Phases Of Stellar Evolution Research Articles

Post-main-sequence debris from rotation-induced YORP break-up of small bodies

Although discs of dust and gas have been observed orbiting white dwarfs, the origin of this circumstellar matter is uncertain. We hypothesize that the in-situ breakup of small bodies such as asteroids spun to fission during the giant branch phases of stellar evolution provides an important contribution to this debris. The YORP effect, which arises from radiation pressure, accelerates the spin rate of asymmetric asteroids, which can eventually shear themselves apart. This pressure is maintained and enhanced around dying stars because the outward push of an asteroid due to stellar mass loss is insignificant compared to the resulting stellar luminosity increase. Consequently, giant star radiation will destroy nearly all bodies with radii in the range 100 m - 10 km that survive their parent star's main sequence lifetime within a distance of about 7 au; smaller bodies are spun apart to their strongest, competent components. This estimate is conservative, and would increase for highly asymmetric shapes or incorporation of the inward drag due to giant star stellar wind. The resulting debris field, which could extend to thousands of au, may be perturbed by remnant planetary systems to reproduce the observed dusty and gaseous discs which accompany polluted white dwarfs.

MASER AND INFRARED STUDIES OF OXYGEN-RICH LATE/POST-ASYMPTOTIC GIANT BRANCH STARS AND WATER FOUNTAINS: DEVELOPMENT OF A NEW IDENTIFICATION METHOD

We explored an efficient method to identify evolved stars with oxygen-rich envelopes in the late AGB or post-AGB phase of stellar evolution, which include a rare class of objects - the "water fountains". Our method considers the OH and H2O maser spectra, the near infrared Q-parameters (these are colour indices accounting for the effect of extinction), and far-infrared AKARI colours. Here we first present the results of a new survey on OH and H2O masers. There were 108 colour-selected objects: 53 of them were observed in the three OH maser lines (1612, 1665, and 1667 MHz), with 24 detections (16 new for 1612 MHz); and 106 of them were observed in the H2O maser line (22 GHz) with 24 detections (12 new). We identify a new potential water fountain source, IRAS19356+0754, with large velocity coverages of both OH and H2O maser emission. In addition, several objects with high velocity OH maser emission are reported for the first time. The Q-parameters as well as the infrared [09]-[18] and [18]-[65] AKARI colours of the surveyed objects are then calculated. We suggest that these infrared properties are effective in isolating aspherical from spherical objects, but the morphology may not necessarily be related to the evolutionary status. Nonetheless, by considering altogether the maser and infrared properties, the efficiency of identifying oxygen-rich late/post-AGB stars could be improved.

A K-band spectral mini-survey of Galactic B[e] stars★

We present a mini-survey of Galactic B[e] stars mainly undertaken with the Large Binocular Telescope (LBT). B[e] stars show morphological features with hydrogen emission lines and an infrared excess, attributed to warm circumstellar dust. In general, these features are assumed to arise from dense, non-spherical, disk-forming circumstellar material in which molecules and dust can condensate. Due to the lack of reliable luminosities, the class of Galactic B[e] stars contains stars at very different stellar evolutionary phases like Herbig AeBe, supergiants or planetary nebulae. We took near-infrared long-slit K-band spectra for a sample of Galactic B[e] stars with the LBT-Luci I. Prominent spectral features, such as the Brackett gamma line and CO band heads are identified in the spectra. The analysis shows that the stars can be characterized as evolved objects. Among others we find one LBV candidate (MWC314), one supergiant B[e] candidate with 13CO (MWC137) and in two cases (MWC623 and AS 381) indications for the existence of a late-type binary companion, complementary to previous studies. For MWC84, IR spectra were taken at different epochs with LBT-Luci I and the GNIRS spectrograph at the Gemini North telescope. The new data show the disappearance of the circumstellar CO emission around this star, previously detectable over decades. Also no signs of a recent prominent eruption leading to the formation of new CO disk emission are found during 2010 and 2013.

