J/ApJ/831/133 Follow-up of probable young star ASASSN-15qi (Herczeg+, 2016)
The eruption of the candidate young star ASASSN-15qi.
Herczeg G.J., Dong S., Shappee B.J., Chen P., Hillenbrand L.A., Jose J.,
Kochanek C.S., Prieto J.L., Stanek K.Z., Kaplan K., Holoien T.-S.,
Mairs S., Johnstone D., Gully-Santiago M., Zhu Z., Smith M.C., Bersier D.,
Mulders G.D., Filippenko A.V., Ayani K., Brimacombe J., Brown J.S.,
Connelley M., Harmanen J., Itoh R., Kawabata K.S., Maehara H., Takata K.,
Yuk H., Zheng W.
<Astrophys. J., 831, 133-133 (2016)>
=2016ApJ...831..133H 2016ApJ...831..133H (SIMBAD/NED BibCode)
ADC_Keywords: Photometry, UBV ; YSOs
Keywords: stars: formation; stars: pre-main sequence; stars: variables: general;
stars: winds, outflows
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 ∼3.5mag brightening in the V band was sudden,
with an unresolved rise time of less than one day. The outburst
decayed exponentially by 1mag for 6 days and then gradually back to
the pre-outburst level after 200 days. The outburst is dominated by
emission from ∼10000K 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 1000km/s. The wind and hot
gas both disappeared as the outburst faded and the source returned to
its quiescent F-star spectrum. Nebulosity near the star brightened
with a delay of 10-20 days. Fluorescent excitation of H2 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,
though 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.
Description:
The outburst of ASASSN-15qi (2MASS J22560882+5831040) occurred on
JD2457298 (2015 October 2; UTC dates are used herein). The All-Sky
Automated Survey for Supernovae (ASAS-SN) is an all-sky V-band
transient survey with a limiting magnitude of ∼17. ASAS-SN photometry
of ASASSN-15qi was obtained from two different telescopes on
Haleakala, Hawaii with intervals of one to three days. ASAS-SN
photometry is listed in Table 2.
Archival photometry, ground-based optical photometry with Las Cumbres
Observatory Global Telescope Network (LCOGT) 1m telescope at McDonald
Observatory between 2015 October 23 and December 23 and at the
Liverpool Telescope on 2016 April 26 and June 11, Swift/UVOT
photometry on 2015 October 12 (ID 00034098001) and 2015 December 27
(ID 00034098002), NIR photometry with the NOTCam camera at the Nordic
Optical Telescope (NOT) on 2015 December 22 and Spitzer/IRAC MIR
photometry on 2006 December 29 (Program ID 30734, PI Donald Figer) and
James Clerk Maxwell Telescope (JCMT) SCUBA2 submillimeter observations
of ASASSN-15qi on 2015 November 5 and optical and NIR spectroscopy
observations are also described in section 2.
Objects:
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RA (ICRS) DE Designation(s)
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22 56 08.82 +58 31 04.1 ASASSN-15qi = 2MASS J22560882+5831040
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 35 99 The ASAS-SN photometry
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See also:
B/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-2014)
II/321 : IPHAS DR2 Source Catalogue (Barentsen+, 2014)
I/284 : The USNO-B1.0 Catalog (Monet+ 2003)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/MNRAS/458/3479 : SVM selection of WISE YSO Candidates (Marton+, 2016)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 13 F13.5 d JD Julian Date of the observation
15- 19 F5.2 mag Vmag [13.5/18] V band magnitude
21- 24 F4.2 mag e_Vmag [0.02/0.8] The 1σ error in Vmag
26- 30 F5.2 Jy Flux [0.2/15] V band flux density
32- 35 F4.2 Jy e_Flux [0.1/0.5] The 1σ error in Flux
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History:
From electronic version of the journal
(End) Prepared by [AAS), Emmanuelle Perret [CDS] 06-Feb-2017