New spectroscopic observations of the post-AGB star V354 Lac = IRAS 22272+5435

The strongest absorption features with the lower-level excitation potentials χ _low < 1 eV are found to be split in the high-resolution optical spectra of the post-AGB star V354 Lac taken in 2007–2008 with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. Main parameters, T _eff =5650 K, log g=0.2, ξ _t =5.0 km/s, and the abundances of 22 chemical elements in the star’s atmosphere are found. The overabundance of the s-process chemical elements (Ba, La, Ce, Nd) in the star’s atmosphere is partly due to the splitting of strong lines of the ions of thesemetals. The peculiarities of the spectrum in the wavelength interval containing the LiI λ 6707 Å line can be naturally explained only by taking the overabundances of the CeII and SmII heavy-metal ions into account. The best agreement with the synthetic spectrum is achieved assuming ?(LiI)=2.0, ?(CeII)=3.2, and ?(SmII)=2.7. The velocity field both in the atmosphere and in the circumstellar envelope of V354 Lac remained stationary throughout the last 15 years of our observations.     

On the Evolutionary State of High-Latitude Variable V534 Lyr

Based on the high spectral resolution monitoring conducted at the 6-m BTA telescope, we study the optical spectrum of the high-latitude variable V534 Lyr. Heliocentric radial velocities V_r corresponding to the positions of all metal absorption components, as well as the Na I D and Hα lines were measured during all the observational sets. The analysis of the velocity field examining the lines of various nature revealed a low-amplitude variability of V_r based on the lines with a high excitation potential, which are formed in deep layers of the stellar atmosphere, and allowed to estimate the systemic velocity of V_sys ≈ ?125 kms^?1 (V_lsr ≈ ?105 kms^?1). The distance estimate of d ≈ 6 kpc for the star leads to its absolute magnitude of \(M_V \approx - 5_ \cdot ^m 3\), what corresponds to the spectral classification. The previously undetected spectral phenomenon was revealed for this star: at certain times a splitting of the profiles of low-excited absorptions is observed, reaching ΔV_r = 20–50 kms^?1. A combination of the parameters: reduced metallicity [Met/H]_⊙ = ?0.28, high nitrogen abundance [N/Fe] = +1.10, large spatial velocity, high luminosity, a strong variability of the emission-absorption profiles of HI lines, splitting of metal absorptions at different times of observations and the variability of the velocity field in the atmosphere allow to classify V534 Lyr as a pulsating star in the thick disk of our Galaxy.     

A study of the B[e] star AS 160

We present the results of our study of the poorly known B[e] star AS 160=IRAS 07370-2438. The high-resolution spectrum obtained with the 6-m BTA telescope exhibits strong emission in the Hα line with a two-component profile, indicating that the gaseous envelope of the star is nonspherical. Previously nonanalyzed photometric data suggest the presence of a compact dust envelope. The fundamental parameters of the star (log L/L_⊙ = 4.4 ± 0.2, v sin i = 200 km s^?1 and its distance (3.5±0.5 kpc) have been determined for the first time and are in agreement with published estimates of the MK spectral type of the object (B1.5 V:). Analysis of the object's properties leads us to suggest that this is a binary system that belongs to our recently identified type of Be stars with warm dust.     

