Arcturus Research Articles

Bioboard

The following topics are under this section: ASIA-PACIFIC — Identification of Therapeutic Points for Genetically Diverse and Fatal Leukaemia ASIA-PACIFIC — Novel Microfluidic Processes for Drug Development ASIA-PACIFIC — Development of Anti-Microbial Coating against COVID-19 ASIA-PACIFIC — Partnership between Arcturus Therapeutics and Duke-NUS Medical School to develop COVID-19 Vaccine ASIA-PACIFIC — Nanoscopic Insights to Proteins against Huntington’s Disease ASIA-PACIFIC — Unravelling the Impact of Marine Heatwave on Coral Reef Fishes ASIA-PACIFIC — Regulation of Plant Pores by MicroRNAs ASIA-PACIFIC — Discovering Clues to Longevity in Our Genome ASIA-PACIFIC — Repurposing Nature’s Products to Viable Materials ASIA-PACIFIC — Reverse Conversion of Oestrogens to Androgens REST OF THE WORLD — HER2-targeted Antibody Drug Conjugate Shows Promise in Patients with Non-Breast-Gastric Cancers REST OF THE WORLD — New Research finds Teeth as a Biological Archive REST OF THE WORLD — Finding Treatment for Muscular Dystrophy using CRISPR

More Astronomy in Ovid’s Daedalus and Icarus

This essay presents a cosmographic analysis of Ovid’s mythology in both Ars am. 2.21–96 and Met. 8.174–235. Daedalus’ flying instruction me duce carpe viam! at 8.208 = Ars am. 2.57–58 appears to deal with the in-tandem Morning Rising of Daedalus alias the single star Protrygeter/Vindemitor and Icarus alias the single star Arcturus, which heralds the grape harvest in September. Icarus is not supposed to impersonate his namesake Icarus pater Erigones, the pioneer winegrower from Attica who was catasterized into the constellation Boötes. Nevertheless the aviator imitates the winegrower’s Evening Setting = Boötes’ συγκατάδυσις (with συν-= “together with the Sun/ vicino sole/ Deo propiore” at Ars am. 2.59–60 and 85), thus causing the wax to liquescere/molliri/φάεος κορέσασθαι at Met. 8.225–226 in the season when ἠελίοιο κατερχομένοιο δύηται <Βοώτης> (Aratus, Phaen. 582–585).

Quae istaec fabulast? V iskanju komedije v Plavtovi Vrvi

Članek obravnava Plavtovo komedijo Rudens; izhaja iz prologa, ki v komedijo z izpostavljanjem izrazito rimskih pojmov pietas in fides vnaša resnoben didaktično-moralizirajoč ton; posveča se analizi omenjenih pojmov, pri tem pa se dotika vprašanj, ki zadevajo komično konvencijo in komedijo kot dramsko zvrst nasploh.

HYPERFINE-DEPENDENT gf -VALUES OF Mn I LINES IN THE 1.49-1.80 μm H BAND

The three Mn I lines at 17325, 17339 and 17349 \AA~are among the 25 strongest lines ($\log(gf)>0.5$) in the H-band. They are all heavily broadened due to hyperfine structure and the profiles of these lines have so far not been understood. Earlier studies of these lines even suggested that they were blended. In this work, the profiles of these three infra-red (IR) lines have been studied theoretically and compared to experimental spectra to assist in the complete understanding of the solar spectrum in the IR. It is shown that the structure of these lines can not be described in the conventional way by the diagonal $A$ and $B$ hyperfine interaction constants. The off-diagonal hyperfine interaction not only has large impact on the energies of the hyperfine levels, but also introduces a large intensity redistribution among the hyperfine lines, changing the line profiles dramatically. By performing large-scale calculations of the diagonal and off-diagonal hyperfine interaction and $gf$-values between the upper and lower hyperfine levels and using a semi-empirical fitting procedure, agreement between our synthetic and experimental spectra was achieved. Furthermore, we compare our results with observations of stellar spectra. The spectra of the Sun and the K1.5 III red giant star Arcturus were modelled in the relevant region, $1.73-1.74$ $\mu$m using our theoretically predicted $gf$-values and energies for each individual hyperfine line. Satisfactory fits were obtained and clear improvements were found using our new data compared with the old available Mn I data. A complete list of energies and $gf$-values for all the $3d^54s({^7S})4d$ e$^{6}$D $-$ $3d^54s({^7S})4f$ w$^{6}$F hyperfine lines are available as supplementary material online, whereas only the stronger lines are presented and discussed in detail in this paper.

