In the recent IBVS 5633, Roslund et al. give a list of new red variable stars. The work evidently was done in the early 1970s, but no effort was made to match the star-list with recent data available from modern on-line resources in this late publication. Johnson R magnitudes at maximum are shown for all stars and spectral classifications for about half. The authors warn that the magnitudes could have a systematic error, such that they are perhaps a magnitude too bright overall. Similarly, the coordinates, given to arcsecond precision, are noted as being poorly determined with "a simple, unpretentious plate-measuring machine of unproven accuracy." I confirm here both of these problems. I have gone through the list to recover the stars in modern catalogues. I matched the source-list in the Strasbourg VizieR utility against UCAC2 and 2MASS, searching a 20" radius and _assuming_ the brightest red star in the region is the variable (typical J-K>>1.0). There are no identification charts published, so misidentifications are possible. However, the candidates are all very similar in near-IR brightness (commonly 7<J<10), so it seemed the choices were limited. The original positions are indeed semi-accurate, being typically 5"-15" in error. I show improved coordinates in the table below. Nearly all thepositions come from 2MASS, but a few appear in UCAC2. That so few stars are present in UCAC2 is a first suggestion that the Roslund et al red magnitudes are much too bright compared to the standard system (either Johnson or Cousins R). I matched the corrected positions again in VizieR with GSC-2.2, USNO-B1.0, and the DENIS catalogue to obtain at least a "representative" V (or 'mv') magnitude, sometimes inferred from adjacent colors. Most of these come from the short-V plate data provided in GSC-2.2, where my experience with the same sorts of stars suggests the zero-point and scale are under good control. It was also easy to compare at the same time the Roslund R(max) magnitudes with the photo-red and I-band data listed in the three surveys just mentioned. This indicates the Roslund 'R' is at least one and more likely _two_ full magnitudes too bright even accounting for the large amplitudes of the variables---the zero-point is nearly that of the USNO-B1.0 or DENIS I-band magnitudes, rather than R. Finally, I matched the stars with the MSX6C and IRAS catalogues and also GCVS v4.2. Most stars have an MSX link, but probably the bright IR background close to the galactic center precluded many IRAS detections. I also searched each position in SIMBAD (3' search radius): the stars with Terzan links are shown, but the rest of the stars are not present in the database. Please note the following: where no reasonably bright red star appeared near the Roslund position on 2MASS J-band images, I used the identifications with the Terzan survey of the same region to obtain improved positions. This allowed all but one star to be recovered unambiguously.
Based on an extensive spectral study of a photometrically confirmed sample of Mira variables, we find a relationship between the relative Balmer emission-line strengths and spectral temperatures of O-rich Mira stars. The F_H{delta}_/F_H{gamma}_ flux ratio increases from less than unity to five as stars cool down from M0 to M10, which is likely driven by increasing TiO absorption above the deepest shock-emitting regions. We also discuss the relationship between the equivalent widths of the Balmer emission lines and the photometric luminosity phase of our Mira sample stars. Using our 291 Mira spectra as templates for reference, 191 Mira candidates are newly identified from the LAMOST DR4 catalog. We summarize the criteria adopted to select Mira candidates based on emission-line indices and molecular absorption bands. This enlarged spectral sample of Mira variables has the potential to contribute significantly to our knowledge of the optical properties of Mira stars and will facilitate further studies of these late-type, long-period variables.
Effective temperatures are determined for a sample of 165 oxygen-rich Miras using indices related to molecular band strength of titanium oxide and vanadium oxide. Using a theoretical evolutionary track on AGB, absolute bolometric magnitudes are computed. Apparent bolometric magnitudes are determined from narrow-band photometry observations. They are used to calibrate distances.