Spectroscopy of the W Virginis star V1 (K 307 ) in the globular cluster M12

High-resolution CCD spectra have been obtained for the first time for the W Virginis star V1 (K 307) in the globular cluster M12 and its closest neighbor K 307b (m _pg=14^m; the angular distance from the W Vir star is δ<1 arcsec). We determined the fundamental parameters (T _eff=5600 K, logg=1.3, and T _eff=4200 K, logg=1.0 for the W Vir star and the neighboring star, respectively) and their detailed chemical composition. The derived metallicities of the two stars ([Fe/H]=?1.27 and ?1.22 relative to the solar value) are in good agreement with the metallicities of other cluster members. Changed CNO abundances were found in the atmosphere of the W Vir star: a small carbon overabundance, [C/Fe]=+0.30 dex, and a large nitrogen overabundance, [N/Fe]=+1.15 dex, with oxygen being underabundant, [O/Fe]≈?0.2 dex. The C/O ratio is ≥1. Na and the α-process elements Mg, Al, Si, Ca, and Ti are variously enhanced with respect to iron. We found an enhanced abundance of s-process metals relative to iron: [X/Fe]=+0.34 for Y, Zr, and Ba. The overabundance of the heavier metals La, Ce, and Nd with respect to iron is larger: [X/Fe]=+0.49. The largest overabundance was found for the r-process element europium, [Eu/Fe]=+0.82. The spectrum of the W Vir star exhibits the Hα and Hβ absorption-emission profiles and the He I λ5876 Å emission line, which are traditionally interpreted as a result of shock passage in the atmosphere. However, the radial velocities determined from absorption and emission features are in conflict with the formation pattern of a strong shock. The high luminosity log L/L _⊙ = 2.98, the chemica peculiarities, and the spectral peculiarity are consistent with the post-AGB evolution in the instability strip. The pattern of relative elemental abundances [X/Fe]in the atmosphere of the neighboring star K 307b is solar. Statistically significant differences were found only for sodium and α-process elements: the mean overabundance of light metals is [X/Fe]=+0.35.     

Detection of lithium in the spectrum of the symbiotic Mira star V407 Cygni

We detected the resonance lithium doublet, ⁷LiI λ6708, in the spectra of the symbiotic Mira V407 Cyg (P≈763^d) obtained with a resolution R = λ/Δλ ≈ 18 500. The line equivalent width is ～0.34 Å. The presence of lithium in the atmosphere of the Mira, which, judging by its period, appreciably ascended the asymptotic giant branch (AGB), can be explained by the penetration of its convective envelope into the hot-bottom-burning (HBB) hydrogen-shell source. At the same time, the spectrum of V407 Cyg does not reveal the ZrO λ5551, 6474 absorption bands, which are used to classify S-type stars from low-resolution spectra. We found only weak ZrO λ5718, 6412 bands, which are, however, invisible in low-resolution spectra. Thus, the Mira star V407 Cyg should be classified as being of the spectral type M. In general, the spectrum of V407 Cyg is similar to the spectrum of the red giant in the symbiotic star CH Cyg, but the latter exhibits no lithium lines. The switch-on of the HBB process without any significant enrichment of the atmosphere of an AGB star with s-process elements implies that the third dredge-up is not efficient for some of these stars.     

The evolutionary status of the semiregular variable QY Sge

Repeated spectroscopic observations made with the 6-m telescope of SAO RAS yielded new data on the radial-velocity variability of the anomalous yellow supergiant QY Sge. The strongest and most peculiar feature in its spectrum is the complex profile of NaI D lines, which contains a narrow and a very wide emission components. The wide emission component can be seen to extend from ?170 to +120 km/s, and at its central part it is cut by an absorption feature, which, in turn, is split into two subcomponents by a narrow (16 km/s at r=2.5) emission peak. An analysis of all the Vr values leads us to adopt for the star a systemic velocity of V_r=?21.1 km/s, which corresponds to the position of the narrow emission component of NaI. The locations of emission-line features of NaI D lines are invariable, which point to their formation in regions that are external to the supergiant’s photosphere. Differential line shifts of about 10 km/s are revealed. Emission in the Hα line is weaker than in NaI D lines, it fills the photospheric absorption almost completely. The absorption lines in the spectrum of QY Sge have a substantial width of FWHM ≈ 45 km/s. The method of model atmospheres is used to determine the following parameters: the effective temperature T _eff =6250±150 K, surface gravity l _{g g}=2.0±0.2, and microturbulence velocity ξ _t =4.5±0.5 km/s. The chemical composition of the atmosphere differs only slightly from the solar composition: the metallicity of the star is found to be somewhat higher than the solar metallicity with an average overabundance of iron-peak elements of [Met/H]_⊙=+0.20. The star is found to be slightly overabundant in carbon and nitrogen, [C/Fe]=+0.25, [N/Fe]=+0.27. The α-process elements Mg, Si, and Ca are slightly overabundant, on the average by [α/H]_⊙=+0.12, and sulfur overabundance is higher, [S/α]=+0.29. The strong overabundance of sodium, [Na/Fe]=+0.75, is likely to be due to the dredge-up of the matter processed in the NeNa cycle. Heavy elements of the s-process are underabundant relative to the Sun. On the whole, the observed properties of QY Sge do not give grounds for including this star into the group of RCrB or RVTau-type objects.     