MULTI-WAVELENGTH RADIO CONTINUUM EMISSION STUDIES OF DUST-FREE RED GIANTS

Multi-wavelength centimeter continuum observations of non-dusty, non-pulsating K spectral-type red giants directly sample their chromospheres and wind acceleration zones. Such stars are feeble emitters at these wavelengths however, and previous observations have provided only a small number of modest S/N measurements slowly accumulated over three decades. We present multi-wavelength Karl G. Jansky Very Large Array thermal continuum observations of the wind acceleration zones of two dust-free red giants, Arcturus (Alpha Boo: K2 III) and Aldebaran (Alpha Tau: K5 III). Importantly, most of our observations of each star were carried out over just a few days, so that we obtained a snapshot of the different stellar atmospheric layers sampled at different wavelengths, independent of any long-term variability. We report the first detections at several wavelengths for each star including a detection at 10 cm (3.0 GHz: S band) for both stars and a 20 cm (1.5 GHz: L band) detection for Alpha Boo. This is the first time single luminosity class III red giants have been detected at these continuum wavelengths. Our long-wavelength data sample the outer layers of Alpha Boo's atmosphere where its wind velocity is approaching its terminal value and the ionization balance is becoming frozen-in. For Alpha Tau, however, our long-wavelength data are still sampling its inner atmosphere, where the wind is still accelerating probably due to its lower mass-loss rate. We compare our data with published semi-empirical models based on ultraviolet data, and the marked deviations highlight the need for new atmospheric models to be developed. Spectral indices are used to discuss the possible properties of the stellar atmospheres, and we find evidence for a rapidly cooling wind in the case of Alpha Boo. Finally, we develop a simple analytical wind model for Alpha Boo based on our new long-wavelength flux measurements.

Temperature stratification of the atmosphere of Arcturus

A brief overview of the results of the investigations of the red giant star Arcturus is given. One-dimensional LTE modeling of the atmospheres of Arcturus and the Sun as a star is carried out on the basis of synthesis of the extended wings of the H and K Ca II lines. It is found that the local continuum in this spectral region is underestimated by an average of 12% in the atlases of Arcturus. The average deficit in UV absorption amounts to 43% for Arcturus whereas it is 9% for the Sun. For Arcturus the correction factor to the continuum opacity at the wavelengths of 390.0, 392.5, 395.0, 398.0, and 400.0 nm equals 2.20, 1.90, 1.70, 1.55, and 1.45. The model atmosphere of Arcturus obtained from the best-fit of the wings of the H and K Ca II lines corresponds to the model atmosphere with the fundamental parameters T_eff = 4286 K, log g = 1.66, and [Fe/H]=-0.52 derived by Ramirez and Allende Prieto (2011). The temperature stratification of Arcturus' atmosphere is presented in tabular form. To obtain more accurate temperature stratification in the future, we need a high spectral resolution spectrum calibrated to absolute fluxes with high accuracy.

FUNDAMENTAL PARAMETERS AND CHEMICAL COMPOSITION OF ARCTURUS

We derive a self-consistent set of atmospheric parameters and abundances of 17 elements for the red giant star Arcturus: Teff = 4286+/-30 K, logg = 1.66+/-0.05, and [Fe/H] = -0.52+/-0.04. The effective temperature was determined using model atmosphere fits to the observed spectral energy distribution from the blue to the mid-infrared (0.44 to 10 um). The surface gravity was calculated using the trigonometric parallax of the star and stellar evolution models. A differential abundance analysis relative to the solar spectrum allowed us to derive iron abundances from equivalent width measurements of 37 FeI and 9 FeII lines, unblended in the spectra of both Arcturus and the Sun; the [Fe/H] value adopted is derived from FeI lines. We also determine the mass, radius, and age of Arcturus: M = 1.08+/-0.06 Msun, R = 25.4+/-0.2 Rsun, and t = 7.1(+1.5/-1.2) Gyr. Finally, abundances of the following elements are measured from an equivalent width analysis of atomic features: C, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, and Zn. We find the chemical composition of Arcturus typical of that of a local thick-disk star, consistent with its kinematics.

