Nova Research Articles

CVN A Convolutional Visual Network for Identication and Reconstruction of NOvA Events

In the past year, the NOvA experiment released results for the observation of neutrino oscillations in the νμ and νe channels as well as νe cross section measurements using neutrinos from Fermilab’s NuMI beam. These and other measurements in progress rely on the accurate identication and reconstruction of the neutrino avor and energy recorded by our detectors. This presentation describes the rst application of convolutional neural network technology for event identication and reconstruction in particle detectors such as NOvA. The Convolutional Visual Network (CVN) Algorithm was developed for identication, categorization, and reconstruction of NOvA events. It increased the selection efficiency of the νe appearance signal by 40% and studies show potential impact to the νμ disappearance analysis.

Study of the Alm26(d,p)Al27 Reaction and the Influence of the Al26 0+ Isomer on the Destruction of Al26 in the Galaxy

The existence of ^{26}Al (t_{1/2}=7.17×10^{5} yr) in the interstellar medium provides a direct confirmation of ongoing nucleosynthesis in the Galaxy. The presence of a low-lying 0^{+} isomer (^{26}Al^{m}), however, severely complicates the astrophysical calculations. We present for the first time a study of the ^{26}Al^{m}(d,p)^{27}Al reaction using an isomeric ^{26}Al beam. The selectivity of this reaction allowed the study of ℓ=0 transfers to T=1/2, and T=3/2 states in ^{27}Al. Mirror symmetry arguments were then used to constrain the ^{26}Al^{m}(p,γ)^{27}Si reaction rate and provide an experimentally determined upper limit of the rate for the destruction of isomeric ^{26}Al via radiative proton capture reactions, which is expected to dominate the destruction path of ^{26}Al^{m} in asymptotic giant branch stars, classical novae, and core collapse supernovae.

Proper-motion age dating of the progeny of Nova Scorpii AD 1437.

'Cataclysmic variables' are binary star systems in which one star of the pair is a white dwarf, and which often generate bright and energetic stellar outbursts. Classical novae are one type of outburst: when the white dwarf accretes enough matter from its companion, the resulting hydrogen-rich atmospheric envelope can host a runaway thermonuclear reaction that generates a rapid brightening. Achieving peak luminosities of up to one million times that of the Sun, all classical novae are recurrent, on timescales of months to millennia. During the century before and after an eruption, the 'novalike' binary systems that give rise to classical novae exhibit high rates of mass transfer to their white dwarfs. Another type of outburst is the dwarf nova: these occur in binaries that have stellar masses and periods indistinguishable from those of novalikes but much lower mass-transfer rates, when accretion-disk instabilities drop matter onto the white dwarfs. The co-existence at the same orbital period of novalike binaries and dwarf novae-which are identical but for their widely varying accretion rates-has been a longstanding puzzle. Here we report the recovery of the binary star underlying the classical nova eruption of 11 March AD 1437 (refs 12, 13), and independently confirm its age by proper-motion dating. We show that, almost 500 years after a classical-nova event, the system exhibited dwarf-nova eruptions. The three other oldest recovered classical novae display nova shells, but lack firm post-eruption ages, and are also dwarf novae at present. We conclude that many old novae become dwarf novae for part of the millennia between successive nova eruptions.

Photometry of some more neglected bright cataclysmic variables and candidates

As part of an effort to better characterize bright cataclysmic variables (CVs) and related systems which have received little attention in the past light curves of four systems (V504 Cen, KT Eri, Ret 1 and CTCV 2056-3014) are analyzed. For some of these stars no time resolved photometry has been published previously. While flickering is observed in all systems except Ret 1, it is particularly strong in V504 Cen and CTCV 2056-3014. In the latter star, a previously observed 15.4 m period, leading to its tentative classification as an intermediate polar, is probably spurious. Variations on time scales of hundredths of days observed in the pre-outburst light curve of the classical nova KT Eri continue after the outburst but appear not to be strictly periodic. Furthermore, the long term post-outburst light curve exhibits modulations with quasi-periods of quite different length. Thus, these variations cannot be due to aspect related variations in a system with a giant component similar to some recurrent novae. Instead, the system possibly exhibits variations with a period of 0.1952 d which may be orbital. However, any such conclusion still requires confirmation. The absence of flickering in Ret 1 indicates that the system probably does not contain an accretion disk. Instead, the observation of slow variations supports a previous suspicion of low amplitude variability with a period >12 h.

