J/A+A/685/A118 Young (sub)stellar obj. X-Shooter spectra (Almendros-Abad+, 2024)
Evolution of the relation between the mass accretion rate and the stellar and
disk mass from BDs to stars.
Almendros-Abad V., Manara C.F., Testi L., Natta A., Claes R.A.B.,
Muzic K., Sanchis E., Alcala J.M., Bayo A., Scholz A.
<Astron. Astrophys. 685, A118 (2024)>
=2024A&A...685A.118A 2024A&A...685A.118A (SIMBAD/NED BibCode)
ADC_Keywords: Stars, pre-main sequence; Spectroscopy; Stars, late-type
Keywords: accretion - accretion disks - protoplanetary disks -
brown dwarfs - stars: pre-main sequence
Abstract:
The time evolution of the dependence of the mass accretion rate with
the stellar mass and the disk mass represents a fundamental way to
understand the evolution of protoplanetary disks and the formation of
planets. In this work we present observations with X-Shooter of 26
Class II very low-mass stars (<0.2M☉) and brown dwarfs in the
Ophiuchus, Chamaeleon-I and Upper Scorpius star-forming regions. These
new observations extend down to SpT of M9 (∼0.02M☉) the
measurement of the mass accretion rate in Ophiuchus and Chamaeleon-I
and add 11 very low-mass stars to the sample of objects previously
studied with broad-band spectroscopy in Upper Scorpius. We obtain the
spectral type and extinction, as well as the physical parameters of
the sources. We use the intensity of various emission lines in the
spectra of these sources to derive the accretion luminosity and mass
accretion rate for the entire sample. Combining these new observations
with data from the literature, we compare relations between accretion
and stellar/disk properties of four different star-forming regions
with different ages: Ophiuchus (∼1Myr), Lupus (∼2Myr), Chamaeleon-I
(∼3Myr) and Upper Scorpius (5-12 Myr). We find the slopes of the
accretion relationships (L*-Lacc, M*-(dMacc/dt)) to steepen in the
1-3Myr age range (i.e. between Ophiuchus, Lupus and Chamaeleon-I), and
that both relationships may be better described with a single power
law. We find that previous claims for a double power law behavior of
the M*-(dMacc/dt) relationship may have been triggered by the use of
a different SpT-Teff scale. We also find the relationship between the
protoplanetary disk mass and the mass accretion rate of the stellar
population to steepen with time down to the age of Upper Scorpius.
Overall, we observe hints of a faster evolution into low accretion
rates of low-mass stars and brown dwarfs. At the same time, we also
found that brown dwarfs present larger Mdisk/(dMacc/dt) ratios
(i.e. longer accretion depletion timescales) than stars in Ophiuchus,
Lupus and Cha-I. This apparently contradictory result may imply that
the evolution of protoplanetary disks around brown dwarfs may be
different than in the stellar regime.
Description:
Reduced, flux- and wavelength-calibrated, telluric corrected 1-d
spectra of the 26 objects considered in this work. Each object's
spectrum is divided in the three arms of X-Shooter, namely the UVB
arm, the VIS arm, and the NIR arm. The spectra are given in fits
format and are not corrected for extinction. The wavelengths are in
nanometers and the flux in erg/s/cm2/nm.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
spectra.dat 185 26 List of X-Shooter spectra
fits/* . 78 Individual fits spectra
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Byte-by-byte Description of file: spectra.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 A24 --- Name Source name
26- 27 I2 h RAh Right ascension (J2000)
29- 30 I2 min RAm Right ascension (J2000)
32- 37 F6.3 s RAs Right ascension (J2000)
39 A1 --- DE- Declination sign (J2000)
40- 41 I2 deg DEd Declination (J2000)
43- 44 I2 arcmin DEm Declination (J2000)
46- 51 F6.3 arcsec DEs Declination (J2000)
53- 61 A9 --- Region Star-forming region to which each source
belongs
63- 66 A4 --- SpType Spectral type
68- 71 F4.1 mag Av Visual extinction
73- 77 F5.3 Lsun Lum Luminosity
79-109 A31 --- UVB UVB spectrum filename in subdirectory spectra
111-141 A31 --- VIS VIS spectrum filename in subdirectory spectra
143-173 A31 --- NIR NIR spectrum filename in subdirectory spectra
175-177 F3.1 --- SLU Width of the UVB slit
179-181 F3.1 --- SLV Width of the VIS slit
183-185 F3.1 --- SLN Width of the NIR slit
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Acknowledgements:
Victor Almendros-Abad, victor.almendrosabad(at)inaf.it
(End) Patricia Vannier [CDS] 07-Feb-2024