- ID:
- ivo://CDS.VizieR/J/ApJ/754/69
- Title:
- UV spectroscopy of solar-mass stars
- Short Name:
- J/ApJ/754/69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare high-resolution ultraviolet spectra of the Sun and thirteen solar-mass main-sequence stars with different rotational periods that serve as proxies for their different ages and magnetic field structures. In this, the second paper in the series, we study the dependence of ultraviolet emission-line centroid velocities on stellar rotation period, as rotation rates decrease from that of the Pleiades star HII314 (P_rot_=1.47days) to {alpha} Cen A (P_rot_=28days). Our stellar sample of F9 V to G5 V stars consists of six stars observed with the Cosmic Origins Spectrograph on the Hubble Space Telescope (HST) and eight stars observed with the Space Telescope Imaging Spectrograph on HST. We find a systematic trend of increasing redshift with more rapid rotation (decreasing rotation period) that is similar to the increase in line redshift between quiet and plage regions on the Sun. The fastest-rotating solar-mass star in our study, HII314, shows significantly enhanced redshifts at all temperatures above logT=4.6, including the corona, which is very different from the redshift pattern observed in the more slowly rotating stars. This difference in the redshift pattern suggests that a qualitative change in the magnetic-heating process occurs near P_rot_=2days. We propose that HII314 is an example of a solar-mass star with a magnetic heating rate too large for the physical processes responsible for the redshift pattern to operate in the same way as for the more slowly rotating stars. HII314 may therefore lie above the high activity end of the set of solar-like phenomena that is often called the "solar-stellar connection."
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/158/95
- Title:
- V348 And and V572 Per: heliocentric minima and RVs
- Short Name:
- J/AJ/158/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The eclipsing binaries are still important objects for our understanding of the universe. Especially these ones located within the more complex multiple systems can help us solving the problem of their origin and subsequent evolution of these higher order multiples. Photometry and spectroscopy spanning over more than 25 yr were used for the first complete analysis of the two bright triple systems, namely V348 And and V572 Per. The light curves in photometric filters were combined together with the radial velocities and analyzed simultaneously, yielding the precise physical parameters of the eclipsing components of these multiple systems. The system V348 And consists of two eclipsing components with its orbital period of about 27.7 days. The system is a very detached one, and both eclipses are rather narrow, lasting only about 0.016 of its period. The visual orbit of the wide pair has the period of about 87 yr. All three components of the system are probably of B8-9 spectral type, and the parallax of the system was slightly shifted to the value of 2.92 mas. On the other hand, the system V572 Per shows apsidal motion of its inner orbit, the orbital period being of about 1.2 days, while the apsidal motion of about 48 yr. The components are of A and F spectral types, while the motion with the third component around a common barycenter is only negligible. According to our modeling, this system is not a member of open cluster Alpha Persei.
- ID:
- ivo://CDS.VizieR/J/ApJ/766/116
- Title:
- Variability in proto-PNe. II.
- Short Name:
- J/ApJ/766/116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out a detailed observational study of the light, color, and velocity variations of two bright, carbon-rich proto-planetary nebulae, IRAS 22223+4327 and 22272+5435. The light curves are based upon our observations from 1994 to 2011, together with published data by Arkhipova and collaborators. They each display four significant periods, with primary periods for IRAS 22223+4327 and 22272+5435 being 90 and 132 days, respectively. For each of them, the ratio of secondary to primary period is 0.95, a value much different from that found in Cepheids, but which may be characteristic of post-asymptotic giant branch (AGB) stars. Fewer significant periods are found in the smaller radial velocity data sets, but they agree with those of the light curves. The color curves generally mimic the light curves, with the objects reddest when faintest. A comparison in seasons when there exist contemporaneous light, color, and velocity curves reveals that the light and color curves are in phase, while the radial velocity curves are ~0.25 P out of phase with the light curves. Thus they differ from what is seen in Cepheids, in which the radial velocity curve is 0.50 P out of phase with the light curve. Comparison of the observed periods and amplitudes with those of post-AGB pulsation models shows poor agreement, especially for the periods, which are much longer than predicted. These observational data, particularly the contemporaneous light, color, and velocity curves, provide an excellent benchmark for new pulsation models of cool stars in the post-AGB, proto-planetary nebula phase.
