- ID:
- ivo://CDS.VizieR/J/A+A/617/A6
- Title:
- Seven new pulsating sdA stars
- Short Name:
- J/A+A/617/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The nature of the recently identified "sdA" spectroscopic class of star is not well understood. The thousands of known sdAs have H-dominated spectra, spectroscopic surface gravities intermediate to main sequence stars and isolated white dwarfs, and effective temperatures below the lower limit for He-burning subdwarfs. Most are likely products of binary stellar evolution, whether extremely low-mass white dwarfs and their precursors, or blue stragglers in the halo. Stellar eigenfrequencies revealed through time series photometry of pulsating stars sensitively probe stellar structural properties. The properties of pulsations exhibited by any sdA stars would contribute importantly to our developing understanding of this class. We extend our photometric campaign to discover pulsating extremely low-mass white dwarfs from McDonald Observatory to target sdA stars classified from SDSS spectra. We also obtain follow-up time series spectroscopy to search for binary signatures from four new pulsators. Out of 23 sdA stars observed, we clearly detect stellar pulsations in seven. Dominant pulsation periods range from 4.6 minutes to 12.3 hours, with most on hour timescales. We argue specific classifications for some of the new variables, identifying both compact and likely main sequence dwarf pulsators, along with a candidate low-mass RR Lyrae star. With dominant pulsation periods spanning orders of magnitude, the pulsational evidence supports the emerging narrative that the sdA class consists of multiple stellar populations. Since multiple types of sdA exhibit stellar pulsations, follow-up asteroseismic analysis can be used to probe the precise evolutionary natures and stellar structures of these individual subpopulations.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/469/4341
- Title:
- Seven recent novae BVI light curves
- Short Name:
- J/MNRAS/469/4341
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The BVI light curves of seven recent novae (i.e. V1534 Sco, V1535 Sco, V2949 Oph, V3661 Oph, MASTER OT J010603.18-744715.8, TCP J18102829-2729590 and ASASSN-16ma) have been extensively mapped with daily robotic observations from Atacama (Chile): five belong to the Galactic bulge, one to the Small Magellanic Cloud and another is a Galactic disc object. The two programme novae detected in {gamma}-rays by Fermi-LAT (i.e. TCP J18102829-2729590 and ASASSN-16ma) are bulge objects with unevolved companions. They distinguish themselves by showing a double-component optical light curve. The first component to develop is the fireball from freely expanding, ballistic-launched ejecta, with a time of passage through maximum that is strongly dependent on wavelength (~1d delay between the B and I bands). The second component, emerging simultaneously with the nova detection in {gamma}-rays, evolves at a slower pace, its optical brightness being proportional to the {gamma}-ray flux, and its passage through maximum not dependent on wavelength. The fact that {gamma}-rays are detected at a flux level that differs by four times from novae at the distance of the bulge seems to suggest that {gamma}-ray emission is not a widespread property of normal novae. We discuss the advantages offered by high-quality photometric observations collected with only one telescope (as opposed to data provided by a number of different instruments). We also observe the effects of the wavelength dependence of fireball expansion, the recombination in the flashed wind of a giant companion, the subtle presence of hiccups and plateaus, and the super-soft X-ray emission and its switch-off. Four programme novae (V2949 Oph, V3661 Oph, TCP J18102829-2729590 and ASASSN-16ma) have normal dwarf companions: V1534 Sco contains an M3 III giant, V1535 Sco a K-type giant and MASTER OT J010603.18-744715.8 a subgiant. We also comment briefly on the maximum absolute magnitude relation with decline time (MMRD).
- ID:
- ivo://CDS.VizieR/J/A+A/611/A48
- Title:
- Seven sdB eclipsing binaries data
- Short Name:
- J/A+A/611/A48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We review the eclipse time variations exhibited by seven sdB eclipsing binaries to establish if data collected over the last 2 decades can reliably predict the presence of two or more circumbinary bodies.
