New photoelectric UBV and BVRI observations, secured during August-November of 2002 at two observatories distant in local time are analyzed together with two earlier photometric data sets and all available radial velocities to derive the most accurate ephemeris of the binary and to set limits on its basic physical elements. These observations were obtained as a support for a high-dispersion spectroscopic study, results of which will be published separately. It was found that radial velocities and photometric observations spanning 53 years can be reconciled with the linear ephemeris T_(prim.min.)_=HJD 2440182.25628(46) + 0.698095113(29)days x E, where the rms errors of the last digits are given in brackets. Masses of the stars are 1.02 and 0.97 solar masses and the binary separation is 4.170 solar radii. There is still a large uncertainty in the stellar radii. We also report the discovery of rapid light variations on a time scale of hours seen in the U band light curve and offer a few thoughts on the future investigation of this binary.
GSC 3208 1986 is an NSVS and TYCHO binary, first observed from 1999 to 2000. It is a W UMa binary with a period of 0.405days. The present observations were taken in 2012 September and are of high precision, averaging a standard deviation of better than 5mmag. The amplitude of the light curve is very nearly 0.5mag yet it undergoes total eclipses. Dominion Astrophysical Observatory spectra give an F3V type (T~6900K) for the system, the earliest of the extreme mass ratio W UMa binaries. The linear period determination of 0.4045672days was calculated with the two sets of epochs available. An early NSVS light curve reveals that the period has been smoothly decreasing over its past 12000 orbits. The binary may be undergoing sinusoidal oscillations due to the presence of a third body, possibly with a period of 23+/-3years. The high inclination of 85{deg} results in a long duration secondary total eclipse, lasting some 49.5minutes. Findings indicate that GSC 3208 1986 is an immaculate extreme mass ratio, q(m_2_/m_1_)=0.24, A-type W UMa binary.
Based on the long-term data in the literature, we present evidence for long-term optical spectral index variability behaviour for BL Lacertae object OJ 287. First we find that the optical spectral index variability period of BL Lacertae object OJ 287 is in agreement with the optical flux variability period of about 11.96yr. It is considered that different processes induce optical variability, and each process should have a definite signature in the spectral index, thus leading to the periodicity of the spectral index. We also find that the time lag between the optical spectral index and the optical flux density is half of the optical flux variability period. This result tends to support the argument that when the brightness of the long-term variations increases, the optical spectra become bluer. These variations can be explained by energy loss of the electrons during the outburst. We show that the spectral index is different during the flares compared with outside the flares; between the first and second flare peaks of the superflares, the spectrum shapes are different. Disparate processes possibly induce the two peaks of OJ 287.
RR Gem is one of the few Blazhko RR Lyrae which has extended enough photometric observations available to study the long-term courses of its pulsation and modulation properties in detail. We investigate the pulsation and modulation properties and the relations between them in RR Gem using the last 70 years' photometric observations in order to gain further insight into the nature of the Blazhko modulation. Photographic, photoelectric and CCD light curves obtained at the Konkoly Observatory and other authors' published maxima observations are studied. Detailed analysis of the light curves, maximum brightness and O-C data are carried out.
We present early-time optical and near-infrared photometry of supernova (SN) 2005cf. The observations, spanning a period from about 12d before to 3 months after maximum, have been obtained through the coordination of observational efforts of various nodes of the European Supernova Collaboration and including data obtained at the 2-m Himalayan Chandra Telescope. From the observed light curve we deduce that SN 2005cf is a fairly typical SN Ia with a post-maximum decline [{delta}m15(B)true=1.12] close to the average value and a normal luminosity of M_B,max_=-19.39+/-0.33. Models of the bolometric light curve suggest a synthesized ^56^Ni mass of about 0.7M_{sun}_. The negligible host galaxy interstellar extinction and its proximity make SN 2005cf a good Type Ia SN template.
CCD UBVRI photometry is presented for type IIb SN 2011dh for about 300 days. The main photometric parameters are derived and the comparison with SNe of similar types is reported. The light curves are similar to those for SN IIb 2008ax, but the initial flash is stronger and very short, and there are humps on the light curves in U and B at the onset of linear decline. Preliminary modeling is carried out, and the results are compared to the quasi-bolometric light curve and to the light curves in UBVRI bands.
