- ID:
- ivo://CDS.VizieR/J/ApJ/761/162
- Title:
- Tycho-2 stars in Galactic Bulge Survey
- Short Name:
- J/ApJ/761/162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify 69 X-ray sources discovered by the Galactic Bulge Survey (GBS) that are coincident with or very close to bright stars in the Tycho-2 catalog. Additionally, two other GBS sources are resolved binary companions to Tycho-2 stars where both components are separately detected in X-rays. Most of these are likely to be real matches, but we identify nine objects with large and significant X-ray-to-optical offsets as either detections of resolved binary companions or chance alignments. We collate known spectral types for these objects, and also examine Two Micron All Sky Survey colors, variability information from the All-Sky Automated Survey, and X-ray hardness ratios for the brightest objects. Nearly a third of the stars are found to be optically variable, divided roughly evenly between irregular variations and periodic modulations. All fall among the softest objects identified by the GBS. The sample forms a very mixed selection, ranging in spectral class from O9 to M3. In some cases, the X-ray emission appears consistent with normal coronal emission from late-type stars, or wind emission from early-types, but the sample also includes one known Algol, one W UMa system, two Be stars, and several X-ray bright objects likely to be coronally active stars or binaries. Surprisingly, a substantial fraction of the spectroscopically classified, non-coincidental sample (12 out of 38 objects) have late B or A type counterparts. Many of these exhibit redder near-IR colors than expected for their spectral type and/or variability, and it is likely that the X-rays originate from a late-type companion star in most or all of these objects.
Number of results to display per page
Search Results
14482. Tycho-2 stars with IR excess
- ID:
- ivo://CDS.VizieR/J/MNRAS/363/1111
- Title:
- Tycho-2 stars with IR excess
- Short Name:
- J/MNRAS/363/1111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stars of all evolutionary phases have been found to have excess infrared emission due to the presence of circumstellar material. To identify such stars, we have positionally correlated the infrared Mid-Course Space Experiment (MSX) Point Source Catalogue (<V/114>) and the Tycho-2 optical catalogue (<I/259>). Near-mid-infrared colour criteria have been developed to select infrared excess stars. The search yielded 1938 excess stars; over half (979) have never previously been detected by IRAS. The excess stars were found to be young objects such as Herbig Ae/Be and Be stars, and evolved objects such as OH/IR (infrared) and carbon stars. A number of B-type excess stars were also discovered whose infrared colours could not be readily explained by known catalogued objects.
14483. Tycho variables stars
- ID:
- ivo://CDS.VizieR/II/233
- Title:
- Tycho variables stars
- Short Name:
- II/233
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the classification procedure described in Piquard's PhD thesis applied to the 1091 stars presented in Piquard et al. (2001. Cat. <J/A+A/373/576>). In those six tables we give indication of variability type for all the stars detected as variables in Piquard et al. (2001, Cat. <J/A+A/373/576>). First of all, we looked for periodic signals in the light curves using adapted Renson's (Renson, 1978A&A....63..125R) and Stellingwerf's (Stellingwerf, 1978ApJ...224..953S) methods applied to the tree different photometric bands from Tycho (Cat. <I/239>): T, B_T_, V_T_ (the T band is defined from the added count-rates in the B_T_ and V_T_ channels, Grossmann et al.. 1995A&A...304..110G). Then we developed a semi-automatic method using 5 parameters (Period, color index, reduced proper motion from Tycho-2 catalogue (Cat. <I/259>), 2 indicators of the shape of the light curve) and a maximum likelihood method, combined with a careful look on the light curves. Finaly, the identification of the variability type is kept only if the resulting light curve is convincing (periodic the star has the P status, if not periodic the star has the U status); else we need more information about the star and is has the A status. All this identifications are indications since the quality of the light curves are often poor, particularly when the star is fainter than T=10.
14484. Type 1 AGN at low z. II.
- ID:
- ivo://CDS.VizieR/J/MNRAS/426/2703
- Title:
- Type 1 AGN at low z. II.
- Short Name:
- J/MNRAS/426/2703
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the relative strength of the narrow emission lines in a Sloan Digital Sky Survey based sample of broad H{alpha} selected active galactic nuclei (AGN), defined in Paper I (Stern & Laor, 2010, Cat. J/MNRAS/423/600).
