Optical Studies of Ten Hard X-ray Selected Cataclysmic Binaries. (arXiv:2110.07466v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Halpern_J/0/1/0/all/0/1">J. P. Halpern</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Thorstensen_J/0/1/0/all/0/1">J. R. Thorstensen</a>
We conducted time-resolved optical spectroscopy and/or photometry of ten
cataclysmic binaries that were discovered in hard X-ray surveys, with the goal
of measuring their orbital periods and searching for evidence that they are
magnetic. Four of the objects in this study are new optical identifications:
IGR J18017$-$3542, PBC J1841.1+0138, IGR J18434$-$0508, and Swift J1909.3+0124.
A 311.8 s, coherent optical pulsation is detected from PBC J1841.1+0138, as
well as eclipses with a period of 0.221909 days. A 152.49 s coherent period is
detected from IGR J18434$-$0508. A probable period of 389 s is seen in IGR
J18151$-$1052, in agreement with a known X-ray spin period. We also detect a
period of 803.5 s in an archival X-ray observation of Swift J0717.8$-$2156. The
latter four objects are thus confirmed magnetic CVs of the intermediate polar
class. An optical period of 1554 s in AX J1832.3$-$0840 also confirms the known
X-ray spin period, but a stronger signal at 2303 s is present whose
interpretation is not obvious. We also studied the candidate intermediate polar
Swift J0820.6$-$2805, which has low and high states differing by $approx4$
mag, and optical periods or QPOs not in agreement with proposed X-ray periods.
Of note is an unusually long 2.06 day orbital period for Swift J1909.3+0124,
manifest in the radial velocity variation of photospheric absorption lines of
an early K-type companion star. The star must be somewhat evolved if it is to
fill its Roche lobe.
We conducted time-resolved optical spectroscopy and/or photometry of ten
cataclysmic binaries that were discovered in hard X-ray surveys, with the goal
of measuring their orbital periods and searching for evidence that they are
magnetic. Four of the objects in this study are new optical identifications:
IGR J18017$-$3542, PBC J1841.1+0138, IGR J18434$-$0508, and Swift J1909.3+0124.
A 311.8 s, coherent optical pulsation is detected from PBC J1841.1+0138, as
well as eclipses with a period of 0.221909 days. A 152.49 s coherent period is
detected from IGR J18434$-$0508. A probable period of 389 s is seen in IGR
J18151$-$1052, in agreement with a known X-ray spin period. We also detect a
period of 803.5 s in an archival X-ray observation of Swift J0717.8$-$2156. The
latter four objects are thus confirmed magnetic CVs of the intermediate polar
class. An optical period of 1554 s in AX J1832.3$-$0840 also confirms the known
X-ray spin period, but a stronger signal at 2303 s is present whose
interpretation is not obvious. We also studied the candidate intermediate polar
Swift J0820.6$-$2805, which has low and high states differing by $approx4$
mag, and optical periods or QPOs not in agreement with proposed X-ray periods.
Of note is an unusually long 2.06 day orbital period for Swift J1909.3+0124,
manifest in the radial velocity variation of photospheric absorption lines of
an early K-type companion star. The star must be somewhat evolved if it is to
fill its Roche lobe.
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