Open loop adaptive optics testbed on 2.16 meter telescope with liquid crystal corrector

A novel liquid crystal wave front corrector (LCWFC) based open loop adaptive optics testbed for nonpolarized light was introduced in this paper. A polarizing beam splitter (PBS) was used behind the LCWFC to divide the reflected nonpolarized light into two orthogonal polarized lights with and without the modulation effect for high resolution imaging and aberration detection respectively. The alignment direction of LC molecules was parallel to the polarization direction of the light PBS reflected. This configuration was simple and easy for construction. It avoided the energy loss due to the use of polarizer for conventional LCWFC based closed loop adaptive optics system. Furthermore, it could be switched into closed loop configuration very easily, which was useful for quantitative system performance evaluation. The detailed construction and operation was reported in Section 2. In Section 3, this testbed was deployed at the coude focus of the 2.16 m telescope at the Xinglong Station of the Beijing Astronomical Observatory. The observation of star Arcturus was done. The Full Width Half Maximum (FWHM) resolution was improved from 2.12″ to 0.64″ successfully.

Blake: The Complexity of Allusions

IN Jerusalem 52 William Blake composed ‘I saw a Monk of Charlemaine’ (E 201–2),1 a poem rejecting ‘Glorious war’, for Charlemagne—Emperor of the Holy Roman Empire—was renowned for his military conquests. Blake, in modulating his projected text (E 811), denounced ‘Charlemaine & his Clouds of War’ that ‘Muster around the Polar Star’ (E 811), where ‘Charlemaine & his Barons bold / Stood by & mockd in iron & gold’ (E 811).2 Accordingly, Blake identifies warlike ‘Charlemaine’ with circumpolar Boötes (which means plowman), a constellation revolving through the heavens that Blake in turn associates with patronymic Albion3 and with King Arthur (who will rise from his ‘sleep’ and ‘return again’ [DC, E 542] as rex quondam rexque futurus [that once and future king]). Blake’s foregoing phrasing borrows from Edmund Spenser’s The Tears of the Muses (l.462),4 where ‘Charlemaine’ is found ‘amongst the starris seaven’, the seven Polar stars of Charles’ Wain, the stellar Plow of Boötes. Charles’ Wain by tradition was envisioned as seven oxen plowing in the furrows of the night heavens,5 and the star Arcturus in the constellation Boötes, associated with Arturus or King Arthur by legend,6 was additionally linked with Carl or Charlemagne (‘Charlemagne or Charles his wane’).7 Book One of Spenser’s The Faerie Queen (2.1) mentions Boötes, ‘the northerne wagoner’ and his ‘sevenfold teme [team] behind the stedfast [Polar] starre’. In consequence, Blake’s starry Plow of Boötes, circulating around the Polaris, becomes King Charles’ Wain (in variation seen as the Big Dipper). In Book Two of The Faerie Queene (10.4) Spenser also speaks of ‘mighty kings and conquerours in warre’ (the ancestors of Elizabeth, the Virgin Queen), and these bellicose English lords in Spenser’s view performed warlike ‘noble deeds above the northern [Polar] starre,’ thereby achieving ‘Immortal Fame.’8

Differential chemical abundance analysis of a 47 Tucan�� asymptotic giant branch star with respect to Arcturus

This study resolves a discrepancy in the abundance of Zr in the 47 Tucanae asymptotic giant branch star Lee 2525. This star was observed using the echelle spectrograph on the 2.3 m telescope at Siding Spring Observatory. The analysis was undertaken by calibrating Lee 2525 with respect to the standard giant star Arcturus. This work emphasises the importance of using a standard star with stellar parameters comparable to the star under analysis rather than a calibration with respect to the Sun (Koch & McWilliam 2008). Systematic errors in the analysis process are then minimised due to the similarity in atmospheric structure between the standard and programme stars. The abundances derived for Lee 2525 were found to be in general agreement with the Brown & Wallerstein (1992) values except for Zr. In this study Zr has a similar enhancement ([Zr/Fe] = +0.51 dex) to another light s-process element, Y ([Y/Fe] = +0.53 dex), which reflects current theory regarding the enrichment of s-process elements by nuclear processes within AGB stars (Busso et al. 2001). This is contrary to the results of Brown & Wallerstein (1992) where Zr was under-abundant ([Zr/Fe] = +0.51 dex) and Y was over-abundant ([Y/Fe] = +0.50 dex) with respect to Fe.

