Dust rings and filaments around the isolated young star V1331 Cygni

We characterize the small and large scale environment of the young star V1331 Cygni with high resolution HST/WFPC2 and Digitized Sky Survey images. In addition to a previously known outer dust ring (~30'' in diameter), the HST/WFPC2 scattered light image reveals an inner dust ring for the first time. This ring has a maximum radius of 6.5'' and is possibly related to a molecular envelope. Large-scale optical images show that V1331 Cyg is located at the tip of a long dust filament linking it to the dark cloud LDN 981. We discuss the origin of the observed dust morphology and analyze the object's relation to its parent dark cloud LDN 981. Finally, based on recent results from the literature, we investigate the properties of V1331 Cyg and conclude that in its current state the object does not show suffcient evidence to be characterized as an FU Ori object.Comment: 15 pages ApJ preprint style including 3 figures, accepted for publication in ApJ (Feb. 2007

FU Orionis - The MIDI/VLTI Perspective

We present the first mid-infrared interferometric measurements of FU Orionis. We clearly resolve structures that are best explained with an optically thick accretion disk. A simple accretion disk model fits the observed SED and visibilities reasonably well and does not require the presence of any additional structure such as a dusty envelope. The inclination and also the position angle of the disk can be constrained from the multibaseline interferometric observations. Our disk model is in general agreement with most published near-infrared interferometric measurements. From the shape and strength of the 8-13 micrometer spectrum the dust composition of the accretion disk is derived for the first time. We conclude that most dust particles are amorphous and already much larger than those typically observed in the ISM. Although the high accretion rate of the system provides both, high temperatures out to large radii and an effective transport mechanism to distribute crystalline grains, we do not see any evidence for crystalline silicates neither in the total spectrum nor in the correlated flux spectra from the inner disk regions. Possible reasons for this non-detection are mentioned. All results are discussed in context with other high-spatial resolution observations of FU Ori and other FU Ori objects. We also address the question whether FU Ori is in a younger evolutionary stage than a classical TTauri star.Comment: 41 pages (aastex style), 11 figures, 8 tables, accepted by Ap

High-Resolution Spectroscopy of FUors

High-resolution spectroscopy was obtained of the FUors FU Ori and V1057 Cyg between 1995 and 2002 with SOFIN at NOT and with HIRES at Keck I. During those years FU Ori remained about 1 mag. (in B) below its 1938-39 maximum brightness, but V1057 Cyg (B ~ 10.5 at peak in 1970-71) faded from about 13.5 to 14.9 and then recovered slightly. Their photospheric spectra resemble a rotating G0 Ib supergiant, with v_eq sin i = 70 km/s for FU Ori and 55 km/s for V1057 Cyg. As V1057 Cyg faded, P Cyg structure in Halpha and the IR CaII lines strengthened and a complex shortward-displaced shell spectrum increased in strength, disappeared in 1999, and reappeared in 2001. Night-to-night changes in the wind structure of FU Ori show evidence of sporadic infall. The strength of P Cyg absorption varied cyclically with a period of 14.8 days, with phase stability maintained over 3 seasons, and is believed to be the rotation period. The structure of the photospheric lines also varies cyclically, but with a period of 3.54 days. A similar variation may be present in V1057 Cyg. As V1057 Cyg has faded, the emission lines of a pre-existing low-excitation chromosphere have emerged, so we believe the `line doubling' in V1057 Cyg is produced by these central emission cores in the absorption lines, not by orbital motion in an inclined Keplerian disk. No dependence of v_eq sin i on wavelength or excitation potential was detected in either star, again contrary to expectation for a self-luminous accretion disk. Nor are critical lines in the near infrared accounted for by synthetic disk spectra. A rapidly rotating star near the edge of stability (Larson 1980), can better explain these observations. FUor eruptions may not be a property of ordinary TTS, but may be confined to a special subspecies of rapid rotators having powerful quasi-permanent winds.Comment: 41 pages (including 32 figures and 9 tables); ApJ, in press; author affiliation, figs. 3 and 9 correcte

