AN INFRARED/X-RAY SURVEY FOR NEW MEMBERS OF THE TAURUS STAR-FORMING REGION

By K. Luhman, Eric Mamajek, P. R. Allen, Kelle Cruz. 2009

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We present the results of a search for new members of the Taurus star-forming region using data from the Spitzer Space Telescope and the XMM-Newton Observatory. We have obtained optical and near-infrared spectra of 44 sources that exhibit red Spitzer colors that are indicative of stars with circumstellar disks and 51 candidate young stars that were identified by Scelsi and coworkers using XMM-Newton. We also performed spectroscopy on four possible companions to members of Taurus that were reported by Kraus and Hillenbrand. Through these spectra, we have demonstrated the youth and membership of 41 sources, 10 of which were independently confirmed as young stars by Scelsi and coworkers. Five of the new Taurus members are likely to be brown dwarfs based on their late spectral types (>M6). One of the brown dwarfs has a spectral type of L0, making it the first known L-type member of Taurus and the least massive known member of the region (M ∼ 4–7 MJup). Another brown dwarf exhibits a flat infrared spectral energy distribution, which indicates that it could be in the protostellar class I stage (star+disk+envelope). Upon inspection of archival images from various observatories, we find that one of the new young stars has a large edge-on disk (r = 2.″5 = 350 AU). The scattered light from this disk has undergone significant variability on a timescale of days in optical images from the Canada–France–Hawaii Telescope. Using the updated census of Taurus, we have measured the initial mass function for the fields observed by XMM-Newton. The resulting mass function is similar to previous ones that we have reported for Taurus, showing a surplus of stars at spectral types of K7–M1 (0.6–0.8 M☉) relative to other nearby star-forming regions, such as IC 348, Chamaeleon I, and the Orion Nebula Cluster.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/e38f07de998b505d977a67e6b27d29618b16706a

