Permanent Superhump Research Articles

Superhumps in Cataclysmic Binaries. XIV. V592 Cassiopeiae

ABSTRACTWe report a spectroscopic and photometric study of the novalike variable V592 Cassiopeiae (=LS I 55° 8). The spectrum is that of a typical UX UMa–type star, with weak, narrow Balmer emission superposed on broad absorption. The 0.1–2.2 μm flux distribution also looks fairly normal, suggesting disk accretion at ∼10−8 M⊙ yr−1 and a distance of 330 pc. The emission lines move with P = 0.115063(1) days, which is presumably the underlying orbital period of the binary. Photometry reveals a different period, namely, 0.12228(1) days. The presence of this wave in a short‐period cataclysmic variable, and the value of the period excess at 6.3%, suggests identification as a “permanent superhump.” After subtraction of this large signal, the residual time series appears to contain a weak feature at 0.11193(5) days. The star evidently shows positive and negative superhumps simultaneously. Its binary period puts it among a modest number of nonmagnetic cataclysmic variables occupying the 2–3 hr period “gap.”

Predicting the future of superhumps in classical nova systems

Oscillations observed in the light curve of Nova V1974 Cygni 1992 since summer 1994 have been interpreted as permanent superhumps. From simple calculations based on the Tidal-Disk Instability model of Osaki, and assuming that the accretion disc is the dominant optical source in the binary system, we predict that the nova will evolve to become an SU UMa system as its brightness declines from its present luminosity by another 2-3 magnitudes. Linear extrapolation of its current rate of fading (in magnitude units) puts the time of this phase transition within the next 2-4 years. Alternatively, the brightness decline will stop before the nova reaches that level, and the system will continue to show permanent superhumps in its light curve. It will then be similar to two other old novae, V603 Aql and CP Pup, that still display the permanent superhumps phenomenon 79 and 55 years, respectively, after their eruptions. We suggest that non-magnetic novae with short orbital periods could be progenitors of permanent superhump systems.

The Orbital Period of AM Canum Venaticorum

We report the discovery of a strictly periodic signal at 1028.7325±0.0004 s in the light curve of the cataclysmic variable AM Canum Venaticorum. This brings to an end the long search for the true binary period of this important star, which represents the latest known stage of binary star evolution. It provides a more secure and quantitative basis for testing theories of binary evolution. And it provides strong evidence in favor of the "permanent superhump" interpretation of this star and other cataclysmic variables of extreme mass ratio.

Permanent superhumps in nova V1974 Cygni (1992)

We observed V1974 Cygni with a CCD camera attached to the 1-m telescope of the Wise Observatory for 32 nights during the years 1994 and 1995. The two periodicities identified in the light curve, 0.0812585 day 1.95 hours and 0.085 d P..1 2.04 hr, are interpreted as the orbital period of the binary system and a superhump period, respectively. These results and the interpretation imply that no later than 2.5 years after the outburst of the nova an accretion disk is present in the nova stellar system. They also imply that the disk is in the state of “permanent superhump”. Using the precessing disk model of the superhump phenomenon and utilizing additional published observational results we estimate a mass of 0.75–1.07 M⊙ for the white dwarf in this nova system.

Photometric Evidence for the Presence of An Accretion Disk and for a Superhump - Like Phenomenon in the Classical Nova V1974 Cygni 1992

AbstractThe light curve of V1974 Cyg shows two distinct periodicities. The shorter periodicity is clearly the orbital period of the binary system. We show that the longer variation has similar features to permanent superhumps. This result indicates the existence of an accretion disk in the system no later than 30 months after the nova outburst. We used the precessing disk model of the superhump phenomenon and previous results in order to estimate that the white dwarf mass is at the range 0.75 – 1.07 M⊙.

Population Studies of Cataclysmic Variables

Cataclysmic variables (CVs) are idiosyncratic objects, but progress can be made by studying groups of them. To do this, one must identify samples that are representative of their true properties. Because of the wide variety of physics that occurs in CVs, they have a complex phenomenology in which effects are still being discovered (e.g. permanent superhumps: Patterson & Richman 1991). CV outbursts have their own complex phenomenology (but see Osaki 1995a,b and this volume, for ideas on unification for dwarf novae), so it is unwise to rely on outburst properties to give unbiased samples.One wants to identify CVs by some property common to all of them. One such property is flickering; another is color excess. CVs are very blue, especially in the ultraviolet, with U – B < −0.46 for 95% of CVs (Bruch & Engel 1994). This color index also defines inclusion in the Palomar-Green (PG) survey (Green, Schmidt & Liebert 1986), and a preliminary list of PG CVs was given by Green et al. (1982). My Ph.D. thesis (Ringwald 1993) completed this work, being the first optically selected complete sample of CVs at high latitude. At the same time, Andy Silber was writing his Ph.D. thesis on an X-ray-selected sample of CVs, from the HEAO-A1 MC-LASS survey (Silber 1992). One might say I was Andy’s optical counterpart.

