ADDITIONALSPITZERIRS SPECTROSCOPY OF THREE INTERMEDIATE POLARS: THE DETECTION OF A MID-INFRARED SYNCHROTRON FLARE FROM V1223 SAGITTARII

Abstract

We present new Spitzer Infrared Spectrograph (IRS) observations of three intermediate polars: V1223 Sgr, EX Hya, and V603 Aql. We detected a strong, fading flare event from V1223 Sgr. During this event, the flux declined by a factor of 13 in 30 minutes. Given the similarity in the slope of its mid-infrared spectrum during this event to that of AE Aqr, we suggest that this event was caused by transient synchrotron emission. Thus, V1223 Sgr becomes the third cataclysmic variable known to be a synchrotron source. We were unable to confirm the mid-infrared excess noted by Harrison et al. (Paper I) for EX Hya, suggesting that this object is either not a synchrotron source, or is slightly variable. Due to a very high background, V603 Aql was not detected in the long-wavelength regions accessible to the IRS. Given the recent detection of SS Cygni at radio wavelengths during outburst, we extract archival Spitzer IRS spectra for this source obtained during two successive maxima. These spectra do not show a strong excess, but without simultaneous data at shorter wavelengths, it is not possible to determine whether there is any contribution to the mid-infrared fluxes from a synchrotron jet.

HERSCHELOBSERVATIONS OF CIRCINUS X-1 DURING OUTBURST AND QUIESCENCE

“…As in our modeling of the mid-IR SEDs of cataclysmic variables (CVs; Harrison et al 2013b), we assume that the spectra of these sources are combinations of blackbody, free-free, and synchrotron spectra. When the accretion disks in CVs are hot and optically thick, their optical/near-IR SEDs closely resemble 10,000 K blackbodies (see Harrison et al 2010). We will assume that the LMXBs in our survey have similar hot, optically thick accretion disks.…”

THE WISE LIGHT CURVES OF Z CAMELOPARDALIS DURING OUTBURST: EVIDENCE FOR SYNCHROTRON EMISSION?

“…Both the W1 and W2 light curves are consistent with a slow rise of about 0.3 mag over the duration of the observations. As demonstrated by SS Cyg (Harrison et al 2010), the change in brightness in the near/mid-IR from minimum to maximum in CVs is much smaller than seen at optical wavelengths.…”

“…We have also plotted the 12 μm IRAS detection in Figure 2. If this is indeed a real measurement of the synchrotron emission of Z Cam, it is much higher relative to the outburst continuum (60×) than that seen in the IRAS detection of SS Cyg (4×; see Harrison et al 2010). Hoard et al (2014) presented mid-IR data for a sample of nova-like variables, systems with high mass accretion rates.…”

“…The highly variable 12 μm light curve of Z Cam during an outburst suggests that, like SS Cyg, it is a synchrotron source when near visual maximum. If so, it would join the small family of synchrotron emitting CVs: SS Cyg, AE Aqr, V1223 Sgr (Harrison et al 2010), and probably EX Hya (Harrison et al 2010) and GK Per (Harrison et al 2013). There is a significant number of non-magnetic CVs in the AllWISE survey catalog that have extreme (W2 − W3) colors that suggest that they too are sources of non-thermal emission.…”

“…In constructing a pseudo-hardness/intensity diagram for SS Cyg, Körding et al analogize the behavior of SS Cyg with the jet-launching realms observed in X-ray binaries. Harrison et al (2010) concluded that the mysterious IRAS detection of SS Cyg (Jameson et al 1987) was in fact due to the detection of its transient synchrotron jet. Thus, like in many X-ray binaries (see Harrison et al 2014 and references therein), the synchrotron emission from SS Cyg extends into the mid-infrared (mid-IR).…”