Late stages of stellar evolution in population models

AbstractMy contribution to Roger's celebration symposium focuses on the treatment of late stellar evolutionary phases in stellar population models, reviewing the state of art and discussing some very recent developments, ranging from local stellar clusters up to distant galaxies at high redshift. I shall focus in particular on the Thermally Pulsating Asymptotic Giant Branch, about which a vivid discussion has been ongoing since a few years. I shall present renewed evidence in favour of a sizable contribution from this phase for matching the observed spectral energy distribution of distant massive galaxies. I shall also discuss the possible reasons why such a conclusion has been controversial in the recent literature. Stellar population models are the magic tool to shape the physics of galaxies out of their observed light, and enter virtually all papers presented at this symposium. In a collective effort to properly treat all relevant aspects of the modelling, we split the discussion into six contributions given by experts in the field, as our present to Roger and his outstanding career.

Constraints on stellar evolution from white dwarf asteroseismology

AbstractHigh mass and low mass stars follow a similar evolution until the inert core phase that follows the end of the core helium burning stage. In particular, one common phase of stellar evolution is the alpha capture reaction that turns carbon into oxygen in the core. We can obtain constraints on this reaction rate by studying the remnants of low mass stars, as this is the ultimate reaction that occurs in their core. We also present results that allow us to test the time dependent calculations of diffusion in dense interiors.

Impact of rotation on the geometrical configurations of fossil magnetic fields

AbstractThe MiMeS project demonstrated that a small fraction of massive stars (around 7%) presents large-scale, stable, generally dipolar magnetic fields at their surface. These fields that do not present any evident correlations with stellar mass or rotation are supposed to be fossil remnants of the initial phases of stellar evolution. They result from the relaxation to MHD equilibrium states, during the formation of stable radiation zones, of initial fields resulting from a previous convective phase. In this work, we present new theoretical results, where we generalize previous studies by taking rotation into account. The properties of relaxed fossil fields are compared to those obtained when rotation is ignored. Consequences for magnetic fields in the radiative envelope of rotating early-type stars and their stability are finally discussed.

A PARTICLE DARK MATTER FOOTPRINT ON THE FIRST GENERATION OF STARS

Dark matter particles with properties identical to dark matter candidates that are hinted at by several international collaborations dedicated to experimental detection of dark matter (DAMA, COGENT, CRESST and CDMS-II, although not, most notably, by LUX), and which also have a dark matter asymmetry identical to the observed baryon asymmetry (Planck and Wilkinson Microwave Anisotropy Probe), may produce a significant impact on the evolution of the first generation of low-metallicity stars. The lifetimes of these stars in different phases of stellar evolution are significantly extended, namely, in the pre-main sequence, main sequence, and red giant phases. In particular, intermediate-mass stars in the red giant phase experience significant changes in their luminosity and chemical composition. The annihilations of dark matter particles affect the interior of the star in such a way that the $3\alpha-$reaction becomes less efficient in the production of carbon and oxygen. This dark matter effect contradicts the excess of carbon and other metals observed today in stars of low mass and low metallicity. Hence, we can impose an upper limit on the dark matter halo density, and therefore on the redshift, at which the first generation of low-metallicity stars formed.

NEW DETERMINATION OF THE2H(d,p)3H AND2H(d,n)3He REACTION RATES AT ASTROPHYSICAL ENERGIES

The cross sections of the 2H(d,p)3H and 2H(d,n)3He reactions have been measured via the Trojan Horse method applied to the quasi-free 2H(3He,p 3H)1H and 2H(3He,n 3He)1H processes at 18 MeV off the proton in 3He. For the first time, the bare nucleus S(E) factors have been determined from 1.5 MeV, across the relevant region for standard Big Bang nucleosynthesis, down to the thermal energies of deuterium burning in the pre-main-sequence (PMS) phase of stellar evolution, as well as of future fusion reactors. Both the energy dependence and the absolute value of the S(E) factors deviate by more than 15% from the available direct data and existing fitting curves, with substantial variations in the electron screening by more than 50%. As a consequence, the reaction rates for astrophysics experience relevant changes, with a maximum increase of up to 20% at the temperatures of the PMS phase. From a recent primordial abundance sensitivity study, it turns out that the 2H(d,n)3He reaction is quite influential on 7Li, and the present change in the reaction rate leads to a decrease in its abundance by up to 10%. The present reaction rates have also been included in an updated version of the FRANEC evolutionary code to analyze their influence on the central deuterium abundance in PMS stars with different masses. The largest variation of about 10%-15% pertains to young stars (≤1 Myr) with masses ≥1 M ☉.

