Russian version

2.6-m Shajn Telescope

General Description

The 2.6-m reflector (ZTSh), named after G.A.Shajn, is the second largest optical telescope in Russia. The telescope was manufactured in 1961 by Leningrad Optical-Mechanical Association (LOMO). The telescope has Prime, Nasmyth, Cassegrain and Coude foci.


Mounting: Equatorial
Main mirror: Paraboloid, D = 2.6 m, F = 10.0 m, material: glass-ceramics (sitall)
Optical systems: Prime focus (F/3.85), Cassegrain (F/16), Nasmyth (F/16), and Coude (F/40)
Complete list of instruments: Spectrograph SPEM in the Nasmyth focus
Spectrograph ASP-14 in the coude focus
Echelle spectrograph in the coude focus (ESPL)
CCD-camera in the primary focus
Click here to overview instruments

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Instruments and detectors for observations of AGNs

At present, the instrumental setup for spectral observations of AGNs includes a modern SPEC-10 CCD and the computer controlled spectrograph ("SPEM" spectrograph) mounted in the Nasmyth focus of the 2.6-m Shajn Telescope. The SPEC-10 CCD has been purchased under US Civilian Research and Development Foundation.


"SPEM" spectrograph mounted in the Nasmyth focus of the 2.6-m Shajn Telescope.
Digits denote: 1 -  Controller of the SPEC-10 CCD camera; 2 - Meade CCD camera to view and to track targets;  3 - Unit to to set title of the grating dispersion unit by steeper engine; 4 - Collimator;
5 - 12V Power supply; 6 - Unit to control the spectrograph;  7 - Wheel to change a position angle;
and  8 - SPEC-10 CCD camera.

Optical scheme of the spectrograph "SPEM".

Readnoise: 1.50 ADU = 2.98 e-
Gain: 1.99 e-/ ADU
QE: 95% Max. at λ 5500Å
Geometry: 1340×100 pixels, 20×20 microns
Well Depth: 262,000 e-
Dynamic resolution: 16 bits, 100 kHz
Cooling: up to -100C, regardless of ambient

Characteristics of the SPEC-10 CCD camera.

Scale: 0.78 arcsec/pixel
Dispersion near Hβ line with grating of 651 gr/mm: 1.86 Å/pixel. 2300Å per frame
Dispersion near Hα line with grating of 651 gr/mm: 1.76 Å/pixel. 2465Å per frame
Spectral resolution with the entrance slit width of
3 arcsec and with grating of 651 gr/mm:
7.5 Å

Characteristics of the  Nasmyth focus spectrograph ("SPEM" spectrograph) with SPEC-10 CCD camera.

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Observations of AGNs

Systematic observations of the emission lines in AGNs were initiated in the CrAO since 1972 by Chuvaev K.K., who is really pioneered spectroscopic monitoring of AGNs  (Pronik & Chuvaev 1972; Chuvaev 1987; Chuvaev 1991). The AGN spectra were obtained with an image intensifier constructed in the USSR and a home-made high-transmission spectrograph (SPEM spectrograph) operating at the Nasmyth focus of the 2.6m telescope. The high sensitivity photographic films were used as detector. Chuvaev continued monitoring AGN spectra with this instrumental setup over 20 years up to 1991.

The CCD observations of AGNs were initiated by V.I. Pronik who had developed a Cassegrain focus spectrograph for this purpose (the Pronik`s spectrograph). The first CCD spectra of AGNs were acquired in February 1988 by V.I. Pronik and S.G. Sergeev. During the next several years CCD observations of AGNs continued on a regular basis (usually once per month). The main target was the NGC 4151 nucleus (e.g., Sergeev 1994).

The experience of these first AGN observations allowed us to identify the key sources of uncertainty in the CCD data (such as the seeing effect, the effect of atmospheric dispersion, etc.) as well as difficulties with the observational technique. As a result, the observation techniques as well as algorithms and software to process AGN spectra have been developed in the early 1990s for CCD observation of AGNs and these have not changed significantly up to the present. And of course, the quality of the CCD spectra has increased significantly.

Intensive spectral monitoring over more than 13 years since November 1991 has been carried out with the SPEM spectrograph and Astro-550 CCD (see Berezin et al. 1991 for the specification of this CCD).  A database containing more than 2500 CCD spectra for more than 20 AGNs was created with this CCD.

