Speckle Observations of Binary Stars with the WIYN Telescope. I

Rochester Institute of Technology RIT Scholar Works Articles 1-1999 Speckle Observations of Binary Stars with the WIYN Telescope. I. Measures During 1997 Elliott .P Horch Rochester Institute of Technology Zoran Ninkov Rochester Institute of Technology William F. van Altena Yale University Reed D. Meyer Yale University Terrence M. Girard Yale University See next page for additional authors Follow this and additional works at: http://scholarworks.rit.edu/article Recommended Citation Elliott orH ch et al 1999 AJ 117 548 DOI: https://doi.org/10.1086/300704 This Article is brought to you for free and open access by RIT Scholar Works. It has been accepted for inclusion in Articles by an authorized administrator of RIT Scholar Works. For more information, please contact [email protected]. Authors Elliott .P Horch, Zoran Ninkov, William F. van Altena, Reed D. Meyer, Terrence M. Girard, and J. Gethyn Timothy This article is available at RIT Scholar Works: http://scholarworks.rit.edu/article/767 THE ASTRONOMICAL JOURNAL, 117:548È561, 1999 January ( 1999. The American Astronomical Society. All rights reserved. Printed in U.S.A. SPECKLE OBSERVATIONS OF BINARY STARS WITH THE WIYN TELESCOPE. I. MEASURES DURING 19971 ELLIOTT HORCH2 AND ZORAN NINKOV Center for Imaging Science, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623-5604; ephpci=cis.rit.edu, ninkov=cis.rit.edu WILLIAM F. VAN ALTENA,REED D. MEYER,2 AND TERRENCE M. GIRARD Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8101; vanalten=astro.yale.edu, rdm=astro.yale.edu, girard=astro.yale.edu AND J. GETHYN TIMOTHY Nightsen, Inc., 30 Fresno Road, Warwick, RI 02886-1407; gethyn=nightsen.com Received 1998 August 21; accepted 1998 October 5 ABSTRACT Two hundred seventy-seven position angle and separation measures of 154 double stars are presented. Three of the systems were previously unknown to be double, and 16 other systems were discovered earlier this decade by the Hipparcos satellite. Measures are derived from speckle observations taken with the Wisconsin-Indiana-Yale-NOAO (WIYN) 3.5 m telescope located at Kitt Peak, Arizona. Speckle images were obtained using two di†erent imaging detectors, namely, a multianode microchannel array (MAMA) detector and a fast-readout CCD. A measurement precision study was performed on a sample of binaries with extremely well known orbits by comparing the measures obtained here to the ephemeris predictions. For the CCD, the root mean square (rms) deviation of residuals was found to be 3.5 milli- arcseconds (mas) in separation and1¡.2 in position angle, while the residuals of the MAMA data varied depending on the magniÐcation used and seeing conditions but can be comparable or superior to the CCD values. In addition, the two cameras were compared in terms of the detection limit in total magnitude and magnitude di†erence of the systems under study. The MAMA system has the ability to detect some systems with magnitude di†erences larger than 3.5, although reliable astrometry could not be obtained on these objects. Reliable astrometry was obtained on a system of magnitude di†erence of 5.3 with the CCD system. Key words: astrometry È binaries: close È binaries: visual È techniques: interferometric 1. INTRODUCTION bination of relative astrometry derived from speckle observations and parallax can only provide total masses of the Mignard et al. (1995) have discussed that, in addition to systems under study, but concurrent spectroscopic obser- measuring the trigonometric parallaxes of approximately vations can be started in cases where orbital motion is 118,000 stars, the Hipparcos satellite has discovered some detected. In this way, individual masses can eventually be 6000 new or newly suspected double star systems. A frac- obtained. In this paper, we focus on initial speckle obser- tion of these systems are no doubt true (i.e., gravitationally vations, calibration issues, and measurement precision, and bound) binaries that could provide valuable information therefore many of the objects for which relative astrometry concerning stellar masses and the main-sequence mass- is presented are not Hipparcos discoveries but rather well- luminosity relation, if their orbits were known in sufficient known binaries. However, as the observational program detail. A distinct advantage of this set of stars in determin- continues and the astrometric calibrations become routine, ing masses and luminosities is that their parallaxes and, in we plan to shift the emphasis to the Hipparcos discovery many cases, the magnitude di†erences have already been objects. measured by the Hipparcos satellite. However, with the OBSERVATIONS exception of the relative astrometry appearing in the Hip- 2. parcos Catalogue (ESA 1997), no substantial orbital data We have the use of two imaging detectors for speckle exist for any of these objects at present. work