Search

Start Over Subject galaxies Rights public
3951. Variable stars in Her dwarf galaxy
ID:
ivo://CDS.VizieR/J/ApJ/756/121
Title:
Variable stars in Her dwarf galaxy
Short Name:
J/ApJ/756/121
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first time-series study of the ultra-faint dwarf galaxy Hercules. Using a variety of telescope/instrument facilities we secured about 50 V and 80 B epochs. These data allowed us to detect and characterize 10 pulsating variable stars in Hercules. Our final sample includes six fundamental-mode (ab-type) and three first-overtone (c-type) RR Lyrae stars, and one Anomalous Cepheid. The average period of the ab-type RR Lyrae stars, <P_ab_>=0.68days ({sigma}=0.03days), places Hercules in the Oosterhoff II group, as found for almost the totality of the ultra-faint dwarf galaxies investigated so far for variability. The RR Lyrae stars were used to obtain independent estimates of the metallicity, reddening, and distance to Hercules, for which we find [Fe/H]=-2.30+/-0.15dex, E(B-V)=0.09+/-0.02mag, and (m-M)_0_=20.6+/-0.1mag, in good agreement with the literature values. We have obtained a V, B-V color-magnitude diagram (CMD) of Hercules that reaches V~25mag and extends beyond the galaxy's half-light radius over a total area of 40'x36'. The CMD and the RR Lyrae stars indicate the presence of a population as old and metal-poor as (at least) the Galactic globular cluster M68.
3952. Variable stars in IC 1613
ID:
ivo://CDS.VizieR/J/A+A/367/759
Title:
Variable stars in IC 1613
Short Name:
J/A+A/367/759
Date:
21 Oct 2021
Publisher:
CDS
Description:
The nearby galaxies IC 1613 and NGC 6822 were observed over four years to detect short period Cepheids and to obtain good light curves for Fourier decomposition. The program was carried out with a relatively small telescope, the Dutch 0.9m at ESO-La Silla, and the observations were performed without filter (white light), or Wh-band. In this paper we present the results of the observations of Fields C and D in IC 1613 (3.8'x3.8' each). The analysis of the light curves of 3297 stars in the two fields has allowed the detection of 92 variable stars. A total of 34 Population I Cepheids have been found, while only 7 of these objects were previously known in these fields. Most of the stars have short periods and some of them are first overtone mode pulsators. Among the other variable stars there are one eclipsing binary and five W Vir candidates. A nova event was observed in Field D.
3953. Variable stars in Leo I dSph
ID:
ivo://CDS.VizieR/J/PASP/126/616
Title:
Variable stars in Leo I dSph
Short Name:
J/PASP/126/616
Date:
21 Oct 2021
Publisher:
CDS
Description:
From archival ground-based images of the Leo I dwarf spheroidal galaxy, we have identified and characterized the pulsation properties of 164 candidate RR Lyrae variables and 55 candidate anomalous and/or short-period Cepheids. We have also identified 19 candidate long-period variable stars and 13 other candidate variables whose physical nature is unclear, but due to the limitations of our observational material we are unable to estimate reliable periods for them.
3954. Variable stars in Logal Group galaxies. III.
ID:
ivo://CDS.VizieR/J/ApJ/842/60
Title:
Variable stars in Logal Group galaxies. III.
Short Name:
J/ApJ/842/60
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the discovery of 1568 RR Lyrae stars in three of the most luminous M31 satellites: And VII (573), NGC 147 (177), and NGC 185 (818). We use their properties to study the formation history of Local Group spiral haloes, and in particular, to infer about the nature of their possible building blocks by comparison with available data for RR Lyrae stars in the halo and in a sample of satellites of M31 and the Milky Way. We find that the brightest satellites and the halos of both galaxies host a number of High Amplitude Short Period (HASP) RR Lyrae variable stars, which are missing in the faintest satellites. HASP variable stars have been shown by Fiorentino+ (2015ApJ...798L..12F) to be tracers of a population of stars as metal-rich as [Fe/H]~-1.5 and older than ~10Gyr. This suggests that the metal-rich M31 and MW halo component, which manifests through the HASP phenomenon, comes from massive dwarf galaxy building blocks, as the low-mass dwarfs did not chemically enrich fast enough to produce them. All detected variable stars are new discoveries; in particular, this work presents the first detections of RR Lyrae stars in And VII. Moreover, a number of candidate Anomalous Cepheids, and binary and long-period variable stars have been detected. We provide pulsation properties (period, amplitude, mean magnitude), light curves, and time series photometry for all of the variable stars in the three galaxies.
