We first selected a sample consisting of the sources among the
Nandra & Pounds (1994) Ginga sample classified as
pure Seyfert 1 galaxies. Seyfert 1.5, 2 and Narrow Emission Line Galaxies
are excluded:
generally these sources are highly absorbed and are therefore very faint
in the ROSAT energy range. We have also been forced to exclude the
Seyfert 1 3C 382 because no ROSAT PSPC observation is available.
This led to the selection of 17 low redshift (z <0.06) sources
spanning a wide range of luminosities (from a few up
to almost 1045 erg s-1). The main source characteristics, as
well as the date of Ginga observation (or the dates of the first and
last observations if more than one) are listed in Table 1 (click here).
From the Nandra & Pounds analysis we have used the slope of the
intrinsic power law derived by including in the model a reflection
component and, when relevant, a warm absorber (Table 10 of their paper
and last column of our Table 2 (click here)).
Obj. | z | ![]() | Ginga | ROSAT | |||
Obs. date | Obs. date | Exp. time2 | cts | CR3 | |||
Mkn 335 | 0.026 | 3.96 | 12/87-06/91 | 29-06-91 | 24586 | 65989 | 2.68![]() |
Fairall-9 | 0.046 | 2.82 | 11/90 | 10-05-91 | 8173 | 31834 | 3.89![]() |
NGC 3783 | 0.01 | 9.41 | 01/90 | 08-07-93 | 23344 | 38051 | 1.63![]() |
NGC 4051 | 0.002 | 1.37 | 06/87-11/90 | 16-11-91 | 28727 | 46509 | 1.62![]() |
NGC 4593 | 0.009 | 1.97 | 06/87-12/87 | 14-07-92 | 1261 | 1849 | 1.47![]() |
MCG 6-30-15 | 0.008 | 4.06 | 09/87-02/90 | 29-01-92 | 8513 | 17017 | 2.00![]() |
Mkn 841 | 0.036 | 2.24 | 07/90-01/91 | 20-01-92 | 17185 | 36656 | 2.13![]() |
3C 390.3 | 0.056 | 4.12 | 11/88 | 17-03-91 | 11516 | 12184 | 1.06![]() |
NGC 7469 | 0.017 | 4.82 | 06/88 | 28-05-92 | 18575 | 32933 | 1.77![]() |
Akn 120 | 0.033 | 11.3 | 09/88 | 18-09-91 | 24493 | 36127 | 1.47![]() |
NGC 5548 | 0.017 | 1.93 | 06/88-07/90 | 16-07-90 | 18861 | 34440 | 1.83![]() |
Mkn 509 | 0.036 | 3.99 | 10/88-10/90 | 29-10-92 | 2294 | 12534 | 5.46![]() |
NGC 3516 | 0.009 | 3.55 | 10/89-10/89 | 03-10-92 | 13081 | 61206 | 4.68![]() |
IC 4329 A | 0.014 | 4.55 | 07/89 | 04-01-93 | 8230 | 23307 | 2.83![]() |
MCG 2-58-22 | 0.048 | 3.51 | 06/89-11/89 | 21-05-93 | 18767 | 17322 | 0.92![]() |
NGC 7213 | 0.006 | 1.94 | 06/90-19/90 | 10-05-91 | 6688 | 36316 | 5.43![]() |
3C 111 | 0.048 | 32.61 | 02/89 | 13-02-93 | 2322 | 1001 | 0.43![]() |
Note: (1) Galactic column density in units of ;
(2) in s.; (3) in counts/s.
Obj. | ![]() | ![]() |
![]() | ![]() | ![]() | |
Mkn 335 | 6.70![]() | 3.88![]() | 3.01![]() | 1.52/176 | 2.39![]() | |
Fairall-9 | 11.4![]() | 2.97![]() | 2.46![]() | 1.04/186 | 1.94![]() | |
NGC 3783 | 9.14![]() | 10.0![]() | 2.79![]() | 17.5/111 | 2.11![]() | |
NGC 4051 | 2.24![]() | 1.79![]() | 2.84![]() | 1.66/174 | 1.84![]() | |
MCG 6-30-15 | 8.73![]() | 4.83![]() | 2.23![]() | 2.46/189 | 2.12![]() | |
Mkn 841 | 5.28![]() | 2.28![]() | 2.42![]() | 1.25/187 | 2.30![]() | |
3C 390.3 | 5.63![]() | 6.33![]() | 1.89![]() | 1.15/177 | 1.86![]() | |
NGC 7469 | 8.63![]() | 5.82![]() | 2.29![]() | 1.03/199 | 1.97![]() | |
Akn 120 | 9.13![]() | 10.2![]() | 2.53![]() | 0.93/199 | 1.93![]() | |
NGC 5548 | 4.56![]() | 1.33![]() | 1.94![]() | 1.84/196 | 1.81![]() | |
Mkn 509 | 17.7![]() | 3.93![]() | 2.63![]() | 0.96/158 | 1.86![]() | |
NGC 3516 | 15.6![]() | 2.78![]() | 2.15![]() | 3.28/208 | 2.08![]() | |
IC 4329A | 23.2![]() | 23.5![]() | 1.30![]() | 0.92/197 | 2.03![]() | |
MCG 2-58-22 | 3.59![]() | 3.51![]() | 2.11![]() | 0.96/183 | 1.67![]() | |
NGC 7213 | 15.8![]() | 2.15![]() | 2.14![]() | 1.55/195 | 1.96![]() | |
Note: (1) Power law flux at 1 keV in units of
keV-1
(2) Neutral column density in units of
(3) Best fit power law index with reflection and warm absorber included.
Of all these 17 sources we have then analized the PSPC (Pfeffermann et al. 1987) observations in the ROSAT (Trümper 1983) public archive. In case of repeated pointings we have selected the longest observation, because we are primarily interested in the spectral properties. The log book of the ROSAT observations can also be found in Table 1 (click here).
Data of each observation were analyzed using the EXSAS package (Zimmermann et al. 1994). After examination of the image to exclude serendipitous sources that may contaminate source and background extraction regions, source spectra were extracted from a circular region of 3 arcmin radius. The background was computed in an annulus between 3.5 and 7 arcmin. The date of observation, exposure times, total source counts and count rates are listed in Table 1 (click here). For each source we produced a 256 channel pulse-invariant (PI) spectrum. We ignored PI channels 1-11 (E<0.1 keV) and above 235 (E>2.36 keV) and rebinned the remaining channels in order to have a signal to noise ratio in each bin of at least 7. We have added systematic errors of 2% to account for residual calibration uncertainties (ROSAT NEWS No. 10, Aug. 1992). The spectral analysis was performed using the PSPC response matrix released on Mar. 92 for the observations performed before 21 Nov. 1991, and the matrix released on Jan. 1993 for observations performed after that date.
In order to have adequate statistics for spectral analysis, particularly below 1 keV, we have further selected objects with ROSAT PSPC total counts greater than 2000 cts and absorption column density lower than 1021 cm-2. Two objects do not satisfy the first requirement (Table 1 (click here) ): NGC 4593 and 3C 111. As for the second selection criterion, we present in Table 2 (click here) the results of the simple power law fits to the 15 remaining objects. One object, IC 4329A, has an absorbing column in excess of 1021 cm-2: the final sample is therefore composed of 14 objects, with total counts comprised between 12.000 and 65.000 cts.
Hereinafter all the errors refer to a 90% confidence level for one interesting parameter.