J/A+A/486/99 Long-term spectral variability of NGC 4151 (Shapovalova+, 2008)
Long-term variability of the optical spectra of NGC 4151.
I. Light curves and flux correlations.
Shapovalova A.I., Popovic L.C., Collin S., Burenkov A.N., Chavushyan V.H.,
Bochkarev N.G., Benitez E., Dultzin-Hacyan D., Kovacevic A., Borisov N.,
Carrasco L., Leon-Tavares J., Mercado A., Valdes J.R., Vlasuyk V.V.,
Zhdanova V.E.
<Astron. Astrophys. 486, 99 (2008)>
=2008A&A...486...99S 2008A&A...486...99S
ADC_Keywords: Active gal. nuclei ; Galaxies, spectra
Keywords: galaxies: active - galaxies: individual: NGC 4151
Abstract:
Results of a long-term spectral monitoring of the active galactic
nucleus of NGC 4151 are presented (11 years, from 1996 to 2006).
High quality spectra (S/N>50 in the continuum near Hα and
Hβ) were obtained in the spectral range ∼4000 to 7500Å, with a
resolution between 5 and 15 Å, using the 6-m and the 1-m SAO's
telescopes (Russia), the GHAO's 2.1-m telescope (Cananea, Mexico), and
the OAN-SPM's 2.1-m telescope (San-Pedro, Mexico). The observed fluxes
of the Hα, Hβ, Hγ and HeIIλ4686 emission lines
and of the continuum at the observed wavelength 5117Å, were
corrected for the position angle, the seeing and the aperture effects.
We found that the continuum and line fluxes varied strongly (up to a
factor 6) during the monitoring period. The emission was maximum in
1996-1998, and there were two minima, in 2001 and in 2005. As a
consequence, the spectral type of the nucleus changed from a Sy1.5 in
the maximum activity state to a Sy1.8 in the minimum state. The
Hα, Hγ and Heλ4686 fluxes were well correlated with
the Hβ flux. The line profiles were strongly variable, showing
changes of the blue and red asymmetry. The flux ratios of the blue/red
wings and of the blue (or red) wing/core of Hα and Hβ
varied differently. We considered three characteristic periods during
which the Hβ and Hα profiles were similar: 1996-1999,
2000-2001 and 2002-2006. The line to continuum flux ratios were
different; in particular during the first period (1996-2001), the
lines were not correlated with the continuum and saturated at high
fluxes. In the second and third period (2002-2006), where the
continuum flux was small, the Hα and Hβ fluxes were well
correlated to the continuum flux, meaning that the ionizing continuum
was a good extrapolation of the optical continuum. The CCFs are often
asymmetrical and the time lags between the lines and the continuum are
badly defined indicating the presence of a complex BLR, with
dimensions from a 1 to 50 light-days.
We discuss the different responses of Hβ and Hα to the
continuum during the monitoring period.
Objects:
------------------------------------------------
RA (2000) DE Designation(s)
------------------------------------------------
12 10 32.6 +39 24 20.6 NGC 4151 = UGC 7166
------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 60 220 Log of the spectroscopic observations
table3.dat 36 8 Corrections for the position angle effect
table45.dat 94 12 Correction for seeing effects
table7.dat 66 220 Observed continuum, Hα, Hβ, Hγ
and HeII{4686} fluxes, reduced to the 6m
telescope aperture (2"x6")
--------------------------------------------------------------------------------
See also:
J/AZh/71/189 : Gas Kinematics from Halpha line in NGC 4151 (Sergeev, 1994)
J/A+A/324/904 : NGC 4151 line-continuum diagram sequences (Malkov+ 1997)
J/PAZh/25/403 : Optical variability of NGC 4151 (Lyuty+, 1999)
J/PAZh/27/83 : Nuclear activity of NGC 4151 in 1989-2000 (Doroshenko+, 2001)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 "DD/MM/YYYY" ObsDate UT-date of the observation
12- 20 F9.1 d JD Julian Date
22- 26 A5 --- Tel Code assigned to each telescope+equipment (1)
28- 30 F3.1 arcsec AperW The projected spectrograph entrance
apertures (Slit Width)
