DOCSLIB.ORG

Spectroscopy and Orbital Periods of Four Cataclysmic Variable Stars

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Spectroscopy and Orbital Periods of Four Cataclysmic Variable Stars Dartmouth College Dartmouth Digital Commons Open Dartmouth: Published works by Dartmouth faculty Faculty Work 10-1-2001 Spectroscopy and Orbital Periods of Four Cataclysmic Variable Stars John R. Thorstensen Dartmouth College Cynthia J. Taylor Dartmouth College Follow this and additional works at: https://digitalcommons.dartmouth.edu/facoa Part of the Stars, Interstellar Medium and the Galaxy Commons Dartmouth Digital Commons Citation Thorstensen, John R. and Taylor, Cynthia J., "Spectroscopy and Orbital Periods of Four Cataclysmic Variable Stars" (2001). Open Dartmouth: Published works by Dartmouth faculty. 1868. https://digitalcommons.dartmouth.edu/facoa/1868 This Article is brought to you for free and open access by the Faculty Work at Dartmouth Digital Commons. It has been accepted for inclusion in Open Dartmouth: Published works by Dartmouth faculty by an authorized administrator of Dartmouth Digital Commons. For more information, please contact [email protected]. Mon. Not. R. Astron. Soc. 326, 1235–1242 (2001) Spectroscopy and orbital periods of four cataclysmic variable stars John R. ThorstensenP and Cynthia J. Taylor Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755, USA Accepted 2001 May 2. Received 2001 May 2; in original form 2001 March 29 ABSTRACT We present spectroscopy and orbital periods Porb of four relatively little-studied cataclysmic variable stars. The stars and their periods are: AF Cam, Porb ¼ 0:324ð1Þ d (the daily cycle count is slightly ambiguous); V2069 Cyg (¼ RX J2123.714217), 0.311683(2) d; PG 09351075, 0.1868(3) d; and KUV 0358010614, 0.1495(6) d. V2069 Cyg and KUV 0358010614 both show He II l4686 emission comparable in strength to Hb. V2069 Cyg appears to be a luminous nova-like variable, and the strong He II suggests it may be an intermediate polar. The period of KUV 0358010614 is similar to members of the SW Sex- type nova-like variables, and it shows the phase-dependent absorption in the Balmer and He I lines typical of this subclass. AF Cam shows absorption features from a K-type secondary, as expected given its rather long orbital period. The secondary spectrum and the outburst magnitude both suggest that AF Cam is approximately 1 kpc distant. The spectrum of PG 09351075 resembles that of a dwarf nova at minimum light, with a noticeable contribution from an M-dwarf secondary star. The secondary spectrum and a tentative outburst magnitude both suggest a distance near 500 pc. Key words: binaries: close – stars: fundamental parameters – novae, cataclysmic variables – stars: variables: other. 1 INTRODUCTION 2 TECHNIQUES Cataclysmic variable stars (CVs) are close binary systems in which All the observations (summarized in Table 1) are from the MDM a red dwarf transfers matter on to a white dwarf, generally by Observatory on Kitt Peak, Arizona. The 1998 January observations overflowing its Roche critical lobe. Warner (1995) gives an of KUV 0358010614 are from the 1.3-m McGraw-Hill telescope excellent comprehensive review of CVs. and Mark III spectrograph, and all others are from the 2.4-m The orbital period of a cataclysmic is a fundamental observable Hiltner telescope and modular spectrograph. We observed which correlates with evolutionary state and outburst type. In comparison lamps frequently, and checks of the l5577 night-sky addition, the Ritter & Kolb (1998) catalogue, which is heavily used line show that our wavelength scale is typically stable to by the CV community, includes only those systems with known or ,10 km s21. When the weather appeared photometric, we observed suspected binary periods, with the result that a system remains flux standards in twilight. Even so, our absolute fluxes