We present time-resolved spectroscopy of the eclipsing, short period cataclysmic variable CTCV J1300-3052. Using absorption features from the secondary star, we determine the radial velocity ...semi-amplitude of the secondary star to be K2 = 378 \pm 6 km/s, and its projected rotational velocity to be v sin i = 125 \pm 7 km/s. Using these parameters and Monte Carlo techniques, we obtain masses of M1 = 0.79 \pm 0.05 MSun for the white dwarf primary and M2 = 0.198 \pm 0.029 MSun for the M-type secondary star. These parameters are found to be in excellent agreement with previous mass determinations found via photometric fitting techniques, supporting the accuracy and validity of photometric mass determinations in short period CVs.
Stars with masses in the range 7-10Msun end their lives either as massive white dwarfs or weak type II supernovae, and there are only limited observational constraints of either channel. Here we ...report the detection of two white dwarfs with large photospheric oxygen abundances, implying that they are bare oxygen-neon cores and that they may have descended from the most massive progenitors that avoid core-collapse.
We present optical lightcurves, spectroscopy, and classification of five X-ray sources in the Chandra Galactic Bulge Survey CXOGBS J174009.1-284725 (CX5), CXOGBS J173935.7-272935 (CX18), CXOGBS ...J173946.9-271809 (CX28), CXOGBS J173729.1-292804 (CX37), CXOGBS J174607.6-261547 (CX561). These objects were selected based on bright optical counterparts which were quickly found to have emission lines in their optical spectra. This paper presents an illustration of GBS optical follow-up, targeting emission line objects. Of these five objects, four exhibit photometric variability in the Sloan r' band. CX5 shows a tentative period of 2.1 hours and is clearly an Intermediate Polar (IP). CX28 and CX37 both exhibit flickering with no clear period. Both are suggested to also be IPs. CX18 was observed to undergo 2 dwarf nova outbursts. Finally, CX561 shows no detectable variability, although its characteristics would be consistent with either a quiescent Low Mass X-ray Binary or Cataclysmic Variable.
We present an analysis of candidate members of the Eta Cha and MBM 12A young associations. For an area of 0.7 deg^2 toward Eta Cha, we have performed a search for members of the association by ...combining JHK_s photometry from 2MASS and i photometry from DENIS with followup optical spectroscopy at Magellan Observatory. We report the discovery of three new members with spectral types of M5.25-M5.75, corresponding to masses of 0.13-0.08 M_sun by theoretical evolutionary models. Two and three of these members were found independently by Lyo and coworkers and Song and coworkers, respectively. Meanwhile, no brown dwarfs were detected in Eta Cha down to the completeness limit of 0.015 M_sun. For MBM 12A, we have obtained spectra of three of the remaining candidate members that lacked spectroscopy at the end of the survey by Luhman, all of which are found to be field M dwarfs. Ogura and coworkers have recently presented four "probable" members of MBM 12A. However, two of these objects were previously classified as field dwarfs by the spectroscopy of Luhman. In this work, we find that the other two objects are field dwarfs as well.
We present time-resolved spectroscopy and photometry of the dwarf nova SBSS 1108+574, obtained during the 2012 outburst. Its quiescent spectrum is unusually rich in helium, showing broad, ...double-peaked emission lines from the accretion disc. We measure a line flux ratio HeI 5875/Halpha = 0.81 +/- 0.04, a much higher ratio than typically observed in cataclysmic variables (CVs). The outburst spectrum shows hydrogen and helium in absorption, with weak emission of Halpha and HeI 6678, as well as strong HeII emission. From our photometry, we find the superhump period to be 56.34 +/- 0.18 minutes, in agreement with the previously published result. The spectroscopic period, derived from the radial velocities of the emission lines, is found to be 55.3 +/- 0.8 minutes, consistent with a previously identified photometric orbital period, and significantly below the normal CV period minimum. This indicates that the donor in SBSS 1108+574 is highly evolved. The superhump excess derived from our photometry implies a mass ratio of q = 0.086 +/- 0.014. Our spectroscopy reveals a grazing eclipse of the large outbursting disc. As the disc is significantly larger during outburst, it is unlikely that an eclipse will be detectable in quiescence. The relatively high accretion rate implied by the detection of outbursts, together with the large mass ratio, suggests that SBSS 1108+574 is still evolving towards its period minimum.
