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- ID:
- ivo://CDS.VizieR/J/A+A/642/A225
- Title:
- Faculae-Spot dominance & rotation periods
- Short Name:
- J/A+A/642/A225
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar rotation periods can be determined by observing brightness variations caused by active magnetic regions transiting visible stellar disk as the star rotates. The successful stellar photometric surveys stemming from the Kepler and TESS observations led to the determination of rotation periods in tens of thousands of young and active stars. However, there is still a lack of information about rotation periods of older and less active stars, like the Sun. The irregular temporal profiles of light curves caused by the decay times of active regions, which are comparable to or even shorter than stellar rotation periods, combine with the random emergence of active regions to make period determination for such stars very difficult. We tested the performance of the new method for the determination of stellar rotation periods against stars with previously determined rotation periods. The method is based on calculating the gradient of the power spectrum (GPS) and identifying the position of the inflection point (i.e. point with the highest gradient). The GPS method is specifically aimed at determining rotation periods of low-activity stars like the Sun. We applied the GPS method to Sun-like stars observed by the Kepler telescope. We separately considered two stellar samples: one with near-solar rotation periods (24-27.4d) and broad range of effective temperatures (5000-6000K), another with near-solar effective temperatures (5700-5900K) and broad range of rotation periods (15-40d). We show that the GPS method returns precise values of stellar rotation periods. Furthermore, it allows us to constrain the ratio between facular and spot areas of active regions at the moment of their emergence. We show that relative facular area decreases with stellar rotation rate. Our results suggest that the GPS method can be successfully applied to retrieve periods of stars with both regular and non-regular light curves.
- ID:
- ivo://archive.stsci.edu/fuse
- Title:
- Far Ultraviolet Spectroscopic Explorer
- Short Name:
- FUSE
- Date:
- 22 Jul 2020 21:29:31
- Publisher:
- Space Telescope Science Institute Archive
- Description:
- The Far Ultraviolet Spectroscopic Explorer (FUSE), launched on June 24, 1999, covers the 905-1187 Å spectral region and will obtain high resolution spectra of hot and cool stars, AGNs, supernova remnants, planetary nebulae, solar system objects as well as perform detailed studies of the interstellar medium. FUSE will be able to observe sources 10 000 times fainter than Copernicus, an early FUV mission, and has superior resolving power than the Hopkins Ultraviolet Telescope (HUT) and the Berkeley Spectrograph (BEFS) and the Tübingen Echelle Spectrograph (TUES) of the Orbiting Retrievable Far and Extreme Ultraviolet Spectrometers (ORFEUS). FUSE was planned for a 3 year lifetime with funding for an additional 2 years expected.
- ID:
- ivo://CDS.VizieR/J/ApJ/682/1205
- Title:
- Fast transients in the Fornax cluster
- Short Name:
- J/ApJ/682/1205
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The luminosity gap between novae (M_R_<=-10) and supernovae (M_R_>=-14) has been well known since the pioneering research of Zwicky and Hubble. Nearby galaxy clusters and concentrations offer an excellent opportunity to search for explosions brighter than classical novae and fainter than supernovae. Here we present the results of a B-band survey of 23 member galaxies of the Fornax Cluster, performed at the Las Campanas 2.5m Irenee du Pont telescope. Observations with a cadence of 32 minutes discovered no genuine fast transient to a limiting absolute magnitude of M_B_=-9.3mag. We provide a detailed assessment of the transient detection efficiency and the resulting upper limits on the event rate as function of peak magnitude. Further, we discuss the discoveries of five previously unknown foreground variables which we identified as two flare stars, two W UMa-type eclipsing binaries and a candidate {delta} Scuti/SX Phe star.
