BVRI Colors Research Articles

New light curve analysis and period changes of the HW Vir-type binary system V1828 Aql

The new BVRI photometric observations of the HW Vir-type eclipsing binary system V1828 Aql (P = 0.11037399 days) were presented. From these measurements, 16 new eclipse times have been obtained. The light curves in BVRI colors and the radial curves were simultaneously analyzed by using the Wilson–Devinney method for the system parameters. The system consists of a very hot primary component (T1 = 42000 K) and a cold secondary component (T2 = 3077 ± 250 K). The absolute dimensions were found as follows: (M1 = 0.351 ± 4 0.040 M⊙, M2 = 0.095 ± 0.011 M⊙, R1 = 0.176 ± 0.007 R⊙, R2 = 0.140 ± 0.007 R⊙, L1 =86.91 ± 6.76 L⊙ and L2 = 0.002 ± 0.001 L⊙). The orbital period variation of V1828 Aql was made using all available light minimum times. From the (O - C) diagram, the orbital period shows a variation possibly attributable to the light travel time effect by the presence of the third body. The third body orbital period is P3 = 3317.7−17.2+18.9 days, its minimal mass is M3 = 13.24−0.14+0.13 Mj. The mass value calculated for the third body shows, that this object is right at the border between the planets and the brown dwarfs.

Long-term photometric monitoring of the dwarf planet (136472) Makemake

Aims. We studied the rotational properties of the dwarf planet Makemake. Methods. The photometric observations were carried out at different telescopes between 2006 and 2017. Most of the measurements were acquired in BVRI broad-band filters of a standard Johnson-Cousins photometric system. Results. We found that Makemake rotates more slowly than was previously reported. A possible lightcurve asymmetry suggests a double-peaked period of P = 22.8266 ± 0.0001 h. A small peak-to-peak lightcurve amplitude in R-filter A = 0.032 ± 0.005 mag implies an almost spherical shape or near pole-on orientation. We also measured BVRI colours and the R-filter phase-angle slope and revised the absolute magnitudes. The absolute magnitude of Makemake has remained unchanged since its discovery in 2005. No direct evidence of a newly discovered satellite was found in our photometric data; however, we discuss the possible existence of another larger satellite.

Astrometric and photometric baseline observations of the asteroid 2014 JO25

Ground-based baseline observations of the potentially hazardous asteroid 2014 JO25 were made. The data were processed and the accuracy of the orbital elements of the asteroid was estimated on the basis of the obtained observations and the data from the Minor Planet Center. Also, the estimation of BVRI color indices of the asteroid was made.

Light curve analysis of a new W UMa system GSC 3581-1856

New BVRI photometric observations covering seven minima times for the eclipsing binary GSC 3581-1856 were presented. The light curves in BVRI colours were analysed by using PHOEBE code for the system parameters. New minima times were used in revising the light elements. The system is found a W-type contact binary with mass ratio of q = 1.3362 ± 0.0042 and a fill out parameter of f = 16.89 ± 3.17% . The smaller and less massive component was found hotter component (T1 ≃ 5590 K). Lower temperature (T2 = 5295 K) of the mass accreting more massive component is probably due to a disk or envelope around this star. The original temperature of the more massive secondary component would be at least T2 ≃ 5590 K. The preliminary absolute dimensions (M1 = 0.78 ± 0.01 M⊙, M2 = 1.05 ± 0.01 M⊙, R1 = 0.92 ± 0.10 R⊙, R2 = 1.05 ± 0.20 R⊙, L1 =0.86 ± 0.20 L⊙ and L2 = 1.00 ± 0.20 L⊙) indicate a relatively young marginal contact binary for GSC 3581-1856 system. The present luminosity of the less massive but hotter component would be not much different from its main sequence luminosity, and thus its original mass was estimated to be slightly more than one solar mass. This means it could be transferred and/or lost about 30% of its original mass which place the system in relatively young system in contact phase.

