We present Spitzer Space Telescope infrared spectroscopic and photometric observations and McDonald Observatory Smith Telescope and Anglo-Australian Telescope high spectral resolution optical observations of 4 nearby stars with variable or anomalous optical absorption , likely caused by circumstellar material .
The optical observations of Ca ii and Na i cover a 2.8 year baseline , and extend the long term monitoring of these systems by previous researchers .
In addition , mini-surveys of the local interstellar medium ( LISM ) around our primary targets provide a reconstruction of the intervening LISM along the line of sight .
We confirm that the anomalous absorption detected toward \alpha Oph is not due to circumstellar material , but to a small filamentary cloud < 14.3 pc from the Sun .
The three other primary targets , \beta Car , HD85905 , and HR10 show both short and long term variability , and little of the observed absorption can be attributed to the LISM along the line of sight .
The Spitzer Space Telescope photometry and spectroscopy did not detect infrared excesses .
We fit the maximum hypothetical infrared excess that is consistent with observed upper limits .
We are able to place upper limits on any possible fractional infrared luminosity , which range from L _ { IR } / L _ { \star } < 2 – 5 \times 10 ^ { -6 } , for our three disk stars .
These fractional luminosities are significantly less than that found toward \beta Pic , but comparable to other nearby debris disks .
No stable gas absorption component centered at the radial velocity of the star is detected for any of our targets , consistent with no infrared excess detections .
Based on simple assumptions of the variable gas absorption component , we estimate limits on the circumstellar gas mass causing the variable absorption , which range from 0.4–20 \times 10 ^ { -8 } M _ { \oplus } .
These multiwavelength observations place strong limits on any possible circumstellar dust , while confirming variable circumstellar gas absorption , and therefore are interesting targets to explore the origins and evolution of variable circumstellar gas .