XMM-Newton Observation of the Second Brightest Quasar PHL 1811

Details XMM-Newton Observation of the Second Brightest Quasar PHL 1811 XMM-Newton Observation of the Second Brightest Quasar PHL 1811

May 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005aas...206.1112c&link_type=abstract

American Astronomical Society Meeting 206, #11.12; Bulletin of the American Astronomical Society, Vol. 37, p.447

Astronomy and Astrophysics

Astronomy

2

Scientific paper

Follow-up spectroscopy of VLA FIRST survey quasar candidates discovered the very bright quasar, PHL 1811 (z=0.192, B=14.4, R=14.1), in the South Galactic Cap; it is the second brightest quasar beyond z=0.1 after 3C 273. Strangely, this quasar was not detected in the ROSAT All Sky Survey. Follow-up BeppoSAX, then coordinated HST and Chandra observations showed that it is very X-ray weak. The inferred α ox from the HST and Chandra observations was -2.4 to -2.2. The X-ray spectrum was steep and the flux varied between two Chandra observations implying that the X-ray emitting region was not absorbed but rather the quasar is intrinsically X-ray weak, pointing to unusual and extreme conditions in the X-ray emitting corona.
We observed PHL 1811 with XMM-Newton on November 1, 2004. The two MOS and PN detectors yielded 1100 photons in the 0.2--5 keV band. The flux was comparable to the Chandra observations; the object is still X-ray weak. Assuming Galactic absorption column of 3.73 × 1020 cm-2, we obtained a good fit with a power-law model. The photon index is 2.32 ± 0.11, typical for a Narrow-line Seyfert 1 galaxy. The upper limit on absorption in the host galaxy is 4.6 × 1020 cm-2 (90% confidence for one parameter of interest); there is no evidence of intrinsic absorption. We found no evidence of X-ray variability in the 30 ks observation. Using the OM UVM2 filter we found that the UV flux at 2310Å/ is 2.52× 10-14 erg cm-2} s{-1Å/-1. This value is comparable to the flux obtained during the December 2001 HST observation.
PHL 1811 has now been observed in X-rays five times over period of 14 years. In each observation it is X-ray weak and there is no evidence for X-ray absorption. We conclude PHL 1811 is an unusual intrinsically X-ray weak quasar.

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