Chi Persei Research Articles

RED SUPERGIANT STARS AS COSMIC ABUNDANCE PROBES. III. NLTE EFFECTS IN J-BAND MAGNESIUM LINES

Non-LTE calculations for Mg I in red supergiant stellar atmospheres are presented to investigate the importance of non-LTE for the formation of Mg I lines in the NIR J-band. Recent work using medium resolution spectroscopy of atomic lines in the J-band of individual red supergiant stars has demonstrated that technique is a very promising tool to investigate the chemical composition of the young stellar population in star forming galaxies. As in previous work, where non-LTE effects were studied for iron, titanium and silicon, substantial effects are found resulting in significantly stronger Mg I absorption lines. For the quantitative spectral analysis the non-LTE effects lead to magnesium abundances significantly smaller than in LTE with the non-LTE abundance corrections varying smoothly between -0.4 dex and -0.1 dex for effective temperatures between 3400 K and 4400 K. We discuss the physical reasons of the non-LTE effects and the consequences for extragalactic J-band abundance studies using individual red supergiants in the young massive galactic double cluster h and chi Persei.

QUANTITATIVE SPECTROSCOPICJ-BAND STUDY OF RED SUPERGIANTS IN PERSEUS OB-1

We demonstrate how the metallicities of red supergiant (RSG) stars can be measured from quantitative spectroscopy down to resolutions of ~3000 in the J-band. We have obtained high resolution spectra on a sample of the RSG population of h and chi Persei, a double cluster in the solar neighborhood. We show that careful application of the MARCS model atmospheres returns measurements of Z consistent with solar metallicity. Using two grids of synthetic spectra--one in pure LTE and one with NLTE calculations for the most important diagnostic lines--we measure Z = +0.04 +/- 0.10 (LTE) and Z = -0.04 +/- 0.08 (NLTE) for the sample of eleven RSGs in the cluster. We degrade the spectral resolution of our observations and find that those values remain consistent down to resolutions of less than R of 3000. Using measurements of effective temperatures we compare our results with stellar evolution theory and find good agreement. We construct a synthetic cluster spectrum and find that analyzing this composite spectrum with single-star RSG models returns an accurate metallicity. We conclude that the RSGs make ideal targets in the near infrared for measuring the metallicities of star forming galaxies out to 7-10 Mpc and up to ten times farther by observing the integrated light of unresolved super star clusters.

PHYSICAL PROPERTIES OF THE B AND Be STAR POPULATIONS OFhAND χ PERSEI

We present a study of the B and Be star populations of the Double Cluster h and chi Persei. Blue optical spectroscopy is used to first measure projected rotational velocity, V sin i, effective surface temperature, T_eff, and surface gravity, log g, for B-type sample stars, while available Stromgren photometry is used to calculate T_eff and log g for the Be stars showing emission. In our sample of 104 objects for which we measured these stellar parameters, 28 are known or proposed Be stars. Of these Be stars, 22 show evidence of emission at the times of our observations, and furthermore, we find evidence in our data and the literature for at least 8 transient Be stars in the clusters. We find that the Be stars are not rotating near their critical velocity, contrary to the results of studies of similar open clusters. We compare the results of our analysis with other previous studies, and find that the cluster members are more evolved than found by Huang & Gies but still retain much of their initial rotational angular momentum.

SpitzerIRAC andJHKsObservations of h and χ Persei: Constraints on Protoplanetary Disk and Massive Cluster Evolution at ∼107Years

