Variability in the Massive Open Cluster NGC 1817 from K2: A Rich Population of Asteroseismic Red Clump, Eclipsing Binary, and Main-sequence Pulsating Stars

AbstractUsing the ASAS-3 photometry, we find the components of four eclipsing binary systems — V916 Cen, HD 101838, V4386 Sgr and HD 168050 — to be β Cephei-type pulsators. The first two systems are members of the young open cluster Stock 14. The pulsating stars are presumably the primary, more massive components in all these systems. The components are detached and for at least two systems, V916 Cen and HD 168050, we may suspect that they will appear to be double-lined spectroscopic ones. In consequence, these stars become very attractive targets for studying pulsations in β Cephei stars by means of asteroseismology.

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Pulsating stars in the open cluster NGC 1817

International Astronomical Union Colloquium ◽

10.1017/s0252921100010708 ◽

2004 ◽

Vol 193 ◽

pp. 242-246

Author(s):

T. Arentoft ◽

L.M. Freyhammer ◽

M.Y. Bouzid ◽

C. Sterken ◽

S. Frandsen

Keyword(s):

Open Cluster ◽

Variable Stars ◽

Eclipsing Binary ◽

Pulsating Stars ◽

Ccd Observations

AbstractWe report on new CCD observations of the open cluster NGC 1817, obtained as part of a program to search for pulsating stars in clusters. In a previous study, several δ Sct stars were found in NGC 1817 and our observations confirm that NGC 1817 is a special cluster, as we detected 19 variable stars. Twelve of these are most likely δ Sct stars of which 11 seem to be cluster members. One is also an eclipsing binary.

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Tidal Circularization Among the Close Binaries in M67

Symposium - International Astronomical Union ◽

10.1017/s0074180900122740 ◽

1992 ◽

Vol 151 ◽

pp. 471-472

Author(s):

David W. Latham ◽

Robert D. Mathieu ◽

Alejandra A. E. Milone ◽

Robert J. Davis

Keyword(s):

Main Sequence ◽

Open Cluster ◽

Radial Velocities ◽

Spectroscopic Binaries ◽

Close Binaries ◽

To Come ◽

Mirror Telescope

In 1971 Roger Griffin and Jim Gunn began monitoring the radial velocities of most of the members brighter than the main-sequence turnoff in the old open cluster M67, primarily using the 200-inch Hale Telescope. In 1982 the torch was passed to Dave Latham and Bob Mathieu, who began monitoring many of the same stars with the 1.5-meter Tillinghast Reflector and the Multiple-Mirror Telescope on Mt. Hopkins. We have successively combined these two sets of data, plus some additional CORAVEL velocities kindly provided by Michel Mayor, to obtain 20 years of time coverage (e.g. Mathieu et al. 1986). Among the stars brighter than magnitude V = 12.7 we have already published orbits for 22 spectroscopic binaries (Mathieu et al. 1990). At Mt. Hopkins an extension of this survey to many of the cluster members down to magnitude V = 15.5 has already yielded thirteen additional orbital solutions, with the promise of many more to come.

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V 3903 Sagitarii: A Main-Sequence (07V+09V) Detached Eclipsing Binary

International Astronomical Union Colloquium ◽

10.1017/s025292110001808x ◽

1993 ◽

Vol 137 ◽

pp. 371-373

Author(s):

L.P.R. Vaz ◽

N.C.S. Cunha ◽

E.F. Vieira ◽

M.L.M. Myrrha

Keyword(s):

Main Sequence ◽

Eclipsing Binary ◽

Spectroscopic Observations ◽

Photometric And Spectroscopic Observations ◽

Absolute Dimensions

AbstractPhotometric and spectroscopic observations of V3903 Sgr are analyzed, and absolute dimensions (masses and radii) are determined to a precision better then 3%.

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Abundance analysis of red clump stars in the old, inner disc, open cluster NGC 4337: a twin of NGC 752?

