In 1975, E. R. Robinson conducted the hallmark study of the behavior of classical nova light curves before eruption, and this work has now become part of the standard knowledge of novae. He made three points; that 5 out of 11 novae showed pre-eruption rises in the years before eruption, that one nova (V446 Her) showed drastic changes in the variability across eruptions, and that all but one of the novae (excepting BT Mon) have the same quiescent magnitudes before and after the outburst. This work has not been tested since it came out. We have now tested these results by going back to the original archival photographic plates and measuring large numbers of pre-eruption magnitudes for many novae using comparison stars on a modern magnitude scale. We find in particular that four out of five claimed pre-eruption rises are due to simple mistakes in the old literature, that V446 Her has the same amplitude of variations across its 1960 eruption, and that BT Mon has essentially unchanged brightness across its 1939 eruption. Out of 22 nova eruptions, we find two confirmed cases of significant pre-eruption rises (for V533 Her and V1500 Cyg), while T CrB has a deep pre-eruption dip. These events are a challenge to theorists. We find no significant cases of changes in variability across 27 nova eruptions beyond what is expected due to the usual fluctuations seen in novae away from eruptions. For 30 classical novae plus 19 eruptions from 6 recurrent novae, we find that the average change in magnitude from before the eruption to long after the eruption is 0.0 mag. However, we do find five novae (V723 Cas, V1500 Cyg, V1974 Cyg, V4633 Sgr, and RW UMi) that have significantly large changes, in that the post-eruption quiescent brightness level is over ten times brighter than the pre-eruption level.
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 publ…
We report on the recovery of the six old novae EL Aql, V606 Aql, V908 Oph, V1149 Sgr, V1583 Sgr and V3964 Sgr, using photometric and spectroscopic data. Analysing several properties, we find that EL Aql is a good candidate for an intermediate polar. Furthermore, the system inclination of EL Aql, V606 Aql, V1583 Sgr and V3964 Sgr appears to be sufficiently high to suggest them as good targets for time series observations. We also eliminate some previously suggested candidates for the post-novae V1301 Aql and V1151 Sgr.
We present the analysis of photometric and spectroscopic data on eight candidates for post-nova systems. Five post-novae, V528 Aql, HS Sge, BS Sgr, GR Sgr and V999 Sgr, are successfully recovered. We furthermore identify likely candidates for the fields of V1301 Aql, V1151 Sgr and V3964 Sgr. The spectroscopic properties of the confirmed post-novae are briefly discussed. We find that two of the oldest post-novae in our sample, GR Sgr and V999 Sgr, contain an optically thick accretion disc, and thus can be suspected to have a high mass-transfer rate, contrary to what one would expect from most m…
We identify a new class of novae characterized by the post-eruption quiescent light curve being more than roughly a factor of ten brighter than the pre-eruption light curve. Eight novae (V723 Cas, V1500 Cyg, V1974 Cyg, GQ Mus, CP Pup, T Pyx, V4633 Sgr, and RW UMi) are separated out as being significantly distinct from other novae. This group shares a suite of uncommon properties, characterized by the post-eruption magnitude being much brighter than before eruption, short orbital periods, long-lasting supersoft emission following the eruption, a highly magnetized white dwarf, and secular declin…
The impact of nova eruptions on the long-term evolution of Cataclysmic Variables(CVs) is one of the least understood and intensively discussed topics in the field. Acrucial ingredient to improve with this would be to establish a large sample of post-novae with known properties, starting with the most easily accessible one, the orbitalperiod. Here we report new orbital periods for six faint novae: X Cir (3.71 h), ILNor (1.62 h), DY Pup (3.35 h), V363 Sgr (3.03 h), V2572 Sgr (3.75 h) and CQ Vel(2.7 h). We furthermore revise the periods for the old novae OY Ara, RS Car, V365Car, V849 Oph, V728 Sc…
The dwarf nova Z Camelopardalis is surrounded by the largest known classical nova shell. This shell demonstrates that at least some dwarf novae must have undergone classical nova eruptions in the past, and that at least some classical novae become dwarf novae long after their nova thermonuclear outbursts. The current size of the shell, its known distance, and the largest observed nova ejection velocity set a lower limit to the time since Z Cam's last outburst of 220 years. The brightest part of the Z Cam shell's radius is currently p ~ 1690 pixels. No expansion of the radius of the brightest p…