Mc Neil's Nebula in Orion: The Outburst History

We present a sequence of I-band images obtained at the Venezuela 1m Schmidt telescope during the outburst of the nebula recently discovered by J.W. McNeil in the Orion L1630 molecular cloud. We derive photometry spanning the pre-outburst state and the brightening itself, a unique record including 14 epochs and spanning a time scale of ~5 years. We constrain the beginning of the outburst at some time between Oct. 28 and Nov. 15, 2003. The light curve of the object at the vertex of the nebula, the likely exciting source of the outburst, reveals that it has brightened ~5 magnitudes in about 4 months. The time scale for the nebula to develop is consistent with the light travel time, indicating that we are observing light from the central source scattered by the ambient cloud into the line of sight. We also show recent FLWO optical spectroscopy of the exciting source and of the nearby HH 22. The spectrum of the source is highly reddened; in contrast, the spectrum of HH 22 shows a shock spectrum superimposed on a continuum, most likely due to reflected light from the exciting source reaching the HH object through a much less reddened path. The blue portion of this spectrum is consistent with an early B spectral type, similar to the early outburst spectrum of the FU Ori variable V1057 Cyg; we estimate a luminosity of L ~219 Lsun. The eruptive behavior of the McNeil nebula source, its spectroscopic characteristics and luminosity, suggest we may be witnessing an FU Ori event on its way to maximum. Further monitoring of this object will decide whether it qualifies as a member of this rare class of objects.Comment: 13 pages, 4 figures, accepted to ApJ Letter

The photometric evolution of FU Orionis objects: disc instability and wind-envelope interaction

We present the results of a photometric monitoring campaign of three well studied FU Orionis systems (FU Orionis, V1057 Cygni and V1515 Cygni) undertaken at Maidanak Observatory between 1981 and 2003. When combined with photometric data in the literature, this database provides a valuable resource for searching for short timescale variability - both periodic and aperiodic - as well as for studying the secular evolution of these systems. In the case of V1057 Cyg (which is the system exhibiting the largest changes in brightness since it went into outburst) we compare the photometric data with time dependent models. We show that prior to the end of the `plateau' stage in 1996, the evolution of V1057 Cyg in the $V-(B-V)$ colour-magnitude diagram is well represented by disc instability models in which the outburst is triggered by some agent - such as an orbiting planet - in the inner disc. Following the end of the plateau phase in 1996, the dimming and irregular variations are consistent with occultation of the source by a variable dust screen, which has previously been interpreted in terms of dust condensation events in the observed disc wind. Here we instead suggest that this effect results from the interaction between the wind and an infalling dusty envelope, the existence of this envelope having been previously invoked in order to explain the mid infrared emissio of FU Orionis systems. We discuss how this model may explain some of the photometric and spectroscopic characteristics of FU Orionis systems in general.Comment: 14 pages, 12 figures, MNRAS, accepted. Data files with detailed photometry can be found at http://www.ast.cam.ac.uk/~giuseppe/Publications

PTF10nvg: An Outbursting Class I Protostar in the Pelican/North American Nebula

During a synoptic survey of the North American Nebula region, the Palomar Transient Factory (PTF) detected an optical outburst (dubbed PTF10nvg) associated with the previously unstudied flat or rising spectrum infrared source IRAS 20496+4354. The PTF R-band light curve reveals that PTF10nvg brightened by more than 5 mag during the current outburst, rising to a peak magnitude of R~13.5 in 2010 Sep. Follow-up observations indicate PTF10nvg has undergone a similar ~5 mag brightening in the K band, and possesses a rich emission-line spectrum, including numerous lines commonly assumed to trace mass accretion and outflows. Many of these lines are blueshifted by ~175 km/s from the North American Nebula's rest velocity, suggesting that PTF10nvg is driving an outflow. Optical spectra of PTF10nvg show several TiO/VO bandheads fully in emission, indicating the presence of an unusual amount of dense (> 10^10 cm^-3), warm (1500-4000 K) circumstellar material. Near-infrared spectra of PTF10nvg appear quite similar to a spectrum of McNeil's Nebula/V1647 Ori, a young star which has undergone several brightenings in recent decades, and 06297+1021W, a Class I protostar with a similarly rich near--infrared emission line spectrum. While further monitoring is required to fully understand this event, we conclude that the brightening of PTF10nvg is indicative of enhanced accretion and outflow in this Class-I-type protostellar object, similar to the behavior of V1647 Ori in 2004-2005.Comment: Accepted to the Astronomical Journal; 21 pages, 11 figures, 6 tables in emulateapj format; v2 fixes typo in abstract; v3 updates status to accepted, adjusts affiliations, adds acknowledgmen

