Phase Dispersion Minimization Method Research Articles

Attitude motion classification of resident space objects using light curve spectral analysis

The characterization of Earth-orbiting objects in terms of attitude motion, material composition, and shape is crucial for Space Domain Awareness. In this respect, light curves, i.e., graphs showing the brightness variation of space objects over a specific time interval, can be used to infer both their dynamical and physical properties. However, such light curve inversion problem is challenging due to measurement noise, data gaps, and the intrinsic difficulty in separating the multiple effects impacting on the object’s brightness. Existing light curve inversion methods rely on estimation filters exploiting data fusion, Machine Learning approaches, or are based on the analysis of the light-curve frequency spectra. Many of these approaches make assumptions about a-priori knowledge of target object’s characteristics, such as shape, size, surface reflective properties, and/or observation parameters, e.g., target’s orbit and observation geometry. In this framework, this paper presents an innovative architecture for the classification of the attitude motion of space objects using only photometric light curve data, not requiring any a-priori assumption or knowledge. The proposed architecture exploits the Lomb-Scargle Periodogram algorithm to retrieve a frequency spectrum from light curve measurements, and then performs the classification by analyzing the spectrum characteristics testing different candidate rotation periods through the Phase Dispersion Minimization method. The proposed classification algorithm is first tested using a light curve simulator, in which any complex geometric model and different surface properties can be generated. Finally, the method is applied to real light curves retrieved from a publicly available database to assess the classification performance.

Photometry, rotation period determination and dust coma numerical study of comet C/2017 K2 (PanStarrs)

C/2017 K2 (Pan-STARRS) is an Oort cloud comet discovered in May 2017. Ground observations have revealed that this long-period comet was active at a heliocentric distance beyond 20 au. Several studies observed this object when it was far from the Sun and proposed that, at such a distance, its activity is primarily driven by the sublimation of super-volatile ices such as CO and CO2.The aim of this paper is to analyze the comet’s dust behavior when it was much closer to the Sun. A series of images were taken on different observation routines between July and August 2022 with the 0.6 m Helen Sawyer Hogg (HSH) telescope at the Complejo Astronómico El Leoncito (CASLEO), using broadband V and R filters. The objective was to conduct a morphological, photometric, and numerical analysis of this comet.Digital filters were applied to enhance contrast in the cometary images, revealing an active region embedded within an isotropic coma. Analysis of the magnitudes and dust production rate from the A(0°)fρ parameter suggests a steady-state dust behavior, consistent with findings from other authors.Moreover, thanks to the images covering a significant time span, it was possible to determine the comet’s rotation period using a periodogram analysis with the Phase Dispersion Minimization method (PDM) and to calculate the coordinates of the rotation axis, yielding a rotation period of 14.24 h with a pole situated at the ecliptic longitude and latitude of (244°,−20°).Finally, to gain deeper insights into C/2017 K2’s dust behavior, observations were fitted to a newly developed theoretical model for studying dust comas. The analysis suggests that the comet’s dust coma was principally formed by large dust particles emitted at a velocity of 180ms−1.

Variability in Early Post-main-sequence Stars in Globular Cluster NGC 3201

In this paper we study stellar variability in the globular cluster NGC 3201 in the magnitude range V = 16–17, corresponding to the subgiant branch and blue stragglers region of the cluster. Our aim is to expand the sample of new type of variables with low amplitude and a short period found in previous papers. We used observations obtained at the Complejo Astronómico El Leoncito. We applied statistical tests and analyzed periodograms obtained by generalized Lomb–Scargle and phase dispersion minimization methods. We found five stars considered as variables and one as a possible variable. According to their periods (fluctuating between 0.33 and 0.57 days), amplitudes (between 0.03 and 0.87 V magnitudes), the position in the color–magnitude diagram, and the shape of their phased light curves, they do not resemble any known variable star. Because stellar variability could be produced by more than one process, we propose to complement this work with a spectroscopic analysis to confirm our results.