An analysis of the BVRI colors of 22 active comets

Our aim was to analyze the variation of Johnson-Kron-Cousins BVRI color indexes of a sample with 22 active comets of various dynamic groups with the time, geometrical, observational and dynamical parameters. We performed photometric observations of 16 comets between 2010 and 2014, using robotic telescopes in three continents. In addition to the sample, we used data of six comets available in the literature. A statistical comparison between the distributions of color indexes was performed using the Kruskal-Wallis H-test. The color indexes of active comets can vary a few tenths up to a magnitude on time scales that range from hours to weeks. Using the B–V colors of the observed comets, we generated a relationship that correlates the cometary visual and CCD magnitudes. We did not identify any relationship between B–V and V–R colors with heliocentric distance and phase angle. The color B–V is correlated with the photometric aperture that can be described by a logarithmic function. We did not identify any differences in the distribution of B–V color among the comets analyzed at a confidence level equal to or greater than 95%. The mean color of active comets are B–R=1.20±0.24, B–V=0.76±0.16 and V–R=0.42±0.16. Active comets with V–R colors outside the three standard deviation interval can be considered objects with unusual physical characteristics.

First photometric study of the W UMa system GSC 1042-2191

We present new photometric observations covering eight minima times for the eclipsing binary GSC 1042-2191. The light curves in BVRI colors were analyzed by using WD-code for the system parameters. Eight minima times were obtained from the new observations. The system is found a low mass ratio (q = 0.148), A-type over-contact binary with a fill out parameter of f = 65.01 ± 12.18%. The preliminary absolute dimensions (M1= 1.26 ± 0.06 M⊙, M2 = 0.18 ± 0.06 M⊙, R1 = 1.54 ± 0.20 R⊙, R2 = 0.69 ± 0.01 R⊙, L1 =3.30 ± 0.30 L⊙ and L2 = 0.59 ± 0.20 L⊙) indicate the very much oversized and over-luminous secondary component, by assuming the present luminosity of the secondary is its main sequence luminosity, we predict the original mass is about 0.8 M⊙, this means the present secondary could be transferred and/or lost 77% of its original mass and only its core is left.

PHOTOMETRIC PROPERTIES FOR SELECTED ALGOL-TYPE BINARIES. VII. V404 AND WITH MAGNETIC ACTIVITY

We present new CCD light curves of the short-period Algol-type eclipsing binary V404 And obtained in 2009-2011. The time-resolving multiple BVRI color light curves of the year 2011 with full phase coverage were analyzed simultaneously using the latest Wilson-Devinney program. We concluded that the configuration of two starspots on the primary is the most reliable explanation for the light curve distortions observed in 2011. Based on the new photometric solution, we further applied the spot model to explain the other light curves, including the previously published R-band light curves. We revealed that the starspots changed on a long timescale in terms of the spot parameters and the differences between Max. I and Max. II. Moreover, the O - C diagram spanning about 15 yr shows an upward parabola, which indicates a secular increase in the orbital period of V404 And. The orbital period increases at a rate of dP/dt = 5.3(0.3) x 10(-7) days yr(-1), which might be interpreted by the angular momentum exchange via magnetic activity.

A method for the simultaneous estimation of the fundamental atmospheric parameters using the photometric indices in the BVRI and JHK color systems

This is the second paper in a series reporting a new method developed to estimate the fundamental atmospheric parameters of effective temperature, surface gravity, and metallicity simultaneously. In the first paper three parameters were estimated using only photometric indices in the uvby color system. Whereas, in this paper, we use BVRI and JHK color systems. Using the model atmosphere grids, all three parameter values were estimated with respect to both [(B–V):(V–R)] and [(B–V):(R–I)], as well as [(V–K):(H–K)] and [(J–K):(H–K)] pair indices. It was confirmed that (B–V) and (V–K) indices are good temperature indicators, but all color indices for the BVRI and JHK systems are very poor indicators of metallicity and surface gravity. This new method was applied to a number of field dwarfs and giants, and the results were compared with those from the uvby color system. We found that the JHK color system can compete with the uvby system only in the estimation of temperature.

