| Frankfurt Quasar Monitoring |
| B2 1147+24 |
| Cross-Identifications | OM+280, TXS 1147+245, S3 1147+24, B2 1147+24 SDSS J115019.21+241753.8, 1FGL J1150.2+2419 7C 1147+2434, GALEXASC J115019.23+241754.3 2E 1147.7+2435, FBQS J115019.2+241753 |
| Equat. coordinates | RA 11 50 19.2 DE +24 17 54 (J2000) |
| Constellation | Leo |
| Type | BL Lac |
| Redshift (2) | z=0.200 |
| Distance (2) (3) |
791 Mpc |
| Total mag range (mv) (4) | 13.7 - 17.0 |
| Catalog Magnitude | 15.74 (1) / 17.57 (2) |
| Absolute Magnitude (1) | --- MB |
| Light Travel-Time (2) | 2.353 × 109 yrs |
| star | V | Rc | Ic |
| C1 | 12.52
(0.05) |
12.18
(0.05) |
11.81
(0.05) |
| C2 | 12.68
(0.05) |
12.32
(0.05) |
11.94
(0.05) |
| C3 | 13.13
(0.05) |
12.78
(0.06) |
12.47
(0.06) |
| C4 | 13.68
(0.06) |
13.18
(0.06) |
12.64
(0.06) |
| B2 1147+24 (= OM
280) is a variable BL Lac object in north-eastern Leo, close to
the constellation Coma Berenices. B2 1147+24 was
discovered as a flat-spectrum radio source in the late 1960s by the
Bologna Radio Survey (B2) and the Ohio Radio Survey (OM). Since then,
it has
been catalogued by various other radio surveys. Spectroscopic
investigations during the mid 1970s revealed a continuous
spectrum. Together with its optical polarization it was classified as a
BL Lac object. Despite its
featureless spectrum, a redshift of z=0.200 was derived from the fact,
that the source is optically unresolved, suggesting z > 0.2. The FR2
radio
morphology also suggests that it is a high-z object. That is why no
redshift is given in the quasar catalogs
by Véron-Cetty & Veron (2001-2010). B2 1147+24 is a variable object with a total optical range of about 3 magnitudes. CCD observers, as well as visual observers, shall use the comparison stars given above. The comparison stars C1=12.52 and C2=12.68 are recommended for both unfiltered and v-mag photometry. B2 1147+24 remains about mag-16 for most of the time, so visual observers need at least a 14- to 16-inch telescope to glimpse this stellar object. ____________
Observers who like to continue their observing
session with more quasi-stellar photons may turn to quasar PG 1116+215, a bright 14-mag object at a distance of
about 2×109 light-years, 7.7° WSW of B2:1147+24. Another
highly variable BL Lac object is W Com,
located 8° NE. About 6° E of B2 1147+24 we find the naked eye open cluster Mel 111, the Coma Cluster, as well as some bright galaxies of the Coma I-cluster, like NGC 4565, NGC 4494 and NGC 4559. Visual observers may also like to take a look at two loose galaxy groups in western Leo: The NGC 3607-galaxy group (10° SW) and the NGC 3684-galaxy group (8.8° SW). Finally, rich galaxy cluster Abell 1367 (4.6° SSW), dominated by its cD-galaxy NGC 3842, shall not be missed. |
| Angel, J.R.P., Stockman, H.S. 1980, ARA&A, 18, 321; Optical and infrared polarization of active extragalactic objects. Colla, G., Fanti, C., et al. 1972, A&AS, 7, 1; The B2 Catalogue of radio sources - second part. Dixon, R.S., Kraus, J.D. 1968, AJ, 73, 381; A High-Sensivity 1415 MHz Survey at North Declinations between 19 and 37 degrees. Fiorucci, M., Tosti, G. 1996, A&AS, 116, 403; VRI photometry of stars in the fields of 12 BL Lacertae objects. Fiorucci, M., Tosti, G. 1996, A&AS, 117, 475; Automatic optical monitoring of 10 Blazars. Katajainen, S., Takalo, L.O., et al. 2000, A&AS, 143, 357; Tuorla quasar monitoring I. Observations of 1995-1997. Kinman, T.D. 1976, ApJ, 205, 1; Photoelectric Magnitudes and Polarization Data for possible BL Lacertae Objects. Moles, M., Garcia-Pelayo, J.M., Masegosa, J., Aparicio, A. 1985, ApJS, 58, 255; BVRI observations of BL Lacertae objects. Pica, A.J., Smith, A.G., et al. 1988, AJ, 96, 1215; Long-term optical behavior of 144 compact extragalactic objects - 1969-1988. Rector, T.A., Stocke, J.T. 2001, AJ, 122, 565; The Properties of the Radio-Selected 1 Jy Sample of BL Lacertae Objects. Sowards-Emmerd, D., Romani, R.W., et al. 2005, ApJ, 626, 95; Northern Survey of Gamma-Ray Blazar Candidates. Steinicke, W.; Katalog heller Quasare und BL Lacertae Objekte; Umkirch 1998. Stickel, M., Fried, J.W., Kühr, H. 1993, A&AS, 98, 393; The complete sample of 1 Jy BL Lac objects. II. Véron-Cetty, M.-P., Véron, P. 2001, A&A 374, 92; A Catalogue of Quasars and Active Nuclei: 10th edition. Véron-Cetty, M.-P., Véron, P. 2003, A&A 412, 399; A Catalogue of Quasars and Active Nuclei: 11th edition. Véron-Cetty, M.-P., Véron, P. 2006, A&A 455, 776; A Catalogue of Quasars and Active Nuclei: 12th edition. Véron-Cetty, M.-P., Véron, P. 2010, A&A 518, 10; A Catalogue of Quasars and Active Nuclei: 13th edition. Wills, D., Wills, B.J. 1976, ApJS, 31, 143; Spectroscopy of 206 QSO candidates and radio galaxies. Zekl, H., Klare, G., Appenzeller, I. 1981, A&A, 103, 342; Optical Brightness Variations of BL-Lacertae Objects. |
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