are not largely ‘beneath the radar’ until a period is measured. Photometry expected to be accurate to much better than 30 per cent, because of yields incontrovertible orbital periods when eclipses are present, occasional clouds and variable losses at the spectrograph slits but other modulations can masquerade as orbital periods. Radial- (1 arcsec at the 2.4 m, 2.2 arcsec at the 1.3 m). Furthermore, for velocity spectroscopy is therefore the most reliable technique for unknown reasons the modular spectrograph produces wavelike determining orbital periods of non-eclipsing CVs. The long distortions in the continua; these appear to average out in sums of cumulative exposures needed to find reliable periods are useful for many exposures. Table 2 contains measurements of the average characterizing the stars in other ways as well. fluxed spectra. We present here spectra and radial velocity periods for four CVs. The data were reduced to counts versus wavelength at the 1 Section 2 details the techniques common to the studies, Section 3 observatory, using standard procedures within IRAF. Radial gives background information and results for the individual stars, velocities of emission lines were measured using convolution and Section 4 contains a brief discussion. algorithms described by Schneider & Young (1980) and Shafter 1 IRAF, the Image Reduction and Analysis Facility, is distributed by the National Optical Astronomy Observatories, under contract to the US PE-mail: [email protected] National Science Foundation. q 2001 RAS Downloaded from https://academic.oup.com/mnras/article-abstract/326/4/1235/1062341 by Dartmouth College Library user on 25 April 2018 1236 J. R. Thorstensen and C. J. Taylor Table 1. Observing log. Run Nights N exposure Range Dl (s) (A˚ )(A˚ ) V2069 Cyg 1997 September 3 23 360 4000–7500 3.7 1997 December 3 12 480 4000–7500 3.7 1998 September 1 3 480 4040–7500 3.7 1999 June 3 9 300 4230–7580 3.6 1999 October 4 7 240 4230–7550 3.9 AF Cam 2000 January 5 32 360 4210–7560 3.6 PG 09351075 1996 April 3 27 480 4208–6780 2.7 2000 January 4 21 480 4210–7560 3.6 KUV 0358010614 1997 December 3 41 480 4000–7500 3.7 1998 January 4 7 900 4845–6865 4.5 1999 October 4 57 480 4230–7560 3.6 Exposure times listed are typical values for each run. Dl is the FWHM resolution determined from fits to night-sky features. (1983). For absorption velocities, we used the cross-correlation was possible for M0. The secondary contribution was 30–40 per algorithms of Tonry & Davis (1979), as implemented in the RVSAO cent of the light near l6500. For the secondary alone we find package (Kurtz & Mink 1998). To search for periods we used the V ¼ 18:4, with an uncertainty estimated from the decomposition ‘residual-gram’ method described by Thorstensen et al. (1996), and and the flux calibration of perhaps ^0.5 mag. to test alias choices in doubtful cases we used the Monte Carlo We cross-correlated the ll5020–5860 and ll5900–6500 method explained by Thorstensen & Freed (1985). With the rough regions against a composite of several G- and K-type IAU radial period established, we fit the velocities with sinusoids, the velocity standards, and obtained velocities for 30 of our 32 target parameters of which are in Table 3. spectra, with typical estimated errors ,20 km s21. We measured We note one simple innovation in these otherwise standard the Ha emission line by convolving with the derivative of procedures. As part of the spectral reduction process, IRAF can Gaussian, optimized for a 16 A˚ FWHM. The counting-statistics estimate the noise in each spectral bin from the readout noise, velocity uncertainties here were typically 10 km s21. Fig. 2 shows detector gain, background, and so on. We have modified the periodograms for the emission and absorption velocities, both of convolution algorithm to compute a counting-statistics uncertainty which favour a period near 