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1.
Results from optical photometric observations of the PMS star V 1735 Cyg are reported. The star is located in the IC 5146
dark cloud complex—a region of active star formation. On the basis of observed outburst and spectral properties, V 1735 Cyg
was classified as a FUor object. We present data from BVRI CCD photometric observations of the star, collected from March 2003 to January 2009. Plates from the Rozhen Schmidt telescope
archive were scanned for a brightness estimation of the star. A sequence of sixteen comparison stars in the field of V 1735
Cyg was calibrated in BVRI bands. The data from photographic observations made from 1986 to 1992 show a strong light variability (ΔV=1⋅m2). In contrast, the recent photometric data obtained from 2003 to 2009 show only small amplitude variations (ΔI=0⋅m3). The analysis of existing photometric data shows a very slow decrease in star brightness—1⋅m8 (R) for a 44 year period. The possibilities for future photometric investigations of V 1735 Cyg using the photographical
plate archives is discussed briefly. 相似文献
2.
Photoelectric observations of the star HD 200925 in the standardUBV system have been secured and analysed. The period is determined to be 0
.
d
267 394. From the period and shape of the light and colour curves, the star HD 200925 appears to be a dwarf cepheid. The physical parameters have been derived. The mass derived for this star is found to agree well with the value inferred from the evolutionary tracks. The star appears to be a post-Main Sequence star in the hydrogen shell burning stage of evolution. The spectral class, for this star, is assigned to be F2 III. 相似文献
3.
The Square Kilometer Array (SKA) will enable studies of star formation in nearby galaxies with a level of detail never before possible outside of the Milky Way. Because the earliest stages of stellar evolution are often inaccessible at optical and near-infrared wavelengths, high spatial resolution radio observations are necessary to explore extragalactic star formation. The SKA will have the sensitivity to detect individual ultracompact HII regions out to the distance of nearly 50 Mpc, allowing us to study their spatial distributions, morphologies, and populations statistics in a wide range of environments. Radio observations of Wolf-Rayet stars outside of the Milky Way will also be possible for the first time, greatly expanding the range of conditions in which their mass loss rates can be determined from free-free emission. On a vastly larger scale, natal of super star clusters will be accessible to the SKA out to redshifts of nearly z 0.1. The unprecedented sensitivity of radio observations with the SKA will also place tight constraints on the star formation rates as low as 1M yr−1 in galaxies out to a redshift of z 1 by directly measuring the thermal radio flux density without assumptions about a galaxy’s magnetic field strength, cosmic ray production rate, or extinction. 相似文献
4.
We report the results of spectropolarimetric observations of the supergiant ζ Ori A made with 6-m BTA telescope of the SAO RAS. We found regular variations of line profiles in the spectrum of the star
with a period of 1–3 hours and point to their possible association with nonradial photospheric pulsations. We also searched
for a possible weak magnetic field in ζ Ori A, but observations did not confirm the existence of such a field in the star considered. 相似文献
5.
τ Bootis is a late F‐type main sequence star orbited by a Hot Jupiter. During the last years spectropolarimetric observations led to the hypothesis that this star may host a global magnetic field that switches its polarity once per year, indicating a very short activity cycle of only one year duration. In our ongoing observational campaign, we have collected several X‐ray observations with XMM‐Newton and optical spectra with TRES/FLWO in Arizona to characterize τ Boo's corona and chromosphere over the course of the supposed one‐year cycle. Contrary to the spectropolarimetric reconstructions, our observations do not show indications for a short activity cycle (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
6.
We present Strömgrenuvby photometric observations and a series of radial velocities obtained with the Coravel scanner for the 11th magnitude star catalogued in the Guide Star Catalogue as GSC 0114401023. This star was serendipitously identified on UV frames taken with the Very-Wide-Field-Camera aboard Spacelab-1. Radial velocities show the star to be binary and we have determined accurate orbital elements. Photometric data and orbital elements are consistent with the system being a previously-unrecognized eclipsing binary, with period = 33.8766 days and eccentricity = 0.262.Based on observations collected at the Observatoire de Haute Provence (OHP), CNRS, Saint-Michel l'Observatoire, France, and at the European Southern Observatory (ESO), La Silla, Chile. 相似文献
7.
Photoelectric UBVR observations of the young irregular variable star V586 Ori are presented and discussed. 相似文献
8.