THE CORE MASS GROWTH AND STELLAR LIFETIME OF THERMALLY PULSING ASYMPTOTIC GIANT BRANCH STARS

We establish new constraints on the intermediate-mass range of the initial-final mass relation by studying white dwarfs in four young star clusters, and apply the results to study the evolution of stars on the thermally pulsing asymptotic giant branch (TP-AGB). We show that the stellar core mass on the AGB grows rapidly from 10% to 30% for stars with $M_{\rm initial}$ = 1.6 to 2.0 $M_\odot$. At larger masses, the core-mass growth decreases steadily to $\sim$10% at $M_{\rm initial}$ = 3.4 $M_\odot$. These observations are in excellent agreement with predictions from the latest TP-AGB evolutionary models in Marigo et al. (2013). We also compare to models with varying efficiencies of the third dredge-up and mass loss, and demonstrate that the process governing the growth of the core is largely the stellar wind, while the third dredge-up plays a secondary, but non-negligible role. Based on the new white dwarf measurements, we perform an exploratory calibration of the most popular mass-loss prescriptions in the literature. Finally, we estimate the lifetime and the integrated luminosity of stars on the TP-AGB to peak at $t$ $\sim$ 3 Myr and $E$ = 1.2 $\times$ 10$^{10}$ $L_\odot$ yr for $M_{\rm initial}$ $\sim$ 2 $M_\odot$ ($t$ $\sim$ 2 Myr for luminosities brighter than the RGB tip at $\log(L/L_{\odot})$ $>$ 3.4), decreasing to $t$ = 0.4 Myr and $E$ = 6.1 $\times$ 10$^{9}$ $L_\odot$ yr for stars with $M_{\rm initial}$ $\sim$ 3.5 $M_\odot$. The implications of these results are discussed with respect to general population synthesis studies that require correct modeling of the TP-AGB phase of stellar evolution.

An exoplanet's response to anisotropic stellar mass loss during birth and death

The birth and death of planets may be affected by mass outflows from their parent stars during the T-Tauri or post-main-sequence phases of stellar evolution. These outflows are often modelled to be isotropic, but this assumption is not realistic for fast rotators, bipolar jets and supernovae. Here we derive the general equations of motion for the time evolution of a single planet, brown dwarf, comet or asteroid perturbed by anisotropic mass loss in terms of a complete set of planetary orbital elements, the ejecta velocity, and the parent star's co-latitude and longitude. We restrict our application of these equations to 1) rapidly rotating giant stars, and 2) arbitrarily-directed jet outflows. We conclude that the isotropic mass-loss assumption can safely be used to model planetary motion during giant branch phases of stellar evolution within distances of hundreds of au. In fact, latitudinal mass loss variations anisotropically affect planetary motion only if the mass loss is asymmetric about the stellar equator. Also, we demonstrate how constant-velocity, asymmetric bipolar outflows in young systems incite orbital inclination changes. Consequently, this phenomenon readily tilts exoplanetary orbits external to a nascent disc on the order of degrees.

The star forming region Monoceros R2 as a gamma-ray source

Context. After the release of the gamma-ray source catalog produced by the Fermi satellite during its first two years of operation, a significant fraction of sources still remain unassociated at lower energies. In addition to well-known high-energy emitters (pulsars, blazars, supernova remnants, etc.) theoretical expectations predict new classes of gamma-ray sources. In particular, gamma-ray emission could be associated with some of the early phases of stellar evolution, but this interesting possibility is still poorly understood. Aims. The aim of this paper is to assess the possibility of the Fermi gamma-ray source 2FGL J0607.5-0618c being associated with the massive star forming region Monoceros R2. Methods. A multi-wavelength analysis of the Monoceros R2 region is carried out using archival data at radio, infrared, X-ray, and gamma-ray wavelengths. The resulting observational properties are used to estimate the physical parameters needed to test the different physical scenarios. Results. We confirm the 2FGL J0607.5-0618c detection with improved confidence over the Fermi two-year catalog. We find that a combined effect of the multiple young stellar objects in Monoceros R2 is a viable picture for the nature of the source.

