Frankfurt Quasar Monitoring

AU CVn  (B2 1308+32, OP+313)
Object data

  Cross-Identifications   7C 1308+3236, TXS 1308+326, 1ES 1308+326
  B2 1308+32, GC 1308+32, OP 313, US 371
  IRAS F13080+3237, 87GB 130808.6+323654
  2MASSi J1310286+322043, 1AXG J131028+3220
  SDSS J131028.66+322043.7, RX J1310.4+3220
  CSO 836, 2E 2900, FIRST J131028.6+322043
  GALEXASC J131028.69+322044.4, 1308+326
  WMAP J1310+3221, 1FGL J1310.6+3222
  Equat. coordinates   RA  13 10 28.7     DE  +32 20 44     (J2000)
  Constellation   Canes Venatici
  Type   QSO (1)  /  BL Lac (3)
  z=0.997 (1) (3)   /   z=0.998 (2)
  Distance (2) (4)
  3224 Mpc
  Total mag range (mv) (5) (6)   12.9 - 19.6
  Catalog Magnitude   15.24 (1)  /  18.0 g (2)
  Absolute Magnitude (1)   -28.6 MB
  Light Travel-Time (2)   7.515 × 109 yrs
(1) Véron-Cetty & Véron 2006, A&A 455, 776
(2) NASA/IPAC Extragalactic Database
(3) CDS Strasbourg Database
(4) Co-Moving Radial Distance
(5) Literature

(6) FQM

Finding chart

Comparison stars

star  B V Rc Ic
A 13.53 (0.03) 13.05 (0.04)
12.71 (0.04)
12.38 (0.04)
B 13.38 (0.02)
12.73 (0.03)
12.35 (0.03)
12.03 (0.03)
C 14.39 (0.07)
13.58 (0.03)1 13.20 (0.03)1 12.84 (0.03)1
F 14.67 (0.07)
14.31 (0.10)
13.88 (0.20)
13.72 (0.14)
comparison stars from Smith et al. 1985, AJ, 90, 1184
(1) comparison stars from Fiorucci et al. 1998, PASP, 110, 105

Colour chart
Credit: SDSS  /  Size 13´× 13´ /  Chart by S. Karge

Light curve


Latest optical superoutburst in 6/7-2022:

    object       date (UTC)      mag     

1308+326    20220630.001    13.03C
1308+326    20220701.913    12.88C
1308+326    20220701.944    12.95V
1308+326    20220702.728    13.18V
1308+326    20220702.767    12.98V
1308+326    20220703.728    13.16V
1308+326    20220703.830    13.18V
1308+326    20220704.955    12.87C
1308+326    20220705.933    12.95C
1308+326    20220713.727    13.94V
observer: S. Karge; comp. stars A=13.08V, C=13.58V

AU CVn = B2 1308+32 is a variable blazar in the southern-most part of Canes Venatici, close to the constellation Coma Berenices. AU CVn was discovered in 1959 as a variable stellar object on POSS plates. It was classified as a new variable star (CSVS 6997). Since then, it has been cataloged with the designation AU CVn in the GCVS. In 1968, a new radio source (OP+313) was found at the position of AU CVn, which was also cataloged by the Bologna Radio Survey (B2). A faint 19-mag stellar object was identified as the optical counterpart in 1972. In 1977, it was found that both the radio source and the variable star refer to the same object. The extragalactic nature of this variable radio source was proved after the first accurate redshift of AU CVn was determined in 1978 (z=0.997). Since 1984, the new identity of AU CVn has been listed in the GCVS. Initially, the extragalactic object AU CVn was classified as a BL Lac object. In 1992, it was reclassified as a quasar, located at the whopping distance of about 7.5×109 light-years. Today, both classifications for AU CVn, quasar and BL Lac object, can be found in the literature. Besides the radio, this blazar has been known also as a blue emission object (CSO) and as a source of infrared (IRAS, 2MASS), X-rays (1ES, RX, 1AXG) and gamma rays (1FGL).

AU CVn is a large amplitude variable object ranging between v=13m.94 and B=20m.0 (literature). Usually, the object remains faint, so it is a favorite target for CCD observers. Visual observers may only observe this quasar during the rare outbursts. The last bright outbursts occurred in 2002, June/July 2019, May 2022 and the latest superoutburst in early July 2022 with a new optical alltime maximum of 12.9mv (see light curve above). Both CCD observers and visual observers shall use the comparison stars given above. Another sequence was published by Miller et al. (1984

The position of quasar AU CVn lies only a few degrees away from the north galactic pole. Here we have an unobstructed view into the universe, so there is a large number of bright and interesting quasi-stellar objects around to observe. Two bright and variable BL Lac objects are located within some 11° to the WSW in Coma Berenices: W Com and B2 1215+30.
Moving about
19° to the ENE will show another two bright quasi-stellar objects in Bootes. The first one is MRK 478, a bright 14-mag quasar. The second one is PKS 1424+240, a bright and slightly variable 14-mag BL Lacertae object.

