counterparts to the low frequency radio sources, using the CFHTLS optical catalogue and images, that have an i-band limiting magnitude of i_AB_~25.
- ID:
- ivo://CDS.VizieR/J/A+A/459/199
- Title:
- XMM-Newton survey of two Upper Scorpius regions
- Short Name:
- J/A+A/459/199
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We studied X-ray emission from young stars by analyzing the deep XMM-Newton observations of two regions of the Upper Scorpius association with an age of 5Myr. Based on near infrared and optical photometry we identified 22 Upper Scorpius photometric members among the 224 detected X-ray sources. We derived coronal properties of Upper Scorpius stars by performing X-ray spectral and timing analyses. The study of four strong and isolated stellar flares allowed us to derive the length of the flaring loops.
- ID:
- ivo://CDS.VizieR/J/A+A/395/499
- Title:
- XMM observations in M8 and NGC6530
- Short Name:
- J/A+A/395/499
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of an XMM-Newton observation of the Lagoon Nebula (M 8). Our EPIC images of this region reveal a cluster of point sources, most of which have optical counterparts inside the very young open cluster NGC 6530. The bulk of these X-ray sources are probably associated with low and intermediate mass pre-main sequence stars.