C. L. Carilli F. Walter R. Wang A. Wootten K. Menten F. Bertoldi E. Schinnerer P. Cox A. Beelen A. Omont 《Astrophysics and Space Science》2008,313(1-3):307-311
We discuss observations of the first galaxies, within cosmic reionization, at centimeter and millimeter wavelengths. We present
a summary of current observations of the host galaxies of the most distant QSOs (z∼6). These observations reveal the gas, dust, and star formation in the host galaxies on kpc-scales. These data imply an enriched
ISM in the QSO host galaxies within 1 Gyr of the big bang, and are consistent with models of coeval supermassive black hole
and spheroidal galaxy formation in major mergers at high redshift. Current instruments are limited to studying truly pathologic
objects at these redshifts, meaning hyper-luminous infrared galaxies (L
FIR
∼1013
L
⊙). ALMA will provide the one to two orders of magnitude improvement in millimeter astronomy required to study normal star
forming galaxies (i.e. Ly-α emitters) at z∼6. ALMA will reveal, at sub-kpc spatial resolution, the thermal gas and dust—the fundamental fuel for star formation—in galaxies
into cosmic reionization. 相似文献
9.
L. Christensen 《Astronomische Nachrichten》2011,332(3):301-306
In the last couple of decades hundreds of studies have explored the nature of star‐forming galaxies at different redshifts. This contribution focuses on X‐shooter observations of star‐burst galaxies at 0 < z < 6 from commissioning runs, science verification, and regular observations, and demonstrates the capability of the new instrument in this competitive field. Observations of gravitationally lensed galaxies show that X‐shooter has no limitation in the redshift desert (1.4 < z < 2) where the strong optical emission lines are shifted to the near‐IR region. Physical properties of galaxies, such as masses, metallicities, abundance ratios, and star formation rates can be derived from observations with relatively short integration times for faint galaxies. The simultaneous UV to near‐IR spectral coverage makes derivation of physical quantities more reliable because there are no differential slit losses as may occur when observations from different optical and near‐IR instruments are used. Over the entire redshift range, spectra of faint galaxies will allow us to better measure stellar ages and dominating ionisation sources compared to broad band spectral energy distribution measurements (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
10.
We have identified three possible ways in which future XMM‐Newton observations can provide significant constraints on the equation of state of neutron stars. First, using a long observation of the neutron star X‐ray transient Cen X‐4 in quiescence one can use the RGS spectrum to constrain the interstellar extinction to the source. This removes this parameter from the X‐ray spectral fitting of the pn and MOS spectra and allows us to investigate whether the variability observed in the quiescent X‐ray spectrum of this source is due to variations in the soft thermal spectral component or variations in the power law spectral component coupled with variations in NH. This will test whether the soft thermal spectral component can indeed be due to the hot thermal glow of the neutron star. Potentially such an observation could also reveal redshifted spectral lines from the neutron star surface. Second, XMM‐Newton observations of radius expansion type I Xray bursts might reveal redshifted absorption lines from the surface of the neutron star. Third, XMM‐Newton observations of eclipsing quiescent low‐mass X‐ray binaries provide the eclipse duration. With this the system inclination can be determined accurately. The inclination determined from the X‐ray eclipse duration in quiescence, the rotational velocity of the companion star and the semi‐amplitude of the radial velocity curve determined through optical spectroscopy, yield the neutron star mass. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
11.
IUE observations of the hydrogen-deficient irregular variable star MV Sgr obtained in 1980 June-October and also in 1979 November
are discussed. These observations show a prominent λ 2200 absorption feature. A value ofE(B — V) = 0.55 is deduced from the strength of λ 2200 band assuming that this absorption is caused by interstellar medium. The dereddened
continuum obtained at different times can be fitted to a theoretical energy distribution of a helium star model with Teff = 18000 K and log g = 2.5, similar to that of BD + 10‡ 2179. This theoretical energy distribution, after applying interstellar extinction, givesV = 12.7 mag, agreeing with the observed visual magnitude of ≃ 13 in 1979 November and 1980 June-October. Even though there
was no change in the continuum flux, the ultraviolet line-spectrum shows variations. The IUE spectra of 1980 October show
enhanced (circumstellar) absorption lines of Fe II, Si II, O I, C I and others along with the absorption lines of a B star.