Photometric and spectroscopic study of the supergiant with an infrared excess V1027 Cygni

We present the results of our UBV and JHKLM photometry for the semiregular pulsating variable V1027 Cyg, a supergiant with an infrared excess, over the period from 1997 to 2015 (UBV) and in 2009–2015 (JHKLM). Together with the new data, we analyze the photometric observations of V1027 Cyg that we have obtained and published previously. Our search for a periodicity in the UBV brightness variations has led to several periods from P = 212^d to 320^d in different time intervals. We have found the period P = 237^d based on our infrared photometry. The variability amplitude, the lightcurve shape, and themagnitude of V1027 Cyg atmaximum light change noticeably from cycle to cycle. The deepest minimum was observed in 2011, when the amplitudes of brightness variations in the star reached the following values: ΔU = 1 _. ^m 28, ΔB = 1 _. ^m 10, ΔV = 1 _. ^m 05, ΔJ = 0 _. ^m 30, ΔH = 0 _. ^m 35, ΔK = 0 _. ^m 32, ΔL = 0 _. ^m 26, and ΔM = 0 _. ^m 10. An ambiguous correlation of the B ? V and U ? B colors with the brightness has been revealed. For example, a noticeable bluing of the star was observed during the deep 1992, 2008, and 2011 minima, while the variations with smaller amplitudes show an increase in B ? V at the photometric minima. The spectral energy distribution for V1027 Cyg from our photometry in the range 0.36 (U)–5.0 (M) μm corresponds to spectral types from G8I to K3I at different phases of the pulsation cycle. Low-resolution spectra of V1027 Cyg in the range λ4400–9200 ?A were taken during 16 nights over the period 1995–2015. At the 1995 and 2011 photometric minima the star’s spectrum exhibited molecular TiO bands whose intensity corresponded to spectral types M0–M1, while the photometric data point to a considerably earlier spectral type. We hypothesize that the TiO bands are formed in the upper layers of the extended stellar atmosphere. We have measured the equivalent widths of the strongest absorption lines, in particular, the infrared Ca II triplet in the spectrum of V1027 Cyg. The calcium triplet (Ca T) with W _λ(Ca T) = 20.3 ± 1.8 ?A as a luminosity indicator for supergiants places V1027 Cyg in the region of the brightest G–K supergiants. V1027 Cyg has been identified with the infrared source IRAS 20004+2955 and is currently believed to be a candidate for post-AGB stars. The evolutionary status of the star and its difference from other post-AGB objects are discussed.     

IR photometry results and dust envelope model for symbiotic Mira star candidate V 335 Vul

We present the results of JHKLM-photometry for the symbiotic Mira star candidate V 335 Vul. Based on the average flux data, supplemented by IRAS, MSX, AKARI, and WISE mid-IR observations, we calculated a model of a spherically symmetric dust envelope of the star, made up of amorphous carbon and silicon carbide particles. The optical depth of the envelope in the visible range with a dust temperature at the inner boundary of T₁ = 1300 K is τ _V = 0.58. For an envelope expansion velocity of 26.5 km s^?1, the estimated mass loss rate is equal to 5.7 × 10^?7M_⊙ yr^?1.     