Light curve analysis of main belt asteroids 4747, 5255, 11411, 15433, 17866

Abstract The main belt asteroids 4747, 5255, 11411, 15433, and 17866 were studied at the Baldone Astrophysical Observatory in the time span range 2018–2022. The obtained light curve data together with published Minor Planet Center data are analyzed with Fourier series, Lomb-Scargle periodogram, and phase dispersion minimization methods. A plan of analysis is given. The results computed from different observatories’ data are compared, and mean-weighted periods are obtained.

M dwarf stars in the b294 field from the VISTA Variables in the Vía Láctea (VVV)

ABSTRACT M dwarf stars are the dominant stellar population in the Milky Way, and they are important for a wide variety of astrophysical topics. The Gaia mission has delivered a superb collection of data, nevertheless, ground-based photometric surveys are still needed to study faint objects. Therefore, the present work aims to identify and characterize M dwarf stars in the direction of the Galactic bulge using photometric data and with the help of Virtual Observatory tools. Using parallax measurements and proper motions from Gaia Data Release 3, in addition to different colour-cuts based on VISTA filters, we identify and characterize 7 925 M dwarf stars in the b294 field from the Vista Variables in the Vía Láctea (VVV) survey. We performed a spectral energy distribution fitting to obtain the effective temperature for all objects using photometric information available at Virtual Observatory archives. The objects in our sample have temperatures varying from 2800–3900 K. We also search for periodic signals in VVV light curves with up to 300 epochs, approximately. As a secondary outcome, we obtain periods for 82 M dwarfs by applying two methods: the Lomb–Scargle and Phase Dispersion Minimization methods, independently. These objects, with periods ranging from 0.14–34 d, are good candidates for future ground-based follow up. Our sample has increased significantly the number of known M dwarfs in the direction of the Galactic bulge and within 500 pc, showing the importance of ground-based photometric surveys in the near-infrared.

Eclipse timing variation analysis of OGLE-IV eclipsing binaries towards the Galactic Bulge – II. Short periodic triple stellar systems

ABSTRACT We report an eclipse timing variations (ETV) study to identify close, stellar mass companions to the eclipsing binaries monitored during the photometric survey Optical Gravitational Lensing Experiment-IV. We also present an alternative automatic way to determine the first and last contacts of an eclipse. Applying the phase dispersion minimization method to identify potential triples, we find close third components with outer periods in less than 1500 d in 23 systems. We present outer orbit solution for 21 of 23 systems. For the 10 tightest triples, we find that the ETV can only be modelled with the combination of the light-travel-time effect (LTTE) and third-body perturbations, while in case of another 11 systems, pure LTTE solutions are found to be satisfactory. In the remaining two systems, we identify extra eclipses connected to the outer component, but for the incomplete and noisy ETV curves, we are unable to find realistic three-body solutions. Therefore, in these cases we give only the outer period.

Background Short-period Eclipsing Binaries in the Original Kepler Field

Abstract During the primary Kepler mission, between 2009 and 2013, about 150,000 preselected targets were observed with a 29.42 minute long cadence. However, a survey of background stars that fall within the field of view (FOV) of the downloaded apertures of the primary targets has revealed a number of interesting objects. In this paper, we present the results of this search, focusing on short-period eclipsing binary (SPEB) stars in the background pixels of primary Kepler targets. We used Lomb–Scargle and Phase Dispersion Minimization methods to reveal pixels that show significant periodicities, resulting in the identification of 547 previously unknown faint SPEBs, mostly W UMa–type stars, and almost doubling the number of SPEBs in the original Kepler FOV. We prepared the light curves for scientific analysis and cross-matched the pixel coordinates with Gaia and other catalogs to identify the possible sources. We have found that the mean of the brightness distribution of the new background SPEBs is ∼4–5 mag fainter than other, primary target eclipsing binaries in the Kepler Eclipsing Binary catalog. The period distribution nonetheless follows the same trend, but the spatial distribution appears to be different from that described by Kirk et al. for the catalog eclipsing binaries.

