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Gaia 19ajj: A Young Star Brightening Due to Enhanced Accretion and Reduced Extinction

Hillenbrand, Lynne A. and Reipurth, Bo and Connelley, Michael and Cutri, Roc M. and Isaacson, Howard (2019) Gaia 19ajj: A Young Star Brightening Due to Enhanced Accretion and Reduced Extinction. Astronomical Journal, 158 (6). Art. No. 240. ISSN 1538-3881. doi:10.3847/1538-3881/ab4e16.

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We report on the source Gaia 19ajj, identifying it as a young star associated with a little-studied star-forming region seen along a complex line of sight through the Gum Nebula. The optical lightcurve recently recorded by Gaia exhibits a slow and unsteady 5.5 mag rise over about 3 yr, while the mid-infrared lightcurve from NEOWISE over the same time period shows a 1.2 mag rise having similar structure. Available color information is inconsistent with pure extinction reduction as the cause for the photometric brightening. Optical spectroscopic characteristics in the current bright phase include: little in the way of absorption except for the hallmark Li I 6707 Å signature of youth plus weak, e.g., Ca I and notably Ba II; strong wind/outflow in Ca II, Mg I b, Na I D, Hα, K I, and O I; jet signatures in [O I], [S II], [Ca II], [Fe II], and [Ni II]; and narrow rest-velocity emission in neutral species such as Fe I, Ni I, and Mg I. The infrared spectrum is also characterized by outflow and emission, including: a hot He I wind, jet lines such as [Fe II] and H2; and weak narrow rest-velocity atomic line emission. The ¹²CO bandheads are weakly in emission, but there is also broad H₂O absorption. Gaia 19ajj exhibited a previous bright state in the 2010–2012 time frame. The body of photometric and spectroscopic evidence suggests that the source bears resemblance to V2492 Cyg (PTF 10nvg) and PV Cep, both of which similarly experience bright phases that recur on long timescales, with large-amplitude photometric variations and emission-dominated spectra. We interpret the behavior of Gaia 19ajj as caused by cycles of enhanced disk accretion accompanied by reduced extinction.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Reipurth, Bo0000-0001-8174-1932
Connelley, Michael0000-0002-8293-1428
Cutri, Roc M.0000-0002-0077-2305
Isaacson, Howard0000-0002-0531-1073
Alternate Title:Gaia 19ajj: A Young Star Brightening Due to Enhanced Accretion + Reduced Extinction
Additional Information:© 2019 The American Astronomical Society. Received 2019 July 16; revised 2019 October 12; accepted 2019 October 14; published 2019 November 20. We gratefully acknowledge Simon Hodgkin for his stewardship of the Gaia Photometric Science Alerts, as well as the Gaia Photometric Science Alerts Team, DPAC, and ESA/Gaia. We also gratefully acknowledge the NASA/NEOWISE Team. Andrew Howard enabled the Keck/HIRES data acquisition. Trevor David investigated for us the potential availability of TESS data. This research has made extensive use of CDS services such as SIMBAD and Vizier. This research has benefited from consultation of the AAVSO Database; we acknowledge with thanks the variable star observations contributed there by observers worldwide. Finally, we are grateful to the referee for a detailed review of our work. Facilities: Gaia - , ASAS-SN - , IRTF:SpeX - , Keck:I (HIRES) - , Keck:II (NIRSPEC) - , 2MASS - , WISE - , NEOWISE - , IRSA. -
Group:Infrared Processing and Analysis Center (IPAC), Astronomy Department
Subject Keywords:Stellar accretion disks; Stellar accretion; Circumstellar matter; Stellar activity; Star formation; T Tauri stars; Herbig Ae/Be stars
Issue or Number:6
Classification Code:Unified Astronomy Thesaurus concepts: Stellar accretion disks (1579); Stellar accretion (1578); Circumstellar matter (241); Stellar activity (1580); Star formation (1569); T Tauri stars (1681); Herbig Ae/Be stars (723)
Record Number:CaltechAUTHORS:20191120-144838506
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Official Citation:Lynne A. Hillenbrand et al 2019 AJ 158 240
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99963
Deposited By: Tony Diaz
Deposited On:20 Nov 2019 22:58
Last Modified:16 Nov 2021 17:50

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