We describe IRAC 3.6-8 mu_m observations and ground-based near-IR JHKs photometry from Mimir and 2MASS of the massive double cluster h & chi Persei complete to J=15.5 (M ~ 1.3 Msun. Within 25' of the cluster centers we detect \~11,000 sources with J < 15.5, ~7,000 sources with [4.5] < 15, and ~ 5000 sources with [8] < 14.5. In both clusters, the surface density profiles derived from the 2MASS data decline with distance from the cluster centers as expected for a bound cluster. Within 15' of the cluster centers, ~ 50% of the stars lie on a reddened ~ 13 Myr isochrone; at 15'-25' from the cluster centers, ~ 40% lie on this isochrone. Thus, the optical/2MASS color-magnitude diagrams indicate that h & chi Per are accompanied by a halo population with roughly the same age and distance as the two dense clusters. The double cluster lacks any clear IR excess sources for J < 13.5 (~ 2.7 Msun). Therefore, disks around high-mass stars disperse prior to ~ 10^{7} yr. At least 2-3% of the fainter cluster stars have strong IR excess at both [5.8] and [8]. About 4-8% of sources slightly more massive than the Sun (~ 1.4 Msun) have IR excesses at [8]. Combined with the lack of detectable excesses for brighter stars, this result suggests that disks around lower-mass stars have longer lifetimes. The IR excess population also appears to be larger at longer IRAC bands ([5.8], [8]) than at shorter IRAC/2MASS bands ($K_{s}$, [4.5]), a result consistent with an inside-out clearing of disks.

Eclipsing binaries in open clusters – III. V621 Per in χ Persei

V621 Persei is a detached eclipsing binary in the open cluster chi Persei which is composed of an early B-type giant star and a main sequence secondary component. From high-resolution spectroscopic observations and radial velocities from the literature, we determine the orbital period to be 25.5 days and the primary velocity semiamplitude to be K = 64.5 +/- 0.4 km/s. No trace of the secondary star has been found in the spectrum. We solve the discovery light curves of this totally-eclipsing binary and find that the surface gravity of the secondary star is log(g_B) = 4.244 +/- 0.054 (cm/s). We compare the absolute masses and radii of the two stars in the mass--radius diagram, for different possible values of the primary surface gravity, to the predictions of stellar models. We find that log(g_A) is approximately 3.55, in agreement with values found from fitting Balmer lines with synthetic profiles. The expected masses of the two stars are 12 Msun and 6 Msun, and the expected radii are 10 Rsun and 3 Rsun. The primary component is near the blue loop stage in its evolution.

A NEW SPECKLE INTERFEROMETRY SYSTEM FOR THE MAMA DETECTOR

ABSTRACT We have developed a new system for making speckle observations with the Multi-Anode Michrochannel Array (MAMA) detector. This system is a true photon counting imaging device which records the arrival time of every detected photon and allows for reconstruction of image features near the diffraction limit of the telescope. We present a description of the system and summary of observational results obtained at the Lick Observatory 1-m reflector in September of 1991. The diffraction limit of the 1-m telescope at 5029 angstroms is about 0.125 arsec and we have successfully resolved the catalogued interferometric binary HD 202582 with a separation of 0.157 ± 0.031 arcsec. A pair of stars in the open cluster Chi Persei separated by 2.65 ± 0.22 arcsec with approximate V magnitudes 8.6 and 11.5 has also been successfully analyzed with the speckle technique.

2000 � UV imaging of A 6� diameter field around theh and Chi Persei double cluster

The stellar field centred close to theh and χ Per double cluster is one of the 123 fields recorded in the galactic plane at 2000 A by the balloon-borne stratospheric gondola of the SCAP-2000 programme. The analysis of the frame allows us to determine an ultraviolet colour indexU 1-V for more than 600 stars. Among these are stars belonging to theh and χ Per and Tr 2 clusters and to the PER OB1 association. The prevailing extinction law is found to produce greater extinction at 1965 A than predicted by the mean extinction law. Moreover, the clouds responsible for the extinction are situated in the local arm and distributed in two layers with a very transparent interval. The comparison of theA v extinction and theHI and CO abundances leads us to assume the presence of a H2 cloud in front ofh and χ Per, in the second absorbing layer and, therefore, in the local arm. The two absorbing layers and the molecular cloud are perhaps in the plane of the Gould belt and associated with the expanding gas detected by Lindblad. A group of hot stars centred at the same distance as this molecular cloud has been detected and could form an association of OB stars in the local arm. Other, much more distant OB stars belonging to the Perseus arm of Efremov's list. Several stars which must have a very hot companion are detected in the field.