Simulations of two-planet systems through all phases of stellar evolution: implications for the instability boundary and white dwarf pollution

Exoplanets have been observed at many stages of their host star's life, including the main sequence (MS), subgiant and red giant branch stages. Also, polluted white dwarfs (WDs) likely represent dynamically active systems at late times. Here, we perform 3-body simulations which include realistic post-MS stellar mass loss and span the entire lifetime of exosystems with two massive planets, from the endpoint of formation to several Gyr into the WD phase of the host star. We find that both MS and WD systems experience ejections and star-planet collisions (Lagrange instability) even if the planet-planet separation well-exceeds the analytical orbit-crossing (Hill instability) boundary. Consequently, MS-stable planets do not need to be closely-packed to experience instability during the WD phase. This instability may pollute the WD directly through collisions, or, more likely, indirectly through increased scattering of smaller bodies such as asteroids or comets. Our simulations show that this instability occurs predominately between tens of Myr to a few Gyrs of WD cooling.

The internal structure of neutron stars and white dwarfs, and the Jacobi virial equation. II.

In a previous paper we have shown that the function \Gamma(M, EOS)=\alpha\beta_{GR}/\Lambda^{0.9}(R) is constant (~ 0.4) for pre main-sequence stars (PMS), white dwarfs (WD) and for some neutron star (NS) models, where \alpha_{GR} and \beta_{GR} are the form-factors of the gravitational potential energy and of the moment of inertia. To investigate the structural evolution of another type of celestial bodies, we use the MESA code to extend these calculations to gaseous planets. We show that this function is conserved for all models during the whole planetary evolution and is independent of the planet mass. We also analyse the cases for which this function is not conserved during some stellar evolutionary phases. For the PMS to the WD cooling sequences, we have found a connection between the strong variations of \Gamma(M, EOS) during the intermediary evolutionary phases and the specific nuclear power. A threshold for the specific nuclear power was determined. Below this limit this function is invariant (~ 0.4) for these models, i.e., at the initial and final stages (PMS and WD). Concerning NS, we study the influence of the equation of state (EOS) on this function and refine the exponent of the auxiliary function \Lambda(R) to be ~ 0.8. It is shown that the function \Gamma(M, EOS) is also invariant (~ 0.4) and is independent of the EOS and of the stellar mass. Therefore, we confirm that regardless of the final products of the stellar evolution, NS or WD, they recover the initial value of \Gamma(M, EOS) ~ 0.4 acquired at the PMS. Finally, we have introduced a macroscopic stability "criterion" for neutron star models based on the properties of the relativistic product \alpha\beta_{GR}.

Fine-grid calculations for stellar electron and positron capture rates on Fe isotopes

The acquisition of precise and reliable nuclear data is a prerequisite to success for stellar evolution and nucleosynthesis studies. Core-collapse simulators find it challenging to generate an explosion from the collapse of the core of massive stars. It is believed that a better understanding of the microphysics of core-collapse can lead to successful results. The weak interaction processes are able to trigger the collapse and control the lepton-to-baryon ratio (Y e ) of the corematerial. It is suggested that the temporal variation of Y e within the core of a massive star has a pivotal role to play in the stellar evolution and a fine-tuning of this parameter at various stages of presupernova evolution is the key to generate an explosion. During the presupernova evolution of massive stars, isotopes of iron, mainly 54–56Fe, are considered to be key players in controlling Y e ratio via electron capture on these nuclides. Recently an improved microscopic calculation of weak-interaction-mediated rates for iron isotopes was introduced using the proton-neutron quasiparticle random-phase-approximation (pn-QRPA) theory. The pn-QRPA theory allows a microscopic state-by-state calculation of stellar capture rates which greatly increases the reliability of calculated rates. The results were suggestive of some fine-tuning of the Y e ratio during various phases of stellar evolution. Here we present for the first time the fine-grid calculation of the electron and positron capture rates on 54–56Fe. The sensitivity of the pn-QRPA calculated capture rates to the deformation parameter is also studied in this work. Core-collapse simulators may find this calculation suitable for interpolation purposes and for necessary incorporation in the stellar evolution codes.

