arXiv subjects

Hector Aceves

Publications and source records attributed to Hector Aceves.

At least 19 recordsLinked to original sources

arXiv2025

BSN-V: The First Detailed Light Curve Modeling of Eight Totally Eclipsing Contact Binary Stars Using Ground-Based and TESS Observations

This study broadens our comprehensive investigation of total-eclipse W Ursae Majoris-type contact binaries by analyzing eight additional systems, continuing our previous research. Multiband $BVR_cI_c$ photometric data were obtained at an observatory in Mexico, from which new times of minima were determined. All target systems also had available space-based TESS time-series data. Orbital period variations were studied for eight target systems, showing either linear or parabolic trends. The target systems exhibiting parabolic trends demonstrated a sustained decrease in their orbital periods over time. We modeled the light curves utilizing the PHOEBE Python code in combination with the BSN application. We revisited the relationship between orbital period and the temperature of the hotter component in contact binary systems using an empirical approach. Our analysis identified a clear break at P=0.27 days, separating the systems into two distinct groups for orbital periods shorter than 0.6 days. Following the determination of stellar extinction, absolute parameters for seven systems were estimated employing parallax measurements from Gaia DR3. Based on the components' effective temperatures and masses, the systems were classified into A- and W-subtypes. Their evolutionary states were illustrated using mass-radius and mass-luminosity diagrams.

astro-ph.SR↗

arXiv2025

BSN-IV: The First Multiband Light Curve Study of Five W UMa-type Contact Binary Systems

In this work, we present a detailed investigation of five contact binary systems of the W Ursae Majoris (W UMa) type. Multiband photometric observations were conducted using ground-based telescopes in both the northern and southern hemispheres, yielding new times of minima. O-C diagram analysis reveals that two systems exhibit parabolic trends, indicating a gradual long-term decrease in their orbital periods. The light curves were modeled using version 1.0 of the BSN application, with one system requiring the inclusion of a cool starspot to achieve a satisfactory fit. We examined empirical relationships between orbital period and fundamental parameters, identifying the period-semi-major axis (P-a) relation as the most robust correlation, which was used to estimate absolute parameters. To statistically assess thermal equilibrium, we analyzed temperature differences between components and found that 90% of systems exhibit less than 9.4% contrast. Two target systems with extremely low mass ratios were identified, and their orbital stability was evaluated. Based on the effective temperatures and component masses, two systems were classified as W-subtype and three as A-subtype. The evolutionary status of the binaries was assessed through their locations in mass-radius, mass-luminosity, and other empirical diagrams, and initial component masses as well as total mass loss were also estimated.

astro-ph.SR↗

arXiv2025

BSN-II: The First Light Curve Study of Eight Total Eclipsing Contact Binary Stars with Shallow Fillout Factors

This study provides the first comprehensive analysis of eight total-eclipse W Ursae Majoris-type contact binary systems. Ground-based photometric multiband observations were conducted at a Mexican observatory, and new times of minima were extracted. The O-C analysis reveals that four of our target binaries exhibit a long-term increase in their orbital periods, while the others show a long-term decrease in their orbital periods. We analyzed the light curves using the PHOEBE Python code and BSN application. Among the target systems, two required the inclusion of a cold starspot on one of the components to achieve an adequate fit. The light curve analysis revealed that the target systems exhibit a shallow fillout factor. Absolute parameters were estimated using the Gaia DR3 parallax and astrophysics equations. Considering the effective temperatures and component masses, each system was classified as either the A- or W-subtype. The stellar evolution of the systems was represented through the mass-radius and mass-luminosity diagrams. Additionally, we calculated the initial masses of the companion stars and the total mass lost for each target system.

astro-ph.SR↗

arXiv2025

BSN-III: The First Multiband Photometric Study on the Eight Total Eclipse Contact Binary Stars

