Spitzer Observations of the Orion OB1 Association: Disk Census in the Low-Mass Stars

By Jesús Hernández, N. Calvet, C. Briceño, L. Hartmann, A. K. Vivas, J. Muzerolle, J. Downes, L. Allen, R. G. D. O. Astronomy, University of Michigan Centro de Investigaciones de Astronomia and 5 more. 2007

134 citations recorded by the source corpus.

We present new Spitzer observations of two fields in the Orion OB1 association. We report IRAC/MIPS observations for 115 confirmed members and 41 photometric candidates of the ~10 Myr 25 Orionis aggregate in the OB1a subassociation, and 106 confirmed members and 65 photometric candidates of the 5 Myr region located in the OB1b subassociation. The 25 Orionis aggregate shows a disk frequency of 6%, while the field in the OB1b subassociation shows a disk frequency of 13%. Combining IRAC, MIPS, and 2MASS photometry, we place stars bearing disks in several classes: those with optically thick disks (class II systems), with an inner transitional disks (transitional disk candidates), and with “evolved disks”; the last exhibit smaller IRAC/MIPS excesses than class II systems. In all, we identify one transitional disk candidate in the 25 Orionis aggregate and three in the OB1b field; this represents ~10% of the disk-bearing stars, indicating that the transitional disk phase can be relatively fast. We find that the frequency of disks is a function of the stellar mass, suggesting a maximum around stars with spectral type M0. Comparing the infrared excess in the IRAC bands among several stellar groups, we find that inner disk emission decays with stellar age, showing a correlation with the respective disk frequencies. The disk emission at the IRAC and MIPS bands in several stellar groups indicates that disk dissipation takes place faster in the inner region of the disks. Comparison with models of irradiated accretion disks, computed with several degrees of settling, suggests that the decrease in the overall accretion rate observed in young stellar groups is not sufficient to explain the weak disk emission observed in the IRAC bands for disk-bearing stars with ages 5 Myr or older; larger degrees of dust settling are necessary to explain these objects.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/043b1ca272d1482216fb908a454d29163f7273f8

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In Astronomy and Astrophysics

