- ID:
- ivo://CDS.VizieR/J/AZh/87/1087
- Title:
- New variable stars in 66 Oph field
- Short Name:
- J/AZh/87/1087
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the course of a program to digitize the astronomical plates of the Sternberg Astronomical Institute's plate stacks, we are developing algorithms for searching for new variable stars and studying them using digitized photographic plates. We have discovered and studied 480 new variable stars in a 10{deg}x10{deg} field of view centered on 66 Ophiuchi. The digitized plate negatives used are from the 40-cm astrograph, and are 30x30cm in size. These stars include three new Cepheids of the Galaxy's spherical component, 157 eclipsing binaries, 11 high-amplitude {delta} Scuti stars (HADSs), 144 RR Lyrae stars, 110 irregular variables (109 LB and one white star), and 55 semi-regular red variables.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+AS/49/715
- Title:
- New variable stars in Sgr B
- Short Name:
- J/A+AS/49/715
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 621 new variable stars have been detected on plates obtained with the Schmidt telescopes of the Mount Palomar Observatory (1968) and of the European Southern Observatory (1976-1980). The astrometric measurements (ESO-CERN) and the photometrical ones (CDCA) which have followed the detection the variable stars (Observatoire de Lyon) have led to determine the parameters {alpha}, {delta}, l, b, R(Max), R(Min), {delta}m. So we notice that: - 379 variable stars have an amplitude of variation in magnitude between 0.5 and 2.0 (delm/N histogram). -The number of variable stars strongly decreases towards the great amplitudes. -The surface density of variable stars by square degree in this central galactic direction increases from 2 to 21 in the explored field of 5.5degx5.5deg size.
- ID:
- ivo://CDS.VizieR/J/MNRAS/482/3058
- Title:
- New variable stars towards Galactic Bulge
- Short Name:
- J/MNRAS/482/3058
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detection of 3714 variable stars towards the Galactic bulge, including 2521 previously uncatalogued variables, using time-series photometry extracted from data obtained with the VIMOS imager at the Very Large Telescope. Observations of the Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS) field in the Galactic Bulge were taken over 2yr between March and October at a cadence of ~4d, enabling the detection of variables with periods up to ~100d. Many of these were already known, but we detected a significant number of new variables, including 11 Cepheids, a further 88 potential Cepheid candidates, and many contact binaries. Here we publish the catalogue of the new variables, containing coordinates, mean magnitudes as well as periods and classification; full light curves for these variables are also made available electronically.
- ID:
- ivo://CDS.VizieR/J/A+A/627/A2
- Title:
- New V-band photometry of Cyg OB2 5 (V729 Cyg)
- Short Name:
- J/A+A/627/A2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Cyg OB2 #5 system is thought to consist of a short-period (6.6d) eclipsing massive binary associated with an OB-star orbiting it with a period of ~6.7yr, themselves orbited by a distant early B-star (with thousands of years period). However, while the inner binary has been studied many times, information is missing on the other stars, in particular the third one whose presence was indirectly postulated from recurrent modulations in the radio domain. Besides, to this date, the X-ray lightcurve could not be fully interpreted, e.g. in the framework of colliding-wind emission linked to one of the systems. We obtained new optical and X-ray observations of Cyg OB2 #5, which we combined to archival data. We performed a thorough and homogeneous investigation of all available data, notably revisiting the times of primary minimum in photometry. In the X-ray domain, XMM-Newton provides scattered exposures over ~5000d whilst Swift provides a nearly continuous monitoring for the last couple of years. Though the X-ray lightcurve reveals clear variability, no significant period can be found hence the high-energy emission cannot be explained solely in terms of colliding winds varying along either the short or intermediate orbits. The optical data reveal for the first time clear signs of reflex motion: the photometry indicates the presence of a 2366d (i.e. 6.5yr) period while the associated radial velocity changes are detected at the 3{sigma} level in the systemic velocity of the HeII 4686 emission line. With the revised period, the radio lightcurve is interpreted consistently in terms of a wind interaction between the inner binary and the tertiary star. From the optical and radio data, we derive constraints on the physical properties of the tertiary star and its orbit.