We have started a project to investigate the connection of post-novae with the population of cataclysmic variables. Our first steps in this concern improving the sample of known post-novae and their properties. Here we present the recovery and/or confirmation of the old novae MT Cen, V812 Cen, V655 CrA, IL Nor, V2109 Oph, V909 Sgr, V2572 Sgr, and V728 Sco. Principal photometric and spectroscopic properties of these systems are discussed. We find that V909 Sgr is a probable magnetic CV, and that V728 Sco is a high-inclination system. We furthermore suggest that the two candidate novae V734 Sco …
I report on the cumulative results from a program started 24 years ago designed to measure the orbital period change of recurrent novae (RNe) across an eruption. The goal is to use the orbital period change to measure the mass ejected during each eruption as the key part of trying to measure whether the RNe white dwarfs are gaining or losing mass over an entire eruption cycle, and hence whether they can be progenitors for Type Ia supernovae. This program has now been completed for two eclipsing RNe; CI Aquilae (CI Aql) across its eruption in 2000 and U Scorpii (U Sco) across its eruption in 19…
Recurrent novae (RNe) are cataclysmic variables with two or more nova eruptions within a century. Classical novae (CNe) are similar systems with only one such eruption. Many of the so-called 'CNe' are actually RNe for which only one eruption has been discovered. Since RNe are candidate Type Ia supernova progenitors, it is important to know whether there are enough in our galaxy to provide the supernova rate, and therefore to know how many RNe are masquerading as CNe. To quantify this, we collected all available information on the light curves and spectra of a Galactic, time-limited sample of 2…
We present data on 13 post-nova systems. This includes the recovery via UBVR photometry of the five post-novae X Cir, V2104 Oph, V363 Sgr, V928 Sgr and V1274 Sgr and their spectroscopic confirmation. We provide accurate coordinates and finding charts for those objects. Additional first-time or improved spectroscopic data are presented for V356 Aql, V500 Aql, V604 Aql, V1370 Aql, MT Cen, V693 CrA, V697 Sco and MU Ser. Investigating the behaviour of a few easily accessible parameters yields (limited) information on the accretion state and the system inclination. We predict that X Cir and V697 Sc…
I collect virtually all photometry of the ten known galactic recurrent novae (RNe) and their 37 known eruptions. This consists of my modern measures of nearly all archival plates (providing the only data for half of 37 known eruptions), my own 10,000 CCD magnitudes from 1987 to present (providing virtually all of the magnitudes in quiescence for seven RNe), over 140,000 visual magnitude estimates recorded by amateur astronomers (who discovered half the known eruptions), and the small scattering of magnitudes from all the literature. From this, I produce various uniform products; (1) BVRIJHK co…
Eruptions of classical novae are possible sources of lithium formation and gamma-ray emission. Nova remnants can also become Type Ia supernovae (SNe Ia). The contribution of novae to these phenomena depends on nova rates, which are not well established for the Galaxy. Here, we directly measure a Galactic bulge nova rate of $13.8 \pm 2.6$ per year. This measurement is much more accurate than any previous measurement of this kind thanks to many years' monitoring of the bulge by the Optical Gravitational Lensing Experiment (OGLE) survey. Our sample consists of 39 novae eruptions, $\sim$1/3 of whi…
IW And-type dwarf novae are recently recognized group of cataclysmic variables which are characterized by a sequence of brightening from a standstill-like phase with damping oscillations often followed by a deep dip. We found that the supposed classical nova BC Cas which erupted in 1929 experienced a state of an IW And-type dwarf nova in 2018, 89 yr after the eruption. This finding suggests that high mass-transfer rate following the nova eruption is associated with the IW And-type phenomenon. The mass of the white dwarf inferred from the decline rate of the nova is considerably higher than the…
Models have long predicted that the frequency-averaged masses of white dwarfs in Galactic classical novae are twice as large as those of field white dwarfs. Only a handful of dynamically well-determined nova white dwarf masses have been published, leaving the theoretical predictions poorly tested. The recurrence time distributions and mass accretion rate distributions of novae are even more poorly known. To address these deficiencies, we have combined our extensive simulations of nova eruptions with the Strope et al (2010) and Schaefer et al (2010) databases of outburst characteristics of Gala…
