AN IMPROVED DYNAMICAL MODEL FOR THE MICROQUASAR XTE J1550–564

(shortened) Spectroscopic observations of the soft X-ray transient 4U 1543-47 reveal a radial velocity curve with a period of P=1.123 +/- 0.008 days and a semi-amplitude of K_2 = 124 +/- 4 km/sec. The mass function is f(M) = 0.22 +/- 0.02 solar masses. We derive a distance of d = 9.1 +/-1.1 kpc if the secondary is on the main sequence. The V and I light curves exhibit two waves per orbital cycle with amplitudes of about 0.08 mag. We modeled the light curves as ellipsoidal variations in the secondary star and derive extreme inclination limits of 20 <= i <= 40 deg and formal 3 sigma limits of 24 <= i <= 36 deg for a mass ratio Q = M_1/M_2 > 1. However, there are systematic effects in the data that the model does not account for, so the above constraints should be treated with caution. We argue that the secondary star is still on the main sequence and if the secondary star has a mass near the main sequence values for early A-stars (2.3 <= M_2 <= 2.6 solar masses), then the best fits for the 3 sigma inclination range (24 <= i <= 36 deg) and the 3 sigma mass function range (0.16 <= f(M) <= 0.28 solar masses) imply a primary mass in the range 2.7 <= M_1 <= 7.5 solar masses. Thus the mass of the compact object in 4U 1543-47 is likely to be in excess of approximately 3 solar masses and we conclude 4U 1543-47 most likely contains a black hole.

We present a dynamical model of the high mass X-ray binary LMC X-1 based on high-resolution optical spectroscopy and extensive optical and near-infrared photometry. From our new optical data we find an orbital period of P=3.90917 +/- 0.00005 days. We present a refined analysis of the All Sky Monitor data from RXTE and find an X-ray period of P=3.9094 +/- 0.0008 days, which is consistent with the optical period. A simple model of Thomson scattering in the stellar wind can account for the modulation seen in the X-ray light curves. The V-K color of the star (1.17 +/- 0.05) implies A_V = 2.28 +/- 0.06, which is much larger than previously assumed. For the secondary star, we measure a radius of R_2 = 17.0 +/- 0.8 solar radii and a projected rotational velocity of V_rot*sin(i) = 129.9 +/- 2.2 km/s. Using these measured properties to constrain the dynamical model, we find an inclination of i = 36.38 +/- 1.92 deg, a secondary star mass of M_2 = 31.79 +/- 3.48 solar masses, and a black hole mass of 10.91 +/- 1.41 solar masses. The present location of the secondary star in a temperature-luminosity diagram is consistent with that of a star with an initial mass of 35 solar masses that is 5 Myr past the zero-age main sequence. The star nearly fills its Roche lobe (~90% or more), and owing to the rapid change in radius with time in its present evolutionary state, it will encounter its Roche lobe and begin rapid and possibly unstable mass transfer on a timescale of a few hundred thousand years.

view Abstract Citations (36) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Spectacular Emission-Line Reflection Effect of BE Ursae Majoris Ferguson, Donald H. ; James, Thomas A. Abstract BE UMa is a noninteracting eclipsing binary consisting of a approximately 100,00 K sdO primary star and a G2 V-K2 V secondary star. The powerful extreme ultraviolet (EUV) flux from the primary star incident on the facing secondary produces a stunning reflection effect that modulates with orbital phase. Preparatory to extensive modeling of the reflection effect, we identify and phase-normalize in self-consistent fashion the emission-line features from a variety of spectra with broad wavelength coverage. We present an analytic model of the reflection effect based on the graybody approximation that predicts a slight but potentially observable asymmetry in the visible light curve. We develop a digital model using the CLOUDY code in the upper regions of the reflection effect atmosphere, where hydrogen is photoionized, and approximate the higher density heated photosphere as a blackbody. The model accounts for angle of incidence of the EUV radiation across the facing secondary by dividing the hemisphere into concentric annuli and then co-adding results. A sensitive study involving a wide variety of physical input values was performed, leading to a set of precise predictions describing the BE UMa system that differ substantially from existing estimates. The primary star mass and luminosity are 0.90 +/- 0.04 solar mass and (2.5 +/- 0.8) x 1036 ergs/s, respectively. The secondary star mass, intrinsic temperature, and radius are 0.83 +/- 0.10 solar mass, 5000 +/- 500 K, and 0.96 +/- 0.22 solar radius, yielding a spectral type of G2 V-K2 V, although some enlargement of the secondary radius over main-sequence values cannot be ruled out. The helium abundance of the secondary star is log (He/H) = -1.0 +/- 0.25 by number. The secondary star metal abundance is from one-third solar to near-solar. The primary cause of the strong emission feature at 4650 A is recombinational O II with a nonnegligible C III component. The relative mix of metals appears solar-like, although only the relative abundance ratio of C/O approximately 0.6 could be quantitatively estimated. The binary star separation is 8.6 +/- 0.2 solar radius. Based on both estimates derived from the primary star and the reflection effect, BE UMa lies at a distance of 8.6 +/- 2.0 +/- 0.4 kpc, nearly perpendicular to the Galactic plane. Our model makes specific predictions regarding the luminosity of the primary star that have recently been confirmed independently through direct analysis of the primary star spectrum by Liebert et al. (1994). The methods we have developed are applicable to other EUV-produced reflection effects, such as those sometimes seen in planetary nebulae. Publication: The Astrophysical Journal Supplement Series Pub Date: October 1994 DOI: 10.1086/192088 Bibcode: 1994ApJS...94..723F Keywords: Eclipsing Binary Stars; Spectral Reflectance; Stellar Luminosity; Stellar Models; Abundance; Digital Simulation; Extreme Ultraviolet Radiation; Photoionization; Stellar Mass; Astrophysics full text sources ADS | data products SIMBAD (1)