Photometric Variability of the mCP Star CS Vir: Evolution of the Rotation Period

AbstractThe aim of this study is to accurately calculate the rotational period of CS Vir by using STEREO observations and investigate a possible period variation of the star with the help of all accessible data. The STEREO data that cover 5-yr time interval between 2007 and 2011 are analysed by means of the Lomb–Scargle and Phase Dispersion Minimization methods. In order to obtain a reliable rotation period and its error value, computational algorithms such as the Levenberg–Marquardt and Monte Carlo simulation algorithms are applied to the data sets. Thus, the rotation period of CS Vir is improved to be 9.29572(12) d by using the 5-yr of combined data set. Also, the light elements are calculated as HJDmax = 2454715.975(11) + 9d· 29572(12) × E + 9d· 78(1.13) × 10 − 8 × E2 by means of the extremum times derived from the STEREO light curves and archives. Moreover, with this study, a period variation is revealed for the first time, and it is found that the period has lengthened by 0.66(8) s y−1, equivalent to 66 s per century. Additionally, a time-scale for a possible spin-down is calculated around τSD ~ 106 yr. The differential rotation and magnetic braking are thought to be responsible of the mentioned rotational deceleration. It is deduced that the spin-down time-scale of the star is nearly three orders of magnitude shorter than its main-sequence lifetime (τMS ~ 109 yr). It is, in return, suggested that the process of increase in the period might be reversible.

Low-amplitude rotational modulation rather than pulsations in the CoRoT B-type supergiant HD 46769

{We aim to detect and interpret photometric and spectroscopic variability of the bright CoRoT B-type supergiant target HD\,46769 ($V=5.79$). We also attempt to detect a magnetic field in the target.} {We analyse a 23-day oversampled CoRoT light curve after detrending, as well as spectroscopic follow-up data, by using standard Fourier analysis and Phase Dispersion Minimization methods. We determine the fundamental parameters of the star, as well as its abundances from the most prominent spectral lines. We perform a Monte Carlo analysis of spectropolarimetric data to obtain an upper limit of the polar magnetic field, assumping a dipole field.} {In the CoRoT data, we detect a dominant period of 4.84\,d with an amplitude of 87\,ppm, and some of its (sub-)multiples. Given the shape of the phase-folded light curve and the absence of binary motion, we interpret the dominant variability in terms of rotational modulation, with a rotation period of 9.69\,d. Subtraction of the rotational modulation signal does not reveal any sign of pulsations. Our results are consistent with the absence of variability in the Hipparcos light curve. The spectroscopy leads to a projected rotational velocity of 72$\pm 2$\,km\,s$^{-1}$ and does not reveal periodic variability nor the need to invoke macroturbulent line broadening. No signature of a magnetic field is detected in our data. A field stronger than $\sim 500$\,G at the poles can be excluded, unless the possible non-detected field were more complex than dipolar.} {The absence of pulsations and of macroturbulence of this evolved B-type supergiant is placed into context of instability computations and of observed variability of evolved B-type stars.}

A photometric study of chemically peculiar stars with the STEREO satellites – II. Non-magnetic chemically peculiar stars★

We have analysed the photometric data obtained with the STEREO spacecraft for 558 non-magnetic chemically peculiar (CP) stars to search for rotational and pulsational variability. Applying the Lomb–Scargle and the phase dispersion minimization methods, we have detected photometric variability for 44 objects from which 35 were previously unknown. The new objects are all bright stars on the ecliptic plane (magnitude range 4.7 < V < 11.7) and will therefore be of great interest to studies of stellar structure and evolution. In particular, several show multiple signals consistent with hybrid δ Scuti and γ Doradus pulsation, with different periodicities allowing very different regions of the stellar interior to be studied. There are two subgroups of stars in our sample: the cool metallic line Am (CP1) and the hot HgMn (CP3) stars. These objects fall well inside the classical instability strip where δ Scuti, γ Doradus and slowly pulsating B-type stars are located. We also expect to find periods correlated to the orbital period for CP1 objects as they are mostly members of binary systems. For CP3 stars, rotationally induced variability is still a matter of debate. Although surface spots were detected, they are believed to produce only marginal photometric amplitudes. So, periods from several hours to a few days were expected for these two star groups. The STEREO/HI-1 data are well matched to studies of this frequency domain, owing to the cadence of approximately 40 min and multiple epochs over four and a half years. The remaining 514 stars are likely to be constant in the investigated range from 0.1 to 10 d. In some cases, the presence of blending or systematic effects prevented us from detecting any reliable variability and in those cases we classified the star as constant. We discuss our results in comparison to already published ones and find a very good agreement. Finally, we have calibrated the variable stars in terms of the effective temperature and luminosity in order to estimate masses and ages. For this purpose, we used specifically developed calibrations for CP stars and, when available, Hipparcos parallaxes. All but two objects cover the stellar mass range from 1.5 to 5 M⊙ and are located between the zero- and terminal-age main sequence.