Observations of novae at radio frequencies provide us with a measure of the total ejected mass, density profile and kinetic energy of a nova eruption. The radio emission is typically well characterized by the free-free emission process. Most models to date have assumed spherical symmetry for the eruption, although it has been known for as long as there have been radio observations of these systems, that spherical eruptions are to simplistic a geometry. In this paper, we build bipolar models of the nova eruption, assuming the free-free process, and show the effects of varying different paramete…
We present time-series photometric and spectroscopic data for seven old novae. They are used to derive the orbital period for the systems V365 Car (5.35 h), AR Cir (5.14 h), V972 Oph (6.75 h), HS Pup (6.41 h), V373 Sct (3.69 h), V909 Sgr (3.43 h) and CN Vel (5.29 h). Their addition increases the number of orbital periods for novae by ~10 per cent. The eclipsing nature of V909 Sgr is confirmed, and in three other cases (V365 Car, Ar Cir and V373 Sct) we detect significant photometric orbital variability with amplitudes >=0.2 mag in R. The resulting period distribution is briefly discussed. We f…
We report the results of a survey of M31 novae in quiescence. This is the first catalog of extragalactic systems in quiescence to be published, and contains data for 38 spectroscopically confirmed novae from 2006 to 2012. We used Liverpool Telescope (LT) images of each nova during eruption to define an accurate position for each system. These positions were then matched to archival Hubble Space Telescope (HST) images and we performed photometry on any resolved objects that were coincident with the eruption positions. The survey aimed to detect quiescent systems with red giant secondaries, as o…
The extensive grid of numerical simulations of nova eruptions of Yaron et al.(2005) first predicted that some classical novae might deviate significantly from the Maximum Magnitude - Rate of Decline (MMRD) relation, which purports to characterise novae as standard candles. Kasliwal et al. (2011) have announced the observational detection of an apparently new class of faint, fast classical novae in the Andromeda galaxy. These objects deviate strongly from the MMRD relationship, exactly as predicted by Yaron et al. (2005). Shara et al. (2016) recently reported the first detections of faint, fast…
We present a preliminary comparison of the post-nova population with that of general cataclysmic variables (CVs). We particularly focus on the mass-transfer rate and its potential relation to the nova eruption. We find that the known post-nova sample exclusively consists of high mass-transfer CVs, but that this is more likely to be due to the shorter recurrent time for those systems, rather than the mass-transfer rate being affected by the eruption. Nevertheless, we find evidence for such an effect for specific post-novae, and that it is potentially related to the binary separation and to pres…
The eruption of a (classical) nova is widely accepted to be a recurrent event in the lifetime of a cataclysmic binary star. In-between eruptions the system should therefore behave as a "normal" cataclysmic variable (CV), i.e. according to its characteristic properties like the mass-transfer rate or the strength of the magnetic field of the white dwarf. How important are these characteristics for the nova eruption itself, i.e. which type of systems preferably undergo a nova eruption? This question could in principle be addressed by comparing the post-nova systems with the general CV population.…
The population of classical novae in the Magellanic Clouds was poorly known because of a lack of systematic studies. There were some suggestions that nova rates per unit mass in the Magellanic Clouds were higher than in any other galaxy. Here, we present an analysis of data collected over 16 years by the OGLE survey with the aim of characterizing the nova population in the Clouds. We found 20 eruptions of novae, half of which are new discoveries. We robustly measure nova rates of $2.4 \pm 0.8$ yr$^{-1}$ (LMC) and $0.9 \pm 0.4$ yr$^{-1}$ (SMC) and confirm that the K-band luminosity-specific nov…
We report on multiwavelength observations of nova SMCN 2016-10a. The present observational set is one of the most comprehensive for any nova in the Small Magellanic Cloud, including: low, medium, and high resolution optical spectroscopy and spectropolarimetry from SALT, FLOYDS, and SOAR; long-term OGLE $V$- and $I$- bands photometry dating back to six years before eruption; SMARTS optical and near-IR photometry from $\sim$ 11 days until over 280 days post-eruption; $Swift$ satellite X-ray and ultraviolet observations from $\sim$ 6 days until 319 days post-eruption. The progenitor system contai…
A TESS View of Post-Eruption Variability in the Novae V1405 Cas,V1716 Sco, and V1674 Her
Universidad Nacional de Hurlingham (UNAHUR)（乌尔希林国立大学）；Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)（国家科学研究委员会）；Advanced Technologies Research Institute, Faculty of Materials Science and Technology in Trnava, Slovak University of Technology in Bratislava（布拉迪斯拉发斯洛伐克技术大学特伦材料科学与技术学院先进技术研究所）；INAF-Osservatorio Astronomico di Padova（帕多瓦天文台）；Department of Astronomy, University of Wisconsin（威斯康星大学天文学系）