This study continues our in-depth investigation of total-eclipse W Ursae Majoris-type contact binaries by analyzing eight new systems, complementing our previous work. Multiband $BVR_cI_c$ photometric data were acquired through ground-based observations at an observatory in Mexico, from which new times of minima were determined. Our analysis of orbital period variations using the O-C method revealed that one system shows no long-term variation, four systems exhibit a secular decrease in their orbital periods, and two systems exhibit a secular increase, suggesting mass transfer between the components. Notably, one system displays a cyclic variation with an amplitude of 0.00865 days and a period of 10.49 years, which we attribute to the light travel time effect induced by a tertiary companion, possibly a brown dwarf. We modeled the light curves using the PHOEBE Python code. Six of the target systems required the inclusion of a cold starspot on one of the system's stars due to the asymmetry observed in the maxima of their light curves. Absolute parameters were estimated using the Gaia DR3 parallax method. Using the components' effective temperatures and masses, we classified five of the systems as W-subtype and three as A-subtype. The stellar evolution was illustrated through the mass-radius and mass-luminosity diagrams. Furthermore, we investigated the dynamical stability of two systems with extremely low mass ratios.

astro-ph.SR↗

arXiv2025

Exploring the halo occupation distribution for moderate X-ray luminosity active galactic nuclei in the EAGLE cosmological simulation

The hydrodynamical cosmological simulation \eagle{} is used to model the Halo Occupation Distribution (HOD) of moderate X-ray luminosity active galactic nuclei (mXAGN), extending previous work using only dark matter simulations and empirical relations. By examining mergers as a triggering mechanism, we focus on halos typical of galaxy groups and cluster-like systems with masses $\geq 10^{12.75}\,{\rm M}{\odot}\,h^{-1}$. We analyze simulation data to create catalogs of central and satellite galaxies. We study their merger history we quantify the percentage of minor and major mergers in the mXAGN sample. We obtain the HOD for central and satellite mXAGN across a redshift interval from $z=2$ to the present epoch. Our results indicate that, across most redshifts, minor mergers slightly predominate as the primary mechanism for triggering mXAGN.

astro-ph.GA↗

arXiv2023

Revisiting FS Aurigae and its triple cataclysmic variable system hypothesis

A very long term variability (VLPP), with period of 875 days, was observed in the long-term light curve of FS Aurigae in 2011. This periodicity was calculated on 6 cycles. We re-examine the periodicity with new observations over of the past 5 yrs. A total of 18 yrs of observations confirm the hypothesis of a third body perturbing in a secular way the cataclysmic variable (CV). Improvements to the model such as eccentric and inclined orbits for the third body and a binary post-Newtonian correction are considered. We confirm the VLPP of FS Aur and find the new period of 857 $\pm$ 78 days. The secular perturbations are most efficient when the mass of the third body is M=29 MJ, much less than the 50 MJ reported in 2011. We estimate the effect of the third body on the mass transfer rate and the brightness of the system. We consider alternative scenarios for the VLPP. The new data and analysis supports the hypothesis that FS Aur is a CV in a triple system.

astro-ph.SR↗

arXiv2022

Testing the third body hypothesis in the Cataclysmic Variables LU Camelopardalis, QZSerpentis, V1007 Herculis and BK Lyncis

Some Cataclysmic Variables (CVs) exhibits a very long photometric period (VLPP). We calculate the properties of a hypothetical third body, initially assumed on circular--planar orbit, by matching the modelled VLPP to the observed one of four CVs studied here: {\sl LU Camelopardalis} (LU Cam), QZ Serpentis (QZ Ser), V1007 Herculis (V1007 Her) and BK Lyncis (BK Lyn). The eccentric and low inclination orbits for a third body are considered using analytical results. The chosen parameters of the binary components are based on the orbital period of each CV. The smallest corresponding semi-major axis permitted before the third body's orbit becomes unstable is also calculated. A first-order analytical post-Newtonian correction is applied, and the rate of precession of the pericentre is found, but it can not explain any of the observed VLPP. For the first time, we also estimate the effect of secular perturbations by this hypothetical third body on the mass transfer rate of such CVs. We made sure that the observed and calculated amplitude of variability was comparable too. The mass of the third body satisfying all constrains range from 0.63 to 97 Jupiter masses. Our results show further evidence supporting the hypothesis of a third body in three of these CVs, but only marginally in V1007 Her.