VLBI spectral absorption in AGN

We present the results of a pilot survey for neutral hydrogen (HI) 21 cm absorption in the Arecibo Legacy Fast Arecibo L-Band Feed Array (ALFALFA) Survey. This project is a wide-area "blind" search for HI absorption in the local universe, spanning -650 km/s < cz < 17,500 km/s and covering 517.0 square degrees (7% of the full ALFALFA survey). The survey is sensitive to HI absorption lines stronger than 7.7 mJy (8983 radio sources) and is 90% complete for lines stronger than 11.0 mJy (7296 sources). The total redshift interval sensitive to all damped Lyman alpha (DLA) systems (N_HI >= 2x10^20 cm^-2) is Delta z = 7.0 (129 objects, assuming T_s = 100 K and covering fraction unity); for super-DLAs (N_HI >= 2x10^21 cm^-2) it is Delta z= 128.2 (2353 objects). We re-detect the intrinsic HI absorption line in UGC 6081 but detect no intervening absorption line systems. We compute a 95% confidence upper limit on the column density frequency distribution function f(N_HI,X) spanning four orders of magnitude in column density, 10^19 (T_s/100 K)(1/f) cm^-2 < N_HI < 10^23 (T_s/100 K)(1/f) cm^-2, that is consistent with previous redshifted optical damped Ly alpha surveys and the aggregate HI 21 cm emission in the local universe. The detection rate is in agreement with extant observations. This pilot survey suggests that an absorption line search of the complete ALFALFA survey --- or any higher redshift, larger bandwidth, or more sensitive survey, such as those planned for Square Kilometer Array pathfinders or a low frequency lunar array --- will either make numerous detections or will set a strong statistical lower limit on the typical spin temperature of neutral hydrogen gas.

Time-resolved spectroscopic observations of the precataclysmic binary RR Cae in the red make it possible to measure the radial velocity (RV) curve of this late-type secondary star and its Hα emission component. The latter is not caused by the illumination of the secondary star by the white dwarf, as in other precataclysmic binaries, but is intrinsic to the late-type star. The phasing of the RV curve allows for an improved measurement of the orbital period. Although still lacking RV measurements of the white dwarf primary, the present observations, together with a reanalysis of previous photometric measurements with the Wilson-Devinney light curve synthesis routine, permit improved determinations of many system parameters. Component masses are found to be 0.467 M⊙ and 0.095 M⊙ for the primary and the secondary stars, respectively. The radius of the secondary star, at 0.189 R⊙, is considerably larger than expected for such a low-mass star, possibly as a consequence of a previous common envelope phase. An orbital eccentricity, although strongly suggested by the shape of the light curve, is not supported by the RV curve. RR Cae is an eclipsing binary with two spectral line systems, which makes it possible to measure the component masses directly. This is of particular importance for the red dwarf secondary, which is of a later spectral type and probably of lower mass than any other known star for which such measurements are possible.