3955. Variable stars in M31 and M33. V. HR diagram
ID:
ivo://CDS.VizieR/J/ApJ/844/40
Title:
Variable stars in M31 and M33. V. HR diagram
Short Name:
J/ApJ/844/40
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present HR diagrams for the massive star populations in M31 and M33, including several different types of emission-line stars: the confirmed luminous blue variables (LBVs), candidate LBVs, B[e] supergiants, and the warm hypergiants. We estimate their apparent temperatures and luminosities for comparison with their respective massive star populations and evaluate the possible relationships of these different classes of evolved, massive stars, and their evolutionary state. Several of the LBV candidates lie near the LBV/S Dor instability strip that supports their classification. Most of the B[e] supergiants, however, are less luminous than the LBVs. Many are very dusty with the infrared flux contributing one-third or more to their total flux. They are also relatively isolated from other luminous OB stars. Overall, their spatial distribution suggests a more evolved state. Some may be post-RSGs (red supergiants) like the warm hypergiants, and there may be more than one path to becoming a B[e] star. There are sufficient differences in the spectra, luminosities, spatial distribution, and the presence or lack of dust between the LBVs and B[e] supergiants to conclude that one group does not evolve into the other.
3956. Variable stars in Sculptor dSph
ID:
ivo://CDS.VizieR/J/MNRAS/462/4349
Title:
Variable stars in Sculptor dSph
Short Name:
J/MNRAS/462/4349
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the identification of 634 variable stars in the Milky Way dwarf spheroidal (dSph) satellite Sculptor based on archival ground-based optical observations spanning ~24yr and covering ~2.5deg^2^. We employed the same methodologies as the 'Homogeneous Photometry' series published by Stetson. In particular, we have identified and characterized one of the largest (536) RR Lyrae samples so far in a Milky Way dSph satellite. We have also detected four Anomalous Cepheids, 23 SX Phoenicis stars, five eclipsing binaries, three field variable stars, three peculiar variable stars located above the horizontal branch - near to the locus of BL Herculis - that we are unable to classify properly. Additionally, we identify 37 long period variables plus 23 probable variable stars, for which the current data do not allow us to determine the period. We report positions and finding charts for all the variable stars, and basic properties (period, amplitude, mean magnitude) and light curves for 574 of them. We discuss the properties of the RR Lyrae stars in the Bailey diagram, which supports the coexistence of subpopulations with different chemical compositions. We estimate the mean mass of Anomalous Cepheids (~1.5M_{sun}_) and SX Phoenicis stars (~1M_{sun}_). We discuss in detail the nature of the former. The connections between the properties of the different families of variable stars are discussed in the context of the star formation history of the Sculptor dSph galaxy.
3957. Variable stars in the field of Andromeda XXV. III.
ID:
ivo://CDS.VizieR/J/ApJ/829/26
Title:
Variable stars in the field of Andromeda XXV. III.
Short Name:
J/ApJ/829/26
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present B and V time series photometry of Andromeda XXV, the third galaxy in our program on the Andromeda's satellites, which we have imaged with the Large Binocular Cameras of the Large Binocular Telescope. The field of Andromeda XXV is found to contain 62 variable stars, for which we present light curves and characteristics of the light variation (period, amplitudes, variability type, mean magnitudes, etc.). The sample includes 57 RR Lyrae variables (46 fundamental-mode-RRab, and 11 first-overtone-RRc, pulsators), 3 anomalous Cepheids, 1 eclipsing binary system, and 1 unclassified variable. The average period of the RRab stars (<Pab>=0.60 {sigma}=0.04d) and the period-amplitude diagram place Andromeda XXV in the class of the Oosterhoff-Intermediate objects. From the average luminosity of the RR Lyrae stars we derive for the galaxy a distance modulus of (m-M)_0_=24.63+/-0.17mag. The color-magnitude diagram reveals the presence in Andromeda XXV of a single, metal-poor ([Fe/H]=-1.8dex) stellar population as old as ~10-12Gyr, traced by a conspicuous red giant branch and the large population of RR Lyrae stars. We discovered a spherically shaped high density of stars near the galaxy center. This structure appears to be at a distance consistent with Andromeda XXV and we suggest it could either be a star cluster or the nucleus of Andromeda XXV. We provide a summary and compare the number and characteristics of the pulsating stars in the M31 satellites analyzed so far for variability.
