On The Period Determination of ASAS Eclipsing Binaries

Variable stars, or particularly eclipsing binaries, are very essential astronomical occurrence. Surveys are the backbone of astronomy, and many discoveries of variable stars are the results of surveys. All-Sky Automated Survey (ASAS) is one of the observing projects whose ultimate goal is photometric monitoring of variable stars. Since its first light in 1997, ASAS has collected 50,099 variable stars, with 11,076 eclipsing binaries among them. In the present work we focus on the period determination of the eclipsing binaries. Since the number of data points in each ASAS eclipsing binary light curve is sparse, period determination of any system is a not straightforward process. For 30 samples of such systems we compare the implementation of Lomb-Scargle algorithm which is an Fast Fourier Transform (FFT) basis and Phase Dispersion Minimization (PDM) method which is non-FFT basis to determine their period. It is demonstrated that PDM gives better performance at handling eclipsing detached (ED) systems whose variability are non-sinusoidal. More over, using semi-automatic recipes, we get better period solution and satisfactorily improve 53% of the selected object's light curves, but failed against another 7% of selected objects. In addition, we also highlight 4 interesting objects for further investigation.Comment: Presented in International Conferences on Mathematics and Natural Science

An X-ray timing and spectral analysis of the AGN NGC 4051

NGC 4051 is a narrow line Seyfert galaxy 1 (NLS1), and it is one of the brightest Active Galactic Nuclei in the X-ray band. We analysed the power density and energy spectra of NGC 4051 using all available data obtained with NASA's Rossi X-ray Timing Explorer from 1996 to 2011. We divided the data into several time intervals to study possible changes of the spectral and timing properties of the source. All power spectra show a power-law component, but in one of the time intervals a broad, Loretntzian-like, component at ~0.2 Hz is also required to fit the data. The energy spectra are all well fitted with a reflection component. During a period of 26 months, from 2009 to 2011, NGC 4051 showed significant flaring activity in the hard X-ray band. We analysed the data during that period separately. We discuss the results of the timing and spectral fits in the different intervals, and compare our findings with those previously published using only a fraction of the data

PENENTUAN STROKE HEMORAGIK DAN NON-HEMORAGIK MEMAKAI SKORING STROKE

Latar belakang: Manajemen stroke yang rasional harus berdasarkan jenis stroke sehingga sangat penting untuk membedakan antara stroke hemoragik dan non-hemoragik. Di rumah sakit yang tidak memiliki fasilitas neuroimaging dapat digunakan skor stroke untuk membedakan antara stroke hemoragik dan non-hemoragik. Objektif: Bertujuan mengetahui tingkat sensitifitas dan spesifisitas skor strokeyang diperkenalkan oleh Nuartha. Metode: Uji diagnostik dikerjakan secara prospektif pada 167 penderita stroke akut periode Juli 2002 – Juni 2003 di Lab/SMF Neurologi Rumah Sakit Sanglah, Denpasar.  Berdasarkan skor stroke, sampel dikelompokkan menjadi stroke hemoragik dan non-hemoragik, dengan CT-Scan otak sebagai standar baku. Perbedaan karakteristik kedua kelompok dianalisis dengan uji t dan chi-square,memakai program SPSS 11.0 dengan tingkat kemaknaan p<0,05. Hasil: Kelompok stroke hemoragik dan non-hemoragik tidak berbeda bermakna dalam hal jenis kelamin (laki-laki 24,0% berbanding 37,1%) dan rerata umur 62,2 ±11,0 berbanding 62,1 ± 13,4 tahun. Skor stroke dengan rentang nilai 16-24 sebagai stroke hemoragik memiliki tingkat sensitifitas 90,0%, dan tingkat spesifisitas 98,1%. Simpulan: Skor Stroke Nuartha dapat digunakan sebagai alat bantu diagnostik untuk membedakan stroke hemoragik dan non hemoragik bila fasilitas neuroimaging tidak tersedia, terutama pada sarana kesehatan lini pertama. Kata Kunci: Stroke, Skoring Stroke, Stroke Hemoragik, Stroke Non Hemoragik, CT Scan Ota

Stellar Occultations by Large TNOs on 2012: The February 3rd by (208996) 2003 AZ84, and the February 17th by (50000) Quaoar

International audienceOn February 2012, two stellar occultation's by large Trans-neptunian Objects (TNO's) were observed by our group. On the 3rd, an event by (208996) 2003 AZ84 was recorded from Mont Abu Observatory and IUCAA Girawali Observatory in India and from Weizmann Observatory in Israel. On the 17th, a stellar occultation by (50000) Quaoar was observed from south France and Switzerland. Both occultations are the second observed by our group for each object, and will be used to improve the results obtained on the previous events. The occultation by 2003 AZ84 is the first multi-chord event recorded for this object. From the single chord event on January 8th 2011, Braga-Ribas et al. 2011 obtained a lower limit of 573 /- 21 km. From the 2012 occultation the longest chord has a size of 662 /- 50 km. The other chords will permit to determine the size and shape of the TNO, and derive other physical parameters, such as the geometric albedo. The Quaoar occultation was observed from south of France (Observatoire de la Côte d'Azur, TAROT telescope and Valensole) and from Gnosca, Switzerland. Unfortunately, all three sites in France are almost at the same Quaoar's latitude, so in practice, we have two chords that can be used to fit Quaoar's limb. The resulting fit will be compared with the results obtained by Braga-Ribas et al. 2011. Braga-Ribas F., Sicardy B., et al. 2011, EPSC-DPS2011, 1060.Ribas F., Sicardy B., et al. 2011, EPSC-DPS2011, 1060

Stellar Occultations by Large TNOs on 2012: The February 3rd by (208996) 2003 AZ84, and the February 17th by (50000) Quaoar

International audienceOn February 2012, two stellar occultation's by large Trans-neptunian Objects (TNO's) were observed by our group. On the 3rd, an event by (208996) 2003 AZ84 was recorded from Mont Abu Observatory and IUCAA Girawali Observatory in India and from Weizmann Observatory in Israel. On the 17th, a stellar occultation by (50000) Quaoar was observed from south France and Switzerland. Both occultations are the second observed by our group for each object, and will be used to improve the results obtained on the previous events. The occultation by 2003 AZ84 is the first multi-chord event recorded for this object. From the single chord event on January 8th 2011, Braga-Ribas et al. 2011 obtained a lower limit of 573 /- 21 km. From the 2012 occultation the longest chord has a size of 662 /- 50 km. The other chords will permit to determine the size and shape of the TNO, and derive other physical parameters, such as the geometric albedo. The Quaoar occultation was observed from south of France (Observatoire de la Côte d'Azur, TAROT telescope and Valensole) and from Gnosca, Switzerland. Unfortunately, all three sites in France are almost at the same Quaoar's latitude, so in practice, we have two chords that can be used to fit Quaoar's limb. The resulting fit will be compared with the results obtained by Braga-Ribas et al. 2011. Braga-Ribas F., Sicardy B., et al. 2011, EPSC-DPS2011, 1060.Ribas F., Sicardy B., et al. 2011, EPSC-DPS2011, 1060

2003 AZ84: Size, shape, albedo and first detection of topographic features

International audienc

2003 AZ84: Size, shape, albedo and first detection of topographic features

International audienc