Shock-powered light curves of luminous red novae as signatures of pre-dynamical mass-loss in stellar mergers

Luminous red novae (LRN) are a class of optical transients believed to originate from the mergers of binary stars, or "common envelope" events. Their light curves often show secondary maxima, which cannot be explained in the previous models of thermal energy diffusion or hydrogen recombination without invoking multiple independent shell ejections. We propose that double-peaked light curves are a natural consequence of a collision between dynamically-ejected fast shell and pre-existing equatorially-focused material, which was shed from the binary over many orbits preceding the dynamical event. The fast shell expands freely in the polar directions, powering the initial optical peak through cooling envelope emission. Radiative shocks from the collision in the equatorial plane power the secondary light curve peak on the radiative diffusion timescale of the deeper layers, similar to luminous Type IIn supernovae and some classical novae. Using a detailed 1D analytic model, informed by complementary 3D hydrodynamical simulations, we show that shock-powered emission can explain the observed range of peak timescales and luminosities of the secondary peaks in LRN for realistic variations in the binary parameters and fraction of the binary mass ejected. The dense shell created by the radiative shocks in the equatorial plane provides an ideal location for dust nucleation consistent with the the inferred aspherical geometry of dust in LRN. For giant stars, the ejecta forms dust when the shock-powered luminosity is still high, which could explain the infrared transients recently discovered by Spitzer. Our results suggest that pre-dynamical mass loss is common if not ubiquitous in stellar mergers, providing insight into the instabilities responsible for driving the binary merger.

Expanding Pharmacists' Scope of Practice to Include Immunization in Nova Scotia

On 10 December 2010 An Act to Amend Chapter 36 of the Acts of 2001, the Pharmacy Act (Bill 7) received Royal Assent in Nova Scotia, including an amendment that enabled an expanded scope of pharmacy practice. Expanding pharmacists' scope of practice came about from recommendations by various federal and provincial government bodies as an attempt to improve accessibility to health care and decrease costs. In 2013, pharmacists in Nova Scotia began administering the influenza vaccine as part of the publicly funded program in attempts to improve vaccine coverage rates. Preliminary evaluation in Nova Scotia has shown an increase in influenza vaccination coverage. Although pharmacist administration of influenza vaccination may improve vaccination coverage and reduce demand on physician time, there may be tension created among the professions, which needs to be addressed and managed. La modification des lois qui concernent les professions de sante reglementees , An Act to Amend Chapter 36 of the Acts of 2001, the Pharmacy Act (Loi 7), a ete sanctionee en Nouvelle-Ecosse le 10 Decembre, 2010. Un de ces changements legislatif avait pu renforcer l’elargissement du practique des pharmaciens en Nouvelle-Ecosse. Grâce a la conseil de plusieurs groupes gouvernementale, Federale et Provinciale, cette elargissement de practique essaient a diminuer le cout et ameliorer l’accessibilite du systeme de sante. En 2013, les pharmaciens en Nouvelle-Ecosse ont commence d’administrer le vaccin antigrippal gratuitement au public, pour augmenter le taux d’immunisation contre la grippe dans le province. Une evaluation preliminaire a demontre l’augmentation des taux d’immunisation en Nouvelle-Ecosse. Bien que l’administration du vaccin contre la grippe pourrait ameliorer la couvrage vaccinale et reduire le temps des medecins, il pourrait aussi cree des tensions entre les professions medicaux, qui doit etre addresser et gerer.

