Exploratory ASCA observations of broad absorption line quasi-stellar objects

S. C. Gallagher, William Nielsen Brandt, R. M. Sambruna, S. Mathur, N. Yamasaki

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Abstract

We present the analysis and interpretation of a sample of eight ASCA observations of broad absorption line quasi-stellar objects (BALQSOs). This is the first moderate-sized sample of sensitive BALQSO observations above 2 keV, and the BALQSOs in our sample are among the optically brightest known (B = 14.5-18.5). Despite the ability of 2-10 keV X-rays to penetrate large column densities, we find BALQSOs to be extremely weak sources above 2 keV, and we are only able to add two new 2-10 keV detections (0226-104 and IRAS 07598+6508) to those previously reported. By comparison with non-BALQSOs of similar optical continuum magnitudes, we derive the column densities needed to suppress the expected X-ray fluxes of our BALQSOs. In several cases we derive column densities ≳5 × 1023 cm-2 for a neutral absorber with solar abundances. These are the largest X-ray column densities yet inferred for BALQSOs, and they exceed ROSAT lower limits by about an order of magnitude. Optical brightness does not appear to be a good predictor of 2-10 keV brightness for BALQSOs, but our data do suggest that the BALQSOs with high optical continuum polarizations may be the X-ray-brighter members of the class. For example, the highly polarized object PHL 5200 appears to be unusually X-ray bright for a BALQSO given its optical magnitude. We discuss the implications of our results for future observations with AXAF and XMM. If the objects in our sample are representative of the BALQSO population, precision X-ray spectroscopy of most BALQSOs will unfortunately prove difficult in the near future.

Original languageEnglish (US)
Pages (from-to)549-555
Number of pages7
JournalAstrophysical Journal
Volume519
Issue number2 PART 1
StatePublished - Jul 10 1999

Fingerprint

x rays
brightness
X Ray Astrophysics Facility
continuums
Infrared Astronomy Satellite
XMM-Newton telescope
X-ray spectroscopy
absorbers
polarization
predictions
spectroscopy
detection
analysis
comparison

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Gallagher, S. C., Brandt, W. N., Sambruna, R. M., Mathur, S., & Yamasaki, N. (1999). Exploratory ASCA observations of broad absorption line quasi-stellar objects. Astrophysical Journal, 519(2 PART 1), 549-555.
Gallagher, S. C. ; Brandt, William Nielsen ; Sambruna, R. M. ; Mathur, S. ; Yamasaki, N. / Exploratory ASCA observations of broad absorption line quasi-stellar objects. In: Astrophysical Journal. 1999 ; Vol. 519, No. 2 PART 1. pp. 549-555.
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Gallagher, SC, Brandt, WN, Sambruna, RM, Mathur, S & Yamasaki, N 1999, 'Exploratory ASCA observations of broad absorption line quasi-stellar objects', Astrophysical Journal, vol. 519, no. 2 PART 1, pp. 549-555.

Exploratory ASCA observations of broad absorption line quasi-stellar objects. / Gallagher, S. C.; Brandt, William Nielsen; Sambruna, R. M.; Mathur, S.; Yamasaki, N.

In: Astrophysical Journal, Vol. 519, No. 2 PART 1, 10.07.1999, p. 549-555.

Research output: Contribution to journalArticle

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N2 - We present the analysis and interpretation of a sample of eight ASCA observations of broad absorption line quasi-stellar objects (BALQSOs). This is the first moderate-sized sample of sensitive BALQSO observations above 2 keV, and the BALQSOs in our sample are among the optically brightest known (B = 14.5-18.5). Despite the ability of 2-10 keV X-rays to penetrate large column densities, we find BALQSOs to be extremely weak sources above 2 keV, and we are only able to add two new 2-10 keV detections (0226-104 and IRAS 07598+6508) to those previously reported. By comparison with non-BALQSOs of similar optical continuum magnitudes, we derive the column densities needed to suppress the expected X-ray fluxes of our BALQSOs. In several cases we derive column densities ≳5 × 1023 cm-2 for a neutral absorber with solar abundances. These are the largest X-ray column densities yet inferred for BALQSOs, and they exceed ROSAT lower limits by about an order of magnitude. Optical brightness does not appear to be a good predictor of 2-10 keV brightness for BALQSOs, but our data do suggest that the BALQSOs with high optical continuum polarizations may be the X-ray-brighter members of the class. For example, the highly polarized object PHL 5200 appears to be unusually X-ray bright for a BALQSO given its optical magnitude. We discuss the implications of our results for future observations with AXAF and XMM. If the objects in our sample are representative of the BALQSO population, precision X-ray spectroscopy of most BALQSOs will unfortunately prove difficult in the near future.

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Gallagher SC, Brandt WN, Sambruna RM, Mathur S, Yamasaki N. Exploratory ASCA observations of broad absorption line quasi-stellar objects. Astrophysical Journal. 1999 Jul 10;519(2 PART 1):549-555.