1. K. Luhman
2. Eric Mamajek
3. L. Hartmann
4. L. Hillenbrand
5. N. Calvet
6. G. Herczeg
7. L. Allen
8. R. Gutermuth

Citations in the corpus

• Pre-main-sequence isochrones - II. Revising star and planet formation time-scales (2013, background): “…2007), IC 5146 (Harvey et al. 2008), NGC 2244 (Balog et al. 2007), Cep OB3b (Allen et al. 2012), NGC 2169 (Hernandez et al., in preparation), σ Ori (Hernández et al. 2007), IC 348 (Lada et al. 2006), λ Ori (Barrado D ow nloaded from https://academ ic.oup.com /m…”
• The spatial distribution of star formation in the solar neighbourhood: do all stars form in dense clusters? (2010, background): “Based on Hernandez et al. (2007) we assume that 65% of the YSOs have disks.”
• NEW DEBRIS DISKS AROUND YOUNG, LOW-MASS STARS DISCOVERED WITH THE SPITZER SPACE TELESCOPE (2009, unknown): “…2009; Cieza et al. 2008; Currie et al. 2008b; Hernandez et al. 2008; Cieza & Baliber 2007; – 3 – Currie et al. 2007; Dahm & Hillenbrand 2007; Gorlova et al. 2007; Hernandez et al. 2007a,b; Carpenter et al. 2006; Chen et al. 2005b; Low et al. 2005; Stauffer et al. 2005; Gorlova et al. 2004).”
• TIME EVOLUTION OF VISCOUS CIRCUMSTELLAR DISKS DUE TO PHOTOEVAPORATION BY FAR-ULTRAVIOLET, EXTREME-ULTRAVIOLET, AND X-RAY RADIATION FROM THE CENTRAL STAR (2009, background): “More recent studies of older clusters (e.g. Haisch et al. 2001, Hernandez et al. 2007, Currie et al. 2009) indicate that the lifetime of primordial disks surrounding many young stars is ∼ 3− 5× 106 years, and coupled with estimates of total disk lifetimes suggest that the transition disk phase may…”
• X-Ray-Irradiated Protoplanetary Disk Atmospheres. I. Predicted Emission-Line Spectrum and Photoevaporation (2008, background): “For example, Hernandez et al. (2007b) reported only a 10% frequency of transitional disk candidates among the diskbearing low mass stars in their Spitzer observations of the Orion OB1 association.”
• Star and Protoplanetary Disk Properties in Orion's Suburbs (2009, background): “…al. 2007a), Chamaeleon II (Alcalá et al. 2008; Spezzi et al. 2008), σOri cluster (Béjar et al. 1999; Barrado y Navascués et al. 2003; Sacco et al. 2008; Hernández et al. 2007b), Coronet cluster (Sicilia-Aguilar et al. 2008), IC 348 (Luhman et al. 2003; Lada et al. 2006), Serpens cloud core,…”
• PHOTOEVAPORATION OF CIRCUMSTELLAR DISKS BY FAR-ULTRAVIOLET, EXTREME-ULTRAVIOLET AND X-RAY RADIATION FROM THE CENTRAL STAR (2008, background): “Recent studies of associations in Orion (Hernandez et al. 2007) indicate a peak at a spectral type of M0, which corresponds to a mass of 0.5 M .”
• ALMA OBSERVATIONS OF CIRCUMSTELLAR DISKS IN THE UPPER SCORPIUS OB ASSOCIATION (2016, background): “…Carpenter et al. 2006; Lada et al. 2006; Sicilia-Aguilar et al. 2006; Balog et al. 2007; Barrado y Navascués et al. 2007; Cieza & Baliber 2007; Dahm & Hillenbrand 2007; Hernández et al. 2007a,b; Flaherty & Muzerolle 2008; Gutermuth et al. 2008; Hernández et al. 2008; Luhman & Mamajek 2012).”
• Accretion onto Pre-Main-Sequence Stars (2016, background): “The Spitzer lifetimes might be somewhat overestimated because Class III (nonexcess) stars tend to be undercounted by IR surveys but can constitute a large fraction of young stellar populations (Kenyon et al. 1990, 1994, Haisch et al. 2001, Hernández et al. 2007).”
• Protoplanetary disk lifetimes vs stellar mass and possible implications for giant planet populations (2015, result): “These results are in agreement with previous studies (e.g. Lada et al. 2000; Hernández et al. 2007b, 2008; Murphy et al. 2013) and supersede our results in R14.”
• THE DISK POPULATION OF THE TAURUS STAR-FORMING REGION (2009, methodology): “One of the transitional disks in 25 Ori, source 1200 from Hernández et al. (2007b), has been studied in detail through IRS and Hα spectroscopy and a comparison of its SED to the predictions of disk models (Espaillat et al. 2008b).”
• A Spitzer View of Protoplanetary Disks in the γ Velorum Cluster (2008, methodology): “Figure 11 shows the disk frequencies of late type stars (stars K middle or later) with near-infrared disk emission in different stellar groups, as a function of age (Hernández et al. 2005, 2007a; Haisch et al. 2001).”
• On the diversity and statistical properties of protostellar discs (2018, background): “…the youngest star-forming regions (a few Myr), observational determinations of disc fractions typically range from ≈ 50 − 85% (Haisch et al. 2000; Lada et al. 2000; Haisch et al. 2001; Lada et al. 2006; Balog et al. 2007; Guarcello et al. 2007; Hernández et al. 2007,?, 2008; Harvey et al. 2008).”
• The star formation history and accretion-disc fraction among the K-type members of the Scorpius–Centaurus OB association (2016, result): “This is consistent with the massdependent trend first identified by Carpenter et al. (2006) and fur- ther confirmed by Luhman & Mamajek (2012) in Upper Sco, as well as the results of Hernández et al. (2007) from the younger σ Ori association at ∼6 Myr (Bell et al. 2013).”