BVRISURFACE PHOTOMETRY OF ISOLATED GALAXY TRIPLETS

Optical broadband BVRI observations of 54 galaxies selected from the Catalog of Isolated Triplets of Galaxies in the Northern Hemisphere have been carried out at San Pedro Martir National Observatory to evaluate their photometric and morphological properties. We complement our analysis with Two-Micron All Sky Survey (2MASS) and Sloan Digital Sky Survey (SDSS) images and look for signatures likely related to interactions/mergers. We report apparent/absolute BVRI magnitudes and colors for the 54 galaxies. The membership of these galaxies is re-evaluated by imposing a reasonable condition of concordant redshifts upon the original selection criteria, rendering a final sample of 34 galaxies in 13 triplets, 12 galaxies in close pairs, and 8 galaxy outliers. The triplets are spiral-dominated systems in different dynamical stages from loosely interacting to almost merged objects. The incidence fraction of features likely associated with interactions is {approx}56%, similar to those found in northern and southern compact groups. The average fraction of bars is 35% with a mean value of maximum bar ellipticity {epsilon}{sub max} {approx} 0.4. Bars are hosted in the late-type triplet spirals, almost twice more than in early-type spirals. The global fraction of rings is 20%, all in the late-type components. The overdensity of triplets withmore » respect to the background and their current dynamical status, as devised from our estimate of their dynamical parameters, namely the harmonic radius R{sub H} , velocity dispersion {sigma}, dimensionless crossing time H{sub 0{tau}c}, and virial mass M{sub V} , appear to be sufficient to favor galaxy transformations similar to those seen in dense groups and clusters. By contrast, the lower fraction of bonafide ellipticals and the relatively higher fraction of late-type spirals make these triplets essentially different from the Hickson Compact Groups and more representative of the field. A modest 1.6 enhancement factor in the optical luminosity of the late-type triplet components relative to an isolated galaxy control sample is also interpreted as consistent with interactions in physically bounded aggregates. Our results lead us to suggest that non-negligible populations of physical triplets might be found in complete and well-observed samples. We provide individual mosaics for the 54 galaxies containing (1) logarithmic-scaled R-band images, (2) R-band sharp/filtered images, (3) (B - I) color index maps, (4) RGB images from the SDSS database, (5) co-added J + H + K images generated from the 2MASS archives that were also sharp/filtered, and (6) {epsilon}, position angle radial profiles from a surface photometry analysis of (a) the R band and (b) the co-added near-infrared images, all used for the present analysis.« less

Puzzling asteroid 21 Lutetia: our knowledge prior to the Rosetta fly-by

A wide observational campaign was carried out in 2004-2009 aimed to complete the ground-based investigation of Lutetia prior to the Rosetta fly-by in July 2010. We have obtained BVRI photometric and V-band polarimetric measurements over a wide range of phase angles, and visible and infrared spectra in the 0.4-2.4 micron range. We analyzed them together with previously published data to retrieve information on Lutetia's surface properties. Values of lightcurve amplitudes, absolute magnitude, opposition effect, phase coefficient and BVRI colors of Lutetia surface seen at near pole-on aspect have been determined. We defined more precisely parameters of polarization phase curve and showed their distinct deviation from any other moderate-albedo asteroid. An indication of possible variations both in polarization and spectral data across the asteroid surface was found. To explain features found by different techniques we propose that (i) Lutetia has a non-convex shape, probably due to the presence of a large crater, and heterogeneous surface properties probably related to surface morphology; (ii) at least part of the surface is covered by a fine-grained regolith with particle size less than 20 microns; (iii) the closest meteorite analogues of Lutetia's surface composition are particular types of carbonaceous chondrites or Lutetia has specific surface composition not representative among studied meteorites.

Polarimetry and BVRI photometry of the potentially hazardous near-Earth Asteroid (23187) 2000 PN 9

The results of V-band polarimetric observations of the potentially hazardous near-Earth Asteroid (23187) 2000 PN 9 at large phase angles are presented as well as its photometric observations in BVRI bands. Observations were made in March–April 2006 during its close approach to the Earth using the 1.82-m Asiago telescope (Italy) and the 0.7-m telescope at the Chuguevskaya Observational Station (Ukraine). We obtained polarimetric measurements at the phase angle of 115°, the largest phase angle ever observed in asteroid polarimetry. Our data show that the maximum value of the polarization phase curve reached 7.7% and occurred in the phase angle range of 90–115°. The measured values of linear polarization degree, BVRI colors and magnitude-phase dependence correspond to the S-type composition of this asteroid. Based on our observations the following characteristics of the Asteroid (23187) 2000 PN 9 were obtained: a rotation period of 2.5325 ± 0.0004 h , a lightcurve amplitude of 0.13 mag, an albedo of 0.24 ± 0.06 and a diameter of 1.6 ± 0.3 km .

