Empirical microlensing event rates predicted by a phenomenological model

Poleski, R.

doi:10.1093/mnras/stv2569

Cited by 74 publications

(70 citation statements)

References 12 publications

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“…First overtone models exhibit much faster (a factor of a few up to 10) higherṖ than fundamental mode models. This is consistent with first overtone pulsators exhibiting faster and more erratic period changes than fundamental mode Cepheids (Poleski 2008). Very long-period Cepheids, i.e., those which cross the IS only once (cf.…”

Section: Rates Of Period Changesupporting

confidence: 83%

“…For the SMC, we use 213 Cepheids with positive and 285 Cepheids with negativeṖ as listed in Pietrukowicz (2002). Poleski (2008) cautions thatṖ values derived from insufficiently long temporal baselines are not necessarily suitable for comparisons with stellar evolution models, since suchṖ values can be dominated by short-term fluctuations rather than secular evolution (see also Berdnikov et al 2000Berdnikov et al , 2009. Studies ofṖ over longer temporal baselines would be very useful for more accurate tests of stellar models.…”

Section: Rates Of Period Changementioning

confidence: 99%

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On the effect of rotation on populations of classical Cepheids

Anderson

Saio

Ekström

et al. 2016

A&A

172

257

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Classical Cepheid variable stars (from hereon: Cepheids) are high-sensitivity probes of stellar evolution and fundamental tracers of cosmic distances. While rotational mixing significantly affects the evolution of Cepheid progenitors (intermediate-mass stars), the impact of the resulting changes in stellar structure and composition on Cepheids and their pulsational properties is hitherto unknown. Here we present the first detailed pulsational instability analysis of stellar evolution models that include the effects of rotation, for both fundamental mode and first overtone pulsation. We employ Geneva evolution models spanning a three-dimensional grid in mass (1.7-15 M ), metallicity (Z = 0.014, 0.006, 0.002), and rotation (non-rotating, average & fast rotation). We determine (1) hot and cool instability strip (IS) boundaries taking into account the coupling between convection and pulsation; (2) pulsation periods; and (3) rates of period change. We investigate relations between period and (a) luminosity; (b) age; (c) radius; (d) temperature; (e) rate of period change; (f) mass; (g) the flux-weighted gravity-luminosity relation (FWGLR). We confront all predictions aside from those for age with observations, finding generally excellent agreement. We tabulate period-luminosity relations (PLRs) for several photometric passbands and investigate how the finite IS width, different IS crossings, metallicity, and rotation affect PLRs. We show that a Wesenheit index based on H, V, and I photometry is expected to have the smallest intrinsic PLR dispersion. We confirm that rotation resolves the Cepheid mass discrepancy. Period-age relations depend significantly on rotation, with rotation leading to older Cepheids, offering a straightforward explanation for evolved stars in binary systems that cannot be matched by conventional isochrones assuming a single age. We further show that Cepheids obey a tight FWGLR. Rotation is a fundamental property of stars that has important implications for the study of intermediate-mass stars, intermediate-age clusters, and classical Cepheid variable stars.

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Section: Rates Of Period Changesupporting

confidence: 83%

Section: Rates Of Period Changementioning

confidence: 99%

On the effect of rotation on populations of classical Cepheids

Anderson

Saio

Ekström

et al. 2016

A&A

172

257

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“…These stars typically have more sinusoidal-like light curves, for instance, Polaris and FF Aql (Neilson et al 2012a;Turner et al 2013a,b). Because of the shape of the light curve, determining the time of light minimum is more difficult than for a fundamental-mode Cepheid (Poleski 2008). A typical sinusoidal light curve is shown in Fig.…”

Section: Results For First-overtone Pulsationmentioning

confidence: 99%

Convection, granulation, and period jitter in classical Cepheids

Neilson¹,

Ignace²

2014

A&A

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Analyses of recent observations of the sole classical Cepheid in the Kepler field, V1154 Cygni, found random changes of about 30 min in the pulsation period. These period changes challenge standard theories of pulsation and evolution because the period change is nonsecular, and explaining this period jitter is necessary for understanding stellar evolution and the role of Cepheids as precise standard candles. We suggest that convection and convective hot spots can explain the observed period jitter. Convective hot spots alter the timing of flux maximum and minimum in the Cepheid light curve, hence change the measured pulsation period. We present a model of random hot spots that generate a localized flux excess that perturbs the Cepheid light curve and consequently the pulsation period, which is consistent with the observed jitter. This result demonstrates how important understanding convection is for modeling Cepheid stellar structure and evolution, how convection determines the red edge of the instability strip, and just how sensitive Cepheid light curves are to atmospheric physics.

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“…It has become evident that large positive-P dot objects are relatively more common among long-P orb systems than expected. Poleski et al (2011) reported a large negative (−2 × 10 −3 ) period variation of superhumps in OGLE-BLG-DN-001, an SU UMa-type dwarf nova in the period gap. Their data, however, covered the growing stage of superhumps and this large negative P dot is most likely a result of stage A-B transition.…”

Section: Period Derivatives During Stage Bmentioning

confidence: 97%

Survey of period variations of superhumps in SU UMa-type dwarf novae. V. The fifth year (2012–2013)

Katô¹,

Hambsch²,

Maehara³

et al. 2014

Publications of the Astronomical Society of Japan

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Continuing the project described in Kato et al. (2009, PASJ, 61, S395), we collected times of superhump maxima for SU UMa-type dwarf novae mainly observed during the 2012-2013 season. We found three objects (V444 Peg, CSS J203937, and MASTER J212624) having strongly positive period derivatives despite the long orbital period (P orb ). By using the period of growing stage (stage A) superhumps, we obtained mass ratios for six objects. We characterized nine new WZ Sge-type dwarf novae. We made a pilot survey of the decline rate in the slowly fading parts of SU UMa-type and WZ Sge-type outbursts. The decline time scale was found to generally follow an expected P 1/4 orb dependence, and WZ Sge-type outbursts also generally follow this trend. There are some objects which show slower decline rates, and we consider these objects good candidates for period bouncers. We also studied unusual behavior in some objects, including BK Lyn which made a transition from an ER UMa-type state to a novalike (standstill) state in 2013, and unusually frequent occurrences of superoutbursts in NY Ser and CR Boo. We applied the least absolute shrinkage and selection operator (Lasso) power spectral analysis, which has been proven to be very effective in analyzing the Kepler data, to the ground-based photometry of BK Lyn, and detected a dramatic disappearance of the signal of negative superhumps in 2013. We suggested that the mass-transfer rates did not strongly vary between the ER UMa-type state and novalike state in BK Lyn, and this transition was less likely caused by a systematic variation of the mass-transfer rate.

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Empirical microlensing event rates predicted by a phenomenological model

Cited by 74 publications

References 12 publications

On the effect of rotation on populations of classical Cepheids

On the effect of rotation on populations of classical Cepheids

Convection, granulation, and period jitter in classical Cepheids

Survey of period variations of superhumps in SU UMa-type dwarf novae. V. The fifth year (2012–2013)

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