IntroductionThe detection and confirmation of long-period transiting planets present significant challenges due to the infrequency of their transits. Such planets are crucial for enhancing our understanding of exoplanet formation and evolutionary dynamics. TOI-4409 b, initially identified by TESS, represents a prototypical case for studying these phenomena.This study aims to confirm and further characterise TOI-4409 b, a long-period planetary candidate. Utilising a combination of photometric and radial velocity (RV) data, the research focuses on verifying the planet's existence and describing its orbital and physical properties.MethodThe comprehensive analysis incorporated photometric data from TESS, ASTEP, CHAT, and OMES lightcurves, along with RV measurements from HARPS, FEROS, and PFS. In total, the study analysed eight lightcurves from TESS, four from ASTEP, one from CHAT, and three from OMES. RV data spanned from 2018 to 2023, as shown in Figure 1, offering a longitudinal perspective essential for detecting and confirming the planetary signals of TOI-4409 b.The TESS spacecraft provided the initial detection of TOI-4409 b through its wide-field, high-precision photometry, which is particularly adept at identifying transiting exoplanets. Subsequent observations by the ASTEP telescope, strategically located in Antarctica, leveraged the prolonged periods of darkness and stable atmospheric conditions to observe additional transits. This was critical for capturing the infrequent transits of TOI-4409 b. Lightcurves from CHAT and OMES telescopes further supplemented these observations, enhancing the data's robustness through additional transit captures and minimising gaps in the observational data.Radial velocity data were obtained using three high-precision spectrometers: HARPS, FEROS, and PFS. These instruments are renowned for their sensitivity in detecting the subtle stellar wobbles induced by orbiting planets, which are crucial for confirming the planetary nature of transit signals. The combined RV dataset enabled a comprehensive analysis of the star's motion, aiding in the verification of TOI-4409 b and suggesting the presence of additional planetary bodies through observed anomalies in the RV signals.ResultsThe integrated analysis confirmed TOI-4409 b as an exoplanet with a planetary radius of 7.28&amp;#177;0.20 Earth radii, orbiting a low-mass main sequence star with an effective temperature of approximately 4945&amp;#177;10 K and a stellar radius of 0.720&amp;#177;0.018 solar radii. The orbital period of TOI-4409 b was determined to be 92.4&amp;#177;0.8 days. Two of the processed light curves are shown in Figure 2.Consistent transit signals across multiple datasets, combined with observed Transit Timing Variations (TTVs), reinforced the candidate&amp;#8217;s robustness. These TTVs (showcased in Figure 3), in conjunction with the radial velocity data, suggested the gravitational influence of a second planet in a 20-day orbit around the same star.The integration of diverse observational methods and data from multiple instruments was pivotal in confirming the planetary status of TOI-4409 b. This approach not only facilitated a thorough characterisation of the planet but also underscored the potential complexities of its orbital dynamics, hinted at by the TTV and RV analyses.The evidence for a second planet, suggested by anomalies in TTV measurements, points to a potentially rich multi-planetary system, warranting further investigation. This discovery highlights the importance of multi-modal and multi-instrumental data analysis in the field of exoplanet research, where single-method approaches may not suffice due to the complex nature of planetary systems and the limitations of individual observational techniques.ConclusionThe successful confirmation of TOI-4409 b as a long-period exoplanet and the indication of a secondary nearby planet demonstrates the critical role of global cooperation and technological integration in exoplanetary science. The unique capabilities of the Antarctica-based ASTEP telescope, combined with the extensive data provided by TESS, CHAT, OMES, HARPS, FEROS, and PFS, exemplify how diverse observational assets can come together to enhance our understanding of the universe.Continued monitoring and future investigations into the TOI-4409 system are essential. They will not only confirm the characteristics and existence of the second suggested planet but will also provide deeper insights into the dynamics and potential habitability of planets in long-period orbits. This study sets a precedent for future research into similar exoplanetary systems, using refined methods and international collaboration to further our understanding of planetary formation and evolution.&amp;#160;Figure 1: All unique photometric observation midtimes, spanning the years 2018 to 2023. This distribution of dates enabled a robust TTV analysis.&amp;#160;Figure 2: TESS (left) lightcurve and ASTEP (right) model fit result, showcasing the transiting nature and the TTV of the signals analysed. All 16 light curves were fitted using the same method.Figure 3: All the unique transit midtimes of our observations (in BJD - 2458000), alongside their calculated Transit Timing Variations.

