Date and Time of the Query: 2022-01-20 T14:35:57 PST
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Notes for object MRK 0501

22 note(s) found in NED.

1. 2004ApJS..155...33S
Re:VSOP J1653+3945
(Mrk 501) The GOT image for this source can be found in Edwards
et al. (2000).

2. 2003ApJS..146....1W
Re:MRK 0501
Mrk 501.-This is one of nine sight lines where O VI absorption is
detected at velocities where complex C is seen in H I. However, in this
direction, the IVC complex K is also present. It is not clear at which
velocity to separate the Galactic and HVC component. A choice was made
to cut at a velocity of -100 km s^-1^, which is also about where the
complex C and K components can be separated in H I.
The sight line also passes through the Draco Galaxy Grouping
(v = 1120 +- 390 km s^-1^), as well as through grouping 70, whose
galaxies have v = 2320 +- 400 km s^-1^. No intergroup Ly{beta} is seen.
Note the feature at 1035.596 {angstrom} (60 +- 15 m{angstrom}) It cannot
be Ly{beta} since there is no corresponding Ly{alpha} line in the GHRS
spectrum. It is most likely C II at a velocity of -215 km s^-1^. The
nearest H I with similar velocities are parts of complex C that lie
about 5deg away (N(H I) 2 x 10^11^ cm^-2^). If it iS C II in complex C,
the corresponding H I column density would also be about
2 x 10^18^ cm^-2^ (assuming a b-value > 10 km s^-1^).

3. 2003A&A...400...95N
Re:RGB J1653+397
1653+397: This object is discussed in more detail in Nilsson et
al. (1999a). Fairly large residuals are seen in the inner part of the
object after subtracting the best-fitting free {beta} model.
Gonzles-Serrano & Carballo (2000) report 1653+397 to have disky

4. 2002MNRAS.329..877C
Re:GB6 J1653+3945
185-redshift and spectrum in Marcha et al. (1996).

5. 2001ApJ...552..508G
Re:MRK 0501
1652+39 (Mkn 501). - We also observed this source with the space VLBI
array. Preliminary results have been published in Giovannini et al.
(1998b, 1999b). A more detailed paper is in preparation.

6. 2001ApJ...548..200X
Re:MRK 0501
3.10. Mrk 501 (H1652+398)
Mrk 501 is a nearby (z = 0.031) BL Lac object. This source was
discovered as a TeV {gamma}-ray source by the Whipple Collaboration in
1995. Variability of the order of 20%-40% of the hard X-ray flux was seen
in 1986, and variation appears random on a timescale of a few hours
(Giommi et al. 1990). Optical observations in 1992-1993 by Xie et al.
(1996) show that its intraday "flickering" amplitude is smaller than
0.22 mag (20%) in the B and V bands. The V light curves of Mrk 501 since
1994 March show that the optical variability of this source is slow and
restricted in a range of only a few tenths of magnitude. Our new
observation on 1999 September 17 shows that the intraday variability of
this object is smaller than 0.08 mag in the R band (see Table 2).
During 1995 and 1996 the TeV {gamma}-ray emission was observed to be
substantially constant by the Whipple {gamma}-ray telescope (Quinn et al.
1997) although a small ascending trend is evident. The observations of
our monitoring projects show that the optical emissions of this source are
also substantially constant although some small fluctuations are evident
(see Fig. 10 and Table 2 of Paper I). The observational data of both TeV
{gamma}-ray and optical bands show that direct correlation between the TeV
{gamma}-ray and optical emissions was suggested as 0420-014.

