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Herczeg, GJ, Dong, S, Shappee, BJ, Chen, P, Hillenbrand, LA, Jose, J, Kochanek, CS, Prieto, JL, Stanek, KZ, Kaplan, K, Holoein, TW-S, Mairs, S, Johnstone, D, Gully-Santiago, M, Zhu, Z, Smith, MC, Bersier, D, Mulders, GD, Filippenko, AV, Ayani, K , Brimacombe, J, Brown, JS, Connelley, M, Harmanen, J, Ito, R, Kawabata, KS, Maehara, H, Takata, K, Yuk, H and Zheng, W (2016) The Eruption of the Candidate Young Star ASASSN-15qi. Astrophysical Journal, 831 (2). ISSN 0004-637X
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Abstract
Outbursts on young stars are usually interpreted as accretion bursts caused by instabilities in the disk or the star-disk connection. However, some protostellar outbursts may not fit into this framework. In this paper, we analyze optical and near-infrared spectra and photometry to characterize the 2015 outburst of the probable young star ASASSN-15qi. The $\sim 3.5$ mag brightening in the $V$ band was sudden, with an unresolved rise time of less than one day. The outburst decayed exponentially by 1 mag for 6 days and then gradually back to the pre-outburst level after 200 days. The outburst is dominated by emission from $\sim10,000$ K gas. An explosive release of energy accelerated matter from the star in all directions, seen in a spectacular cool, spherical wind with a maximum velocity of 1000 km/s. The wind and hot gas both disappeared as the outburst faded and the source the source returned to its quiescent F-star spectrum. Nebulosity near the star brightened with a delay of 10-20 days. Fluorescent excitation of H$_2$ is detected in emission from vibrational levels as high as $v=11$, also with a possible time delay in flux increase. The mid-infrared spectral energy distribution does not indicate the presence of warm dust emission, although the optical photospheric absorption and CO overtone emission could be related to a gaseous disk. Archival photometry reveals a prior outburst in 1976. Although we speculate about possible causes for this outburst, none of the explanations are compelling.
| Item Type: | Article |
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| Uncontrolled Keywords: | astro-ph.SR; astro-ph.SR |
| Subjects: | Q Science > QB Astronomy Q Science > QC Physics |
| Divisions: | Astrophysics Research Institute |
| Publisher: | American Astronomical Society; IOP Publishing |
| Related URLs: | |
| Date Deposited: | 25 Nov 2016 12:09 |
| Last Modified: | 04 Sep 2021 04:13 |
| DOI or ID number: | 10.3847/0004-637X/831/2/133 |
| URI: | https://researchonline.ljmu.ac.uk/id/eprint/3943 |
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