0.32 d, but with the inevitable daily in the radial velocities by propagating these noise estimates cycle-count aliases. The Monte Carlo tests give discriminatory through the calculation. These a priori estimates allow the data to powers (defined in Thorstensen & Freed 1985) of 0.96 and 0.83 for be more optimally weighted in period finding and curve fitting. the emission and absorption time series respectively, with correctness likelihoods somewhat higher than this, so the cycle count is reasonably secure, but frequencies differing by 1 cycle d21 3 THE INDIVIDUAL STARS cannot be excluded absolutely. The data span 7.8 h of hour angle, ordinarily enough to decide daily cycle counts unambiguously, but 3.1 AF Camelopardalis the sampling is somewhat sparse and the period is awkwardly close This object is listed in the General Catalog of Variable stars to an integer submultiple of one day. On the face of it, Szkody & (Kholopov et al. 1988) as a U Gem-type dwarf nova with Howell’s (1989) 5–6 h period favours the ,4 cycle d21 alias, rather 21 13:4 # mpg # 17:6. It is the only star here with a useful period than the ,3 cycle d we adopt; however, their data do not have estimate in the literature. Early indications of a very short period enough hour angle span to influence the choice. (Szkody & Mateo 1986, Howell & Szkody 1988) prompted an Fig. 3 shows the velocities folded on the combined best period. emission-line radial velocity study by Szkody & Howell (1989). The sine fits (Table 3) show that the emission-line velocity They obtained very limited data which indicated a 5–6 h period, modulation lags the absorption-line velocities by 0:54 ^ 0:02 leading Ritter & Kolb (1998) to tabulate Porb ¼ 0:23: in their cycles, suggesting as usual that the emission lines do not trace the catalogue. white dwarf motion with any precision. We observed this object in 2000 January, in quiescence. The The secondary velocity amplitude suggests a fairly low orbital mean spectrum (Fig. 1) shows the absorption features of a late-type inclination, as might be expected from the single-peaked emission 21 secondary star, as would be expected given the relatively long Porb.
Load more

Recommended publications
  • White Dwarfs and Electron Degeneracy
    White Dwarfs and Electron Degeneracy Farley V. Ferrante Southern Methodist University Sirius A and B 27 March 2017 SMU PHYSICS 1 Outline • Stellar astrophysics • White dwarfs • Dwarf novae • Classical novae • Supernovae • Neutron stars 27 March 2017 SMU PHYSICS 2 27 March 2017 SMU PHYSICS 3 Pogson’s ratio: 5 100≈ 2.512 27 March 2017 M.S. Physics Thesis Presentation 4 Distance Modulus mM−=5 log10 ( d) − 1 • Absolute magnitude (M) • Apparent magnitude of an object at a standard luminosity distance of exactly 10.0 parsecs (~32.6 ly) from the observer on Earth • Allows true luminosity of astronomical objects to be compared without regard to their distances • Unit: parsec (pc) • Distance at which 1 AU subtends an angle of 1″ • 1 AU = 149 597 870 700 m (≈1.50 x 108 km) • 1 pc ≈ 3.26 ly • 1 pc ≈ 206 265 AU 27 March 2017 SMU PHYSICS 5 Stellar Astrophysics • Stefan-Boltzmann Law: 54 2π k − − −− FT=σσ4; = = 5.67x 10 5 ergs 1 cm 24 K bol 15ch23 • Effective temperature of a star: Temp. of a black body with the same luminosity per surface area • Stars can be treated as black body radiators to a good approximation • Effective surface temperature can be obtained from the B-V color index with the Ballesteros equation: 11 T = 4600+ 0.92(BV−+) 1.70 0.92(BV −+) 0.62 • Luminosity: 24 L= 4πσ rT* E 27 March 2017 SMU PHYSICS 6 H-R Diagram 27 March 2017 SMU PHYSICS 8 27 March 2017 SMU PHYSICS 9 White dwarf • Core of solar mass star • Pauli exclusion principle: Electron degeneracy • Degenerate Fermi gas of oxygen and carbon • 1 teaspoon would weigh 5 tons • No energy produced from fusion or gravitational contraction Hot white dwarf NGC 2440.
