scholarly journals Photoionization modelling of quiescence-phase spectra of novae and a symbiotic star

2020 ◽  
Vol 492 (2) ◽  
pp. 2326-2334 ◽  
Author(s):  
Anindita Mondal ◽  
Ramkrishna Das ◽  
G C Anupama ◽  
Soumen Mondal
Keyword(s):  
Physical Parameters ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Hydrogen Density ◽  
Elemental Abundances ◽  
Optical Region ◽  
Best Fitting ◽  
Best Fit ◽  
Absorption Features ◽  
Phase Spectra

ABSTRACT Using observed and published spectra in the optical region, we have studied a handful of novae and symbiotic stars that show novae-like variability in the quiescence phase. We present results for the novae T Coronae Borealis, GK Persei, RS Ophiuchi, V3890 Sagittarii and V745 Scorpii, and for a symbiotic star BX Monocerotis. Observations were carried out at the 2-m Himalayan Chandra Telescope (HCT). Generally, the spectra show prominent low-ionization emission features of hydrogen, helium, iron and oxygen and TiO absorption features resulting from the cool secondary component; T Coronae Borealis and GK Persei show higher ionization lines. We used the photoionization code cloudy to model these spectra. From the best-fitting models, we have estimated the physical parameters (e.g. temperature, luminosity and hydrogen density), the elemental abundances and other parameters related to the system. By matching the spectra of various giants with the absorption features and using the best fit, we have determined the types of secondaries and also their contribution to the spectra.

Properties of symbiotic stars from studies in the optical region

1982 ◽  
Vol 70 ◽  
pp. 61-70
Author(s):  
Franco Ciatti
Keyword(s):  
Emission Lines ◽  
Symbiotic Stars ◽  
Coronal Emission ◽  
Optical Region ◽  
Type Giant ◽  
Definition Of ◽  
High Degree ◽  
Absorption Features ◽  
Excitation Conditions ◽  
The Continuum

The traditional definition of Symbiotic Stars (SS) is that of objects which display a combination spectrum (e.g. Merrill, 1950) that is emission lines requiring high-excitation conditions, superposed to the continuum and absorption features of a low-temperature star, most commonly an M-type giant. About one hundred of SS are known and listed today. It is anyway apparent that the classification criteria are rather rough, and since the excitation varies from the simple Me to SS with coronal emission, it is not well defined where a clear division should be made. As a result, the available lists include a very heterogeneous set of objects, probably different phases in stellar evolution. Moreover it has been remarked that SS show a rather confusing variety in their spectroscopic and photometric behaviour. Different intensities of both absorption and emission lines are reported from star to star. These facts indicate a high degree of individuality among SS, which is partly cause and/or effect of the adopted definitions.

Stellar Wind Accretion and Raman O VI Spectroscopy of the Symbiotic Star AG Draconis

2018 ◽  
Vol 14 (S343) ◽  
pp. 449-451
Author(s):  
Young-Min Lee ◽  
Jeong-Eun Heo ◽  
Hee-Won Lee ◽  
Ho-Gyu Lee ◽  
Rodolfo Angeloni ◽  
...  
Keyword(s):  
Loss Rate ◽  
Profile Analysis ◽  
Mass Loss Rate ◽  
Flux Ratio ◽  
Orbital Plane ◽  
Mass Transfer Process ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Accretion Flow ◽  
Best Fit

AbstractRaman scattered O VI features at 6825 Å and 7082 Å found in symbiotic stars are important spectroscopic tools to probe the mass transfer process. Adopting a Monte Carlo approach, we perform a profile analysis of Raman O VI features of the yellow SySt AG Draconis and make a comparison with the spectrum obtained with CFHT. It is assumed that the accretion flow is convergent on the entering side with enhanced O VI emission and the flux ratio F(1032)/F(1038)∼1, whereas on the opposite side the flow is divergent with low O VI emission and F(1032/F(1038)∼2. Our best fit to the spectrum is obtained from our model with a mass-loss rate of the giant ∼4 × 10−7 M⊙ yr−1. A slight red wing excess in the spectrum suggests the presence of bipolar neutral components receding in the directions perpendicular to the binary orbital plane with a speed ∼70km s−1

scholarly journals Ultraviolet properties of the symbiotic stars

1982 ◽  
Vol 70 ◽  
pp. 103-113
Author(s):  
Mark H. Slovak ◽  
David L. Lambert
Keyword(s):  
High Resolution ◽  
Broad Band ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Interim Report

Prior to the launch of the IDE satellite in early 1978, the only symbiotic star previously detected in the ultraviolet by earlier UV satellites, such as the 0A0-2, TD-1 and ANS experiments, was AG Pegasi = HD 207757 (Gallager et al. 1979). These broad-band observations indicated that the symbiotics as a class may show a significant ultraviolet flux and thus they became natural candidates for a survey with the IUE satellite. The following is an interim report on a survey of the symbiotics, both at low and, for AG Pegasi and CH Cygni, at high resolution.