The light-curve synthesis approach of Wilson and Devinney (1971) has been used to solve simultaneously light and radial velocity curves of the Algol-type eclipsing binary star U Cephei. Eight new differential corrections solutions have been performed to obtain a consistent set of orbital and astrophysical parameters for the light and velocity curves of this famous system. U Cephei is found to be best modeled using the semidetached (mode 5) system geometry of the Wilson and Devinney program, with a primary rotating at about 5.2 times its synchronous rate, and absolute system parameters are found to be M1 = 4.93 solar masses, M2 = 3.27 solar masses, R1 = 2.77 solar radii and R2 = 5.22 solar radii. 46 refs.

view Abstract Citations (65) References (56) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Wolf-Rayet Binary V444 Cygni under the Spectroscopic Microscope. I. Improved Characteristics of the Components and Their Interaction Seen in He i Marchenko, Sergey V. ; Moffat, Anthony F. J. ; Koenigsberger, Gloria Abstract A large accumulation of high signal-to-noise, moderate-resolution optical spectra has led to an unprecedented analysis of the radial velocities of emission and absorption lines in the close binary system V444 Cyg (WN 5 + O6 III-V). Improved orbital elements and masses are KWR = 332.6 +/- 3.0 km/s, KO = 108.4 +/- 4.7 km/s, a(sin (i)) = 35.8 +/- 0.4 solar radius, e = 0.036 +/- -0.009, MWR(sin (i))3) = 8.8 +/- 0.4 solar mass, MO((sin(i))3) = 26.3 +/- 1.0 solar mass. With i = 78.7 +/- 0.5 deg from previous studies, these yield a = 38.0 +/- 0.5 solar radius, MWR = 9.3 +/- 0.5 solar mass, MO = 27.9 +/- 1.1 solar mass. Other results include (1) the stable presence of short-period pulsations, P approximately equals 0.36 days in the O-C deviations from the W-R orbital curve based on the He II 4686 and 5412 radial velocities; (2) supersynchronous rotation of the O star by a factor approximately 2: ve(sin (i)) = 215 +/- 13 km/s, (3) sensitivity, especially of the He I 4471, 4922, and 5876 lines, to the presence of a wind-wind collision region in the form of a bow shock around the O star. Publication: The Astrophysical Journal Pub Date: February 1994 DOI: 10.1086/173773 Bibcode: 1994ApJ...422..810M Keywords: Absorption Spectra; Eclipsing Binary Stars; Emission Spectra; Light (Visible Radiation); Line Spectra; Orbital Elements; Radial Velocity; Stellar Mass; Wolf-Rayet Stars; Astronomical Spectroscopy; Bow Waves; Helium; O Stars; Shock Waves; Stellar Rotation; Astronomy; STARS: BINARIES: ECLIPSING; STARS: INDIVIDUAL CONSTELLATION NAME: V444 CYGNI; STARS: WOLF-RAYET full text sources ADS | data products SIMBAD (5) Related Materials (1) Part 2: 1997ApJ...485..826M

view Abstract Citations (29) References (39) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS LB 1800: A Bright Eclipsing Cataclysmic Variable and a Transient X-Ray Source Buckley, D. A. H. ; Sullivan, D. J. ; Remillard, R. A. ; Tuohy, I. R. ; Clark, M. Abstract The star LB 1800 has been discovered to be a 13th mag high-excitation cataclysmic variable exhibiting novalike characteristics and partial eclipses in its light curve. It has subsequently been identified as the optical counterpart of the transient hard X-ray source 4U 0608-49 following analysis of HEAO 1 data. Both the radial velocity and photometric variations have a period of 5.56 hr, while the K-velocity of the relatively uncomplicated radial velocity curves is 134 + or - 9 km/s, leading to a mass function of 0.058 + or - 0.003 solar mass. The dynamical and eclipse solutions point to an orbital inclination of 87 deg + or - 3 deg and a mass ratio of 0.46 + or - 0.04 for the empirical secondary mass 0.55 solar mass. The implied white dwarf mass is therefore quite high at about 1.2 solar mass. The disk size, from timings of first and last contact, was estimated to be very close to that of the secondary star. Phase-dependent, double-peak emission lines are sometimes observed. It is argued that the orbital variations in the relative strengths of the red and blue peaks arise from changing hot-spot visibility. Publication: The Astrophysical Journal Pub Date: June 1990 DOI: 10.1086/168794 Bibcode: 1990ApJ...355..617B Keywords: Cataclysmic Variables; Eclipsing Binary Stars; X Ray Sources; Balmer Series; Dwarf Novae; Light Curve; Spectral Line Width; Stellar Luminosity; White Dwarf Stars; Astrophysics; STARS: DWARF NOVAE; STARS: ECLIPSING BINARIES; STARS: INDIVIDUAL ALPHANUMERIC: LB 1800; X-RAYS: BINARIES full text sources ADS | data products SIMBAD (4)

