- ID:
- ivo://CDS.VizieR/J/ApJ/788/154
- Title:
- Palomar Transient Factory SNe IIn photometry
- Short Name:
- J/ApJ/788/154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Interaction of supernova (SN) ejecta with the optically thick circumstellar medium (CSM) of a progenitor star can result in a bright, long-lived shock-breakout event. Candidates for such SNe include Type IIn and superluminous SNe. If some of these SNe are powered by interaction, then there should be a specific relation between their peak luminosity, bolometric light-curve rise time, and shock-breakout velocity. Given that the shock velocity during shock breakout is not measured, we expect a correlation, with a significant spread, between the rise time and the peak luminosity of these SNe. Here, we present a sample of 15 SNe IIn for which we have good constraints on their rise time and peak luminosity from observations obtained using the Palomar Transient Factory. We report on a possible correlation between the R-band rise time and peak luminosity of these SNe, with a false-alarm probability of 3%. Assuming that these SNe are powered by interaction, combining these observables and theory allows us to deduce lower limits on the shock-breakout velocity. The lower limits on the shock velocity we find are consistent with what is expected for SNe (i.e., ~10^4^ km/s). This supports the suggestion that the early-time light curves of SNe IIn are caused by shock breakout in a dense CSM. We note that such a correlation can arise from other physical mechanisms. Performing such a test on other classes of SNe (e.g., superluminous SNe) can be used to rule out the interaction model for a class of events.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/152/19
- Title:
- Pan-Pacific Planet Search (PPPS). V. 164 stars
- Short Name:
- J/AJ/152/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spectroscopic stellar parameters for the complete target list of 164 evolved stars from the Pan-Pacific Planet Search, a five-year radial velocity campaign using the 3.9m Anglo-Australian Telescope. For 87 of these bright giants, our work represents the first determination of their fundamental parameters. Our results carry typical uncertainties of 100K, 0.15dex, and 0.1dex in T_eff_, logg, and [Fe/H] and are consistent with literature values where available. The derived stellar masses have a mean of 1.31_-0.25_^+0.28^M_{Sun}_, with a tail extending to ~2M_{Sun}_, consistent with the interpretation of these targets as "retired" A-F type stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/786/97
- Title:
- Photospheric properties of T Tauri stars
- Short Name:
- J/ApJ/786/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Estimates of the mass and age of young stars from their location in the H-R diagram are limited by not only the typical observational uncertainties that apply to field stars, but also by large systematic uncertainties related to circumstellar phenomena. In this paper, we analyze flux-calibrated optical spectra to measure accurate spectral types and extinctions of 281 nearby T Tauri stars (TTSs). The primary advances in this paper are (1) the incorporation of a simplistic accretion continuum in optical spectral type and extinction measurements calculated over the full optical wavelength range and (2) the uniform analysis of a large sample of stars, many of which are well known and can serve as benchmarks. Comparisons between the non-accreting TTS photospheric templates and stellar photosphere models are used to derive conversions from spectral type to temperature. Differences between spectral types can be subtle and difficult to discern, especially when accounting for accretion and extinction. The spectral types measured here are mostly consistent with spectral types measured over the past decade. However, our new spectral types are one to two subclasses later than literature spectral types for the original members of the TW Hya Association (TWA) and are discrepant with literature values for some well-known members of the Taurus Molecular Cloud. Our extinction measurements are consistent with other optical extinction measurements but are typically 1 mag lower than near-IR measurements, likely the result of methodological differences and the presence of near-IR excesses in most CTTSs. As an illustration of the impact of accretion, spectral type, and extinction uncertainties on the H-R diagrams of young clusters, we find that the resulting luminosity spread of stars in the TWA is 15%-30%. The luminosity spread in the TWA and previously measured for binary stars in Taurus suggests that for a majority of stars, protostellar accretion rates are not large enough to significantly alter the subsequent evolution.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A24
- Title:
- Pipe nebula optical-depth, column-density maps
- Short Name:
- J/A+A/620/A24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Multi-wavelength observations in the sub-mm regime provide information on the distribution of both the dust column density and the effective dust temperature in molecular clouds. In this study, we created high-resolution and high-dynamic-range maps of the Pipe nebula region and explored the value of dust-temperature measurements in particular towards the dense cores embedded in the cloud. The maps are based on data from the Herschel and Planck satellites, and calibrated with a near-infrared extinction map based on 2MASS observations. We have considered a sample of previously defined cores and found that the majority of core regions contain at least one local temperature minimum. Moreover, we observed an anti-correlation between column density and temperature. The slope of this anti-correlation is dependent on the region boundaries and can be used as a metric to distinguish dense from diffuse areas in the cloud if systematic effects are addressed appropriately. Employing dust-temperature data thus allows us to draw conclusions on the thermodynamically dominant processes in this sample of cores: external heating by the interstellar radiation field and shielding by the surrounding medium. In addition, we have taken a first step towards a physically motivated core definition by recognising that the column-density-temperature anti-correlation is sensitive to the core boundaries. Dust-temperature maps therefore clearly contain valuable information about the physical state of the observed medium.