Some peculiarities of the variability of the positional and photometric line parameters in the spectrum of HD 93521. Differential rotation of the star

The variability of positional and photometric parameters of the lines in the spectrum of HD 93521 is analyzed using CCD spectra taken with the PFES echelle spectrograph of the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS). To study the velocity field of the star’s atmosphere, the radial velocity variations are measured separately for the blue and red halves of the absorption profile at different levels of residual line intensity. The amplitude and phase of temporal variations of radial velocity differ for the two halves of the absorption profile. In case of strong HeI, Hβ, andHα lines the amplitude depends on intensity r. The time scales (P) of radial velocity variations and the mean halfwidths \(\overline {FW H M} \) differ for different lines and correlate fairly well with their central depths. The increase of P and decrease of \(\overline {FW H M} \) from weak to strong lines are due to the differential nature of the rotation of the star. Our analysis proofs that HD 93521 is a run-away star and this fact explains its location at a distance of about 2.0 kpc above the Galactic plane.     

Stars with Discrepant <Emphasis Type="Italic">v</Emphasis> sin <Emphasis Type="Italic">i</Emphasis> as Derived from the Ca II 3933 and Mg II 4481 Å Lines. VII. HD9531 (SB), HD31592 (SB2), HD129174 (SB?)

In this paper of the series we analyze three stars listed among stars with discrepant v sin i: HD9531 and HD31592, which also show radial velocity variations inherent to spectroscopic binaries, and HD129174 which is an Mn-type star with a possible magnetic field. In HD9531 we confirm the radial velocity derived fromthe hydrogen lines as well as fromthe Ca II line at 3933 Å as variable. The profile of the calcium line also appears variable, and with the estimated magnetic induction B_e = ?630 ± 1340 G, this suggests that the abundance of calcium possibly varies over the surface of the star. We identified the lines of the secondary component in the spectrum of HD31592 revealing thus it is an SB2 binary with B9.5V and A0V components. While the primary star rotates with v sin i = 50 km s^?1, the secondary star is faster with v sin i = 170 km s^?1. We find that only 60% of the Mn lines identified in the spectrum of HD129174 can be fitted with a unique abundance value, whereas the remaining lines are stronger or fainter. We also identified two Xe II lines at 5339.33 Å and 5419.15 Å and estimated their log g f.     

FG Sge at the stage of dust shell ejection

New photometric observations of the variable star FG Sge, a rapidly evolving planetary nebula nucleus, were performed in 2003–2008. On 230 nights, we obtained 86 UBV and 155 BV RI (or R _c , I _c ) magnitude estimates. The maximum amplitude of the V-band light variations was >8 ^m . Six deep minima and four high maxima were observed. Analysis of the light curve has shown that the pulsation period of the star remained constant since 1991 and was P = 115 days. We have studied the wavelength dependence of the extinction at various phases of the light curve. The blueing of the B-V color at deep minima is interpreted as the result of light scattering in the circumstellar dust shell of the star formed by preceding dust ejections since 1992. Our spectroscopic observations performed on nine nights in 2003–2007 with the 125-cm telescope at the Crimean Station of the Sternberg Institute have confirmed the previously detected intensity variations of the Swan bands and the sodium doublet with brightness. It is noted that the Swan bands originate in the upper atmosphere, the star’s extended envelope, while the sodium doublet originates mainly in the circumstellar shell of FG Sge. We suggest that the star is currently located in the temperature-luminosity diagram at the turning point of the horizontal track of cooling in the direction of hot stars—evolution caused by the last helium shell flash at the planetary nebula stage.     

