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2. Observations and reduction

The present work is based on two spectrograms, taken with the Coudé spectrograph of the 2 m RCC telescope of the National Astronomical Observatory Rozhen (NAO) on Sep. 8, 1995 (JD 2449969.38) and Sep. 13, 1995 (JD 2449974.38). The observations were performed in the region from 3600 Å to 5000 Å on ORWO ZU emulsion, with a resolution of 0.5 Å. (The reciprocal linear dispersion was 18 Åmm-1.) Both exposures were comparatively deep, each of 240 minutes, in order to bring out the wings of the bright emission lines and to detect the fainter features. The spectra were digitized with the Joyce Loebl microdensitometer of NAO and ReWiA package was used for wavelength and density calibration as well as for calculation of the radial velocities and the equivalent widths. Sections of the spectrum taken on JD 2449969.38 are displayed in Fig. 1 (click here) where the lines with measured radial velocities have been marked. As the strongest lines are not seen in this figure, the profile of one of them is displayed separately in Fig. 2 (click here). The profiles of the others are similar. The radial velocity of each group of lines is listed in Table 1 (click here).

  figure225  figure232  figure238
Figure 1: Sections of the spectrum, taken on JD 2449969.38. The ordinate scale is in arbitrary units

  figure242
Figure 2: The profile of the HeII 4686 line, observed on JD 2449969.38 and normalized with respect to the local continuum. It consists of two components - a narrow and a broad one

 

Elem. JD 2449000tex2html_wrap_inline1338 \ Elem. JD 2449000tex2html_wrap_inline1338
96938 97438 96938 97438
Abs. lines tex2html_wrap_inline1342 tex2html_wrap_inline1344 HeII, NIII, CIII tex2html_wrap_inline1346 tex2html_wrap_inline1348
HI tex2html_wrap_inline1350 tex2html_wrap_inline1352 HeII 4686 (N) -13.7 -6.5
He1I tex2html_wrap_inline1360 tex2html_wrap_inline1362 [OIII] 4363 -16.1 -18.7
He3I tex2html_wrap_inline1370 tex2html_wrap_inline1372 FeII, TiII tex2html_wrap_inline1374 tex2html_wrap_inline1376

Table 1: Radial velocities in units of kms-1

 

We obtained the line fluxes using only the spectrogram of JD 2449969.38 as it turned out that the sensitivity of the other one was decreased in the long wavelengths region. Only fluxes of comparatively stronger lines were measured such that their equivalent width errors should be less than 30%. We consider the intensities of the same emission lines investigated in the work of Tomov (1993a) to have possibility for comparison. Some of these lines are the members of Pickering series of HeII having wavelengths tex2html_wrap_inline1378tex2html_wrap_inline1378 4200 and 4542 Å. They are unresolved blends. At the phases of our observations the line HeII 4542 is blending with the line FeII 4542, but the latter of them has considerably lower intensity. The line HeII 4200 is blending with the line NIII 4200 which has also lower intensity. In our opinion the blending of these lines works unessentially on the measurement of their equivalent widths.

The line fluxes have been obtained by means of our unpublished tex2html_wrap_inline1382 and tex2html_wrap_inline1384 photometric estimates, taken on JD 2449974.34. The monochromatic continuum fluxes at the positions of emission lines considered were calculated via linear interpolation of the fluxes at the positions of the sensitivity maxima of the B and V photometric systems. The error of the monochromatic continuum fluxes, obtained in this way, is due first of all to the presence of the bands of titanium oxide. This error is approximately equal to the error of the level of the local continuum (tex2html_wrap_inline139010%), as titanium oxide bands of the AG Peg system are shallow because of an overwhelming by the hot continuum (Boyarchuk 1966; Tomov & Tomova 1992). The line fluxes were corrected for interstellar reddening. There are several values for the excess E(B-V), obtained by different methods and placed in the range 0.08-0.15 (Penston & Allen 1985). We adopted the value E(B-V)=0.12 and used the extinction law by Seaton (1979). The line fluxes are listed in Table 2 (click here).