Non Circular Disks in am CVn Systems?

The AM CVn stars are mass transferring, interacting binary, white dwarf systems with orbital periods of 15…45 minutes. Hydrogen is completely lost from these systems, and we observe small helium disks which may show thermal and tidal instabilities if the mass transfer rate is large enough (Osaki 1995). A tidal instability brings the disk into a superoutburst state, and in the light curve we may observe superhumps. Based on the observed periods and mass transfer rates we can divide the AM CVn stars into three groups:A: In permanent superoutburst: AM CVn and EC 15330-1403B: Regular superoutbursts: CR Boo, V803 Cen and CP EriC: Not yet observed superoutburst: GP ComGroup A consists of systems with disks which are too hot to decline into a low state. These disks are in a constant superoutburst state, analogous to nova-like CVs which show no outbursts, but still exhibit permanent superhumps (Skillman & Patterson 1993). Group B shows normal outbursts which can trigger superoutbursts, analogous to the VY Scl dwarf novae. The group C object may also be a superhumper, but with very infrequent outbursts analogous to the SU UMa stars (Warner 1995). In the following we will discuss evidence for superoutbursts in these systems, and the likelihood for these systems to develop elliptical disks.

Time-resolved CCD photometry of a sample of Palomar-green cataclysmic variable candidates

view Abstract Citations (57) References (36) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Time-Resolved CCD Photometry of a Sample of Palomar-Green Cataclysmic Variable Candidates Misselt, K. A. ; Shafter, A. W. Abstract We present the results of a photometric study of 12 cataclysmic variables from the Palomar-Green survey of high-galactic-latitude ultraviolet excess objects. Nine of the twelve (PG 0917+342, PG 0943+521, PG 1114+187, PG 1119+147, PG 1316+678, PG 1510+234, PG 1524+622, PG 1633+115, and PG 2133+115) are part of Ringwald's magnitude-limited sample of cataclysmic variables. Among these nine, we identify an unusual new SU UMa dwarf nova PG 0943+521, and find a superhump period Psh = 0.0656 +/- 0.0001d. We confirm the presence of permanent superhumps in the nova-like variable PG 0917+342. We find photometric periodicities in PG 1633+115, but an aliasing problem prohibits us from distinquishing between periods of 3.94h, 3.43h, and 3.38h. PG 1510+234 exhibits large scale brightness variations, but shows no evidence of any photometric periodicity. Three objects PG 114+187, PG 1119+147, and PG 1316+678, exhibit no obvious variability and are unlikely to be cataclysmic variables. Of the remaining three objects not in the complete sample, PG 0240+066. PG 1116+349, and PG 0911-066, we identify the latter as a likely dwarf nova, possibly of the WZ Sge subtype, and we find a photometric period, possibly orbital in nature, of P = 82.931 +/- 0.001 min. PG 0240+066 and PG 116+349 exhibited no variability during our observations and are unlikely to be cataclysmic variables. Finally, we briefly examine the fraction of eclipsing cataclysmic variables in the sample as it relates to the importance of selection effects. Publication: The Astronomical Journal Pub Date: April 1995 DOI: 10.1086/117406 Bibcode: 1995AJ....109.1757M Keywords: Astronomical Photometry; Brightness; Cataclysmic Variables; Charge Coupled Devices; Dwarf Novae; Periodic Variations; Sky Surveys (Astronomy); Temporal Resolution; Astronomy; CATACLYSMIC VARIABLES; BINARIES: ECLIPSING full text sources ADS | data products SIMBAD (12)

PERMANENT SUPERHUMPS IN V603 AQUILAE

ABSTRACT The results of an intensive program of photometry of the old nova V603 Aquilae (= Nova Aquilae 1918) are reported. In four separate observing runs of high-speed photometry, totaling 15 nights, no evidence is found for previously reported signals with periods of 61.4 and 15.6 minutes, or any other coherent signal with a period in the range 20 seconds to 3 hours. This makes it very unlikely that the star contains a strongly magnetic white dwarf, as has been suggested. The light curves do consistently show a slow wave with a period of about 3.5 hours, about 5 percent longer than the accepted orbital period. This period is stable on time scales of at least a few weeks. Published observations are too scarce to determine a long-term ephemeris, but the period increased between 1981 and 1990 at a mean rate of about 5 seconds/year. Several models for the origin of the periodicity are discussed. There is some resemblance to the well-known 'superhumps' of the SU Ursae Majoris class of dwarf novae. This suggests that the star may be stuck in a more or less permanent state of high mass transfer, with the photometric period arising from the precession of an eccentric accretion disk.