astro-ph.EP↗

arXiv2019

Accretion of Small Satellites and Gas Inflows in a Disc Galaxy

Galaxy interactions can have an important effect in a galaxy's evolution. Cosmological models predict a large number of small satellites around galaxies. It is important to study the effect that these small satellites can have on the host. The present work explores the effect of small N-body spherical satellites with total mass ratios in the range approx 1:1000-1:100 in inducing gas flows to the central regions of a disc galaxy with late-type morphology resembling the Milky Way. Two model galaxies are considered: barred and non-barred models; the latter one is motivated in order to isolate and understand better the effects of the satellite. Several circular and non-circular orbits are explored, considering both prograde and retrogade orientations. We show that satellites with such small mass ratios can still produce observable distortions in the gas and stellar components of the galaxy. In terms of gas flows, the prograde circular orbits are more favourable for producing gas flows, where in some cases up to $60% of the gas of the galaxy is driven to the central region. We find, hence, that small satellites can induce significant gas flows to the central regions of a disc galaxy, which is relevant in the context of fuelling active galactic nuclei.

astro-ph.GA↗

arXiv2017

Spatial clustering and halo occupation distribution modeling of local AGN via cross-correlation measurements with 2MASS galaxies

We present the clustering properties and halo occupation distribution (HOD) modelling of very low redshift, hard X-ray-detected active galactic nuclei (AGN) using cross-correlation function measurements with Two-Micron All Sky Survey galaxies. Spanning a redshift range of $0.007 < z < 0.037$, with a median $z=0.024$, we present a precise AGN clustering study of the most local AGN in the Universe. The AGN sample is drawn from the SWIFT/BAT 70-month and INTEGRAL/IBIS eight year all-sky X-ray surveys and contains both type I and type II AGN. We find a large-scale bias for the full AGN sample of $b=1.04^{+0.10}_{-0.11}$, which corresponds to a typical host dark matter halo mass of $M_{\rm h}^{\rm typ}=12.84^{+0.22}_{-0.30}\,h^{-1} M_{\odot}$. When split into low and high X-ray luminosity and type I and type II AGN subsamples, we detect no statistically significant differences in the large-scale bias parameters. However, there are differences in the small-scale clustering which are reflected in the full HOD model results. We find that low and high X-ray luminosity AGN, as well as type I and type II AGN, occupy dark matter haloes differently, with 3.4$σ$ and 4.0$σ$ differences in their mean halo masses, respectively, when split by luminosity and type. The latter finding contradicts a simple orientation-based AGN unification model. As a by-product of our cross-correlation approach, we also present the first HOD model of 2MASS galaxies.

astro-ph.GA↗

arXiv2016

The radiation energy component of the Hubble function and a LCDM cosmological simulation

We study some effects the inclusion of the radiation energy component in the universe, Omega_r, can have on several quantities of interest for the large-scale structure of the universe in a LCDM cosmological simulation; started at a very high redshift (z=500). In particular we compute the power spectrum density, the halo mass function, and the concentration-mass relation for haloes. We find that Omega_r has an important contribution in the long-term nonlinear evolution of structures in the universe. For instance, a lower matter density power, by approx 50%, in all scales is obtained when compared with a simulation without the radiation term. Also, haloes formed with the Omega_r taken into account are approx 20% less concentrated than when not included in the Hubble function.

astro-ph.CO↗

arXiv2015

The spatial clustering of ROSAT All-Sky Survey Active Galactic Nuclei IV. More massive black holes reside in more massive dark matter halos

This is the fourth paper in a series that reports on our investigation of the clustering properties of active galactic nuclei (AGN) identified in the ROSAT All-Sky Survey (RASS) and Sloan Digital Sky Survey (SDSS). In this paper we investigate the cause of the X-ray luminosity dependence of the clustering of broad-line, luminous AGN at 0.16<z<0.36. We fit the H-alpha line profile in the SDSS spectra for all X-ray and optically-selected broad-line AGN, determine the mass of the super-massive black hole (SMBH), M_BH, and infer the accretion rate relative to Eddington (L/L_EDD). Since M_BH and L/L_EDD are correlated, we create AGN subsamples in one parameter while maintaining the same distribution in the other parameter. In both the X-ray and optically-selected AGN samples we detect a weak clustering dependence with M_BH and no statistically significant dependence on L/L_EDD. We find a difference of up to 2.7sigma when comparing the objects that belong to the 30% least and 30% most massive M_BH subsamples, in that luminous broad-line AGN with more massive black holes reside in more massive parent dark matter halos at these redshifts. These results provide evidence that higher accretion rates in AGN do not necessarily require dense galaxy environments in which more galaxy mergers and interactions are expected to channel large amounts of gas onto the SMBH. We also present semi-analytic models which predict a positive M_DMH dependence on M_BH, which is most prominent at M_BH ~ 10^{8-9} M_SUN.