 

Line 1986 1995 Line 1986 1995 Line 1986 1995
NIII 4097 0.43 0.19 FeII 4296 0.06 0.03 FeII 4584 0.14 0.14
Htex2html_wrap_inline1404 4103 4.95 1.52 Htex2html_wrap_inline1406 4340 (N) 8.07 2.00 FeII 4629 0.15 0.10
He3I 4121 0.32 0.16 [OIII] 4363 0.34 0.07 NIII 4634 0.19 0.15
He1I 4144 0.49 0.17 He1I 4388 0.59 0.36 NIII 4640 0.35 0.21
FeII 4173 0.11 0.07 He3I 4471 0.71 0.38 HeII 4686 (N) 5.20 1.74
FeII 4179 0.12 0.09 FeII 4508 0.09 0.04 He3I 4713 0.53 0.29
HeII 4200 0.10 0.08 FeII 4520 0.09 Htex2html_wrap_inline1418 4861 (N) 14.71 6.02
FeII 4233 0.23 0.11 HeII 4542 0.12 0.12 He1I 4922 1.18 0.65

Table 2: Emission line fluxes in units of 10-11 ergcm-2s-1

 

 

JDtex2html_wrap_inline1424 Phase Abs.lines HeII 4686 HI He1I HeII, NIII, HeII 4686 [OIII] 4363
2446000+ (B) OIII, CIII (N)
221.50 0.300 tex2html_wrap_inline1428 -0.6 tex2html_wrap_inline1432 tex2html_wrap_inline1434 tex2html_wrap_inline1436 -6.8 -21.1
244.55 0.329 tex2html_wrap_inline1442 tex2html_wrap_inline1444 tex2html_wrap_inline1446 tex2html_wrap_inline1448 -22.3 -31.4
252.52 0.338 tex2html_wrap_inline1454 tex2html_wrap_inline1456 tex2html_wrap_inline1458 tex2html_wrap_inline1460 -11.8 -29.5
252.57 0.339 tex2html_wrap_inline1466 -6.7 tex2html_wrap_inline1470 tex2html_wrap_inline1472 tex2html_wrap_inline1474 -21.7 -29.9
273.52 0.364 tex2html_wrap_inline1480 3.0 tex2html_wrap_inline1482 tex2html_wrap_inline1484 tex2html_wrap_inline1486 -25.3 -36.6
277.40 0.369 tex2html_wrap_inline1492 tex2html_wrap_inline1494 tex2html_wrap_inline1496 tex2html_wrap_inline1498 -19.5 -33.7
301.39 0.398 tex2html_wrap_inline1504 tex2html_wrap_inline1506 tex2html_wrap_inline1508 tex2html_wrap_inline1510 -29.3 -35.0
330.23 0.434 tex2html_wrap_inline1516 -35.8 tex2html_wrap_inline1520 tex2html_wrap_inline1522 tex2html_wrap_inline1524 -34.6 -40.2
370.30 0.483 tex2html_wrap_inline1530 -32.7 tex2html_wrap_inline1534 tex2html_wrap_inline1536 tex2html_wrap_inline1538 -43.1 -42.3
452.21 0.583 tex2html_wrap_inline1544 tex2html_wrap_inline1546 tex2html_wrap_inline1548 -53.9 -45.5
603.53 0.768 tex2html_wrap_inline1554 -36.8 tex2html_wrap_inline1558 tex2html_wrap_inline1560 tex2html_wrap_inline1562 -26.3 -25.7
603.57 0.768 tex2html_wrap_inline1568 -47.4 tex2html_wrap_inline1572 -21.3 tex2html_wrap_inline1576 -22.6 -30.1
605.49 0.771 tex2html_wrap_inline1582 tex2html_wrap_inline1584 tex2html_wrap_inline1586 tex2html_wrap_inline1588 -27.8 -20.2
627.53 0.798 tex2html_wrap_inline1594 -41.7 tex2html_wrap_inline1598 tex2html_wrap_inline1600 tex2html_wrap_inline1602 -24.1 -22.7
630.19 0.801 tex2html_wrap_inline1608 -50.4 tex2html_wrap_inline1612 tex2html_wrap_inline1614 tex2html_wrap_inline1616 -20.2 -16.2
638.49 0.811 tex2html_wrap_inline1622 -43.3 tex2html_wrap_inline1626 tex2html_wrap_inline1628 tex2html_wrap_inline1630 -25.0 -19.8
638.59 0.811 tex2html_wrap_inline1636 tex2html_wrap_inline1638 tex2html_wrap_inline1640 tex2html_wrap_inline1642 -16.7 -17.7
660.53 0.838 tex2html_wrap_inline1648 tex2html_wrap_inline1650 tex2html_wrap_inline1652 tex2html_wrap_inline1654 -21.0 -14.1
752.18 0.950 tex2html_wrap_inline1660 tex2html_wrap_inline1662 tex2html_wrap_inline1664 tex2html_wrap_inline1666 0.9 7.6
755.27 0.954 tex2html_wrap_inline1668 -30.9 tex2html_wrap_inline1672 tex2html_wrap_inline1674 tex2html_wrap_inline1676 -2.8 2.1
775.15 0.979 tex2html_wrap_inline1680 -28.6 tex2html_wrap_inline1684 tex2html_wrap_inline1686 tex2html_wrap_inline1688 5.8 14.8
928.50 0.166 tex2html_wrap_inline1690 32.3 tex2html_wrap_inline1692 tex2html_wrap_inline1694 tex2html_wrap_inline1696 -3.1 -4.0
990.52 0.242 tex2html_wrap_inline1702 10.5 tex2html_wrap_inline1704 tex2html_wrap_inline1706 tex2html_wrap_inline1708 2.8 -37.6
991.51 0.244 tex2html_wrap_inline1712 tex2html_wrap_inline1714 tex2html_wrap_inline1716 tex2html_wrap_inline1718 -9.4 -31.7
1023.53 0.283 tex2html_wrap_inline1724 tex2html_wrap_inline1726 tex2html_wrap_inline1728 tex2html_wrap_inline1730 -14.0 -33.3
1025.48 0.285 tex2html_wrap_inline1736 tex2html_wrap_inline1738 tex2html_wrap_inline1740 tex2html_wrap_inline1742 -22.3 -33.2
1047.26 0.312 tex2html_wrap_inline1748 13.8 tex2html_wrap_inline1750 tex2html_wrap_inline1752 tex2html_wrap_inline1694 -16.7 -34.9
1346.50 0.678 tex2html_wrap_inline1760 tex2html_wrap_inline1762 tex2html_wrap_inline1764 -40.7 -31.8