The K giant star Arcturus: the hybrid nature of its infrared spectrum

<i>Aims. <i/>We investigate the infrared spectrum of Arcturus to clarify the nature of the cool component of its atmosphere, referred to as the CO-mosphere, and its relationship to the warm molecular envelope or the MOLsphere in cooler M (super)giant stars.<i>Methods. <i/>We apply the standard methods of spectral analysis to the CO lines measured from the “Infrared Atlas of the Arcturus Spectrum” by Hinkle, Wallace, and Livingston. <i>Results. <i/>We found that the intermediate-strength lines (with : <i>W<i/> is the equivalent width and <i>ν<i/> the wavenumber) of CO fundamentals as well as overtones cannot be interpreted with the line-by-line analysis based on the classical line formation theory, while the weaker lines can and provide some information on the photosphere (e.g. log <i>A<i/><sub>C<sub/> = 7.97/log , = 1.87 km s<sup>-1<sup/>, and km s<sup>-1<sup/>). The nature of CO lines shows an abrupt change at and the lines stronger than this limit indicate large excess absorption that cannot be photospheric in origin. This difficulty also appears as an unpredictable upturn (at ) in the flat part of the curves-of-growth of CO lines. We confirm the same phenomenon in dozens of M giant stars, whose infrared spectra are known to have hybrid origins in the photosphere and extra-molecular constituent referred to as the MOLsphere. Thus the curve-of-growth analysis provides a simple means by which to recognize the hybrid nature of the infrared spectra. We note that the curves-of-growth of red supergiants and Mira variables found in the literature show similar peculiar patterns. The intermediate-strength lines of CO in Arcturus show only minor expansion (0.6 km s<sup>-1<sup/>) relative to the weak lines and only small line-asymmetry, but the strong lines of the CO fundamentals exhibit higher turbulent velocity than the other CO lines. <i>Conclusions. <i/>The large excess absorption of the CO fundamental lines in Arcturus appears to be the same phenomenon as that found in the CO overtone lines of cooler M giant stars. Thus, molecular condensation referred to as the MOLsphere in cool luminous stars may also exist in Arcturus. The MOLsphere, however, is not necessarily a separate “sphere” but may be an aggregation of molecular clouds formed within the outer atmosphere. The formation of molecular clouds (referred to as MOLsphere in our modeling) in the outer atmosphere appears to be a basic feature of all the red giant stars from early K to late M types (and red supergiants).

Optical vortices with starlight

Aims. In this paper we present our first observations at the Asiago 122 cm telescope of � = 1 optical vortices generated with starlight beams. Methods. We used a fork-hologram blazed at the first diffraction order as a phase modifying device. The multiple system Rasalgethi (α Herculis) in white light and the single star Arcturus (α Bootis) through a 300 A bandpass were observed using a fast CCD camera. In the first case we could adopt the Lucky Imaging approach to partially correct for seeing effects. Results. For both stars, the optical vortices could be clearly detected above the smearing caused by the mediocre seeing conditions. The profiles of the optical vortices produced by the beams of the two main components of the α Her system are consistent with numerically simulated on-axis and off-axis optical vortices. The optical vortices produced by α Boo can also be reproduced by numerical simulations. Our experiments confirm that the ratio between the intensity peaks of an optical vortex can be extremely sensitive to off-axis displacements of the beam. Conclusions. Our results give insights for future astronomical applications of optical vortices both for space telescopes and groundbased telescopes with good seeing conditions and adaptive optics devices. The properties of optical vortices can be used to perform high precision astrometry and tip/tilt correction of the isoplanatic field. We are now designing a � = 2 optical vortex coronagraph around a continuous spiral phase plate. We also point out that optical vortices could find extremely interesting applications also in the infrared and radio wavelengths.

Asteroseismology of red giants: photometric observations of Arcturus by SMEI

Abstract We present new results on oscillations of the K1.5 III giant Arcturus (α Boo), from analysis of just over 2.5 yr of precise photometric observations made by the Solar Mass Ejection Imager on board the Coriolis satellite. A strong mode of oscillation is uncovered by the analysis, having frequency 3.51 ± 0.03 μHz. By fitting its mode peak, we are able to offer a highly constrained direct estimate of the damping time (τ= 24 ± 1 d). The data also hint at the possible presence of several radial-mode overtones, and maybe some non-radial modes. We are also able to measure the properties of the granulation on the star, with the characteristic time-scale for the granulation estimated to be ∼0.50 ± 0.05 d.

