Line Radial Velocity Research Articles

Catalog & atlas of the LV galaxies

AbstractWe present a database of galaxies in the Local Volume (LV) (https://www.sao.ru/lv/lvgdb/) Kaisina et al. (2012) having individual distance estimates within 11Â Mpc or corrected radial velocities VLG < 600 km s-1. It collects data on the following galaxy observables: angular diameters, apparent magnitudes in far-UV, B, and Ks bands, Hα and HI fluxes, morphological types, HI -line widths, radial velocities, and distance estimates. It also contains a consolidated set of optical images of all the galaxies from the SDSS and DSS surveys and Hα images of galaxies that were derived with the 6-m BTA telescope. The latest version of the Updated Nearby Galaxy Catalog (UNGC) Karachentsev et al. (2013) contains 869 objects, now the database consist of 1175 objects. We present basic relations, describing the updated LV sample: Hubble flow, distribution galaxies according to their distance estimates and on the sky, et al.

A new method of measuring centre-of-mass velocities of radially pulsating stars from high-resolution spectroscopy

We present a radial velocity analysis of 20 solar neighborhood RR Lyrae and 3 Population II Cepheids variables. We obtained high-resolution, moderate-to-high signal-to-noise ratio spectra for most stars and obtained spectra were covering different pulsation phases for each star. To estimate the gamma (center-of-mass) velocities of the program stars, we use two independent methods. The first, `classic' method is based on RR Lyrae radial velocity curve templates. The second method is based on the analysis of absorption line profile asymmetry to determine both the pulsational and the gamma velocities. This second method is based on the Least Squares Deconvolution (LSD) technique applied to analyze the line asymmetry that occurs in the spectra. We obtain measurements of the pulsation component of the radial velocity with an accuracy of $\pm$ 3.5 km s$^{-1}$. The gamma velocity was determined with an accuracy $\pm$ 10 km s$^{-1}$, even for those stars having a small number of spectra. The main advantage of this method is the possibility to get the estimation of gamma velocity even from one spectroscopic observation with uncertain pulsation phase. A detailed investigation of the LSD profile asymmetry shows that the projection factor $p$ varies as a function of the pulsation phase -- this is a key parameter which converts observed spectral line radial velocity variations into photospheric pulsation velocities. As a byproduct of our study, we present 41 densely-spaced synthetic grids of LSD profile bisectors that are based on atmospheric models of RR Lyr covering all pulsation phases.

Properties of the redback millisecond pulsar binary 3FGL J0212.1+5320

Linares et al. (2016) obtained quasi-simultaneous g', r' and i-band light curves and an absorption line radial velocity curve of the secondary star in the redback system 3FGL J0212.1+5320. The light curves showed two maxima and minima primarily due to the secondary star's ellipsoidal modulation, but with unequal maxima and minima. We fit these light curves and radial velocities with our X-ray binary model including either a dark solar-type star spot or a hot spot due to off-centre heating from an intrabinary shock, to account for the unequal maxima. Both models give a radial velocity semi-amplitude and rotational broadening that agree with the observations. The observed secondary star's effective temperature is best matched with the value obtained using the hot spot model, which gives a neutron star and secondary star mass of $M_{\rm 1}$=1.85$^{+0.32}_{-0.26}$ $M_{\odot}$and $M_{\rm 2}$=0.50$^{+0.22}_{-0.19}$ $M_{\odot}$, respectively.

Spectroscopic Comparison of Metal-rich RRab Stars of the Galactic Field with their Metal-poor Counterparts

