39 research outputs found
The Habitability of the Galactic Bulge
We present a new investigation of the habitability of the Milky Way bulge,
that expands previous studies on the Galactic Habitable Zone. We discuss
existing knowledge on the abundance of planets in the bulge, metallicity and
the possible frequency of rocky planets, orbital stability and encounters, and
the possibility of planets around the central supermassive black hole. We focus
on two aspects that can present substantial differences with respect to the
environment in the disk: (i) the ionizing radiation environment, due to the
presence of the central black hole and to the highest rate of supernovae
explosions and (ii) the efficiency of putative lithopanspermia mechanism for
the diffusion of life between stellar systems. We use analytical models of the
star density in the bulge to provide estimates of the rate of catastrophic
events and of the diffusion timescales for life over interstellar distances.Comment: Published in Lif
Stark Broadening in Compact Stars: Xe VI Lines
International audienceWe will consider Stark broadening of non hydrogenic spectral lines in the impact approximation in compact stars: pre-white dwarf and white dwarf atmospheres. In order to show an example, Stark broadening parameters have been calculated, using the impact semiclassical perturbation approach for four Xe VI spectral lines. Obtained results have been used to demonstrate the influence of Stark broadening in DA and DB white dwarf atmospheres
Determination of Ceres mass based on the most gravitationally efficient close encounters
Here is presented recalculated value of the mass of Ceres, based on explicit
tracking of its gravitational influence on orbits evolution of 21 selected
asteroids during their mutual close encounters (CE). It was applied a new
modified method (MM) for mass determination, based on the connecting of
pre-encounter observations to the orbit determined from post-encounter ones.
The calculated weighted mean value of Ceres mass, based on modified method, is
while standard procedure (SM) provided
result of . We found that correlation between
individual estimated masses based on modified and standard method is 0.78,
which confirms reliability of using modified method.Comment: MNRAS:Accepted 2011 September 28. Received 2011 September 28; in
original form 2011 January 2
Long-term monitoring of the broad-line region properties in a selected sample of AGN
We present the results of the long-term optical monitoring campaign of active
galactic nuclei (AGN) coordinated by the Special Astrophysical Observatory of
the Russian Academy of Science. This campaign has produced a remarkable set of
optical spectra, since we have monitored for several decades different types of
broad-line (type 1) AGN, from a Seyfert 1, double-peaked line, radio loud and
radio quiet AGN, to a supermassive binary black hole candidate. Our analysis of
the properties of the broad line region (BLR) of these objects is based on the
variability of the broad emission lines. We hereby give a comparative review of
the variability properties of the broad emission lines and the BLR of seven
different type 1 AGNs, emphasizing some important results, such as the
variability rate, the BLR geometry, and the presence of the intrinsic Baldwin
effect. We are discussing the difference and similarity in the continuum and
emission line variability, focusing on what is the impact of our results to the
supermassive black hole mass determination from the BLR properties.Comment: Published in Frontiers in Astronomy and Space Scienc
Stark broadening of B IV lines for astrophysical and laboratory plasma research
Stark broadening parameters for 36 multiplets of B IV have been calculated
using the semi-classical perturbation formalism. Obtained results have been
used to investigate the regularities within spectral series and temperature
dependence.Comment: 8 pages, 6 figures, 1 table, in press in Advances in Space Researc
Stark broadening of B IV spectral lines
Stark broadening parameters for 157 multiplets of helium like boron (B IV)
have been calculated using the impact semiclassical perturbation formalism.
Obtained results have been used to investigate the regularities within spectral
series. An example of the influence of Stark broadening on B IV lines in DO
white dwarfs is given.Comment: 6 pages, 2 figure
Long-Term Optical Monitoring of Broad-Line AGNs (LoTerm AGN): Case Study of NGC 3516
Properties of the broad line region (BLR) in active galactic nuclei (AGNs) are commonly used to estimate the mass of the supermassive black hole (SMBH) that powers an AGN. However, the understanding of the physics behind the BLR remains incomplete. The AGNs exhibit strong optical variability, observed in the change of the profiles and fluxes of broad emission lines. Utilizing this variability provides an opportunity to constrain the physics of the BLR, and understand the interplay of the BLR with SMBH and surrounding regions. Here, we present the long-term monitoring campaign of a sample of the known broad-line AGNs (identified as LoTerm AGN). The aim of this study is to show the importance of sustained and dedicated campaigns that continually collect spectroscopic data of the known AGNs over extended timescales, providing unique insight into the origin and structure of the BLR. LoTerm AGN is a collaborative network of seven moderate-size telescopes equipped for spectroscopy. We focus on the recent spectral data of the known changing-look AGN, NGC 3516. Specifically, we examine the broad hydrogen Balmer Hα line observed in the period 2020–2023, demonstrating that this AGN remains active with the BLR signatures observed in the spectra. No significant change in the broad line profile of Hα line is observed during this recent period
The LSST Era of Supermassive Black Hole Accretion Disk Reverberation Mapping
peer reviewedThe Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) will detect an unprecedentedly large sample of actively accreting supermassive black holes with typical accretion disk (AD) sizes of a few light days. This brings us to face challenges in the reverberation mapping (RM) measurement of AD sizes in active galactic nuclei using interband continuum delays. We examine the effect of LSST cadence strategies on AD RM using our metric AGN_TimeLagMetric. It accounts for redshift, cadence, the magnitude limit, and magnitude corrections for dust extinction. Running our metric on different LSST cadence strategies, we produce an atlas of the performance estimations for LSST photometric RM measurements. We provide an upper limit on the estimated number of quasars for which the AD time lag can be computed within 0 1000 sources in each deep drilling field (DDF; (10 deg2)) in any filter, with the redshift distribution of these sources peaking at z ≍ 1. We find the LSST observation strategies with a good cadence (≲5 days) and a long cumulative season (~9 yr), as proposed for LSST DDF, are favored for the AD size measurement. We create synthetic LSST light curves for the most suitable DDF cadences and determine RM time lags to demonstrate the impact of the best cadences based on the proposed metric