5914. SEXSI catalog. II
- ID:
- ivo://CDS.VizieR/J/ApJS/156/35
- Title:
- SEXSI catalog. II
- Short Name:
- J/ApJS/156/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Serendipitous Extragalactic X-ray Source Identification (SEXSI) Program is designed to expand significantly the sample of identified extragalactic hard X-ray sources at intermediate fluxes, 10^-13^ergs/cm^2^/s<~S_2-10keV_<10^-15^ergs/cm^2^/s. SEXSI, which includes sources derived from more than 2{deg}^2^ of Chandra images, provides the largest hard X-ray-selected sample yet studied, offering an essential complement to the Chandra Deep Fields (total area 0.2{deg}^2^). In this paper we describe R-band optical imaging of the SEXSI fields from the Palomar, MDM, and Keck observatories. We have identified counterparts or derived flux limits for nearly 1000 hard X-ray sources. Using the optical images, we derive accurate source positions. We investigate correlations between optical and X-ray flux, and optical flux and X-ray hardness ratio. We also study the density of optical sources surrounding X-ray counterparts, as well as the properties of optically faint, hard X-ray sources.
5915. SEXSI catalog. III
- ID:
- ivo://CDS.VizieR/J/ApJS/165/19
- Title:
- SEXSI catalog. III
- Short Name:
- J/ApJS/165/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the catalog of 477 spectra from the Serendipitous Extragalactic X-ray Source Identification (SEXSI) program, a survey designed to probe the dominant contributors to the 2-10keV cosmic X-ray background. Our survey covers 1deg^2^ of sky to 2-10keV fluxes of 1x10^-14^ergs/cm^2^/s, and 2deg^2^ for fluxes of 3x10^-14^ergs/cm^2^/s. Our spectra reach to R-band magnitudes of ~<24 and have produced identifications and redshifts for 438 hard X-ray sources.
5916. SEXSI Spitzer catalog
- ID:
- ivo://CDS.VizieR/J/ApJ/708/584
- Title:
- SEXSI Spitzer catalog
- Short Name:
- J/ApJ/708/584
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare the relative merits of active galactic nuclei (AGNs) selection at X-ray and mid-infrared wavelengths using data from moderately deep fields observed by both Chandra and Spitzer. The X-ray-selected AGN sample and associated photometric and spectroscopic optical follow-up are drawn from a subset of fields studied as part of the Serendipitous Extragalactic X-ray Source Identification (SEXSI) program. Mid-infrared data in these fields are derived from targeted and archival Spitzer imaging, and mid-infrared AGN selection is accomplished primarily through application of the Infrared Array Camera (IRAC) color-color AGN "wedge" selection technique. Nearly all X-ray sources in these fields which exhibit clear spectroscopic signatures of AGN activity have mid-infrared colors consistent with IRAC AGN selection. These are predominantly the most luminous X-ray sources. X-ray sources that lack high-ionization and/or broad lines in their optical spectra are far less likely to be selected as AGNs by mid-infrared color selection techniques. The fraction of X-ray sources identified as AGNs in the mid-infrared increases monotonically as the X-ray luminosity increases. Conversely, only 22% of mid-infrared-selected AGNs are detected at X-ray energies in the moderately deep (t_exp_~100ks) SEXSI Chandra data.
- ID:
- ivo://CDS.VizieR/J/ApJ/788/159
- Title:
- 17 Seyfert 1 galaxies light curves
- Short Name:
- J/ApJ/788/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a dust reverberation survey for 17 nearby Seyfert 1 galaxies, which provides the largest homogeneous data collection for the radius of the innermost dust torus. A delayed response of the K-band light curve after the V-band light curve was found for all targets, and 49 measurements of lag times between the flux variation of the dust emission in the K band and that of the optical continuum emission in the V band were obtained by the cross-correlation function analysis and also by an alternative method for estimating the maximum likelihood lag. The lag times strongly correlated with the optical luminosity in the luminosity range of M_V_=-16 to -22 mag, and the regression analysis was performed to obtain the correlation log {Delta}t (days)=-2.11 -0.2 M_V_ assuming {Delta}t{prop.to}L^0.5^, which was theoretically expected. We discuss the possible origins of the intrinsic scatter of the dust lag-luminosity correlation, which was estimated to be approximately 0.13 dex, and we find that the difference of internal extinction and delayed response of changes in lag times to the flux variations could have partly contributed to intrinsic scatter. However, we could not detect any systematic change of the correlation with the subclass of the Seyfert type or the Eddington ratio. Finally, we compare the dust reverberation radius with the near-infrared interferometric radius of the dust torus and the reverberation radius of broad Balmer emission lines. The interferometric radius in the K band was found to be systematically larger than the dust reverberation radius in the same band by the about a factor of two, which could be interpreted by the difference between the flux-weighted radius and response-weighted radius of the innermost dust torus. The reverberation radius of the broad Balmer emission lines was found to be systematically smaller than the dust reverberation radius by about a factor of four to five, which strongly supports the unified scheme of the Seyfert type of active galactic nuclei (AGNs). Moreover, we examined the radius-luminosity correlations for the hard X-ray (14-195 keV) and the [O IV] {lambda}25.89 {mu}m emission-line luminosities, which would be applicable for obscured AGNs.
