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See detailWASP-22 b: A Transiting "Hot Jupiter" Planet in a Hierarchical Triple System
Maxted, P. F. L.; Anderson, D. R.; Gillon, Michaël ULg et al

in Astrophysical Journal (2010), 140(6), 2007-2012

We report the discovery of a transiting planet orbiting the star TYC 6446-326-1. The star, WASP-22, is a moderately bright (V = 12.0) solar-type star (T[SUB]eff[/SUB] = 6000 ± 100 K, [Fe/H] = –0.05 ± 0.08 ... [more ▼]

We report the discovery of a transiting planet orbiting the star TYC 6446-326-1. The star, WASP-22, is a moderately bright (V = 12.0) solar-type star (T[SUB]eff[/SUB] = 6000 ± 100 K, [Fe/H] = –0.05 ± 0.08). The light curve of the star obtained with the WASP-South instrument shows periodic transit-like features with a depth of about 1% and a duration of 0.14 days. The presence of a transit-like feature in the light curve is confirmed using z-band photometry obtained with Faulkes Telescope South. High-resolution spectroscopy obtained with the CORALIE and HARPS spectrographs confirms the presence of a planetary mass companion with an orbital period of 3.533 days in a near-circular orbit. From a combined analysis of the spectroscopic and photometric data assuming that the star is a typical main-sequence star we estimate that the planet has a mass M [SUB]p[/SUB] = 0.56 ± 0.02M [SUB]Jup[/SUB] and a radius R [SUB]p[/SUB] = 1.12 ± 0.04R [SUB]Jup[/SUB]. In addition, there is a linear trend of 40 m s[SUP]–1[/SUP] yr[SUP]–1[/SUP] in the radial velocities measured over 16 months, from which we infer the presence of a third body with a long-period orbit in this system. The companion may be a low mass M-dwarf, a white dwarf, or a second planet. [less ▲]

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See detailOGLE-2009-BLG-092/MOA-2009-BLG-137: A Dramatic Repeating Event with the Second Perturbation Predicted by Real-time Analysis
Ryu, Y*-H; Han, C.; Hwang, K*-H et al

in Astrophysical Journal (2010), 723(1), 81-88

We report the result of the analysis of a dramatic repeating gravitational microlensing event OGLE-2009-BLG-092/MOA-2009-BLG-137, for which the light curve is characterized by two distinct peaks with ... [more ▼]

We report the result of the analysis of a dramatic repeating gravitational microlensing event OGLE-2009-BLG-092/MOA-2009-BLG-137, for which the light curve is characterized by two distinct peaks with perturbations near both peaks. We find that the event is produced by the passage of the source trajectory over the central perturbation regions associated with the individual components of a wide-separation binary. The event is special in the sense that the second perturbation, occurring ~100 days after the first, was predicted by the real-time analysis conducted after the first peak, demonstrating that real-time modeling can be routinely done for binary and planetary events. With the data obtained from follow-up observations covering the second peak, we are able to uniquely determine the physical parameters of the lens system. We find that the event occurred on a bulge clump giant and it was produced by a binary lens composed of a K- and M-type main-sequence stars. The estimated masses of the binary components are M [SUB]1[/SUB] = 0.69 ± 0.11 M [SUB]sun[/SUB] and M [SUB]2[/SUB] = 0.36 ± 0.06 M [SUB]sun[/SUB], respectively, and they are separated in projection by r [SUB]bottom[/SUB] = 10.9 ± 1.3 AU. The measured distance to the lens is D [SUB]L[/SUB] = 5.6 ± 0.7 kpc. We also detect the orbital motion of the lens system. [less ▲]

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See detailERRATUM: "Physical Properties of the 0.94 Day Period Transiting Planetary System WASP-18" (2009, ApJ, 707, 167)
Southworth, John; Hinse, T. C.; Dominik, M. et al

in Astrophysical Journal (2010), 723(2), 1829

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See detailHD 259440: The Proposed Optical Counterpart of the γ-ray Binary HESS J0632+057
Aragona, C.; McSwain, M. V.; De Becker, Michaël ULg

in Astrophysical Journal (2010), 724

HD 259440 is a B0pe star that was proposed as the optical counterpart to the γ-ray source HESS J0632+057. Here, we present optical spectra of HD 259440 acquired to investigate the stellar parameters, the ... [more ▼]