Astronomy and Astrophysics ◽

10.1051/0004-6361/201424443 ◽

2014 ◽

Vol 568 ◽

pp. A86 ◽

Cited By ~ 9

Author(s):

Giovanni Carraro ◽

Lorenzo Monaco ◽

Sandro Villanova

Keyword(s):

Open Cluster ◽

Red Clump

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Eclipsing spotted giant star with K2 and historical photometry

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834106 ◽

2018 ◽

Vol 620 ◽

pp. A189 ◽

Cited By ~ 3

Author(s):

K. Oláh ◽

S. Rappaport ◽

T. Borkovits ◽

T. Jacobs ◽

D. Latham ◽

...

Keyword(s):

Binary System ◽

Main Sequence ◽

Rapid Evolution ◽

Magnetic Activity ◽

Primary Component ◽

Physical Parameters ◽

Giant Star ◽

Eclipsing Binary ◽

Giant Stars ◽

Active Stars

Context. Stars can maintain their observable magnetic activity from the pre-main sequence (PMS) to the tip of the red giant branch. However, the number of known active giants is much lower than active stars on the main sequence (MS) since the stars spend only about 10% of their MS lifetime on the giant branch. Due to their rapid evolution it is difficult to estimate the stellar parameters of giant stars. A possibility for obtaining more reliable stellar parameters for an active giant arises when it is a member of an eclipsing binary system. Aims. We have discovered EPIC 211759736, an active spotted giant star in an eclipsing binary system during the Kepler K2 Campaign 5. The eclipsing nature allows us to much better constrain the stellar parameters than in most cases of active giant stars. Methods. We have combined the K2 data with archival HATNet, ASAS, and DASCH photometry, new spectroscopic radial velocity measurements, and a set of follow-up ground-based BVRCIC photometric observations, to find the binary system parameters as well as robust spot models for the giant at two different epochs. Results. We determined the physical parameters of both stellar components and provide a description of the rotational and long-term activity of the primary component. The temperatures and luminosities of both components were examined in the context of the Hertzsprung–Russell diagram. We find that both the primary and the secondary components deviate from the evolutionary tracks corresponding to their masses in the sense that the stars appear in the diagram at lower masses than their true masses. Conclusions. We further evaluate the proposition that traditional methods generally result in higher masses for active giants than what is indicated by stellar evolution tracks in the HR diagram. A possible reason for this discrepancy could be a strong magnetic field, since we see greater differences in more active stars.

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The McDonald Observatory search for pulsating sdA stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833279 ◽

2018 ◽

Vol 617 ◽

pp. A6 ◽

Cited By ~ 4

Author(s):

K. J. Bell ◽

I. Pelisoli ◽

S. O. Kepler ◽

W. R. Brown ◽

D. E. Winget ◽

...

Keyword(s):

Time Series ◽

White Dwarfs ◽

Main Sequence ◽

Pulsating Stars ◽

Blue Stragglers ◽

Rr Lyrae ◽

Stellar Pulsations ◽

Low Mass ◽

New Variables

Context. The nature of the recently identified “sdA” spectroscopic class of stars is not well understood. The thousands of known sdAs have H-dominated spectra, spectroscopic surface gravity values between main sequence stars and isolated white dwarfs, and effective temperatures below the lower limit for He-burning subdwarfs. Most are likely products of binary stellar evolution, whether extremely low-mass white dwarfs and their precursors or blue stragglers in the halo. Aims. Stellar eigenfrequencies revealed through time series photometry of pulsating stars sensitively probe stellar structural properties. The properties of pulsations exhibited by sdA stars would contribute substantially to our developing understanding of this class. Methods. We extend our photometric campaign to discover pulsating extremely low-mass white dwarfs from the McDonald Observatory to target sdA stars classified from SDSS spectra. We also obtain follow-up time series spectroscopy to search for binary signatures from four new pulsators. Results. Out of 23 sdA stars observed, we clearly detect stellar pulsations in 7. Dominant pulsation periods range from 4.6 min to 12.3 h, with most on timescales of approximately one hour. We argue specific classifications for some of the new variables, identifying both compact and likely main sequence dwarf pulsators, along with a candidate low-mass RR Lyrae star. Conclusions. With dominant pulsation periods spanning orders of magnitude, the pulsational evidence supports the emerging narrative that the sdA class consists of multiple stellar populations. Since multiple types of sdA exhibit stellar pulsations, follow-up asteroseismic analysis can be used to probe the precise evolutionary natures and stellar structures of these individual subpopulations.

