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A fraction of the heavily reddened quasars require a reddening curve which iseven steeper than that of the Small Magellanic Cloud. In this paper, wethoroughly characterize the anomalously steep reddening law in quasars, via anexceptional example observed in IRAS 14026+4341. By comparing the observedspectrum to the quasar composite spectrum, we derive a reddening curve in therest-frame wavelength range of 1200 {\AA}--10000 {\AA}. It is featured with asteep rise at wavelengths shorter than 3000 {\AA}, but no significant reddeningat longer wavelengths. The absence of dust reddening in optical continuum isconfirmed by the normal broad-line Balmer decrement (the H$\alpha$/H$\beta$ratio) in IRAS 14026+4341. The anomalous reddening curve can be satisfactorilyreproduced by a dust model containing silicate grains in a power-law sizedistribution, $dn(a)/da \propto a^{-1.4}$, truncated at a maximum size$a_{max}=70 {\rm nm}$. The unusual size distribution may be caused by thedestruction of large "stardust" grains by quasar activities or a different dustformation mechanism (i.e., the in situ formation of dust grains in quasaroutflows). It is also possible that the analogies of the dust grains observedtoward the Galactic center is responsible for the steep reddening curve. Inaddition, we find that IRAS 14026+4341 is a weak emission-line quasar (i.e.,PHL 1811 analogies) with heavy dust reddening and blueshifted broad absorptionlines.

Anomalously Steep Reddening Law in Quasars: An Exceptional Example Observed in IRAS14026+4341