HD 259440 is a B0pe star that was proposed as the optical counterpart to the γ-ray source HESS J0632+057. Here, we present optical spectra of HD 259440 acquired to investigate the stellar parameters, the properties of the Be star disk, and evidence of binarity in this system. Emission from the Hα line shows evidence of a spiral density wave in the nearly edge-on disk. We find a best-fit stellar effective temperature of 27,500-30,000 K and a log surface gravity of 3.75-4.0, although our fits are somewhat ambiguous due to scattered light from the circumstellar disk. We derive a mass of 13.2-19.0 M sun and a radius of 6.0-9.6 R sun. By fitting the spectral energy distribution, we find a distance between 1.1 and 1.7 kpc. We do not detect any significant radial velocity shifts in our data, ruling out orbital periods shorter than one month. If HD 259440 is a binary, it is likely a long-period (>100 d) system. [less ▲]

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See detailWASP-24 b: A New Transiting Close-in Hot Jupiter Orbiting a Late F-star
Street, R. A.; Simpson, E.; Barros, S. C. C. et al

in Astrophysical Journal (2010), 720

We report the discovery of a new transiting close-in giant planet, WASP-24 b, in a 2.341 day orbit, 0.037 AU from its F8-9 type host star. By matching the star's spectrum with theoretical models, we infer ... [more ▼]

We report the discovery of a new transiting close-in giant planet, WASP-24 b, in a 2.341 day orbit, 0.037 AU from its F8-9 type host star. By matching the star's spectrum with theoretical models, we infer an effective temperature T [SUB]eff[/SUB] = 6075 ± 100 K and a surface gravity of log g = 4.15 ± 0.10. A comparison of these parameters with theoretical isochrones and evolutionary mass tracks places only weak constraints on the age of the host star, which we estimate to be 3.8[SUP]+1.3[/SUP] [SUB]-1.2[/SUB] Gyr. The planetary nature of the companion was confirmed by radial velocity measurements and additional photometric observations. These data were fit simultaneously in order to determine the most probable parameter set for the system, from which we infer a planetary mass of 1.071[SUP]+0.036[/SUP] [SUB]-0.038[/SUB] M [SUB]Jup[/SUB] and radius 1.3[SUP]+0.039[/SUP] [SUB]-0.037[/SUB] R [SUB]Jup[/SUB]. [less ▲]

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See detailFrequency of Solar-like Systems and of Ice and Gas Giants Beyond the Snow Line from High-magnification Microlensing Events in 2005-2008
Gould, A.; Dong, Subo; Gaudi, B. S. et al

in Astrophysical Journal (2010), 720

We present the first measurement of the planet frequency beyond the "snow line," for the planet-to-star mass-ratio interval –4.5 < log q < –2, corresponding to the range of ice giants to gas giants. We ... [more ▼]

We present the first measurement of the planet frequency beyond the "snow line," for the planet-to-star mass-ratio interval –4.5 < log q < –2, corresponding to the range of ice giants to gas giants. We find \endgraf\vbox{\begin{center}$\displaystyle{d^2 N{_{\rm pl}}\over d\log q\, d\log s} = (0.36\pm 0.15)\;{\rm dex}^{-2}$\end{center}}\noindentat the mean mass ratio q = 5 × 10 –4 with no discernible deviation from a flat (Öpik's law) distribution in log-projected separation s. The determination is based on a sample of six planets detected from intensive follow-up observations of high-magnification ( A>200) microlensing events during 2005-2008. The sampled host stars have a typical mass M host ~ 0.5 M sun [less ▲]

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See detailFirst Orbital Solution for the Non-thermal Emitter Cyg OB2 No. 9
Nazé, Yaël ULg; Damerdji, Yassine ULg; Rauw, Grégor ULg et al

in Astrophysical Journal (2010), 719

After the first detection of its binary nature, the spectroscopic monitoring of the non-thermal radio emitter Cyg OB2 No. 9 (P = 2.4 yr) has continued, doubling the number of available spectra of the star ... [more ▼]

