scholarly journals A PSF-based Approach to TESS High quality data Of Stellar clusters (PATHOS) – III. Exploring the properties of young associations through their variables, dippers, and candidate exoplanets

2020 ◽  
Vol 498 (4) ◽  
pp. 5972-5989
Author(s):  
D Nardiello
Keyword(s):  
Variable Stars ◽  
Open Clusters ◽  
Light Curves ◽  
Quality Data ◽  
Stellar Systems ◽  
Satellite Mission ◽  
Open Clusters And Associations ◽  
Star Forming ◽  
Star Forming Regions ◽  
Strong Candidate

ABSTRACT Young associations in star-forming regions are stellar systems that allow us to understand the mechanisms that characterize the stars in their early life and what happens around them. In particular, the analysis of the discs and of the exoplanets around young stars allows us to know the key processes that prevail in their evolution and understand the properties of the exoplanets orbiting older stars. The Transiting Exoplanet Survey Satellite mission is giving us the opportunity to extract and analyse the light curves of association members with high accuracy, but the crowding that affects these regions makes difficult the light curve extraction. In the PATHOS project, cutting-edge tools are used to extract high-precision light curves and identify variable stars and transiting exoplanets in open clusters and associations. In this work, I analysed the light curves of stars in five young (≲10 Myr) associations, searching for variables and candidate exoplanets. Using the rotational periods of the association members, I constrained the ages of the five stellar systems (∼2–10 Myr). I searched for dippers, and I investigated the properties of the dust that forms the circumstellar discs. Finally, I searched for transiting signals, finding six strong candidate exoplanets. No candidates with radius RP ≲ 0.9 RJ have been detected, in agreement with the expectations. The frequency of giant planets resulted to be ∼2–3 per cent, higher than that expected for field stars (≲ 1 per cent); the low statistic makes this conclusion not strong, and new investigations on young objects are mandatory to confirm this result.

scholarly journals A PSF-based Approach to TESS High quality data Of Stellar clusters (PATHOS) – II. Search for exoplanets in open clusters of the Southern ecliptic hemisphere and their frequency

2020 ◽  
Vol 495 (4) ◽  
pp. 4924-4942 ◽  
Author(s):  
D Nardiello ◽  
G Piotto ◽  
M Deleuil ◽  
L Malavolta ◽  
M Montalto ◽  
...  
Keyword(s):  
False Positive Rate ◽  
Variable Stars ◽  
Open Clusters ◽  
Light Curves ◽  
Quality Data ◽  
Stellar Clusters ◽  
High Quality ◽  
High Quality Data ◽  
Positive Rate ◽  
Strong Candidate

ABSTRACT The scope of the project ‘A PSF-based Approach to TESS High Quality data Of Stellar clusters’ (PATHOS) is the extraction and analysis of high-precision light curves of stars in stellar clusters and young associations for the identification of candidate exoplanets and variable stars. The cutting-edge tools used in this project allow us to measure the real flux of stars in dense fields, minimizing the effects due to contamination by neighbour sources. We extracted about 200 000 light curves of stars in 645 open clusters located in the Southern ecliptic hemisphere and observed by TESS during the first year of its mission. We searched for transiting signals and we found 33 objects of interest, 11 of which are strong candidate exoplanets. Because of the limited SNR, we did not find any Earth or super-Earth. We identified two Neptune-size planets orbiting stars with $R_{\star }\lt 1.5\, \mathrm{\it R}_{\odot }$, implying a frequency $f_{\star }=1.34 \pm 0.95\, {{\ \rm per\ cent}}$, consistent with the frequency around field stars. The seven Jupiter candidates around stars with $R_{\star }\lt \, 1.5\, \mathrm{\it R}_{\odot }$ imply a frequency $f_{\star }=0.19\pm 0.07\, {{\ \rm per\ cent}}$, which is smaller than in the field. A more complete estimate of the survey completeness and false positive rate is needed to confirm these results. Light curves used in this work will be made available to the astronomical community on the Mikulski Archive for Space Telescope under the project PATHOS.

scholarly journals X-Ray Coronae from Stars

1998 ◽  
Vol 188 ◽  
pp. 13-16
Author(s):  
R. Pallavicini
Keyword(s):  
Open Clusters ◽  
Temperature Structure ◽  
List Type ◽  
Star Forming ◽  
Spectroscopic Observations ◽  
Star Forming Regions ◽  
Complete Mapping ◽  
Sky Survey ◽  
Order Of Magnitude ◽  
Age Range

