1,297 research outputs found
Galactic Cepheids with Spitzer: I. Leavitt Law and Colors
Classical Cepheid variable stars have been important indicators of
extragalactic distance and Galactic evolution for over a century. The Spitzer
Space Telescope has opened the possibility of extending the study of Cepheids
into the mid- and far-infrared, where interstellar extinction is reduced. We
have obtained photometry from images of a sample of Galactic Cepheids with the
IRAC and MIPS instruments on Spitzer. Here we present the first mid-infrared
period-luminosity relations for Classical Cepheids in the Galaxy, and the first
ever Cepheid period-luminosity relations at 24 and 70 um. We compare these
relations with theoretical predictions, and with period-luminosity relations
obtained in recent studies of the Large Magellanic Cloud. We find a significant
period-color relation for the [3.6]-[8.0] IRAC color. Other mid-infrared colors
for both Cepheids and non-variable supergiants are strongly affected by
variable molecular spectral features, in particular deep CO absorption bands.
We do not find strong evidence for mid-infrared excess caused by warm (~500 K)
circumstellar dust. We discuss the possibility that recent detections with
near-infrared interferometers of circumstellar shells around delta Cep, l Car,
Polaris, Y Oph and RS Pup may be a signature of shocked gas emission in a
dust-poor wind associated to pulsation-driven mass loss.Comment: Accepted by The Astrophysical Journal on Nov 11, 200
Examining the validity of the multiple-sclerosis walking scale-12 with Rasch analysis: Results from an Italian study
Dataset on individual differences in self-reported personality and inferred emotional expression in profile pictures of Italian Facebook users
Calibrating the Cepheid Period-Luminosity relation with the VLTI
The VLTI is the ideal instrument for measuring the distances of nearby
Cepheids with the Baade-Wesselink method, allowing an accurate recalibration of
the Cepheid Period-Luminosity relation. The high accuracy required by such
measurement, however, can only be reached taking into account the effects of
limb darkening, and its dependence on the Cepheid pulsations. We present here
our new method to compute phase- and wavelength-dependent limb darkening
profiles, based on hydrodynamic simulation of Classical Cepheid atmospheres.Comment: 3 pages, 2 postscript figures, uses eas.cls LaTeX class file, to
appear in the proc. Eurowinter School "Observing with the VLTI", Feb 3-8
2002, Les Houches (France
Mining Digital Traces of Facebook Activity for the Prediction of Individual Differences in Tendencies Toward Social Networks Use Disorder: A Machine Learning Approach
The associations between sex drive, sexual self-concept, sexual orientation, and exposure to online victimization in Italian adolescents: Investigating the mediating role of verbal and visual sexting behaviors
Predicting Big Five personality traits from smartphone data: a meta-analysis on the potential of digital phenotyping
A SEARCH FOR MASS LOSS ON THE CEPHEID INSTABILITY STRIP USING H i 21 cm LINE OBSERVATIONS
We present the results of a search for H i 21 cm line emission from the circumstellar environments of four Galactic Cepheids (RS Pup, X Cyg, ζ Gem, and T Mon) based on observations with the Karl G. Jansky Very Large Array. The observations were aimed at detecting gas associated with previous or ongoing mass loss. Near the long-period Cepheid T Mon, we report the detection of a partial shell-like structure whose properties appear consistent with originating from an earlier epoch of Cepheid mass loss. At the distance of T Mon, the nebula would have a mass (H I+He) of ∼0.5M[subscript ⨀], or ~6% of the stellar mass. Assuming that one-third of the nebular mass comprises swept-up interstellar gas, we estimate an implied mass-loss rate of [superscript dot]M∼(0.6-2) x 10⁻⁵ M[subscript ⨀] yr−1. No clear signatures of circumstellar emission were found toward ζ Gem, RS Pup, or X Cyg, although in each case, line-of-sight confusion compromised portions of the spectral band. For the undetected stars, we derive model-dependent 3 upper limits on the mass-loss rates, averaged over their lifetimes on the instability strip, of ≲ (0.3-6) x 10⁻⁶ M[subscript ⨀] yr⁻¹ and estimate the total amount of mass lost to be less than a few percent of the stellar mass.National Science Foundation (U.S.) (AST-1310930)Chandra X-ray Center (U.S.) (NAS8-03060
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