Discovery of pulsations in the Am star HD 13079

Martinez, Peter; Kurtz, D. W.; Ashoka, B. N.; Chaubey, U. S.; Gupta, S. K.; Leone, F.; Catanzaro, G.; Sagar, Ram; Raj, Edward; Seetha, S.; Kasturirangan, K.

doi:10.1046/j.1365-8711.1999.02896.x

Cited by 18 publications

(13 citation statements)

References 17 publications

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“…During the survey the CP stars HD 13038, HD 13079, HD 98851 and HD 102480 have been discovered to be new δ Sct pulsating variables, while HD 12098 has been discovered to be a rapidly oscillating Ap star. The pulsation properties of HD 13038 (Martinez et al 1999a), HD 13079 (Martinez et al 1999b) and HD 12098 ) have been reported earlier while those of HD 98851 and HD 102480 are presented here. Joshi et al (2000) discovered two main periods of 75 and 150 min for HD 98851.…”

supporting

confidence: 64%

Discovery of unusual pulsations in the cool, evolved Am stars HD 98851 and HD 102480

Joshi¹,

Girish²,

Sagar³

et al. 2003

Monthly Notices RAS

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The chemically peculiar (CP) stars HD 98851 and HD 102480 have been discovered to be unusual pulsators during the ‘Naini Tal–Cape Survey’ programme to search for pulsational variability in CP stars. Time series photometric and spectroscopic observations of these newly discovered stars are reported here. Fourier analyses of the time series photometry reveal that HD 98851 is pulsating mainly with frequencies 0.208 and 0.103 mHz, and HD 102480 is pulsating with frequencies 0.107, 0.156 and 0.198 mHz. The frequency identifications are all subject to 1 d−1 cycle count ambiguities. We have matched the observed low‐resolution spectra of HD 98851 and HD 102480 in the range 3500–7400 Å with theoretical synthetic spectra using Kurucz models with solar metallicity and a micro‐turbulent velocity of 2 km s−1. These yield Teff= 7000 ± 250 K, log g= 3.5 ± 0.5 for HD 98851 and Teff= 6750 ± 250 K, log g= 3.0 ± 0.5 for HD 102480. We determined the equivalent H‐line spectral class of these stars to be F1 IV and F3 III/IV, respectively. A comparison of the location of HD 98851 and HD 102480 in the HR diagram with theoretical stellar evolutionary tracks indicates that both stars are about 1‐Gyr‐old, 2‐M⊙ stars that lie towards the red edge of the δ Sct instability strip. From comparison between the observed and calculated physical parameters, we conclude that HD 98851 and HD 102480 are cool, evolved Am pulsators. The light curves of these pulsating stars have alternating high and low amplitudes, nearly harmonic (or subharmonic) period ratios, high pulsational overtones and Am spectral types. This is unusual for both Am and δ Sct pulsators, making these stars interesting objects for further observational and theoretical studies.

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supporting

confidence: 64%

Discovery of unusual pulsations in the cool, evolved Am stars HD 98851 and HD 102480

Joshi¹,

Girish²,

Sagar³

et al. 2003

Monthly Notices RAS

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“…The original frequency solution for HIP44166 had f 2 1X348 d 21 Y but examination of the spectrum over a wider frequency range showed this to be an artefact induced by the peak at 12.6 d 21 . This probable d Scuti star may be of interest due to its spectroscopic classification as an Am star (see, e.g., Martinez et al 1999).…”

Section: A and F Starsmentioning

confidence: 99%

Multiperiodicities from the Hipparcos epoch photometry and possible pulsation in early A-type stars

Koen

2001

Monthly Notices of the Royal Astronomical Society

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A selection criterion based on the relative strength of the largest peaks in the amplitude spectra, and an information criterion are used in combination to search for multiperiodicities in Hipparcos epoch photometry. The method is applied to all stars which have been classified as variable in the Hipparcos catalogue: periodic, unsolved and microvariables. Results are assessed critically: although there are many problems arising from aliasing, there are also a number of interesting frequency combinations which deserve further investigation. One such result is the possible occurrence of multiple periods of the order of a day in a few early A‐type stars. The Hipparcos catalogue also contains a number of these stars with single periodicities: such stars with no obvious variability classifications are listed, and information about their properties (e.g., radial velocity variations) discussed. These stars may constitute a new class of pulsators.

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“…Indeed, pulsations of the δ-Scuti type 1 have been seen in many Am stars (e.g. Kurtz 1989;Martinez et al 1999;Kurtz & Martinez 2000;Joshi et al 2003;González et al 2008), but our understanding of the physics of pulsating Am stars is still far from being complete. Theoretical models can for instance partially explain that evolved Am stars can pulsate (κ-mechanism in He ii can drive the pulsations in evolved Am stars) and that marginal Am stars can be low-amplitude δ-Scuti stars (a sufficient amount of He remains to drive low-amplitude oscillations).…”

Section: Introductionmentioning

confidence: 99%

The Nainital-Cape Survey

Joshi¹,

Mary²,

Chakradhari³

et al. 2009

A&A

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Context. The Nainital-Cape survey is a dedicated research programme to search for and study the pulsational variability in chemically peculiar stars in the Northern Hemisphere. Aims. The aim of the survey is to search for such chemically peculiar stars that are pulsationally unstable. Methods. The observations of the sample stars were carried out in high-speed photometric mode using a three-channel fast photometer attached to the 1.04-m Sampurnanand telescope at ARIES. Results. The new photometric observations confirmed that the pulsational period of star HD 25515 is 2.78-hrs. The repeated timeseries observations of HD 113878 and HD 118660 revealed that previously known frequencies are indeed present in the new data sets. We have estimated the distances, absolute magnitudes, effective temperatures and luminosities of these stars. Their positions in the H-R diagram indicate that HD 25515 and HD 118660 lie near the main-sequence while HD 113878 is an evolved star. We also present a catalogue of 61 stars classified as null results, along with the corresponding 87 frequency spectra taken from [2002][2003][2004][2005][2006][2007][2008]. A statistical analysis of these null results shows, by comparison with past data, that the power of the noise in the light curves has slightly increased during the last few years.

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Discovery of pulsations in the Am star HD 13079

Cited by 18 publications

References 17 publications

Discovery of unusual pulsations in the cool, evolved Am stars HD 98851 and HD 102480

Discovery of unusual pulsations in the cool, evolved Am stars HD 98851 and HD 102480

Multiperiodicities from the Hipparcos epoch photometry and possible pulsation in early A-type stars

The Nainital-Cape Survey

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