Search

We propose a theory for the MMRD relation of novae, using free-free emission model light curves built on the optically thick wind theory. We calculated $(t_3,M_{V,\rm max})$ for various sets of $(\dot M_{\rm acc}, M_{\rm WD})$, where $M_{V,\rm max}$ is the peak absolute $V$ magnitude, $t_3$ is the 3-mag decay time from the peak, and $\dot M_{\rm acc}$ is the mass accretion rate on to the white dwarf (WD) of mass $M_{\rm WD}$. The model light curves are uniquely characterized by $x\equiv M_{\rm env}/M_{\rm sc}$, where $M_{\rm env}$ is the hydrogen-rich envelope mass and $M_{\rm sc}$ is the scaling mass at which the wind has a certain wind mass-loss rate. For a given ignition mass $M_{\rm ig}$, we can specify the first point $x_0= M_{\rm ig}/M_{\rm sc}$ on the model light curve, and calculate the corresponding peak brightness and $t_3$ time from this first point. Our $(t_3, M_{V,\rm max})$ points cover well the distribution of existing novae. The lower the mass accretion rate, the brighter the peak. The maximum brightness is limited to $M_{V,\rm max} \gtrsim -10.4$ by the lowest mass-accretion rate of $\dot M_{\rm acc} \gtrsim1 \times 10^{-11}~M_\odot$ yr$^{-1}$. A significant part of the observational MMRD trend corresponds to the $\dot M_{\rm acc}\sim5\times10^{-9}~M_\odot$ yr$^{-1}$ line with different WD masses. A scatter from the trend line indicates a variation in their mass-accretion rates. Thus, the global trend of an MMRD relation does exist, but its scatter is too large for it to be a precision distance indicator of individual novae. We tabulate $(t_3, M_{V,\rm max})$ for many sets of $(\dot M_{\rm acc},M_{\rm WD})$., 23 pages, 9 figures, to appear in ApJ

M31 is an ideal laboratory for observing and studying recurrent novae. To date, there have been 18 recurrent nova discovered in M31, six of which have recurrence periods less than nine years. M31N 2017-12a (AT2017jdm) is a transient that was reported near the center of M31, with the time of outburst estimated to be 2017 December 24.141 +/- 0.42 based on constraints from previous data. Here we present the photometric observations of M31N 2017-12a, which we confirm as a recurrence of M31N 2007-10b.

A spectrum of the quiescent counterpart of the Recurrent Nova candidate M31N 1966-08a (= M31N 1968-10c) obtained with LRS2 on the Hobby-Eberly Telescope reveals the object to be a foreground Galactic dMe flare star, and not a nova in M31., Published in Research Notes AAS, Vol. 1, No. 44

The recurrent nova M31N 2008-12a experiences annual eruptions, contains a near-Chandrasekhar mass white dwarf, and has the largest mass accretion rate in any nova system. In this paper, we present Hubble Space Telescope (HST) WFC3/UVIS photometry of the late decline of the 2015 eruption. We couple these new data with archival HST observations of the quiescent system and Keck spectroscopy of the 2014 eruption. The late-time photometry reveals a rapid decline to a minimum luminosity state, before a possible recovery / re-brightening in the run-up to the next eruption. Comparison with accretion disk models supports the survival of the accretion disk during the eruptions, and uncovers a quiescent disk mass accretion rate of the order of $10^{-6}\,M_\odot\,\mathrm{yr}^{-1}$, which may rise beyond $10^{-5}\,M_\odot\,\mathrm{yr}^{-1}$ during the super-soft source phase - both of which could be problematic for a number of well-established nova eruption models. Such large accretion rates, close to the Eddington limit, might be expected to be accompanied by additional mass loss from the disk through a wind and even collimated outflows. The archival HST observations, combined with the disk modeling, provide the first constraints on the mass donor; $L_\mathrm{donor}=103^{+12}_{-11}\,L_\odot$, $R_\mathrm{donor}=14.14^{+0.46}_{-0.47}\,R_\odot$, and $T_\mathrm{eff, donor}=4890\pm110$ K, which may be consistent with an irradiated M31 red-clump star. Such a donor would require a system orbital period $\gtrsim5$ days. Our updated analysis predicts that the M31N 2008-12a WD could reach the Chandrasekhar mass in < 20 kyr., 20 pages, 8 figures, 5 tables, accepted for publication in The Astrophysical Journal

Despite its fundamental importance, a reliable estimate of the Galactic nova rate has remained elusive. Here, the overall Galactic nova rate is estimated by extrapolating the observed rate for novae reaching $m\leq2$ to include the entire Galaxy using a two component disk plus bulge model for the distribution of stars in the Milky Way. The present analysis improves on previous work by considering important corrections for incompleteness in the observed rate of bright novae and by employing a Monte Carlo analysis to better estimate the uncertainty in the derived nova rates. Several models are considered to account for differences in the assumed properties of bulge and disk nova populations and in the absolute magnitude distribution. The simplest models, which assume uniform properties between bulge and disk novae, predict Galactic nova rates of $\sim$50 to in excess of 100 per year, depending on the assumed incompleteness at bright magnitudes. Models where the disk novae are assumed to be more luminous than bulge novae are explored, and predict nova rates up to 30% lower, in the range of $\sim$35 to $\sim$75 per year. An average of the most plausible models yields a rate of $50_{-23}^{+31}$ yr$^{-1}$, which is arguably the best estimate currently available for the nova rate in the Galaxy. Virtually all models produce rates that represent significant increases over recent estimates, and bring the Galactic nova rate into better agreement with that expected based on comparison with the latest results from extragalactic surveys., Accepted for publication in The Astrophysical Journal; 18 pages, 10 figures; analysis expanded to include nova rate estimates and uncertainties based on Monte Carlo simulations

