Long-lived Flare From the Stellar Transient iPTF 14hqp
ATel #6796; A. A. Miller (JPL/Caltech), L. A. Hillenbrand, D. A. Perley, G. Duggan, Y. Cao (Caltech), M. Kasliwal (Carnegie), on behalf of the intermediate Palomar Transient Factory
on 9 Dec 2014; 21:05 UT
Credential Certification: Adam Miller (amiller@astro.caltech.edu)
Subjects: Binary, Star, Transient, Variables, Young Stellar Object
We report the discovery of a long-lived stellar flare, which was identified via automated processing of intermediate Palomar Transient Factory (iPTF; Atel#4807) observations. The variable star, named iPTF 14hqp, was discovered on 2014-11-11.21 UT with R = 18.2 mag. The variable is located at R.A. Dec = 21:08:30.49 +44:34:22.7 (J2000). A second observation taken approximately 30 min later at 2014-11-11.23 UT showed that the source had brightened to R = 18.0 mag. No historical variability from the previous 4 years has been detected from this source by PTF/iPTF, and the most recent limits were obtained on 2014-11-04.10 UT, where nothing is present at the source location to a limiting magnitude of R > 20.0 mag. No cataloged sources, including SDSS, 2MASS, UKIDSS, and WISE, have been detected within 4 arcsec of the newly flaring variable.
Subsequent photometric observations show that iPTF 14hqp faded over the following two weeks to R = 19.6 mag on 2014-11-20.18 UT and R = 20.2 on 2014-11-26.17 UT. A low-resolution spectrum obtained with Keck/LRIS on 2014-11-19 UT shows a predominantly featureless, red continuum with Halpha emission at redshift 0.0 as the only distinguishing feature. A second, very low signal-to-noise, low-resolution spectrum was obtained APO/DIS on 2014-11-26 UT shows some broad features possibly consistent with TiO and VO absorption features seen in M-type stars.
The variable is located in the galactic plane, towards the direction of the North America Nebula, but somewhat east of the molecular cloud containing the ongoing star formation. The extinction toward this region is large, and the red continuum observed in the Keck/LRIS spectrum may be the result of reddening, as opposed to an intrinsically cool photosphere for the flaring source. The relatively slow decay (0.15 mag/day) and long-lived (15 day) nature of the flare suggest that this cannot be a typical M-dwarf flare. We speculate that the possible presence of molecular features in the APO/DIS spectrum suggests that the flare is from a symbiotic binary system, where the mass donor is a late-type giant star. In this scenario, the flare occurred as the result of an increase in the accretion rate onto the mass-gaining star.