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Citations in the corpus

A Universal Stellar Initial Mass Function? A critical look at variations in extreme environments (2010, background): “Most recently, Luhman et al. (2009) analyzed Spitzer observations and x–ray data obtained from the XMM satellite (XEST - XMM-Newton Extended Survey of Taurus; Güdel et al. 2007).”
MAPPING THE SHORES OF THE BROWN DWARF DESERT. II. MULTIPLE STAR FORMATION IN TAURUS–AURIGA (2011, background): “However, there could be additional undiscovered companions; several of these candidate ultrawide companions were discovered only within the past 1–2 years (Scelsi et al. 2008; Luhman et al. 2009).”
AN OPTICAL SPECTROSCOPIC STUDY OF T TAURI STARS. I. PHOTOSPHERIC PROPERTIES (2014, background): “Table 8 compares 29 stars with spectral types and extinctions measured here, in a survey of the MBM 12 Association by Luhman (2001), and in a survey of Spitzer IRAC/X-ray excess sources by Luhman et al. (2009).”
The Formation and Early Evolution of Low-Mass Stars and Brown Dwarfs (2012, methodology): “We can compare those predictions to observations, which can be summarized as follows based on the field and cluster data: brown dwarfs have a binary fraction of 20–30% (Basri & Reiners 2006, Maxted & Jeffries 2005), most of the binaries are tight (<20 AU) and a few are very wide > 100 AU, and the ma”
FUNDAMENTAL PARAMETERS AND SPECTRAL ENERGY DISTRIBUTIONS OF YOUNG AND FIELD AGE OBJECTS WITH MASSES SPANNING THE STELLAR TO PLANETARY REGIME (2015, unknown): “…(38) Kirkpatrick et al. (1997), (39) Metchev et al. (2008), (40) West et al. (2008), (41) Turnbull & Tarter (2003), (42) Henry et al. (2006), (43) Luhman et al. (2009), (44) Scholz et al. (2011), (45) Kirkpatrick et al. (2011), (46) Martín et al. (1999), (47) Kirkpatrick et al. (2008), (48) Reid…”
Inverse dynamical population synthesis: Constraining the initial conditions of young stellar clusters by studying their binary populations (2012, background): “Taurus contains more than 300 known members and the stellar density in each of its clusters is at 1 − 10 stars pc−3 very low (Luhman et al. 2009).”
Search for brown-dwarf companions of stars (2010, background): “…constitute objects at the transition between planets and stars, though the lower end of the brown-dwarf mass range overlaps with the one of massive planets (e.g. Luhman et al. 2009), and the distinction between planets and brown dwarfs may require to trace the individual formation process.”
Imaging Extrasolar Giant Planets (2016, background): “A handful of companions in the 5–15 MJup range have been discovered with direct imaging: 2M1207–3932 b (Chauvin et al. 2004; Chauvin et al. 2005a), 2M0441+2301 b (Todorov et al. 2010), and possibly both FU Tau B (Luhman et al. 2009b) and VHS 1256–1257 (Gauza et al. 2015) depending on their ages.”
Dense core formation by fragmentation of velocity-coherent filaments in L1517 (2011, background): “In this sense, the L1517 cloud seems a quiescent remnant of a larger gas cloud that gave rise to AB Aur, SU Aur, and an additional group of PMS stars located in their vicinity (Luhman et al. 2009).”
Stellar, brown dwarf and multiple star properties from a radiation hydrodynamical simulation of star cluster formation (2011, background): “…minimum mass is also greater than the estimated masses of some objects observed in star-forming regions (Zapatero Osorio et al. 2000, 2002; Kirkpatrick et al. 2001, 2006; Lodieu et al. 2008; Luhman et al. 2008, 2009b; Bihain et al. 2009; Burgess et al. 2009; Weights et al. 2009; Quanz et al. 2010).”
THE TAURUS SPITZER SURVEY: NEW CANDIDATE TAURUS MEMBERS SELECTED USING SENSITIVE MID-INFRARED PHOTOMETRY (2009, background): “Extragalactic objects from Luhman et al. Eight objects show up as having YSO-like colors in at least one of the color spaces we investigated and are reported as spectroscopically confirmed non-members by Luhman et al. (2006, 2009b).”
Cores, filaments, and bundles: hierarchical core formation in the L1495/B213 Taurus region (2013, background): “This population of YSOs has been the subject of a number of dedicated studies, most recently by Luhman et al. (2009) and Rebull et al. (2010), and by the dedicated outflow search from Davis et al. (2010).”
THE ROLE OF MULTIPLICITY IN DISK EVOLUTION AND PLANET FORMATION (2011, result): “…for a full discussion of biases and completeness, but here note that given the meager yield of ≤M4 stars among recent surveys (Scelsi et al. 2008; Luhman et al. 2009; Rebull et al. 2010; Findeisen & Hillenbrand 2010), there is unlikely to be a large population of Taurus members in this mass…”
THE MASS DEPENDENCE BETWEEN PROTOPLANETARY DISKS AND THEIR STELLAR HOSTS (2013, background): “The published classifications for many mid/late-M stars are more accurate than assumed here (±0.5 sub-classes or better; e.g., Luhman et al. 2009a), but we feel our conservative approach is warranted due to the lingering uncertainty in the type – temperature conversion.”
BANYAN. XI. The BANYAN Σ Multivariate Bayesian Algorithm to Identify Members of Young Associations with 150 pc (2018, unknown): “The membership lists of Luhman et al. (2009) and Esplin et al. (2014) were adopted here, without differenciating the sub-groups.”
THE DISK POPULATION OF THE TAURUS STAR-FORMING REGION (2009, methodology): “…of the Hα emission lines from the candidate evolved transitional/debris systems do not indicate the presence of active accretion, and thus allow for the possibility of gas depletion (Strom et al. 1989; Kenyon et al. 1998; White & Ghez 2001; Muzerolle et al. 2003; Luhman 2004b; Luhman et al. 2009b).”
LkCa 15: A YOUNG EXOPLANET CAUGHT AT FORMATION? (2011, background): “The observed fluxes for any individual component, or even for the sum, are fainter than all but the few least-massive members of Taurus-Auriga, which themselves fall in the planetarymass range (e.g., Luhman et al. 2009).”