A number of major advances in stellar coronal physics have occurred since 1990 mainly as a consequence of imaging observations by ROSAT and spectroscopic observations by ASCA. These can be summarised as follows: 1.an all-sky survey has been performed by ROSAT at a sensitivity of ~ 2 × 10−13 erg cm−2 s−1, complemented by pointed observations an order of magnitude deeper;2.complete mapping and deeper pointings have been obtained for virtually all open clusters closer than ~ 500 pc, and covering the age range from ~ 30 Myr to ~ 700 Myr;3.complete mapping and deeper paintings have been obtained for several Star Forming Regions (SFRs) covering the age range ~ 1 to ~ 10 Myr;4.spectroscopic observations of bright coronal sources have been obtained with EUVE and ASCA allowing the derivation of the temperature structure and elemental abundances.

scholarly journals Optical photometric variable stars towards Cygnus OB7

2019 ◽  
Vol 487 (2) ◽  
pp. 1765-1776 ◽  
Author(s):  
Somnath Dutta ◽  
Soumen Mondal ◽  
Santosh Joshi ◽  
Ramkrishna Das
Keyword(s):  
Variable Stars ◽  
T Tauri Stars ◽  
Light Curves ◽  
Main Sequence Stars ◽  
Star Forming ◽  
Rotation Rates ◽  
T Tauri ◽  
Photometric Observations ◽  
Sky Survey ◽  
Magnitude Diagram

ABSTRACT We present optical I-band light curves of the stars towards a star-forming region Cygnus OB7 from 17-night photometric observations. The light curves are generated from a total of 381 image frames with very good photometric precision. From the light curves of 1900 stars and their periodogram analyses, we detect 31 candidate variables including five previously identified. 14 out of 31 objects are periodic and exhibit the rotation rates in the range of 0.15–11.60 d. We characterize those candidate variables using optical/infrared colour–colour diagram and colour–magnitude diagram (CMD). From spectral indices of the candidate variables, it turns out that four are probably Classical T-Tauri stars (CTTSs), rest remain unclassified from present data, they are possibly field stars or discless pre-main-sequence stars towards the region. Based on their location on the various CMDs, the ages of two T Tauri Stars were estimated to be ∼5 Myr. The light curves indicate at least five of the periodic variables are eclipsing systems. The spatial distribution of young variable candidates on Planck 857 GHz (350 $\mu$m) and 2MASS (Two Micron All Sky Survey) Ks images suggest that at least two of the CTTSs are part of the active star-forming cloud Lynds 1003.

scholarly journals Star Clusters in Irregular Galaxies in the Local Group

2002 ◽  
Vol 207 ◽  
pp. 94-104
Author(s):  
Eva K. Grebel
Keyword(s):  
Globular Clusters ◽  
Local Group ◽  
Cluster Formation ◽  
Star Clusters ◽  
Open Clusters ◽  
High Angular Resolution ◽  
Star Clusters And Associations ◽  
Star Forming ◽  
Star Forming Regions ◽  
Irregular Galaxies

I summarize our knowledge of star clusters and associations in irregular galaxies other than the Magellanic Clouds in the Local Group. Surveys affording complete area coverage at high angular resolution are still lacking. Confirmed globular clusters are known only in NGC 6822 and WLM. Very few dIrrs contain populous or sparse open clusters. There is a pronounced deficiency of intermediate-age and young clusters. Apart from parent galaxy mass, the lack of interactions may be a key reason for the lack of cluster formation in the dIrrs. All dIrrs have one or several short-lived OB associations in the star-forming regions in their centers.

scholarly journals Mass segregation effects in very young open clusters

2007 ◽  
Vol 3 (S248) ◽  
pp. 481-483
Author(s):  
L. Chen ◽  
R. de Grijs ◽  
J. L. Zhao
Keyword(s):  
Star Formation ◽  
Strong Support ◽  
Open Clusters ◽  
Proper Motions ◽  
Star Forming ◽  
Star Forming Regions ◽  
Mass Segregation ◽  
The Way