7. 2000ApJS..127...11G
Re:MRK 0501
3.12. PKS 1652+398 (Mrk 501)
Mrk 501 is a member of the 1 Jy (Kuhr et al. 1981) and the Einstein
Slew Survey sample (Elvis et al. 1992) and is a well-known TeV
{gamma}-ray blazar (Bradbury et al. 1997; Aharonian et al. 1997, 1999).
Even though Mrk 501 is a radio-loud blazar, the multifrequency spectrum
of this source is very similar to that of an X-ray-selected BL Lac or
high-energy peaked BL Lac object (HBL) (Ghosh & Soundararajaperumal
1995; Sambruna, Maraschi, & Urry 1996; Kubo et al. 1997). Mrk 501 has
displayed optical variability on timescales of weeks (Heidt & Wagner
1996). To search for rapid variability on timescales of minutes to
hours, we have carried out V-band CCD differential photometric
observations of this blazar on 10 nights between 1997 March and June, at
the VBO. In total, we obtained 72 CCD frames of Mrk 501 of 6.5 x 10^4^ s
exposure (Table 2). This blazar displayed rapid variability on seven
nights. Figure 10a shows the differential magnitude variation of Mrk 501
that was observed on 1997 March 16. The top and middle panels show the
differential magnitude between Mrk 501 and the two comparison stars, S1
and S2. The bottom panel displays the differences in magnitude between
the two comparison stars. It can be seen from this figure (top and
middle) that the brightness of this source decreased and increased by
around 0.13 +/- 0.02 mag in the interval of 14 and 12 minutes,
respectively. Figure 10b shows that this blazar was not very active
(only 0.04 mag variation in 29 minutes and then remained almost steady)
until it displayed rapid variability on 1997 April 29. Figure 10c
displays the brightness variation of this source by 0.08 mag in 12
minutes, on 1997 June 1. Here we do not present the results of seven
other nights that were very similar to the results presented in
Figures 10a-10c. Figure 10a shows large amplitude (0.13 +/- 0.02 mag)
variation on a short timescale (~ 12 minutes) when Mrk 501 was not in a
flare state (Fig. 10d). This will be a new result, if it is real. Thus
it is important to check the reality of such results that are primarily
based upon a single observational data point. Artificial rapid variations
in brightness can be caused by the variable seeing for an object with an
extended galaxy component. Mrk 501 resides at the center of an extended
host galaxy, and variable seeing may introduce rapid variations similar
to the one presented in Figure 10a. To check the reality of the observed
variability we have carried out photometric analysis using apertures of
4" and 10" diameter rather than the 7" diameter aperture that was used
earlier. We obtained rather than similar results (0.11 +/- 0.02 mag
variability) using the variable aperture photometry.

8. 2000ApJS..127...11G
Re:MRK 0501
Also, we have carried out another test to check the results
presented in Figure 10a. On the night of 1997 March 16, we obtained
observations of 11 CCD image frames of Mrk 501 and Figure 10a shows the
plot of these results. It may be seen from this figure that the first
and last three CCD frames did not display any variations of Mrk 501.
Using these six frames, we created an average image frame and then
subtracted this frame from all the aligned CCD image frames. Then the
subtracted CCD image frames were used for photometry and we obtained the
similar light curve that is shown in Figure 10a. We also obtained
similar type of light curve of Mrk 501 from our observations that were
carried out on 1997 May 2 (around 0.1 mag in 22 minutes).
Similar type of variability (decrease and increase of brightness on
timescales of minutes) of other blazars has also been reported by
different authors (Bai et al. 1998; Guibin et al. 1998 and references
therein). Based on all these results, we will consider that the rapid
variations detected in Mrk 501 (Figs. 10a-10c) are real and not due to
the artifact of seeing. Significance of these variations will be
discussed in the next section.

9. 2000A&AS..145....1P
Re:[HB89] 1652+398
1652+398: In this BL Lac object (z=0.034), very slow and weak flux
variations appear. Its modulation index is 3% at 11 cm, then increases
with decreasing wavelength;

10. 1999ApJS..121..131F
Re:B3 1652+398
B2 1652+398 was shown to have a redshift of 0.0337 by Ulrich et al.
(1975). It has effective spectral indices similar to those of X-ray
-selected BL Lac objects but has been classified as an RBL. The largest
optical variation of 1.3 mag (Stickel et al. 1993) is smaller than that
in J. Its optical and infrared emissions are polarized at P_opt_ =2%-7%
and P_IR_ =3% (CH84). During the flare, the colors are found to be very
much bluer than in the quiescent state, reaching (H-K)=0.13 and
(J-H)=0.48 (Takalo et al. 1992), but there are almost no correlations
between the color index and the magnitude or for the color-color indices
(see Fig. 18).