    [Show full text]
  • The Inter-Eruption Timescale of Classical Novae from Expansion of the Z Camelopardalis Shell
    The Astrophysical Journal, 756:107 (6pp), 2012 September 10 doi:10.1088/0004-637X/756/2/107 C 2012. The American Astronomical Society. All rights reserved. Printed in the U.S.A. THE INTER-ERUPTION TIMESCALE OF CLASSICAL NOVAE FROM EXPANSION OF THE Z CAMELOPARDALIS SHELL Michael M. Shara1,4, Trisha Mizusawa1, David Zurek1,4, Christopher D. Martin2, James D. Neill2, and Mark Seibert3 1 Department of Astrophysics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024-5192, USA 2 Department of Physics, Math and Astronomy, California Institute of Technology, 1200 East California Boulevard, Mail Code 405-47, Pasadena, CA 91125, USA 3 Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101, USA Received 2012 May 14; accepted 2012 July 9; published 2012 August 21 ABSTRACT The dwarf nova Z Camelopardalis is surrounded by the largest known classical nova shell. This shell demonstrates that at least some dwarf novae must have undergone classical nova eruptions in the past, and that at least some classical novae become dwarf novae long after their nova thermonuclear outbursts. The current size of the shell, its known distance, and the largest observed nova ejection velocity set a lower limit to the time since Z Cam’s last outburst of 220 years. The radius of the brightest part of Z Cam’s shell is currently ∼880 arcsec. No expansion of the radius of the brightest part of the ejecta was detected, with an upper limit of 0.17 arcsec yr−1. This suggests that the last Z Cam eruption occurred 5000 years ago.
    [Show full text]
  • AT Cnc: a SECOND DWARF NOVA with a CLASSICAL NOVA SHELL
    The Astrophysical Journal, 758:121 (5pp), 2012 October 20 doi:10.1088/0004-637X/758/2/121 C 2012. The American Astronomical Society. All rights reserved. Printed in the U.S.A. AT Cnc: A SECOND DWARF NOVA WITH A CLASSICAL NOVA SHELL Michael M. Shara1,5, Trisha Mizusawa1, Peter Wehinger2, David Zurek1,5,6, Christopher D. Martin3, James D. Neill3, Karl Forster3, and Mark Seibert4 1 Department of Astrophysics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024-5192, USA 2 Steward Observatory, the University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA 3 Department of Physics, Math and Astronomy, California Institute of Technology, 1200 East California Boulevard, Mail Code 405-47, Pasadena, CA 91125, USA 4 Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101, USA Received 2012 July 31; accepted 2012 August 23; published 2012 October 8 ABSTRACT We are systematically surveying all known and suspected Z Cam-type dwarf novae for classical nova shells. This survey is motivated by the discovery of the largest known classical nova shell, which surrounds the archetypal dwarf nova Z Camelopardalis. The Z Cam shell demonstrates that at least some dwarf novae must have undergone classical nova eruptions in the past, and that at least some classical novae become dwarf novae long after their nova thermonuclear outbursts, in accord with the hibernation scenario of cataclysmic binaries. Here we report the detection of a fragmented “shell,” 3 arcmin in diameter, surrounding the dwarf nova AT Cancri. This second discovery demonstrates that nova shells surrounding Z Cam-type dwarf novae cannot be very rare.
    [Show full text]
  • A Review of the Disc Instability Model for Dwarf Novae, Soft X-Ray Transients and Related Objects a J.M
    A review of the disc instability model for dwarf novae, soft X-ray transients and related objects a J.M. Hameury aObservatoire Astronomique de Strasbourg ARTICLEINFO ABSTRACT Keywords: I review the basics of the disc instability model (DIM) for dwarf novae and soft-X-ray transients Cataclysmic variable and its most recent developments, as well as the current limitations of the model, focusing on the Accretion discs dwarf nova case. Although the DIM uses the Shakura-Sunyaev prescription for angular momentum X-ray binaries transport, which we know now to be at best inaccurate, it is surprisingly efficient in reproducing the outbursts of dwarf novae and soft X-ray transients, provided that some ingredients, such as irradiation of the accretion disc and of the donor star, mass transfer variations, truncation of the inner disc, etc., are added to the basic model. As recently realized, taking into account the existence of winds and outflows and of the torque they exert on the accretion disc may significantly impact the model. I also discuss the origin of the superoutbursts that are probably due to a combination of variations of the mass transfer rate and of a tidal instability. I finally mention a number of unsolved problems and caveats, among which the most embarrassing one is the modelling of the low state. Despite significant progresses in the past few years both on our understanding of angular momentum transport, the DIM is still needed for understanding transient systems. 1. Introduction tems using Doppler tomography techniques (Steeghs et al. 1997; Marsh and Horne 1988; see also Marsh and Schwope Dwarf novae (DNe) are cataclysmic variables (CV) that 2016 for a recent review).