- ID:
- ivo://CDS.VizieR/J/ApJS/172/599
- Title:
- SFI++ II. A new I-band Tully-Fisher catalog
- Short Name:
- J/ApJS/172/599
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the SFI++ data set, a homogeneously derived catalog of photometric and rotational properties and the Tully-Fisher distances and peculiar velocities derived from them. We make use of digital optical images, optical long-slit spectra, and global HI line profiles to extract parameters of relevance to disk scaling relations, incorporating several previously published data sets as well as a new photometric sample of some 2000 objects. According to the completeness of available redshift samples over the sky area, we exploit both a modified percolation algorithm and the Voronoi-Delaunay method to assign individual galaxies to groups as well as clusters, thereby reducing scatter introduced by local orbital motions. We also provide corrections to the peculiar velocities for both homogeneous and inhomogeneous Malmquist bias, making use of the 2MASS Redshift Survey density field to approximate large-scale structure. The final SFI++ peculiar velocity catalog contains 4861 field and cluster galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJS/229/28
- Title:
- SFiNCs: X-ray, IR and membership catalogs
- Short Name:
- J/ApJS/229/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Star Formation in Nearby Clouds (SFiNCs) project is aimed at providing a detailed study of the young stellar populations and of star cluster formation in the nearby 22 star-forming regions (SFRs) for comparison with our earlier MYStIX survey of richer, more distant clusters. As a foundation for the SFiNCs science studies, here, homogeneous data analyses of the Chandra X-ray and Spitzer mid-infrared archival SFiNCs data are described, and the resulting catalogs of over 15300 X-ray and over 1630000 mid-infrared point sources are presented. On the basis of their X-ray/infrared properties and spatial distributions, nearly 8500 point sources have been identified as probable young stellar members of the SFiNCs regions. Compared to the existing X-ray/mid-infrared publications, the SFiNCs member list increases the census of YSO members by 6%-200% for individual SFRs and by 40% for the merged sample of all 22 SFiNCs SFRs.
- ID:
- ivo://CDS.VizieR/J/ApJS/219/8
- Title:
- SFR for WISE + SDSS spectroscopic galaxies
- Short Name:
- J/ApJS/219/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine Sloan Digitital Sky Survey (SDSS) and WISE photometry for the full SDSS spectroscopic galaxy sample, creating spectral energy distributions (SEDs) that cover {lambda}=0.4-22{mu}m for an unprecedentedly large and comprehensive sample of 858365 present-epoch galaxies. Using MAGPHYS (da Cunha+ 2008MNRAS.388.1595D), we then simultaneously and consistently model both the attenuated stellar SED and the dust emission at 12 and 22{mu}m, producing robust new calibrations for monochromatic mid-IR star formation rate (SFR) proxies. These modeling results provide the first mid-IR-based view of the bimodality in star formation activity among galaxies, exhibiting the sequence of star-forming galaxies ("main sequence") with a slope of dlogSFR/dlogM_*_=0.80 and a scatter of 0.39dex. We find that these new SFRs along the SF main sequence are systematically lower by a factor of 1.4 than those derived from optical spectroscopy. We show that for most present-day galaxies, the 0.4-22{mu}m SED fits can exquisitely predict the fluxes measured by Herschel at much longer wavelengths. Our analysis also illustrates that the majority of stars in the present-day universe are formed in luminous galaxies (~L*) in and around the "green valley" of the color-luminosity plane. We make publicly available the matched photometry catalog and SED modeling results.