Since July 2005, the instrumental setup for spectral observations of AGNs includes a modern SPEC-10 CCD and the computer controlled SPEM spectrograph. More than 1500 spectra of about thirty AGNs are obtained with this CCD.

In the beginning of our AGN monitoring program with CCD, we had no more than one observational set (2-3 nights) per month and the entrance slit width was usually 2.0-2.3 arcsec. Since 1993, the observational rate has been increased up to 2 sets per month and the entrance slit width was set to 3 arcsec. The spectra were registered at the two separate spectral regions near Hβ and Hα lines. The ``extraction window'' was equal to 11 arcsec. The position angle was set to 90 degrees in most cases. Generally, most of the spectra in both spectral regions were obtained with a single exposure within a night, As a rule, four short-time (~5-30 sec) exposures of bright standard stars per each galaxy exposure have been obtained at approximately the same zenith distance. The spectral energy distribution for these stars has been taken from Kharitonov, Tereshchenko, & Knyazeva (1988). The standard star spectra were used to remove telluric absorption features from the AGN spectra as well as to provide the relative flux calibration. Using the standard stars, we have also measured the ``seeing'' defined as FWHM of the cross-dispersion profile on CCD image. The final flux calibration has been carried out by assuming the narrow emission line fluxes to be constant.

Observer room of the 2.6-m Shajn Telescope. Right: the computer to control SPEC-10 CCD camera and Nasmyth focus spectrograph to carry out the spectral observations of AGNs. Left: the computer to control MEADE CCD camera to view the focal plane of the entrance slit and to track targets.

(1) (2) (3) (4) (5) (6) (7) (8) (9)
Target α2000
z Class Number of
1E 0754.6+3928 07:58:00.1 +39:20:29 0.0956 NLS1 39 46 12.6 23.04
3C 120 04:33:11.1 +05:21:16 0.033 Sy1.5 22 49 22.6 20.73
3C 332 16:17:42.7 +32:22:34 0.152 Sy1 2 4 45.4 21.76
3C 390.3 18:42:03.0 +79:46:09 0.0555 Sy1 163 125 32.5 21.63
Ark 120 05:16:10.1 00:08:57 0.0327 Sy1 101 64 13.3 21.81
Ark 564 22:42:39.3 +29:43:32 0.0245 NLS1 96 35 2.9 20.00
Arp 102 B 17:19:14.5 +48:58:50 0.0244 Sy1.2 62 92 1.8 19.07
IZw1 00:53:35.0 +12:41:36 0.061 NLS1 11 52 7.0 22.02
III Zw 2 00:10:31.0 +10:58:28 0.0894 Sy1.2 33 43 15.2 21.72
Mrk 110 09:25:12.9 +52:17:11 0.0354 Sy1.5 3 10 42.3 20.46
Mrk 279 13:53:03.8 +69:18:28 0.0301 Sy1 11 43 24.1 20.98
Mrk 335 00:06:19.5 +20:12:11 0.0258 Sy1.2 21 74 8.8 20.61
Mrk 509 20:44:09.7 10:43:24 0.0345 Sy1 78 55 13.8 22.01
Mrk 590 02:14:33.6 00:46:00 0.0265 Sy1 34 44 4.1 19.98
Mrk 6 06:52:12.3 +74:25:38 0.0190 Sy1.5 216 83 24.9 19.65
Mrk 668 14:07:00.6 +28:27:20 0.0766 Sy1.5 3 17 17.4 21.66
Mrk 704 09:18:26.0 +16:18:20 0.0292 Sy1.2 1 24 10.6 20.33
Mrk 766 12:18:26.7 +29:48:47 0.0129 NLS1 15 24 3.9 18.94
Mrk 79 07:42:32.8 +49:48:35 0.0216 Sy1.2 2 43 16.3 20.00
NGC 1275 03:19:48.2 +41:30:42 0.0176 Sy1.5? 63 54 4.0 20.50
NGC 3227 10:23:30.6 +19:51:56 0.00345 Sy1.5 74 62 6.6 16.85
NGC 3516 11:06:47.4 +72:34:07 0.0088 Sy1.5 6 56 15.7 19.34
NGC 4051 12:03:09.6 +44:31:53 0.00201 NLS1 68 101 5.8 15.67
NGC 4151 12:10:31.1 +39:24:31 0.00320 Sy1.5 407 106 32.1 17.99
NGC 4593 12:39:38.5 05:20:50 0.0090 Sy1 15 17 12.7 18.91
NGC 5548 14:17:59.6 +25:08:13 0.0168 Sy1.5 341 114 13.6 19.56
NGC 6814 19:42:40.5 10:19:10 0.0052 Sy1.5 4 40 12.5 17.00
NGC 7469 23:03:15.6 +08:52:26 0.0161 Sy1.5 208 97 8.4 20.32
NGC 7603 23:18:56.7 +00:14:38 0.0293 Sy1 54 66 13.7 21.64
OX 169 21:43:35.6 +17:43:49 0.211 Sy1 1 7 6.7 23.37