After the first detection of its binary nature, the spectroscopic monitoring of the non-thermal radio emitter Cyg OB2 No. 9 (P = 2.4 yr) has continued, doubling the number of available spectra of the star. Since the discovery paper of 2008, a second periastron passage has occurred in 2009 February. Using a variety of techniques, the radial velocities could be estimated and a first, preliminary orbital solution was derived from the He I 5876 line. The mass ratio appears close to unity and the eccentricity is large, i.e., 0.7-0.75. X-ray data from 2004 and 2007 are also analyzed in quest of peculiarities linked to binarity. The observations reveal neither large overluminosity nor strong hardness, but it must be noted that the high-energy data were taken after the periastron passage, at a time where colliding wind emission may be low. Some unusual X-ray variability is however detected, with a 10% flux decrease between 2004 and 2007. To clarify their origin and find a more obvious signature of the wind-wind collision, additional data, taken at periastron and close to it, are needed. Based on observations collected at the Haute-Provence Observatory and with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA). [less ▲]

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See detailCombining Coronagraphy with Interferometry as a Tool for Measuring Stellar Diameters
Riaud, P.; Hanot, Charles ULg

in Astrophysical Journal (2010)

The classical approach for determining stellar angular diameters is to use interferometry and to measure fringe visibilities. Indeed, in the case of a source having a diameter larger than typically λ/6B ... [more ▼]

The classical approach for determining stellar angular diameters is to use interferometry and to measure fringe visibilities. Indeed, in the case of a source having a diameter larger than typically λ/6B, B being the interferometer's baseline and λ the wavelength of observation, the fringe contrast decreases. Similarly, it is possible to perform angular diameter determinations by measuring the stellar leakage from a coronagraphic device or a nulling interferometer. However, all coronagraphic devices (including those using nulling interferometry) are very sensitive to pointing errors and to the size of the source, two factors with significant impact on the rejection efficiency. In this work, we present an innovative idea for measuring stellar diameter variations, combining coronagraphy together with interferometry. We demonstrate that, using coronagraphic nulling statistics, it is possible to measure such variations for angular diameters down to ≈λ/40B with 1σ error-bars as low as ≈λ/1500B. For that purpose, we use a coronagraphic implementation on a two-aperture interferometer, a configuration that significantly increases the precision of stellar diameter measurements. Such a design offers large possibilities regarding the stellar diameter measurement of Cepheids or Mira stars, at a 60-80 μas level. We report on a simulation of a measurement applied to a typical Cepheid case, using the VLTI-UT interferometer on Paranal. [less ▲]

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See detailSolar-like Oscillations in Low-luminosity Red Giants: First Results from Kepler
Bedding, T. R.; Huber, D.; Stello, D. et al

in Astrophysical Journal (2010), 713

We have measured solar-like oscillations in red giants using time-series photometry from the first 34 days of science operations of the Kepler Mission. The light curves, obtained with 30 minute sampling ... [more ▼]

We have measured solar-like oscillations in red giants using time-series photometry from the first 34 days of science operations of the Kepler Mission. The light curves, obtained with 30 minute sampling, reveal clear oscillations in a large sample of G and K giants, extending in luminosity from the red clump down to the bottom of the giant branch. We confirm a strong correlation between the large separation of the oscillations (Πν) and the frequency of maximum power (ν[SUB]max[/SUB]). We focus on a sample of 50 low-luminosity stars (ν[SUB]max[/SUB] > 100 μHz, L <~ 30 L [SUB]sun[/SUB]) having high signal-to-noise ratios and showing the unambiguous signature of solar-like oscillations. These are H-shell-burning stars, whose oscillations should be valuable for testing models of stellar evolution and for constraining the star formation rate in the local disk. We use a new technique to compare stars on a single échelle diagram by scaling their frequencies and find well-defined ridges corresponding to radial and non-radial oscillations, including clear evidence for modes with angular degree l = 3. Measuring the small separation between l = 0 and l = 2 allows us to plot the so-called C-D diagram of δν[SUB]02[/SUB] versus Πν. The small separation δν[SUB]01[/SUB] of l = 1 from the midpoint of adjacent l = 0 modes is negative, contrary to the Sun and solar-type stars. The ridge for l = 1 is notably broadened, which we attribute to mixed modes, confirming theoretical predictions for low-luminosity giants. Overall, the results demonstrate the tremendous potential of Kepler data for asteroseismology of red giants. [less ▲]