کانه زایی مس- نقره سولفید توده ای آتشفشان زاد نوع بشی در توالی آتشفشانی- رسوبی کرتاسه پسین: مثال موردی کانسار گرماب پایین، جنوب شرق شاهرود

کانسار مس- نقره گرماب پایین در توالی آتشفشانی- رسوبی کرتاسه پسین زیر پهنه سبزوار واقع ‌شده است. کانه زایی به شکل هندسی چینه‌سان و چینه‌کران در افق چینه‌ای خاص به همراه نهشته‌های برون‌دمی رخ‌داده است. سنگ میزبان کانه زایی را سنگ‌های آتشفشانی آندزیتی- داسیتی و آذرآواری‌های وابسته تشکیل می‌دهند. کانه زایی از کمرپایین به سمت کمربالا در چهار رخساره رگه- رگه‌چه ای، توده‌ای- نیمه توده‌ای، لایه‌ای و رسوبات برون‌دمی رخ‌داده است. کانی‌شناسی ماده معدنی شامل کانی‌های اولیه نظیر پیریت، مگنتیت و کالکوپیریت و کانی‌های ثانویه نظیر مس طبیعی، مالاکیت، کوپریت، کولیت و اکسیدهای آهن- منگنز است. دگرسانی سنگ دیواره، به‌طور عمده از نوع کلریتی و به مقدار کمتر شامل سیلیسی، آرژیلیتی و زئولیتی است. حداکثر عیار طلا و نقره در کانسار به ترتیب 1 و 19 گرم در تن است. به نظر می‌رسد که بروز فعالیت آتشفشانی زیردریایی در یک حوضه پشت‌کمانی در کرتاسه پسین، به تشکیل این کانسار سولفید توده‌ای نوع بشی منجر شده است.

No pre-maximum halt in classical nova V5589 Sgr observed with STEREO HI-1B

No pre-maximum halt in classical nova V5589 Sgr observed with STEREO HI-1B

Expanding Free School-based Human Papilloma Virus (HPV) Vaccination Programs to Include School-aged Males in Nova Scotia, Canada

Bill 70 ( HPV Vaccine Act ) was presented to the Nova Scotia House of Assembly with the aim of expanding the current Nova Scotia school-based HPV vaccination program to include males. In recent years, increased awareness of HPV and HPV-caused cancers has led to the implementation of school-based female HPV vaccination programs across Canada. Changing guidelines, based on recent evidence, suggest that males should also be included in these programs. Program expansion to include males aims to reduce the prevalence of HPV-causing cancers and their ensuing costs, to promote equal access to healthcare services, and to make Nova Scotia a leader in HPV prevention. Support from the Canadian public and high profile political actors along with pressure from other provinces and interest groups, including the Society of Obstetricians and Gynaecologists of Canada, influenced the passing of the HPV Vaccine Act . In order to implement this reform, the provincial financial commitment to the previous HPV program was expanded to cover the cost of male vaccination. Le projet de loi 70 (Loi sur les vaccins contre le papillomavirus) , dont l’objet est d’etendre aux garcons le programme de vaccination contre le papillomavirus humain (PVH) en vigueur actuellement dans les ecoles de Nouvelle Ecosse, a ete presente devant l’Assemblee parlementaire de la province. La prise de conscience recente du role du PVH comme facteur de risque dans de nombreux cancers a conduit a la mise en place de programmes de vaccination scolaires pour les filles partout au Canada. Des donnees empiriques recentes ont conduit a modifier les recommandations de pratiques pour ouvrir ces programmes aux garcons. L’objectif d’une telle ouverture des programmes est de diminuer la prevalence (et les couts) des cancers provoques par le PVH, ainsi que de renforcer l’egalite d’acces aux soins et de placer la Nouvelle Ecosse a la pointe de la prevention du PVH. Une opinion publique canadienne favorable, ainsi que le renfort d’acteurs politiques majeurs et la pression venue d’autres provinces et de groupes d’opinion, comme la Societe des Obstetriciens et Gynecologues du Canada, ont contribue au vote de la loi sur la vaccination PVH. La province a augmente son engagement financier dans le programme PVH afin de couvrir le cout des vaccins pour les garcons.

