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Xiao H.Y.,Cornell University | Covey K.R.,Cornell University | Rebull L.,Spitzer Science Center Caltech | Charbonneau D.,Harvard University | And 4 more authors.
Astrophysical Journal, Supplement Series | Year: 2012

We analyze light curves obtained by the Trans-atlantic Exoplanet Survey (TrES) for a field centered on the L1495 dark cloud in Taurus. The Spitzer Taurus Legacy Survey catalog identifies 179 bona fide Taurus members within the TrES field; 48 of the known Taurus members are detected by TrES, as well as 26 candidate members identified by the Spitzer Legacy team. We quantify the variability of each star in our sample using the ratio of the standard deviation of the original light curve (σ orig.) to the standard deviation of a light curve that has been smoothed by 9 or 1001 epochs (σ 9 and σ 1001, respectively). Known Taurus members typically demonstrate (σ orig./σ 9) < 2.0, and (σ orig./σ 1001) < 5, while field stars reveal (σ orig./σ 9) ∼3.0 and (σ orig./σ 1001) ∼10, as expected for light curves dominated by unstructured white noise. Of the 74 Taurus members/candidates with TrES light curves, we detect significant variability in 49 sources. Adapting a quantitative metric originally developed to assess the reliability of transit detections, we measure the amount of red and white noise in each light curve and identify 18 known or candidate Taurus members with highly significant period measurements. These appear to be the first periods measured for four of these sources (HD 282276, CX Tau, FP Tau, TrES J042423+265008), and in two other cases, the first non-aliased periods (LkCa 21 and DK Tau AB). For the remainder, the TrES measurements typically agree very well (δP < 1%) with previously reported values. Including periods measured at lower confidence for 15 additional sources, we report periods for 11 objects where no previous periods were found, including 8 confirmed Taurus members. We also identify 10 of the 26 candidate Taurus members that demonstrate variability levels consistent with being bona fide TTauri stars. A Kolomgorov-Smirnov (K-S) test confirms that these new periods confirm the distinction between the rotation period distributions of stars with and without circumstellar disks, with only a 10% probability of the two populations sharing the same parent period distribution. K-S tests do suggest, however, that the updated Taurus period distribution now more closely resembles those measured in other young star-forming clusters (i.e., NGC2264, NGC6530, and the ONC). This improved agreement may reflect the exclusion of long rotation periods which are detected in Taurus at lower significance, and which may be beyond the limits of detectability in more distant star-forming regions. © 2012. The American Astronomical Society. All rights reserved.

Rebull L.M.,Spitzer Science Center Caltech | Guieu S.,European Southern Observatory | Stauffer J.R.,Spitzer Science Center Caltech | Hillenbrand L.A.,California Institute of Technology | And 8 more authors.
Astrophysical Journal, Supplement Series | Year: 2011

We present observations of ∼7 deg2 of the North American and Pelican Nebulae region at 24, 70, and 160 μm with the Spitzer Space Telescope Multiband Imaging Photometer for Spitzer (MIPS). We incorporate the MIPS observations with earlier Spitzer Infrared Array Camera (IRAC) observations, as well as archival near-infrared (IR) and optical data. We use the MIPS data to identify 1286 young stellar object (YSO) candidates. IRAC data alone can identify 806 more YSO candidates, for a total of 2076 YSO candidates. Prior to the Spitzer observations, there were only ∼200 YSOs known in this region. Three subregions within the complex are highlighted as clusters: the Gulf of Mexico, the Pelican, and the Pelican's Hat. The Gulf of Mexico cluster is subject to the highest extinction (AV at least ∼30) and has the widest range of infrared colors of the three clusters, including the largest excesses and by far the most point-source detections at 70 μm. Just 3% of the cluster members were previously identified; we have redefined this cluster as about 10-100 times larger (in projected area) than was previously realized. © 2011. The American Astronomical Society. All rights reserved.

Van Dyk S.D.,Spitzer Science Center Caltech | Cenko S.B.,University of California at Berkeley | Poznanski D.,Tel Aviv University | Arcavi I.,Weizmann Institute of Science | And 8 more authors.
Astrophysical Journal | Year: 2012

We report on the direct detection and characterization of the probable red supergiant (RSG) progenitor of the intermediate-luminosity TypeII-Plateau (II-P) supernova (SN) 2012aw in the nearby (10.0Mpc) spiral galaxy Messier 95 (M95; NGC3351). We have identified the star in both Hubble Space Telescope images of the host galaxy, obtained 17-18yr prior to the explosion, and near-infrared ground-based images, obtained 6-12yr prior to the SN. The luminous supergiant showed evidence for substantial circumstellar dust, manifested as excess line-of-sight extinction. The effective total-to-selective ratio of extinction to the star was R'V 4.35, which is significantly different from that of diffuse interstellar dust (i.e., RV = 3.1), and the total extinction to the star was therefore, on average, AV 3.1mag. We find that the observed spectral energy distribution for the progenitor star is consistent with an effective temperature of 3600K (spectral typeM3), and that the star therefore had a bolometric magnitude of -8.29. Through comparison with recent theoretical massive-star evolutionary tracks we can infer that the RSG progenitor had an initial mass 15 ≲ M ini(M ⊙) < 20. Interpolating by eye between the available tracks, we surmise that the star had initial mass 17-18 M ⊙. The circumstellar dust around the progenitor must have been destroyed in the explosion, as the visual extinction to the SN is found to be low (AV = 0.24mag with R V = 3.1). © 2012. The American Astronomical Society. All rights reserved.