In view of the similarity of the spectroscopic phenomena of MV Sgr with that of α Sco system, a model is proposed in which
a cool companion star, surrounded by dust, occasionally blows gas towards the hotter hydrogen-poor B star. This model explains
the irregular light variations and the spectroscopic phenomena.
Based on observations obtained with IUE satellite at the Villafranca Satellite Tracking Station of the European Space Agency. 相似文献
12.
Gerhard F. O. Schnur 《Astronomische Nachrichten》1977,298(3):167-169
Photoelectric UBV observations of 69 stars, distributed in two sequences north and south of the galactic star cluster NGC 5823, are reported. 相似文献
13.
Photometric observations of the Ap star HD 193722 give unambiguous proofs for a rotational period of P=8.5297 days in contradiction to the earlier found value of P=1.13316 days. Spectroscopic measurements yield a line width equivalent to the value v sin i=44.5 km/s. Both findings show convincingly that HD 193722 is an evolved Ap star with a position in the giant region of the HR diagram. This place falls into a domain occupied by the hypothetic Maia sequence. 相似文献
14.
V. P. Arkhipova V. G. Klochkova E. L. Chentsov V. F. Esipov N. P. Ikonnikova G. V. Komissarova 《Astronomy Letters》2006,32(10):661-670
We present the results of spectroscopic and photometric observations for the B star StHα62 with an IR excess, a post-AGB candidate identified with the IR source IRAS 07171+1823. High-resolution spectroscopy has allowed the λ4330–7340 Å spectrum of the star to be identified: it contains absorption lines of an early B star and emission lines of a gaseous shell. The residual line intensities have been measured. The heliocentric radial velocities measured from absorption lines of the star and emission lines of the shell are 〈V r 〉 = +45 ± 1 and +52 ± 1 km s?1, respectively. The line-of-sight velocities of gas-dust clouds determined from the interstellar Na I lines are 12 and 33 km s?1. The He I λ5876 Å line exhibits a P Cyg profile, which is indicative of an ongoing mass loss by the star. The expansion velocity of the outer shell estimated from forbidden lines is 12–13 km s?1. Quantitative classification gives the spectral type B0.51 for the star. The parameters of the gaseous shell have been determined: N e = 3.1 × 103 cm?3 and T e ～ 21 000 K. Over 4 years of its observations, the star showed rapid irregular light variations with the amplitudes ΔV = We present the results of spectroscopic and photometric observations for the B star StHα62 with an IR excess, a post-AGB candidate
identified with the IR source IRAS 07171+1823. High-resolution spectroscopy has allowed the λ4330–7340 ? spectrum of the star
to be identified: it contains absorption lines of an early B star and emission lines of a gaseous shell. The residual line
intensities have been measured. The heliocentric radial velocities measured from absorption lines of the star and emission
lines of the shell are 〈V
r
〉 = +45 ± 1 and +52 ± 1 km s−1, respectively. The line-of-sight velocities of gas-dust clouds determined from the interstellar Na I lines are 12 and 33
km s−1. The He I λ5876 ? line exhibits a P Cyg profile, which is indicative of an ongoing mass loss by the star. The expansion velocity
of the outer shell estimated from forbidden lines is 12–13 km s−1. Quantitative classification gives the spectral type B0.51 for the star. The parameters of the gaseous shell have been determined:
N
e
= 3.1 × 103 cm−3 and T
e
∼ 21 000 K. Over 4 years of its observations, the star showed rapid irregular light variations with the amplitudes ΔV =
, ΔB =
, and ΔU =
and no color-magnitude correlation. We estimate the total extinction for the star from our photometric observations as A
v
=
. Near-IR observations have revealed dust radiation with a temperature of ∼1300 K. We estimate the distance to StHα62 to be
r = 5.2 ± 1.2 kpc by assuming that the star is a low-mass (M = 0.55 ± 0.05 M
⊙) protoplanetary nebula.
Original Russian Text ? V.P. Arkhipova, V.G. Klochkova, E.L. Chentsov, V.F. Esipov, N.P. Ikonnikova, G.V. Komissarova, 2006,
published in Pis’ma v Astronomicheskiĭ Zhurnal, 2006, Vol. 32, No. 10, pp. 737–747. 相似文献
15.