Analysis of HST ultraviolet spectra for T Tauri stars: DR Tau

We analyze the spectra of DR Tau in the wavelength range 1200 to 3100 Å obtained with the GHRS and STIS spectrographs from the Hubble Space Telescope. The profiles for the C IV 1550 and He II 1640 emission lines and for the absorption features of some lines indicate that matter falls to the star at a velocity ～300 km s^?1. At the same time, absorption features were detected in the blue wings of the N I, Mg I, Fe II, Mg II, C II, and Si II lines, suggesting mass outflow at a velocity up to 400 km s^?1. The C II, Si II, and Al II intercombination lines exhibit symmetric profiles whose peaks have the same radial velocity as the star. This is also true for the emission features of the Fe II and H₂ lines. We believe that stellar activity is attributable to disk accretion of circumstellar matter, with matter reaching the star mainly through the disk and the boundary layer. At the time of observations, the accretion luminosity was L_ac ? 2L_⊙ at an accretion rate ?10^?7M_⊙ yr^?1. Concurrently, a small (<10%) fraction of matter falls to the star along magnetospheric magnetic field lines from a height ～R_*. Within a region of size ?3.5R_*, the disk atmosphere has a thickness ～0.1R_* and a temperature ?1.5 × 10⁴ K. We assume that disk rotation in this region significantly differs from Keplerian rotation. The molecular hydrogen lines are formed in the disk at a distance <1.4 AU from the star. Accretion is accompanied by mass outflow from the accretion-disk surface. In a region of size <10R_*, the wind gas has a temperature ～7000 K, but at the same time, almost all iron is singly ionized by H I L _α photons from inner disk regions. Where the warm-wind velocity reaches ?400 km s^?1, the gas moves at an angle of no less than 30° to the disk plane. We found no evidence of regions with a temperature above 10⁴ K in the wind and leave open the question of whether there is outflow in the H₂ line formation region. According to our estimate, the star has the following set of parameters: M_* ? 0.9M_⊙, R_* ? 1.8R_⊙, L_* ? 0.9L_⊙, and \(A_V \simeq 0\mathop .\limits^m 9\). The inclination i of the disk axis to the line of sight cannot be very small; however, i≤60°.     

Stars with discrepant <Emphasis Type="Italic">v</Emphasis> sin <Emphasis Type="Italic">i</Emphasis> as derived from the Ca II 3933 and Mg II 4481 Å lines. VI. HD 199892 — an SB2 spectroscopic binary

We analyzed the spectra of a well known SB1 binary HD199892 for which the projected rotational velocity v sin i, introduced in the literature, significantly differs when determined from the lines of Ca II at 3933 Å and ofMg II at 4481 Å. Contrary to the former findings, we discovered the signs of spectral lines of a companion star in the profile of Hβ as well as weak metallic lines in the high resolution high S/N spectra covering the most of the visual region. We estimated the secondary star to be a main sequence A4V star with a mass of 2.2M _⊙ and derived its radial velocity which resulted in the mass of the primary M = 4.6M _⊙. Short sections of the spectra in the Mg II 4481 Å and Ca II 3933 Å regions are analyzed as well.     

Some features of the radial-velocity variations of lines of different intensity in the spectrum of HD 93521. Variability of the stellar wind

CCD spectra taken with the PFES echelle spectrograph of the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences are used to perform a detailed study of the variability of the profiles of Hell, Hβ, and Hα lines in the spectrum of HD 93521. The pattern and nature of the variability of the Hell lines are similar to those of weak HeI lines and are due to nonradial pulsations. The period and amplitude of the radial-velocity variations are the same for the blue and red halves of the absorption profile but their phases are opposite. The behavior of the variations of Hβ and Hα hydrogen lines relative to their mean profiles is the same as that of strong HeI line and is due to nonradial pulsations. The period and phase of the radial-velocity oscillations are the same for the blue and red halves of the absorption profile but their amplitude are different. The behavior of the radial-velocity variations of the absorption and emission components of the Hα line indicates that the latter also are caused by nonradial pulsations. All this is indicative of the complex structure of the stellar wind in the region of its origin. The behavior of variability and wind kinematics differ in different directions and for different regions of the atmosphere and/or envelope.     