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See detailHybrid gamma Doradus-delta Scuti Pulsators: New Insights into the Physics of the Oscillations from Kepler Observations
Grigahcène, Ahmed; Antoci, V.; Balona, L. et al

in Astrophysical Journal (2010), 713

Observations of the pulsations of stars can be used to infer their interior structure and test theoretical models. The main-sequence γ Doradus (Dor) and δ Scuti (Sct) stars with masses 1.2-2.5 M [SUB ... [more ▼]

Observations of the pulsations of stars can be used to infer their interior structure and test theoretical models. The main-sequence γ Doradus (Dor) and δ Scuti (Sct) stars with masses 1.2-2.5 M [SUB]sun[/SUB] are particularly useful for these studies. The γ Dor stars pulsate in high-order g-modes with periods of order 1 day, driven by convective blocking at the base of their envelope convection zone. The δ Sct stars pulsate in low-order g- and p-modes with periods of order 2 hr, driven by the κ mechanism operating in the He II ionization zone. Theory predicts an overlap region in the Hertzsprung-Russell diagram between instability regions, where "hybrid" stars pulsating in both types of modes should exist. The two types of modes with properties governed by different portions of the stellar interior provide complementary model constraints. Among the known γ Dor and δ Sct stars, only four have been confirmed as hybrids. Now, analysis of combined Quarter 0 and Quarter 1 Kepler data for hundreds of variable stars shows that the frequency spectra are so rich that there are practically no pure δ Sct or γ Dor pulsators, i.e., essentially all of the stars show frequencies in both the δ Sct and the γ Dor frequency range. A new observational classification scheme is proposed that takes into account the amplitude as well as the frequency and is applied to categorize 234 stars as δ Sct, γ Dor, δ Sct/γ Dor or γ Dor/δ Sct hybrids. [less ▲]

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See detailA New Investigation of the Binary HD 48099
Mahy, Laurent ULg; Rauw, Grégor ULg; Martins, F. et al

in Astrophysical Journal (2010), 708

With an orbital period of about 3.078 days, the double-lined spectroscopic binary HD 48099 is, until now, the only short-period O+O system known in the Mon OB2 association. Even though an orbital solution ... [more ▼]

With an orbital period of about 3.078 days, the double-lined spectroscopic binary HD 48099 is, until now, the only short-period O+O system known in the Mon OB2 association. Even though an orbital solution has already been derived for this system, few information are available about the individual stars. We present, in this paper, the results of a long-term spectroscopic campaign. We derive a new orbital solution and apply a disentangling method to recover the mean spectrum of each star. To improve our knowledge concerning both components, we determine their spectral classifications and their projected rotational velocities. We also constrain the main stellar parameters of both stars by using the CMFGEN atmosphere code and provide the wind properties for the primary star through the study of International Ultraviolet Explorer spectra. This investigation reveals that HD 48099 is an O5.5 V ((f)) + O9 V binary with M [SUB]1[/SUB]sin[SUP]3[/SUP] i = 0.70 M [SUB]sun[/SUB] and M [SUB]2[/SUB]sin[SUP]3[/SUP] i = 0.39 M [SUB]sun[/SUB], implying a rather low orbital inclination. This result, combined with both a large effective temperature and log g, suggests that the primary star (vsin i sime 91 km s[SUP]â 1[/SUP]) is actually a fast rotator with a strongly clumped wind and a nitrogen abundance of about 8 times the solar value. [less ▲]