    [Show full text]
  • The SAI Catalog of Supernovae and Radial Distributions of Supernovae
    Astronomy Letters, Vol. 30, No. 11, 2004, pp. 729–736. Translated from Pis’ma v Astronomicheski˘ı Zhurnal, Vol. 30, No. 11, 2004, pp. 803–811. Original Russian Text Copyright c 2004 by Tsvetkov, Pavlyuk, Bartunov. TheSAICatalogofSupernovaeandRadialDistributions of Supernovae of Various Types in Galaxies D. Yu. Tsvetkov*, N.N.Pavlyuk**,andO.S.Bartunov*** Sternberg Astronomical Institute, Universitetski ˘ı pr. 13, Moscow, 119992 Russia Received May 18, 2004 Abstract—We describe the Sternberg Astronomical Institute (SAI)catalog of supernovae. We show that the radial distributions of type-Ia, type-Ibc, and type-II supernovae differ in the central parts of spiral galaxies and are similar in their outer regions, while the radial distribution of type-Ia supernovae in elliptical galaxies differs from that in spiral and lenticular galaxies. We give a list of the supernovae that are farthest from the galactic centers, estimate their relative explosion rate, and discuss their possible origins. c 2004MAIK “Nauka/Interperiodica”. Key words: astronomical catalogs, supernovae, observations, radial distributions of supernovae. INTRODUCTION be found on the Internet. The most complete data are contained in the list of SNe maintained by the Cen- In recent years, interest in studying supernovae (SNe)has increased signi ficantly. Among other rea- tral Bureau of Astronomical Telegrams (http://cfa- sons, this is because SNe Ia are used as “standard www.harvard.edu/cfa/ps/lists/Supernovae.html)and candles” for constructing distance scales and for cos- the electronic version of the Asiago catalog mological studies, and because SNe Ibc may be re- (http://web.pd.astro.it/supern). lated to gamma ray bursts.
    [Show full text]
  • V2487 Oph 1998: a Post Nova in an Intermediate Polar
    EPJ Web of Conferences 64, 07002 (2014) DOI: 10.1051/epjconf/20146407002 C Owned by the authors, published by EDP Sciences, 2014 V2487 Oph 1998: a post nova in an intermediate polar Margarita Hernanz1;a 1Institute of Space Sciences - ICE (CSIC-IEEC), Campus UAB, Fac. Ciències, C5 par 2a pl., 08193 Bellaterra (Barcelona), Spain Abstract. V2487 Oph (Nova Oph 1998) is a classical nova that exploded in 1998. XMM-Newton observations performed between 2 and 9 years after the explosion showed emission related to restablished accretion, and indicative of a magnetic white dwarf. The spectrum looks like that of a cataclysmic variable of the intermediate polar type. Anyway, we don’t have yet a definitive confirmation of the intermediate polar character, through determination of spin and orbital periods. Although it is not the first nova exploding in a magnetic white dwarf, it is always challenging to reach explosive conditions when a stan- dard accretion disk can’t be formed, because of the magnetic field. In addition, V2487 Oph has been the first nova where a detection of X-rays - in the host binary system - has been reported prior to its eruption, in 1990 with the ROSAT satellite. V2487 Oph has been also detected in hard X-rays with INTEGRAL/IBIS and RXTE/PCA. Last but not least, V2487 Oph has been identified as a recurrent nova in 2008, since a prior eruption in 1900 has been reported through analysis of Harvard photographic plates. Therefore, it is expected to host a massive white dwarf and be a candidate for a type Ia supernova explo- sion.