It has been proposed that a galaxy's nova rate might be enhanced by the production of nova progenitor binaries in the dense cores of its globular clusters (GCs). To explore this idea, relative nova rates in three Virgo elliptical galaxies, M87, M49 and M84, which have significantly different GC specific frequencies ($S_{N}$) of 14, 3.6, and 1.6, respectively, were measured over the course of 4 epochs spanning a period of 14 months. To simplify the analysis, observations of the nearly equidistant galaxies were made on the same nights, with the same integration times, and through the same filter (H$\alpha$), so that the relative numbers of novae discovered would reflect the relative nova rates. At the conclusion of our survey we found a total of 27 novae associated with M87, 37 with M49, and 19 with M84. After correcting for survey completeness, we found annual nova rates of $154^{+23}_{-19}$, $189^{+26}_{-22}$, and $95^{+15}_{-14}$, for M87, M49, and M84, respectively, corresponding to $K$-band luminosity-specific nova rates of $3.8\pm1.0$, $3.4\pm0.6$, and $3.0\pm0.6$ novae per year per $10^{10}~L_{K,\odot}$. The overall results of our study suggest that a galaxy's nova rate simply scales with its luminosity, and is insensitive to its GC specific frequency. Two novae, one in M87 and one in M84, were found to be spatially coincident with known GCs. After correcting for the mass fraction in GCs, we estimate that novae are likely enhanced relative to the field by at least an order of magnitude in the GC systems of luminous Virgo ellipticals., Comment: Accepted for publication in The Astrophysical Journal - 11 pages, 6 figures

Multicolor (BVRI) light curves of the eclipsing novalike variable TT Tri are presented and analyzed with a parameter-fitting eclipse model. The mass ratio of TT Tri is poorly constrained, but must lie roughly in the range 0.3>R_1) generally resulted in a higher white dwarf temperature, and a steepening of the disk temperature profile, but were not required to achieve a viable steady-state disk solution. No evidence was found for a luminous bright spot in the system, which is not surprising given the lack of a pre-eclipse "hump" in the light curve. A total of 22 eclipse timings were measured for the system, which yielded an ephemeris for the times of mid-eclipse given by HJD = 2,453,618.953(3) + 0.1396369(4) E. A comparison of the observed brightness and color at mid-eclipse with the photometric properties of the best-fitting model suggests that TT Tri lies at a distance of ~400-500 pc. (abstract abridged), Comment: Submitted to PASP: 37 pages; 9 figures

We examine AAVSO (American Association of Variable Star Observers) light curves of 16 Z Camelopardalis systems with measured orbital periods, with particular focus on intervals away from standstill. During these times, most of the systems display a sawtooth-like outburst behavior, with quiescent intervals comparable to the outburst durations. We report the discovery of a linear relation between the characteristic outburst period and orbital period for these systems, which is given by . AP (days)S p 62.0(7.7)P (days) 2.41(1.87) out orb

As part of an ongoing program to determine the stellar population of novae, a multiepoch Hα survey of the late-type spiral galaxy M33 has been completed. The survey yielded a total of six novae over eight observing seasons in the period between 1995 and 2002. A global nova rate of 2.5 yr-1 is found, which corresponds to a luminosity-specific nova rate of 2.34 ± 0.99 × 10-10 L☉,K yr-1 when the K luminosity is calculated from a B - K color, or 2.17 ± 0.89 × 10-10 L☉,K yr-1 when using the most recent Two Micron All Sky Survey data. Our derived nova rate is significantly different from the previously published rates of 4.6 ± 0.9 and 0.45 yr-1 by Della Valle et al. and Sharov, respectively. When galaxies with measured nova rates are compared, it appears that the Magellanic Clouds (and possibly M87) may have somewhat higher luminosity-specific nova rates than those of M33 and other galaxies. Nevertheless, given the uncertainty in the measured nova rates, we find no compelling evidence that the luminosity-specific nova rate varies strongly or systematically with the Hubble type of the galaxy.

Multicolor (BVRI) light curves have been obtained for the 5.04 hr eclipsing dwarf nova EX Dra. The eclipse profiles have been analyzed with a parameter-fitting model that assumes four sources of luminosity: a white dwarf primary star, an assumed main-sequence secondary star, an accretion disk, and a bright spot at the intersection of the mass-transfer stream and the disk periphery. Model parameters include the temperatures of the white dwarf (T1) and the secondary star (T2), the radius (Rd) and temperature (Td) of the disk periphery, the disk power-law temperature exponent (α), and the bright-spot temperature (Ts). The large eclipse phase width (Δ = 0.109) constrains the orbital inclination i > 83° for plausible mass ratios q (=M2/M1) < 0.81. A matrix of model solutions was computed, covering an extensive range of plausible parameter values. The solution matrix was then explored to determine the optimum values for the fitting parameters and their associated errors. Specifically, the analysis reveals optimum values of T1 = 50,000 ± 20,000 K, Ts = 40,000 ± 10,000 K, Td = 6500 ± 1000 K, Rd/TL1 = 0.50 ± 0.05, α = 0.3 ± 0.2, and B–V = 0.15 ± 0.05 for the EX Dra system. A value of T2 = 3750(±150) K has been fixed in the analysis on the basis of the observed spectral type of the secondary star (M0-M2). An estimate of the absolute magnitude of the secondary star based on this spectral type [8.8 < MV(2) < 9.7] coupled with the observed brightness at mideclipse (V = 16.57 ± 0.05) and an estimated extinction AV = 0.45 ± 0.63 yields a distance to EX Dra of 240 ± 90 pc.