Symbiotic Stars in the Local Group of Galaxies: POINT-AGAPE Catalogue Revisited

2017 ◽  
Vol 14 (S339) ◽  
pp. 291-294
Author(s):  
K. Drozd ◽  
J. Mikołajewska ◽  
M. Darnley ◽  
K. Iłkiewicz ◽  
N. Caldwell ◽  
...  
Keyword(s):  
Light Curve ◽  
Local Group ◽  
Light Curves ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Original Point

AbstractThis research was prompted by the discovery of 35 new or candidate symbiotic stars during a targeted search in the Local Group of Galaxies. A catalogue of a further 200 or so such objects has now been compiled. Many of them could be identified with counterparts in the POINT-AGAPE Catalogue. However, information in the Catalogue is limited to position, brightness and possible period, and light-curves are not available. The poster presented an example of a light-curve of a symbiotic star retrieved from original Point-Agape Catalogue data.

Multiwavelength SED as a Tool in Understanding Outbursts of Symbiotic Binaries

2012 ◽  
Vol 21 (1-2) ◽  
Author(s):  
A. Skopal
Keyword(s):  
Energy Distribution ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Physical Parameters ◽  
X Rays ◽  
Symbiotic Stars ◽  
Physical Processes ◽  
Symbiotic Binaries

AbstractSymbiotic binaries consist of a few sources of radiation contributing to spectral energy distribution (SED) from hard X-rays to radio wavelengths. To identify the basic physical processes forming the observed spectrum, we have to disentangle the composite SED into its individual components of radiation, i.e., to determine their physical parameters. Spectral disentangling of different objects at different stages of activity allows us to understand the mechanism of their outbursts. In this contribution I demonstrate the method of multiwave-length modeling SEDs on the example of two classical symbiotic stars, AG Dra and Z And.

The nova type outburst of the symbiotic star AS 296

1990 ◽  
Vol 122 ◽  
pp. 440-441
Author(s):  
Ulisse Munari
Keyword(s):  
Orbital Period ◽  
Active Phase ◽  
Borderline Case ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Late Type ◽  
Type Giant ◽  
One Year

AbstractThe photometric and spectroscopic evolutions, displayed by AS 296 since the June 1988 outburst ([1]), are presented and discussed. The main features of the model outlined by [2], [3] and [4], are confirmed and further developped. An orbital period of about 3 years is inferred from Hα modulation (see [5]).The outburst originated from a TNR event in the accreted envelope of a WD. The IUE and optical spectroscopic evolution agrees with the expected scenario for degenerate conditions in the accreted material, while the high quiescence luminosity of the WD would indicate nondegenerate conditions.The late type giant passed unchanged the outburst. Also the region of Hα formation was not touched by the eruption.After one year the system has not yet reached the quiescence again. The photometric evolution displayed by AS 296 up to June 15, 1989 is presented in Fig.1.In Tab.1, the main features exhibited by symbiotic stars that have experienced a TNR event are summarized. The first 8 objects in the table are usually collectively called "symbiotic novae". They distinguish themselves for the very long outburst duration. At present, AS 296 appears to be a borderline case of such class, and a firm understanding needs to wait for the end of current active phase.

scholarly journals Retrieving the True Masses of Gravitational Wave Sources

Proceedings ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 4 ◽  
Author(s):  
Xian Chen ◽  
Zhefeng Shen
Keyword(s):  
Hydrodynamic Drag ◽  
Chirp Signal ◽  
Binary Black Holes ◽  
Best Fitting ◽  
Real Mass ◽  
The Masses ◽  
The Impact ◽  
Best Fit ◽  
Gas Effect ◽  
Fitting Parameters

Gravitational waves (GWs) encode important information about the mass of the source. For binary black holes (BBHs), the templates that are used to retrieve the masses normally are developed under the assumption of a vacuum environment. However, theories suggest that some BBHs form in gas-rich environments. Here, we study the effect of hydrodynamic drag on the chirp signal of a stellar-mass BBH and the impact on the measurement of the mass. Based on theoretical arguments, we show that the waveform of a BBH in gas resembles that of a more massive BBH residing in vacuum. The effect is important for those GW sources in the band of space-borne detectors but negligible for those in ground-based ones. Furthermore, we carry out a matched-filtering search of the best fitting parameters. We find that the best-fit chirp mass could be significantly greater than the real mass when the gas effect is ignored. Our results have important implications for the future joint observation of BBHs using both ground- and space-based detectors.