astro-ph.GA↗

arXiv2014

Intragroup dark matter distribution in small groups of halos in a LCDM cosmology

We study the distribution of intragroup dark matter in small groups of dark matter halos of galaxy-like size in a LCDM cosmology. These groups are identified using a physical criterion and may be an appropriate representation of small galaxy groups. We quantify the amount of intragroup dark matter and characterize its distribution. We find that compact associations of halos, as well as those intermediate and loose groups, have rather flat intragroup dark matter profiles with logarithmic slopes of gamma ~0 and ~-0.2$, respectively. Hence, the intragroup dark matter of these halo systems does not follow the same cuspy tendency that halos of galaxies have. In intermediate and loose galaxy-size halo associations the intragroup matter tends to be <50% that of the total mass of the group, and in compact associations is <20% within their group radius.

astro-ph.CO↗

arXiv2014

Stability of the Outer Planets in Multiresonant Configurations with a Self-gravitating Planetesimal Disk

We study the effect of a massive planetesimal disk on the dynamical stability of the outer planets assuming, as has been suggested recently, that these were initially locked in a compact and multiresonant configuration as a result of gas-driven migration in a protoplanetary disk. The gravitational interaction among all bodies in our simulations is included self-consistently using the Mercury6.5 code. Several initial multiresonant configurations and planetesimal disk models are considered. Under such conditions a strong dynamical instability, manifested as a rapid giant planet migration and planetesimal disk dispersal, develops on a timescale of less than 40 Myr in most cases. Dynamical disk heating due to the gravitational interactions among planetesimals leads to more frequent interactions between the planetesimals and the ice giants Uranus and Neptune, in comparison to models in which planetesitmal-planetesimal interactions are neglected. On account of the rapid evolution of the multiresonant configurations obtained with fully self-consistent simulations, our results are inconsistent with the dynamical instability origin of the Late Heavy Bombardment as currently considered by the Nice model for the Solar System.

astro-ph.EP↗

arXiv2011

The Spatial Clustering of ROSAT All-Sky Survey AGNs III. Expanded Sample and Comparison with Optical AGNs

This is the third paper in a series that reports on our investigation of the clustering properties of AGNs identified in the ROSAT All-Sky Survey (RASS) and Sloan Digital Sky Survey (SDSS). In this paper, we extend the redshift range to 0.07<z<0.50 and measure the clustering amplitudes of both X-ray and optically-selected SDSS broad-line AGNs with and without radio detections as well as for X-ray selected narrow-line RASS/SDSS AGNs. We measure the clustering amplitude through cross-correlation functions (CCFs) with SDSS galaxies and derive the bias by applying a halo occupation distribution (HOD) model directly to the CCFs. We find no statistically convincing difference in the clustering of X-ray and optically-selected broad-line AGNs, as well as with samples in which radio-detected AGNs are excluded. This is in contrast to low redshift optically-selected narrow-line AGNs, where radio-loud AGNs are found in more massive halos than optical AGNs without a radio-detection. The typical dark matter halo masses of our broad-line AGNs are log M_DMH/[h^(-1) M_SUN] ~ 12.4-13.4, consistent with the halo mass range of typical non-AGN galaxies at low redshifts. We find no significant difference between the clustering of X-ray selected narrow-line AGNs and broad-line AGNs. We confirm the weak dependence of the clustering strength on AGN X-ray luminosity at a ~2 sigma level. Finally, we summarize the current picture of AGN clustering to z~1.5 based on three dimensional clustering measurements.

astro-ph.CO↗

arXiv2011

Effects of Magnetic Turbulence on the Dynamics of Pickup Ions in the Ionosheath of Mars