Recently, Shara and collaborators searched for novae in M87 in a series of images originally acquired in HST program #10543 (PI: Baltz), finding a surprisingly high nova rate of $363_{-45}^{+33}$ per year. In an attempt to reconcile this rate with previous ground-based estimates, we have undertaken an independent analysis of the HST data. Our results are in broad agreement with those of Shara et al., although we argue that the global nova rate in M87 remains uncertain, both due to the difficulty in identifying bona fide novae from incomplete lightcurves, and in extrapolating observations near the center of M87 to the entire galaxy. We conclude that nova rates as low as ~200 per year remain plausible.

As part of a program to study the stellar population of novae, multiepoch Hα surveys of M31 have been undertaken. In the first survey, conducted between 1990 and 1993, a total of 53 novae were discovered in 11 CCD fields oriented generally along the major axis of M31. The second survey was conducted between 1995 and 1997, yielding a total of 29 novae in five fields including the outer regions of M31's disk. In both surveys, the spatial distribution of novae is found to follow the background galactic light. However, after decomposing the background B light into its bulge and disk components, the nova distribution is found to follow the bulge light better than the overall light, with the disk light providing a significantly poorer fit. As a check on the possibility that extinction in the disk of M31 is biasing the results, an analysis of the spatial distribution of M31's planetary nebulae—the space density of which is expected to be only weakly affected by stellar population—was also considered. Unlike the nova distribution, the planetary nebula distribution is found to follow the overall background B light remarkably well, establishing that, regardless of extinction, the nova distribution is more centrally concentrated than the planetary nebula distribution. To quantify the results, a maximum likelihood analysis was conducted, and it suggests that ~70% of the novae arise from the bulge, although a bulge fraction as low as 50% cannot be ruled out by the data. A Monte Carlo simulation that makes use of the properties of observed Hα light curves was employed in order to translate the observed nova rate in the central region of M31 to a total bulge nova rate. The procedure was applied to the bulge field of our survey as well as to the Hα bulge survey of Ciardullo and coworkers and to a bulge subset of Arp's extensive B-band survey. In all three cases, the results are remarkably consistent, suggesting a total bulge nova rate of ~25 ± 4 yr-1. Based on the bulge nova rate, an Hα mean lifetime versus Hα absolute magnitude relation is derived, which can be used to estimate the nova rate in galaxies of known distance that have been surveyed in Hα. A second-order relation given by log τc(days) = -(4.78 + 2.10Mc + 0.162M) provides the best fit to the data. Finally, the bulge rate is extrapolated to the entire galaxy assuming the disk-to-bulge nova ratio determined in the maximum likelihood analysis. A global nova rate of ~37 is found, which is somewhat higher than previous estimates of ~30 yr-1 for the overall nova rate in M31. If the luminosity-specific disk and bulge nova rates are comparable, the overall nova rate in M31 could approach 50 yr-1.

Multicolor (BVRI) light curves have been obtained for the newly discovered, 4.21 hr eclipsing dwarf nova RX J0909+1849. The eclipse profiles have been analyzed with a parameter-fitting model to constrain properties of the system. The model assumes four sources of luminosity: the white dwarf primary star and the secondary star (both assumed to radiate as blackbodies) and an accretion disk characterized as a blackbody whose temperature follows a radial power-law distribution: T(r) = Td(Rd/r)α, where Td and Rd are the outer disk temperature and radius, respectively. The model also includes an optically thick bright spot at the intersection of the mass transfer stream and the disk periphery. A matrix of model solutions is computed, which covers an extensive range of plausible parameter values. The solution matrix is then explored to determine the optimum values for the fitting parameters and their associated errors.The mass ratio of RX J0909+1849 is unknown, thus the orbital inclination is not tightly constrained by the model. Five mass ratios have been considered spanning a range of plausible values, 0.3 ≤ q(=M2/M1) ≤ 0.7. Over this range of q, the inclination varies between roughly 74° and 80°. Model parameters include the temperatures of the white dwarf (T1) and the secondary star (T2), the radius (Rd) and temperature (Td) of the disk periphery, the disk power-law temperature exponent (α), and the bright spot temperature (Ts). With the exception of the q = 0.3 models, which required a relatively hot white dwarf (80,000 K), the optimum values of the parameters are nearly constant with mass ratio. For a representative mass ratio of q = 0.5, values of T1 = 26,000±14,000 K, Ts = 18,000±7000 K, Td = 3200±600 K, Rd/RL1 = 0.54±0.08, α = 0.53±0.11, and B–V = 0.45±0.07 are found. A value of T2 = 3400 K has been adopted for all models based on the spectral type of the secondary star (M3-M4).The observed color (B– V = 0.4±0.2) is consistent with the colors given by the model; thus, it is unlikely that RX J0909+1849 suffers significant interstellar absorption. The observed spectral type of the secondary star suggests an absolute magnitude in the range 10.6 < MV(2) < 11.0. After correcting the apparent V magnitude at mideclipse by the fraction of light originating from the secondary star (~94%), a distance of ~200-250 pc is derived for the RX J0909+1849 system.

As part of a program to determine the stellar population of novae, we have conducted a multiepoch Hα survey of the galaxies M51, M87, and M101. A total of nine and 12 novae were detected in the spiral galaxies M51 and M101, respectively, during four epochs of observation, and two epochs of observation yielded a total of nine novae in the giant elliptical galaxy M87. After correcting for the effective survey time and for the fraction of luminosity sampled, we find global nova rates of 18 ± 7, 91 ± 34, and 12 ± 4 novae per year for M51, M87, and M101, respectively. After normalizing to the total K-band luminosity of each galaxy, we estimate luminosity-specific nova rates for M51, M87, and M101 of 1.09 ± 0.47, 2.30 ± 0.99, and 0.97 ± 0.38 novae per year per 1010 solar luminosities in K. When we compare these data with measured values for the luminosity-specific nova rates of other galaxies, we find no compelling evidence for a significant variation with Hubble type. Possible ramifications of this result are discussed within the context of current theoretical models for nova production in galaxies.