Long‐Term Spectroscopic and Precise Radial Velocity Monitoring of Arcturus

This dissertation presents an analysis of data obtained from long-term spectroscopic monitoring of the bright, nearby K giant star Arcturus (a Bootis, K1.5 III, HR 5340, HD 124897), conducted using the University of Western Ontario’s Elginfield Observatory. Over 1300 high-resolution spectra ( ) 5 l/Dl ≈ 10 were recorded in the 6250 A spectral region during the 1984– 2006 observing seasons, with 311 simultaneous, precise radial velocity measurements (j ∼ 25 m s ) obtained during the 2002–2006 observing seasons. Temperature variations were measured using the well-established line-depth ratio V i l6251.83 to Fe i l6252.56. Velocity spans were obtained from the line bisector of the Fe i l6252.56 line. Precise radial velocities were measured using the telluric absorption technique outlined by Gray & Brown (2006, PASP, 118, 399). Spectroscopic observations and precise radial velocity measurements reveal variability in Arcturus from hours to years. From velocity span observations, three distinct periods of variability are observed: (1) a semiregular 5 1 yr period interpreted as evidence for a long-term stellar magnetic cycle, (2) a 2.0 0.2 yr modulation identified as the rotation period (see also Gray & Brown 2006, PASP, 118, 1112), and (3) a semicoherent 200 5 day period interpreted as one-fourth of the rotation period, indicating the presence of four magnetically active longitudes on the surface of Arcturus. One of these four active longitudes is postulated to dominate the other three, inducing the observed 2 yr rotational modulation in the velocity span measurements. Line-depth ratio measurements indicate no evidence for variations in temperature in excess of 10 K over the observed magnetic cycle, rotation period, and short-term variability of Arcturus. Precise radial velocity measurements exhibit a long-term period of 222 3 days, with an amplitude of 150 20 m s . This long-term period and the corresponding amplitude are consistent with the radial velocity observations of Hatzes & Cochrane (1993, ApJ, 413, 339). The 222 day period is coherent over the 14 yr time span between the Hatzes & Cochrane (1993, ApJ, 413, 339) data and the observations of this work, and does not correlate with observed line bisector or line-depth ratio variations, suggesting that this observed period is not associated with stellar variability. Hatzes & Cochrane (1993, ApJ, 413, 339) suggested that the observed long-term radial velocity period was due either to rotational modulation or a low-mass companion, but were unable to differentiate between the two explanations, due to a lack of ancillary spectroscopic data. A detection of a low-mass companion is postulated by this work. Assuming a mass of 1 M, for Arcturus, a best-fit Keplerian orbit to the 222 day period is found to have approximately zero eccentricity, a projected semimajor axis ( ) of 0.72 AU, and a companion a sin i mass ( ) of ≥4.4 MJ. M sin i 2 Precise radial velocity observations also demonstrate a scatter (j) of ∼145 m s 1 superimposed on the observed 222 day period, resulting from short-term variability on the timescale of individual nights to days. This short-term variability has been interpreted as being the result of solar-type p-mode oscillations by previous studies, such as Hatzes & Cochrane (1994, ApJ, 422, 366), Merline (1995, Ph.D. thesis, Univ. Arizona), and Retter et al. (2003, ApJ, 591, L151). Observed scatter during individual nights ranges from ∼50 to 180 m s , while the scatter over consecutive nights ranges from ∼70 to 160 m s . These observations are consistent with previous studies of the short-term radial velocity variability of Arcturus. Ultimately, this scatter of ∼145 m s 1 limits the accuracy of studies of the long-term radial velocity variability of Arcturus. Evidence for eruptive events is also suggested from the observed radial velocities.

Is Arcturus a well-understood K giant?

We present near-IR interferometric measurements of the K1.5 giant Arcturus (alpha Bootis), obtained at the IOTA interferometer with the FLUOR instrument, in four narrow filters with central wavelengths ranging from 2.03 to 2.39 micron. These observations were expected to allow us to quantify the wavelength dependence of the diameter of a typical K giant. They are compared to predictions from both plane-parallel and spherical model atmospheres. Unexpectedly, neither can explain the observed visibilities. We show how these data suggest the presence of a companion, in accordance with the Hipparcos data on this star, and discuss this solution with respect to Arcturus' single star status.