Comparative economic evaluation of data from the ACRIN national CT colonography trial with three cancer intervention and surveillance modeling network microsimulations

Purpose: To estimate the cost-effectiveness of computed tomographic (CT) colonography for colorectal cancer (CRC) screening in average-risk asymptomatic subjects in the United States aged 50 years. Materials and Methods: Enrollees in the American College of Radiology Imaging Network National CT Colonography Trial provided informed consent, and approval was obtained from the institutional review board at each site. CT colonography performance estimates from the trial were incorporated into three Cancer Intervention and Surveillance Modeling Network CRC microsimulations. Simulated survival and lifetime costs for screening 50-year-old subjects in the United States with CT colonography every 5 or 10 years were compared with those for guideline-concordant screening with colonoscopy, flexible sigmoidoscopy plus either sensitive unrehydrated fecal occult blood testing (FOBT) or fecal immunochemical testing (FIT), and no screening. Perfect and reduced screening adherence scenarios were considered. Incremental cost-effectiveness and net health benefits were estimated from the U.S. health care sector perspective, assuming a 3% discount rate. Results: CT colonography at 5- and 10-year screening intervals was more costly and less effective than FOBT plus flexible sigmoidoscopy in all three models in both 100% and 50% adherence scenarios. Colonoscopy also was more costly and less effective than FOBT plus flexible sigmoidoscopy, except in the CRC-SPIN model assuming 100% adherence (incremental cost-effectiveness ratio: $26 300 per life-year gained). CT colonography at 5- and 10-year screening intervals and colonoscopy were net beneficial compared with no screening in all model scenarios. The 5-year screening interval was net beneficial over the 10-year interval except in the MISCAN model when assuming 100$50 000 per life-year gained. Conclusion: All three models predict CT colonography to be more costly and less effective than non-CT colonographic screening but net beneficial compared with no screening given model assumptions

Depression, anxiety, stress, social interaction and health-related quality of life in men and women with unexplained chest pain

<p>Abstract</p> <p>Background</p> <p>Unexplained chest pain (UCP) is a common reason for emergency hospital admission and generates considerable health-care costs for society. Even though prior research indicates that psychological problems and impaired quality of life are common among UCP patients, there is lack of knowledge comparing UCP patients with a reference group from the general population. The aim of this study was to analyse differences between men and women with UCP and a reference group in terms of psychosocial factors as depression, anxiety, stress, social interaction and health-related quality of life (HRQOL).</p> <p>Methods</p> <p>A self-administered questionnaire about psychosocial factors was completed by 127 men and 104 women with acute UCP admitted consecutively to the Emergency Department (ED) or as in-patients on a medical ward. A reference group from the general population, 490 men and 579 women, participants in the INTERGENE study and free of clinical heart disease, were selected.</p> <p>Results</p> <p>The UCP patients were more likely to be immigrants, have a sedentary lifestyle, report stress at work and have symptoms of depression and trait-anxiety compared with the reference group. After adjustment for differences in age, smoking, hypertension and diabetes, these factors were still significantly more common among patients with UCP. In a stepwise multivariate model with mutual adjustment for psychosocial factors, being an immigrant was associated with a more than twofold risk in both sexes. Stress at work was associated with an almost fourfold increase in risk among men, whereas there was no independent impact for women. In contrast, depression only emerged as an independent risk factor in women. Trait-anxiety and a low level of social interaction were not independently associated with risk in either men or women. Patients with UCP were two to five times more likely to have low scores for HRQOL.</p> <p>Conclusion</p> <p>Both men and women with UCP had higher depression scores than referents, but an independent association was only found in women. Among men, perceived stress at work emerged as the only psychosocial variable significantly associated with UCP.</p