- ID:
- ivo://CDS.VizieR/J/AJ/154/134
- Title:
- Planetary-mass brown dwarfs in the Taurus SFR
- Short Name:
- J/AJ/154/134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the initial results from a survey for planetary-mass brown dwarfs in the Taurus star-forming region. We have identified brown dwarf candidates in Taurus using proper motions and photometry from several ground- and space- based facilities. Through spectroscopy of some of the more promising candidates, we have found 18 new members of Taurus. They have spectral types ranging from mid-M to early-L, and they include the four faintest known members in extinction-corrected K_s_, which should have masses as low as ~4-5 M_Jup_ according to evolutionary models. Two of the coolest new members (M9.25, M9.5) have mid-IR excesses that indicate the presence of disks. Two fainter objects with types of M9-L2 and M9-L3 also have red mid-IR colors relative to photospheres at =<L0, but since the photospheric colors are poorly defined at >L0, it is unclear whether they have excesses from disks. We also have obtained spectra of candidate members of the IC 348 and NGC 1333 clusters in Perseus that were identified by Luhman et al. Eight candidates are found to be probable members, three of which are among the faintest and least-massive known members of the clusters (~5 M_Jup_).
- ID:
- ivo://CDS.VizieR/J/A+A/654/A93
- Title:
- Polar dust obscuration in broad-line AGN
- Short Name:
- J/A+A/654/A93
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We study a sample of 1275 broad-line AGN in the XMM-XXL field, with optical to infrared photometric data. These AGN are seen along their polar direction and we expect a maximal impact of dust located around the poles when it is present. We use X-CIGALE, which introduces a dust component to account for obscuration along the polar directions, modeled as a foreground screen, and an extinction curve that is chosen as it steepens significantly at short wavelengths or is much grayer. By comparing the results of different fits, we are able to define subsamples of sources with positive statistical evidence in favor of or against polar obscuration (if present) and described using the gray or steep extinction curve. We find a similar fraction of sources with positive evidence for and against polar dust. Applying statistical corrections, we estimate that half of our sample could contain polar dust and among them, 60% exhibit a steep extinction curve and 40% a flat extinction curve; although these latter percentages are found to depend on the adopted extinction curves. The obscuration in the V-band is not found to correlate with the X-ray column density, while A_V_/N_H_ ratios span a large range of values and higher dust temperatures are found with the flat, rather than with the steep extinction curve. Ignoring this polar dust component in the fit of the spectral energy distribution of these composite systems leads to an overestimation of the stellar contribution. A single fit with a polar dust component described with an SMC extinction curve efficiently overcomes this issue but it fails at identifying all the AGN with polar dust obscuration.
- ID:
- ivo://CDS.VizieR/J/ApJ/849/157
- Title:
- Polarimetry obs. toward IC5146 background stars
- Short Name:
- J/ApJ/849/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical and near-infrared stellar polarization observations toward the dark filamentary clouds associated with IC5146. The data allow us to investigate the dust properties (this paper) and the magnetic field structure (Paper II). A total of 2022 background stars were detected in the Rc, i', H, and/or K bands to A_V_<~25mag. The ratio of the polarization percentage at different wavelengths provides an estimate of {lambda}_max_, the wavelength of the peak polarization, which is an indicator of the small-size cutoff of the grain size distribution. The grain size distribution seems to significantly change at A_V_~3mag, where both the average and dispersion of P_Rc_/P_H_ decrease. In addition, we found {lambda}_max_~0.6-0.9{mu}m for A_V_>2.5mag, which is larger than the ~0.55{mu}m in the general interstellar medium (ISM), suggesting that grain growth has already started in low-AV regions. Our data also reveal that polarization efficiency (PE=P_{lambda}_/A_V_) decreases with A_V_ as a power law in the Rc, i', and K bands with indices of -0.71+/-0.10, -1.23+/-0.10, and -0.53+/-0.09. However, H-band data show a power index change; the PE varies with A_V_ steeply (index of -0.95+/-0.30) when A_V_<2.88+/-0.67mag, but softly (index of -0.25+/-0.06) for greater AV values. The soft decay of PE in high-AV regions is consistent with the radiative alignment torque model, suggesting that our data trace the magnetic field to A_V_~20mag. Furthermore, the breakpoint found in the H band is similar to that for A_V_, where we found the P_Rc_/P_H_ dispersion significantly decreased. Therefore, the flat PE-A_V_ in high-A_V_ regions implies that the power-index changes result from additional grain growth.
