Young Stellar Objects

Intrinsic Properties of the Young Stellar Object SU Aurigae

10 June 2003, ApJ, 590, 357

L.E. DeWarf, J.F. Sepinsky, E.F. Guinan, I. Ribas, & I. Nadalin

Abstract:

Intensive long-term photometric observations of the archetypical young G2 IIIe stellar object SU Aurigae are analyzed to determine many of its photometric and physical properties. Combining nearly 2000 Strömgren uvby measures obtained using the 0.8m Four College Automatic Photoelectric Telescope, previously published photometry, and recently obtained high resolution echelle spectra has led to the determination of its effective temperature, surface gravity, luminosity, mass, age, rotation period, and absolute radius. Since the disk of SU Aur is seen at a high inclination angle (i.e. nearly edge-on), this complicates the observations with significant (ΔV

Δy

0.80 mag), and apparently random, drops in observed mean light. These are possibly due to the transits of protoplanetary bodies, protocomets, or associated accretion halos. In this study, an effort has been made to separate the contributions of the circumstellar disk from the intrinsic properties of the stellar core itself. Furthermore, photometry has been simultaneously obtained for the nearby young A0 Vpe stellar companion AB Aurigae. Analysis has shown that SU Aur and AB Aur are a coeval proper motion pair. Also included are certain photometric and physical properties of AB Aur.

Strömgren Photometry of the T Tauri Star SU Aurigae: Multi-timescale Light Variations

21 November 2000, IBVS, No. 4987

I. Nadalin, L.E. DeWarf, & E.F. Guinan

Abstract:

Photoelectric photometry from October 1993 to March 2000 is analyzed. Many "eclipse-like" dimming events have been observed, but have no predictable frequency. SU Aur exhibits variability, like many T Tauri stars, that is complicated. In addition to the short-term "dips" in the light curve, the star also varies on time scales of days, months, and years. Short period modulations, most likely due to the rotational effects of starspots, is measured for three relatively constant sections of the light curve. We determine the rotation period of the star to be about 1.7 days. Combining this with the projected rotational velocity (v sin i) yields a radius of 2.2 R.

Strömgren Photometry of the T Tauri Star SU Aurigae: Eclipse-Like Variability and Age Determination

3 February 1998, IBVS, No. 4551

L.E. DeWarf, E.F. Guinan, & T.M. Shaughnessy

Abstract:

Intensive photoelectric photometry of the classical T Tauri star SU Aurigae is analyzed. For observations from November 1993 to March 1994 a large (0.75 mag in u; 0.40 mag in y) "eclipse-like" drop in mean light was observed. The Strömgren color-independent indices ([c₁] and [m₁]) are seen to be unaffected, showing that this dimming event is probably caused by obscuring dust with properties similiar to the ISM. The interstellar absorption is determined, and when combined with the Hipparcos distance, yields estimates of its absolute magnitude and intrinsic colors. Plotting SU Aur on pre-main sequence evolution tracks yields an age of about 4 Myrs and a mass of 1.9 ± 0.1 M.

The Infrared Morphology of Young Stellar Objects Without Companions: A Speckle Interferometric Study

June 1993, AJ, 105, 2211

L.E. DeWarf & H.M. Dyck

Abstract:

One-dimensional speckle interferometric techniques are employed in the near-infrared wavelength range of 1.25 to 4.8 µm to ascertain the morphology of eighteen young stellar objects not known to have companions. We find that three of these objects are resolved as core/halo distributions or are partially resolved with a high level of confidence. Five other sources probably show some structure although the confidence level is lower. The ten remaining sources either show evidence for very small angular scale structure or are unresolved with an upper limit of about 0.2 arcsec. Our results are compared to other published angular size data. A relationship between the 12 to 25 µm spectral slope and the physical extent of the material in near infrared is discovered and compared to simple models. We interpret this relationship as an indication that the effective scale size of circumstellar matter surrounding young stellar objects decreases with advancing age.