We study some of the effects that magnetic turbulent fluctuations have on the dynamics of pickup O+ ions in the magnetic polar regions of the Mars ionosheath. In particular we study their effect on the bulk velocity profiles of ions as a function of altitude over the magnetic poles, in order to compare them with recent Mars Express data; that indicate that their average velocity is very low and essentially in the anti-sunward direction. We find that, while magnetic field fluctuations do give rise to deviations from simple ExB-drift gyromotion, even fluctuation amplitudes much greater than those of in situ measurements are {\it not} able to reproduce the vertical velocity profile of O+ ions. We conclude that other physical mechanisms, different from a pure charged particle dynamics, are acting on pickup ions at the Martian terminator. A possibility being a viscous-like interaction between the Solar Wind and the Martian ionosphere at low altitudes.

astro-ph.EP↗

arXiv2011

Dynamical Analysis of the 3:1 Resonance in the upsilon-Andromedae System

We study the dynamics of the upsilon-Andromedae planetary system proposed by Curiel et al. (2011). We focus on the study of the 3:1 Mean Motion Resonance between upsilon-Andromedae-d and the recently discovered upsilon-Andromedae-e (hereafter upsilon-And-d and upsilon-And-e). Numerical simulations of the dynamics of the four planet system are conducted. The previously reported apsidal resonance between upsilon-And-c and upsilon-And-d is confirmed. In addition, we find that upsilon-And-d and upsilon-And-e are also in an apsidal resonance condition. Our results further indicate that the upsilon-Andromedae planetary system configuration is in the middle of a stability island in the semimajor axis-eccentricity domain. Additionally, we performed numerical integrations of the planetary configuration over 500 Myr and found it to be stable. We conclude that, within the uncertainties in the value of the orbital parameters, it is likely that upsilon-Andromedae planetary system will remain stable for a long timescale.

astro-ph.EP↗

arXiv2010

The Spatial Clustering of ROSAT All-Sky Survey AGNs II. Halo Occupation Distribution Modeling of the Cross Correlation Function

This is the second paper of a series that reports on our investigation of the clustering properties of AGNs in the ROSAT All-Sky Survey (RASS) through cross-correlation functions (CCFs) with Sloan Digital Sky Survey (SDSS) galaxies. In this paper, we apply the Halo Occupation Distribution (HOD) model to the CCFs between the RASS Broad-line AGNs with SDSS Luminous Red Galaxies (LRGs) in the redshift range 0.16<z<0.36 that was calculated in paper I. In our HOD modeling approach, we use the known HOD of LRGs and constrain the HOD of the AGNs by a model fit to the CCF. For the first time, we are able to go beyond quoting merely a `typical' AGN host halo mass, M_h, and model the full distribution function of AGN host dark matter halos. In addition, we are able to determine the large-scale bias and the mean M_h more accurately. We explore the behavior of three simple HOD models. Our first model (Model A) is a truncated power-law HOD model in which all AGNs are satellites. With this model, we find an upper limit to the slope (α) of the AGN HOD that is far below unity. The other two models have a central component, which has a step function form, where the HOD is constant above a minimum mass, without (Model B) or with (Model C) an upper mass cutoff, in addition to the truncated power-law satellite component, similar to the HOD that is found for galaxies. In these two models we find the upper limits of α< 0.95 and α< 0.84 for Model B and C respectively. Our analysis suggests that the satellite AGN occupation increases slower than, or may even decrease with, M_h, in contrast to the satellite's HODs of luminosity-threshold samples of galaxies, which, in contrast, grow approximately as \propto M_h^αwith α\approx 1. These results are consistent with observations that the AGN fraction in groups and clusters decreases with richness.

astro-ph.CO↗

arXiv2006

Dynamical Friction in Stellar Systems: an introduction

An introductory exposition of Chandrasekhar's gravitational dynamical friction, appropriate for an undergraduate class in mec hanics, is presented. This friction results when a massive particle moving through a ``sea'' of much lighter star particles experiences a retarding force du to an exchange of energy and momentum. General features of dynamical friction are presented, both in an elementary and in a more elaborate way using hyperbolic two-body interactions. The orbital decay of a massive particle in an homogeneous gravitational system is solved analytically, that leads to an underdamped harmonic oscillator type of motion. A numerical integration of the equation of motion in a more realistic c ase is done. These results are compared to those of an N-body computer simulation. Several problems and projects are suggested to students for further st udy.

physics.class-ph↗