Abstract We investigate atmospheric properties of 35 stable RRab stars that possess the full ranges of period, light amplitude, and metal abundance found in Galactic RR Lyrae stars. Our results are derived from several thousand echelle spectra obtained over several years with the du Pont telescope of Las Campanas Observatory. Radial velocities of metal lines and the Hα line were used to construct curves of radial velocity versus pulsation phase. From these we estimated radial velocity amplitudes for metal lines (formed near the photosphere) and Hα Doppler cores (formed at small optical depths). We also measured Hα emission fluxes when they appear during primary light rises. Spectra shifted to rest wavelengths, binned into small phase intervals, and co-added were used to perform model atmospheric and abundance analyses. The derived metallicities and those of some previous spectroscopic surveys were combined to produce a new calibration of the Layden abundance scale. We then divided our RRab sample into metal-rich (disk) and metal-poor (halo) groups at [Fe/H] = −1.0; the atmospheres of RRab families, so defined, differ with respect to (a) peak strength of Hα emission flux, (b) Hα radial velocity amplitude, (c) dynamical gravity, (d) stellar radius variation, (e) secondary acceleration during the photometric bump that precedes minimum light, and (f) duration of Hα line-doubling. We also detected Hα line-doubling during the “bump” in the metal-poor family, but not in the metal-rich one. Although all RRab probably are core helium-burning horizontal branch stars, the metal-rich group appears to be a species sui generis.

Cold gas in hot star clusters: the wind from the red supergiant W26 in Westerlund 1

The massive red supergiant (RSG) W26 in Westerlund 1 is one of a growing number of RSGs shown to have winds that are ionized from the outside in. The fate of this dense wind material is important for models of second generation star formation in massive star clusters. Mackey et al. (2014) showed that external photoionization can stall the wind of RSGs and accumulate mass in a dense static shell. We use 1D R-HD simulations of an externally photoionized wind to predict the Halpha and [NII] emission arising from photoionized winds both with and without a dense shell. We analyse spectra of the Halpha and [NII] emission in the environment around W26 and compare them with predicted synthetic emission. Simulations of slow winds that are decelerated into a dense shell show strongly limb-brightened line emission, with line radial velocities that are independent of the wind speed. Faster winds (>22 km/s) do not form a dense shell, have less limb-brightening, and the line radial velocity is a good tracer of the wind speed. The brightness of the [NII] and Halpha lines as a function of distance from W26 agrees reasonably well with observations when only the line flux is considered. The radial velocity disagrees, however: the brightest observed emission is blueshifted by ~25 km/s relative to the radial velocity of the star, whereas a spherically symmetric wind has the brightest emission at zero radial velocity. Our results show that the bright nebula surrounding W26 must be asymmetric; we suggest it is confined by external ram pressure from the wind of the nearby supergiant W9. We obtain a lower limit on the nitrogen abundance within the nebula of 2.35 times solar. The line ratio strongly favours photoionization over shock ionization, and so even if the observed nebula is pressure confined there should still be an ionization front and a photoionization-confined shell closer to the star.

THE 2011 PERIASTRON PASSAGE OF THE Be BINARY δ Scorpii

We describe the results of the world-wide observing campaign of the highly eccentric Be binary system delta Scorpii 2011 periastron passage which involved professional and amateur astronomers. Our spectroscopic observations provided a precise measurement of the system orbital period at 10.8092+/- 0.0005 years. Fitting of the He II 4686A line radial velocity curve determined the periastron passage time on 2011 July 3, UT 9:20 with a 0.9--day uncertainty. Both these results are in a very good agreement with recent findings from interferometry. We also derived new evolutionary masses of the binary components (13 and 8.2 Msun) and a new distance of 136 pc from the Sun, consistent with the HIPPARCOS parallax. The radial velocity and profile variations observed in the H_alpha line near the 2011 periastron reflected the interaction of the secondary component and the circumstellar disk around the primary component. Using these data, we estimated a disk radius of 150 Rsun. Our analysis of the radial velocity variations measured during the periastron passage time in 2000 and 2011 along with those measured during the 20th century, the high eccentricity of the system, and the presence of a bow shock-like structure around it suggest that delta Sco might be a runaway triple system. The third component should be external to the known binary and move on an elliptical orbit that is tilted by at least 40 degree with respect to the binary orbital plane for such a system to be stable and responsible for the observed long-term radial velocity variations.