For deep sky
observers, the sky in the near vicinity of AU CVn offers two bright and remarkable galaxy pairs. First I like to advise you of NGC 4631 and NGC 4656, a bright interacting pair in Com, some 6° E. NGC 4631 is a slightly distorted edge-on spiral, accompanied by elliptical NGC 4627. NGC 4656 is a more strongly affected spiral, also dubbed the "hockey stick". This galaxy pair is an easy task for telescopes of 8- to 10-inch of aperture.
The second galaxy pair is located in
CVn, some 4.5° N of quasar AU CVn. This pair consists of NGC 5033, a bright and large open arm spiral. Its gravitational partner, NGC 5005, lies only 40´ to the NE, which is a tightly wound 10.5-mag spiral. NGC 5005 also harbours an AGN (S3b) at its centre, which appears as a remarkably bright star-like nucleus.
Do you like to take another deep view into the deep sky? 320 million light-years is O.K. for you? Then sweep your telescope
5° to the south and you will meet Abell 1656, the Coma galaxy cluster. This rich galaxy cluster is dominated by its two 12-mag giant ellipticals NGC 4884 and NGC 4874. In late 2011, a new investigation found out that the supermassive black hole at the centre of NGC 4884 has an incredible  mass of about 10×109 solar masses - one of the most massive yet known.
Finally, do not forget about globular cluster Messier 3, located 7.8° SE in Bootes, an impressive showpiece for medium and large aperture telescopes.

Colla, G., Fanti, C., et al. 1970, A&AS, 1, 281; A catalogue of 3235 radio sources at 408 MHz.
Fan, J.H., Lin, R.G. 2000, ApJ, 537, 101; Optical variability and periodicity analysis for Blazars. I. Light curves for
     radio-selected BL Lacertae objects.
Fiorucci, M., Tosti, G., Rizzi, N. 1998, PASP, 110, 105; VRI Photometry of Stars in the fields of 16 Blazars.
Gabuzda, D.C., Kollgaard, R.I., et al. 1992, ApJ, 410, 39; Is 1308+326 a BL Lacertae object or a quasar?
Gottlieb, E.W., Chaisson, L.J., Liller, W. 1977, IAUC. 3140; B2 1308+32 = CSVS 6997 = OP 313.
Grueff, G., Vigotti, M., 1972, A&AS 6, 1.
Khopolov, P.N., et al. 1984; General Catalogue of Variable Stars, Nauka Publishing House, Moscow.
Kurochkin, N.E. 1959, PZ, 12, 409; New variable stars in SA 57.
Kukarkin, B.V., Kurochkin, N.E. 1977, IAUC 3051; CSVS 6997.
Miller, J.S., French, H.B., et al. 1978; in: Pittsburgh Conf. on BL Lac Objects, p.176.
Miller, H.R., Wilson, J.W., et al. 1984, A&AS, 57, 353; Photoelectric comparison sequences in the fields of
     B2 1308+326 and 1418+54.
Pollock, J.T., Pica, A.J., Smith, A.G., et al. 1979, AJ, 84, 11; Long-term optical variations of 20 violently variable
     extragalactic radio sources.
Puschell, J.J., Stein, W.A., Jones, T.W., et al. 1979, ApJ, 227, L11; B2 1308+326 - Photometry and polarization during
     the outburst of 1978 spring.
Smith, P.S., Balonek, T.J., et al. 1985, AJ, 90, 1184; UBVRI Field Comparison Stars for Selected Active Quasars and
     BL Lacertae Objects.
Steinicke, W.; Katalog heller Quasare und BL Lacertae Objekte; Umkirch 1998.
Steinicke, W.; Extragalactic Objects discovered as variable stars; Umkirch 2000.
Tytler, D., Fan, X.-M. 1992, ApJS, 79, 1; Systematic QSO Emission-Line Velocity Shifts and new unbiased Redshifts.
Usher, P. 1981, ApJS, 46, 117; Faint blue objects at high galactic latitude. I - Palomar Schmidt field centered on
     selected area 57.
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.

© Stefan Karge  /  last obs. 2023-01-13