Photometric study of the short-period RS Canum Venaticorum binary RT Andromedae

Context. Long-term photometric observations of cool stars can reveal the evolution and activity cycles of the stellar active region. Furthermore, studying the stellar activity provides opportunities for understanding of stellar dynamo and valuable constraints for stellar dynamo theory. Aims. We analyze our observational data and discuss light-curve variability due to starspots on both a short and long time scale, especially the short-term variation. At the same time, we accumulate some results from the literature to discuss active-region evolution and activity cycles. Methods. By analyzing the light curves using the Wilson-Devinney program, the photometric solution of the system is obtained and the starspot parameters are also derived. Using the phase-dispersion minimization method, we infer the activity cycle of RT And. Results. The case of two spots being on the primary is most successful in reproducing the light curve distortion of RT And in 2004. Although the light curves in 1999 and 2005 do not have sufficient phase coverage, we still could use the spot model to explain their light-curve variation successfully based on the photometric solution in 2004. Comparing the light curves of 1999, 2004, and 2005, the light curve distortion changes on both short and long time scales, especially the significant variation around the secondary minimum on a time scale of two months. Analysis of the longitude of spots within the belt around 270 degrees suggests that the activity cycle of RT And may be 6.69 +/- 0.80 years.

Period analysis for simultaneous multichannel photometric observations

The method of three stage weighted period analysis is generalized for simultaneous multichannel ob- servations. The new method is based on the phase disper- sion minimization over all channels simultaneously. The three stages in the full algorithm are phase dispersion minimization method (PDM), linear modeling (LM) and nonlinear modeling (NLM). Simple computational tests of the multichannel period analysis (MPA) are presented. We show that the method has advantages if compared with methods where single channels are analysed sepa- rately. We derive a general formula for spurious periods and demonstrate that the interpretation of peaks in the PDM spectra can be more complicated than in classical power spectra.

Systematic Radio-Observations of UX Arietis: Analysis of Its Variability

UX Arietis is an active binary system with an orbital period of 6.44 days. The presence of long lasting large spots on the surface of the more active star has been deduced from optical observations (Vogt &amp; Hatzes 1991).The observations presented here have been performed from December 1992 until October 1994 using the Effelsberg 100 m telescope. The instrument was available for this program in the gaps between previously scheduled observations. For this reason our observations span a frequency interval between 1.4 GHz (21 cm) and 43 GHz (7 mm), depending on the scheduled receiver at each observing time. These data, which are an extension of those published by Neidhöfer et al. (1993), are shown in Fig. 1, plotted in terms of the known orbital period (6.44 days). The search for different periodicities (by using the Phase Dispersion Minimization method) has shown the existence of two main other periods: at 156 days and at 24 days (Massi et al., in preparation).

On the validity of Davies' test for periodicity

Davies' test (1990, MNRAS, 244) for periodicity, which is based on the phase dispersion minimization method, is shown to be of limited application. In his derivation of the null distribution of the test statistic (i.e. the distribution under the null hypothesis of no periodicity), Davies assumes that the period to be tested is known a priori. Consequently, although the test can be used to test periods, that are identified by conducting a period search of the data. In the latter case, Davies uses adjustment based on Bonferroni's Inequality to compensate for the fact that multiple trial periods have been examined. Until a better solution to this difficult problem has been found, the use of the non-parametric randomization test described by Nemec & Nemec (1985, Astron. J., 90) is recommended

Frequency analysis of photometric observations of HD 101158

Photoelectric observations of HD 101158 in visual light were obtained for six nights. A phase dispersion minimization method and Fourier analysis were used to derive a main frequency of 11.0877±0.0057 c/d or one of its aliases, 11.0648 and 11.1118 c/d. Some indications of multiplicity are presented. Because of the short period variability and the spectral type (F0V), HD 101158 is found to be another Delta Scuti star.