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Spectroscopic Binaries in the Open Cluster M67

International Astronomical Union Colloquium ◽

10.1017/s025292110000628x ◽

1992 ◽

Vol 135 ◽

pp. 155-157 ◽

Cited By ~ 4

Author(s):

David W. Latham ◽

Robert D. Mathieu ◽

Alejandra A.E. Milone ◽

Robert J. Davis

Keyword(s):

Circular Orbit ◽

Main Sequence ◽

Open Cluster ◽

Radial Velocities ◽

Spectroscopic Binaries ◽

Eccentric Orbit ◽

Circular Orbits ◽

Blue Stragglers ◽

Short Period ◽

Blue Straggler

AbstractFor almost 400 members of M67 we have accumulated about 5,000 precise radial velocities. Already we have orbital solutions for more than 32 spectroscopic binaries in M67. Many of these orbits were derived by combining the Palomar and CfA observations, thus extending the time coverage to more than 20 years. The distribution of eccentricity versus period shows evidence for tidal circularization on the main sequence. The transition from circular orbits is fairly clean. Excluding the blue stragglers, the first eccentric orbit has a period of 11.0 days, while the last circular orbit has a period of 12.4 days. For longer periods the distribution of eccentricity is the same as for field stars. The blue straggler S1284 has an eccentric orbit despite its short period of 4.2 days.

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WIYN Open Cluster Study: Tidal Interactions in Solar-Type Binaries

Symposium - International Astronomical Union ◽

10.1017/s0074180900195506 ◽

2004 ◽

Vol 215 ◽

pp. 170-176

Author(s):

S. Meibom ◽

R. D. Mathieu

Keyword(s):

Binary Stars ◽

Main Sequence ◽

Open Cluster ◽

Current Data ◽

Close Binary ◽

Tidal Interactions ◽

Close Binary Stars ◽

Theoretical Predictions ◽

Solar Type ◽

Existing Data

We present an ongoing study on tidal interactions in late-type close binary stars. New results on tidal circularization are combined with existing data to test and constrain theoretical predictions of tidal circularization in the pre-main-sequence (PMS) phase and throughout the main-sequence phase of stellar evolution. Current data suggest that tidal circularization during the PMS phase sets the tidal cutoff period for binary populations younger than ~ 1 Gyr. Binary populations older than ~ 1 Gyr show increasing tidal cutoff periods with age, consistent with active main-sequence tidal circularization.

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Pulsation among TESS A and B stars and the Maia variables

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa670 ◽

2020 ◽

Vol 493 (4) ◽

pp. 5871-5879

Author(s):

L A Balona ◽

D Ozuyar

Keyword(s):

Main Sequence ◽

Large Fraction ◽

Single Mode ◽

Distinct Region ◽

Low Frequencies ◽

B Stars ◽

High Frequencies ◽

Pulsating Stars ◽

Scuti Stars

ABSTRACT Classification of over 50 000 TESS stars in sectors 1–18 has resulted in the detection of 766 pulsating main-sequence B stars as well as over 5000 δ Scuti, 2300 γ Doradus, and 114 roAp candidates. Whereas it has been assumed that high-frequency pulsations among B-type main-sequence stars are confined to the early B-type β Cephei stars, the observations indicate that high frequencies are to be found over the whole B-star range, eventually merging with δ Scuti stars. The cool B stars pulsating in high frequencies are called Maia variables. It is shown that Maia variables are not rapidly rotating and thus cannot be β Cephei pulsators that appear to have lower temperatures due to gravity darkening. In the region where β Cephei variables are found, the proportion of pulsating stars is larger and amplitudes are higher and a considerable fraction pulsate in a single mode and low rotation rate. There is no distinct region of slowly pulsating B stars (SPB stars). Stars pulsating solely in low frequencies are found among all B stars. At most, only one-third of B stars appear to pulsate. These results, as well as the fact that a large fraction of A and B stars show rotational modulation, indicate a need for a revision of current ideas regarding stars with radiative envelopes.

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