- ID:
- ivo://CDS.VizieR/J/A+A/312/111
- Title:
- [Fe/H] from RR Lyrae light curves
- Short Name:
- J/A+A/312/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an accurate and robust method for the calculation of [Fe/H] from the light curves of RRab stars. The method introduces a considerable improvement relative to our previously published formulae. First of all, it uses an improved and extended data base for the light curves and more accurate, very recent iron abundances. Secondly, the new data base makes it possible to show that the basic relation between [Fe/H] and the Fourier parameters is linear and contains only the period and one of the Fourier phases, most importantly {phi}_31_. Last but not least, we derive interrelations among the Fourier parameters which help us to filter out peculiar stars where more caution is needed in accepting the calculated abundance. The applicability of the method is demonstrated on independent samples of globular cluster stars. Peculiarities encountered in Blazhko variables and in some other cases are also discussed. The Fourier decomposition is defined by the formula: V(t) = A0 + A1*sin(2*pi/P*(t-t0)+phi1) + A2*sin(2*pi*2/P*(t-t0)+phi2) +... + A15*sin(2*pi*15/P*(t-t0)+phi15) V(t) -- light curve in Johnson V P -- period t0 -- Epoch = 2400000.0
- ID:
- ivo://CDS.VizieR/J/MNRAS/434/2418
- Title:
- [Fe/H] of short-period Galactic Cepheids
- Short Name:
- J/MNRAS/434/2418
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the study of the metallicity dependence of the Fourier amplitude ratios R_21_ and R_31_ for the light curves of short-period Galactic classical Cepheids in B, V, R_C_ and I_C_ bands. Based on the available photometric and spectroscopic data, we determined the relations between the atmospheric iron abundance, [Fe/H], and the Fourier parameters. Using these relations we calculated the photometric [Fe/H] values of all programme Cepheids with an average accuracy of +/-0.15dex. No spectroscopic iron abundance was known before for 14 of these stars. These empirical results provide an alternate method to determine the iron abundance of classical Cepheids too faint for spectroscopic observations. We also checked whether the metal-poor Cepheids of both Magellanic Clouds follow the same relationships, and a good agreement was found.
- ID:
- ivo://CDS.VizieR/J/A+A/381/507
- Title:
- Fe II emission lines of RR Tel
- Short Name:
- J/A+A/381/507
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Files table1.dat and table2.dat contain the permitted and forbidden Fe II emission lines respectively which have been selected from the optical spectrum of RR Tel between 3180 and 9455{AA}. The spectrum was observed by Crawford et al. (1999, Cat. <J/A+AS/139/135>) whose corrected line fluxes and velocity widths we took for further analysis in this work. In the tables there are also values characteristic for the corresponding multiplets and lines such as multiplet numbers, term designations, level excitation potentials and quantum numbers J. The log functions of gf's, line fluxes and wavelengths are relevant for the SAC curves.
- ID:
- ivo://CDS.VizieR/J/AZh/91/299
- Title:
- FF Aql BV light curves
- Short Name:
- J/AZh/91/299
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photographic plates of the Harvard Observatory stacks have been used to obtain 1261 brightness estimates for the low-amplitude Cepheid FF Aql (P=4.47 days). Combined with published visual, photoelectric, and CCD observations, these data enable the construction of an O-C diagram spanning 122 years. The resulting O-C diagram is parabola-shaped, enabling the determination of quadratic brightness elements for the first time. The evolutionary rate of increase of the period, dP/dt=0.072+/-0.011s/year, is in agreement with theoretical computations for the third crossing of the instability strip. The available data, reduced using the technique of by Eddington and Plakidis, reveal the presence of small, random period fluctuations, {epsilon}=0.0061d+/-0.0044d, that do not distort the evolutionary trend of the O-C residuals.
- ID:
- ivo://CDS.VizieR/J/PAZh/29/858
- Title:
- FG Sagittae: new observations
- Short Name:
- J/PAZh/29/858
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In 1999-2002 the BVRI photometric and spectroscopic observations of FG Sge were made. The star has been in a new R CrB photometric phase since 1992.
- ID:
- ivo://CDS.VizieR/J/A+A/338/581
- Title:
- Field 3 Palomar-Groningen survey. II.
- Short Name:
- J/A+A/338/581
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Near-infrared photometry (JHKL'M) was obtained for 78 semiregular variables (SRVs) in field #3 of the Palomar-Groningen survey (PG3, l=0{deg}, b=-10{deg}). Together with a sample of Miras in this field a comparison is made with a sample of field SRVs and Miras. The PG3 SRVs form a sequence (period-luminosity & period-colour) with the PG3 Miras, in which the SRVs are the short period extension to the Miras. The field and PG3 Miras follow the same P/(J-K)_0_ relation, while this is not the case for the field and PG3 SRVs. Both the PG3 SRVs and Miras follow the Sgr I period-luminosity relation adopted from Glass et al. (1995MNRAS.273..383G). They are likely pulsating in the fundamental mode and have metallicities spanning the range from intermediate to approximately solar.