A Bayesian approach to scaling relations for amplitudes of solar-like oscillations in Kepler stars

We investigate different amplitude scaling relations adopted for the asteroseismology of stars that show solar-like oscillations. Amplitudes are among the most challenging asteroseismic quantities to handle because of the large uncertainties that arise in measuring the background level in the star's power spectrum. We present results computed by means of a Bayesian inference on a sample of 1640 stars observed with Kepler, spanning from main sequence to red giant stars, for 12 models used for amplitude predictions and exploiting recently well-calibrated effective temperatures from SDSS photometry. We test the candidate amplitude scaling relations by means of a Bayesian model comparison. We find the model having a separate dependence upon the mass of the stars to be largely the most favored one. The differences among models and the differences seen in their free parameters from early to late phases of stellar evolution are also highlighted.

Angular momentum evolution of low‐mass pre‐main sequence stars via extreme coronal mass ejections

AbstractThe angular momentum evolution of cool stars during the pre‐main sequence phase of stellar evolution remains a major outstanding problem. Multiple processes are likely involved in the transfer of mass and angular momentum within and out of the star+disk system. The role of coronal mass ejections (CMEs), energetic events which shed mass and magnetic flux in the Sun, has yet to be fully explored in the context of pre‐main sequence stars. It is well established that young, solar‐type stars exhibit X‐ray activity levels up to four orders of magnitude higher than the present‐day Sun, suggesting that CMEs associated with these extreme X‐ray flares could be an important process for expelling mass and angular momentum. We present a novel approach to modeling the CMEs of low‐mass pre‐main sequence stars that uses a solar‐calibrated CME model and observed X‐ray flare rates for young stars. We derive mass loss rates via stellar CMEs and calculate their attendant angular momentum losses during the pre‐main sequence phase. While we find the mass loss rates to be modest, ∼10 % of steady‐state stellar wind values from the literature, the angular momentum losses can be substantial, potentially counteracting the effects of initial stellar spin‐up due to contraction in tens of Myr. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Tidally induced oscillations and orbital decay in compact triple-star systems

We investigate the nature of tidal effects in compact triple-star systems. The hierarchical structure of a triple system produces tidal forcing at high frequencies unobtainable in binary systems, allowing for the tidal excitation of high frequency p-modes in the stellar components. The tidal forcing exists even for circular, aligned, and synchronized systems. We calculate the magnitude and frequencies of three-body tidal forcing on the central primary star for circular and coplanar orbits, and we estimate the amplitude of the tidally excited oscillation modes. We also calculate the secular orbital changes induced by the tidally excited modes, and show that they can cause significant orbital decay. During certain phases of stellar evolution, the tidal dissipation may be greatly enhanced by resonance locking. We then compare our theory to observations of HD 181068, which is a hierarchical triply eclipsing star system in the Kepler field of view. The observed oscillation frequencies in HD 181068 can be naturally explained by three-body tidal effects. We then compare the observed oscillation amplitudes and phases in HD 181068 to our predictions, finding mostly good agreement. Finally, we discuss the past and future evolution of compact triple systems like HD 181068.

Combining computer models to account for mass loss in stellar evolution

AbstractIntricate computer models can be used to describe complex physical processes in astronomy such as the evolution of stars. Like a sampling distribution, these models typically predict observed quantities as a function of a number of unknown parameters. Including them as components of a statistical model, however, leads to significant modeling, inferential, and computational challenges. In this article, we tackle these challenges in the study of the mass loss that stars experience as they age. We have developed a new Bayesian technique for inferring the so‐called initial–final mass relation (IFMR), the relationship between the initial mass of a Sun‐like star and its final mass as a white dwarf. Our model incorporates several separate computer models for various phases of stellar evolution. We bridge these computer models with a parameterized IFMR in order to embed them into a statistical model. This strategy allows us to apply the full force of powerful statistical tools to build, fit, check, and improve the statistical models and their computer model components. In contrast to traditional techniques for inferring the IFMR, which tend to be quite ad hoc, we can estimate the uncertainty in our fit and ensure that our model components are internally coherent. We analyze data from three star clusters: NGC 2477, the Hyades, and M35 (NGC 2168). The results from NGC 2477 and M35 suggest different conclusions about the IFMR in the mid‐ to high‐mass range, raising questions for further astronomical work. We also compare the results from two different models for the primary hydrogen‐burning stage of stellar evolution. We show through simulations that misspecification at this stage of modeling can sometimes have a severe effect on inferred white dwarf masses. Nonetheless, when working with observed data, our inferences are not particularly sensitive to the choice of model for this stage of evolution. © 2013 Wiley Periodicals, Inc. Statistical Analysis and Data Mining 6: 34–52, 2013