Skinner S.L.,University of Colorado at Boulder | Rebull L.,Spitzer Science Center Caltech | Gudel M.,University of Vienna
Astronomical Journal | Year: 2014

The nearby Lynds 1228 (L1228) dark cloud at a distance of 200 pc is known to harbor several young stars including the driving sources of the giant HH 199 and HH 200 Herbig-Haro (HH) outflows. L1228 has previously been studied at optical, infrared, and radio wavelengths but not in X-rays. We present results of a sensitive 37 ks Chandra ACIS-I X-ray observation of the L1228 core region. Chandra detected 60 X-ray sources, most of which are faint (<40 counts) and non-variable. Infrared counterparts were identified for 53 of the 60 X-ray sources using archival data from the Two Micron All-Sky Survey, the Spitzer Space Telescope, and the Wide-field Infrared Survey Explorer. Object classes were assigned using mid-IR colors for those objects with complete photometry, most of which were found to have colors consistent with extragalactic background sources. Seven young stellar object candidates were identified including the class I protostar HH 200-IRS which was detected as a faint hard X-ray source. No X-ray emission was detected from the luminous protostar HH 199-IRS. We summarize the X-ray and infrared properties of the detected sources and provide IR spectral energy distribution modeling of high-interest objects including the protostars driving the HH outflows. © 2014. The American Astronomical Society. All rights reserved..

Kafka S.,Spitzer Science Center Caltech | Kafka S.,Carnegie Institution of Washington | Tappert C.,University of Chile | Tappert C.,University of Valparaíso | Honeycutt R.K.,Indiana University
Monthly Notices of the Royal Astronomical Society | Year: 2010

We present new red/near-infrared spectra of the low-accretion-rate polar J204827.9+005008.9. Compared to 2004 spectra in the literature, our 2008 data show more structured emission-line profiles. All emission lines in our spectra have two components at most orbital phases. The stronger component has a sinusoidal velocity variation (K∼ 120 km s-1) and is likely due to irradiation of the inner hemisphere of the secondary star by the white dwarf. Based on the appearance of the Hα Doppler tomogram, the weaker, larger amplitude, line component likely originates in a ballistic stream from the L1 point. J2048 is thought to be accreting via a wind from the secondary star, so the detection of velocity features consistent with the velocities of Roche lobe overflow is unexpected. It appears that J2048 was experiencing an interval of enhanced mass transfer during our observations. We briefly discuss scenarios that might lead to such a situation, such as changes in the chromospheric activity level on the secondary star. © 2010 The Authors. Journal compilation © 2010 RAS.

Furness J.P.,University of Sheffield | Crowther P.A.,University of Sheffield | Morris P.W.,NASA | Barbosa C.L.,University of Paraíba Valley | And 3 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2010

We present near-infrared Very Large Telescope/Infrared Spectrograph and Array Camera and mid-infrared (mid-IR) Spitzer/Infrared Spectrograph spectroscopy of the young massive cluster in the W31 star-forming region. H-band spectroscopy provides refined classifications for four cluster member O stars with respect to Blum et al. In addition, photospheric features are detected in the massive young stellar object (massive YSO) μ26. Spectroscopy permits estimates of stellar temperatures and masses, from which a cluster age of ∼0.6 Myr and distance of 3.3 kpc are obtained, in excellent agreement with Blum et al. IRS spectroscopy reveals mid-IR fine structure line fluxes of [Ne ii-iii] and [S iii-iv] for four O stars and five massive YSOs. In common with previous studies, stellar temperatures of individual stars are severely underestimated from the observed ratios of fine-structure lines, despite the use of contemporary stellar atmosphere and photoionization models. We construct empirical temperature calibrations based upon the W31 cluster stars of known spectral type, supplemented by two inner Milky Way ultracompact (UC) H ii regions whose ionizing star properties are established. Calibrations involving [Ne iii] 15.5 μm/[Ne ii] 12.8 μm, [S iv] 10.5 μm/[Ne ii] 12.8 μm or [Ar iii] 9.0 μm/[Ne ii] 12.8 μm have application in deducing the spectral types of early to mid O stars for other inner Milky Way compact and UC H ii regions. Finally, evolutionary phases and time-scales for the massive stellar content in W31 are discussed, due to the presence of numerous young massive stars at different formation phases in a 'coeval' cluster. © 2010 The Authors. Journal compilation © 2010 RAS.