The hydrogen-rich envelopes accreted by white dwarf stars from their red dwarf companions lead to thermonuclear runaways observed as classical nova eruptions peaking at up to 1 Million solar luminosities. Virtually all nova progenitors are novalike binaries exhibiting high rates of mass transfer to their white dwarfs before and after an eruption. It is a puzzle that binaries indistinguishable from novalikes, but with much lower mass transfer rates, and resulting dwarf nova outbursts, co-exist at the same orbital periods. Nova shells surrounding several dwarf novae demonstrate that at least som…
Orbital Period Changes for Fourteen Novae and the Critical Failures of the Predictions of Standard Theories, the Hibernation Model, and the Magnetic Braking Model
We use a combined binary evolution code including dynamical effects to study nova eruptions in a symbiotic system. Following the evolution, over $\sim10^5$ years, of multiple consecutive nova eruptions on the surface of a $1.25M_\odot$ white dwarf (WD) accretor, we present a comparison between simulations of two types of systems. The first is the common, well known, cataclysmic variable (CV) system in which a main sequence donor star transfers mass to its WD companion via Roche-lobe overflow. The second is a detached, widely separated, symbiotic system in which an asymptotic giant branch donor…
Estimates of the accretion rate in symbiotic recurrent novae (RNe) often fall short of theoretical expectations by orders of magnitude. This apparent discrepancy can be resolved if the accumulation of mass by the white dwarf (WD) is highly sporadic, and most observations are performed during low states. Here we use a reanalysis of archival data from the Digital Access to a Sky Century @Harvard (DASCH) survey to argue that the most recent nova eruption in symbiotic RN T CrB, in 1946, occurred during -- and was therefore triggered by -- a transient accretion high state. Based on similarities in …
The Andromeda Galaxy recurrent nova M31N 2008-12a had been caught in eruption eight times. The inter-eruption period of M31N 2008-12a is ~1 year, making it the most rapidly recurring system known, and a strong single-degenerate Type Ia Supernova progenitor candidate. Following the 2013 eruption, a campaign was initiated to detect the predicted 2014 eruption and to then perform high cadence optical photometric and spectroscopic monitoring using ground-based telescopes, along with rapid UV and X-ray follow-up with the Swift satellite. Here we report the results of a high cadence multicolour opti…
We report a 20-year campaign to track the 1.8 hour photometric wave in the recurrent nova T Pyxidis, using the global telescope network of the Center for Backyard Astrophysics. During 1996-2011, that wave was highly stable in amplitude and waveform, resembling the orbital wave commonly seen in supersoft binaries. The period, however, was found to increase on a timescale P/P-dot=3x10^5 years. This suggests a mass transfer rate in quiescence of ~10^-7 M_sol/yr, in substantial agreement with the accretion rate based on the star's luminosity. This is ~2000x greater than is typical for cataclysmic …
Extremely luminous, red eruptive variables like RV in M31 are being suggested as exemplars of a new class of astrophysical object. Our greatly extended series of nova simulations shows that classical nova models can produce very red, luminous eruptions. In a poorly studied corner of 3-D nova parameter space (very cold, low-mass white dwarfs, accreting at very low rates) we find bona fide classical novae that are very luminous and red because they eject very slowly moving, massive envelopes. A crucial prediction of these nova models - in contrast to the predictions of merging star ("mergeburst"…
All novae recur, but only a handful have been observed in eruption more than once. These systems, the recurrent novae (RNe), are among the most extreme examples of novae. RNe have long been thought of as potential type Ia supernova progenitors, and their claim to this 'accolade' has recently been strengthened. In this short review RNe will be presented within the framework of the maximum magnitude-rate of decline (MMRD) phase-space. Recent work integrating He-flashes into nova models, and the subsequent growth of the white dwarf, will be explored. This review also presents an overview of the G…
The development of a nova eruption is well known to be determined by the white dwarf (WD) mass and the rate at which it accretes mass from its donor. One of the advancements in this field is the understanding that the occurrence of a nova eruption depends on the presence of heavy elements in the envelope, and that the concentration of these elements is highly dependent on the time allotted for accretion. This results in many features of the eruption being correlated with the mass fractions of heavy elements in the ejected material, however, the accreted material is always assumed to be of sola…
