Alon Retter

Preprint typeset using L ATEX style emulateapj v. 14/09/00 A TIGHT UPPER LIMIT ON OSCILLATIONS IN THE AP STAR ǫ URSAE MAJORIS FROM WIRE

Observations of ǫ UMa obtained with the star tracker on the Wide Field Infrared Explorer (WIRE) s... more Observations of ǫ UMa obtained with the star tracker on the Wide Field Infrared Explorer (WIRE) satellite during a month in mid-2000 are analyzed. This is one of the most precise photometry of an Ap star. The amplitude spectrum is used to set an upper limit of 75 parts per million for the amplitude of stellar pulsations in this star unless it accidentally oscillates with a single mode at the satellite orbit, its harmonics or their one day aliases. This is the tightest limit put on the amplitude of oscillations in an Ap star. As the rotation period of ǫ UMa is relatively short (5.1 d), it cannot be argued that the observations were made at a wrong rotational phase. Our results thus support the idea that some Ap stars do not pulsate at all. Subject headings: stars: individuals (ǫ UMa)—stars: oscillations

Preprint typeset using L ATEX style emulateapj v. 14/09/00 OSCILLATIONS IN ARCTURUS FROM WIRE PHOTOMETRY

Observations of the red giant Arcturus (α Boo) obtained with the star tracker on the Wide Field I... more Observations of the red giant Arcturus (α Boo) obtained with the star tracker on the Wide Field Infrared Explorer (WIRE) satellite during a baseline of 19 successive days in 2000 July-August are analysed. The amplitude spectrum has a significant excess of power at low-frequencies. The highest peak is at ∼ 4.1 µHz (2.8 d), which is in agreement with previous ground-based radial velocity studies. The variability of Arcturus can be explained by sound waves, but it is not clear whether these are coherent p-mode oscillations or a single mode with a short life-time.

158 Publications 1,284 Citations See Profile

A model of an expanding giant that swallowed planets for the eruption of V838 Monocerotis

V705 Cassiopeiae

RI light curves of V1493 Aql (Dobrotka+, 2006)

Photometric observations of the nova V1493 Aquilae performed a few weeks after maximum is present... more

GRB 060203: Swift/UVOT upper limits

A study of RW Ursae Minoris shell

Astronomy & Astrophysics - ASTRON ASTROPHYS, 2000

We find an expansion parallax for the slow nova RW UMi (Nova Ursae Minoris 1956). A narrow-band H... more We find an expansion parallax for the slow nova RW UMi (Nova Ursae Minoris 1956). A narrow-band Halpha image shows that the diameter of the nova shell in 1995 was 2.94+0.37-0.49 arcsec. We derive a distance of 5250+590-1050 pc, and an absolute magnitude at maximum of Mv = -7.7+0.3-0.4 which are consistent with previous estimates for the nova. We also revised known relations between various parameters of nova systems.

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Nova Sagittarii 2002: An Intermediate Polar Candidate

We present the results of 11 nights of CCD photometry of V4743 Sgr (Nova Sagittarii 2002) from 20... more We present the results of 11 nights of CCD photometry of V4743 Sgr (Nova Sagittarii 2002) from 2003 and 2005. Two periods of 6.7 hours and 24 min were identified in the 2005 data. The 2003 data also showed evidence of the longer period but only weak evidence of the shorter period. We suggest that the 6.7-hour periodicity represents the orbital period of the underlying binary system and that the 24-min period is the beat periodicity between the orbital period and the 22-min X-ray period, which is presumably the spin period of the white dwarf. Intermediate polars are a subset of the Am Her stars in which the spin period is much shorter than the orbital period, so we propose that V4743 Sgr is a member of this group.

Photometric Evidence for the Intermediate Polar Nature and for Accretion Activity in Nova V1425 Aquilae 1995 Shortly After its Outburst

Wild Stars in the Old West, 1998

... to Intermediate Polars systems. Here we check further the characteristic of the novaas an Int... more

CCD Photometry of V2275 Cygni (N Cyg 2001 No.2) in 2002-2003

We present the CCD photometry, light curve and time series analysis of the classical nova V2275 C... more We present the CCD photometry, light curve and time series analysis of the classical nova V2275 Cyg. The source is observed for 14 nights in total using standard R filters in 2002 and 2003 with the 1.5 m Russian-Turkish joint telescope (RTT150) at the TUBITAK National Observatory (TUG) in Antalya Turkey. We report the detection of two periodicities in the light curve of the nova : a) P1=0.31449(15) d, b) P2=0.017079(17) d. We propose that the first period is the orbital period of the system as a result of the aspect changes of the secondary irradiated by the hot WD. The second period could be a QPO originating from the oscillation of the ionization front below the inner Lagrange point as predicted by King (1989) or could be a QPO/beat period related to the magnetic nature of the WD.