Wolff S.C.,NOAO | Strom S.E.,NOAO | Rebull L.M.,Spitzer Science Center Caltech
Astrophysical Journal | Year: 2011

We report the results of a study of the intermediate-and high-mass stars in the young, rich star-forming complex IC 1805, based on a combination of optical, near-infrared, and mid-infrared photometry, and classification spectra. These data provide the basis for characterizing the masses and ages for stars more massive than ∼2 M⊙ and enable a study of the frequency and character of circumstellar disks associated with intermediate-and high-mass stars. Optically thick accretion disks among stars with masses 2 < M/M ⊙ < 4 are rare (∼2% of members) and absent among more massive stars. A larger fraction (∼10%) of stars with masses 2 < M/M ⊙ < 4 appear to be surrounded by disks that have evolved from the initial optically thick accretion phase. We identify four classes of such disks. These classes are based on spectral energy distributions (SEDs) of excess emission above photospheric levels: disks that are (1) optically thin based on the magnitude of the observed excess emission from 2 to 24 μm, (2) optically thin in their inner regions (r < 20 AU) and optically thick in their outer regions, (3) exhibit empty inner regions (r < 10 AU) and optically thin emission in their outer regions, and (4) exhibit empty inner regions and optically thick outer regions. We discuss, and assess the merits and liabilities of, proposed explanations for disks exhibiting these SED types and suggest additional observations that would test these proposals. © 2011. The American Astronomical Society. All rights reserved. Printed in the U.S.A.

Van Dyk S.D.,Spitzer Science Center Caltech
Astronomical Journal | Year: 2013

Type IIn supernovae (SNe IIn) have been found to be associated with significant amounts of dust. These core-collapse events are generally expected to be the final stage in the evolution of highly massive stars, either while in an extreme red supergiant phase or during a luminous blue variable phase. Both evolutionary scenarios involve substantial pre-supernova mass loss. I have analyzed the SN IIn 1995N in MCG -02-38-017 (Arp 261), for which mid-infrared archival data obtained with the Spitzer Space Telescope in 2009 (∼14.7 yr after explosion) and with the Wide-field Infrared Survey Explorer in 2010 (∼15.6-16.0 yr after explosion) reveal a luminous (∼2 × 10 7 L ⊙) source detected from 3.4 to 24 μm. These observations probe the circumstellar material, set up by pre-SN mass loss, around the progenitor star and indicate the presence of ∼0.05-0.12 M ⊙ of pre-existing, cool dust at ∼240 K. This is at least a factor ∼10 lower than the dust mass required to be produced from SNe at high redshift, but the case of SN 1995N lends further evidence that highly massive stars could themselves be important sources of dust. © 2013. The American Astronomical Society. All rights reserved.

Van Dyk S.D.,Spitzer Science Center Caltech | Zheng W.,University of California at Berkeley | Clubb K.I.,University of California at Berkeley | Filippenko A.V.,University of California at Berkeley | And 7 more authors.
Astrophysical Journal Letters | Year: 2013

We conducted Hubble Space Telescope (HST) Snapshot observations of the Type IIb supernova (SN) 2011dh in M51 at an age of 641 days with the Wide Field Camera 3. We find that the yellow supergiant star, clearly detected in pre-SN HST images, has disappeared, implying that this star was almost certainly the progenitor of the SN. Interpretation of the early time SN data which led to the inference of a compact nature for the progenitor, and to the expected survival of this yellow supergiant, is now clearly incorrect. We also present ground-based UBVRI light curves obtained with the Katzman Automatic Imaging Telescope at Lick Observatory up to SN age 70 days. From the light-curve shape including the very late time HST data, and from recent interacting binary models for SN 2011dh, we estimate that a putative surviving companion star to the now deceased yellow supergiant could be detectable by late 2013, especially in the ultraviolet. No obvious light echoes are detectable yet in the SN environment. © 2013. The American Astronomical Society. All rights reserved.

Laine S.,Spitzer Science Center Caltech | Krause M.,Max Planck Institute for Radio Astronomy | Tabatabaei F.S.,Max Planck Institute for Radio Astronomy | Siopis C.,Free University of Colombia
Astronomical Journal | Year: 2010

We obtained Spitzer/IRAC 3.6-8 μm images of the nearby spiral galaxy NGC 4258 to study possible interactions between dust and the radio jet. In our analysis, we also included high-resolution radio continuum, Hα, CO, and X-ray data. Our data reveal that the 8 μm emission, believed to originate largely from polycyclic aromatic hydrocarbon molecules and hot dust, is an excellent tracer of the normal spiral structure in NGC 4258, and hence it originates from the galactic plane. We investigated the possibility of dust destruction by the radio jet by calculating correlation coefficients between the 8 μm and radio continuum emissions along the jet in two independent ways, namely, (1) from wavelet-transformed maps of the original images at different spatial scales and (2) from one-dimensional intensity cuts perpendicular to the projected path of the radio jet on the sky. No definitive sign of a correlation (or anticorrelation) was detected on relevant spatial scales with either approach, implying that any dust destruction must take place at spatial scales that are not resolved by our observations. © 2010. The American Astronomical Society. All rights reserved.

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