An Extremely Bright Echo Associated with SN 2002hh

We present new, very late time optical photometry and spectroscopy of the interesting Type II-P supernova SN 2002hh, in NGC 6946. Gemini/GMOS-N has been used to acquire visible spectra at six epochs between 2004 August and 2006 July, following the evolution of the SN from age 661 to 1358 days. Few optical spectra of Type II supernovae with ages greater than 1 yr exist. In addition, g', r', and i' images were acquired at all six epochs. The spectral and photometric evolution of SN 2002hh has been very unusual. Measures of the brightness of this SN, both in the R and I bands, as well as in the Hα emission flux, show no significant fading over an interval of nearly 2 years. The most straightforward explanation for this behavior is that the light being measured comes not only from the SN itself but also from an echo off nearby dust. Echoes have been detected previously around several SNe, but these echoes, at their brightest, were ~8 mag below the maximum brightness of the SN. At V ~ 21 mag, the putative echo dominates the light of SN 2002hh and is only ~4 mag below the outburst's peak brightness. There is an estimated 6 mag of total extinction in V toward SN 2002hh. The proposed explanation of a differential echo/SN absorption is inconsistent with the observed BVRI colors.

The Effects of Interactions on the Structure and Morphology of Elliptical/Lenticular Galaxies in Pairs

We present a structural and photometric analysis of 42 elliptical/lenticular galaxies in (E/S0 + S) pairs observed in the BV RI color bands. The aim of the analysis is to empirically determine the effects of interactions on their morphology, structure and stellar populations as seen from the light concentration (C), asymmetry (A), and clumpiness (S) parameters. We further compare these values to a control sample of 67 mostly isolated non-interacting E/S0 galaxies. We find that the paired E/S0 galaxies occupy a more scattered loci in CAS space than non-interacting E/S0’s, and that the effects of interactions on E/S0’s are minor, in contrast to disk galaxies involved in interactions. This suggests that observational methods for recognizing interactions at high redshift, such the CAS methodology of Conselice (2003), would hardly detect E/S0’s involved in interactions (related to early phases of the so called ‘dry-mergers’), and that the majority of interacting galaxies identified at high redshift must be gas dominated systems. We however find statistical differences in the asymmetry index when comparing isolated and interacting E/S0s. In the mean, paired E/S0 galaxies have A values 2.96 ± 0.72 times larger than the ones of noninteracting E/S0’s. For the subset of presumably strongly interacting E/S0’s, A and S can be several times larger than the typical values of the isolated E/S0’s. We show that the asymmetries are consistent with several internal and external morphological distortions. We conclude that the subset of interacting E/S0s should be dense, gas poor galaxies in systems spaning a wide range of interaction stages, with typical merging timescales > ∼0.1 0.5 Gyr. We use the observed phenomenology of this subsample to predict the approximate loci of ‘dry pre-mergers’ in the CAS parameter space. Subject headings: Galaxies: elliptical – Galaxies: lenticular – Galaxies: structure – Galaxies: photometry – Galaxies: interactions – Galaxies: morphology

Surface characterization of 28978 Ixion (2001 KX$\mathsf{_{76}}$)

The Plutino 28978 Ixion, one of the largest objects in the Kuiper Belt, is measured by R filter photometry and linear polarimetry over the phase angle range as well as by BVRI colours and visible spectroscopy. Ixion is a medium red object with spectral slope of 17.7%/100 nm (400-900 nm). While its opposition phase curve surge (0.2 mag/deg) is within the typical range found for other solar system objects, it displays unusually high negative polarization (min. -1.3%). Comparison with model spectra and numerical modeling of the opposition brightening and polarization effects suggest an areal mixture of absorbing (dark) and icy (bright) compounds on its surface: the mixing ratio is about 6:1 for dark and bright material of 0.21 and 0.79 single-scattering albedo and of 250 and 33 dimensionless mean free path (length multiplied by wave number), respectively.

