100 research outputs found
Spectroscopic and Photometric Analysis of the Nova-Like Cataclysmic Variable PG 1000+667: A New VY Sculptoris Star
Multiyear photometry and orbit-resolved spectroscopy of the nova-like cataclysmic variable PG 1000+667 show behavior associated with the VY Sculptoris subclass of nova-like cataclysmic variables. Photometric observations over a 35 month interval from Indiana University\u27s robotic telescope Robo-Scope show two drops of 3 mag to a low state. Spectroscopy shows a periodic velocity variation in the Hβ emission line with P = 3.47 hr. This places the star just above the 2-3 hour period gap, which supports the VY Sculptoris classification
Testing the binary hypothesis for the formation and shaping of planetary nebulae
There is no quantitative theory to explain why a high 80% of all planetary
nebulae are non-spherical. The Binary Hypothesis states that a companion to the
progenitor of a central star of planetary nebula is required to shape the
nebula and even for a planetary nebula to be formed at all. A way to test this
hypothesis is to estimate the binary fraction of central stars of planetary
nebulae and to compare it with that of the main sequence population.
Preliminary results from photometric variability and the infrared excess
techniques indicate that the binary fraction of central stars of planetary
nebulae is higher than that of the main sequence, implying that PNe could
preferentially form via a binary channel. This article briefly reviews these
results and current studies aiming to refine the binary fraction.Comment: EUROWD12 Proceeding
Planetary nebulae : getting closer to an unbiased binary fraction
Why 80% of planetary nebulae are not spherical is not yet understood. The
Binary Hypothesis states that a companion to the progenitor of the central star
of a planetary nebula is required to shape the nebula and even for a planetary
nebula to be formed at all. A way to test this hypothesis is to estimate the
binary fraction of central stars of planetary nebula and to compare it with the
main sequence population. Preliminary results from photometric variability and
infrared excess techniques indicate that the binary fraction of central stars
of planetary nebulae is higher than that of the putative main sequence
progenitor population, implying that PNe could be preferentially formed via a
binary channel. This article briefly reviews these results and future studies
aiming to refine the binary fraction.Comment: SF2A 2012 proceeding
Reconnaissance of Suspected Old Novae
Several of the \ blank fields\ in the novae atlas by Duerbeck were imaged at the WIYN 3.5 m telescope during technical engineering and commissioning activities in 1994-1995. Several old novae have been recovered utilizing CCD photometry. Multiobject spectroscopy with the Hydra/MOS instrumentation at WIYN was also used on random stars in the fields to search for a cataclysmic variable. The old novae candidates identified include SV Ari, V465 Cyg, SS LMi, V2104 Oph, GR Ori, V529 Ori, UW Per, and UW Tri
Dynamical Masses for the Large Magellanic Cloud Massive Binary System [L72] LH 54-425
We present results from an optical spectroscopic investigation of the massive
binary system [L72] LH~54-425 in the LH 54 OB association in the Large
Magellanic Cloud. We revise the ephemeris of [L72] LH 54-425 and find an
orbital period of 2.247409 +/- 0.000010 days. We find spectral types of O3 V
for the primary and O5 V for the secondary. We made a combined solution of the
radial velocities and previously published V-band photometry to determine the
inclination for two system configurations, i = 52 degrees for the configuration
of the secondary star being more tidally distorted and i = 55 degrees for the
primary as the more tidally distorted star. We argue that the latter case is
more probable, and this solution yields masses and radii of M_1 = 47 +/- 2
M_Sun and R_1 = 11.4 +/- 0.1 R_Sun for the primary, and M_2 = 28 +/- 1 M_Sun
and R_2 = 8.1 +/- 0.1 R_Sun for the secondary. Our analysis places LH 54-425
amongst the most massive stars known. Based on the position of the two stars
plotted on a theoretical HR diagram, we find the age of the system to be about
1.5 Myr.Comment: 21 pages, 6 figures. Accepted in ApJ. To appear vol. 683, Aug. 10t
Fast optical variability of SS 433
We study the optical variability of the peculiar Galactic source SS 433 using
the observations made with the Russian Turkish 1.5-m telescope (RTT150). A
simple technique which allows to obtain high-quality photometric measurements
with 0.3-1 s time resolution using ordinary CCD is described in detail. Using
the test observations of nonvariable stars, we show that the atmospheric
turbulence introduces no significant distortions into the measured light
curves. Therefore, the data obtained in this way are well suited for studying
the aperiodic variability of various objects.