High ions towards white dwarfs: circumstellar line shifts and stellar temperature

Based on a compilation of OVI, CIV, SiIV and NV data from IUE, FUSE, GHRS, STIS, and COS, we derive an anti- correlation between the stellar temperature and the high ion velocity shift w.r.t. to the photosphere, with positive (resp. negative) velocity shifts for the cooler (resp. hotter) white dwarfs. This trend probably reflects more than a single process, however such a dependence on the WD's temperature again favors a CS origin for a very large fraction of those ion absorptions, previously observed with IUE, HST-STIS, HST-GHRS, FUSE, and now COS, selecting objects for which absorption line radial velocities, stellar effective temperature and photospheric velocity can be found in the literature. Interestingly, and gas in near-equilibrium in the star vicinity. It is also probably significant that the temperature that corresponds to a null radial velocity, i.e. \simeq 50,000K, also corresponds to the threshold below which there is a dichotomy between pure or heavy elements atmospheres as well as some temperature estimates for and a form of balance between radiation pressure and gravitation. This is consistent with ubiquitous evaporation of orbiting dusty material. Together with the fact that the fraction of stars with (red-or blue-) shifted lines and the fraction of stars known to possess heavy species in their atmosphere are of the same order, such a velocity-temperature relationship is consistent with quasi-continuous evaporation of orbiting CS dusty material, followed by accretion and settling down in the photosphere. In view of these results, ion measurements close to the photospheric or the IS velocity should be interpreted with caution, especially for stars at intermediate temperatures. While tracing CS gas, they may be erroneously attributed to photospheric material or to the ISM, explaining the difficulty of finding a coherent pattern of the high ions in the local IS 3D distribution.

Pressure shifts and abundance gradients in the atmosphere of the DAZ white dwarf GALEX J193156.8+011745★

We present a detailed model atmosphere analysis of high-dispersion and high signal-to-noise ratio spectra of the heavily polluted DAZ white dwarf GALEX J1931+0117. The spectra obtained with the VLT-Kueyen/UV-Visual Echelle Spectrograph show several well-resolved Si II spectral lines enabling a study of pressure effects on line profiles. We observed large Stark shifts in silicon lines in agreement with theoretical predictions and laboratory measurements. Taking into account Stark shifts in the calculation of synthetic spectra we reduced the scatter in individual line radial velocity measurements from ~ 3 to < 1 km/s. We present revised abundances of O, Mg, Si, Ca, and Fe based on a critical review of line broadening parameters and oscillator strengths. The new measurements are generally in agreement with our previous analysis with the exception of magnesium with a revised abundance a factor of two lower than previously estimated. The magnesium, silicon and iron abundances exceed solar abundances, but the oxygen and calcium abundances are below solar. Also, we compared the observed line profiles to synthetic spectra computed with variable accretion rates and vertical abundance distributions assuming diffusive steady-state. The inferred accretion rates vary from dM/dt = 2x10^6 for calcium to 2x10^9 g/s for oxygen. We find that the accretion flow must be oxygen-rich while being deficient in calcium relative to solar abundances. The lack of radial velocity variations between two measurement epochs suggests that GALEX J1931+0117 is probably not in a close binary and that the source of the accreted material resides in a debris disc.

A NEW SAMPLE OF VERY MASSIVE STAR FORMING COMPLEXES IN THESPITZERGLIMPSE SURVEY

We examine the thirteen most luminous sources in the WMAP free-free map using the Spitzer GLIMPSE and MSX surveys to identify massive star formation regions, emitting one-third of the Galactic free-free luminosity. We identify star forming regions by a combination of bubble morphology in 8 $\micronm$ (PAH) emission and radio recombination line radial velocities. We find 40 star forming regions associated with our WMAP sources, and determine unique distances to 31. We interpret the bubbles as evidence for radial expansion. The radial velocity distribution for each source allows us to measure the intrinsic speed of a region's expansion. This speed is consistent with the size and age of the bubbles. The high free-free luminosities, combined with negligible synchrotron emission, demonstrate that the bubbles are not driven by supernovae. The kinetic energy of the largest bubbles is a substantial fraction of that measured in the older superbubbles found by Heiles. We find that the energy injected into the ISM by our bubbles is similar to that required to maintain the turbulent motion in the gas disk inside 8 kpc. We report a number of new star forming regions powered by massive ($\textrm{M}_{*} > 10^4 \textrm{M}_\sun$) star clusters. We measure the scale height of the Galactic O stars to be $h_{\textrm{*}} = 35 \pm 5 \pc$. We determine an empirical relationship between the PAH and free-free emission of the form $F_{\textrm{PAH}} \propto F^2_{\textrm{ff}}$. Finally, we find that the bubble geometry is more consistent with a spherical shell rather than a flattened disk.