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See detailWASP-19b: The Shortest Period Transiting Exoplanet Yet Discovered
Hebb, L.; Collier-Cameron, A.; Triaud, A H M J et al

in Astrophysical Journal (2010), 708

We report on the discovery of a new extremely short period transiting extrasolar planet, WASP-19b. The planet has mass M [SUB]pl[/SUB] = 1.15 ± 0.08 M[SUB]J[/SUB] , radius R [SUB]pl[/SUB] = 1.31 ± 0.06 ... [more ▼]

We report on the discovery of a new extremely short period transiting extrasolar planet, WASP-19b. The planet has mass M [SUB]pl[/SUB] = 1.15 ± 0.08 M[SUB]J[/SUB] , radius R [SUB]pl[/SUB] = 1.31 ± 0.06 R[SUB]J[/SUB] , and orbital period P = 0.7888399 ± 0.0000008 days. Through spectroscopic analysis, we determine the host star to be a slightly super-solar metallicity ([M/H] = 0.1 ± 0.1 dex) G-dwarf with T [SUB]eff[/SUB] = 5500 ± 100 K. In addition, we detect periodic, sinusoidal flux variations in the light curve which are used to derive a rotation period for the star of P [SUB]rot[/SUB] = 10.5 ± 0.2 days. The relatively short stellar rotation period suggests that either WASP-19 is somewhat young (~ 600 Myr old) or tidal interactions between the two bodies have caused the planet to spiral inward over its lifetime resulting in the spin-up of the star. Due to the detection of the rotation period, this system has the potential to place strong constraints on the stellar tidal quality factor, Q'[SUB] s [/SUB], if a more precise age is determined. [less ▲]

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See detailWASP-17b: an ultra-low density planet in a probable retrograde orbit
Anderson, D. R.; Hellier, C.; Gillon, Michaël ULg et al

in Astrophysical Journal (2010), 709(1), 159-167

We report the discovery of the transiting giant planet WASP-17b, the least-dense planet currently known. It is 1.6 Saturn masses but 1.5-2 Jupiter radii, giving a density of 6-14 per cent that of Jupiter ... [more ▼]

We report the discovery of the transiting giant planet WASP-17b, the least-dense planet currently known. It is 1.6 Saturn masses but 1.5-2 Jupiter radii, giving a density of 6-14 per cent that of Jupiter. WASP-17b is in a 3.7-day orbit around a sub-solar metallicity, V = 11.6, F6 star. Preliminary detection of the Rossiter-McLaughlin effect suggests that WASP-17b is in a retrograde orbit (lambda ~ -150 deg), indicative of a violent history involving planet-planet or planet-star scattering. WASP-17b's bloated radius could be due to tidal heating resulting from recent or ongoing tidal circularisation of an eccentric orbit, such as the highly eccentric orbits that typically result from scattering interactions. It will thus be important to determine more precisely the current orbital eccentricity by further high-precision radial velocity measurements or by timing the secondary eclipse, both to reduce the uncertainty on the planet's radius and to test tidal-heating models. Owing to its low surface gravity, WASP-17b's atmosphere has the largest scale height of any known planet, making it a good target for transmission spectroscopy. [less ▲]

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See detailFrequency of Solar-Like Systems and Planet Mass-Ratio Distribution Function Beyond the Snow Line from High-Magnification Microlensing Events
Gould, A.; Dong, S.; Gaudi, B~S et al

in Astrophysical Journal (2010), 720

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See detailAtomic data and spectral model for Fe III
Bautista, M A; Ballance, C; Quinet, Pascal ULg

in Astrophysical Journal (2010), 718

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See detailPhysical Properties of the 0.94-Day Period Transiting Planetary System WASP-18
Southworth, John; Hinse, T. C.; Dominik, M. et al

in Astrophysical Journal (2009), 707

We present high-precision photometry of five consecutive transits of WASP-18, an extrasolar planetary system with one of the shortest orbital periods known. Through the use of telescope defocusing we ... [more ▼]