Statistics for the spectral observations of AGNs. Given are only the targets that were observed on a regular basis. The number of nights of observations for each target is given in the following columns: (6): spectral observations with the Astro-550 CCD in 1991–2005; (7): spectral observations with the SPEC-10 CCD in 2005–2009.

Main window of the program for spectral observations.

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Scientific results on AGNs

The program of the spectroscopic observations of the selected AGNs in the CrAO has the three major goals:

  1. The reverberation mapping studies, i.e., determination the size, geometry, and kinematics of the broad-line region (BLR), as well as masses of the central black holes from the time delay between line and continuum flux variations.
  2. Study the long-term evolution of the broad line profiles in order to evaluate the reasons for this evolution and to obtain observational limitations on the BLR models.
  3. Study observed correlations between variability of the continuum flux in different spectral ranges in terms of a widely accepted model in which the optical and ultraviolet radiation of AGNs are caused by X-rays heating. The spectral observations are a support for the X-ray observations and for the broad-band optical photometry.

The Crimean reverberation program is generally intended for the AGNs with a moderate or high absolute luminosity, for which a temporal resolution of order ten days is sufficient to determine the time lag. However, to obtain reliable lag estimates, especially for the low-luminosity AGNs, the international cooperation is strongly required. The Crimean observatory participates in the international programs of spectroscopic and photometric monitoring of AGNs (such as AGN Watch, see Peterson et al. 2002; Denney et al. 2010 for example). The Crimean team takes part in the determination the sizes and masses in total of nine AGNs (e.g., Denney et al. 2010). For Mrk 6 (Sergeev et al. 1999a, 1999b; Doroshenko 2012) and 1E 0754.6+3928 (Sergeev et al. 2007) the sizes and masses have been determined for the first time, and by the efforts of the Crimean team only. Our reverberation results on 3C 390.3 suggests even larger black hole mass to its nucleus and, therefore, lower accretion rate than was previously thought and thus provides more evidence for anti-correlation between broad line widths and Eddington luminosity ratios (Sergeev et al. 2011). The reverberation BLR sizes and black hole masses allow to establish the most important relationships for AGNs: the size-luminosity and the mass-luminosity diagrams (Peterson et al. 2004; Bentz et al. 2009). These relationships are often considered in the frame of the AGN models. A link between the Hβ equivalent width, profile width, the BLR size and optical continuum luminosity have been investigated from a small sample of well studied AGNs (Sergeev et al. 1999b). The radius-luminosity relation of r ~L0.7 and the mass-luminosity relation L~M1.9 have been claimed. Also, it was found a Baldwin effect in the Hβ line. Several attempts have been undertaken by the Crimean team in order to understand the long-term evolution of the broad line profiles. An explanation of this evolution in NGC 4151 has been given in terms of the multicomponent BLR which produces the two-component line profiles (Sergeev et al. 2001). For Arp 102 B, the BLR was represented by a high number of gas clouds rotating predominantly in the same plane. This model explains double-peaked profiles of the Balmer lines as well as a drift motion of emission details along the line profile (Sergeev et al. 2000). A difference in the line-continuum lag among various line-of-sight velocities of the Hβ profile was found in Mrk 6. This difference is consistent with the virialized motion of BLR gas combined with the radial infall component (Sergeev et al. 1999a; Doroshenko et al. 2012). The important results for the NGC 4151, NGC 5548, Mrk 6, 3C 390.3, and Ark 120 nuclei concerned the line continuum correlation were obtained by Sergeev et al. (1994, 1999a, 2001, 2011), Malkov et al. (1997), Doroshenko et al. (2008, 2012). It was shown that the responsivities of the emission lines to the continuum flux changes undergone long-term changes, and the responses of the Hβ, Hα, and He II 4686Å emission lines are significantly different. Perhaps emission-line responsivities to the continuum events of different durations are different as well.

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