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/2676
- Title:
- New white dwarf pulsators for TESS
- Short Name:
- J/MNRAS/478/2676
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of our survey searching for new white dwarf pulsators for observations by the TESS space telescope. We collected photometric time-series data on 14 white dwarf variable candidates at Konkoly Observatory, and found two new bright ZZ Ceti stars, namely EGGR 120 and WD 1310+583. We performed a Fourier analysis of the datasets. In the case of EGGR 120, which was observed on one night only, we found one significant frequency at 1332uHz with 2.3mmag amplitude. We successfully observed WD 1310+583 on eight nights, and determined 17 significant frequencies in the whole dataset. Seven of them seem to be independent pulsation modes between 634 and 2740uHz, and we performed preliminary asteroseismic investigations of the star utilizing six of these periods. We also identified three new light variables on the fields of white dwarf candidates: an eclipsing binary, a candidate delta Scuti/beta Cephei and a candidate W UMa-type star.
- ID:
- ivo://CDS.VizieR/J/A+A/629/A3
- Title:
- NGC1326A, 1425 and 4548 supergiants VI mags
- Short Name:
- J/A+A/629/A3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Studies on the massive star population in galaxies beyond the Local Group are the key to understand the link between their numbers and modes of star formation in different environments. We present the analysis of the massive star population of the galaxies NGC1326A, NGC 1425 and NGC 4548 using archival Hubble Space Telescope Wide Field Planetary Camera 2 images in the F555W and F814W filters. Through high precision point spread function fitting photometry for all sources in the three fields we identified 7640 candidate blue supergiants, 2314 candidate yellow supergiants, and 4270 candidate red supergiants. We provide an estimation the ratio of blue to red supergiants for each field as a function of galactocentric radius. Using Modules for Experiments in Stellar Astrophysics (MESA) at solar metallicity, we defined the luminosity function and estimated the star formation history of each galaxy. We carried out a variability search in the V and I filters using three variability indexes: the median absolute deviation, the interquartile range, and the inverse von-Neumann ratio. This analysis yielded 243 new variable candidates with absolute magnitudes ranging from M_V_=-4 to -10mag. We classified the variable stars based on their absolute magnitude and their position on the color-magnitude diagram using the MESA evolutionary tracks at solar metallicity. Our analysis yielded 8 candidate variable blue supergiants, 12 candidate variable yellow supergiants, 21 candidate variable red supergiants, and 4 candidate periodic variables.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/2489
- Title:
- NGC 6401 bulge variable stars
- Short Name:
- J/MNRAS/465/2489
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of variable stars in globular cluster NGC 6401. The cluster is only 5.3{deg} away from the Galactic Centre and suffers from strong differential reddening. The photometric precision afforded us by difference image analysis resulted in improved sensitivity to variability in formerly inaccessible interior regions of the cluster. We find 23 RRab and 11 RRc stars within one cluster radius (2.4-arcmin), for which we provide coordinates, finder-charts and time series photometry. Through Fourier decomposition of the RR Lyrae star light curves we derive a mean metallicity of [Fe/H]UVES=-1.13+/-0.06 ([Fe/H]ZW=-1.25+/-0.06), and a distance of d~6.35+/-0.81kpc. Using the RR Lyrae population, we also determine that NGC 6401 is an Oosterhoff type I cluster.