We present high-precision photometry of five consecutive transits of WASP-18, an extrasolar planetary system with one of the shortest orbital periods known. Through the use of telescope defocusing we achieve a photometric precision of 0.47-0.83 mmag per observation over complete transit events. The data are analyzed using the JKTEBOP code and three different sets of stellar evolutionary models. We find the mass and radius of the planet to be M [SUB]b[/SUB] = 10.43 ± 0.30 ± 0.24 M [SUB]Jup[/SUB] and R [SUB]b[/SUB] = 1.165 ± 0.055 ± 0.014 R [SUB]Jup[/SUB] (statistical and systematic errors), respectively. The systematic errors in the orbital separation and the stellar and planetary masses, arising from the use of theoretical predictions, are of a similar size to the statistical errors and set a limit on our understanding of the WASP-18 system. We point out that seven of the nine known massive transiting planets (M [SUB]b[/SUB] > 3 M [SUB]Jup[/SUB]) have eccentric orbits, whereas significant orbital eccentricity has been detected for only four of the 46 less-massive planets. This may indicate that there are two different populations of transiting planets, but could also be explained by observational biases. Further radial velocity observations of low-mass planets will make it possible to choose between these two scenarios. Based on data collected by MiNDSTEp with the Danish 1.54  m telescope at the ESO La Silla Observatory. [less ▲]

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See detailSpectroscopic Study of the Variability of Three Northern Of+ Supergiants
De Becker, Michaël ULg; Rauw, Grégor ULg; Linder, N.

in Astrophysical Journal (2009), 704

The transition from early Of stars to WN-type objects is poorly understood. O-type supergiants with emission lines (OIf+) are considered to be intermediate between these two classes. The scope of this ... [more ▼]

The transition from early Of stars to WN-type objects is poorly understood. O-type supergiants with emission lines (OIf+) are considered to be intermediate between these two classes. The scope of this paper is to investigate the spectral variability of three Of+ supergiants. We constituted spectral time series of unprecedented quality for our targets (~200 spectra in total), essentially in the blue domain, covering timescales from a few hours up to a few years. Temporal Variance Spectrum and Fourier analyses were performed in order to characterize their spectral variability. We report on a correlated significant line profile variability in the prominent He II λ4686 and Hβ lines most likely related to the strong stellar winds. The variability pattern is similar for the three stars investigated (HD 14947, HD 15570, and HD 16691), and the main differences are more quantitative than qualitative. However, the reported timescales are somewhat different, and the most striking variability pattern is reported for HD 16691. We did not find any clear evidence for binarity, and we focus mainly on an interpretation based on a single-star scenario. We show that the behavior of the three stars investigated in this study present strong similarities, pointing to a putative common scenario, even though a few differences should be noted. Our preferred interpretation scheme is that of Large-Scale Corotating Structures modulating the profile of the lines that are produced in the strong stellar wind. [less ▲]

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See detailAn Interferometric Study of the Fomalhaut Inner Debris Disk. I. Near-Infrared Detection of Hot Dust with VLTI/VINCI
Absil, Olivier ULg; Mennesson, Bertrand; Le Bouquin, Jean-Baptiste et al

in Astrophysical Journal (2009), 704

The innermost parts of dusty debris disks around main-sequence stars are currently poorly known due to the high contrast and small angular separation with their parent stars. Using near-infrared ... [more ▼]

The innermost parts of dusty debris disks around main-sequence stars are currently poorly known due to the high contrast and small angular separation with their parent stars. Using near-infrared interferometry, we aim to detect the signature of hot dust around the nearby A4 V star Fomalhaut, which has already been suggested to harbor a warm dust population in addition to a cold dust ring located at about 140 AU. Archival data obtained with the VINCI instrument at the VLTI are used to study the fringe visibility of the Fomalhaut system at projected baseline lengths ranging from 4 m to 140 m in the K band. A significant visibility deficit is observed at short baselines with respect to the expected visibility of the sole stellar photosphere. This is interpreted as the signature of resolved circumstellar emission, producing a relative flux of 0.88% ± 0.12% with respect to the stellar photosphere. While our interferometric data cannot directly constrain the morphology of the excess emission source, complementary data from the literature allow us to discard an off-axis point-like object as the source of circumstellar emission. We argue that the thermal emission from hot dusty grains located within 6 AU from Fomalhaut is the most plausible explanation for the detected excess. Our study also provides a revised limb-darkened diameter for Fomalhaut (theta_LD = 2.223 ± 0.022 mas), taking into account the effect of the resolved circumstellar emission. Based on observations made with ESO Telescopes at the Paranal Observatory (public VINCI commissioning data). [less ▲]