Photometric survey of the irregular satellites

We present BVRI colors of 13 jovian and 8 saturnian irregular satellites obtained with the 2.56 m Nordic Optical Telescope on La Palma, the 6.5 m Magellan Baade Telescope on La Campanas, and the 6.5 m MMT on Mt. Hopkins. The observations were performed from December 2001 to March 2002. The colors of the irregular satellites vary from grey to light red. We have arbitrarily divided the known irregular satellites into two classes based on their colors. One, the grey color class, has similar colors to the C-type asteroids, and the other, the light red color class, has colors similar to P/D-type asteroids. We also find at least one object, the jovian irregular J XXIII Kalyke, that has colors similar to the red colored Centaurs/TNOs, although its classification is insecure. We find that there is a correlation between the physical properties and dynamical properties of the irregular satellites. Most of the dynamical clusters have homogeneous colors, which points to single homogeneous progenitors being cratered or fragmented as the source of each individual cluster. The heterogeneously colored clusters are most easily explained by assuming that there are several dynamical clusters in the area, rather than just one, or that the parent body was a differentiated, heterogeneous body. By analyzing simple cratering/fragmentation scenarios, we show that the heterogeneous colored S IX Phoebe cluster, is most likely two different clusters, a grey colored cluster centered on S IX Phoebe and a light red colored cluster centered on S/2000 S 1. To which of these two clusters the remaining saturnian irregulars with inclinations close to 174° belong is not clear from our analysis, but determination of their colors should help constrain this. We also show through analysis of possible fragmentation and dispersion of the six known uranian irregulars that they most likely make up two clusters, one centered on U XVI Caliban and another centered on U XVII Sycorax. We further show that, although the two objects have similar colors, a catastrophic fragmentation event creating one cluster containing both U XVI Caliban and U XVII Sycorax would have involved a progenitor with a diameter of ∼395 km. While such an event is not impossible it seems rather improbable, and we further show that such an event would leave 5–6 fragments with sizes comparable to or larger than U XVI Caliban. The stable region around Uranus has been extensively searched to limiting magnitudes far beyond that of U XVI Caliban. The fact that only U XVI Caliban, the larger U XVII Sycorax and four much smaller objects have been found leaves us with a distribution not compatible with a catastrophic event with such a large progenitor. The most likely solution is therefore two separate events creating two uranian dynamical clusters.

143P/Kowal-Mrkos and the Shapes of Cometary Nuclei

We add 143P/Kowal-Mrkos to the small but growing sample of well-observed cometary nuclei. Photometric observations from 3.4 to 4.0 AU heliocentric distance reveal a pointlike object with no detectable outgassing. Periodic modulation of the scattered light (ΔmR = 0.45 ± 0.05) is attributed to rotation of the bare nucleus with a double-peaked period 17.21 ± 0.10 hr and a projected ratio of the shortest to longest axis of about 0.67/1. We also measured the phase coefficient (0.043 ± 0.014 mag deg-1), the BVRI colors (V-R = 0.58 ± 0.02), and the absolute red magnitude [mR(1, 1, 0) = 13.49 ± 0.20]. The effective circular radius is 5.7 ± 0.6 km (geometric albedo 0.04 assumed). We study the properties of 11 well-observed Jupiter-family comet (JFC) nuclei. On average, the nuclei are systematically more elongated (average photometric range = 0.54 ± 0.07) than main-belt asteroids of comparable size ( = 0.32 ± 0.05) and more elongated than fragments produced in laboratory impact experiments. We attribute the elongation of the nuclei to an evolutionary effect, most likely driven by sublimation-induced mass loss. However, we find no evidence for any relation between the nucleus shape and the sublimation timescale. This may be because the timescale for evolution of the nucleus shape is very short compared with the dynamical timescale for the JFCs, meaning that most nuclei in our sample are already highly physically evolved.