The highest field polar AR UMa was observed with ASCA during a low state, and with simultaneous EUVE, RXTE, and ground-based optical photometry during a high state. The marginal detection at the low state places a limit on the hard X-ray emission, which is a factor of 5 below the high-state flux limit. The high-state EUV light curves are highly modulated with peak flux at phase 0.9, but the flux never entirely disappears, implying some view of a heated area at all times of the orbit. The spectra during bright phases suggest a temperature of 265,000 K while the fainter phases are cooler, ~215,000 K, and the spectrum is hottest (320,000 K) during the stream dip phases. However, neither a blackbody nor a standard stellar atmosphere model provides a good fit to the data. In order for the EUV modulation to be consistent with geometrical parameters derived from polarimetry and spectroscopy, the primary heated area on the white dwarf must be geometrically extended from the southern magnetic pole while the northern pole is constantly in view. The temperatures of the heated regions are typical of polars, but the projected areas are small, which could be due to the lack of a good view of the main pole at the low inclination of the system. The RXTE light curve shows no modulation over the orbit and only a marginal detection in hard X-rays, implying a weak bremsstrahlung component that is typical for the highest magnetic field polars. In the optical, a low-amplitude sinusoidal modulation peaking at phase 0.5 is consistent with an origin from the irradiated secondary.

We report photometry and spectroscopy of the dwarf nova EG Cancri in its 1996/1997 episode of eruptions. The main eruption was clearly a superoutburst featuring common superhumps with a period of 0.06036(2) days, establishing the star as a new member of the SU UMa class of dwarf novae. At the end of the main eruption, the superhumps were replaced by another wave of slightly longer period (0.06045 days), which endured for at least another 90 days. The properties of the latter wave suggest identification as a "late superhump." The recurrence time for superoutbursts is long, probably in the range 7-20 yr. After the 15 day superoutburst, the star displayed six remarkable surges in light, with an average interval of 7 days; these "echo outbursts" strongly resemble ordinary dwarf nova eruptions. This suggests that a high accretion rate persisted in the disk for ~40 days after the main superoutburst. By a year after outburst, the star faded to V = 18.7, with most of the continuum light from a white dwarf of T ~ 15,000 K. We estimate a distance of 320 pc and a Mv = +11.5 for accretion light. The extreme faintness, the rarity of eruptions, the enormous duration of superhumps, and the quiescent spectrum together establish membership in the WZ Sge subclass, the most sluggish of dwarf novae. Spectroscopy at quiescence and a transient wave in early outburst establish an orbital period of 0.05997(9) days. This suggests a secondary star with M ~ 0.02 M⊙, yet R ~ 0.08 R⊙. A binary can reach such a state after the secondary is forced to lose mass on a timescale shorter than its Kelvin-Helmholtz timescale.

We present high-quality Hα spectra of the massive X-ray binary HDE 226868 = Cyg X-1 that were made in 1985 and 1986. We measured radial velocities using the He I λ6678 line, and we use the resulting orbital solution together with a Hipparcos light curve of the ellipsoidal variation to arrive at a revised period estimate of P = 5.59977 ± 0.00002 days. We analyze the orbital phase-related variations in Hα emission using a Doppler tomography algorithm, and we show that the profile variations are well matched by a linear combination of two components: a P Cygni profile that moves with the motion of the supergiant star and an emission component that follows an antiphase but phase-shifted velocity curve (semiamplitude Kem = 68 km s-1 and radial velocity maximum at 0 = 0.86; these parameters are similar to those for the He II λ4686 emission line). We use a vector decomposition of this motion to argue that the latter emission component forms between the stars in a focused wind flow from the supergiant to the unseen companion. We searched for but found no clear evidence of Hα emission from the accretion disk surrounding the companion (any such emission contributes less than 3% of the continuum intensity). The results demonstrate that the Hα line provides an important probe of the mass transfer process that eventually fuels the X-ray source.

We present high-quality spectra of the H? emission line of the nova-like variable V Sge, obtained during a photometric bright state during 1986 July. The profiles have several components, including (1) a very broad, flat-topped emission line that forms in the optically thin wind of one of the stars, (2) a central, narrow peak that probably originates in a circumbinary shell, and (3) a moving component that attains an extreme velocity of approach just prior to secondary eclipse (when the brighter and lower mass Roche lobe?filling primary star is in the foreground). We review models for the emission based on the expected collision of the stellar winds of both stars, and suggest that the moving component originates in a high-density region that extends from between the stars to above the leading hemisphere of the primary. The example of V Sge shows that interacting binaries may cease mass transfer in favor of mass ejection from the system at some stage in their evolution.

The Galactic nova rate is poorly known, with estimates in the literature ranging from as few as 11 to as many as 260 yr-1. At the lower end of the spectrum (50 yr-1), the predictions are based on scalings from extragalactic nova surveys, while estimates based on extrapolations of Galactic nova observations suggest rates that are significantly higher, in the range 50-100 yr-1 or more. In an attempt to reconcile this difference, the nova rate, based on Galactic nova observations, is recomputed. If the stellar mass distribution is axisymmetric about the Galactic center, a new estimate of the Galactic nova rate of ~35 ± 11 yr-1 is deduced. Although this value is marginally consistent with the highest estimates based on extragalactic surveys, the agreement is not entirely satisfactory. It is pointed out that a departure from axial symmetry, such as that caused by the presence of a Galactic bar, can potentially lower the estimated nova rate (perhaps approaching 50%) if the bar is sufficiently large, and has its long axis pointed toward the Sun. Alternatively, or perhaps in addition, it is possible that previous extragalactic surveys may have missed a significant fraction of novae (up to a factor of ~2) because of extinction internal to the galaxies. If this latter possibility can be ruled out, for example, through infrared surveys of nearby galaxies, the Galactic nova observations may provide additional support for the existence of a Galactic bar.

