Search Publications
Stellar Photometry With DSLR: Benchmark of Two Color Correction Techniques Toward Johnson's VJ and Tycho VT
Pieri, R.
DSLRs are now routinely used for measuring the V magnitude of stars through their G channel output. This requires a transformation to Johnson V, using a correction based on the catalogue (B-V) color indices of the stars. This paper reviews the responses of the involved passbands and proposes an alternate solution using a synthetic filter made by c…
The History of Variable Stars: A Fresh Look
Hatch, R. A.
(Abstract only) For historians of astronomy, variable stars are important for a simple reason - stars change. But good evidence suggests this is a very modern idea. Over the millennia, our species has viewed stars as eternal and unchanging, forever fixed in time and space - indeed, the Celestial Dance was a celebration of order, reason, and stabil…
Deep Infrared ZAMS Fits to Benchmark Open Clusters Hosting Delta Scuti Stars
Turner, D. G.; Majaess, D. J.; Lane, D. J. +1 more
This research aims to secure precise distances for cluster δ Scuti stars in order to investigate their properties via a VI Wesenheit framework. Deep JHKs color-color and zero-age main sequence (ZAMS) relations derived from ~700 unreddened stars featuring 2MASS photometry and precise Hipparcos parallaxes (d≤25 pc) are applied to establish distances…
Anchoring the Universal Distance Scale Via a Wesenheit Template
Henden, A. A.; Turner, D. G.; Majaess, D. J. +2 more
A VI Wesenheit diagram featuring SX Phoenicis, δ Scuti, RR Lyrae, and type II and classical Cepheid variables is calibrated by means of geometric-based distances inferred from HST, Hipparcos, and VLBA observations (n = 30). The distance to a target population follows from the offset between the observed Wesenheit magnitudes and the calibrated temp…
Searching for Orbital Periods of Supergiant Fast X-ray Transients
Stella, L.; Walter, R.; Bozzo, E. +2 more
Building on the currently active program of observing High Mass X-ray Binaries (HMXBs), we describe here a challenging extension of the project for experienced AAVSO observers who want to push their observing to the limit. A new subclass of HMXBs, the Supergiant Fast X-ray Transients (SFXTs), have been recently discovered in INTEGRAL data and are …
Pulsating B Stars Discovered by HIPPARCOS
Eyer, L.; Aerts, C.; De Cat, P. +4 more
We present a classification of 267 new variable B-type stars discovered by Hipparcos, which results in, among others, a huge number of new Slowly Pulsating B stars and several supergiants with ? Cyg-type variations. Our results clearly point out the bias towards short-period variables of earlier, ground-based surveys of variable stars.
The po…The HIPPARCOS Mission: a New Era for Variable Star Astronomy
Eyer, L.; Grenon, M.
Initially planned as a pure astrometric mission, Hipparcos was optimized to produce the highest achievable photometric accuracy in the Hp broad-band and in the Tycho BT and VT bands. A complex calibration process allowed to cope with the rapid change of the optics and to fix the magnitude scale to better than 0.001 magnitude throughout the mission…
The Characteristics of the Cool Component of the Cataclysmic Variable AE Aquarii from Hipparcos Observations
Friedjung, M.
The parallax of the cataclysmic binary AE Aquarii, found using the Hipparcos satellite, is combined with published infrared observations. Indications are obtained that the cool component is somewhat above the main sequence. However, this result is not absolute because of the errors and uncertainties.
Using XMM-Newton and Optical Photometry to Figure Out CVs
Szkody, P.; Henden, A.; Homer, L.
X-ray light curves from XMM-Newton combined with optical data from the satellite and ground-based observers provide distinctive shapes and periodicities that give information on the correct classification of cataclysmic variables. Our recent data on three SDSS sources with strong helium emission are used to identify a highly magnetic system (a pol…
Pulsating B Stars Discovered by HIPPARCOS
Poretti, E.; Musazzi, F.
The photometric properties of the variable stars located in the lower part of the classical instability strip are discussed. The importance of the determination of some light curve parameters and their connection with the stellar models are stressed, with a particular emphasis on large amplitude Delta Scuti stars.