    [Show full text]
  • An Observational Argument Against Accretion in Magnetars
    Astronomy & Astrophysics manuscript no. start c ESO 2020 September 30, 2020 An observational argument against accretion in magnetars V.Doroshenko1; 2, A. Santangelo1, V. F. Suleimanov1; 2; 3, and S. S. Tsygankov4; 2 1 Institut für Astronomie und Astrophysik, Sand 1, 72076 Tübingen, Germany 2 Space Research Institute of the Russian Academy of Sciences, Profsoyuznaya Str. 84/32, Moscow 117997, Russia 3 Astronomy Department, Kazan (Volga region) Federal University, Kremlyovskaya str. 18, 420008 Kazan, Russia 4 Department of Physics and Astronomy, FI-20014 University of Turku, Finland September 30, 2020 ABSTRACT The phenomenology of anomalous X-ray pulsars is usually interpreted within the paradigm of very highly magnetized neutron stars, also known as magnetars. According to this paradigm, the persistent emission of anomalous X-ray pulsars (AXPs) is powered by the decay of the magnetic field. However, an alternative scenario in which the persistent emission is explained through accretion is also discussed in literature. In particular, AXP 4U 0142+61 has been suggested to be either an accreting neutron star or a white dwarf. Here, we rule out this scenario based on the the observed X-ray variability properties of the source. We directly compare the observed power spectra of 4U 0142+61 and of two other magnetars, 1RXS J170849.0−400910 and 1E 1841−045 with that of the X-ray pulsar 1A 0535+262, and of the intermediate polar GK Persei. In addition, we include a bright young radio pulsar PSR B1509-58 for comparison. We show that, unlike accreting sources, no aperiodic variability within the expected frequency range is observed in the power density spectrum of the magnetars and the radio pulsar.
    [Show full text]
  • Cosmic Catastrophes Wheeler 309N Spring 2008 April 7, 2008 (49490) Review for Test #3 Neutron Stars and Black Holes
    Cosmic Catastrophes Wheeler 309N Spring 2008 April 7, 2008 (49490) Review for Test #3 Neutron Stars and Black Holes Neutron stars – mass of sun, radius ~ 10km, density like atomic nucleus, huge gravity at surface. Discovery of pulsars – pulsating radio sources Interpretation of pulsars as rotating magnetized neutron stars Role of magnetic field to cause radiation, misalignment of rotation axis, magnetic axis Production of pulses – probably related to strong electric, magnetic fields at magnetic poles About 600 pulsars known, perhaps a billion neutron stars in the Galaxy. Pressure support from quantum pressure of neutrons plus nuclear repulsion. Maximum mass of neutron star about 2 solar masses. Neutron stars as binary X-rays sources. X-ray pulsars – accreted gas channeled to magnetic poles, “pulsar” by lighthouse effect if magnetic axis is tilted with respect to the spin axis. X-ray transients – 4 or 5 known in our Galaxy. Outburst every few years for a month. Probably a disk instability like a dwarf nova, but with the white dwarf replaced by a neutron star. X-ray Bursters – about 30 known in our Galaxy. Burst every few hours for minutes. Probably the neutron star analog of a classical nova. Matter accretes on surface of neutron star. Hydrogen is supported by thermal pressure, burns to helium. Helium is supported by quantum pressure and is unregulated and explodes, producing the X-rays. Magnetars – neutron stars with magnetic fields 100 to 1000 times stronger than the Crab nebula pulsar. Soft gamm-ray repeaters – objects that emit intense bursts of low energy gamma rays and X-rays for a few minutes every few years.
    [Show full text]
  • Nova V4743 Sagittarii 2002: an Intermediate Polar Candidate
    Draft version March 30, 2021 A Preprint typeset using LTEX style emulateapj v. 6/22/04 NOVA V4743 SAGITTARII 2002: AN INTERMEDIATE POLAR CANDIDATE Tae W. Kang1, Alon Retter1, Alex Liu2, and Mercedes Richards1 1Dept. of Astronomy & Astrophysics, Penn State University, 525 Davey Lab, University Park, PA 16802; [email protected]; [email protected]; [email protected] and 2Norcape Observatory, PO Box 300, Exmouth, 6707, Australia; [email protected] Draft version March 30, 2021 ABSTRACT 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 the transition phase in novae may be related to intermediate polars.
