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J/A+A/579/A66       Accretion in ρ-Ophiucus              (Manara+, 2015)

X-Shooter study of accretion in ρ-Ophiucus: very low-mass stars and brown dwarfs. Manara C.F., Testi L., Natta A., Alcala J.M. <Astron. Astrophys., 579, A66-66 (2015)> =2015A&A...579A..66M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, pre-main sequence ; Accretion ; Stars, masses ; Effective temperatures ; Equivalent widths Keywords: stars: pre-main sequence - stars: formation - brown dwarfs - protoplanetary disks - accretion, accretion disks - clusters open and associations: individual: rho-Ophiucus Abstract: We present new VLT/X-Shooter optical and near-infrared spectra of a sample of 17 candidate young low-mass stars and brown dwarfs located in the ρ-Ophiucus cluster. We derived the spectral type and extinction for all the targets, and then we determined their physical parameters. All the objects but one have M*≲0.6M, and eight have mass below or close to the hydrogen-burning limit. Using the intensity of various permitted emission lines present in their spectra, we determined the accretion luminosity and mass accretion rates ({dot}(M)acc) for all the objects. When compared with previous works targeting the same sample, we find that, in general, these objects are not as strongly accreting as previously reported, and we suggest that the reason is our more accurate estimate of the photospheric parameters. We also compare our findings with recent works in other slightly older star-forming regions, such as Lupus, to investigate possible differences in the accretion properties, but we find that the accretion properties for our targets have the same dependence on the stellar and substellar parameters as in the other regions. This leads us to conclude that we do not find evidence for a different dependence of {dot}(M)acc with M* when comparing low-mass stars and brown dwarfs. Moreover, we find a similar small (≲1dex) scatter in the {dot}(M)acc-M* relation as in some of our recent works in other star-forming regions, and no significant differences in {dot}(M)acc due to different ages or properties of the regions. The latter result suffers, however, from low statistics and sample selection biases in the current studies. The small scatter in the {dot}(M)acc-M* correlation confirms that mass accretion rate measurements in the literature based on uncertain photospheric parameters and single accretion indicators, such as the Hα width, can lead to a scatter that is unphysically large. Our studies show that only broadband spectroscopic surveys coupled with a detailed analysis of the photospheric and accretion properties allows us to properly study the evolution of disk accretion rates in star-forming regions. Description: We report here about new data collected with the ESO/VLT X-Shooter spectrograph during Pr.Id.085.C-0876 (PI Testi). This instrument acquires spectra of the targets from λ∼300nm to λ∼2500nm simultaneously, splitting the spectrum in three parts, usually referred to as the UVB (λλ∼300-550nm), VIS (λλ∼550-1050nm), and NIR (λλ∼1050-2500nm) arms. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file tabled1.dat 74 178 Properties of rho-Ophiuci young stellar objects from Natta et al. (2006A&A...452..245N, Cat. J/A+A/452/245) using distance of 125pc
See also: J/A+A/452/245 : Near-IR photometry of PMS stars in rho Oph (Natta+, 2006) Byte-by-byte Description of file: tabled1.dat
Bytes Format Units Label Explanations
1- 3 I3 --- Seq Object sequential number 5- 11 A7 --- --- [ISO-Oph] 12- 14 I03 --- ISO ISO-Oph number 15 A1 --- m_ISO [ab] Multiplicity index on ISO 17- 19 A3 --- Class Class 21- 25 F5.2 [Lsun] logL* Stellar luminosity 27- 30 F4.2 [K] logTeff Effective temperature 32- 36 F5.2 [Msun] logM* ?=- Stellar mass (1) 38- 46 A9 --- Line Line identification 48 A1 --- l_EW(line) Limit flag on EW(line) 49- 52 F4.1 0.1nm EW(line) ?=- Line equivalent width 54 A1 --- l_logLline Limit flag on logLline 55- 59 F5.2 [Lsun] logLline ?=- Line luminosity 61 A1 --- l_logLacc Limit flag on logLacc 62- 66 F5.2 [Lsun] logLacc ?=- Accretion luminosity 68 A1 --- l_logdMacc/dt Limit flag on logdMacc/dt 69- 74 F6.2 [Msun/yr] logdMacc/dt ?=- Mass accretion rate
Note (1): M* and age are derived using the evolutionary tracks of Baraffe et al. (1998A&A...337..403B, Cat. J/A+A/337/403) and assuming a single isochrone at 1Myr as explained in Rigliaco et al. (2011A&A...525A..47R, Cat. J/A+A/525/A47).
History: From electronic version of the journal
(End) Patricia Vannier [CDS] 30-Sep-2015
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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