Physical Sciences and Mathematics Commons^™

Orbital, Superhump And Superorbital Periods In The Cataclysmic Variables Aq Mensae And Im Eridani, E. Armstrong, J. Patterson, E. Michelsen, John Thorstensen

Dartmouth Scholarship

We report photometric detections of orbital and superorbital signals, and negative orbital sidebands, in the light curves of the nova-like cataclysmic variables AQ Mensae and IM Eridani. The frequencies of the orbital, superorbital, and sideband signals are 7.0686 (3), 0.263 (3), and 7.332 (3) cycles per day (c/d) in AQ Mensae, and 6.870 (1), 0.354 (7), and 7.226 (1) c/d in IM Eridani. We also find a spectroscopic orbital frequency in IM Eridani of 6.86649 (2) c/d. These observations can be reproduced by invoking an accretion disc that is tilted with respect to the orbital plane. This model works well …

The Cataclysmic Variable Sdss J1507+52: An Eclipsing Period Bouncer In The Galactic Halo, Helena Uthas, Christian Knigge, Knox S. Long, Joseph Patterson, John Thorstensen

Dartmouth Scholarship

SDSS J1507+52 is an eclipsing cataclysmic variable (CV) consisting of a cool, non-radially pulsating white dwarf and an unusually small substellar secondary. The system has a high space velocity and a very short orbital period of about 67 min, well below the usual minimum period for CVs. To explain the existence of this peculiar system, two theories have been proposed. One suggests that SDSS J1507+52 was formed from a detached white dwarf-brown dwarf binary. The other theory proposes that the system is a member of the Galactic halo population.

Here, we present the ultraviolet (UV) spectroscopy of SDSS J1507+52 obtained …

Deriving An X-Ray Luminosity Function Of Dwarf Novae Based On Parallax Measurements, K. Byckling, K. Mukai, J. R. Thorstensen, J. P. Osborne

Dartmouth Scholarship

We have derived an X-ray luminosity function using parallax-based distance measurements of a set of 12 dwarf novae, consisting of Suzaku, XMM-Newton and ASCA observations. The shape of the X-ray luminosity function obtained is the most accurate to date, and the luminosities of our sample are concentrated between ~10^{30}-10^{31} erg s^{-1}, lower than previous measurements of X-ray luminosity functions of dwarf novae. Based on the integrated X-ray luminosity function, the sample becomes more incomplete below ~3 x 10^{30} erg s^{-1} than it is above this luminosity limit, and the sample is dominated by X-ray bright dwarf novae. The total integrated …

Sdss Unveils A Population Of Intrinsically Faint Cataclysmic Variables At The Minimum Orbital Period, B. T. Gänsicke, M. Dillon, J. Southworth, J. R. Thorstensen

Dartmouth Scholarship

We discuss the properties of 137 cataclysmic variables (CVs) which are included in the Sloan Digital Sky Survey (SDSS) spectroscopic data base, and for which accurate orbital periods have been measured. 92 of these systems are new discoveries from SDSS and were followed-up in more detail over the past few years. 45 systems were previously identified as CVs because of the detection of optical outbursts and/or X-ray emission, and subsequently re-identified from the SDSS spectroscopy. The period distribution of the SDSS CVs differs dramatically from that of all the previously known CVs, in particular it contains a significant accumulation of …

Hs 2331+3905: The Cataclysmic Variable That Has It All, S. Araujo-Betancor, B. T. Gänsicke, H.-J. Hagen, T. R. Marsh, E T. Harlaftis, J Thorstensen

Dartmouth Scholarship

We report detailed follow-up observations of the cataclysmic variable HS 2331+3905, identified as an emission- line object in the Hamburg Quasar Survey. An orbital period of 81.08 min is unambiguously determined from the detection of eclipses in the light curves of HS 2331+3905. A second photometric period is consistently detected at P ≃ 83.38 min, ∼2.8% longer than Porb, which we tentatively relate to the presence of permanent superhumps. High time resolution photometry exhibits short-timescale variability on time scales of ≃5−6 min which we interpret as non-radial white dwarf pulsations, as well as a coherent signal at 1.12 min, which …

Parallaxes And Distance Estimates For 14 Cataclysmic Variable Stars, John R. Thorstensen

Dartmouth Scholarship

I used the 2.4 m Hiltner Telescope at MDM Observatory in an attempt to measure trigonometric parallaxes for 14 cataclysmic variable stars. Techniques are described in detail. In the best cases the parallax uncertainties are below 1 mas, and significant parallaxes are found for most of the program stars. A Bayesian method that combines the parallaxes together with proper motions and absolute magnitude constraints is developed and used to derive distance estimates and confidence intervals. The most precise distance derive here is for WZ Sge, for which I find 43: 3.1:6 1:5 pc. Six Luyten Half-Second stars with previous precise …

The Cataclysmic Variable Cw 1045+525: A Secondary-Dominated Dwarf Nova?, C. Tappert, J. R. Thorstensen, W. H. Fenton, N. Bennert