A nova eruption irradiates and heats the donor star in a cataclysmic variable to high temperatures $T_{\rm irr}$, causing its outer layers to expand and overflow the Roche lobe. We calculate the donor's heating and expansion both analytically and numerically, under the assumption of spherical symmetry, and find that irradiation drives enhanced mass transfer from the donor at a rate $\dot{m}\propto T_{\rm irr}^{5/3}$, which reaches $\dot{m}\sim 10^{-6}\textrm{ M}_\odot\textrm{ yr}^{-1}$ at the peak of the eruption - about a thousand times faster than during quiescence. As the nova subsides and …
Fluctuations during a prolonged maximum have been observed in several nova eruptions, although it is not clear, and can not be deduced directly from observations, if the phenomenon is an actual physical reaction to some mechanism originating in the erupting white dwarf, if it is occurring in the expanding ejected shell or if it is a form of interaction with the red dwarf companion. A handful of erupting nova models are investigated in this work, in order to assess the possibility of this sort of feature being an actual part of the eruption itself. The results explain that the mechanism that ma…
For the ordinary classical nova QZ Aurigae (which erupted in 1964), we report 1317 magnitudes from 1912--2016, including four eclipses detected on archival photographic plates from long before the eruption. We have accurate and robust measures of the orbital period both pre-eruption and post-eruption, and we find that the orbital period decreased, with a fractional change of -290.71+-0.28 parts-per-million across the eruption, with the orbit necessarily getting smaller. Further, we find that the light curve outside of eclipses and eruption is flat at near B=17.14 from 1912--1981, whereupon the…
The old nova V728 Sco has been recently recovered via photometric and spectroscopic observations, 150 years after the nova eruption. The spectral properties pointed to a high-inclination system with a comparatively low mass-transfer rate. In this paper we show that the object is an eclipsing system with an orbital period of 3.32 h. It has enhanced long-term variability that can be interpreted as 'stunted' dwarf-nova-type outbursts. Using the ingress and egress times of the eclipsed components we calculate the radius of the central object. The latter turns out to be significantly larger than a …
I report two new measures of the sudden change in the orbital period ($P$) across the nova eruption ($Δ$P) and the steady period change in quiescence ($\dot{P}$) for classical novae (CNe) DQ Her and BT Mon. The fractional changes ($Δ$P/P) in parts-per-million (ppm) are $-$4.46$\pm$0.03 for DQ Her and +39.6$\pm$0.5 for BT Mon. For BT Mon, the $Δ$P/P value is not large enough (i.e., $>$1580 ppm) to allow for Hibernation in this system. The {\it negative} $Δ$P/P for DQ Her is a confident counterexample of the Hibernation model for the evolution of cataclysmic variables. Further, published models …
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 no…
We present a study on the evolution of the small scale velocity field in a solar filament as it approaches to the eruption. The observation was carried out by the Solar Dynamics Doppler Imager (SDDI) that was newly installed on the Solar Magnetic Activity Research Telescope (SMART) at Hida Observatory. The SDDI obtains a narrow-band full disk image of the sun at 73 channels from H$α$ - 9.0 Å to H$α$ + 9.0 Å, allowing us to study the line-of-sight (LOS) velocity of the filament before and during the eruption. The observed filament is a quiescent filament that erupted on 2016 November 5. We deri…
There have been several surprising developments in our understanding of symbiotic binary stars and nova eruptions over the last decade or so based on multiwavelength data. For example, symbiotic stars without shell burning on their white dwarfs have been revealed through their X-ray emission, UV excess, and UV variability. These purely accretion powered symbiotic stars have much weaker optical emission lines than those with shell burning, and are therefore harder to discover. Yet they may be as numerous as symbiotic stars with shell burning. Interestingly, both types of symbiotic stars are cap…
Cataclysmic variable stars (CVs) are close binary systems consisting of a white dwarf (primary) that is accreting matter from a low-mass companion star (secondary). From time to time such systems undergo large-amplitude brightenings. The most spectacular eruptions, over $10^4$ times in brightness, occur in classical novae and are caused by a thermonuclear runaway on the surface of the white dwarf. Such eruptions are thought to recur on timescales of $10^4-10^6$. In between, the system's properties depend primarily on the mass-transfer rate: if it is lower than a $10^{-9} M_{\odot}$/year, the a…
