NDLI: X-Shooter study of accretion in ρ-Ophiucus: very low-mass stars and brown dwarfs

Content Provider	EDP Sciences
Author	C. F. Manara L. Testi A. Natta J. M. Alcalá
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_{⋆_{≲0.6 M_{⊙_{, 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 (Ṁ_{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 Ṁ_{acc_{with M_{⋆_{when comparing low-mass stars and brown dwarfs. Moreover, we find a similar small (≲1 dex) scatter in the Ṁ_{acc_{−M_{⋆_{relation as in some of our recent works in other star-forming regions, and no significant differences in Ṁ_{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 Ṁ_{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.}}}}}}}}}}}}}}}}}}}}
Page Count	22
File Format	HTM / HTML PDF
ISSN	00046361
Alternate Webpage(s)	https://www.aanda.org/articles/aa/abs/2015/07/aa26169-15/aa26169-15.html
e-ISSN	14320746
Journal	Astronomy & Astrophysics
Volume Number	579
DOI	10.1051/0004-6361/201526169
Language	English
Publisher	EDP Sciences
Publisher Date	2015-07-01
Access Restriction	Open
Rights Holder	© ESO, 2015
Subject Keyword	stars: pre-main sequence stars: formation brown dwarfs protoplanetary disks accretion, accretion disks open clusters and associations: individual: rho-Ophiucus stars: pre-main sequence / stars: formation / brown dwarfs / protoplanetary disks / accretion, accretion disks / open clusters and associations: individual: rho-Ophiucus
Content Type	Text
Resource Type	Article
Subject	Astronomy and Astrophysics Space and Planetary Science

Sl.	Authority	Responsibilities	Communication Details
1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
5	Website/Portal (Helpdesk)	Queries regarding NDLI and its services	support@ndl.gov.in
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