The Naini Tal -Cape survey for pulsations in chemically peculiar A-type stars

Martinez, Peter; Kurtz, D. W.; Ashoka, B. N.; Chaubey, U. S.; Girish, V.; Gupta, S. K.; Joshi, Santosh; Kasturirangan, K.; Sagar, Ram; Seetha, S.

doi:10.1051/0004-6361:20010432

Cited by 40 publications

(47 citation statements)

References 24 publications

(9 reference statements)

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“…This is the only survey of its kind that was conducted from both the northern and southern hemisphere. The first three papers of this survey described the scope and methods of the survey and reported the discovery of pulsations in several CP stars (Martinez et al 2001;Paper I, Joshi et al 2006;Paper II, Joshi et al 2009: Paper III). The present paper is the fourth in this series and presents the null results obtained for 108 stars observed during the period of 2006 to 2009.…”

Section: Introductionmentioning

confidence: 99%

The Nainital-Cape Survey

Joshi

Martinez

Chowdhury

et al. 2016

A&A

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Context. The Nainital-Cape Survey is a dedicated ongoing survey program to search for and study pulsational variability in chemically peculiar (CP) stars to understand their internal structure and evolution. Aims. The main aims of this survey are to find new pulsating Ap and Am stars in the northern and southern hemisphere and to perform asteroseismic studies of these new pulsators. Methods. The survey is conducted using high-speed photometry. The candidate stars were selected on the basis of having Strömgren photometric indices similar to those of known pulsating CP stars. Results. Over the last decade a total of 337 candidate pulsating CP stars were observed for the Nainital-Cape Survey, making it one of the longest ground-based surveys for pulsation in CP stars in terms of time span and sample size. The previous papers of this series presented seven new pulsating variables and 229 null results. In this paper we present the light curves, frequency spectra and various astrophysical parameters of the 108 additional CP stars observed since the last reported results. We also tabulated the basic physical parameters of the known roAp stars. As a part of establishing the detection limits in the Nainital-Cape Survey, we investigated the scintillation noise level at the two observing sites used in this survey, Sutherland and Nainital, by comparing the combined frequency spectra stars observed from each location. Our analysis shows that both the sites permit the detection of variations of the order of 0.6 milli-magnitude (mmag) in the frequency range 1-4 mHz, Sutherland is on average marginally better.

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Section: Introductionmentioning

confidence: 99%

The Nainital-Cape Survey

Joshi

Martinez

Chowdhury

et al. 2016

A&A

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“…Also important is that excitation theories are continuously tested against new observations like the northern hemisphere surveys that have been started recently (Handler & Pauzen, 1999;Martinez et al, 2001). Also, targets appropriate to test these theories should, when possible, be included in the new surveys.…”

Section: Other Exciting Topics and Conclusionmentioning

confidence: 99%

“…They were discovered by Kurtz (1982), and since then the number observed has increased considerably, making today a total of 32 (Martinez et al, 2001). …”

Section: Introductionmentioning

confidence: 99%

Pulsations in roAp Stars

Cunha¹

2002

International Astronomical Union Colloquium

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“…It is well established however that in general, these perturbations occur at frequencies less than 1 or 2 mHz, above which the noise spectrum is approximately flat (see Fig. 2;and Sagar 1999;Martinez & Kurtz 1994;Martinez et al 2001;Joshi 2004;Sagar & Mary 2005;Joshi et al 2006). A schematic representation of the noise peak level generated by atmospheric noise (both the sky transparency variations and scintillation) in the amplitude spectrum obtainable at Manora Peak, NainiTal with the 104-cm Sampurnanand telescope.…”

Section: Remarks Regarding the Validity Of The Modelmentioning

confidence: 97%

“…A collaborative program searching for milli magnitude pulsations in chemically peculiar (CP) stars in the northern hemisphere was initiated in 1997 between NainiTal, India, and Cape Town, South Africa (Martinez 2001;Joshi 2003Joshi , 2004Girish 2004). Pulsating stars form an extremely rich subclass of variable stars.…”

Section: Introductionmentioning

confidence: 99%

A Statistical Analysis of the Detection Limits in Fast Photometry

Mary

2006 IEEE International Conference on Acoustics Speed and Signal Processing Proceedings

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This work investigates the statistical limits for the detection of stellar variability using ground based fast photometry. We show that when sky transparency variations are very low or have been efficiently removed from the raw light curve, the overall noise is of a Mixed Poisson (MP) nature (photon noise mixed by scintillation). As a consequence, three regimes appear for the detection of photometric variations depending on the star's brightness (scintillation, scintillation and photon noise, photon noise and sky background). The proposed analysis is mainly applied to the Indian sites of Manora Peak (existing 104 cm telescope) and Devasthal (future 1 m automated telescope, and 3 m telescope project). As shown by some examples, it can be applied to any site with the corresponding parameters. For 1 m class telescopes at an altitude of about 2000 m, the frontier magnitudes between the different detection regimes are about 10 mag and 15 mag. By analysing the corresponding statistics of the MP noise periodogram, the minimum amplitude variation that one can detect with a given confidence level is evaluated for each observational setting. For example, with a 3 m telescope at about 2500 m, ≈120 µmag variations would be detected in 2 h with a 99% confidence level for stars brighter than magnitude 12. For a star of 15th magnitude, ≈400 µmag oscillations would still be detected at that level. These detection limits are discussed in the light of observations obtained in Manora peak, and compared to results obtained at different astronomical sites.

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The Naini Tal -Cape survey for pulsations in chemically peculiar A-type stars

Cited by 40 publications

References 24 publications

The Nainital-Cape Survey

The Nainital-Cape Survey

Pulsations in roAp Stars

A Statistical Analysis of the Detection Limits in Fast Photometry

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