- ID:
- ivo://CDS.VizieR/J/AJ/158/175
- Title:
- Photometric & spectroscopic study of AF And in M31
- Short Name:
- J/AJ/158/175
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a photometric and spectroscopic analysis of the Hubble-Sandage variable star AF And in M31. The data have been taken under the Nainital Microlensing Survey during 1998-2002, and follow-up observations were carried out until 2011. During this period, photometric observations in Cousins R and I bands were obtained for 169 nights spanning about 5000 days. AF And showed a prominent outburst around 1999 mid-January, followed by a gradual decrease in brightness of about 1.5 mag in the next 3 yr with a declining rate of ~0.0015 mag/day, leading to a quiescent phase at the end of 2001. After lying low for about 9 yr, AF And again went through a secondary outburst phase in late 2010 with an amplitude of 0.44 mag, where it lasted for one year before fading back to its quiescent phase. Spectroscopic observations of AF And show prominent Balmer and He I emission lines along with the comparatively weaker Fe II and [Fe II] emissions. Asymmetric emission line profiles in its spectrum imply a mass-loss rate of about 2.2x10^-4^ M_{sun}_/yr through the stellar winds in the photosphere. Using spectral energy distribution fitting, we find a photospheric temperature of 33000+/-3000 K during the visual minimum. Using a weak P Cygni profile of the He I emission line, the wind terminal velocity for AF And is found to be around 280-300 km/s.
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- ID:
- ivo://CDS.VizieR/J/PAZh/35/592
- Title:
- Photometry of FG Sge at the ejection state
- Short Name:
- J/PAZh/35/592
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 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 BVRI (or Rc, Ic) magnitude estimates. The maximum amplitude of the V-band light variations was >8mag. Six deep minima and four high maxima were observed.
- ID:
- ivo://CDS.VizieR/J/A+A/524/A99
- Title:
- Polarisation of S Per and VX Sgr in OH
- Short Name:
- J/A+A/524/A99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Two red supergiant star S Per and VX Sgr were observed in the OH 1612 and 1667MHz maser lines with the Nancay radio telescope at several runs in 2002-2005 and 2002-2008, respectively. Both targets were sampled at irregular intervals of 2-3 days up to 4 months. Time series of OH spectra in the Stokes parameters I, Q, U and V are presented. The spectra of the linearly polarized flux density, p=sqrt{Q^2^+U^2^}, the degrees of circular polarization, m_C_=V/I linear polarization, m_L_=p/I, and position angle, {chi}=0.5xtan^-1^(U/Q), drived from the Stokes parameters are also given. The degrees of polarization at 1667MHz show diverse behaviours usually uncorrelated with the total flux, whereas those at 1612MHz are commonly stable on time scales of 4-6yr. Several outbursts of the 1667MHz emission on time scales of 0.5-2yr were found in both targets. The bursting features are highly polarized and show drifts in velocity. Small changes of the degrees of polarization and smooth variations of position angle of linear polarization during the bursts were observed in S Per but they are more dramatic in VX Sgr.
- ID:
- ivo://CDS.VizieR/J/ApJ/897/48
- Title:
- Properties of Galactic Be Supergiants. VI.
- Short Name:
- J/ApJ/897/48
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- We report the results of long-term spectroscopic monitoring of the A-type supergiant with the B[e] phenomenon 3Pup=HD62623. We confirm earlier findings that it is a binary system. The orbital parameters were derived using cross-correlation of the spectra in a range of 4460-4632{AA}, which contains over 30 absorption lines. The orbit was found to be circular with a period of 137.4{+/-}0.1days, radial velocity semiamplitude K1=5.0{+/-}0.8km/s, systemic radial velocity {gamma}=26.4{+/-}2.0km/s, and mass function f(m)=(1.81_-0.76_^+0.97^)x10^-3^M{sun}. The object may have evolved from a pair with initial masses of ~6.0M{odot} and ~3.6M{sun} with an initial orbital period of ~5days. Based on the fundamental parameters of the A-supergiant (luminosity log L/L{sun}=4.1{+/-}0.1 and effective temperature Teff=8500{+/-}500K) and evolutionary tracks of mass-transferring binaries, we found current masses of the gainer M2=8.8{+/-}0.5M{sun} and donor M1=0.75{+/-}0.25M{sun}. We also modeled the object's IR-excess and derived a dust mass of ~5x10^-5^M{sun} in the optically thin dusty disk. The orbital parameters and properties of the H{alpha} line profile suggest that the circumstellar gaseous disk is predominantly circumbinary. The relatively low mass of the gainer led us to a suggestion that 3 Pup should be excluded from the B[e] supergiant group and moved to the FSCMa group. Overall these results further support our original suggestion that FSCMa objects are binary systems, where an earlier mass transfer caused formation of the circumstellar envelope.