14485. Type 1 AGN at low z. III.
- ID:
- ivo://CDS.VizieR/J/MNRAS/431/836
- Title:
- Type 1 AGN at low z. III.
- Short Name:
- J/MNRAS/431/836
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the optical narrow-line ratios in a Sloan Digital Sky Survey (SDSS) based sample of 3175 broad H{alpha} selected type 1 active galactic nuclei (AGN), and explore their positions in the BPT diagrams as a function of the AGN and the host properties. We find the following: (1) the luminosities of all measured narrow lines (H{alpha}, H{beta}, [OIII], [NII], [SII], [OI]) show a Baldwin relation relative to the broad H{alpha} luminosity LbH{alpha}, with slopes in the range of 0.53-0.72. (2) About 20 percent of the type 1 AGN reside within the "Composite" and "star-forming" (SF) regions of the Baldwin, Phillips & Terlevich (BPT) diagrams. These objects also show excess narrow H{alpha} and ultraviolet (UV) luminosities, for their LbH{alpha}, consistent with contribution from star formation which dominates the narrow-lines emission, as expected from their positions in the BPT diagrams. (3) The type 1 which reside within the AGN region in the BPT diagrams, are offset to lower [SII]/H{alpha} and [NII]/H{alpha} luminosity ratios, compared to type 2 AGN. This offset is a selection effect, related to the lower AGN/host luminosity selection of the type 2 AGN selected from the SDSS galaxy sample. (4) The [NII]/H{alpha} and [NII]/[SII] ratios in type 1 AGN increase with the host mass, as expected if the mass-metallicity relation of quiescent galaxies holds for the AGN narrow-line region (NLR). (5) The broad lines optical Fe ii is higher for a higher [NII]/H{alpha}, at a fixed Lbol and Eddington ratio L/LEdd. This suggests that the broad line region metallicity is also related to the host mass. (6) The fraction of AGN which are low-ionization nuclear emission-line regions (LINERs) increases sharply with decreasing L/LEdd. This fraction is the same for type 1 and type 2 AGN. (7) The BPT position is unaffected by the amount of dust extinction of the optical-UV continuum, which suggests that the extincting dust resides on scales larger than the narrow-line region (NLR).
- ID:
- ivo://CDS.VizieR/J/A+A/534/A110
- Title:
- Type-2 AGN from XMM-COSMOS bolometric output
- Short Name:
- J/A+A/534/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Study of the multi-wavelength properties of a sample of 255 spectroscopically identified X-ray selected Type-2 AGN from the XMM-COSMOS survey. For each source, X-ray ID, spectroscopic redshift, logarithm of the 2-10keV luminosity, logarithm of the bolometric luminosity, bolometric correction, logarithm of the stellar mass, star formation rate, absolute magnitude M_U_, absolute magnitude M_V_, absolute magnitude M_J_ (Johnson-Kron-Cousin system), morphological class.
