J/A+A/650/A43 Spectra of NGC 1333 Class I-Class II stars (Fiorellino+, 2021)
KMOS study of the mass accretion rate from Class I to Class II in NGC 1333.
Fiorellino E., Manara C., Nisini B., Ramsay S., Antoniucci S., Giannini T.,
Biazzo K., Alcala J., Fedele D.
<Astron. Astrophys. 650, A43 (2021)>
=2021A&A...650A..43F 2021A&A...650A..43F (SIMBAD/NED BibCode)
ADC_Keywords: Stars, pre-main sequence ; Stars, variable ; Spectroscopy
Keywords: accretion: accretion disks - protoplanetary disks - stars: low-mass -
stars: pre-main sequence - stars: protostars - stars: variables -
stars: T Tauri - stars: Herbig Ae/Be
Abstract:
The mass accretion rate (dM/dtacc) is the fundamental parameter to
understand the process of mass assembly that results in the formation
of a low-mass star. This parameter has been largely studied in
Classical T Tauri stars in star-forming regions with ages of
∼1-10Myr. However, little is known about the accretion
properties of young stellar objects (YSOs) in younger regions and
early stages of star formation, such as in the Class 0/I phases.
We present new near-infrared spectra of 17 Class I/Flat and 35 Class
II sources located in the young (<1Myr) NGC 1333 cluster, acquired
with the KMOS instrument at the Very Large Telescope. Our goal is to
study whether the mass accretion rate evolves with age, as suggested
by the widely adopted viscous evolution model, by comparing the
properties of the NGC 1333 members with samples of older regions.
For the Class II sources in our sample, we measured the stellar
parameters (SpT, AV, and L*) through a comparison of the IR spectra
with a grid of non-accreting Class III stellar templates. We then
computed the accretion luminosity by using the known correlation
between Lacc and the luminosity of HI lines (Paβ and Brγ).
For the Class I sample, where the presence of a large IR excess makes
it impossible to use the same spectral typing method, we applied a
procedure that allowed us to measure the stellar and accretion
luminosity in a self-consistent way. Mass accretion rates dM/dtacc
were then measured once masses and radii were estimated adopting
suitable evolutionary tracks.
The NGC 1333 Class II sources of our sample have
Lacc∼10-4-1L☉ and dM/dtacc∼10-11-10-7M☉/yr.
We find a correlation between accretion and stellar luminosity in the
form of log Lacc=(1.5±0.2)logL*+(-1.0±0.1), and a correlation
between the mass accretion rate and stellar mass in the form of
log(dM/dtacc)=(2.6±0.9)logM*+(-7.3±0.7). Both correlations are
compatible within the errors with the older Lupus star-forming region,
while only the latter is consistent with results from Chamaeleon I.
The Class I sample shows larger accretion luminosities
(∼10-2-102L☉) and mass accretion rates
(∼10-9-10-6M☉/yr) with respect to the Class II stars of the
same cloud. However, the derived mass accretion rates are not
sufficiently high to build up the inferred stellar masses, assuming
steady accretion during the Class I lifetime. This suggests that the
sources are not in their main accretion phase and that most of their
mass has already been accumulated during a previous stage and/or that
the accretion is an episodic phenomenon. We show that some of the
targets originally classified as Class I through Spitzer photometry
are in fact evolved or low accreting objects. This evidence can have
implications for the estimated protostellar phase lifetimes.
The accretion rates of our sample are larger in more embedded and
early stage YSOs. Further observations of larger samples in young
star-forming regions are needed to determine if this is a general
result. In addition, we highlight the importance of spectroscopic
surveys of YSOs to confirm their classification and perform a more
correct estimate of their lifetime.
Description:
Fits file of the objects described in the paper are reported.
Names are the same of Tab.1 and Tab.C.1 in the paper Bright/dim in the
name is related to different exposure time described in Tab.A.1
Wavelength are in microns and flux in erg/(s.cm2.um). Further
informations are stored in the header of each fits file.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 48 61 List of studied stars
list.dat 104 261 List of fits spectra
fits/* . 261 Individual fits spectra
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Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Name Star identification number
5- 6 I2 h RAh Star right ascension (J2000)
8- 9 I2 min RAm Star right ascension (J2000)
11- 16 F6.3 s RAs Star right ascension (J2000)
18 A1 --- DE- Star declination sign (J2000)
19- 20 I2 deg DEd Star declination (J2000)
22- 23 I2 arcmin DEm Star declination (J2000)
25- 30 F6.3 arcsec DEs Star declination (J2000)
32- 48 A17 --- 2MASS 2MASS name (JHHMMSSss+DDMMSSs)
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Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Name Star identification number
5- 6 I2 h RAh Star right ascension (J2000)
8- 9 I2 min RAm Star right ascension (J2000)
11- 16 F6.3 s RAs Star right ascension (J2000)
18 A1 --- DE- Star declination sign (J2000)
19- 20 I2 deg DEd Star declination (J2000)
22- 23 I2 arcmin DEm Star declination (J2000)
25- 30 F6.3 arcsec DEs Star declination (J2000)
32- 35 I4 --- Nx Number of pixels along X-axis
37- 41 F5.3 um Blambda Lower value of wavelength interval
43- 49 F7.5 um blambda Upper value of wavelength interval
51- 61 F11.9 um dlambda Wavelength resolution
63- 64 I2 Kibyte size Size of FITS file
66- 82 A17 --- FileName Name of FITS file, in subdirectory fits
84-104 A21 --- Title Title of the FITS file (1)
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Note (1): Table A1: Observing log
-----------------------------------------------------------------------
OB name Date-Obs DITTime NDIT Nexp airmass seeing arms
s arcsec
-----------------------------------------------------------------------
1brightJ 2018-10-24T05:52:38 20 4 18 1.8 0.90 22
1brightH 2018-10-24T04:46:46 20 4 18 1.9 0.78 22
1brightK 2018-10-03T08:40:36 15 4 18 1.9 1.11 22
1dimJ 2018-10-12T07:45:10 140 2 12 1.9 1.07 18
1dimH 2018-10-23T06:14:43 145 2 12 1.8 0.89 18
1dimK 2018-10-09T06:36:18 145 2 12 1.8 0.99 18
2brightJ 2018-10-23T05:16:11 20 4 18 1.8 0.89 18
2brightH 2018-10-23T05:36:30 20 4 18 1.8 0.83 18
2brightK 2018-10-23T05:55:55 15 4 18 1.8 0.91 18
2dimJ 2018-10-31T04:16:23 150 2 12 1.9 0.79 11
2dimH 2018-10-24T06:44:00 150 2 12 1.8 0.93 11
2dimK 2018-10-09T07:50:17 150 2 12 1.8 0.98 11
3brightJ 2018-10-24T06:24:09 20 4 18 1.8 0.91 12
3brightH 2018-10-24T05:12:31 20 4 18 1.8 0.93 12
3brightK 2018-10-10T08:27:54 15 4 18 2.0 0.98 12
3dimJ 2018-10-31T05:47:49 150 2 12 1.8 0.88 6
3dimH 2018-10-25T04:57:18 150 2 12 1.9 0.93 6
3dimK 2018-10-25T06:02:41 150 2 12 1.8 0.91 6
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Acknowledgements:
Eleonora Fiorellino, eleonora.fiorellino(at)inaf.it
(End) Patricia Vannier [CDS] 25-Feb-2021