3958. Variable Stars in the Sculptor dwarf galaxy
ID:
ivo://CDS.VizieR/J/A+AS/112/407
Title:
Variable Stars in the Sculptor dwarf galaxy
Short Name:
J/A+AS/112/407
Date:
21 Oct 2021
Publisher:
CDS
Description:
The central area of the Sculptor dwarf galaxy was surveyed for variable stars as a side-program of the OGLE project. Light curves in the V band were obtained for 226 RR Lyr stars and for 3 anomalous cepheids. The data on RR Lyr variables in four nearby dwarf galaxies are summarized and discussed briefly.
3959. Variable stars of Draco dSph
ID:
ivo://CDS.VizieR/J/AJ/136/1921
Title:
Variable stars of Draco dSph
Short Name:
J/AJ/136/1921
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a CCD survey of variable stars in the Draco dwarf spheroidal galaxy. This survey, which has the largest areal coverage since the original variable star survey by Baade & Swope (1961AJ.....66..300B), includes photometry for 270 RR Lyrae (RRL) stars, 9 anomalous Cepheids (ACs), 2 eclipsing binaries, and 12 slow, irregular red variables, as well as 30 background QSOs. Twenty-six probable double-mode RRL stars were identified. Observed parameters, including mean V and I magnitudes, V amplitudes, and periods, have been derived.
3960. V-band, 5100{AA} and broad emission LCs of Mrk 79
ID:
ivo://CDS.VizieR/J/ApJ/887/135
Title:
V-band, 5100{AA} and broad emission LCs of Mrk 79
Short Name:
J/ApJ/887/135
Date:
21 Oct 2021
Publisher:
CDS
Description:
We developed a spectroscopic monitoring project to investigate the kinematics of the broad-line region (BLR) in active galactic nuclei (AGNs) with ultrafast outflows (UFOs). Mrk 79 is a radio-quiet AGN with UFOs and warm absorbers and has been monitored by three reverberation mapping (RM) campaigns, but its BLR kinematics are not yet understood. In this paper, we report the results from a new RM campaign of Mrk 79, which was undertaken with the Lijiang 2.4m telescope. Mrk 79 appears to come out the faint state, with the mean flux approximately a magnitude fainter than the historical record. We successfully measured the lags of the broad emission lines including H{beta}{lambda}4861, H{gamma}{lambda}4340, HeII{lambda}4686, and HeI{lambda}5876 with respect to the varying AGN continuum. Based on the broad H{beta}{lambda}4861 line, we measured a black hole mass of M_{bullet}_=5.13_-1.55_^+1.57^x10^7^M_{sun}_, and an estimated accretion rate of dM/dt_{bullet}_=(0.05+/-0.02)L_Edd_c^-2^, indicating that Mrk 79 is a sub-Eddington accretor. We found that Mrk 79 deviates from the canonical Radius-Luminosity relationship. The marginal blueshift of the broad HeII{lambda}4686 line detected from the rms spectrum indicates outflow of high- ionization gas. The velocity-resolved lag profiles of the broad H{gamma}{lambda}4340, H{beta}{lambda}4861, and HeI{lambda}5876 lines show similar signatures such that the largest lag occurs in the red wing of the lines and then the lag decreases to both sides. These signatures may suggest that the BLR of Keplerian motion probably exists as outflow gas motion. All findings including UFOs, warm absorbers, and the kinematics of high- and low-ionization BLR, may provide indirect evidence that the BLR of Mrk 79 probably originates from a disk wind.