The photometric and spectroscopic properties of the 43 known LMC nova candidates are summarized and reviewed. Of these, photometric data sufficient to establish decline rates are available for 29 novae, while spectroscopic data sufficient to establish the spectroscopic classes are available for 18 systems. Half of the 18 novae belong to the Fe II class, with the remaining nine belonging to either the He/N or the Fe IIb classes. As seen in previous nova studies of M31 and M33, the He/N and Fe IIb novae have on average faster photometric developments than do their Fe II counterparts. Overall, the available photometry confirms earlier studies, and shows conclusively that LMC novae have faster rates of decline than do novae in the Galaxy and M31. It appears that the increased fraction of faster, He/N and Fe IIb novae observed in the LMC compared with M31 is almost certainly the result of differences in the underlying stellar population between the two galaxies. We propose that the younger population seen in the LMC compared with M31's bulge (where most of the novae are found) produces progenitor binaries with higher average white dwarf masses. The higher mean white dwarf mass not only produces a larger fraction of fast, He/N novae compared with M31, but also results in a relatively large recurrent nova population., Comment: Accepted for publication in the Astronomical Journal (29 pages, including 5 figures); A few typos in the tables and references have been corrected in V2

In our preceding paper, Liverpool Telescope data of M31 novae in eruption were used to facilitate a search for their progenitor systems within archival Hubble Space Telescope (HST) data, with the aim of detecting systems with red giant secondaries (RG-novae) or luminous accretion disks. From an input catalog of 38 spectroscopically confirmed novae with archival quiescent observations, likely progenitors were recovered for eleven systems. Here we present the results of the subsequent statistical analysis of the original survey, including possible biases associated with the survey and the M31 nova population in general. As part of this analysis we examine the distribution of optical decline times (t(2)) of M31 novae, how the likely bulge and disk nova distributions compare, and how the M31 t(2) distribution compares to that of the Milky Way. Using a detailed Monte Carlo simulation, we determine that 30 (+13/-10) percent of all M31 nova eruptions can be attributed to RG-nova systems, and at the 99 percent confidence level, >10 percent of all M31 novae are RG-novae. This is the first estimate of a RG-nova rate of an entire galaxy. Our results also imply that RG-novae in M31 are more likely to be associated with the M31 disk population than the bulge, indeed the results are consistent with all RG-novae residing in the disk. If this result is confirmed in other galaxies, it suggests any Type Ia supernovae that originate from RG-nova systems are more likely to be associated with younger populations, and may be rare in old stellar populations, such as early-type galaxies., 15 pages, 11 figures, accepted for publication in the Astrophysical Journal

A multi-epoch H-alpha survey of the late-type spiral galaxy NGC 2403 has been completed in order to determine its nova rate. A total of 9 nova candidates were discovered in 48 nights of observation with two different telescopes over the period from February 2001 to April 2012. After making corrections for temporal coverage and spatial completeness, a nova rate of 2.0 (+0.5,-0.3) per year was determined. This rate corresponds to a luminosity-specific nova rate of 2.5+/-0.7 novae per year per 10^{10} solar luminosities in K. This value is consistent with that of the similar Hubble type galaxy, M33, and is typical of those of other galaxies with measured nova rates, which range from 1-3 novae per year per 10^{10} solar luminosities in K., Comment: Accepted for publication in the Astrophysical Journal; 20 pages, 5 figures. Version 2 corrects a few typos and grammatical errors

We report the results of a multi-year spectroscopic and photometric survey of novae in M31 that resulted in a total of 53 spectra of 48 individual nova candidates. Two of these, M31N 1995-11e and M31N 2007-11g, were revealed to be long-period Mira variables, not novae. These data double the number of spectra extant for novae in M31 through the end of 2009 and bring to 91 the number of M31 novae with known spectroscopic classifications. We find that 75 novae (82%) are confirmed or likely members of the Fe II spectroscopic class, with the remaining 16 novae (18%) belonging to the He/N (and related) classes. These numbers are consistent with those found for Galactic novae. We find no compelling evidence that spectroscopic class depends sensitively on spatial position or population within M31 (i.e., bulge vs. disk), although the distribution for He/N systems appears slightly more extended than that for the Fe II class. We confirm the existence of a correlation between speed class and ejection velocity (based on line width), as in the case of Galactic novae. Follow-up photometry allowed us to determine light-curve parameters for a total of 47 of the 91 novae with known spectroscopic class. We confirm that more luminous novae generally fade the fastest, and that He/N novae are typically faster and brighter than their Fe II counterparts. In addition, we find a weak dependence of nova speed class on position in M31, with the spatial distribution of the fastest novae being slightly more extended than that of slower novae., Accepted for publication in the Astrophysical Journal. The manuscript is 123 pages with 29 figures

We present light curves of three classical novae (KT Eridani, V598 Puppis, V1280 Scorpii) and one recurrent nova (RS Ophiuchi) derived from data obtained by the Solar Mass Ejection Imager (SMEI) on board the Coriolis satellite. SMEI provides near complete sky-map coverage with precision visible-light photometry at 102-minute cadence. The light curves derived from these sky maps offer unprecedented temporal resolution around, and especially before, maximum light, a phase of the nova eruption normally not covered by ground-based observations. They allow us to explore fundamental parameters of individual objects including the epoch of the initial explosion, the reality and duration of any pre-maximum halt (found in all three fast novae in our sample), the presence of secondary maxima, speed of decline of the initial light curve, plus precise timing of the onset of dust formation (in V1280 Sco) leading to estimation of the bolometric luminosity, white dwarf mass and object distance. For KT Eri, Liverpool Telescope SkyCamT data confirm important features of the SMEI light curve and overall our results add weight to the proposed similarities of this object to recurrent rather than to classical novae. In RS Oph, comparison with hard X-ray data from the 2006 outburst implies that the onset of the outburst coincides with extensive high velocity mass-loss. It is also noted that two of the four novae we have detected (V598 Pup and KT Eri) were only discovered by ground-based observers weeks or months after maximum light, yet these novae reached peak magnitudes of 3.46 and 5.42 respectively. This emphasizes the fact that many bright novae per year are still overlooked, particularly those of the very fast speed class. Coupled with its ability to observe novae in detail even when relatively close to the Sun in the sky, we estimate that as many as 5 novae per year may be detectable by SMEI., 17 pages, 4 figures, Accepted for publication in the Astrophysical Journal