The spectral variations of MWC 314

AbstractNew spectra of MWC314 are presented; they indicate that the V/R emission line flux ratios show signs of varying in an opposite way to the absorption line radial velocities. The latter appear to be due to apparently non-periodic pulsations, perhaps in strange modes.

Periodic mass-loss episodes due to an oscillation mode with variable amplitude in the hot supergiant HD 50064

<i>Aims. <i/>We aim to interpret the photometric and spectroscopic variability of the luminous blue variable supergiant HD 50064 (<i>V<i/> = 8.21).<i>Methods. <i/>CoRoT space photometry and follow-up high-resolution spectroscopy with a time base of 137 d and 169 d, respectively, was gathered, analysed, and interpreted using standard time series analysis and light curve modelling methods, as well as spectral line diagnostics.<i>Results. <i/>The space photometry reveals one period of 37 d, which undergoes a sudden amplitude change with a factor 1.6. The pulsation period is confirmed in the spectroscopy, which additionally reveals metal line radial velocity values differing by ~30 km s<sup>-1<sup/> depending on the spectral line and on the epoch. We estimate <i>T<i/><sub>eff<sub/> ~ 13 500 K, log <i>g<i/> ~ 1.5 from the equivalent width of Si lines. The Balmer lines reveal that the star undergoes episodes of changing mass loss on a time scale similar to the changes in the photometric and spectroscopic variability, with an average value of log -5 (in M yr<sup>-1<sup/>). We tentatively interpret the 37 d period as the result of a strange mode oscillation.

Wind-swept clouds and possible triggered star formation associated with the supernova remnant G357.7+0.3

We present evidence for interaction between the supernova remnant (SNR) G357.7+0.3 and nearby molecular clouds, leading to the formation of wind-swept structures and bright emission rims. These features are not observed at visual wavelengths, but are clearly visible in mid-infrared mapping undertaken using the Spitzer Space Telescope. Analysis of one of these clouds, the bright cometary structure G357.46+0.60, suggests that it contains strong polycyclic aromatic hydrocarbon emission features in the 5.8 and 8.0 μm photometric bands, and that these are highly variable over relatively small spatial scales. The source is also associated with strong variations in electron density; a far-infrared continuum peak associated with dust temperatures of ∼30 K; and has previously been observed in the 1720 MHz maser transition of OH, known to be associated with SNR shock excitation of interstellar clouds. This source also appears to contain a young stellar object (YSO) within the bright rim structure, with a steeply rising spectrum between 1.25 and 24 μm. If the formation of this star has been triggered recently by the SNR, then YSO modelling suggests a stellar mass ∼5–10 M⊙, and luminosity LYSO∼102–2 × 103 L⊙. Finally, it is noted that a further, conical emission region appears to be associated with the Mira V1139 Sco, and it is suggested that this may represent the case of a Mira outflow interacting with a SNR. If this is the case, however, then the distance to the SNR must be ∼half of that determined from CS J= 2–1 and 3–2 line radial velocities.