- ID:
- ivo://CDS.VizieR/J/PAZh/25/209
- Title:
- Variability of peculiar star HD 108
- Short Name:
- J/PAZh/25/209
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of fifteen-year-long observations of optical spectra and BVR photoelectric photometry of the runaway star HD 108 are presented.
2075. Variability of WR 86
- ID:
- ivo://CDS.VizieR/J/A+A/384/1012
- Title:
- Variability of WR 86
- Short Name:
- J/A+A/384/1012
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The tables present photometric monitoring of WR 86 in the Walraven VBLUW system during two nights in July 1989, three nights in May/June 1990 and six nights in June 1990, together with UBV photometry during one night in 1995. Radial velocity measurements of WR86 for six emission lines in 1989, three emission lines in 1995 and two absorption lines in 1995. Equivalent width measurements of WR86 for five emission lines in 1989 and three emission lines in 1995.
- ID:
- ivo://CDS.VizieR/J/A+A/463/589
- Title:
- Variables stars in NGC 362
- Short Name:
- J/A+A/463/589
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 362 is a bright southern globular cluster in the foreground of the Small Magellanic Cloud (SMC), for which no extensive variability survey has ever been done. Finding regularly pulsating RR Lyrae stars in the cluster can lead to improved metallicity and distance estimates of the system, while other types of variable objects may be used to confirm the results. Time-series CCD photometric observations have been obtained. Light curves have been derived with both profile fitting photometry and image subtraction. We developed a simple method to convert flux phase curves to magnitudes, which allows the use of empirical light curve shape vs. physical parameters calibrations. Periods and light curve parameters of the detected variable stars have been determined with Fourier analysis, phase dispersion minimization and string-length minimization. Using the RR Lyrae metallicity and luminosity calibrations, we have determined the relative iron abundances and absolute magnitudes of the stars. The color-magnitude diagram has been fitted with Yale-Yonsei isochrones to determine reddening and distance independently. For five RR Lyrae stars we obtained radial velocity measurements from optical spectra. We found 45 RR Lyr stars, of which the majority are new discoveries. While most of them are cluster members, as shown by their radial velocities and positions in the color-magnitude diagram, we also see a few stars in the galactic field and in the outskirts of the SMC. About half of the RR Lyraes exhibit light curve changes (Blazhko effect). The RR Lyrae-based metallicity of the cluster is [Fe/H]=-1.16+/-0.25, the mean absolute magnitude of the RR Lyrae stars is M_V=0.82+/-0.04mag implying a distance of 7.9+/-0.6kpc. The mean period of RRab stars is 0.585+/-0.081days. These properties place NGC 362 among the Oosterhoff type I globular clusters. The isochrone fit implies a slightly larger distance of 9.2+/-0.5kpc and an age of 11+/-1Gyr. We also found 11 eclipsing binaries, 14 pulsating stars of other types, including classical Cepheids in the SMC and 15 variable stars with no firm classification. NGC 362 hosts a large number of RR Lyrae stars, which makes the cluster a potentially important test object for studying the Blazhko effect in a chemically homogeneous environment.
- ID:
- ivo://CDS.VizieR/J/ApJ/809/159
- Title:
- Variations of RS CVn primaries. II. o Dra
- Short Name:
- J/ApJ/809/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To measure the stellar and orbital properties of the metal-poor RS CVn binary o Draconis (o Dra), we directly detect the companion using interferometric observations obtained with the Michigan InfraRed Combiner at Georgia State University's Center for High Angular Resolution Astronomy (CHARA) Array. The H-band flux ratio between the primary and secondary stars is the highest confirmed flux ratio (370+/-40) observed with long-baseline optical interferometry. These detections are combined with radial velocity data of both the primary and secondary stars, including new data obtained with the Tillinghast Reflector Echelle Spectrograph on the Tillinghast Reflector at the Fred Lawrence Whipple Observatory and the 2m Tennessee State University Automated Spectroscopic Telescope at Fairborn Observatory. We determine an orbit from which we find model-independent masses and ages of the components (M_A_=1.35+/-0.05M_{sun}_, M_B_=0.99+/-0.02M_{sun}_, system age =3.0+-0.5Gyr). An average of a 23-year light curve of o Dra from the Tennessee State University Automated Photometric Telescope folded over the orbital period newly reveals eclipses and the quasi-sinusoidal signature of ellipsoidal variations. The modeled light curve for our system's stellar and orbital parameters confirm these ellipsoidal variations due to the primary star partially filling its Roche lobe potential, suggesting most of the photometric variations are not due to stellar activity (starspots). Measuring gravity darkening from the average light curve gives a best-fit of {beta}=0.07+/-0.03, a value consistent with conventional theory for convective envelope stars. The primary star also exhibits an anomalously short rotation period, which, when taken with other system parameters, suggests the star likely engulfed a low-mass companion that had recently spun-up the star.