Stellar neutron capture rates – key data for thesprocess

Neutron reactions are responsible for the formation of the elements heavier than iron. The corresponding scenarios relate to the He- and C- burning phases of stellar evolution (s process) and to supernova explosions (r and p processes). The s process, which is characterized by low neutron densities, operates in or near the valley of β stability and has produced about half of the elemental abundances between Fe and Bi in the solar system and in the Universe. Because the s abundances are essentially determined by the (n, γ ) cross sections along the reaction path, accurate neutron data constitute the key input for s process studies. Important constraints for the physical conditions at the stellar sites can be inferred by comparison of the abundance patterns from current s -process models with solar system material or presolar grains. The experimental methods for the determination of stellar (n, γ ) rates are outlined at the example of recent cross section measurements and remaining quests will be discussed with respect to existing laboratory neutron sources and new developments.

Measurement ofγrays from15N(p,γ)16O cascade and15N(p,α1γ)12C reactions

Background The main energy production mechanism for massive stars during hydrogen burning is the CNO cycle. The reactions ${}^{15}$N${(p,\phantom{\rule{-0.16em}{0ex}}\ensuremath{\gamma})}^{16}$O and ${}^{15}$N${(p,\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\alpha}}_{0})}^{12}$C form a branch point in this cycle. The ratio of the corresponding reaction rates determines the CNO abundances evolving during this early stage of the star's life which affects the subsequent nucleosynthesis in later phases of stellar evolution. Determining the cross sections for these reactions at stellar energies is often very difficult. Measurements of other reactions that populate the same compound nucleus can often be used to indirectly determine the cross section of interest.Purpose The nuclear level properties of broad resonances in ${}^{16}$O which characterize the cross section of the reactions ${}^{15}$N${(p,\phantom{\rule{-0.16em}{0ex}}\ensuremath{\gamma})}^{16}$O and ${}^{15}$N${(p,\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\alpha}}_{0})}^{12}$C must be well known in order to accurately extrapolate the measured cross sections to the stellar energy range. The $R$-matrix formalism is a powerful technique for interpreting these cross sections and is greatly enhanced by additional data in other reaction channels. In a previous publication, measurements were reported for the cross section of the reaction ${}^{15}$N${(p,\phantom{\rule{-0.16em}{0ex}}\ensuremath{\gamma})}^{16}$O for the ground state transition only. Concurrently, $\ensuremath{\gamma}$-ray measurements were recorded for the cascade transitions to the ${E}_{x}$ $=$ 6.050, 6.130, and 7.117 MeV bound states of ${}^{16}$O as well as from the reaction ${}^{15}$N${(p,\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\alpha}}_{1}\ensuremath{\gamma})}^{12}$C. Excitation curves for the cascade transitions have never been measured and the excitation curve data for the ${}^{15}$N${(p,\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\alpha}}_{1}\ensuremath{\gamma})}^{12}$C reaction found in the literature may suffer from substantial errors due to target contamination.Methods Angle integrated cross sections are measured over the proton energy range from ${E}_{p}$ $=$ 0.14 to 1.80 MeV for the $\ensuremath{\gamma}$-ray cascade transitions and for the reaction ${}^{15}$N${(p,\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\alpha}}_{1}\ensuremath{\gamma})}^{12}$C.Results De-excitations associated with several compound nucleus states in ${}^{16}$O are observed in both the $\ensuremath{\gamma}$-ray and ${\ensuremath{\alpha}}_{1}$ channels. An $R$-matrix analysis is performed and partial decay widths are deduced for several previously unobserved decay branchings from these states.Conclusion For the first time, excitation curves for the cascade transitions to the ${}^{16}$O bound states at ${E}_{x}$ $=$ 6.050, 6.130, and 7.117 MeV are reported over the energy range from ${E}_{p}$ $=$ 0.14 to 1.80 MeV. In addition, an improved measurement of the ${}^{15}$N${(p,\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\alpha}}_{1}\ensuremath{\gamma})}^{12}$C excitation curve has been made over a similar energy range.