Peremennye Zvezdy

Peremennye Zvezdy (Variable Stars) 26, No. 5, 2006

Received 5 May; accepted 5 July.

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The Emission Spectrum of T Tau in 1971-1979

Ismailov, N.Z.; Guliev, N.Kh.; Aliyeva, A.A.

Shamakha Astrophysical Observatory, National Academy of Sciences of Azerbaijan, Shamakha, Azerbaijan
E-mail: Box1955n@yahoo.com

1. Introduction

The star T Tau is the prototype of pre-main sequence (PMS) low-mass T Tauri-type stars, which are at an early stage of evolution. Numerous spectral and photometric observations, carried out during many years, revealed strong variability of this unique star's emission spectrum and visual light (Joy 1945, Herbig 1977, Ismailov 1974, Zaitseva 1978, Zaitseva and Kolotilov 1977). Sometimes, the light curve shows quasi-periodic light variations with a period of 28 (Zaitseva 1978, Herbst et al. 1987). Recently, a long-period wave in the star's brightness, with a nearly 6-year period, was detected (Ismailov and Samus 2003, Mel'nikov and Grankin 2005).

Studies of the recent 20 years demonstrate that T Tau is an exceptional member of the class, a triple system, with an infrared southern component (T Tau S) in 0 7 from the northern component (T Tau N) (Dyck et al. 1982). T Tau S is itself a binary, with a projected separation of 0 07 (Koresko 2000). Solf and Böhm (1999) found that both T Tau N and T Tau S possessed bipolar jets, the two jet systems directed perpendicularly. From spectroscopy, Tracy et al. (2001) revealed evidence for accretion of matter on T Tau S. The data from Loinard et al. (2003) demonstrate relative motions of the IR components of T Tau S. They show that the lower-mass component, T Tau Sb, is running away from the system.

During 1971-1988, Z.A. Ismailov carried out long-time homogenous low-resolution spectroscopy of T Tau at Shamakha Observatory. Some of the results based on these observations have already been published by different authors (Ismailov 1972, 1973, Guliev, 1991, 1994, Ismailov and Rustamov 1999). Below we briefly remind the basic results from this spectroscopy and from spectroscopic data by other authors.

Synchronous increase of line intensities of hydrogen H, H, H and of H and K CaII emission lines, nearly threefold in 3 hours, was discovered (Ismailov 1974). During the star's transition from photometric quiescence to a more active state, variations of the H emission line profile from night to night, evidencing for mass loss from the star, were observed. The intensity of the H emission increased with increasing UV excess (Zaytseva 1978). 90-120 min and 18-20-day quasi-cyclic variations of equivalent widths and radial velocities of hydrogen lines and flare activity in the H, K CaII lines were revealed by Guliev (1991, 1994). The star's spectral type can be described as G8-K0V, its radial velocity is 20-22 km/s (Herbig 1977, Rustamov 1999).

In this paper, we present parameters of emission spectral lines determined from our complete spectroscopic material for 1971-1979.

2. Observations and Results

Our spectroscopic observations were carried out in the Cassegrain focus of the 2 m telescope of the Shamakha Observatory (National Academy of Sciences, Azerbaijan) using the prism spectrograph with inverse dispersion 94 Å/mm at H. The spectral range was  Å. The spectra were reduced using standard techniques (Guliev 1994, Ismailov and Rustamov 1999). We used microphotometer tracing with a magnification of 40 to measure equivalent widths of the strongest emission spectral lines: H-H, H and K CaII, [SII] Å. Mean standard errors of the equivalent widths were within 15%, those of the radial velocities, within  km/s.

Table 1 presents all measurements of (in Å) and (in km/s) for the program emission lines.

Table 1. The spectroscopic observations of HD 200775

Sp. JD H H H H+H [SII]4068 H CaII K CaII
No. 2440000+
1 989.143 3.9 - - - - - 0.6 - 1.8 - 2.2 -
2 989.158 4.3 - - - - - 0.6 - 2.7 - 2.6 -
3 989.171 2.6 20 - - - - 0.9 - 2.9 - 2.2 -
4 989.187 6.2 144 - - - - 0.3 - 2.4 - 2.6 -
5 989.201 2.4 97 - - - - 0.4 - 1.5 - 1.5 -
6 989.237 2.1 - - - - - 0.4 - 1.5 - 1.2 -
7 989.251 4.6 - - - - - 1.1 - 1.3 - 1.3 -
8 989.274 3.8 - - - - - 0.9 - 0.5 - 0.9 -
9 990.521 1.2 - - - - - - - 1.2 - 1.4 -
10 990.535 2.4 - - - - - - - 1.1 - 1.3 -
11 990.551 4.2 - - - - - - - 1.9 - 1.5 -
12 990.565 3.5 - - - - - - - 1.6 - 1.6 -
13 995.221 2.3 - - - - - - - 1.5 - 1.8 -
14 995.551 2.0 - - - - - - - 1.9 - 1.5 -
15 998.512 2.2 - - - - - - - 1.6 - 1.5 -
16 998.531 3.4 - - - - - - - 1.1 - 1.1 -
17 998.550 4.9 - - - - - - - 1.5 - 1.3 -
18 1294.135 5.4 - - - - - - - 4.3 - 3.4 -
19 1294.159 4.9 - - - - - - - 5.0 - 2.6 -
20 1294.180 7.4 - - - - - - - 3.5 - 2.6 -
21 1294.202 3.9 - - - - - - - 2.2 - 1.6 -
22 1294.222 2.6 - - - - - - - 2.3 - 2.8 -
23 1294.246 6.2 - - - - - - - 2.4 - 2.2 -
24 1294.267 5.5 - - - - - - - 2.6 - 1.7 -
25 1294.291 4.8 - - - - - - - 1.8 - 1.7 -
26 1294.3