Accurate pre- and post-eruption orbital periods for the dwarf/classical nova V1017 Sgr

V1017 Sgr is a classical nova (in 1919) that displayed an earlier dwarf nova eruption (in 1901), and two more dwarf nova events (in 1973 and 1991). Previous work on this bright system in quiescence (V=13.5) has only been a few isolated magnitudes, a few spectra, and an ambiguous claim for an orbital period of 5.714 days as based on nine radial velocities. To test this period, we have collected 2896 magnitudes (plus 53 in the literature) in the UBVRIJHKL bands from 1897 to 2016, making an essentially complete photometric history of this unique cataclysmic variable. We find that the light curve in all bands is dominated by the ellipsoidal modulations of a G giant companion star, with a post-eruption (after the 1919 nova event) orbital period of 5.786290 +- 0.000032 days. This is the longest period for any classical nova, the accretion must be powered by the nuclear evolution of the companion star, and the dwarf nova events occur only because the outer parts of the large disk are cool enough to be unstable. Furthermore, we measure the pre-eruption orbital period (from 1907 to 1916), and there is a small steady period change in quiescence. The orbital period has decreased by 273 +- 61 parts-per-million across the 1919 eruption, with the significance of the period change being at the 5.7-sigma confidence level. This is startling and mystifying for nova-theory, because the three known period change effects cannot account for a period decrease in V1017 Sgr, much less one of such a large size.

Constraints on Oscillation Parameters from ν_{e} Appearance and ν_{μ} Disappearance in NOvA.

Results are reported from an improved measurement of ν_{μ}→ν_{e} transitions by the NOvA experiment. Using an exposure equivalent to 6.05×10^{20} protons on target, 33 ν_{e} candidates are observed with a background of 8.2±0.8 (syst.). Combined with the latest NOvA ν_{μ} disappearance data and external constraints from reactor experiments on sin^{2}2θ_{13}, the hypothesis of inverted mass hierarchy with θ_{23} in the lower octant is disfavored at greater than 93%C.L. for all values of δ_{CP}.

Hydrodynamic simulations of classical novae: Accretion onto CO white dwarfs as Sn Ia progenitors

Hydrodynamic simulations of classical novae: Accretion onto CO white dwarfs as Sn Ia progenitors

Nonmaximal θ_{23} Mixing at NOvA from Neutrino Decoherence.

In a study of a muon-neutrino disappearance at 810km, the NOvA experiment finds flavor mixing of the atmospheric sector to deviate from maximal (sin^{2}θ_{23}=0.5) by 2.6σ. The result is in tension with the 295-km baseline measurements of T2K, which are consistent with maximal mixing. We propose that θ_{23} is in fact maximal, and that the disagreement is a harbinger of environmentally induced decoherence. The departure from maximal mixing can be accounted for by an energy-independent decoherence of strength Γ=(2.3±1.1)×10^{-23} GeV.

Novae Contribution to the Galactic Lithium Enhancement

We use the Modules for Experiments in Stellar Astrophysics (MESA) code to calculate the yields of in the ejecta of classical novae, occurring on the surface of carbon-oxygen (CO) and oxygen-neon-magnesium (ONeMg) white dwarfs (WDs). Taking the masses and the mass accretion rates of WDs as input parameters, this article presents a grid showing the yield of from classical novae, including a total of 79 models. Under similar input parameters, the yields in our models are consistent with previous ones in the literature. yields recently inferred spectroscopically from classical nova V1369 Cen are then compared with the theoretical values obtained in this work. Using the grid as its basis and population synthesis as its method, this paper estimates the amount of produced by classical novae compared to the total in the Galaxy. Our simulations suggest that novae can eject about of every year. Hence, one may estimate that approximately 10% of in the Galaxy originates from classical novae, which is significantly higher than the produced by asymptotic giant branch stars.