scholarly journals Symbiotic star UV emission and theoretical models

1982 ◽  
Vol 70 ◽  
pp. 269-272
Author(s):  
M. Kafatos
Keyword(s):  
Line Emission ◽  
Theoretical Models ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Uv Emission

Observations of symbiotic stars in the far UV have provided important information on the nature of these objects. The canonical spectrum of a symbiotic star, e.g. RW Hya, Z And, AG Peg, is dominated by strong allowed and semiforbidden lines of a variety of at least twice ionized elements. Weaker emission from neutral and singly ionized species is also present. The Mg II doublet is usually very strong and may be associated with the M giant primary. A continuum may or may not be present in the 1200 - 2000 A range but is generally present in the range 2000 - 3200 A range, the latter arising from free-free and bound-free emission in the same nebula that is responsible for the UV line emission (CI Cyg, RW Hya, RX Pup). The suspected hot subdwarf continuum is seen in some cases in the range 1200 - 2000 A (RW Hya, AG Peg, SY Mus).

scholarly journals Separating the intrinsic alignment signal and the lensing signal using self-calibration in photo-z surveys with KiDS450 and KV450 Data

2020 ◽  
Vol 495 (4) ◽  
pp. 3900-3919 ◽  
Author(s):  
Ji Yao ◽  
Eske M Pedersen ◽  
Mustapha Ishak ◽  
Pengjie Zhang ◽  
Anish Agashe ◽  
...  
Keyword(s):  
Full Potential ◽  
Photometric Redshift ◽  
Self Calibration ◽  
Intrinsic Shape ◽  
Best Fitting ◽  
Systematic Biases ◽  
Cosmic Shear ◽  
Validation Tests ◽  
The Impact ◽  
Best Fit

ABSTRACT To reach the full potential for the next generation of weak lensing surveys, it is necessary to mitigate the contamination of intrinsic alignments (IAs) of galaxies in the observed cosmic shear signal. The self-calibration (SC) of IAs provides an independent method to measure the IA signal from the survey data and the photometric redshift information. It operates differently from the marginalization method based on the IA modelling. In this work, we present the first application of SC to the KiDS450 data and the KV450 data, to split directly the intrinsic shape–galaxy density (Ig) correlation signal and the gravitational shear–galaxy density (Gg) correlation signal, using the information from photometric redshift (photo-z). We achieved a clear separation of the two signals and performed several validation tests. Our measured signals are found to be in general agreement with the KiDS450 cosmic shear best-fitting cosmology, for both lensing and IA measurements. For KV450, we use partial (high-z) data, and our lensing measurements are also in good agreement with KV450 cosmic shear best fit, while our IA signal suggests a larger IA amplitude for the high-z sample. We discussed the impact of photo-z quality on IA detection and several other potential systematic biases. Finally, we discuss the potential application of the information extracted for both the lensing signal and the IA signal in future surveys.

scholarly journals Stability analysis of three exoplanet systems

2020 ◽  
Vol 494 (2) ◽  
pp. 2280-2288
Author(s):  
J P Marshall ◽  
J Horner ◽  
R A Wittenmyer ◽  
J T Clark ◽  
M W Mengel
Keyword(s):  
Time Scales ◽  
Planetary Systems ◽  
Orbital Parameters ◽  
Exoplanetary Systems ◽  
Best Fitting ◽  
The Stability ◽  
Short Time ◽  
Exoplanet Systems ◽  
Best Fit

ABSTRACT The orbital solutions of published multiplanet systems are not necessarily dynamically stable on time-scales comparable to the lifetime of the system as a whole. For this reason, dynamical tests of the architectures of proposed exoplanetary systems are a critical tool to probe the stability and feasibility of the candidate planetary systems, with the potential to point the way towards refined orbital parameters of those planets. Such studies can even help in the identification of additional companions in such systems. Here, we examine the dynamical stability of three planetary systems, orbiting HD 67087, HD 110014, and HD 133131A. We use the published radial velocity measurements of the target stars to determine the best-fitting orbital solutions for these planetary systems using the systemic console. We then employ the N-body integrator mercury to test the stability of a range of orbital solutions lying within 3σ of the nominal best fit for a duration of 100 Myr. From the results of the N-body integrations, we infer the best-fitting orbital parameters using the Bayesian package astroemperor. We find that both HD 110014 and HD 133131A have long-term stable architectures that lie within the 1σ uncertainties of the nominal best fit to their previously determined orbital solutions. However, the HD 67087 system exhibits a strong tendency towards instability on short time-scales. We compare these results to the predictions made from consideration of the angular momentum deficit criterion, and find that its predictions are consistent with our findings.

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