11. 1999A&AS..139..601C
Re:[HB89] 1652+398
1652+398: Kollgaard et al. (1992) find a diffuse emission at 5 GHz which
is in agreement with the 75" wide halo we detect in our higher
resolution B array image at 1.36 GHz (Fig. 24). Our 4.88 GHz image shows
instead only a small fraction of the extended emission visible in the
L band.

12. 1999A&AS..136...13F
Re:MRK 0501
Mkn 501, z=0.033, together with other two XBLs are three known TeV
{gamma}-ray sources detected by the Whipple group (see Quinn et al.
1996; Catanese et al. 1997a; Samuelson et al. 1998; Kataoka et al.
During 1995 March-July period, Mkn 501 was observed to show a flux of
F(>300 GeV) = (8.1 +/- 1.4) 10^-12^ photon cm^-2^ s^-1^ with a photon
spectral index {alpha}_{gamma}_ = 2.2. A variation of a factor of 4 over
one day is also detected, {DELTA}T_D_ = 6 hrs. The upper limit
corresponds to a flux of F(>100 MeV) = 1.5 10^-7^ photon cm^-2^ s^-1^
(see Quinn et al. 1996). During the 1996 multiwavelength campaign,
Mkn 501 was detected with EGRET a flux of F(>100 MeV) = (0.32 +/- .13)
10^-6^ photon cm^-2^ s^-1^ with a photon index of 1.6 +/- 0.5 (see
Kataoka et al. 1998). During 1997 April 9-19 observation, Catanese
et al. (1997a) obtained F(>300 GeV) = (40.5 +/- 9.6) 10^-11^
photon cm^-2^ s^-1^, {alpha}_{gamma}_ = 2.5, the April 9-15 flux
corresponds to a flux of F(>100 MeV) < 3.6 10^-7^ photon cm^-2^ s^-1^.
The TeV observations show that the spectrum softens when the source

13. 1998AJ....115.1295K
Re:MRK 0501
1652+398.--Mrk 501 has a diffuse twisting jet, which has been studied in more
detail by Conway & Wrobel (1995). A very high energy (E > 300 GeV) gamma-ray
flare was observed in 1997 April (Catanese et al. 1997).

14. 1998A&AS..130..305V
Re:MRK 0501
3.5 Mkn 501
Stars 1 and 2 of our photometric sequence have already been calibrated by Veron
& Veron (1976; their Stars 3 and 2) in the UBV filters and by Smith et
al. (1991; their Stars A and B) in the UBVRI bands. We confirm the results of
the above authors in the BVR filters. Standard VRI magnitudes for Stars 1, 4,
and 6 were published by Fiorucci & Tosti (1996); also in this case there is
accordance among their data and ours. A comparison among calibrations is shown
in Table 4.

15. 1997ApJ...480..547W
Re:MRK 0501
1652+398 (Mrk 501).-This well-known, very low redshift (z = 0.033) BL Lac
is in the "Great Wall" supercluster but not within any rich cluster. The
richness of the region around Mrk 501 corresponds to Abell class <0.

16. 1995ApJS..100...37G
Re:MRK 0501
Mrk 501 is a well-known BL Lac object (Angel & Stockman 1980; Maccagni
et al. 1989; Stickel et al. 1991; Burbidge & Hewitt 1992). It has been
classified as an XBL (Giommi et al. 1990; Hewitt & Burbidge 1993). Mrk
501 was observed on many occasions with EXOSAT. In Table 2 we have listed
only those observations which have signal significance above 4 {sigma}.
Details of X-ray observations of this source with uhuru, ariel5, HEAO 1
and 2, and EXOSAT are given in Staubert et al. (1986a), and EXOSAT and
IUE observations are given in George et al. (1988b) and Edelson et al.
(1992). Correlated variability of the ME count rates with the hardness
ratio of this source was detected from EXOSAT observations (Giommi et al.
1990). This blazar also displayed rapid variability ofthe ME flux on
timescales of hours. To fit the spectra of Mrk 501, we have used
different models, mentioned in Section 4.1. We have found that the power-
law plus absorption model fits these spectra best. Results of the fit
parameters show that Mrk 501 is a steep spectrum (Fig. 2x) source with no
intrinsic absorption (Table 3). The multifrequency spectrum of this XBL
was constructed using simultaneous/quasisimultaneous multifrequency
observations (Mufson et al. 1984; Sembay et al. 1985). This spectrum
(Fig. 4j) can be represented by a single spectral component.