We report observations of the eclipsing classical nova V368 Aql (Nova Aql 1936 No. 2). These data reveal that the orbital period previously published by Diaz & Bruch is an alias of the true orbital period. A total of 14 eclipses (12 complete and 2 partial) over 25 nights of observation have established that the orbital period of V368 Aql is 0.6905093(1) d (16.57 hr), which is roughly twice the previously published period. With its revised orbital period, V368 Aql now joins other nova systems with periods in excess of 0.5 day that dominate the long end of the orbital period distribution of cataclysmic variables., Accepted for publication in the PASP

We infer that detached binary white dwarfs with orbital periods of a few hours exist because we observe both their progenitors and their descendents. The binary LB 3459 has an orbital period of 6.3 hr and contains a pair of hot subdwaffs that will eventually cool to become white dwarfs (Kilkenny, Hill, and Penfold 1981). L870-2 is a pair of white dwarfs and, given enough time, its 1.55 d orbital period will decay to shorter periods (Saffer, Liebert, and Olszewski 1988). GP Corn, AM CVn, V803 Cen, and PG1346+082 are interacting binary white dwarfs with orbital periods between 1051 s for AM CVn and 46.5 mix for GP Corn (Nather, Robinson, and Stover 1981; Solheim et aL 1984; Wood et al. 1987; O'Donoghue and Kilkenny 1988). These ultrashort period systems must be descendents of detached pairs of white dwarfs. We also expect short-period binary white dwarfs to exist for theoretical reasons. All calculations of the evolution of binary stars show that main-sequence binaries can evolve to binary white dwarfs (e.g., Ibex and Tutukov 1984). Among Population I stars, 1/2 to 2/3 of all main-sequence stars are binaries and about 20% of these binaries should become double white dwarfs with short orbital periods (Abt 1983, Ibex and Tutukov 1986). Thus, about 1/10 of all white dwarfs could be close binaries (Paczynski 1985). Nevertheless, no detached binary white dwarfs with extremely short periods have yet been found. The space density of short-period binary white dwarfs is worth measuring for several reasons. Most generally, the space density, is a test of modern theories for the evolution of binary stars. In addition, short-period binary white dwarfs should be the dominant source of gravitational radiation at periods between about 0.5 mix and 1 hour (e.g., Clark and Epstein 1979, Evans, Iben and Smarr 1987). Plans to build detectors of gravitational radiation at these periods using space-based interferometers are now being seriously considered and this new generation of detectors should be sensitive enough to detect binary white dwarfs (Faller and Bender 1984). Finally, in the most commonly discussed model for Type la supernovae, the progenitor of the supernova is a short-period binary consisting of two white dwarfs with a total mass greater than the Chandrasekhar limit (Webbink 1979; Tutukov and Yungelson 1979; Ibex and Tutukov 1984; Paczynski 1985; Tornamb~ and Matteucci 1986). Gravitational radiation drives the binary to shorter orbital periods and ultimately disrupts the lower mass white dwarf. If enough mass accretes onto the higher-mass white dwarf, its mass will exceed the Chandrasekhar limit and it will collapse

We report a series of extensive photometric and spectroscopic observations of the luminous M31 nova M31N 2007-11d. Our photometric observations coupled with previous measurements show that the nova took at least four days to reach peak brightness at R~14.9 on 20 Nov 2007 UT. After reaching maximum, the time for the nova to decline 2 and 3 magnitudes from maximum light (t_2 and t_3) was ~9.5 and ~13 days, respectively, establishing that M31N 2007-11d was a moderately fast declining nova. During the nova's evolution a total of three spectra were obtained. The first spectrum was obtained one day after maximum light (5 days post-discovery), followed by two additional spectra taken on the decline at two and three weeks post-maximum. The initial spectrum reveals narrow Balmer and Fe II emission with P Cygni profiles superimposed on a blue continuum. These data along with the spectra obtained on the subsequent decline clearly establish that M31N 2007-11d belongs to the Fe II spectroscopic class. The properties of M31N 2007-11d are discussed within the context of other luminous novae in M31, the Galaxy, and the LMC. Overall, M31N 2007-11d appears to be remarkably similar to Nova LMC 1991, which was another bright, slowly-rising, Fe II nova. A comparison of the available data for luminous extragalactic novae suggest that the >~4 day rise to maximum light seen in M31N 2007-11d may not be unusual, and that the rise times of luminous Galactic novae, usually assumed to be, Comment: Accepted for publication in The Astrophysical Journal (28 pages, 6 figures)