A Radio Emission Analysis of Classical Nova V351 Pup (1991)

Abstract Previously, Nova Puppis 1991 (V351 Pup) was measured to host one of the most massive ejections claimed in the literature. Multi-frequency radio detections from one epoch were published for this nova in the 1990's; and yet, the remaining data collected by the Karl G. Jansky Very Large Array (VLA) have remained unpublished. In this paper, we analyze the remaining unpublished data sets for V351 Pup at frequencies of 4.9, 8.4, 14.9, and 22.5 GHz. We fit the resulting light curve to a model of expanding thermal ejecta, under the assumption that the radio emission is dominated by free–free radiation and accounting for high levels of clumping in the ejecta. Images of V351 Pup in both the radio (from the VLA) and Hα+[N ii] (from Hubble Space Telescope) exhibit no aspherical structure, strengthening our assumption of spherical symmetry. From expansion parallax methods, we estimate the distance to V351 Pup to be 5.0 ± 1.5 kpc. Our light-curve fit yields a value of for the ejecta mass, implying that V351 Pup is on the low end of expectations for ejecta mass from classical novae. A comparison between our derived ejecta mass and theoretical models gives evidence for a very massive (1.25 ) white dwarf, which is consistent with spectroscopic evidence for an oxygen–neon white dwarf.

Multi-epoch radio imaging of γ-ray Nova V959 Mon

V959 Mon (Nova Mon 2012) was first detected by the Fermi Large Area Telescope in June 2012, as a transient gamma-ray source. Subsequent optical observations showed that this gamma-ray emission was due to a classical nova explosion. Multi-frequency observations of V959 Mon with the VLA between June and September 2012 revealed dramatic brightening, and a spectrum that steepened with increasing frequency. High resolution radio images of V959 Mon using e-MERLIN are presented here, at six epochs between September 2012 and February 2014 which show morphological evolution of the source. While early e-MERLIN observations of V959 Mon show an east-west elonga- tion in the ejecta morphology, subsequent observations suggest that the ejecta become elongated in the north-south direction. Our high-resolution observations of this sur- prising evolution in the structure of V959 Mon can assist us in further understanding the behaviour and morphology of nova ejecta.

The supersoft X-ray source in V5116 Sagittarii

Classical novae occur on the surface of an accreting white dwarf in a binary system. After ejection of a fraction of the envelope and when the expanding shell becomes optically thin to X-rays, a bright source of supersoft X-rays arises, powered by residual H burning on the surface of the white dwarf. While the general picture of the nova event is well established, the details and balance of accretion and ejection processes in classical novae are still full of unknowns. The long-term balance of accreted matter is of special interest for massive accreting white dwarfs, which may be promising supernova Ia progenitor candidates. V5116 Sgr was observed as a bright and variable supersoft X-ray source by XMM-Newton 610~days after outburst. The light curve showed a periodicity consistent with the orbital period. During one third of the orbit the luminosity was a factor of seven brighter than during the other two thirds of the orbital period. In the present work we aim to disentangle the X-ray spectral components of V5116 Sgr and their variability. We present the high resolution spectra obtained with XMM-Newton RGS and Chandra LETGS/HRC-S in March and August 2007. The grating spectrum during the periods of high-flux shows a typical hot white dwarf atmosphere dominated by absorption lines of N VI and N VII. During the low-flux periods, the spectrum is dominated by an atmosphere with the same temperature as during the high-flux period, but with several emission features superimposed. Some of the emission lines are well modeled with an optically thin plasma in collisional equilibrium, rich in C and N, which also explains some excess in the spectra of the high-flux period. No velocity shifts are observed in the absorption lines, with an upper limit set by the spectral resolution of 500 km/s, consistent with the expectation of a non-expanding atmosphere so late in the evolution of the post-nova.