17. 1993ApJS...85..265J
Re:H 1652+398
H 1652+398
This well known BL Lac object (also named Mrk 501 and 4U 1651+39, Schwartz
et al. 1978) is one of the most observed objects in our sample. Polarimetry
has been published by various authors including those presented in Angel &
Stockman (1980). The narrow range of variability of the polarization
position angle had already been noted at that time. Rusk (1988) gives a mean
polarization position angle of 136^deg^ and notes that the VLBI observations
give a position angle of 128^deg^ +/- 5 for the small-scale radio emission.
During our monitoring the mean {theta} was 115^deg^.

18. 1993A&AS...98..393S
Re:MRK 0501
During their survey observations, Markarian & Lipovetski (1974) detected
two emission features in the spectrum of 1652+398 (Mkn 501), which were
identified with [O II] {lambda}3727 and H{alpha} {lambda}6563. Ulrich et
al. (1975), however, observed only the stellar absorption lines of the
host galaxy at a redshift of z = 0.033. In the red part of the spectrum,
Moles et al. (1987) found evidence for several emission lines with no
clear identification and suggested that the strongest line is narrow
H{alpha} {lambda}6563 at a significantly larger redshift than the
corresponding absorption lines of the stellar population of the host
galaxy. Our spectrum, however, shows in addition to the host galaxy
absorption lines only a weak and a strong narrow emission line, which we
identify with H{alpha} {lambda}6563 and [N II] {lambda}6584,
respectively, at the same redshift as the absorption lines of the stellar
population (z = 0.033, see Table 3). No other emission lines, especially
[O I] {lambda}6300, [O III] {lambda}4959,5007 or [O II] {lambda}3727, are
This source is the nearest of the 1 Jy BL Lac objects and thus appears
as a very large galaxy on the direct image. The central point source is
relatively weak compared to those seen in e.g. 1418+546 and 2200+420.

19. 1988ApJ...328..114P
Re:MRK 0501
1652+398 (Markarian 501).-We obtained a good fit to our data with the
three-component core-jet model given in Table 4. Van Breugel and
Schilizzi (1986) observed this galaxy on the European VLBI
network. Their map, which has lower resolution but greater sensitivity
than ours, shows that the jet extends at least 55 mas from the core. In
our data, there are variations in the amplitudes on the US baselines
which suggest that there is a more distant component than those in our
map, in agreement with van Breugel and Schilizzi's results. It is not
clear how the VLBI jet is related to the large-scale radio emission,
which is extended 1deg in P.A. 450 (Ulvestad, Johnston, and Weiler
1983). Observations at 10.7 GHz by Seielstad, Pearson, and Readhead
(1983) show no evidence of variability.
Where necessary, we have assumed H_0_ = 100h km s^-1^ Mpc^-1^ and
q_0_ = 0.5 to convert angles to projected distances.

20. 1986A&AS...64..135P
Re:B2 1652+39A
The source, unresolved, is associated with the N galaxy Mk 501; the
radio spectrum is flat. No map is given in figure 1.

21. 1976RC2...C...0000d
Re:[RC2] A1652+39
= MRK 0501
= 4C 39.49
Bright blue nucleus, extremely compact, but not a Seyfert; no emission.
First described as featureless spectrum.
Ap. J. (Letters), 189, L99, 1974.
Ap. J., 190, 271, 1974.
Ap. J., 192, 581, 1974.
Astr. Ap. Suppl., 20, 1, 1975.

22. 1973UGC...C...0000N
Re:UGC 10599
Several small galaxies near

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