- ID:
- ivo://CDS.VizieR/J/ApJ/764/3
- Title:
- H{alpha} indices in M low-mass stars
- Short Name:
- J/ApJ/764/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Through the McDonald Observatory M Dwarf Planet Search, we have acquired nearly 3000 high-resolution spectra of 93 late-type (K5-M5) stars over more than a decade using the High Resolution Spectrograph on the Hobby-Eberly Telescope. This sample provides a unique opportunity to investigate the occurrence of long-term stellar activity cycles for low-mass stars. In this paper, we examine the stellar activity of our targets as reflected in the H{alpha} feature. We have identified periodic signals for six stars, with periods ranging from days to more than 10 years, and find long-term trends for seven others. Stellar cycles with P>=1 year are present for at least 5% of our targets. Additionally, we present an analysis of the time-averaged activity levels of our sample, and search for correlations with other stellar properties. In particular, we find that more massive, earlier type (M0-M2) stars tend to be more active than later type dwarfs. Furthermore, high-metallicity stars tend to be more active at a given stellar mass. We also evaluate H{alpha} variability as a tracer of activity-induced radial velocity (RV) variation. For the M dwarf GJ 1170, H{alpha} variation reveals stellar activity patterns matching those seen in the RVs, mimicking the signal of a giant planet, and we find evidence that the previously identified stellar activity cycle of GJ 581 may be responsible for the recently retracted planet f in that system. In general, though, we find that H{alpha} is not frequently correlated with RV at the precision (typically 6-7m/s) of our measurements.
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- ID:
- ivo://CDS.VizieR/J/AJ/126/1286
- Title:
- H{alpha}+[NII] observations of M81 HII regions
- Short Name:
- J/AJ/126/1286
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a first of a series of studies of the H{alpha}+[NII] emission from nearby spiral galaxies, we present measurements of H{alpha}+[NII] emission from HII regions in M81. Our method uses large-field CCD images and long-slit spectra and is part of the ongoing Beijing-Arizona-Taipei-Connecticut Sky Survey (the BATC survey). The CCD images are taken with the National Astronomical Observatories of China (NAOC) 0.6/0.9m f/3 Schmidt telescope at the Xinglong Observing Station, using a multicolor filter set. The observations reported here were taken on 30 individual nights over the time period 1995 February 5 to 1997 February 19. Spectra of 10 of the brightest HII regions are obtained using the NAOC 2.16m telescope with a Tek 1024x1024 CCD, between 1997 April 9 and 11. The continua of the spectra are calibrated by flux-calibrated images taken from the Schmidt observations. We determine the continuum component of our H{alpha}+[NII] image via interpolation from the more accurately measured backgrounds (M81 starlight) obtained from the two neighboring (in wavelength) BATC filter images. We use the calibrated fluxes of H{alpha}+[NII] emission from the spectra to normalize this interpolated, continuum-subtracted H{alpha}+[NII] image. We estimate the zero-point uncertainty of the measured H{alpha}+[NII] emission flux to be 8%. A catalog of H{alpha}+[NII] fluxes for 456 HII regions is provided, with those fluxes being on a more consistent linear scale than previously available. The logarithmically binned H{alpha}+[NII] luminosity function of HII regions is found to have slope {alpha}=-0.70, consistent with previous results (which allowed {alpha}=-0.5 to -0.8). From the overall H{alpha}+[NII] luminosity of the HII regions, the star formation rate of M81 is found to be ~0.68M_{sun}_/yr, modulo uncertainty with extinction corrections.
- ID:
- ivo://CDS.VizieR/J/A+A/559/A87
- Title:
- H{alpha} observations of LSI+61 303
- Short Name:
- J/A+A/559/A87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report 137 spectral observations of the H{alpha} emission line of the radio- and gamma-ray-emitting Be/X-ray binary LSI+61 303 obtained during the period of September 1998 - January 2013. From measuring various H{alpha} parameters, we found that the orbital modulation of the H{alpha} is best visible in the equivalent width ratio EW(B)/EW(R), the equivalent width of the blue hump, and in the radial velocity of the central dip. The periodogram analysis confirmed that the H{alpha} emission is modulated with the orbital and superorbital periods. For the past 20 years the radius of the circumstellar disk is similar to the Roche lobe size at the periastron. It is probably truncated by a 6:1 resonance. The orbital maximum of the equivalent width of H{alpha} emission peaks after the periastron and coincides on average with the X-ray and gamma-ray maxima.