Dartmouth Scholarship

We present spectroscopic and photometric observations of the cataclysmic variable CW 1045+525. Both the optical spectrum and the photometric lightcurve show a strong contribution of a K5V–M0V secondary. We derive an orbital period Porb = 0.271278(1) d by measuring the radial velocities of the absorption lines of the secondary. The period and spectral type of the secondary suggest a distance of 350–700 pc. There is evidence for additional sources of line- and continuum emission, but no direct evidence of an accretion disc. We discuss several scenarios for the nature of CW 1045+525 on the basis of our results, finding a …

Spectroscopy And Orbital Periods Of Four Cataclysmic Variable Stars, John R. Thorstensen, Cynthia J. Taylor

Dartmouth Scholarship

We present spectroscopy and orbital periods P_orb of four relatively little-studied cataclysmic variable stars. The stars and their periods are: AF Cam, P_orb = 0.324(1) d (the daily cycle count is slightly ambiguous); V2069 Cyg (= RX J2123.7+4217), 0.311683(2) d; PG 0935+075, 0.1868(3) d; and KUV 03580+0614, 0.1495(6) d. V2069 Cyg and KUV 03580+0614 both show He iiλ4686 emission comparable in strength to Hβ. V2069 Cyg appears to be a luminous nova-like variable, and the strong He ii suggests it may be an intermediate polar. The period of KUV 03580+0614 is similar to members …

The Long-Period Orbit Of The Dwarf Nova V630 Cassiopeiae, J. A. Orosz, J. R. Thorstensen, R. K. Honeycutt

Dartmouth Scholarship

We present extensive spectroscopy and photometry of the dwarf nova V630 Cassiopeiae. A late-type (K4-5) absorption spectrum is easily detectable, from which we derive the orbital parameters. We find a spectroscopic period of P=2.56387 +/- (4 times 10^{-5}) days and a semiamplitude of K_2=132.9 +/- 4.0 km/s. The resulting mass function, which is a firm lower limit on the mass of the white dwarf, is then f(M)=0.624 +/- 0.056 solar masses. The secondary star is a ``stripped giant'', and using relations between the core mass and the luminosity and the core mass and the radius we derive a lower limit …

Spectroscopy And Orbital Periods Of The Old Novae V533 Herculis, V446 Herculis And X Serpentis, J. R. Thorstensen, C. J. Taylor

Dartmouth Scholarship

We report spectroscopic orbital periods of 0.147 d (= 3.53 h) for V533 Her, 0.207 d (= 4.97 h) for V446 Her and 1.478 d for X Ser. V533 Her (Nova Herculis 1963) shows absorption features in its He i and Balmer lines which appear only in a limited range of orbital phase, suggesting that it is a low-inclination SW Sextantis star. V446 Her is unusual in that it has started normal dwarf nova eruptions after a nova outburst, but we find nothing else unusual about it — in particular, a distance estimate based on its dwarf nova outbursts agrees …

A Photometric And Spectroscopic Study Of The Cataclysmic Variable Sx Leonis Minoris In Quiescence And Superoutburst, R. Mark Wagner, John R. Thorstensen, R. K. Honeycutt, S. B. Howell

Dartmouth Scholarship

We present CCD imaging, CCD photometry on long and short timescales, and time-resolved spectroscopy of SX LMi, a new SU Ursae Majoris type dwarf nova. The quiescent optical spectrum shows broad double-peaked Balmer, He I, and He II emission lines, similar to other quiescent dwarf novae. Absorption lines from a late-type secondary are not detected. Time-resolved spectra obtained in quiescence reveal radial velocity variations of the Balmer emission lines on a period of 0.06717 ± 0.00011 days, or 96.72 ± 0.16 minutes, with only a slight possibility of a daily cycle-count error. Optical photometry obtained between 1987 and 1991 shows …

The Orbital Period Of Bk Lyncis (Pg 0917 + 342), F. A. Ringwald, J. R. Thorstensen, R. K. Honeycutt, J. W. Robertson

Dartmouth Scholarship

Long-term light curves of the cataclysmic variable BK Lyn = PG 0917 + 342 from the Indiana Automated CCD photometric telescope (‘RoboScope’) and the Harvard College Observatory plate archive reveal no dwarf nova outbursts. Two radial velocity studies show its orbital period to be 107.97 ;1 0.07 min, confirming that it does have an orbital period shorter than the period gap for cataclysmic variables. Whether this is the first nova-like variable below the period gap or a dwarf nova with rare outbursts resembling WZ Sge is still unclear, however.

Orbital Studies Of The Cataclysmic Variables Cz Orionis, V1193 Orionis And Bz Ursae Majoris, F. A. Ringwald, J. R. Thorstensen, R. M. Hamwey

Dartmouth Scholarship

Time-resolved spectroscopy reveals the orbital periods of three cataclysmic variables. CZ Ori has an orbital period of 0.2189 d. This is within 3 per cent of a prediction relating orbital period and dwarf nova outburst decline time. We find the M2.5 ± 1.0 secondary, and infer an absolute magnitude for CZ Ori in RKc of 8.5 ± 1.0 and a distance of 260 ± 110 pc. V1193 Ori, also called Hamuy's Blue Variable, has an orbital period of 0.165 d. In 1988, Ha emission line profile variations suggested red star illumination. In 1989, this line's red wing flared at orbital …