Mass accretion rates from multiband photometry in the Carina Nebula: the case of Trumpler 14

Abstract

We present a study of the mass accretion rates of pre-main sequence (PMS) stars in the cluster Trumpler 14 (Tr 14) in the Carina Nebula. Using optical multiband photometry we were able to identify 356 PMS stars showing Hα excess emission with equivalent width EW(Hα) > 20 Å. We interpret this observational feature as an indication that these objects are still actively accreting gas from their circumstellar medium. From a comparison of the HR diagram with PMS evolutionary models we derive ages and masses of the PMS stars. We find that most of the PMS objects are younger than 10 Myr with a median age of ∼3 Myr. Surprisingly, we also find that ∼20% of the mass accreting objects are older than 10 Myr. For each PMS star in Trumpler 14 we determine the mass accretion rate (Ṁ acc ) and discuss its dependence on mass and age. We finally combine the optical photometry with near-IR observations to build the spectral energy distribution (SED) for each PMS star in Tr 14. The analysis of the SEDs suggests the presence of transitional discs in which a large amount of gas is still present and sustains accretion onto the PMS object at ages older than 10 Myr. Our results, discussed in light of recent recent discoveries with Herschel of transitional discs containing a massive gas component around the relatively old PMS stars TW Hydrae, 49 Ceti, and HD 95086, support a new scenario n which old and evolved debris discs still host a significant amount of gas.

A comparative study on the reliability of open cluster parameters

“…Trumpler 14: this object is one of the few young massive (starburst) star clusters in the Milky Way (Beccari et al 2015;Negueruela 2014), and is located in the north-west extension of the Great Carina Nebula. Since it is a prominent cluster, it received much attention in the previous century.…”

Star Clusters Near and Far

“…While X-ray observations require space missions (e.g., Chandra or XMM-Newton), the optical and NIR observations can also be obtained from the ground, and with extreme AO even at similar spatial resolutions as HST provides. Combining these broad-band observations with narrow-band observations such as the Hα or Paβ filter allows to detect pre-main sequence stars with active mass accretion (e.g., De Marchi et al 2011;Beccari et al 2015;Zeidler et al 2016a;Kalari 2019) revealing protoplanetary disks. NUV and FUV photometry and spectroscopy from space is necessary to study and classify the most massive OB-stars.…”

A High-Resolution Multiband Survey of Westerlund 2 With the Hubble Space Telescope. Ii. Mass Accretion in the Pre-Main-Sequence Population

“…De presented a method that uses two broadband filters (V and I in their study) to determine the continuum emission in combination with the narrow-band Hα filter to identify PMS stars with disk accretion. This method had been pioneered for the study of Hα emission-line stars in young clusters by Grebel et al (1992) and has since been widely used in multiple studies of different regions within the MW and the Magellanic Clouds , 2011a,b, 2013Beccari et al 2010Beccari et al , 2015Spezzi et al 2012). A summary can also be found in De .…”