- ID:
- ivo://CDS.VizieR/J/ApJ/647/128
- Title:
- H{alpha} observations of UV-selected galaxies
- Short Name:
- J/ApJ/647/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using Halpha spectra of 114 rest-frame UV-selected galaxies at z~2, we compare inferred star formation rates (SFRs) with those determined from the UV continuum luminosity. After correcting for extinction using standard techniques based on the UV continuum slope, we find excellent agreement between the indicators, with <SFR_Ha_>=31M_{sun}_/yr and <SFR_UV_>=29M_{sun}_/yr. The agreement between the indicators suggests that the UV luminosity is attenuated by a typical factor of ~4.5 (ranging from no attenuation to a factor of 100 for the most obscured object in the sample), in good agreement with estimates of obscuration from X-ray, radio, and mid-IR data.
- ID:
- ivo://CDS.VizieR/J/ApJS/166/505
- Title:
- H{alpha} photometry of face-on galaxies
- Short Name:
- J/ApJS/166/505
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a survey of the photometric and kinematic properties of 39 nearby, nearly face-on disk galaxies. Our approach exploits echelle-resolution integral-field spectroscopy of the H{alpha} regions, obtained with DensePak on the WIYN 3.5m telescope Bench Spectrograph. These data are complemented by HI line profiles observed with the Nancay radio telescope for 25 of these sample galaxies. Twelve additional line widths are available for sample galaxies from the literature. In this paper, we introduce the goals of this survey, define the sample selection algorithm, and amass the integral field spectroscopic data and HI line widths. We establish spatially integrated H{alpha} line widths for the sample. We test the veracity of these spatially integrated line profiles by convolving narrowband imaging data with velocity field information for one of the sample galaxies, PGC 38268, and also by comparing to HI line profiles.
- ID:
- ivo://CDS.VizieR/J/ApJS/187/228
- Title:
- H{alpha} profiles of Be stars
- Short Name:
- J/ApJS/187/228
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a set of theoretical H{alpha} emission-line profiles of Be stars, created by systematically varying model input parameters over a wide range of accepted values. Models were generated with a non-LTE radiative transfer code that incorporates a non-isothermal disk structure and a solar-type chemical composition. The theoretical H{alpha} emission-line profiles were compared to a large set of Be star spectra with the aim of reproducing their global characteristics. We find that the observed profile shapes cannot be used to uniquely determine the inclination angle of Be star+disk systems. Drastically different profile shapes arise at a given inclination angle as a direct result of the state of the gas, and self-consistent disk physical conditions are therefore crucial for interpreting the observations.
- ID:
- ivo://CDS.VizieR/J/A+A/554/A143
- Title:
- H{alpha} spectra of MWC 342 spectra, 2004-2010
- Short Name:
- J/A+A/554/A143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalogue presents spectra of MWC 342 (V1972 Cyg) obtained during the period 2004 to 2010 with the Coude spectrograph at the 2m telescope in Ondrejov observatory, Czech Republic, using the SITe CCD (2030x800 pixels, 15um pixel size) in a camera with 700mm focus. The spectral interval along the H{alpha} line covers 6265 to 6765{AA}. The resolving power is this range is R~13000. The data reduction was performed using IRAF. After the bias subtraction, flat-field and overscan correction, the dcr program written by Pych (2004PASP..116..148P) was used for the cosmic ray removal. The spectra subtraction was done by IRAF apall task without using the optimal extraction . The background, together with the night sky lines, is eliminated during spectra subtraction by individual pixel columns. The remaining wavelength calibration, heliocentric correction, and the continuum fitting are also performed using IRAF. The heliocentric correction was applied on the data. Chebyshev polynomial of the third order is used for the spectra normalisation to fit the intervals, which apparently contain no spectral lines. Each continuum interval is split into sub-intervals of five pixels, where the median value is taken for the continuum evaluation. Possible remaining cosmic ray hits thus do not affect continuum normalisation.