We analyse a unique set of time-resolved echelle spectra of the dwarf nova IP Peg, obtained at ESO's NTT with EMMI. The dataset covers the wavelength range of 4000-7500A and shows Balmer, HeI, HeII ...and heavier elements in emission. IP Peg was observed one day after the peak of an outburst. The trailed spectra, spectrograms and Doppler maps show characteristics typical of IP Pegasi during the early stages of its outburst. The high-ionisation line of HeII 4686A is the most centrally located line and has the greatest radial extension compared to the HeI lines. The Balmer lines extend from close to the white dwarf up to approximately 0.45 times R_L, with the outer radius gradually increasing when moving from H delta to H alpha. The application, for the first time, of the modulation Doppler tomography technique, maps any harmonically varying components present in the system configuration. We find, as expected, that part of the strong secondary star emission in Balmer and HeI lines is modulated predominantly with the cosine term, consistent with the emission originating from the irradiated front side of the mass-donor star, facing the accreting white dwarf. For the Balmer lines the level of the modulation, compared to the average emission, decreases when moving to higher series. Emission from the extended accretion disk appears to be only weakly modulated, with amplitudes of at most a few percent of the non-varying disk emission. We find no evidence of modulated emission in the spiral arms, which if present, is relatively weak at that our signal-to-noise ratio was good enough to put a lower detection limit of any modulated emission at 5--6%. Only in one arm of the HeII 4686A line, is there a possibility of modulated emission, but again, we cannot be sure this is not caused by blending with the nearby Bowen complex of lines.
We present the latest results from a spectroscopic survey designed to uncover the hidden population of AM Canum Venaticorum (AM CVn) binaries in the photometric database of the Sloan Digital Sky ...Survey (SDSS). We selected ~2000 candidates based on their photometric colours, a relatively small sample which is expected to contain the majority of all AM CVn binaries in the SDSS (expected to be ~50). We present two new candidate AM CVn binaries discovered using this strategy: SDSS J104325.08+563258.1 and SDSS J173047.59+554518.5. We also present spectra of 29 new cataclysmic variables, 23 DQ white dwarfs and 21 DZ white dwarfs discovered in this survey. The survey is now approximately 70 per cent complete, and the discovery of seven new AM CVn binaries indicates a lower space density than previously predicted. From the essentially complete g <= 19 sample, we derive an observed space density of (5 +/- 3) x10^-7 pc^-3; this is lower than previous estimates by a factor of 3. The sample has been cross-matched with the GALEX All-Sky Imaging Survey database, and with Data Release 9 of the UKIRT (United Kingdom Infrared Telescope) Infrared Deep Sky Survey (UKIDSS). The addition of UV photometry allows new colour cuts to be applied, reducing the size of our sample to ~1100 objects. Optimising our followup should allow us to uncover the remaining AM CVn binaries present in the SDSS, providing the larger homogeneous sample required to more reliably estimate their space density.
We present a short overview of the properties of faint Galactic X-ray binaries. We place emphasis on current classification scenarios. One of the important parameters for the faint sources is their ...intrinsic luminosity. In the case of low-mass X-ray binaries it has recently been realised that besides a phase of radius expansion, the duration of type I X-ray bursts can be used as a primer for the source luminosity in some cases. Further, we show that a very low equivalent width of hydrogen and helium emission lines in the optical spectrum alone is not a tell-tale sign for an ultra-compact system. Finally, we list and discuss some unusual sources that could be X-ray binaries.
We investigate a region of the Galactic plane, between 120 <= l <= 140 and -1 <= b <= +4, and uncover a population of moderately reddened (E(B-V) \sim 1) classical Be stars within and beyond the ...Perseus and Outer Arms. 370 candidate emission line stars (13 <= r <= 16) selected from the INT Photometric H-alpha Survey of the Northern Galactic plane (IPHAS) have been followed up spectroscopically. A subset of these, 67 stars with properties consistent with those of classical Be stars, have been observed at sufficient spectral resolution (Delta_lambda \sim 2 - 4 Angstrom) at blue wavelengths to narrow down their spectral types. We determine these to a precision estimated to be +/- 1 sub-type and then we measure reddenings via SED fitting with reference to appropriate model atmospheres. Corrections for contribution to colour excess from circumstellar discs are made using an established scaling to H-alpha emission equivalent width. Spectroscopic parallaxes are obtained after luminosity class has been constrained via estimates of distances to neighbouring A/F stars with similar reddenings. Overwhelmingly, the stars in the sample are confirmed as luminous classical Be stars at heliocentric distances ranging from 2 kpc up to \sim 12 kpc. However, the errors are presently too large to enable the cumulative distribution function with respect to distance to distinguish between models placing the stars exclusively in spiral arms, or in a smooth exponentially-declining distribution.
Purely photometric models can be used to determine the binary parameters of eclipsing cataclysmic variables with a high degree of precision. However, the photometric method relies on a number of ...assumptions, and to date there have been very few independent checks of this method in the literature. We present time-resolved spectroscopy of the P=90.9 min eclipsing cataclysmic variable OY Carinae obtained with X-shooter on the VLT, in which we detect the donor star from K I lines in the J-band. We measure the radial velocity amplitude of the donor star K2 = 470.0 +/- 2.7 km/s, consistent with predictions based upon the photometric method (470 +/- 7 km/s). Additionally, the spectra obtained in the UVB arm of X-shooter show a series of Fe I and Fe II lines with a phase and velocity consistent with an origin in the accretion disc. This is the first unambiguous detection at optical wavelengths of the `iron curtain' of disc material which has been previously reported to veil the white dwarf in this system. The velocities of these lines do not track the white dwarf, reflecting a distortion of the outer disc that we see also in Doppler images. This is evidence for considerable radial motion in the outer disk, at up to 90 km/s towards and away from the white dwarf.