(shortened) Spectroscopic observations of the fast X-ray transient and superluminal jet source SAX J1819.3-2525 (V4641 Sgr) reveal a best fitting period of P_spect=2.81678 +/- 0.00056 days and a semiamplitude of K_2=211.0 +/- 3.1 km/sec. The optical mass function is f(M)=2.74 +/- 0.12 solar masses. We find a photometric period of P_photo=2.81730 +/- 0.00001 days using a light curve measured from photographic plates. The folded light curve resembles an ellipsoidal light curve with two maxima of roughly equal height and two minima of unequal depth per orbital cycle. The secondary star is a late B-type star which has evolved off the main sequence. Using a moderate resolution spectrum (R=7000) we measure T_eff=10500 +/- 200K, log(g)=3.5 +/- 0.1, and V_rot*sin(i)=123 +/- 4 km/sec (1 sigma errors). Assuming synchronous rotation, our measured value of the projected rotational velocity implies a mass ratio of Q=M_1/M_2=1.50 +/- 0.08 (1sigma). The lack of X-ray eclipses implies an upper limit to the inclination of i 60 deg). Using the above mass function, mass ratio, and inclination range, the mass of the compact object is in the range 8.73 < M_1 < 11.70 solar masses and the mass of the secondary star is in the range 5.49 < M_2 < 8.14 solar masses (90% confidence). The mass of the compact object is well above the maximum mass of a stable neutron star and we conclude that V4641 Sgr contains a black hole.

The physical properties of the population II cepheids have been studied using the following material: photoelectric observations of Arp, low dispersion spectra of Joy, high dispersion spectra taken by Sanford and Abt, and numerous moderate dispersion spectra obtained by the author. Radial velocity curves for ten cepheids are shown. It is shown that the velocity curves for all population II cepheids with periods greater than 15 days are probably discontinuous. The difference between the RV tauri star an the star whose velocity and light curves repeat well is shown to be due to a delay in the new outrush of gas during alternate cycles of the RV tauri star. Displacement curves are derived for eight cepheids that probably have discontinuous velocity curves. The photoelectric observations are interpreted to show that the surface temperature M5 No. 42 varies from 7200°K to 4800°K and of W Virginis from 6200°K to below 4800°K. The electron pressure for the two stars varies from 100 dynes/cm2 to 0.1 dynes/cm2 and 10 dynes/cm2 to less than 0.1 dynes/cm2 respectively. The changes in radii obtained applying Steffan's Law to the changes in temperature and luminosity agree reasonably well with integration of the velocity curve. Values of the surface gravity obtained from the colors at maximum radius and from the deceleration of the velocity curve yield masses in the vicinity of one to three solar masses. The use of the period density relation is consistent with masses between 1.2 and 2.0 solar masses. The spectra of the population II cepheids are generally of type A5 to F0 at earliest a F5 to G0 at latest. No correlation of spectral type with period can found. A correlation between spectral type and light curve seems to be present. Consideration of the emission lines and of certain absorption lines that are effected by dilution leads to the conclusion that proper model for W Virginis must contain a shock wave moving out through the atmosphere of the star.

Dynamic models of the Hipp pendulum regulator: PMM vol. 35, n≗1, 1971, pp. 147–162

HI Absorption Lines Detected from the Arecibo Legacy Fast ALFA Survey Data

The large spectral bandwidth and wide field of view of the Australian SKA Pathfinder radio telescope will open up a completely new parameter space for large extragalactic HI surveys. Here we focus on identifying and parametrising HI absorption lines which occur in the line of sight towards strong radio continuum sources. We have developed a method for simultaneously finding and fitting HI absorption lines in radio data by using multi-nested sampling, a Bayesian Monte Carlo algorithm. The method is tested on a simulated ASKAP data cube, and is shown to be reliable at detecting absorption lines in low signal-to-noise data without the need to smooth or alter the data. Estimation of the local Bayesian evidence statistic provides a quantitative criterion for assigning significance to a detection and selecting between competing analytical line-profile models.