1987A-like events form a rare sub-group of hydrogen-rich core-collapse supernovae that are thought to originate from the explosion of blue supergiant stars. Although SN 1987A is the best known supernova, very few objects of this group have been discovered and, hence, studied. In this paper we investigate the properties of SN 2009E, which exploded in a relatively nearby spiral galaxy (NGC 4141) and that is probably the faintest 1987A-like supernova discovered so far. We also attempt to characterize this subgroup of core-collapse supernovae with the help of the literature and present new data for a few additional objects. The lack of early-time observations from professional telescopes is compensated by frequent follow-up observations performed by a number of amateur astronomers. This allows us to reconstruct a well-sampled light curve for SN 2009E. Spectroscopic observations which started about 2 months after the supernova explosion, highlight significant differences between SN 2009E and the prototypical SN 1987A. Modelling the data of SN 2009E allows us to constrain the explosion parameters and the properties of the progenitor star, and compare the inferred estimates with those available for the similar SNe 1987A and 1998A. The light curve of SN 2009E is less luminous than that of SN 1987A and the other members of this class, and the maximum light curve peak is reached at a slightly later epoch than in SN 1987A. Late-time photometric observations suggest that SN 2009E ejected about 0.04M_{sun}_ of ^56^Ni, which is the smallest ^56^Ni mass in our sample of 1987A-like events. Modelling the observations with a radiation hydrodynamics code, we infer for SN 2009E a kinetic plus thermal energy of about 0.6 foe, an initial radius of ~7x10^12^cm and an ejected mass of ~19M_{sun}_. The photospheric spectra show a number of narrow (v~1800km/s) metal lines, with unusually strong BaII lines. The nebular spectrum displays narrow emission lines of H, NaI, [CaII] and [OI], with the [OI] feature being relatively strong compared to the [CaII] doublet. The overall spectroscopic evolution is reminiscent of that of the faint ^56^Ni-poor type II-plateau supernovae. This suggests that SN 2009E belongs to the low-luminosity, low ^56^Ni mass, low-energy tail in the distribution of the 1987A-like objects in the same manner as SN 1997D and similar events represent the faint tail in the distribution of physical properties for normal type II-plateau supernovae.
We present multicolor light curves for the W UMa-type eclipsing binary TU Boo for two epochs separated by 22 years. An analysis of the O-C diagram indicates the earlier observations took place right in the middle of a major period change, thus allowing for a unique study on mass transfer and period changes in this W UMa-type system. We compute model fits to our light curves, along with the only other published set, using the Wilson-Devinney program, and find temporally correlated changes in the size of the secondary component with anomalies in the O-C diagram. We investigate the cause of these changes and find support for the existence of rapid, large-scale mass transfer between the components.
We present UBVRI photometry of 44 Type Ia supernovae (SNe Ia) observed from 1997 to 2001 as part of a continuing monitoring campaign at the Fred Lawrence Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics. The data set comprises 2190 observations and is the largest homogeneously observed and reduced sample of SNe Ia to date, nearly doubling the number of well-observed, nearby SNe Ia with published multicolor CCD light curves.
Wolf-Rayet (WR) stars have strong, hot winds, with mass-loss rates at least a factor of 10 greater than their O-star progenitors, although their terminal wind speeds are similar. In this paper, we use the technique of multiband linear polarimetry to extract information on the global asymmetry of the wind in a sample of 47 bright Galactic WR stars. Our observations also include time-dependent observations of 17 stars in the sample. The path to our goal includes removing the dominating component of wavelength-dependent InterStellar Polarization (ISP), which normally follows the well-known Serkowski law. We include a wavelength-dependent ISP position angle parameter in our ISP law and find that 15 stars show significant results for this parameter. We detect a significant component of wavelength-independent polarization due to electron scattering in the wind for 10 cases, with most WR stars showing none at the ~0.05% level precision of our data. The intrinsically polarized stars can be explained with binary interaction, large-scale wind structure, and clumping. We also found that 5 stars out of 19 observed with the Stromgren b filter (probing the complex {lambda}4600-4700{AA} emission-line region) have significant residuals from the ISP law and propose that this is due to wind asymmetries. We provide a useful catalog of ISP for 47 bright Galactic WR stars and upper limits on the possible level of intrinsic polarization.
