HS2325+8205- an ideal laboratory for accretion disc physics (original) (raw)
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HS 2325+8205—An Ideal Laboratory for Accretion Disk Physics
We identify HS 2325 þ 8205 as an eclipsing, frequently outbursting, dwarf nova with an orbital period of P orb ¼ 279:841731ð5Þ minutes. Spectroscopic observations are used to derive the radial velocity curve of the secondary star from absorption features and also from the Hα emission lines, originating from the accretion disk, yielding K sec ¼ K abs ¼ 237 AE 28 km s À1 and K em ¼ 145 AE 9 km s À1 , respectively. The distance to the system is calculated to be 400ðþ200; À140Þ pc. A photometric monitoring campaign reveals an outburst recurrence time of ∼12-14 days. The combination of magnitude range (17-14 mag), high declination, and eclipsing nature and frequency of outbursts makes HS 2325 þ 8205 the ideal system for "real-time" studies of the accretion disk evolution and behavior in dwarf nova outbursts.
Changes in the structure of the accretion disc of HS1804+67 through the outburst cycle
New Astronomy Reviews, 1999
We report on the analysis of high-speed photometry of the dwarf-nova HS1804+67 through its outburst cycle with eclipse mapping techniques. Eclipse maps show evidences of the formation of a spiral structure in the disc at the early stages of the outburst and reveal how the disc expands during the rise until its fills most of the primary Roche lobe at maximum light. During the decline phase, the disc becomes progressively fainter as the cooling front moves inwards from the outer regions, until only a small bright region around the white dwarf is left at minimum light. The variable part of the uneclipsed light is possibly due to emission in a wind emanating from the inner parts of the disc. The emission from this region is sensitive to the mass accretion rate.
Photometry of the low accretion rate polar HS 1023+3900
Astronomy and Astrophysics, 2001
We present results from a photometric monitoring campaign of the new lowṀ magnetic CV HS 1023+3900. It showed the system at a constant brightness level during the half year of observations, confirming that it is permanently accreting at a low rate. Optical light curves are dominated by emission from two cyclotron spots in accordance with previously published spectroscopy. The timings of the primary maxima were used to derive a revised spin-period of 166.93 min. We estimated approximate locations of the accretion spots on the white dwarf by simple modeling of the R and I-band light curves. Interestingly, the dipole axis is perpendicular to the line connecting both stars and inclined into the orbital plane, an orientation quite different from that found in all other polars so far. We report the detection of a single flare event of ∆B ∼ 1 mag lasting ∼1 min, indicating chromospheric activity of the secondary.
An International Ultraviolet Explorer Archival Study of Dwarf Novae in Outburst
The Astrophysical Journal, 2007
We present a synthetic spectral analysis of nearly the entire far-ultraviolet International Ultraviolet Explorer (IUE ) archive of spectra of dwarf novae in or near outburst. The study includes 46 systems of all dwarf nova subtypes, both above and below the period gap. The spectra were uniformly analyzed using synthetic spectral codes for optically thick accretion disks and stellar photospheres, along with the best available distance measurements or estimates. We present newly estimated accretion rates and discuss the implications of our study for disk accretion physics and CV evolution.
BVRI observations of dwarf novae in outburst
Astronomy and Astrophysics Supplement Series, 1998
In this paper we report photometric observations of AL Com, V544 Her, V660 Her, V516 Cyg and DX And taken during the descending phase after an outburst. For four of these variables we calibrated comparison stars in the field of view. Our observations cover the period in which AL Com showed the larger optical outburst since 1974, and V660 Her showed the larger outburst ever reported in the literature (B 14.3). The optical spectral distribution of DX And, AL Com and V660 Her shows that the model of the steady-state accretion disk does not provide a good representation of the optical continuum during the decline phase of a dwarf nova outburst.
Monthly Notices of the Royal Astronomical Society, 2019
We report the analysis of time-series of infrared JHKs photometry of the dwarf nova V2510 Oph in quiescence with eclipse mapping techniques to investigate structures and the spectrum of its accretion disc. The light curves after removal of the ellipsoidal variations caused by the mass-donor star show a double-wave modulation signalling the presence of two asymmetric light sources in the accretion disc. Eclipse maps reveal two spiral arms on top of the disc emission, one at R1 = 0.28 ± 0.02 RL1 and the other at R2 = 0.42 ± 0.02 RL1 (where RL1 is the distance from disc centre to the inner Lagrangian point), which are seen face-on at binary phases consistent with the maxima of the double-wave modulation. The wide open angle inferred for the spiral arms (θs = 21o ± 4o) suggests the quiescent accretion disc of V2051 Oph has high viscosity. The accretion disc is hot and optically thin in its inner regions (Tgas ∼ 10 − 12 × 103 K and surface densities ∼10−3 − 10−2 g cm−2), and becomes cool...