Extreme Be stars in the Magellanic Clouds

view Abstract Citations (23) References (31) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Extreme Be stars in the Magellanic Clouds. Garmany, C. D. ; Humphreys, R. M. Abstract In the course of a spectroscopic investigation of the O-type stars in the Magellanic Clouds, a population of luminous Be stars was serendipitously encountered. They are here referred to as extreme Be stars, following the terminology used by Schild (1966) for a population of Be stars in the region of h and Chi Persei which lie significantly above the main sequence. As members of the Clouds, their luminosities and intrinsic colors can be determined directly. A comparison of these new high-luminosity Be stars with known H-beta-emission-line supergiants in the Clouds is made in both the optical and UV spectral regions. The Galactic counterparts of these Be stars are also discussed. Although these Be stars are an average of several magnitudes brighter than those in the Galaxy, this may in part be a selection effect. Publication: The Astronomical Journal Pub Date: October 1985 DOI: 10.1086/113906 Bibcode: 1985AJ.....90.2009G Keywords: B Stars; Magellanic Clouds; O Stars; Stellar Luminosity; Variable Stars; Astronomical Spectroscopy; Emission; Line Spectra; Astrophysics full text sources ADS | data products SIMBAD (52) NED (1)

The open star clusters of M31 and its spiral structure

view Abstract Citations (59) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The open star clusters of M31 and its spiral structure. Hodge, P. W. Abstract This paper examines the properties of the 403 open star clusters in M31, most of which are small young objects similar to the Pleiades and h and Chi Persei. Their mean diameter is 20 pc. A crude age function for the younger stars is derived from the brightest stars; it differs from that of the LMC in the sense of a relative paucity of the very youngest clusters. The distribution of the young open clusters within M31 closely resembles the distribution of H I; there is a strong concentration of clusters to intermediate distances. An interesting difference in the distribution of young clusters and young stars, on the one hand, and the general intensity in the disk, on the other, is pointed out and briefly discussed. A comparison of the open clusters' positions with various spiral-arm patterns favors a gravitationally distorted two-armed trailing model. Publication: The Astronomical Journal Pub Date: June 1979 DOI: 10.1086/112476 Bibcode: 1979AJ.....84..744H Keywords: Andromeda Galaxy; Astronomical Maps; Galactic Structure; Open Clusters; Hydrogen Clouds; Pleiades Cluster; Star Distribution; Stellar Evolution; Stellar Magnitude; Astrophysics; Andromeda Nebula:Open Clusters; Andromeda Nebula:Spiral Structure full text sources ADS | data products NED (11)

Energy distributions of Be stars in clusters

view Abstract Citations (66) References (10) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Energy distribution of Be stars in clusters. Schild, R. E. Abstract Continuum energy distributions of Be stars are studied on the basis of photoelectric photometry of all known Be stars in 14 clusters and at least two normal B stars in each cluster. Reddening corrections are reviewed, H-alpha emission line strengths are measured photoelectrically and compared with previous photographic data, and the Balmer jumps measured on the dereddened energy distributions are examined. Intrinsic color excesses in the Be stars are evaluated, and polarization data for the h and Chi Persei clusters are analyzed. Evidence of variability in UBV for certain B stars is noted. It is found that: (1) some Be stars have a component of color excess or reddening that is intrinsic to the star itself and may be circumstellar in origin; (2) many Be stars have a component of (B-V) color excess due to the near-IR continuum excess that peaks near 1 micron; (3) the Be stars in the h and Chi Persei clusters can be identified by their intrinsic polarization; (4) the Balmer jumps in many early-type Be stars are typically smaller than in normal stars and sometimes appear to be in emission; (5) some Balmer jumps among middle to late Be stars are larger than normal; and (6) the amount of filling-in of the Balmer jump is poorly correlated with H-alpha emission line strength. Publication: The Astrophysical Journal Supplement Series Pub Date: May 1978 DOI: 10.1086/190519 Bibcode: 1978ApJS...37...77S Keywords: B Stars; Spectral Energy Distribution; Star Clusters; Stellar Spectrophotometry; Balmer Series; H Alpha Line; Tables (Data); Ubv Spectra; Astrophysics; Be Stars:Open Clusters; Be Stars:Spectrophotometry full text sources ADS | data products SIMBAD (44)