Preprint typeset using L ATEX style emulateapj v. 14/09/00 OSCILLATIONS IN ARCTURUS FROM WIRE PHOTOMETRY

Observations of the red giant Arcturus (α Boo) obtained with the star tracker on the Wide Field I... more Observations of the red giant Arcturus (α Boo) obtained with the star tracker on the Wide Field Infrared Explorer (WIRE) satellite during a baseline of 19 successive days in 2000 July-August are analysed. The amplitude spectrum has a significant excess of power at low-frequencies. The highest peak is at ∼ 4.1 µHz (2.8 d), which is in agreement with previous ground-based radial velocity studies. The variability of Arcturus can be explained by sound waves, but it is not clear whether these are coherent p-mode oscillations or a single mode with a short life-time.

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**TITLE** ASP Conference Series, Vol. **VOLUME**, **PUBLICATION YEAR** **EDITORS** Does TV Col Have the longest Recorded Positive

Abstract. Re-examination of extensive photometric data of TV Col reveals evidence for a permanent... more Abstract. Re-examination of extensive photometric data of TV Col reveals evidence for a permanent positive superhump. Its period (6.4 h) is 16 percent longer than the orbital period and obeys the well known relation between superhump period excess and binary period. At 5.5h, TV Col has an orbital period longer than any known superhumping cataclysmic variable and, therefore, a mass ratio which might be outside the range at which superhumps can occur according to the current theory. We suggest several solutions for this problem. 1.

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Preprint typeset using L ATEX style emulateapj v. 6/22/04 NOVA V4743 SAGITTARII 2002: AN INTERMEDIATE POLAR CANDIDATE

We present the results of 11 nights of CCD unfiltered photometry of V4743 Sgr (Nova Sgr 2002 # 3)... more We present the results of 11 nights of CCD unfiltered photometry of V4743 Sgr (Nova Sgr 2002 # 3) from 2003 and 2005. We find two periods of 0.2799 d ≈ 6.7 h and 0.01642 d ≈ 24 min in the 2005 data. The long period is also present in the 2003 data, but only weak evidence of the shorter period is found in this year. The 24-min period is somewhat longer than the 22-min period, which was detected from X-ray observations. We suggest that the 6.7-h periodicity represents the orbital period of the underlying binary system and that the 24-min period is the beat periodicity between the orbital period and the X-ray period, which is presumably the spin period of the white dwarf. Thus, V4743 Sgr should be classified as an intermediate polar (DQ Her star). About six months after the nova outburst, the optical light curve of V4743 Sgr seemed to show quasi-periodic oscillations, which are typical of the transient phase in classical nova. Therefore, our results support the previous suggestion that...

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Two new accreting, pulsating white dwarfs

We report the discovery of rapid periodic signals in the light curves of two cataclysmic variable... more We report the discovery of rapid periodic signals in the light curves of two cataclysmic variables with prominent white-dwarf components in their spectra, SDSS J1457+51 and BW Sculptoris. These stars therefore appear to be new members of the GW Lib class of variable star, in which the fast periodic (and non-commensurate with the orbital period) signals are believed to arise from non-radial pulsations in the underlying white dwarf. The power spectra of both stars show complex signals with primary periods near 10 and 20 minutes. These signals change in frequency by a few percent on a timescale of weeks or less, and probably contain an internal fine structure unresolved by our observations. We also detect double-humped waves signifying the underlying orbital periods, near 78 minutes for both stars. In addition, BW Scl shows a transient but powerful signal with a period near 87 minutes, a quiescent superhump. The ∼ 11% excess over the orbital period is difficult to understand, and may arise from an eccentric instability near the 2:1 resonance in the accretion disc.

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Preprint typeset using L ATEX style emulateapj v. 14/09/00 A TIGHT UPPER LIMIT ON OSCILLATIONS IN THE AP STAR ǫ URSAE MAJORIS FROM WIRE

Observations of ǫ UMa obtained with the star tracker on the Wide Field Infrared Explorer (WIRE) s... more Observations of ǫ UMa obtained with the star tracker on the Wide Field Infrared Explorer (WIRE) satellite during a month in mid-2000 are analyzed. This is one of the most precise photometry of an Ap star. The amplitude spectrum is used to set an upper limit of 75 parts per million for the amplitude of stellar pulsations in this star unless it accidentally oscillates with a single mode at the satellite orbit, its harmonics or their one day aliases. This is the tightest limit put on the amplitude of oscillations in an Ap star. As the rotation period of ǫ UMa is relatively short (5.1 d), it cannot be argued that the observations were made at a wrong rotational phase. Our results thus support the idea that some Ap stars do not pulsate at all. Subject headings: stars: individuals (ǫ UMa)—stars: oscillations

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Observation of Superhumps in SS UMi

Nova MUSCAE 1998

ABSTRACT

GRB 060102: Swift-BAT detection of a burst

GRB 060204C: XRT analysis of swift J061223.0+701243.9

Classical novae as WET objects

Open Astronomy, 1995

By two examples, we demonstrate that some classical novae may be suitable and worthwhile objects ... more

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