New in the optical spectrum and kinematic state of the atmosphere of the variable V1027 Cyg (=IRAS 20004+2955)

Based on our high-spectral-resolution observations performed with the NES echelle spectrograph of the 6-m telescope, we have studied the peculiarities of the spectrum and the velocity field in the atmosphere and envelope of the cool supergiant V1027 Cyg, the optical counterpart of the infrared source IRAS 20004+2955. A splitting of the cores of strong absorptions of metals and their ions (Si II, Ni I, Ti I, Ti II, Sc II, Cr I, Fe I, Fe II, BaII) has been detected in the stellar spectrum for the first time. The broad profile of these lines contains a stable weak emission in the core whose position may be considered as the systematic velocity V _sys = 5.5 km s^?1. Small radial velocity variations with an amplitude of 5–6 km s^?1 due to pulsations have been revealed by symmetric low- and moderate-intensity absorptions. A long-wavelength shift of the Hα profile due to line core distortion is observed in the stellar spectrum. Numerous weak CN molecular lines and the KI 7696 Å line with a P Cyg profile have been identified in the red spectral region. The coincidence of the radial velocities measured from symmetric metal absorptions and CN lines suggests that the CN spectrum is formed in the stellar atmosphere. We have identified numerous diffuse interstellar bands (DIBs) whose positions in the spectrum, V _r (DIBs) = ?12.0 km s^?1, correspond to the velocity of the interstellar medium in the Local Arm of the Galaxy.     

Spectroscopic study of the optical counterpart to the fast X-ray transient IGR J17544-2619 based on observations at the 1.5-m RTT-150 telescope

We present the results of our long-term photometric and spectroscopic observations at the Russian–Turkish RTT-150 telescope for the optical counterpart to one of the best-known sources, representatives of the class of fast X-ray transients, IGR J17544-2619. Based on our optical data, we have determined for the first time the orbital and physical parameters of the binary system by the methods of Doppler spectroscopy.We have calculated theoretical spectra of the optical counterpart by applying non- LTE corrections for selected lines and obtained the parameters of the stellar atmosphere (T _eff = 33 000 K, log g = 3.85, R = 9.5 R _⊙, and M = 23 M _⊙). The latter suggest that the optical star is not a supergiant as has been thought previously.     

Symbiotic halo star LT Del: Phase variations of the emission spectrum and parameters of the cool component

Long-term photometric and spectroscopic observations of the yellow symbiotic star LT Del are analyzed. UBV light curves are presented. Based on the observations of 20 cycles, we have refined the orbital period of the star, P = 476 _· ^d 0 ± 1 _· ^d 0. The brightness has been found to be unstable at some orbital phases with an amplitude up to 0 _· ^m 3. We have measured the fluxes in hydrogen and helium emission lines and in continuum and investigated their relationship to the orbital period. The fluxes in hydrogen and HeI lines follow the UBV light curves in phase; the He II 4686 Å flux does not depend on the phase and is constant within the accuracy of our measurements. The intensity ratio of the 4686 Å andHβ lines changes from 0.2 to 0.9 over the period. We interpret the spectroscopic observations based on the hypothesis of heating and ionization of the stellar wind from a cool component by high-frequency radiation from a hot star with a temperature of 105 K. We have estimated the spectral type of the cool star from our photometry and its continuum energy distribution as a bright K2–4 red giant branch halo star. The bolometric luminosity and mass loss rate have been estimated for the K component to be L _bol ～ 700L _⊙ and \(\dot{M}\) ～ 10^?8 M _⊙ yr^?1, respectively.     