I report on two new measures of the sudden change in the orbital period ($P$) across the nova eruption ($Δ$P) and the steady period change in quiescence ($\dot{P}$) for classical novae (CNe) RR Pic and HR Del, bringing a total of six such measures for CNe, all in a final report of my large and long observing program. The fractional changes ($Δ$P/P) in parts-per-million (ppm) are -290.71$\pm$0.28 (QZ Aur), -472.1$\pm$4.8 (HR Del), -4.46$\pm$0.03 (DQ Her), +39.6$\pm$0.5 (BT Mon), -2003.7$\pm$0.9 (RR Pic), and -273$\pm$61 (V1017 Sgr). These results are in stark opposition to the Hibernation Model…
We are systematically surveying all known and suspected Z Cam-type dwarf novae for classical nova shells. This survey is motivated by the discovery of the largest known classical nova shell, which surrounds the archetypal dwarf nova Z Camelopardalis. The Z Cam shell demonstrates that at least some dwarf novae must have undergone classical nova eruptions in the past, and that at least some classical novae become dwarf novae long after their nova thermonuclear outbursts, in accord with the hibernation scenario of cataclysmic binaries. Here we report the detection of a fragmented "shell", 3 arcmi…
We present extensive datasets for a class of intermediate-luminosity optical transients known as "luminous red novae" (LRNe). They show double-peaked light curves, with an initial rapid luminosity rise to a blue peak (at -13 to -15 mag), which is followed by a longer-duration red peak that sometimes is attenuated, resembling a plateau. The progenitors of three of them (NGC4490-2011OT1, M101-2015OT1, and SNhunt248), likely relatively massive blue to yellow stars, were also observed in a pre-eruptive stage when their luminosity was slowly increasing. Early spectra obtained during the first peak …
We examine four high resolution reflection grating spectrometers (RGS) spectra of the February 2009 outburst of the luminous recurrent nova LMC 2009a. They were very complex and rich in intricate absorption and emission features. The continuum was consistent with a dominant component originating in the atmosphere of a shell burning white dwarf (WD) with peak effective temperature between 810,000 K and a million K, and mass in the 1.2-1.4 M$_\odot$ range. A moderate blue shift of the absorption features of a few hundred km s$^{-1}$ can be explained with a residual nova wind depleting the WD sur…
Using multi-wavelength observation from SDO and STEREO, we investigated the mechanism of two successive eruptions (F1 & F2) of a filament in active region NOAA 11444 on 27 march, 2012. The filament was inverse `J' shaped and lying along a quasi-circular polarity inversion line (PIL). The first part of the filament (F1) erupted at ~2:30UT on 27 March 2012, the second part of the filament (F2) erupted at around 4:20 UT on the same day. A precursor/pre-flare brightening was observed below filament's main axis about 30 min prior to F1. The brightening was followed by a jet-like ejection below fila…
We present an analysis of the red giant component of the recurrent nova V3890 Sgr, using data obtained before and after its 2019 eruption. Its effective temperature is $T_{\rm eff}=3050\pm$200 K for $\log{g}=0.7$, although there are modest changes in $T_{\rm eff}$. There is an overabundance of both carbon ($0.20\pm0.05$~dex) and sodium ($1.0\pm0.3$~dex) relative to their solar values, possibly the result of ejecta from the 1990 nova eruption being entrained into the red giant photosphere. We find $^{12}$C/$^{13}$C $=25\pm2$, a value similar to that found in red giants in other recurrent novae.…
The detection by Rest et al. (2012) of light echoes from $η$ Carinae has provided important new observational constraints on the nature of its 1840's era giant eruption. Spectra of the echoes suggest a relatively cool spectral temperature of about 5500K, lower than the lower limit of about 7000K suggested in the optically thick wind outflow analysis of Davidson (1987). This has lead to a debate about the viability of this steady wind model relative to alternative, explosive scenarios. Here we present an updated analysis of the wind outflow model using newer low-temperature opacity tabulations …
We present a series of near-infrared spectra of Nova Ophiuchus 2017 in the $K$ band that record the evolution of the first overtone CO emission in unprecedented detail. Starting from 11.7d after maximum, when CO is first detected at great strength, the spectra track the CO emission to +25.6d by which time it is found to have rapidly declined in strength by almost a factor of $\sim$ 35. The cause for the rapid destruction of CO is examined in the framework of different mechanisms for CO destruction viz. an increase in photoionizating flux, chemical pathways of destruction or destruction by ener…