A Hubble Space Telescope Survey for Novae in M87. II. Snuffing out the Maximum Magnitude–Rate of Decline Relation for Novae as a Non-standard Candle, and a Prediction of the Existence of Ultrafast Novae*

Abstract The extensive grid of numerical simulations of nova eruptions from the work of Yaron et al. first predicted that some classical novae might significantly deviate from the Maximum Magnitude–Rate of Decline (MMRD) relation, which purports to characterize novae as standard candles. Kasliwal et al. have announced the observational detection of a new class of faint, fast classical novae in the Andromeda galaxy. These objects deviate strongly from the MMRD relationship, as predicted by Yaron et al. Recently, Shara et al. reported the first detections of faint, fast novae in M87. These previously overlooked objects are as common in the giant elliptical galaxy M87 as they are in the giant spiral M31; they comprise about 40% of all classical nova eruptions and greatly increase the observational scatter in the MMRD relation. We use the extensive grid of the nova simulations of Yaron et al. to identify the underlying causes of the existence of faint, fast novae. These are systems that have accreted, and can thus eject, only very low-mass envelopes, of the order of 10−7–10−8 M ⊙, on massive white dwarfs. Such binaries include, but are not limited to, the recurrent novae. These same models predict the existence of ultrafast novae that display decline times, t 2, to be as short as five hours. We outline a strategy for their future detection.

Shell-type supernova remnants as sources of cosmic rays

The investigation of VHE gamma-ray sources by any methods, including mirror Cherenkov telescopes, touches on the problem of the cosmic ray origin and, accordingly, the role of the Galaxy in their generation. The SHALON observations have yielded the results on Galactic supernova remnants (SNR) of different ages. Among them are: the shell-type SNRs Tycho’s SNR (1572y), Cas A (1680y), IC 443 (age∼(3–30)×103y), γCygni SNR (age∼(5–7)×103y), G166.0+4.3 (age∼24×103y) and classical nova GK Per (Nova 1901). For each of SNRs the observation results are presented with spectral energy distribution by SHALON in comparison with other experiment data and images by SHALON in together with data from X-ray by Chandra and radio-data by CGPS. The collected experimental data have confirmed the prediction of the theory about the hadronic generation mechanism of very high energy 800GeV–100TeV gamma-rays in Tycho’s SNR, Cas A and IC 443. For the first time, unique data on GK Per (Nova 1901) TeV gamma-ray emission were obtained with SHALON experiment. The X-ray data shows that, the nova remnant of GK Per could be a younger remnant that will resemble older SNRs like IC 443 which interact with molecular clouds. GK Per is supposed to be a candidate for TeV gamma-ray emission due to the accelerated particles in the reverse shock region.

Multimission observations of the old nova GK Per during the 2015 outburst

GK Per, a classical nova of 1901, is thought to undergo variable mass accretion on to a magnetized white dwarf (WD) in an intermediate polar system (IP). We organized a multi-mission observational campaign in the X-ray and ultraviolet (UV) energy ranges during its dwarf nova (DN) outburst in 2015 March-April. Comparing data from quiescence and near outburst, we have found that the maximum plasma temperature decreased from about 26 to 16.2+/-0.4 keV. This is consistent with the previously proposed scenario of increase in mass accretion rate while the inner radius of the magnetically disrupted accretion disc shrinks, thereby lowering the shock temperature. A NuSTAR observation also revealed a high-amplitude WD spin modulation of the very hard X-rays with a single-peaked profile, suggesting an obscuration of the lower accretion pole and an extended shock region on the WD surface. The X-ray spectrum of GK Per measured with the Swift X-Ray Telescope varied on time-scales of days and also showed a gradual increase of the soft X-ray flux below 2 keV, accompanied by a decrease of the hard flux above 2 keV. In the Chandra observation with the High Energy Transmission Gratings, we detected prominent emission lines, especially of Ne, Mg and Si, where the ratios of H-like to He-like transition for each element indicate a much lower temperature than the underlying continuum. We suggest that the X-ray emission in the 0.8-2 keV range originates from the magnetospheric boundary.