- ID:
- ivo://CDS.VizieR/J/A+A/560/A30
- Title:
- H{alpha} spectra of {pi} Aqr
- Short Name:
- J/A+A/560/A30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The work is aimed at studying the circumstellar disk of the bright classical binary Be star pi Aqr. We analysed variations of a double-peaked profile of the Halpha emission line in the spectrum of pi Aqr that was observed in many phases during ~40 orbital cycles in 2004-2013. We applied the discrete Fourier transform (DFT) method to search for periodicity in the peak intensity ratio (V/R). Doppler tomography was used to study the structure of the disk around the primary. The dominant frequency in the power spectrum of the Halpha V/R ratio is 0.011873d^-1^, which corresponds to a period of 84.2(2) days and agrees with the earlier determined orbital period of the system P_orb_=84.1d. The V/R shows a sinusoidal variation that is phase-locked with the orbital period. Doppler maps of all our spectra show a non-uniform structure of the disk around the primary: a ring with the inner and outer radii at V_in_~450km/s and V_out_~200km/s, respectively, along with an extended stable region (spot) at V_x_~225km/s and Vy~100km/s. The disk radius of ~65R_{sun}_=0.33AU was estimated by assuming Keplerian motion of a particle on a circular orbit at the disk's outer edge.
- ID:
- ivo://CDS.VizieR/J/ApJ/890/86
- Title:
- H{alpha} spectra & V-band photometry of {delta} Sco
- Short Name:
- J/ApJ/890/86
- Date:
- 04 Dec 2021
- Publisher:
- CDS
- Description:
- We model the circumstellar disk of {delta} Sco using the three-dimensional Monte Carlo radiative transfer code HDUST in order to quantify the large-scale changes in the disk through the years 2000-2018, and to see if these changes can be attributed to the secondary star affecting the disk throughout its orbit. We determine our best-fitting models through matching simulated observations to actual H{alpha} spectroscopy and V-band photometric observations. Our modeling results confirm previous findings that the disk of {delta}Sco was forming early in the century. We also find a period of disk dissipation when the companion is at apastron, as well as a significant growth of the disk between 2009 and 2011, prior to the periastron of 2011. Due to the steady-state nature of the disk after 2011, it is difficult to say whether the variations seen are due to the effect of the close passage of the binary companion.
- ID:
- ivo://CDS.VizieR/J/AJ/143/61
- Title:
- H{alpha} spectroscopy in IC 1396 HII region
- Short Name:
- J/AJ/143/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have made an extensive survey of emission-line stars in the IC 1396 H II region to investigate the low-mass population of pre-main-sequence (PMS) stars. A total of 639 H{alpha} emission-line stars were detected in an area of 4.2deg^2^ and their i' photometry was measured. Their spatial distribution exhibits several aggregates near the elephant trunk globule (Rim A) and bright-rimmed clouds at the edge of the H II region (Rim B and SFO 37, 38, 39, 41), and near HD206267, which is the main exciting star of the HII region. Based on the extinction estimated from the near-infrared color-color diagram, we have selected PMS star candidates associated with IC1396. The age and mass were derived from the extinction-corrected color-magnitude diagram and theoretical PMS tracks. Most of our PMS candidates have ages of <3Myr and masses of 0.2-0.6M_{sun}_. Although it appears that only a few stars were formed in the last 1Myr in the east region of the exciting star, the age difference among subregions in our surveyed area is not clear from the statistical test. Our results may suggest that massive stars were born after the continuous formation of low-mass stars for 10Myr. The birth of the exciting star could be the late stage of slow but contiguous star formation in the natal molecular cloud. It may have triggered the formation of many low-mass stars at the dense inhomogeneity in and around the HII region by a radiation-driven implosion.