- ID:
- ivo://CDS.VizieR/J/MNRAS/421/2998
- Title:
- NGC 6822 Cepheids JHKs light curves
- Short Name:
- J/MNRAS/421/2998
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent estimates of the Cepheid distance modulus of NGC 6822 differ by 0.18mag. To investigate this we present new multi-epoch JHKs photometry of classical Cepheids in the central region of NGC 6822 and show that there is a zero-point difference from earlier work. These data together with optical and mid-infrared observations from the literature are used to derive estimates of the distance modulus of NGC 6822. A best value of 23.40mag is adopted, based on a Large Magellanic Cloud (LMC) distance modulus of 18.50mag. The standard error of this quantity is ~0.05mag. We show that to derive consistent moduli from Cepheid observations at different wavelengths, it is necessary that the fiducial LMC period-luminosity relations at these wavelengths should refer to the same subsample of stars. Such a set is provided. A distance modulus based on RR Lyrae variables agrees with the Cepheid result.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A16
- Title:
- NGC 6774 cool stars rotation periods
- Short Name:
- J/A+A/644/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gyrochronology allows the derivation of ages for cool main sequence stars based on their observed rotation periods and masses, or a suitable proxy thereof. It is increasingly well-explored for FGK stars, but requires further measurements for older ages and K-M-type stars. We study the 2.7Gyr-old open cluster Ruprecht 147 to compare it with the previously-studied, but far more distant, NGC 6819 cluster, and especially to measure cooler stars than was previously possible there. We constructed an inclusive list of 102 cluster members from prior work, including Gaia DR2, and for which light curves were also obtained during Campaign 7 of the Kepler/K2 space mission. We placed them in the cluster color-magnitude diagram and checked the related information against appropriate isochrones. The light curves were then corrected for data systematics using Principal Component Analysis on all observed K2 C07 stars and subsequently subjected to periodicity analysis. Periodic signals are found for 32 stars, 21 of which are considered to be both highly reliable and to represent single, or effectively single, Ru 147 stars. These stars cover the spectral types from late-F to mid-M stars, and they have periods ranging from 6d-33d, allowing for a comparison of Ruprecht 147 to both other open clusters and to models of rotational spindown. The derived rotation periods connect reasonably to, overlap with, and extend to lower masses the known rotation period distribution of the 2.5 Gyr-old cluster NGC 6819. The data confirm that cool stars lie on a single surface in rotation period-mass-age space, and they simultaneously challenge its commonly assumed shape. The shape at the low mass region of the color-period diagram at the age of Ru 147 favors a recently-proposed model which requires a third mass-dependent timescale in addition to the two timescales required by a former model, suggesting that a third physical process is required to model rotating stars effectively.
- ID:
- ivo://CDS.VizieR/J/AJ/146/57
- Title:
- NGC 6402. I. BV photometry
- Short Name:
- J/AJ/146/57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present BV photometry of the Galactic globular cluster NGC 6402 (M14), based on 65 V frames and 67 B frames, reaching two magnitudes below the turnoff level. This represents, to the best of our knowledge, the deepest color-magnitude diagram (CMD) of NGC 6402 available in the literature. Statistical decontamination of field stars as well as differential reddening corrections are performed in order to derive a precise ridgeline and hence physical parameters of the cluster. We discuss previous attempts at deriving a reddening value for the cluster, and argue in favor of a value E(B-V)=0.57+/-0.02, which is significantly higher than indicated by either the Burstein & Heiles or Schlegel et al. (corrected according to Bonifacio et al.) interstellar dust maps. Differential reddening across the face of the cluster, which we find to be present at the level of {Delta}E(B-V){approx}0.17mag, is taken into account in our analysis. We measure several metallicity indicators based on the position of the red giant branch (RGB) in the cluster CMD. These give a metallicity of [Fe/H]=-1.38+/-0.07 on the Zinn & West scale and [Fe/H]=-1.28+/-0.08 on the new Carretta et al. (UVES) scale. We also provide measurements of other important photometric parameters for this cluster, including the position of the RGB luminosity function "bump" and the horizontal branch morphology. We compare the NGC 6402 ridgeline with that of NGC 5904 (M5) derived by Sandquist et al., and find evidence that NGC 6402 and M5 have approximately the same age to within the uncertainties, although the possibility that M14 may be slightly older cannot be ruled out.