A new multi-epoch H-alpha imaging study of M101 (NGC 5457) has been carried out as part of a larger campaign to study the rate and stellar population of extragalactic novae. The survey yielded a total of 13 nova detections from 10 epochs of M101 observations spanning a three year period. After correcting for the temporal coverage and survey completeness, a global nova rate of 11.7^{+1.9}_{-1.5} per year is found. This value corresponds to a luminosity-specific nova rate of 1.23\pm0.27 novae per year per 10^{10} L_{\sun,K} when the K luminosity is derived from the B-K color, or 1.94\pm0.42 novae per year per 10^{10} L_{\sun,K} when the K magnitude from the Two Micron All Sky Survey is used. These values are consistent with previous estimates by Shafter et al. that were based on more limited data. The spatial distribution of the combined nova sample from the present survey and from the earlier Shafter et al. survey shows that the specific frequency of novae closely follows the integrated background light of the galaxy., Comment: 22 pages; 4 figures; accepted for publication in the Astrophysical Journal

Time-resolved CCD photometry is presented of the recently-discovered (V~15 at maximum light) eruptive variable star in Taurus, which we dub VS0329+1250. A total of ~20 hr of data obtained over six nights reveals superhumps in the light curves, confirming the star as a member of the SU UMa class of dwarf novae. The superhumps recur with a mean period of 0.053394(7) days (76.89 min), which represents the shortest superhump period known in a classical SU UMa star. A quadratic fit to the timings of superhump maxima reveals that the superhump period was increasing at a rate given by dP/dt ~ (2.1 +/- 0.8) x 10^{-5} over the course of our observations. An empirical relation between orbital period and the absolute visual magnitude of dwarf novae at maximum light, suggests that VS0329+1250 lies at a distance of ~1.2 +/- 0.2 kpc., Comment: V2 - The paper has been modified to incorporate the referee's comments, and has now been accepted for publication in the PASP. The most significant change is that we are now able to confirm that the superhump period was increasing during the course of our observations

The M 31 nova M31N 2008-12a was recently found to be a recurrent nova (RN) with a recurrence time of about 1 year. This is by far the fastest recurrence time scale of any known RNe. Our optical monitoring programme detected the predicted 2014 outburst of M31N 2008-12a in early October. We immediately initiated an X-ray/UV monitoring campaign with Swift to study the multiwavelength evolution of the outburst. We monitored M31N 2008-12a with daily Swift observations for 20 days after discovery, covering the entire supersoft X-ray source (SSS) phase. We detected SSS emission around day six after outburst. The SSS state lasted for approximately two weeks until about day 19. M31N 2008-12a was a bright X-ray source with a high blackbody temperature. The X-ray properties of this outburst were very similar to the 2013 eruption. Combined X-ray spectra show a fast rise and decline of the effective blackbody temperature. The short-term X-ray light curve showed strong, aperiodic variability which decreased significantly after about day 14. Overall, the X-ray properties of M31N 2008-12a are consistent with the average population properties of M 31 novae. The optical and X-ray light curves can be scaled uniformly to show similar time scales as those of the Galactic RNe U Sco or RS Oph. The SSS evolution time scales and effective temperatures are consistent with a high-mass WD. We predict the next outburst of M31N 2008-12a to occur in autumn 2015., 13 pages, 7 figures, 3 tables; accepted for publication in A&A

The reported positions of 964 suspected nova eruptions in M31 recorded through the end of calendar year 2013 have been compared in order to identify recurrent nova candidates. To pass the initial screen and qualify as a recurrent nova candidate two or more eruptions were required to be coincident within 0.1', although this criterion was relaxed to 0.15' for novae discovered on early photographic patrols. A total of 118 eruptions from 51 potential recurrent nova systems satisfied the screening criterion. To determine what fraction of these novae are indeed recurrent the original plates and published images of the relevant eruptions have been carefully compared. This procedure has resulted in the elimination of 27 of the 51 progenitor candidates (61 eruptions) from further consideration as recurrent novae, with another 8 systems (17 eruptions) deemed unlikely to be recurrent. Of the remaining 16 systems, 12 candidates (32 eruptions) were judged to be recurrent novae, with an additional 4 systems (8 eruptions) being possibly recurrent. It is estimated that ~4% of the nova eruptions seen in M31 over the past century are associated with recurrent novae. A Monte Carlo analysis shows that the discovery efficiency for recurrent novae may be as low as 10% that for novae in general, suggesting that as many as one in three nova eruptions observed in M31 arise from progenitor systems having recurrence times, Comment: Accepted for Publication in The Astrophysical Journal Supplement (81 pages, 48 figures, 6 tables)

An estimate of the nova rate in M33 provides a valuable constraint on the rate of nova production in a disk‐dominated, essentially bulgeless galaxy. Presented here are the preliminary results of a new Hα survey for novae in M33. Data analyzed thus far includes the inner 13′ × 13′ of the galaxy, yielding four novae detected to a limiting magnitude of mHα ≃ 17.5 ± 0.3. After correcting for the fraction of M33 covered in the survey, a preliminary nova rate for M33 of 4 ± 2 yr−1 is found.

Despite its fundamental importance and a considerable expenditure of observational effort, a reliable estimate of the Galactic nova rate has remained elusive. In this review recent estimates of the Galactic nova rate are critically examined and the problems associated with the determination of the Galactic nova rate are discussed. After considering how the observed properties of novae may depend on the underlying stellar population, a new estimate of the Galactic nova rate is presented based both on Galactic data and on a comparison with the nova rate in M31. Agreement between these two different approaches is found to be satisfactory, with the Galactic data yielding a rate of ∼ 30 yr−1 and the extragalactic data suggesting a somewhat smaller value of ∼ 25 yr−1. After considering likely sources of uncertainty in both the Galactic and extragalactic analyses, a value of 30 ± 10 yr−1 is suggested as the current best estimate of the Galactic nova rate.

We report preliminary results from a new program of observations of novae in nearby galaxies. The principal goal of the program is to explore the population of nova progenitors through observations of galaxies having a wide range of Hubble types. Here we present preliminary results from observations of the spiral systems M51 and M101, and the giant elliptical, M87. Based on available data, we find no evidence that the luminosity specific nova rate varies across the Hubble sequence.

