Direct Detection of the Close Companion of Polaris with the Hubble Space Telescope

  title={Direct Detection of the Close Companion of Polaris with the Hubble Space Telescope},
  author={Nancy Remage Evans and Gail H. Schaefer and Howard E. Bond and Giuseppe Bono and Margarita Karovska and Edmund P. Nelan and Dimitar D. Sasselov and Brian D. Mason},
  journal={The Astronomical Journal},
Polaris, the nearest and brightest classical Cepheid, is a single-lined spectroscopic binary with an orbital period of 30 yr. Using the High Resolution Channel of the Advanced Camera for Surveys on board the Hubble Space Telescope (HST) at a wavelength of ~2255 A, we have directly detected the faint companion at a separation of 017. A second HST observation 1.04 yr later confirms orbital motion in a retrograde direction. By combining our two measures with the spectroscopic orbit of Kamper and… 
The Orbit of the Close Companion of Polaris: Hubble Space Telescope Imaging, 2007 to 2014
As part of a program to determine dynamical masses of Cepheids, we have imaged the nearest and brightest Cepheid, Polaris, with the Hubble Space Telescope Wide Field Planetary Camera 2 and Wide Field
Hubble Space Telescope: Snapshot Survey for Resolved Companions of Galactic Cepheids
We have conducted an imaging survey with the Hubble Space Telescope Wide Field Camera~3 (WFC3) of 70 Galactic Cepheids, typically within 1~kpc, with the aim of finding resolved physical companions.
Hubble Space Telescope Trigonometric Parallax of Polaris B, Companion of the Nearest Cepheid
Polaris, the nearest and brightest Cepheid, is a potential anchor point for the Leavitt period-luminosity relation. However, its distance is a matter of contention, with recent advocacy for a
We have observed Cepheid Polaris (α UMi A: F7 Ib [Aa] + F6 V [Ab]) with Chandra ACIS-I for 10 ks. An X-ray source was found at the location of Polaris with log LX = 28.89 erg s–1 (0.3-8 keV) and kT =
The Mass of the Cepheid V350 Sgr
V350 Sgr is a classical Cepheid suitable for mass determination. It has a hot companion which is prominent in the ultraviolet and which is not itself a binary. We have obtained two high resolution
We identify and phase a sample of 107 Cepheids with 10 days < P < 100 days in M81 using the Large Binocular Telescope and calibrate their B, V, and I mean magnitudes with archival Hubble Space
Homing in on Polaris: A 7 M⊙ first-overtone Cepheid entering the instability strip for the first time
A recently presented HST/FGS parallax measurement of the Polaris system has been interpreted as evidence for the Cepheid Polaris Aa to be pulsating in the second overtone. An age discrepancy between
Multiplicity of Galactic Cepheids from long-baseline interferometry
Aims. We aim at detecting and characterizing the main-sequence companions of a sample of known and suspected Galactic binary Cepheids. The long-term objective is to accurately and independently
Binary Cepheids from optical interferometry
Classical Cepheid stars have been considered since more than a century as reliable tools to estimate distances in the universe thanks to their Period-Luminosity (P-L) relationship. Moreover, they are
Multiplicity of Galactic Cepheids from long-baseline interferometry I. CHARA/MIRC detection of the companion of V1334 Cygni
Context. More than 60% of Cepheids are in binary or multiple systems. Studying such systems could lead to a better understanding of the age and evolution of Cepheids. These are also useful tools to


A search for the binary companion of Polaris
Polaris has a spectroscopic orbit determined from an extensive series of observations as well as a more uncertain astrometric orbit. The determination of its mass and evolutionary state is of
Extended envelopes around Galactic Cepheids. II. Polaris and delta Cephei from near-infrared interfe
We present the results of long-baseline interferometric observations of the classical Cepheids Polaris and δ  Cep in the near infrared K'  band (1.9-2.3  μ m), using the FLUOR instrument of the CHARA
Extended envelopes around Galactic Cepheids I. Carinae from near and mid-infrared interferometry with the VLTI
We present the results of long-baseline interferometric observations of the bright southern CepheidCarinae in the infrared N (8−13 µm) and K (2.0−2.4 µm) bands, using the MIDI and VINCI instruments
Cepheid parallaxes and the Hubble constant
Revised Hipparcos parallaxes for classical Cepheids are analysed together with 10 Hubble Space Telescope (HST)-based parallaxes. In a reddening-free V, I relation we find that the coefficient of log
The period changes of polaris
The evolutionary changes in pulsation period for the Cepheid Polaris are reinvestigated using archival observational material (radial velocities, photometry, and eye observations) over the interval
On the Pulsation Mode Identification of Short-Period Galactic Cepheids
We present new theoretical period-radius relations for first-overtone Galactic Cepheids. Current predictions are based on several sequences of nonlinear, convective pulsation models at solar chemical
Cepheid Masses: FUSE Observations of S Muscae
S Mus is the Cepheid with the hottest known companion. The large ultraviolet flux means that it is the only Cepheid companion for which the velocity amplitude could be measured with the echelle mode
Theoretical Fits of the δ Cephei Light, Radius, and Radial Velocity Curves
We present a theoretical investigation of the light, radius, and radial velocity variations of the prototype δ Cephei. We find that the best-fit model accounts for luminosity and velocity amplitudes
Polaris, the nearest Cepheid in the Galaxy : atmosphere parameters, reddening and chemical composition
We present the results of our analysis of spectroscopic observations of α UMi (Polaris) obtained in 1994 (five spectra) and 2001‐2004 (30 spectra). The mean atmospheric parameters we derived are as
Pulsation and Evolutionary Masses of Classical Cepheids. I. Milky Way Variables
We investigate a selected sample of Galactic classical Cepheids with available distance and reddening estimates in the framework of the theoretical scenario provided by pulsation models, computed