    [Show full text]
  • Cataclysmic Variables
    Cataclysmic variables Article (Accepted Version) Smith, Robert Connon (2006) Cataclysmic variables. Contemporary Physics, 47 (6). pp. 363-386. ISSN 0010-7514 This version is available from Sussex Research Online: http://sro.sussex.ac.uk/id/eprint/2256/ This document is made available in accordance with publisher policies and may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher’s version. Please see the URL above for details on accessing the published version. Copyright and reuse: Sussex Research Online is a digital repository of the research output of the University. Copyright and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable, the material made available in SRO has been checked for eligibility before being made available. Copies of full text items generally can be reproduced, displayed or performed and given to third parties in any format or medium for personal research or study, educational, or not-for-profit purposes without prior permission or charge, provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. http://sro.sussex.ac.uk Cataclysmic variables Robert Connon Smith Department of Physics and Astronomy, University of Sussex, Falmer, Brighton BN1 9QH, UK E-mail: [email protected] Abstract. Cataclysmic variables are binary stars in which a relatively normal star is transferring mass to its compact companion.
    [Show full text]
  • Near-Infrared Spectroscopy of 20 New Chandra Sources in the Norma Arm
    A&A 568, A54 (2014) Astronomy DOI: 10.1051/0004-6361/201424006 & c ESO 2014 Astrophysics Near-infrared spectroscopy of 20 new Chandra sources in the Norma arm F. Rahoui1,2,J.A.Tomsick3, F. M. Fornasini3,4, A. Bodaghee3,5, and F. E. Bauer6,7,8 1 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany e-mail: [email protected] 2 Harvard University, Department of Astronomy, 60 Garden street, Cambridge MA 02138, USA 3 Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley CA 94720-7450, USA 4 Astronomy Department, University of California, 601 Campbell Hall, Berkeley CA 94720, USA 5 Department of Chemistry, Physics, and Astronomy, Georgia College & State University CBX 82, Milledgeville GA 31061, USA 6 Instituto de Astrofísica, Facultad de Física, Pontifica Universidad Católica de Chile, 306 Santiago 22, Chile 7 Millennium Institute of Astrophysics 8 Space Science Institute, 4750 Walnut Street, Suite 205, Boulder CO 80301, USA Received 16 April 2014 / Accepted 4 June 2014 ABSTRACT We report on CTIO/NEWFIRM and CTIO/OSIRIS photometric and spectroscopic observations of 20 new X-ray (0.5–10 keV) emit- ters discovered in the Norma arm Region Chandra Survey (NARCS). NEWFIRM photometry was obtained to pinpoint the near- infrared counterparts of NARCS sources, while OSIRIS spectroscopy was used to help identify 20 sources with possible high mass X-ray binary properties. We find that (1) two sources are WN8 Wolf-Rayet stars, maybe in colliding wind binaries, part of the mas- sive star cluster Mercer
    [Show full text]
  • Variable Star
    Variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) fluctuates. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as either: Intrinsic variables, whose luminosity actually changes; for example, because the star periodically swells and shrinks. Extrinsic variables, whose apparent changes in brightness are due to changes in the amount of their light that can reach Earth; for example, because the star has an orbiting companion that sometimes Trifid Nebula contains Cepheid variable stars eclipses it. Many, possibly most, stars have at least some variation in luminosity: the energy output of our Sun, for example, varies by about 0.1% over an 11-year solar cycle.[1] Contents Discovery Detecting variability Variable star observations Interpretation of observations Nomenclature Classification Intrinsic variable stars Pulsating variable stars Eruptive variable stars Cataclysmic or explosive variable stars Extrinsic variable stars Rotating variable stars Eclipsing binaries Planetary transits See also References External links Discovery An ancient Egyptian calendar of lucky and unlucky days composed some 3,200 years ago may be the oldest preserved historical document of the discovery of a variable star, the eclipsing binary Algol.[2][3][4] Of the modern astronomers, the first variable star was identified in 1638 when Johannes Holwarda noticed that Omicron Ceti (later named Mira) pulsated in a cycle taking 11 months; the star had previously been described as a nova by David Fabricius in 1596. This discovery, combined with supernovae observed in 1572 and 1604, proved that the starry sky was not eternally invariable as Aristotle and other ancient philosophers had taught.
    [Show full text]