We report the initial results from an ongoing multi-year spectroscopic survey of novae in M33. The survey resulted in the spectroscopic classification of six novae (M33N 2006-09a, 2007-09a, 2009-01a, 2010-10a, 2010-11a, and 2011-12a) and a determination of rates of decline (t_2 times) for four of them (2006-09a, 2007-09a, 2009-01a, and 2010-10a). When these data are combined with existing spectroscopic data for two additional M33 novae (2003-09a and 2008-02a) we find that 5 of the 8 novae with available spectroscopic class appear to be members of either the He/N or Fe IIb (hybrid) classes, with only two clear members of the Fe II spectroscopic class. This initial finding is very different from what would be expected based on the results for M31 and the Galaxy where Fe II novae dominate, and the He/N and Fe IIb classes together make up only ~20% of the total. It is plausible that the increased fraction of He/N and Fe IIb novae observed in M33 thus far may be the result of the younger stellar population that dominates this galaxy, which is expected to produce novae that harbor generally more massive white dwarfs than those typically associated with novae in M31 or the Milky Way., 30 pages; 5 figures; accepted for publication in the Astrophysical Journal; second version corrects some references to Table 3, and a few typos

Les observations spectroscopiques de l'emission Hα emanant du disque d'accretion dans la binaire A 0620-00 sont presentees. L'emission revele des variations de la vitesse radiale au niveau de la periode orbitale. Il est suggere que ces variations refletent le mouvement orbital de l'objet compact. La determination du rapport des masses resulte en de nouvelles limites inferieures sur les masses des composantes : 3.82 ± 0.24 M ○. pour l'objet compact, renforcant l'hypothese d'un trou noir, et 0.36 ± 0.07 M ○. pour l'etoile K.

We present observations of the old nova HZ Pup (Nova Pup 1963 No. 1) showing it to be an intermediate polar with an exceptionally rich selection of photometric periodicities arising from spin and orbital variations and beating between these two.

High-speed photometric UBV observations of the nova-like variable V Sagittae conducted during 1994 and 1995 are reported. The data consist of a total of 152 hours of observations, covering the entire 12.3 hr orbital period. Analysis of the photometry using the new Wilson eclipsing-binary code suggests a model where mass is being transferred from a 0.86 Msun, evolved, Helium-burning star, which fills its Roche lobe, to a 3.48 Msun evolved companion. Thirteen new timings of primary eclipse in conjunction with published timings from 1946 to 1996 show that the orbital period is changing at a rate dot {P} = -5.1(± 1.0) x 10-10 . We derive a lower limit to the mass loss rate from the primary star of dot {M1} ~ -4.4(± 0.1) x 10-7 Msun yr-1 . V Sge appears to be in a short-lived evolutionary state with a lifetime of ~ 2 x 106 yr.

Time-resolved photometric observations of the classical novae DO Aql and V849 Oph have been obtained using the Mount Laguna Obervatory CCD photometer. The data reveal that both systems are eclipsing. A total of 6 eclipses were obtained for DO Aql and 4 for V849 Oph, allowing us to determine orbital periods of 0.1677624 day and 0.1727553 day, respecitvely. The eclipse profiles of both systems are asymmetric and are relatively shallow: ~0.5 mag in the case of DO Aql and ~1 mag for V849 Oph. The shallow DO aql eclipse suggests that the white dwarf and the inner disk are never occulted. Interestingly, the eclipse profiles of both systems show broad and shallow depressions or "dips" immediately preceding eclipse. The phasing of htese depressions suggests obscuration of the central region of the disk by a thickened disk rim in the vicinity of the bright spot, or by stream overshoot, or both.

Observations are presented of an extremely slow nova that was discovered in the bulge of M31 in 1986. The evolution of the object was monitored with subsequent yearly spectra until 1990, as part of a general spectroscopic survey of novae in M31 underway at McDonald Observatory. The spectra cover the nova's evolution in the nebular phase, and these observations have made this nova the most extensively observed extragalactic nova to date. This has provided a unique opportunity to make the first detailed comparison of the evolution and properties of an extragalactic nova with those in our own Galaxy

For many years VY Aquarii has been regarded as a charter member of the class fo recurrent novae, because it erupted several times, with outburst amplitudes of ~8 mag, exceeding those normally attributed to dwarf novae. We present observations obtained both in quiescence and eruption that emphasize the great similarity of the star to well-credentialed dwarf novae like WZ Sagittae. Long-term visual and photographic coverage shows two types of eruptions, differing in brightness and timescale by a factor of ~5. A transient wave in the quiescent light curve suggests a period in the range 80-120 minutes, which could be the orbital period of the underlying binary. Photometry during a long eruption in 1986 showed a large-amplitude modulation ("superhump") with a period of 92.7 (or possibly 99.1) minutes, which slowly decreased during the eruption. These are normal signatures of SU Ursae Majoris stars, a subclass of dwarf novae. The superhumps observed in SU UMa stars appear to show a similar degree of period instability, such that P ~ -(3-10)X10-5. Perhaps a more physically significant expression of this is a period-magnitude law: the periods decrease by 0.64±0.10% per magnitude of decline,_ at least during the early decline. This is a plausible decrease to expect from the precessing-disk model for the origin of superhumps, assuming the disk to be largest near maximum light.

Results are presented from a 3 year (1987-1989) spectroscopic and photometric survey of novae in M31's bulge, the first comprehensive study of novae outside the Galactic and Magellanic Cloud systems. Nine novae were detected and monitored and their spectra cover a range of outburst states from early decline to the early nebular phases. Broad agreement in spectral morphology and evolution is found with Galactic novae. Since Galactic novae are mainly disk objects, this indicates that novae outburst properties are not critically dependent on the metallicity of the progenitor population