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See detailWASP-16b: A New Jupiter-Like Planet Transiting a Southern Solar Analog
Lister, T. A.; Anderson, D. R.; Gillon, Michaël ULg et al

in Astrophysical Journal (2009), 703

We report the discovery from WASP-South of a new Jupiter-like extrasolar planet, WASP-16b, which transits its solar analog host star every 3.12 days. Analysis of the transit photometry and radial velocity ... [more ▼]

We report the discovery from WASP-South of a new Jupiter-like extrasolar planet, WASP-16b, which transits its solar analog host star every 3.12 days. Analysis of the transit photometry and radial velocity spectroscopic data leads to a planet with R [SUB]p[/SUB] = 1.008 ± 0.071 R [SUB]Jup[/SUB] and M [SUB]p[/SUB] = 0.855 ± 0.059 M [SUB]Jup[/SUB], orbiting a host star with R [SUB]*[/SUB] = 0.946 ± 0.054 R [SUB]sun[/SUB] and M [SUB]*[/SUB] = 1.022 ± 0.101 M [SUB]sun[/SUB]. Comparison of the high resolution stellar spectrum with synthetic spectra and stellar evolution models indicates the host star is a near-solar metallicity ([Fe/H] =0.01 ± 0.10) solar analog (T [SUB]eff[/SUB] = 5700 ± 150 K and log g = 4.5 ± 0.2) of intermediate age (tau = 2.3[SUP]+5.8[/SUP] [SUB]--2.2[/SUB] Gyr). [less ▲]

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See detailThe QSO HE0450-2958: Scantily dressed or heavily robed? A normal quasar as part of an unusual ULIRG
Jahnke, Knud; Elbaz, David; Pantin, Eric et al

in Astrophysical Journal (2009), 700(2), 1820-1830

(Abridged) The luminous z=0.286 quasar HE0450-2958 is interacting with a companion galaxy at 6.5 kpc distance and the whole system is a ULIRG. A so far undetected host galaxy triggered the hypothesis of a ... [more ▼]

(Abridged) The luminous z=0.286 quasar HE0450-2958 is interacting with a companion galaxy at 6.5 kpc distance and the whole system is a ULIRG. A so far undetected host galaxy triggered the hypothesis of a mostly "naked" black hole (BH) ejected from the companion by three-body interaction. We present new HST/NICMOS 1.6micron imaging data at 0.1" resolution and VLT/VISIR 11.3micron images at 0.35" resolution that for the first time resolve the system in the near- and mid-infrared. We combine these with existing optical HST and CO maps. (i) At 1.6micron we find an extension N-E of the quasar nucleus that is likely a part of the host galaxy, though not its main body. If true, this places HE0450-2958 directly onto the M_BH-M_bulge-relation for nearby galaxies. (ii) HE0450-2958 is consistent with lying at the high-luminosity end of Narrow-Line Seyfert 1 Galaxies, and more exotic explanations like a "naked quasar" are unlikely. (iii) All 11.3micron radiation in the system is emitted by the quasar nucleus, which is radiating at super-Eddington rate, L/L_Edd=6.2+3.8-1.8, or 12 M_sun/yr. (iv) The companion galaxy is covered in optically thick dust and is not a collisional ring galaxy. It emits in the far infrared at ULIRG strength, powered by Arp220-like star formation (strong starburst-like). An M82-like SED is ruled out. (v) With its black hole accretion rate HE0450-2958 produces not enough new stars to maintain its position on the M_BH-M_bulge-relation, and star formation and black hole accretion are spatially disjoint; the bulge has to grow by redistribution of preexisting stars. (vi) Systems similar to HE0450-2958 with spatially disjoint ULIRG-strength star formation and quasar activity are rare. At z<0.43 we only find <4% (3/77) candidates for a similar configuration. [less ▲]

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