Frankfurt Quasar Monitoring

PKS 1424+240
Object data

  Cross-Identifications   PG 1424+240, TXS 1424+240, B2 1424+24, OQ+240
  KUV 14247+2401, 7C 1424+2401, QSO B1424+240
  PKS 1424+240, RGB J1427+238, 2E 1424.7+2401
  SDSS J142700.39+234800.0, GB6 B1424+2401
  FBQS J142700.4+234800, RX J1427.0+2348
  0FGL J1427.1+2347, RBS 1395, 1424+240
  Equat. coordinates   RA  14 27 00.5     DE  +23 48 00     (J2000)
  Constellation   Bootes
  Type   BL Lac
  Redshift   z=0.160 (2)  /  z>0.603 (5)
  Distance (2) (3)
  638 Mpc
  Total mag range (mv) (4)   14.0 - 18.39
  Catalog Magnitude (1)   14.28
  Absolute Magnitude (1)   ---
  Light Travel-Time   1.930 × 109 yrs (2)  /  >5.5 × 109 yrs (approx.) (6)
(1) Véron-Cetty & Véron 2006, A&A 455, 776
(2) NASA/IPAC Extragalactic Database
(3) Co-Moving Radial Distance
(4) Literature
(5) Furniss et al. (2013)
(6) Frankfurt Quasar Monitoring

Finding chart

Comparison stars

star V Rc Ic
C1 13.59 (0.04)
13.20 (0.04)
12.80 (0.04)
C2 13.70 (0.05)
13.32 (0.05)
12.91 (0.04)
C3 15.91 (0.09)
15.57 (0.08)
15.21 (0.08)
comparison stars from Fiorucci et al. 1996, A&AS, 116, 403

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

Light curve

PKS 1424+240 is a variable stellar object in Bootes, about 1° NE of Arcturus. The designation PKS:1424+240 refers to the Parkes Radio Survey (PKS), where this object was cataloged as a radio source in 1973. PKS 1424+240 was discovered as a radio loud point source by the Ohio Radio Survey (OQ). Independently, it was identified with a blue stellar object by the Palomar-Green Bright Quasar Survey (PG), where this object was initially classified as a white dwarf due to its featureless spectrum. In the 1980s, it was finally identified as an extragalactic object. PKS 1424+240 was classified as a BL Lac object in the 1990s, after X-ray observations were carried out by ROSAT.

Due to the featureless spectrum no accurate redshift has been determined to date. CDS Strasbourg Database, as well as NASA/IPAC Extragalactic Database, published a
(tentativ) redshift of z=0.16 (Aleksić et al. 2011), which is not fully accepted by Véron-Cetty et al. 2001-2010. A recent spectroscopic study found a new redshift lower limit of z>0.6035 (Furniss et al. 2013). This would make PKS 1424+240 the most distant TeV-emitting Blazar ever detected. However, the true distance as well as the absolute luminosity still remain uncertain.

PKS 1424+240 displays large and rapid changes in optical brightness with a total range of about 4 magnitudes. Usually, it is a bright object of about 14 mag. Visual observers need at least an 8- to 10-inch telescope to glimpse this stellar object during bright state. CCD observers, as well as visual observers, shall use the comparison stars given above.

Looking at some interesting objects around PKS 1424+240, we first take a look at RX Boo, a type RR Crb variable some 2° NE, ranging between 8.6-11.3 mag (340d, M6.5-M8).
Another extragalactic variable object is NGC 5548, a well known AGN, some 2.4° to the NW. This type 1 Seyfert galaxy shows a total optical variability ranging between 11.9 mag and 14.3 mag.
Some 12° NNE of PKS 1424+240, bright 14-mag quasar MRK 478 might also attract your interest.
And finally, two other bright 15-mag quasars are located nearby:
MRK 813 can be found about 4° to the south, and PG 1402+261 lies about 5.4° to the west.

Aleksić, J., et al. 2011, ApJ, 729, 115A; Gamma-ray Excess from a Stacked Sample of High- and Intermediate-
     frequency Peaked Blazars Observed with the MAGIC Telescope.
Condon, J.J., Hicks, P.D., Jauncey, D.L. 1977, AJ, 82, 692; Optical identifications of Parkes sources with flat spectra.
Dixon, R., Kraus, J. 1968, AJ, 73, 381; A High-Sensivity 1415 MHz Survey at North Declinations between 19° and 37°.
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.
Fleming, T.A., Green, R.F., et al. 1993, AJ, 106, 1729; Three new BL Lacertae objects in the Palomar-Green survey.
Furniss, A., Williams, D.A., et al. 2013, arXiv:1304.4859; The firm redshift lower limit of the most distant TeV-
     detected Blazar PKS 1424+240.
Green, R., Schmidt, M., Liebert, J. 1986, ApJS, 61, 305; The Palomar Green Catalogue of Ultraviolet-Excess Stellar
Impey, C.D., Tapia, S. 1988, ApJ, 333, 666; New blazars discovered by polarimetry.
Karge, S.; Helle Quasare für 8- bis 10-Zoll Teleskope. Ein Beobachtungsführer zur visuellen Beobachtung von Quasaren
     und BL Lacertae Objekten; Frankfurt 2005.
Katajainen, S., Takalo, L.O., et al. 2000, A&AS, 143, 357; Tuorla quasar monitoring. I. Observations of 1995-1997.
Mead, A.R.G., Ballard, K.R., et al. 1990, A&AS, 83, 183; Optical and infrared polarimetry and photometry of blazars.
Scarpa, R., Falomo, R. 1995, A&A, 303, 656; Spectral energy distribution of Palomar-Green BL Lacertae objects.
Scarpa, R., Falomo, R. 1997, A&A, 325, 109; Are high polarization quasars and BL Lacertae objects really different?
     A study of the optical spectral properties.
Shimmins, A.J., Bolton, J.G., Wall, J.V. 1975, AuJPA, 34, 63; The Parkes 2700 MHz Survey (Tenth Part): Supplementary
     Catalogue for the Declination zone +4° to +25°.
Steinicke, W.; Beobachtungsliste für helle Quasare; Umkirch 1999.
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.



Landessternwarte Heidelberg

Sloan Digital Sky Survey

© Stefan Karge  /  last obs. 2023-01-18