AbstractWe derived proper motions and membership probabilities of stars in the regions of two very young (~ 2–4 Myr-old) open clusters NGC 2244 and NGC 6530. Both clusters show clear evidence of mass segregation, which provides strong support for the suggestion that the observed mass segregation is – at least partially – due to the way in which star formation has proceeded in these complex star-forming regions (“primordial” mass segregation).

scholarly journals Wide-Field Observations of Variable Stars in the Region of NGC 7129

1994 ◽  
Vol 161 ◽  
pp. 475-477
Author(s):  
E.H. Semkov
Keyword(s):  
Variable Stars ◽  
Astronomical Observatory ◽  
Flare Star ◽  
Wide Field ◽  
Field Observations ◽  
Schmidt Telescope ◽  
Bulgarian Academy ◽  
Star Forming ◽  
Star Forming Regions ◽  
Academy Of Sciences

During our programme for nonstable and flare star investigations in the star forming regions, more than 290 UBVR photographic plates in the field of the bright nebula NGC 7129 were obtained. The photographic observations were made with the 50/70/172 cm Schmidt telescope of the Rozhen Astronomical Observatory of the Bulgarian Academy of Sciences during the period September 1984–July 1993.

Periodic masers in massive star forming regions

2017 ◽  
Vol 13 (S336) ◽  
pp. 225-230
Author(s):  
S. Goedhart ◽  
R. van Rooyen ◽  
D. J. van der Walt ◽  
J. P. Maswanaganye ◽  
G. C. MacCleod ◽  
...  
Keyword(s):  
Linear Response ◽  
Massive Star ◽  
Class Ii ◽  
Light Curves ◽  
Star Forming ◽  
Methanol Maser ◽  
Modes Of Variability ◽  
Star Forming Regions ◽  
Underlying Mechanisms ◽  
Periodic Class

AbstractThe first periodic Class II methanol maser was reported on in 2003. Since that time, a number of different monitoring programmes have found periodic masers, as well as other modes of variability. In a few cases, periodicity has been found in other maser species such as formaldehyde and water. Several distinct characteristics of light curves have been noted, possibly pointing to different underlying mechanisms for periodicity if one assumes a linear response to incoming radiation. I will give a brief overview of the known periodic sources, discuss current theories, and present new results obtained from monitoring mainline hydroxyl masers using the seven-element Karoo Array Telescope (KAT-7) during its science verification phase.

XMM-Newton spectroscopy of stars in open clusters and star forming regions

2006 ◽  
Vol 38 (7) ◽  
pp. 1509-1519 ◽  
Author(s):  
R. Pallavicini ◽  
E. Franciosini ◽  
A. Maggio ◽  
L. Scelsi ◽  
J. Sanz-Forcada
Keyword(s):  
Open Clusters ◽  
Star Forming ◽  
Star Forming Regions

scholarly journals Extragalactic star-forming regions and open clusters in the Milky Way

2009 ◽  
Vol 5 (S266) ◽  
pp. 522-522
Author(s):  
F. Sakhibov ◽  
A. S. Gusev ◽  
N. V. Kharchenko ◽  
A. E. Piskunov
Keyword(s):  
Comparative Analysis ◽  
Milky Way ◽  
Interstellar Extinction ◽  
Young Star ◽  
Open Clusters ◽  
Evolutionary Sequence ◽  
Star Forming ◽  
Star Forming Regions ◽  
Irregular Galaxies

AbstractWe have carried out a comparative analysis of the evolution of integrated photometric parameters of young star-forming complexes in spiral and irregular galaxies and Galactic open clusters. We find that when the interstellar extinction is properly taken into account, the extragalactic complexes observed as giant Hii regions and open clusters in the Milky Way form a single evolutionary sequence of objects evolving at different stages.

scholarly journals Analysis of MOST light curves of five young stars in Taurus-Auriga and Lupus 3 star-forming regions★

2011 ◽  
Vol 415 (2) ◽  
pp. 1119-1124 ◽  
Author(s):  
Michal Siwak ◽  
Slavek M. Rucinski ◽  
Jaymie M. Matthews ◽  
Rainer Kuschnig ◽  
David B. Guenther ◽  
...  
Keyword(s):  
Young Stars ◽  
Light Curves ◽  
Star Forming ◽  
Star Forming Regions
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