Multicolor Photometry and Spectroscopy of the Yellow Supergiant with Dust Envelope HD 179821 = V1427 Aquilae

We present the results of multicolor (UBV JHKLM) photometry (2009–2017) and low-resolution spectroscopy (2016–2017) of the semi-regular variable V1427 Aql = HD 179821, a yellow supergiant with gas-dust envelope. The star displays low-amplitude (ΔV<0 _. ^m 2) semi-periodic brightness variations superimposed on a long-term trend. The light curve shape and timescale change from cycle to cycle. There are temperature variations characteristic for pulsations; brightness oscillations with no significant change of color are also observed. The UBV data for the 2009–2011 interval are well reproduced by a superposition of two periodic components with P = 170^d and 141^d (or P = 217^d—the one year alias of P = 141^d). The variation became less regular after 2011, the timescale increased and exceeded 250^d. Unusual photometric behavior was seen in 2015 when the star brightness increased by 0 _. ^m 25 in the V filter in 130 days and reached the maximum value ever observed in the course of our monitoring since 1990. In 2009–2016 the annual average brightness monotonically increased in V, J, K, whereas it decreased in U and B. The annual average U ? B, B ? V, and J ? K colors grew, the star was getting redder. The cooling and expanding of the star photosphere along with the increasing of luminosity may explain the long-term trend in brightness and colors. Based on our photometric data we suppose that the photosphere temperature decreased by ~400 K in the 2008–2016 interval, the radius increased by ~24%, and the luminosity grew by ~19%. We review the change of annual average photometric data for almost 30 years of observations. Low-resolution spectra in the λ4000?9000 Å wavelength range obtained in 2016–2017 indicate significant changes in the spectrum of V1427 Aql as compared with the 1994–2008 interval, i.e., the Ba II and near-infraredCa II triplet absorptions have gotten stronger while the OI λ7771-4 triplet blend has weakened that points out the decrease of temperature in the region where the absorptions are formed. The evolutionary stage of the star is discussed. We also compare V1427 Aql with post-AGB stars and yellow hypergiants.     

Variability of hot supergiant IRAS 19336-0400 in the early phase of planetary nebula ionization

We present photoelectric and spectral observations of a hot candidate proto-planetary nebula—early B-type supergiant with emission lines in spectrum—IRAS 19336-0400. The light and color curves display fast irregular brightness variations with maximum amplitudes \(\Delta V = 0_ \cdot ^m 30\), \(\Delta B = 0_ \cdot ^m 35\), \(\Delta U = 0_ \cdot ^m 40\) and color-brightness correlations. By the variability characteristics IRAS 19336-0400 appears similar to other hot proto-planetary nebulae. Based on low-resolution spectra in the range λ4000–7500 Å we have derived absolute intensities of the emission lines Hα, Hβ, Hγ, [S II], [N II], physical conditions in gaseous nebula: n _e = 10⁴ cm^?3, T _e = 7000 ± 1000 K. The emission line Hα, Hβ equivalent widths are found to be considerably variable and related to light changes. By UBV-photometry and spectroscopy the color excess has been estimated: E _B-V = 0.50–0.54. Joint photometric and spectral data analysis allows us to assume that the star variability is caused by stellar wind variations.     

Luminescence in Primordial Helium Lines at the Pre-recombination Epoch

The formation of luminescent subordinate He I lines by the absorption of radiation from a source in lines of the main He I series in an expanding Universe is considered. A burst of radiation in continuum is assumed to occur at some instant of time corresponding to redshift z₀. This radiation is partially absorbed at different z < z₀ in lines of the main He I series (different pumping channels) and then is partially converted into radiation in subordinate lines. If ν _ik is the laboratory transition frequency of some subordinate line emerging at some z, then at the present epoch its frequency will be ν = ν _ik /(1 + z). The quantum yield, i.e., the number of photons emitted in the subordinate line per initial excited atom, has been calculated for different z (and, consequently, for different ν). Several pumping channels have been considered. We show that the luminescent lines can be both emission and absorption ones; the same line can be an emission one for one of the pumping channels and an absorption one for another. For example, the 1s2s–1s2p (1S–1P*) line is an emission one for the 1s2–1s2p pumping and an absorption one for the 1s2–1s3p pumping. We show that in the frequency range 30–80 GHz the total quantum yield for the first and second of the above channels can reach +50 and ?50%, respectively.