- ID:
- ivo://CDS.VizieR/J/ApJ/720/1045
- Title:
- Polarimetry toward sightlines through ChaI
- Short Name:
- J/ApJ/720/1045
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained optical multi-band polarimetry toward sightlines through the Chamaeleon I cloud, particularly in the vicinity of the young B9/A0 star HD 97300. We show, in agreement with earlier studies, that the radiation field impinging on the cloud in the projected vicinity of the star is dominated by the flux from the star, as evidenced by a local enhancement in the grain heating. By comparing the differential grain heating with the differential change in the location of the peak of the polarization curve, we show that the grain alignment is enhanced by the increase in the radiation field. We also find a weak, but measurable, variation in the grain alignment with the relative angle between the radiation field anisotropy and the magnetic field direction. Such an anisotropy in the grain alignment is consistent with a unique prediction of modern radiative alignment torque theory and provides direct support for radiatively driven grain alignment.
- ID:
- ivo://CDS.VizieR/J/ApJ/741/21
- Title:
- Polarization of stars in Taurus
- Short Name:
- J/ApJ/741/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present maps of the plane-of-sky magnetic field within two regions of the Taurus molecular cloud: one in the dense core L1495/B213 filament and the other in a diffuse region to the west. The field is measured from the polarization of background starlight seen through the cloud. In total, we measured 287 high-quality near-infrared polarization vectors in these regions. In L1495/B213, the percent polarization increases with column density up to A_V_~9mag, the limits of our data. The radiative torques model for grain alignment can explain this behavior, but models that invoke turbulence are inconsistent with the data. We also combine our data with published optical and near-infrared polarization measurements in Taurus. Using this large sample, we estimate the strength of the plane-of-sky component of the magnetic field in nine subregions. This estimation is done with two different techniques that use the observed dispersion in polarization angles. Our values range from 5 to 82uG and tend to be higher in denser regions. In all subregions, the critical index of the mass-to-magnetic flux ratio is sub-unity, implying that Taurus is magnetically supported on large scales (~2pc). Within the region observed, the B213 filament takes a sharp turn to the north and the direction of the magnetic field also takes a sharp turn, switching from being perpendicular to the filament to becoming parallel. This behavior can be understood if we are observing the rim of a bubble. We argue that it has resulted from a supernova remnant associated with a recently discovered nearby gamma-ray pulsar.
- ID:
- ivo://CDS.VizieR/J/ApJ/875/64
- Title:
- Polarization & photom. of stars toward LDN1225
- Short Name:
- J/ApJ/875/64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results based on the optical R-band observations of the polarization of 280 stars distributed toward the dark globule LDN1225. Parallaxes from Gaia data release 2 along with the polarization data of ~200 stars have been used to (a) constrain the distance of LDN 1225 as 830+/-83pc, (b) determine the contribution of interstellar polarization, and (c) characterize the dust properties and delineate the magnetic field (B-field) morphology of LDN 1225. We find that B-fields are more organized and exhibit a small dispersion of 12{deg}. Using the ^12^CO molecular line data from the Purple Mountain Observatory, along with the column density and dispersion in B-fields, we estimate the B-field strength to be ~56+/-10{mu}G, the ratio of magnetic to turbulent pressure to be ~3+/-2, and the ratio of mass to magnetic flux (in units of the critical value) to be <1. These results indicate the dominant role of B-fields in comparison to turbulence and gravity in rendering the cloud support. B-fields are aligned parallel to the low-density parts (traced by a ^12^CO map) of the cloud; in contrast, they are neither parallel nor perpendicular to the high-density core structures (traced by ^13^CO and C^18^O maps). LDN1225 hosts two 70{mu}m sources, which seem to be low-mass Class 0 sources. The ratio of total to selective extinction derived using optical and near-infrared photometric data is found to be anomalous (RV=3.4), suggesting the growth of dust grains in LDN 1225. The polarization efficiency of dust grains follows a power law with an index of -0.7, implying that optical polarimetry traces B-fields in the outer parts of the cloud.
