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ASAS-SN Discovery of A Likely, Heavily-Obscured Galactic Nova ASASSN-15qd

ATel #8126; B. J. Shappee (Hubble Fellow, Carnegie Observatories), K. Z. Stanek, J. S. Brown, T. W.-S. Holoien, C. S. Kochanek, D. Godoy-Rivera, G. Simonian, U. Basu (Ohio State), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong, Ping Chen (KIAA-PKU), R. M. Wagner (LBTO), J. Brimacombe (Coral Towers Observatory)
on 6 Oct 2015; 02:24 UT
Credential Certification: Benjamin Shappee (bshappee@obs.carnegiescience.edu)

Subjects: Optical, Nova

Referred to by ATel #: 8127, 8136, 8142, 8150, 8332

During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"), using data from the quadruple 14-cm "Brutus" telescope in Haleakala, Hawaii, we detect a new transient source, most likely a nova, near the Galactic plane.

 
Object       RA (J2000)    DEC (J2000)    Gal l (deg)   Gal b (deg)    Disc. UT Date   Disc. V mag 
ASASSN-15qd  19:21:50.139  +15:09:25.31   49.8444       0.3220         2015 Oct. 1.29     15.2 

ASASSN-15qd was discovered in images obtained on UT 2015-10-01.29 at V~15.2 mag. We also detect the source on UT 2015-09-29.31 in images taken under poor conditions at V~14.7. We do not detect (V>17.2) the object in images taken on UT 2015-09-12.35 and before. No previous outbursts are detected in the previous 52 epochs of ASAS-SN data at this location since ASAS-SN started observing the Galactic plane in February 2015. This figure shows the archival SDSS i-band image of the host (left) and our LCOGT i-band confirmation image (right). The red circle has a radius of 2" and is centered on the position of the transient in the confirmation image. No source is seen in any of the SDSS archival images at the location of ASASSN-15qd (i-band limiting magnitude ~ 21.3).

 
JD           Observation Date    V mag  V err 
2457270.87   2015-09-05.37       >17.5   
2457274.78   2015-09-09.28       >17.6   
2457277.85   2015-09-12.35       >17.2   
2457294.81   2015-09-29.31        14.7  0.1 
2457296.79   2015-10-01.29        15.2  0.1 

Assuming an intrinsic color of (B-V)_0 ~ (V-I)_0 ~ 0.0 as a reasonable first guess for the intrinsic color of the nova candidate (e.g., van den Bergh, S.; Younger, P. F. 1987), and using the discovery V-band measurement from ASAS-SN and the 2015-10-02.4356 I-band measurements (Ic = 10.6 +/- 0.1) from the Kamogata-Kiso-Kyoto Wide-field Survey (Maehara 2015, vsnet-alert 19120), we arrive at an approximate value of interstellar reddening of E(V-I)~4.6, as already suggested by Maehara (2015). That translates to A_V=11.5, using the ratio of A_V/E(V-I)=2.5 from Stanek (1996). This estimate is consistent with the "upper limit" given by the total line-of-sight V-band extinction (19.3 mag) found by using the NED Coordinate & Extinction Calculator and the Schlafly et al. 2011 extinction maps.

To get an approximate estimate for the absolute magnitude for ASASSN-15qd, we assume a distance to object is 2kpc-15kpc, a distance modulus of 11.5-15.7 mag, and our estimate for A_V. This yields an absolute V-band magnitude of V~-8.3 - -12.5 on 2015-09-29.31 for ASASSN-15qd. While only approximate, this range is consistent with a Galactic, heavily-obscured nova.

We thank LCOGT and its staff for their continued support of ASAS-SN. ASAS-SN is supported by NSF grant AST-1515927, the Mt. Cuba Astronomical Foundation, the Center for Cosmology and AstroParticle Physics (CCAPP) at OSU, and the Robert Martin Ayers Sciences Fund. For more information about the ASAS-SN project, see the ASAS-SN Homepage and the list of all ASAS-SN transients.