Monthly Notices of the Royal Astronomical Society, 2000
We present a numerical scheme for the evolution of an accretion disc through a dwarf nova outburst. We introduce a time-varying artificial viscosity into an existing smoothed particle hydrodynamics code optimized for two-and three-dimensional simulations of accretion discs. The technique gives rise to coherent outbursts and can easily be adapted to include a complete treatment of thermodynamics. We apply a two-dimensional isothermal scheme to the system SS Cygni, and present a wide range of observationally testable results.
On the nature of long-period dwarf novae with rare and low-amplitude outbursts
Publications of the Astronomical Society of Japan
There are several peculiar long-period dwarf-nova like objects, which show rare, low-amplitude outbursts with highly ionized emission lines. 1SWASP J162117+441254, BD Pav, and V364 Lib belong to this kind of objects. Some researchers even doubt whether 1SWASP J1621 and V364 Lib have the same nature as normal dwarf novae. We studied the peculiar outbursts in these three objects via our optical photometry and spectroscopy, and performed numerical modeling of their orbital variations to investigate their properties. We found that their outbursts lasted for a long interval (a few tens of days), and that slow rises in brightness were commonly observed during the early stage of their outbursts. Our analyses and numerical modeling suggest that 1SWASP J1621 has a very high inclination, close to 90 deg, plus a faint hot spot. Although BD Pav seems to have a slightly lower inclination (∼75 deg), the other properties are similar to those in 1SWASP J1621. On the other hand, V364 Lib appears to have a massive white dwarf, a hot companion star, and a low inclination (∼35 deg). In addition, these three objects possibly have low transfer rate and/or large disks originating from the long orbital periods. We find that these properties of the three objects can explain their infrequent and low-amplitude outbursts within the context of the disk instability model in normal dwarf novae without strong magnetic field. In addition, we suggest that the highly-ionized emission lines in outburst are observed due to a high inclination and/or a massive white dwarf. More instances of this class of object may be unrecognized, since their unremarkable outbursts can be easily overlooked.
Results of a campaign to observe outbursts of the dwarf nova CSS 121005:212625+201948
arXiv (Cornell University), 2015
A monitoring programme of CSS 121005:212625+201948 covering nearly two observing seasons has shown that it is a typical SU UMa dwarf nova, but it has one of the shortest supercycles of its class, at 66.9(6) d. The superoutbursts are interspersed with 3 to 7 short duration (~2 days) normal outbursts each of which are separated by a mean interval of 11 days, but can be as short as 2 days. The most intensively studied superoutburst was that of 2014 November, which lasted 14 days and had an outburst amplitude of >4.8 magnitudes, reaching magnitude 15.7 at its brightest. Time resolved photometry revealed superhumps with a peak-to-peak amplitude of 0.2 magnitudes, later declining to 0.1 magnitude. The superhump period was P sh = 0.08838(18) d. Time resolved photometry was conducted during several other superoutbursts, which gave broadly similar results.
Fundamental parameters of the close interacting binary HD 170582 and its luminous accretion disc
Monthly Notices of the Royal Astronomical Society, 2015
We present a spectroscopic and photometric study of the Double Period Variable HD 170582. Based on the study of the ASAS V-band light curve we determine an improved orbital period of 16.87177 ± 0.02084 days and a long period of 587 days. We disentangled the light curve into an orbital part, determining ephemerides and revealing orbital ellipsoidal variability with unequal maxima, and a long cycle, showing quasi-sinusoidal changes with amplitude ∆V= 0.1 mag. Assuming synchronous rotation for the cool stellar component and semi-detached configuration we find a cool evolved star of M 2 = 1.9 ± 0.1 M , T 2 = 8000 ± 100 K and R 2 = 15.6 ± 0.2 R , and an early B-type dwarf of M 1 = 9.0 ± 0.2 M . The B-type star is surrounded by a geometrically and optically thick accretion disc of radial extension 20.8 ± 0.3 R contributing about 35% to the system luminosity at the V band. Two extended regions located at opposite sides of the disc rim, and hotter than the disc by 67% and 46%, fit the light curve asymmetries. The system is seen under inclination 67.4 ± 0.4 degree and it is found at a distance of 238 ± 10 pc. Specially interesting is the double line nature of H 5875; two absorption components move in anti-phase during the orbital cycle; they can be associated with the shock regions revealed by the photometry. The radial velocity of one of the H 5875 components closely follows the donor radial velocity, suggesting that the line is formed in a wind emerging near the stream-disc interacting region.