at WIYN. The Ðrst is a multianode microchannel Many of these newly discovered systems have separations array (MAMA) detector. The MAMA system used here and magnitude di†erences that are easily observable by way (based on the original design of Morgan 1989 and including of speckle interferometry. We have therefore initiated a new some of the original components) was most recently used at program of speckle observations of this set of stars at the El Leoncito, Argentina (Horch et al. 1996). As described in WIYN Observatory, Ðrst to identify which systems exhibit that work, a typical data Ðle with the MAMA system con- orbital motion and second to determine the orbits of the sists of between 1 and 2 million photon events, depending true binaries en route to deriving their masses. The com- on the brightness of the source. For all observations described here, the so-called ““ high-resolution ÏÏ mode (Kasle & Morgan 1991) of decoding MAMA photon event posi- ÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈ tions was used. In this mode, the camera has 7 micron 1 The WIYN Observatory is a joint facility of the University of Wiscon- sin, Indiana University, Yale University, and the National Optical square pixels, although the spatial resolution is limited by Astronomy Observatories (NOAO). the microchannel plate pore spacing of 10 microns. Since 2 Visiting Astronomer, Kitt Peak National Observatory. the MAMA is a photon-counting camera, the arrival time 548 SPECKLE OBSERVATIONS OF BINARY STARS. I. 549 of each photon event is recorded, and therefore the data are 3. DATA REDUCTION divided into frames in the analysis phase. Typical frame 3.1. Measurement of the Pixel Scale exposure times for the data reduced here ranged from 5 to 15 ms. For the three modes of observing discussed here (MAMA The second detector is a fast readout CCD. The CCD low magniÐcation, MAMA 2.5], and CCD low used here is a 2033 ] 2048 pixel KAF 4200 chip with 9 magniÐcation), the fundamental scale calibration was micron square pixels. This is a front-illuminated device with obtained by attaching a slit mask to the tertiary mirror a quantum efficiency of 40% at 7000A , and it has camera baffle support structure, which is located approximately 84 electronics capable of reading out pixels at a rate of 500 cm above the tertiary mirror of the telescope. The mask is kHz. Speckle data are obtained with the chip using the therefore placed in the converging beam between the sec- shutterless charge transfer method described in Horch, ondary mirror and the image plane at the Nasmyth focus. Ninkov, & Slawson (1997). However, in that paper, the When the telescope is pointed at a single star, a di†raction authors used a 60 cm telescope and read out strips of pattern is produced on the detector such that the spacing of dimensions 64 ] 1024 pixels, with each strip containing 32 fringes uniquely determines the scale in arcseconds per individual speckle frames. At the WIYN Observatory, pixel, once the slit spacing, the distance from the Nasmyth because the telescope is much larger and consequently the focus to the mask and the f/number of the converging beam di†raction limit is much smaller, a larger subframe format is are known. While at the telescope, the distance along the required to simultaneously contain the seeing disk and optical axis from the mask to the center of the tertiary oversample the di†raction limit of the telescope. For WIYN mirror was measured to be 840.2 ^ 3.2 mm. The slit base- observing, strip formats of 128 ] 1024 pixels (with 8 speckle lines were also measured, ranging from the shortest of frames per strip) and 128 ] 1120 pixels (with 10 speckle 54.9 ^ 0.2 mm to the longest of 439.9 ^ 0.2 mm. The dis- frames per strip) have been used. With the current readout tance from the center of the tertiary to the Nasmyth focus electronics, an e†ective frame readout rate of approximately and the f/number had already been precisely measured by 4.5 Hz has been obtained, meaning that a typical obser- Kitt Peak personnel for other reasons (with results of vation with the CCD (which is 960 frames) requires 3.5 3177.3 ^ 2.2 mm and 6.28 ^ 0.01, respectively), and these minutes of observing time. For all of the data presented values were adopted for our scale calculations. here, a frame integration time of 50 ms was used. In the case of MAMA data, the position angle o†set, i.e., Both systems were mounted at the Nasmyth focus known the orientation of the detector pixels relative to true north, as the WIYN port. This focus delivers an f/6.3 beam, which was measured by trailing stars across the detector. The path is then increased to f/16 (referred to as low magniÐcation) or of the star, as judged by binning the photon events into 10 f/44 (referred to as 2.5] magniÐcation) by the speckle ms frames and computing the path of frame centroids, then optics, depending on the amount of magniÐcation desired.

Load more