Observations of the Centaur 1999 UG5: Evidence of a Unique Outer Solar System Surface

ABSTRACTThe outer solar system body 1999 UG5 is a Centaur of medium brightness and slightly redder color when compared to other Centaurs. Similar to at least 1/5 of the known Centaurs, it is a Saturn‐crosser with a mean orbital distance between Saturn and Uranus. We present optical photometry data and near‐IR spectra obtained during 2000 September, November, and December. We find a rotation period of 13.41 ± 0.04 hr with an amplitude of 0.102 ± 0.005 mag and a phase curve with a Lumme‐Bowell G value of -0.13 ± 0.02. BVRI colors are reported, and they confirm the red spectral gradient observed previously. Our spectra reveal that this redward slope extends into near‐IR wavelengths and indicates possible localized differences in the surface composition.

Line-Blanketing in Theoretical Model Atmospheres for F, G, and K-Type Stars

We have computed improved flux distributions from Gustafsson et al.'s extensive grids of theoretical model atmospheres for late-type (F-K) giant and dwarf stars. In order to enhance the realism of the computed fluxes throughout the optical and the ultraviolet wavelength ranges, the massive list of atomic opacity sources used for the hotter Kurucz models was also employed in calculating the cooler spectra. For both the giant and the dwarf models, the resulting synthetic UBVRI photometry provides excellent matches to the spectroscopic calibrations of the observed metallicity and temperature scales based on the ultraviolet excesses, δ (U-B), and the BVRI colors, respectively. We conclude that atomic line-blanketing due to known, rather than “missing”, opacity sources accounts for the largest fraction of the systematic UV discrepancy existing between observations and earlier model calculations.

Photometry of dwarf K and M stars

view Abstract Citations (24) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Photometry of dwarf K and M stars. Upgren, A. R. ; Lu, P. K. Abstract Broadband photometry in BVRI colors is presented for 120 nearby dwarf K and M stars, most of which have no previous photometry. This is the first contribution in a program to obtain magnitudes and colors of all stars in the lists of dwarf stars by Vyssotsky as well as the nearer stars without photometry in the catalog of nearby stars. Completion of the program will help to evaluate more precisely the selection effects in the Van Vleck program of parallaxes and proper motions. Publication: The Astronomical Journal Pub Date: October 1986 DOI: 10.1086/114225 Bibcode: 1986AJ.....92..903U Keywords: Dwarf Stars; K Stars; M Stars; Stellar Spectrophotometry; Star Distribution; Stellar Color; Stellar Magnitude; Stellar Motions; Astronomy full text sources ADS | data products SIMBAD (115) GCPD (1)

Photometry of possible members of the Hyades cluster. VI

view Abstract Citations (27) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Photometry of possible members of the Hyades cluster. VI. Upgren, A. R. ; Weis, E. W. ; Hanson, R. B. Abstract Photoelectric observations in BVRI colors have been obtained for about 200 stars suspected of being members of the Hyades cluster, mostly on the basis of their proper motions. More than half of this total have been observed photometrically for the first time; the rest are mostly stars covered in the early papers of this series for which the V - R colors had not been determined and for which the accuracy of the photometry could be improved by reobservation. Based on the photometry, about half of these stars appear to be probable cluster members. Most of the stars included here are faint and have appeared in proper-motion lists for which identification charts have not been available. Their identifications were confirmed from their motions measured on plates taken in the course of the Lick Proper Motion Survey. This list raises to about 810 the total number of stars in the Hyades region with broadband photometry. Of these, 365 appear to be probable or possible members of the cluster. Publication: The Astronomical Journal Pub Date: October 1985 DOI: 10.1086/113910 Bibcode: 1985AJ.....90.2039U Keywords: Astronomical Photometry; Star Clusters; Stellar Motions; Star Distribution; Stellar Magnitude; Astronomy full text sources ADS | data products SIMBAD (171) GCPD (1) Related Materials (5) Part 1: 1977AJ.....82..978U Part 2: 1979PASP...91..766W Part 3: 1982PASP...94..475W Part 4: 1983PASP...95...29W Part 6: 1988AJ.....96..148W