Table 3: Radial velocity data of AG Peg in units of kms-1 (Tomov & Tomova 1992)

 

For the aims of our consideration the ephemeris of Fernie (1985) tex2html_wrap_inline1770tex2html_wrap_inline1772 will be used. The epoch of the photometric maximum when the hot companion is before the giant is used as a start epoch. In this case our observations are at phases 0.891 and 0.897.

The data obtained will be compared with the results of our previous observations (Tomov & Tomova 1992) and that is why some of these results are listed in Table 3 (click here) and displayed in Fig. 3 (click here) as well. These are radial velocities data derived also on the basis of photographic observations in the blue spectral region. 40% of these spectrograms were taken with the Coudé spectrograph of the 6m telescope of the Special Astrophysical Observatory of Russian Academy of Sciences and have dispersion of 9 Åmm-1 and the rest - with the Coudé spectrograph of the 2 m RCC telescope of NAO, with dispersion of 18 Åmm-1. All these spectrograms were processed with the oscilloscopic comparator of NAO, whose positioning error is equal to 0.5 tex2html_wrap_inline1778m.

  figure320
Figure 3: The orbital radial velocity curves of the visual lines of AG Peg from the work of Tomov & Tomova (1992). The elements of each curve as well as the designation of the M3 giant and the barycentric velocity have been marked

 

Group of lines Phase V0 K s
shift (kms-1) (kms-1) (kms-1)
Abs. lines -18.37 5.22 1.60
HeII 4686 (B) 0.50 -20.69 31.77 9.88
HI 0.38 -18.56 27.94 6.88
He1I 0.38 -16.96 9.01 3.91
HeII, NIII, OIII, CIII 0.38 -16.74 19.18 3.14
HeII 4686 (N) 0.40 -18.00 27.36 5.12
 4363 0.34 -22.81 24.08 6.83

Table 4: Parameters of the radial velocities curves of AG Peg

 

The radial velocity curves of all groups of emission lines (Fig. 3 (click here)) were plotted by means of the same program, used for obtaining the orbital solution. The lines in this figure plot the best-fitting circular orbits for the data in Table 3 (click here). The phase shift of each curve with respect to the absorption lines velocity curve, determined by the orbital motion of the cool component, is presented in the second column of Table 4 (click here). The parameters corresponding to the baricentric velocity V0 and the semiamplitude K for each curve are presented in the third and fourth columns of this table. The standard deviation s is in the last column.


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