- ID:
- ivo://CDS.VizieR/J/ApJ/841/102
- Title:
- Type 2 AGN host galaxies in Chandra-COSMOS
- Short Name:
- J/ApJ/841/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the star formation properties of a large sample of ~2300 X-ray-selected Type 2 Active Galactic Nuclei (AGNs) host galaxies out to z~3 in the Chandra COSMOS Legacy Survey in order to understand the connection between the star formation and nuclear activity. Making use of the existing multi-wavelength photometric data available in the COSMOS field, we perform a multi-component modeling from far-infrared to near-ultraviolet using a nuclear dust torus model, a stellar population model and a starburst model of the spectral energy distributions (SEDs). Through detailed analyses of SEDs, we derive the stellar masses and the star formation rates (SFRs) of Type 2 AGN host galaxies. The stellar mass of our sample is in the range of 9<logM_stellar_/M_{sun}_<12 with uncertainties of ~0.19dex. We find that Type 2 AGN host galaxies have, on average, similar SFRs compared to the normal star-forming galaxies with similar M_stellar_ and redshift ranges, suggesting no significant evidence for enhancement or quenching of star formation. This could be interpreted in a scenario, where the relative massive galaxies have already experienced substantial growth at higher redshift (z>3), and grow slowly through secular fueling processes hosting moderate-luminosity AGNs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/463/24
- Title:
- Type 2 AGNs with double-peaked narrow emission lines
- Short Name:
- J/MNRAS/463/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 1 per cent of redshift z~0.1 active galactic nuclei (AGNs) show velocity splitting of a few hundred km/s in the narrow emission lines in spatially integrated spectra. Such line profiles have been found to arise from the bulk motion of ionized gas clouds associated with galactic-scale outflows, merging pairs of galaxies each harbouring a supermassive black hole (SMBH), and/or galactic-scale disc rotation. It remains unclear, however, how the frequency of narrow-line velocity splitting may depend on AGN luminosity. Here we study the correlation between the fraction of Type 2 AGNs with double-peaked narrow emission lines and AGN luminosity as indicated by [OIII] {lambda}5007 emission-line luminosity L_[OIII]_. We combine the sample of Liu et al. (2010. Cat. J/ApJ/708/427) at z~0.1 with a new sample of 178 Type 2 AGNs with double-peaked [OIII] emission lines at z~0.5. We select the new sample from a parent sample of 2089 Type 2 AGNs from the SDSS-III/Baryon Oscillation Spectroscopic Survey. We find a statistically significant (~4.2{sigma}) correlation between L_[OIII}]_ and the fraction of objects that exhibit double-peaked narrow emission lines among all Type 2 AGNs, corrected for selection bias and incompleteness due to [OIII] line width, equivalent width, splitting velocity, and/or equivalent width ratio between the two velocity components. Our result suggests that galactic-scale outflows and/or merging pairs of SMBHs are more prevalent in more powerful AGNs, although spatially resolved follow-up observations are needed to resolve the origin(s) for the narrow-line velocity splitting for individual AGNs.
- ID:
- ivo://CDS.VizieR/J/ApJ/708/427
- Title:
- Type 2 AGNs with double-peaked [OIII] lines
- Short Name:
- J/ApJ/708/427
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 167 type 2 active galactic nuclei (AGNs) with double-peaked [OIII]4959,5007 narrow emission lines, selected from the Seventh Data Release of the Sloan Digital Sky Survey. The double-peaked profiles can be well modeled by two velocity components, blueshifted and redshifted from the systemic velocity. Half of these objects have a more prominent redshifted component. In cases where the H{beta} emission line is strong, it also shows two velocity components whose line-of-sight (LOS) velocity offsets are consistent with those of [OIII]. The relative LOS velocity offset between the two components is typically a few hundred km/s, larger by a factor of ~1.5 than the line full width at half maximum of each component. The offset correlates with the host stellar velocity dispersion {sigma}_*_. The host galaxies of this sample show systematically larger {sigma}_*_, stellar masses, and concentrations, and older luminosity-weighted mean stellar ages than a regular type 2 AGN sample matched in redshift, [OIII]5007 equivalent width, and luminosity; they show no significant difference in radio properties. These double-peaked features could be due to narrow-line region kinematics, or binary black holes.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/732
- Title:
- Type Ia SN environment within host galaxies
- Short Name:
- J/MNRAS/448/732
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present constraints on Type Ia supernovae (SNe Ia) progenitors through an analysis of the environments found at the explosion sites of 102 events within star-forming host galaxies. H{alpha} and Galaxy Evolution Explorer near-ultraviolet (UV) images are used to trace on-going and recent star formation (SF), while broad-band B, R, J, K imaging is also analysed. Using pixel statistics we find that SNe Ia show the lowest degree of association with H{alpha} emission of all supernova (SN) types. It is also found that they do not trace near-UV emission. As the latter traces SF on time-scales less than 100Myr, this rules out any extreme 'prompt' delay times as the dominant progenitor channel of SNe Ia. SNe Ia best trace the B-band light distribution of their host galaxies. This implies that the population within star-forming galaxies is dominated by relatively young progenitors. Splitting SNe by their (B-V) colours at maximum light, 'redder' events show a higher degree of association with HII regions and are found more centrally within hosts. We discuss possible explanations of this result in terms of line-of-sight extinction and progenitor effects. No evidence for correlations between SN stretch and environment properties is observed.