- ID:
- ivo://CDS.VizieR/J/AJ/155/207
- Title:
- Properties of yellow supergiant stars in the SMC
- Short Name:
- J/AJ/155/207
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We recently discovered a yellow supergiant (YSG) in the Small Magellanic Cloud (SMC) with a heliocentric radial velocity of ~300 km/s, which is much larger than expected for a star at its location in the SMC. This is the first runaway YSG ever discovered and only the second evolved runaway star discovered in a galaxy other than the Milky Way. We classify the star as G5-8 I and use de-reddened broad-band colors with model atmospheres to determine an effective temperature of 4700+/-250 K, consistent with what is expected from its spectral type. The star's luminosity is then log L/L_{sun}_~4.2~0.1, consistent with it being a ~30 Myr 9 M_{sun}_ star according to the Geneva evolution models. The star is currently located in the outer portion of the SMC's body, but if the star's transverse peculiar velocity is similar to its peculiar radial velocity, in 10 Myr the star would have moved 1.6{deg} across the disk of the SMC and could easily have been born in one of the SMC's star-forming regions. Based on its large radial velocity, we suggest it originated in a binary system where the primary exploded as a supernovae, thus flinging the runaway star out into space. Such stars may provide an important mechanism for the dispersal of heavier elements in galaxies given the large percentage of massive stars that are runaways. In the future, we hope to look into additional evolved runaway stars that were discovered as part of our other past surveys.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A146
- Title:
- Radial Velocity and BIS measurements of Polaris
- Short Name:
- J/A+A/623/A146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate temporally changing variability amplitudes and the multi- periodicity of the type-I Cepheid Polaris using 162 high-precision radial velocity (RV) and bisector inverse span (BIS) measurements based on optical spectra recorded using Hermes at the 1.2m Flemish Mercator telescope on La Palma, Canary Islands, Spain. Using an empirical template fitting method, we show that Polaris' RV amplitude has been stable to within ~30m/s between September 2011 and November 2018. We apply the template fitting method to publicly accessible, homogeneous RV data sets from the literature and provide an updated solution of Polaris' eccentric 29.3yr orbit. While the inferred pulsation-induced RV amplitudes differ among individual data sets, we find no evidence for time-variable RV amplitudes in any of the separately considered, homogeneous data sets. Additionally, we find that increasing photometric amplitudes determined using SMEI photometry are likely spurious detections due to as yet ill-understood systematic effects of instrumental origin. Given this confusing situation, further analysis of high-quality homogeneous data sets with well-understood systematics is required to confidently establish whether Polaris' variability amplitude is subject to change over time. We confirm periodic bisector variability periods of 3.97d and 40.22d using Hermes BIS measurements and identify a third signal at a period of 60.17d. Although the 60.17d signal dominates the BIS periodogram, we caution that this signal may not be independent of the 40.22d signal. Finally, we show that the 40.22d signal cannot be explained by stellar rotation. Further long-term, high-quality spectroscopic monitoring is required to unravel the complete set of Polaris' periodic signals, which has the potential to provide unprecedented insights into the evolution of Cepheid variables.
- ID:
- ivo://CDS.VizieR/J/A+A/281/161
- Title:
- Radio emission from stars at 250GHz
- Short Name:
- J/A+A/281/161
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the IRAM 30 m-telescope together with the Max Planck Institute for Radio Astronomy (MPIfR) bolometer to survey nearly 270 stars of different types for 250GHz continuum emission. We compare these data with their low frequency (cm-range) properties. Early type stars show very often a deviation from the uniformly expanding wind model which we tentatively attribute to temperature and/or density fluctuations in their deeper atmospheric layers. For WR stars this deviation seems to depend on the effective temperature. Pre-main sequence stars usually seem to be surrounded by a shell of warm dust making a substantial contribution to the 250 GHz flux density value. We have found especially for nearby giants and supergiants that a layer at the transition from photosphere to chromosphere emits ample 250 GHz radiation. We show that the present data can still be explained by a simple uniformly illuminated disk model with the known stellar radius. Optically variable stars are not very strong emitters at 250 GHz. We preferentially detected the more exotic ones, a few Beta Lyr-type and symbiotic stars. Comments on many individual objects are given in the appropriate sections.
- ID:
- ivo://CDS.VizieR/J/A+A/439/1107
- Title:
- R-band spectra for 13 early-type supergiants
- Short Name:
- J/A+A/439/1107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue contains R-band spectra for 13 early-type supergiants. Spectral types range from B0 to A6, all with luminosity classes Ia or Iab. Eight of the stars are classified as having emission. The wavelength range is 5846 to 7030{AA} at a spectral resolution of 1.2{AA}, and a signal-to-noise ratio of 400 or above. Identification of spectral lines in supergiant spectra can be found in Chentsov et al. (2003A&A...397.1035C). The reader should be aware of the blends of atmospheric telluric lines that contaminate the spectra in the ranges 5870-5995{AA}, 6270-6315{AA}, 6470-6500{AA}, and 6850{AA} onwards.
- ID:
- ivo://CDS.VizieR/J/MNRAS/389/1336
- Title:
- Reddenings of FGK supergiants & Cepheids
- Short Name:
- J/MNRAS/389/1336
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate and homogeneous atmospheric parameters (Teff, logg, Vt, [Fe/H]) are derived for 74 FGK non-variable supergiants from high-resolution, high signal-to-noise ratio, echelle spectra. Extremely high precision for the inferred effective temperatures (10-40K) is achieved by using the line-depth ratio method. The new data are combined with atmospheric values for 164 classical Cepheids, observed at 675 different pulsation phases, taken from our previously published studies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/475/2003
- Title:
- Red supergiant population in Perseus arm
- Short Name:
- J/MNRAS/475/2003
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new catalogue of cool supergiants in a section of the Perseus arm, most of which had not been previously identified. To generate it, we have used a set of well-defined photometric criteria to select a large number of candidates (637) that were later observed at intermediate resolution in the infrared calcium triplet spectral range, using a long-slit spectrograph. To separate red supergiants from luminous red giants, we used a statistical method, developed in previous works and improved in the present paper. We present a method to assign probabilities of being a red supergiant to a given spectrum and use the properties of a population to generate clean samples, without contamination from lower luminosity stars. We compare our identification with a classification done using classical criteria and discuss their respective efficiencies and contaminations as identification methods. We confirm that our method is as efficient at finding supergiants as the best classical methods, but with a far lower contamination by red giants than any other method. The result is a catalogue with 197 cool supergiants, 191 of which did not appear in previous lists of red supergiants. This is the largest coherent catalogue of cool supergiants in the Galaxy.
