Further BVRI photometry of ASASSN-15qi using the Tautenburg Schmidt and Leicester telescopes

ATel #8364; Bringfried Stecklum, Jochen Eisloeffel (Thueringer Landessternwarte Tautenburg), Klaas Wiersema (University of Leicester)
on 4 Dec 2015; 19:07 UT
Credential Certification: Bringfried Stecklum (stecklum@tls-tautenburg.de)

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We report further optical monitoring of the transient ASASSN-15qi using the 1.34-m Tautenburg Schmidt and the 0.5-m Leicester telescopes along with results from archival data.
The brightening of 2MASS J22560882+5831040 between Oct 2 and Oct 3, 2015 was reported by the ASAS-SN transients survey as ASASSN-15qi (http://www.astronomy.ohio-state.edu/~assassin/transients.html, Shappee ea. 2014, ApJ, 788:A48). Recent optical and NIR spectroscopy by Hillenbrand, Reipurth & Connelley (ATel #8331) and Connelley, Reipurt & Hillenbrand (ATel #8333) confirmed earlier findings by Maehara, Ayani, Itoh, Takata & Kawabata (ATel #8147) concerning the presence of a fast wind, traced by P Cygni profiles in a variety of lines. Moreover, a compact nebula associated with the object was found. The fast brightness decline and the apparent lack of IR excess raised doubts on the whether the source represents an outbursting YSO.
On Oct. 09.96, one week after the brightening, BR imaging of ASASSN-15qi was obtained within the generic transient followup program using the 0.5-m Leicester telescope. The total integration time amounts to 180s per filter, and the spatial resolution (FWHM) of the 2x2 rebinned images (pixel scale 0.89") is about 2.5". Further BVRI imaging using the 1.34-m Tautenburg Schmidt telescope was performed on Nov. 05.77 and Nov. 13.99 using integration times of 300, 120, 60, and 20s, respectively. The spatial resolution for the V band images is 1.6" and 2.2", respectively. Searching the Schmidt CCD archive revealed that ASASSN-15qi was covered by Halpha, [SII], and I band observations targeting the field of DI Cep, carried out on 2004 Sep. 09.90. The analysis of the data from both telescopes was done in the same fashion as described by Stecklum, Eisloeffel & Scholz (ATel #8210). The results of the additional photometry are as follows.

2004 Sep. 09.90 I=15.08+/-0.08
2015 Oct. 09.96 B=15.34+/-0.25, R=13.90+/-0.10
(B is based on the TYCHO-2 magnitude of BT=15.62, assuming [BT-VT] did not change during the fade)
2015 Nov. 05.77 B=17.05+/-0.12, V=15.79+/-0.09, R=14.94+/-0.09, I=13.80+/-0.03
2015 Nov. 13.99 B=17.16+/-0.10, V=15.99+/-0.05, R=15.23+/-0.16, I=13.92+/-0.03

Together with IPHAS and URAT1 measurements, the additional pre-outburst I magnitude confirms a variability at the +/-0.5mag level during the low state.
The 2004 narrow-band images reveal the close-by HII region and more widespread ionized gas to the southwest. No emission knots hinting at an Herbig-Haro flow from ASASSN-15qi were found. RGB color frames based on the 2004 Sep. 09.90 (I, Halpha, [SII]; left) and 2015 Nov. 05.77 (I, V, R; right) can be retrieved from the bottom link. The green contours represent the I band emission from 2004 Sep. 09.90. This comparison confirms that the compact nebulosity southeast of ASASSN-15qi is absent on frames taken before the brightening. It is thus the likely result of a non-isotropic outburst where the involved mass loss created a scattering nebula. In this respect we have to withdraw our statement made in ATel #8210 for what concerns the presence of a nebulosity which was based on images of comparatively poor spatial resolution.
If this is a YSO indeed, the asymmetric nebulosity as well as the CO bandheads seen in emission (cf. ATel #8333) point to an inclination closer to pole- rather than edge-on. We note that while variability is a general issue when modelling YSO SEDs, for this object the emission from the nearby HII region adds another complication. As it is obvious from the WISE channel 3 and 4 images, and indicated by the contamination and confusion flag in the ALLWISE catalog, the source emission at these wavelengths is overwhelmed by the thermal background at the spatial resolution of WISE. High-resolution IR and submm/mm observations are required to reveal whether this source is as enigmatic as it seems now.

ASASSN-15qi_TLS_2004_2015