Supergiant binaries in the h+chi Per association.

view Abstract Citations (11) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Supergiant binaries in the h and chi Persei association. Abt, H. A. ; Levy, S. G. Abstract A study of 23 supergiants in Per OB1 showed the existence of three spectroscopic binaries for which orbital elements are derived and three possible additional binaries. The resultant binary frequency of at least 15 percent is similar to that of field supergiants and Cepheids. No binaries with periods less than 32 days in length were found, implying that the known supergiant X-ray sources of much shorter periods are probably rarely found systems. Subject headings: associations - binaries - luminous stars Publication: The Astrophysical Journal Pub Date: August 1973 DOI: 10.1086/152314 Bibcode: 1973ApJ...184..167A full text sources ADS | data products SIMBAD (33)

Red Supergiants and Neutrino Emission

Investigation of the variation with stellar mass of the ratio of the numbers of blue and red supergiants. Statistical data for supergiants in young open clusters and subgroups of associations are collected to supplement a more restricted list presented earlier. Improved methods are used to identify hydrogen-burning supergiants, as well as faint supergiant remnants of binary mass exchange, and to arrange the bright evolved supergiants in order of their masses. Neither of these two operations requires knowledge of stellar distances or luminosities. Relevant published work on stellar evolution, rotation, mass loss, and duplicity is used to predict upper and lower limits on the blue-to-red ratio. It is concluded that the observed paucity of very massive red supergiants (and of carbon stars) confirms and extends the trend previously observed, and thereby supports the idea of neutrino-induced acceleration of the carbon burning and later phases of evolution; the h and chi Persei association shows the same dependence of the blue-to-red-ratio on stellar mass as do other clusters and associations; and a moderate decrease of the blue-to-red ratio is observed with increasing galactocentric distance in the Galaxy (as in M33) and seems to be due to a relative scarcity of extremely young stars in distant galactic regions.

Spectral classification in H and chi Persei

Spectral classification in H and chi Persei

Emission line stars near H and chi Persei.

view Abstract Citations (8) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Emission line stars near H and chi Persei. Bidelman, William P. Abstract A plot of the known non-supergiant emission- line stars in the region of the double cluster in Perseus shows that there is a much more pronounced grouping of these objects about the cluster x Persei than about the other cluster. In view of the apparent similarity in constitution of the two clusters, this result is of considerable interest. The average absolute magnitude of these emission-line stars may be estimated at about -3.5, if it is assumed that they are associated with the double cluster; their spectral types, as far as known, range from Bo to B3. Two previously unrecognized Hα emission stars of early type have been found on an~objective prism plate of the h and x Persei region taken with the Schmidt-type reflector of the Warner and Swasey Observatory. This plate was made available to the writer through the kindness of the director of that observatory, Dr. J. J. Xassau. These new Be stars are BD +560612 and star number 2566 in Oosterhoff's monograph on the double cluster in Perseus. Yerkes Observatory, Williams Bay, Wis. Publication: The Astronomical Journal Pub Date: 1947 DOI: 10.1086/106002 Bibcode: 1947AJ.....52Q.121B full text sources ADS |

A group of stars of common motion in the Herschel and chi Persei cluster

A group of stars of common motion in the Herschel and chi Persei cluster