We present V, I photometry of the loose star cluster NGC 6749, and for the first time colour-magnitude diagrams are provided. We confirm that it is a globular cluster and its blue horizontal branch indicates that it is metal-poor. We derive a reddening of E(B-V)=1.39+/-0.04 and a distance from the Sun d_{sun}_=7.3+/-0.9kpc (assuming a total-to-selective absorption R=3.4). The cluster is projected very close to the Galactic plane, and the derived distance implies a Galactic coordinate Z~-300pc. It is thus a halo globular cluster located close to the disc plane. We also discuss the properties of 78 newly discovered long-period variable stars, of which 75 are Miras, projected within 1{deg} of the cluster centre. The variables do not appear to be associated with the globular cluster. From their periods, most of them belong to the metal-rich disc or bulge stellar populations.
The 222000 I-band light curves of variable stars detected by the OGLE-II survey in the direction of the Galactic Bulge have been fitted and also correlated with the DENIS and 2MASS all-sky release databases and with lists of known objects. Light-curves and the results of the light-curve fitting (periods and amplitudes) and DENIS and 2MASS data are presented for 2691 objects with I-band semi-amplitude larger than 0.45 magnitude, corresponding to classical Mira variables.
Good distance indicators are needed in studies of the galactic structure. Pulsating variables can be used, but the problem is to find a homogeneous sample obeying a period-luminosity relation with low scatter. In this paper, we show how such a sample can be produced using the Terzan catalogue of Variables and available Schmidt plates. We have selected 150 large amplitude variables discovered by Terzan in a field of 25 sq degrees near the Galactic Centre. A set of 22 red plates was scanned with the MAMA machine, providing time series for all the variables. The times series were analysed using both the periodogram and Renson's method. Periods could be derived for 122 stars of the sample showing clearly that most of these objects are Miras. As a conclusion we show that with some infrared photometry, these Miras could be used as good distance indicators in this region.
We have studied the long-term variations of Mira type variables observed with Robotic Optical Transient Search Experiment telescope (ROTSE-IIId) between 2004 and 2009 located at TUBITAK National Observatory (TUG) in Antalya, Turkey. The actual pulsation periods, variability amplitudes, epochs of maximums and light curves of selected 70 Mira type variables already defined in the SIMBAD database were investigated. In these variables, 17 periods are identified for the first time
This report describes 300 new variable stars (MisV0001-MisV0300) discovered in the course of the MISAO Project The goal of the MISAO Project, standing for Multitudinous Image-based Sky-survey and Accumulative Observations, is to discover new celestial objects or to obtain photometric data from multitudinous astronomical images. The details are described on the MISAO Project Home Page: http://www.info.waseda.ac.jp/muraoka/members/seiichi/misao/
We revisit the photometric variability of stars in the M67 field using Kepler/K2-Campaign-5 light curves. In our previous work (Gonzalez, 2016, Cat. J/MNRAS/459/1060), we limited the search area around M67 to that of a recent ground-based study. In the present work, we expand the search area and apply a more rigorous period-finding algorithm to determine the rotation periods of 98 main-sequence cluster members from the same data. In addition, we derive periods of 40 stars from the K2SC detrended light curves. We determine the mean period of single sun-like main-sequence cluster members to be 29.6+/-0.6d. Assuming the periods correspond to stellar rotation, the corresponding mean gyrochronological (gyro-) age is 5.4+/-0.2Gyr.
In the third paper of this series we continue the exploitation of Kepler/K2 data in dense stellar fields using our PSF-based method. This work is focused on a ~720-arcmin^2^ region centred on the Solar-metallicity and Solar-age open cluster M 67. We extracted light curves for all detectable sources in the Kepler channels 13 and 14, adopting our technique based on the usage of a high-angular-resolution input catalogue and target-neighbour subtraction. We detrended light curves for systematic errors, and searched for variables and exoplanets using several tools. We found 451 variables, of which 299 are new detection. Three planetary candidates were detected by our pipeline in this field. Raw and detrended light curves, catalogues, and K2 stacked images used in this work will be released to the community.