The large amount of SS 433 optical light curve measurements obtained in this
way allowed us to obtain the power spectra of its flux variability with a
record sensitivity up to frequencies of ~0.5 Hz and to detect its break at
frequency =~2.4e-3 Hz. We suggest that this break in the power spectrum results
from the smoothing of the optical flux variability due to a finite size of the
emitting region. Based on our measurement of the break frequency in the power
spectrum, we estimated the size of the accretion-disk photosphere as 2e12 cm.
We show that the amplitude of the variability in SS 433 decreases sharply
during accretion-disk eclipses, but it does not disappear completely. This
suggests that the size of the variable optical emission source is comparable to
that of the normal star whose size is therefore R_O \approx 2e12 cm \approx 30
R_sun. The decrease in flux variability amplitude during eclipses suggests the
presence of a nonvariable optical emission component with a magnitude
m_R=~13.2.Comment: 12 pages, 11 figures. Accepted for publication in Astronomy Letters.
The original version in Russian is available at
http://hea.iki.rssi.ru/rtt150/ru/ss433_pazh10/pss433_fast.pd
First Results from the CHARA Array. II. A Description of the Instrument
The CHARA Array is a six 1-m telescope optical/IR interferometric array
located on Mount Wilson California, designed and built by the Center for High
Angular Resolution Astronomy of Georgia State University. In this paper we
describe the main elements of the Array hardware and software control systems
as well as the data reduction methods currently being used. Our plans for
upgrades in the near future are also described
The Ultraviolet Spectrum and Physical Properties of the Mass Donor Star in HD 226868 = Cygnus X-1
We present an examination of high resolution, ultraviolet spectroscopy from
Hubble Space Telescope of the photospheric spectrum of the O-supergiant in the
massive X-ray binary HD 226868 = Cyg X-1. We analyzed this and ground-based
optical spectra to determine the effective temperature and gravity of the O9.7
Iab supergiant. Using non-local thermodynamic equilibrium (non-LTE), line
blanketed, plane parallel models from the TLUSTY grid, we obtain T_eff = 28.0
+/- 2.5kK and log g > 3.00 +/- 0.25, both lower than in previous studies. The
optical spectrum is best fit with models that have enriched He and N
abundances. We fit the model spectral energy distribution for this temperature
and gravity to the UV, optical, and IR fluxes to determine the angular size of
and extinction towards the binary. The angular size then yields relations for
the stellar radius and luminosity as a function of distance. By assuming that
the supergiant rotates synchronously with the orbit, we can use the radius -
distance relation to find mass estimates for both the supergiant and black hole
as a function of the distance and the ratio of stellar to Roche radius. Fits of
the orbital light curve yield an additional constraint that limits the
solutions in the mass plane. Our results indicate masses of 23^{+8}_{-6} M_sun
for the supergiant and 11^{+5}_{-3} M_sun for the black hole.Comment: ApJ in pres
The outflows and 3D structure of NGC 6337, a planetary nebula with a close binary nucleus
NGC 6337 is a member of the rare group of planetary nebulae where a close
binary nucleus has been identified. The nebula's morphology and emission line
profiles are both unusual, particularly the latter. We present a thorough
mapping of spatially resolved, long-slit echelle spectra obtained over the
nebula that allows a detailed characterization of its complex kinematics. This
information, together with narrow band imagery is used to produce a three
dimensional model of the nebula using the code SHAPE. The 3-D model yields a
slowly expanding toroid with large density fluctuations in its periphery that
are observed as cometary knots. A system of bipolar expanding caps of low
ionization are located outside the toroid. In addition, an extended high
velocity and tenuous bipolar collimated outflow is found emerging from the core
and sharply bending in opposite directions, a behavior that cannot be accounted
for by pure magnetic launching and collimation unless the source of the outflow
is precessing or rotating, as could be expected from a close binary nucleus.Comment: Accepted for publication in Astrophysical Journa
The post-common-envelope binary central star of the planetary nebula PN G283.7-05.1
We present the discovery and characterisation of the post-common-envelope central star system in the planetary nebula PN G283.7-05.1. Deep images taken as part of the POPIPlaN survey indicate that the nebula may possess a bipolar morphology similar to other post-common-envelope planetary nebulae. Simultaneous light and radial velocity curve modelling reveals that the newly discovered binary system comprises a highly irradiated M-type main-sequence star in a 5.9-hour orbit with a hot pre-white dwarf. The nebular progenitor is found to have a particularly low mass of around 0.4 M, making PN G283.7-05.1 one of only a handful of candidate planetary nebulae that is the product of a common-envelope event while still on the red giant branch. In addition to its low mass, the model temperature, surface gravity, and luminosity are all found to be consistent with the observed stellar and nebular spectra through comparison with model atmospheres and photoionisation modelling. However, the high temperature (Teff ∼ 95 kK) and high luminosity of the central star of the nebula are not consistent with post-RGB evolutionary tracks
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