The very massive X-ray bright binary system Wack 2134 (= WR 21a)★

Fil: Niemela, Virpi Sinikka. Universidad Nacional de la Plata. Facultad de Ciencias Astronomicas y Geofisicas; Argentina

Analysis of the variability of the luminous emission line star MWC 314

Context. We investigated the surroundings of MWC 314 in the framework of the study of hot emission line star environments using the SAC method. This star is either a B[e] supergiant or a luminous blue variable and appears to be extremely luminous and massive. Aims. We determine the structure and physical conditions of the emitting region and study the possible variations. Methods. We measured the absorption and emission line radial velocities and the emission line fluxes on high-resolution spectra obtained with Aurelie at the 1.52 m OHP telescope in July 1998, with Elodie at the 1.93 m OHP telescope at various epochs, and with echelle spectrographs of the Asiago and Loiano observatories (Italy) in 2006. We used the statistical approach of the self-absorption curve method (SAC) to derive physical parameters of the line-emitting region. Results. We detected drastic variations of the photospheric absorption line radial velocities with time, while the emission line velocities appear to be stable. The Cr II, Ti II, and Fe II emission lines have a complex structure. They are double-peaked, and each of these two 60 km s -1 separated components, is composed of a narrow and a broad component, while the [Fe II] line components are narrower. The fit of the various components of the Fe II lines to a SAC curve indicates that their intensities are affected by some self absorption. We obtained a Boltzmann-type population law whose mean excitation temperature is 6500 +1500 -1000 K for the narrow component lower and upper levels. We obtained a higher Boltzmann-type population law of 10 500 +3000 -2000 K for the forbidden transition upper levels. Conclusions. From the absorption lines we confirm the binarity for MWC 314. The periodicity has nevertheless to be improved with a higher sampling frequency. Our results from the emission lines are consistent with line formation in a rotating disk around a star. The typical minimum radius of the line emitting region obtained from the SAC study is 3.5 x 10 13 cm (2.0 x 10 13 cm < R < 6.3 x 10 13 cm). We argue, in the framework of a very simplified geometrical model, that the [Fe II] lines are emitted farther out than the permitted Cr II, Ti II, and Fell lines, in a disk inclined 25 ± 5 degrees to the plane of sky. If the rotation of the disk is Keplerian, the Fell lines are emitted in a zone defined by 4 x 10 12 cm < R < 7 x 10 13 cm, while for a rotation with conservation of angular momentum, they are emitted from 4 x 10 12 cm < R < 2 x 10 13 cm.

Robust Models for Phase Shifts in Accreting Binary Stars

Radial velocity studies of accreting binary stars commonly use accretion disk emission lines to determine the radial velocity of the primary star and therefore the mass ratio. These emission line radial velocity curves are often shifted in phase from the expected motion of the primary. These phase shifts cast doubt on the use of disk emission lines in the determination of mass ratios. We present a systematic study of phase shifts, using data from the literature to distinguish between possible explanations of the phase shift. We find that one widely adopted class of models is contradicted by observations (section 2). We present a generalized form of another class of models, which we call offset models. We show that these models are quantitatively consistent with existing data (figures 2 and 3, and the discussion in section 4.4). We consider the implications of adopting measurement offset models, for both disk structure and determination of binary parameters. Specifically, we describe in section 6 how measurement offset models may be used improve determinations of the mass ratio based on disk emission lines. This could be a valuable new tool in determining masses of important astrophysical objects such as accreting neutron stars and black holes.

Multimode Pulsations of the λ Bootis Star 29 Cygni: The 1995 and 1996 Multisite Campaigns