Atmospheric Models of Red Giants with Massive‐Scale Non–Local Thermodynamic Equilibrium

We present plane-parallel and spherical LTE and non-LTE (NLTE) atmospheric models of a variety of stellar parameters of the red giant star Arcturus (α Boo, HD 124897, HR 5340) and study their ability to fit the measured absolute flux distribution. Our NLTE models include tens of thousands of the strongest lines in NLTE, and we investigate separately the effects of treating the light metals and the Fe group elements Fe and Ti in NLTE. We find that the NLTE effects of Fe group elements on the model structure and Fλ distribution are much more important than the NLTE effects of all the light metals combined, and serve to substantially increase the violet and near-UV Fλ levels as a result of NLTE Fe overionization. Both the LTE and NLTE models predict significantly more flux in the blue and UV bands than is observed. We find that within the moderately metal-poor metallicity range, the effect of NLTE on the overall UV flux level decreases with decreasing metallicity. These results suggest that there may still be important UV opacity missing from the models. We find that models of solar metallicity giants of spectral type similar to that of Arcturus fit well the observed flux distributions of those stars from the red to the near-UV band. This suggests that the blue and near-UV flux discrepancy is metallicity dependent, increasing with decreasing metallicity.

Oscillations in Arcturus from WIRE Photometry

Observations of the red giant Arcturus (Alpha Boo) obtained with the star tracker on the Wide Field Infrared Explorer (WIRE) satellite during a baseline of 19 successive days in 2000 July-August are analysed. The amplitude spectrum has a significant excess of power at low-frequencies. The highest peak is at about 4.1 micro-Hz (2.8 d), which is in agreement with previous ground-based radial velocity studies. The variability of Arcturus can be explained by sound waves, but it is not clear whether these are coherent p-mode oscillations or a single mode with a short life-time.

ISO-SWS calibration and the accurate modelling of cool-star atmospheres

The fine calibration of the ISO-SWS detectors (Infrared Space Observatory - Short Wavelength Spectrometer) has proven to be a delicate problem. We therefore present a detailed spectroscopic study in the 2.38 -- 12 micron wavelength range of a sample of 16 A0 -- M2 stars used for the calibration of ISO-SWS. By investigating the discrepancies between the ISO-SWS data of these sources, the theoretical predictions of their spectra, the high-resolution FTS-KP (Kitt Peak) spectrum of Alpha Boo and the solar FTS-ATMOS (Atmospheric Trace Molecule Spectroscopy) spectrum, both calibration problems and problems in computing the theoretical models and the synthetic spectra are revealed. The underlying reasons for these problems are sought for and the impact on the further calibration of ISO-SWS and on the theoretical modelling is discussed extensively.

Detection of Water Vapor in the Photosphere of Arcturus

We report detections of pure rotation lines of OH and H2O in the K1.5 III red giant star Arcturus (α Bootis) using high-resolution, infrared spectra covering the regions 806-822 cm-1 (12.2-12.4 μm) and 884-923 cm-1 (10.8-11.3 μm). Arcturus is the hottest star yet to show water vapor features in its disk-averaged spectrum. We argue that the water vapor lines originate from the photosphere, albeit in the outer layers. We are able to predict the observed strengths of OH and H2O lines satisfactorily after lowering the temperature structure of the outermost parts of the photosphere (log τ500 = -3.8 and beyond) compared to a flux-constant, hydrostatic, standard MARCS model photosphere. Our new model is consistently calculated including chemical equilibrium and radiative transfer from the given temperature structure. Possible reasons for a temperature decrease in the outermost parts of the photosphere and the assumed breakdown of the assumptions made in classical model atmosphere codes are discussed.

Atmosphere parameters of four K-giants obtained by spectrum fitting

Basic parameters of the atmospheres (i.e., Teff, log g, [A/H], vturb) of four late type giant stars alpha Ari, alpha Boo, alpha Cas, beta Gem are obtained by matching synthetic spectra to observed ones. We used model atmosphere to compute the synthetic spectrum. The parameters of the model atmosphere and of the synthetic spectrum are fitted to match the observed spectrum, accelerated by means of a proposed numerical tool.