32- 36 F5.2 arcsec AperL The projected spectrograph entrance
apertures (along Slit)
38- 41 I4 0.1nm lam1 Lower wavelength of the spectral range
42 A1 --- --- [-]
43- 46 I4 0.1nm lam2 Upper wavelength of the spectral range
48- 51 F4.1 0.1nm Res Spectral resolution
53- 55 I3 deg PA ? Slit position angle
57- 60 F4.2 arcsec Seeing ? Mean seeing
--------------------------------------------------------------------------------
Note (1): Codes as follows:
L(N) = SAO (Russia), Inst.: 6m+Long slit, Focus: Nasmith
L(U) = SAO (Russia), Inst.: 6m+UAGS, Focus: Prime
L(S) = SAO (Russia), Inst.: 6m+Scorpio, Focus: Prime
GH = Gullermo Haro(Mexico), Inst.: 2.1m+B&C, Focus: Cassegrain
S-P = San-Pedro(Mexico), Inst.: 2.1m+B&C, Focus: Cassegrain
L1(G) = SAO (Russia), Inst.: 1m+GAD, Focus: Cassegrain
L1(U) = SAO (Russia), Inst.: 1m+UAGS+CCD2K, Focus: Cassegrain
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 deg PA Slit position angle in degrees
5- 7 F3.1 arcsec AperW The projected spectrograph entrance
apertures (Slit Width)
9- 12 F4.1 arcsec AperL The projected spectrograph entrance
apertures (along Slit)
14- 18 F5.3 --- kp(Hβ) Slit position angle corrections
for emission lines (Hβ) (1)
20- 24 F5.3 --- e_kp(Hβ) ? Estimated PA correction error
for emission line
26- 30 F5.3 --- kp(cnt) Position angle (PA) corrections (1)
for continuum flux
32- 36 F5.3 --- e_kp(cnt) ? Estimated PA correction error
for continuum flux
--------------------------------------------------------------------------------
Note (1): correction in the flux depending on the position angle of
the slit k = F(90)/F(i) (see section 2.3 of paper)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table45.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 F3.1 arcsec SeeingL ? Lower value of the interval of seeings
4 A1 --- --- [-]
5- 7 F3.1 arcsec SeeingU ? Upper value of the interval of seeings
9- 12 F4.2 arcsec Seeing ? Mean seeing
14- 18 F5.3 --- ksHb ? Our seeing correction for the emission
lines flux (Hβ)
21- 30 A10 --- apksHb Aperture for ksHb
33- 37 F5.3 --- e_ksHb ? Estimated seeing correction error
39- 43 F5.3 --- ksHbP ? Peterson's seeing correction for the
emission lines flux (Hβ) (2)
46- 52 A7 --- apksHbP Aperture for ksHP
54- 59 F6.3 10-16W/m2/nm Gs ? Our host galaxy seeing correction for
the continuum flux (1)
62- 71 A10 --- apGs Aperture for Gs
74- 78 F5.3 10-16W/m2/nm e_Gs ? Estimated host galaxy seeing
correction error (1)
80- 85 F6.3 10-16W/m2/nm GsP ? Peterson's host galaxy seeing
correction for the continuum flux (2)
88- 94 A7 --- apGsP Aperture for GsP
--------------------------------------------------------------------------------
Note (1): In units of 10-14erg/s/cm2/Å
Note (2): Peterson et al., 1995PASP..107..579P 1995PASP..107..579P
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.1 d JD Julian date
11- 15 F5.2 10-16W/m2/nm F(cont) Continuum flux at 5117Å (2)(1)
17- 20 F4.2 10-16W/m2/nm e_F(cont) Estimated continuum flux error (2)
22- 26 F5.2 fW/m2 F(Ha) ? Hα total flux (3)
28- 31 F4.2 fW/m2 e_F(Ha) ? Hα flux error (1)(3)
33- 37 F5.2 fW/m2 F(Hb) ? Hβ total flux (3)
39- 42 F4.2 fW/m2 e_F(Hb) ? Hβ flux error (3)
44- 48 F5.3 fW/m2 F(Hg) ? Hγ total flux (1)(3)
50- 54 F5.3 fW/m2 e_F(Hg) ? Hγ flux error (3)
56- 60 F5.3 fW/m2 F(HeII) ? HeIIλ4686Å total flux (1)(3)
62- 66 F5.3 fW/m2 e_F(HeII) ? HeIIλ4686Å flux error (3)
--------------------------------------------------------------------------------
Note (1): The fluxes are corrected for position angle (to PA=90°),
seeing and aperture effects.
Note (2): In units of 10-14erg/s/cm2/Å
Note (3): In units of 10-12erg/s/cm2
--------------------------------------------------------------------------------
Acknowledgements:
Alexander Burenkov, ban(at)sao.ru
(End) Alexander Burenkov [SAO RAS], Patricia Vannier [CDS] 08-Jul-2008