- ID:
- ivo://CDS.VizieR/J/AJ/159/121
- Title:
- V-band light curve & RVs of the Cepheid V473Lyr
- Short Name:
- J/AJ/159/121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- V473Lyr is a classical Cepheid that is unique in having substantial amplitude variations with a period of approximately 3.3yr, thought to be similar to the Blazhko variations in RR Lyrae stars. We obtained an X-ray Multi-Mirror Mission (XMM)-Newton observation of this star to follow up a previous detection in X-rays. Rather than the X-ray burst and rapid decline near maximum radius seen in {delta}Cephei itself, the X-ray flux in V473Lyr remained constant for a third of the pulsation cycle covered by the observation. Thus the X-rays are probably not produced by the changes around the pulsation cycle. The X-ray spectrum is soft (kT=0.6keV), with X-ray properties consistent with a young low-mass companion. Previously there was no evidence of a companion in radial velocities or in Gaia and Hipparcos proper motions. While this rules out companions that are very close or very distant, a binary companion at a separation between 30 and 300au is possible. This is an example of an X-ray observation revealing evidence of a low-mass companion, which is important in completing the mass ratio statistics of binary Cepheids. Furthermore, the detection of a young X-ray bright companion is a further indication that the Cepheid (primary) is a Population I star, even though its pulsation behavior differs from other classical Cepheids.
- ID:
- ivo://CDS.VizieR/J/ApJ/846/115
- Title:
- V-band photometry and RVs of V482 Persei system
- Short Name:
- J/ApJ/846/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report spectroscopic and differential photometric observations of the A-type system V482 Per, which reveal it to be a rare hierarchical quadruple system containing two eclipsing binaries. One binary has the previously known orbital period of 2.4 days and a circular orbit, and the other a period of 6 days, a slightly eccentric orbit (e=0.11), and shallow eclipses only 2.3% deep. The two binaries revolve around their common center of mass in a highly elongated orbit (e=0.85) with a period of 16.67yr. Radial velocities are measured for all components from our quadruple-lined spectra and are combined with the light curves and measurements of times of minimum light for the 2.4 day binary to solve for the elements of the inner and outer orbits simultaneously. The line-of-sight inclination angles of the three orbits are similar, suggesting they may be close to coplanar. The available observations appear to indicate that the 6 day binary experiences significant retrograde apsidal motion in the amount of about 60 deg per century. We derive absolute masses for the four stars good to better than 1.5%, along with radii with formal errors of 1.1% and 3.5% for the 2.4 day binary and ~9% for the 6 day binary. A comparison of these and other physical properties with current stellar evolution models gives excellent agreement for a metallicity of [Fe/H]=-0.15 and an age of 360Myr.
- ID:
- ivo://CDS.VizieR/J/AJ/131/814
- Title:
- VCC 1087 globular cluster system
- Short Name:
- J/AJ/131/814
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the globular cluster (GC) system of the nucleated dwarf elliptical galaxy VCC 1087 in the Virgo Cluster based on Keck LRIS spectroscopy and archival Hubble Space Telescope Advanced Camera for Surveys imaging. We estimate that VCC 1087 hosts a total population of 77+/-19 GCs, which corresponds to a relatively high V-band specific frequency of 5.8+/-1.4. The g_475_-z_850_ color distribution of the GCs shows a blue (metal-poor) peak with a tail of redder (metal-rich) clusters similar in color to those seen in luminous elliptical galaxies.