M. A. Eritsian 《Astrophysics》2001,44(4):449-453
The results of photometric and polarimetric observations of the star CH Cygni in the B, V, and R filters are presented. Variations of brightness and color indices are given as functions of the time of observation. A fairly irregular character was found, both in the brightness variations and in the variations of color indices. The polarization observations showed that the light of CH Cygni is intrinsically polarized. 相似文献
16.
The detection of near‐infrared (NIR) excess at the position of a star can indicate either a substellar companion or a disk around the respective star. In this work we probed whether a 2.5σ H ‐band flux enhancement at the position of the isolated neutron star RX J0806.4–4123 can be confirmed at another NIR wavelength. We observed RXJ0806.4–4123 in the J ‐band with Gemini South equipped with FLAMINGOS‐2. There was no significant detection of a J ‐band source at the neutron star position. However, similarly to the H ‐band we found a very faint (1.4σ) flux enhancement with a nominal magnitude of J = 24.8 ± 0.5. The overall NIR‐detection significance is 3.1σ. If real, this emission is too bright to come from the neutron star alone. Deeper near‐infrared observations are necessary to confirm or refute the potential NIR excess. The confirmation of such NIR excess could imply that there is a substellar companion or a disk around RXJ0806.4–4123. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
17.
We present a one-zone model of star formation in elliptical galaxies that includes thermal feedback from supernovae and a
temperature dependent star formation efficiency. The modulation of feedback with the total mass results in the triggering
of late episodes of star formation in low-mass galaxies. These small `bursts' can occur as late as at redshifts z ∼ 0.5 but they do not change significantly the optical and NIR color-magnitude relation (CMR) of cluster galaxies, both locally
and out to moderate redshifts, in agreement with the observations. However, they introduce a large scatter at the faint end
of the NUV-Optical CMR, as recently found in cluster Abell 851 (z = 0.41).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
We review the classification of the variable star SW Equulei, formerly classified as a close binary of the W UMa type with a period of 0.83632 d and components of spectral types O–A or F–G and later. New observations indicate that the light curve is not that of an eclipsing binary but of a pulsating star with a period half of the old value. Further examination shows that SW Equulei is a double mode star of the RRd Lyrae type with a fundamental period of P = 0.560727 d and an overtone of P = 0.4181777 d at a distance of ≈ 7.1 kpc. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
19.
M. C. Weisskopf M. Karovska G. G. Pavlov V. E. Zavlin T. Clarke 《Astrophysics and Space Science》2007,308(1-4):151-160
We present an overview of Chandra X-ray Observatory observations of neutron stars. The outstanding spatial and spectral resolution of this great observatory
have allowed for observations of unprecedented clarity and accuracy. Many of these observations have provided new insights
into neutron star physics. We present an admittedly biased and overly brief review of these observations, highlighting some
new discoveries made possible by the Observatory’s unique capabilities. This includes our analysis of recent multiwavelength
observations of the putative pulsar and its pulsar-wind nebula in the IC443 SNR.
相似文献
20.
Jay A. Frogel 《Astrophysics and Space Science》1999,265(1-4):303-309
Observations of the stellar content of the bulge of the Milky Way can provide critical guidelines for the interpretation of
observations of distant galaxies, in particular for understanding their stellar content and evolution. In this brief overview
I will first highlight some recent work directed towards measuring the history of star formation and the chemical composition
of the central few parsecs of the Galaxy. These observations point to an episodic history of star formation in the central
region with several bursts having occurred over the past few 100 Myr (e.g. Blum et al., 1996b). High resolution spectroscopic observations by Ramírez et al. (1998) of luminous M stars in this region yield a near solar value for [Fe/H] from direct measurements of iron lines. Then
I will present some results from an ongoing program by my colleagues and myself the objective of which is the delineation
of the star formation and chemical enrichment histories of the central 100 parsecs of the Galaxy, the `inner bulge'. From
new photometric data we have concluded that there is a small increase in mean [Fe/H] from Baade's Window to the Galactic Center
and deduce a near solar value for stars in the central region. For radial distances greater than 1° from the Galactic Center we fail to find a measurable population of stars that are significantly younger than those in Baade's
Window. Within 1° we find a number of luminous M giants that most likely are the result of a star formation episode not more than one or two
Gyr ago.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献