In this paper we present the results of multisite photometric and spectroscopic campaigns, carried out during the years 1995 and 1996, to study the pulsations of a typical λ Bootis star, 29 Cyg. During the 1995 campaign we found well-defined multiperiodicity in 29 Cyg, which was studied in detail during a multilongitude campaign covering a 65 day time interval in 1996. The frequency analysis of the 1996 campaign's data easily revealed 11 excited low l degree modes with frequencies of oscillation ranging from 20.3 to 37.4 cycles day-1 and mean photometric amplitudes ranging from 10.65 to 0.96 mmag in the V filter. After removing the well-identified frequencies, the discrete Fourier transform of the residuals showed excess power in the 20-40 cycle day-1 domain, which indicates the probable existence of unresolved rich p-mode spectra with photometric V amplitudes below 0.5 mmag. We found a regular spacing of 2.41 cycles day-1 within the modes of 29 Cyg, which was interpreted as the spacing of consecutive even and odd l-values. The asteroseismic luminosity log L/L⊙ = 1.12, calculated from the frequency spacing, is in good agreement with the Hipparcos luminosity log L/L⊙ = 1.16 and with luminosities from photometric and spectroscopic calibrations. Using our multicolor photometry we tentatively identified the dominant f1 = 37.425 cycle day-1 mode as an l = 2, n = 5 mode, and made radial overtone identification for all frequencies. These ranged from n = 2 to 5. Analysis of the photometric data shows the long-term (years) and probable short-term (days) variability of amplitudes for all of these modes in 29 Cyg. Using our multicolor WBVR filter photometry, we found the wavelength dependence of the pulsation amplitudes for the five highest amplitude modes. Based on the Hα line radial velocity observations of 29 Cyg, we detected multiperiodic radial velocity variations with frequencies of 38.36 and 29.99 cycles day-1 and semiamplitudes of 1.0 and 0.8 km s-1, respectively. These frequencies coincide within the errors with the photometric frequencies of the two highest amplitude modes, 37.425 and 29.775 cycles day-1. For the highest amplitude l = 2, n = 5 mode (37.425 cycles day-1), the radial velocity-to-light amplitude ratio and velocity-to-light phase shift are equal to 2K(Hα)/ΔV = 94 km mag-1 s-1 and Φf1 = - V = +0.08 ± 0.01, respectively, and are in good agreement with values for δ Scuti stars. The rich multiperiodic spectrum makes 29 Cyg a promising target for future multisite campaigns.

Helium abundance and ionization structure in the Orion nebula: radio recombination lines observations

Results of the Ori A HII region mapping based on hydrogen (H), helium (He) and carbon (C) Radio Recombination lines (RRL) are presented. Observations were made with the same angular resolution (2') using the 32 m VLBI dish of Medicina (Italy, 22.4 GHz) and the Pushchino RT-22 dish (Russia, 36.5 GHz). The behaviour of the ionized helium abundance, y + , with distance from the center shows that the He + zone size is smaller than that of H + . Such a behaviour is different for the core and for the envelope, as well as for different directions from the center. The helium abundance, N(He)/N(H) = 10.0(±0.8)%, is measured. Derived line radial velocities, their widths and y + data support the well-known blister-type structure of this HII region. LTE electron temperatures (7800-9600 K) are also measured.

Synthesis of Line Profiles and Radial Velocity Curves for X-Ray Binary Systems

Line profiles and radial velocity curves for optical stars in X-ray binaries are calculated taking into account ellipticity of the optical star and X-ray heating effect.

Simultaneous X-Ray and Optical Observations of EX Hydrae

The intermediate polar, EX Hydrae, was the object of a large simultaneous multiwavelength observational campaign during 2000 May–June. Here we present the Rossi X-Ray Timing Explorer photometry and optical photometry and spectroscopy from ground-based observatories obtained as part of this campaign. Balmer line radial velocities and Doppler maps provide evidence for an extended bulge along the outer edge of the accretion disk and some form of extended/overflowing material originating from the hot spot. In addition, the optical binary eclipse possesses an extended egress shoulder, an indication that an additional source (other than the white dwarf) is coming out of eclipse. We also compare the X-ray and optical results with the results obtained from the EUV and UV observations from the multiwavelength data set.

Near‐Ultraviolet Spectra of Nine M Dwarf Stars, or a Second Effort to Find Optical Coronal Lines in M Dwarf Stars

ABSTRACTWe have searched for optical coronal lines in the 3100–3700 Å region of eight M dwarf stars with rather low levels of activity. This brief survey supplements a similar search in 15 active stars published in 1991. No coronal lines could be identified. However, the emission spectra including lines of H i, He i, Ca ii, Ca i, Si i, and Fe i are described and illustrated. Radial velocities of the emission lines show no systematic differences from the stellar absorption lines. Coronae with temperatures similar to those in the solar corona seem to be rare among the M dwarfs, although at least one example has been found by Schmitt & Wichmann.