scholarly journals Is there a signature of ice in the IRAS LRS spectra of some Mira variables?

1987 ◽  
Vol 122 ◽  
pp. 221-222
Author(s):  
M. S. Vardya
Keyword(s):  
Emission Feature ◽  
Mira Variables ◽  
Broad Emission ◽  
New Feature

Some M Miras show the 9.7 and 20μm silicate emission. Recently, Vardya, de Jong & Willems (1986; hereafter VDJW) discovered using IRAS LRS spectra a weak broad emission feature ~12μm; this new feature may be silicate (VDJW). Here we investigate whether this can be due to H2O ice.

scholarly journals AKARI IRC survey of the Large Magellanic Cloud: A new feature in the infrared color—magnitude diagram

2008 ◽  
Vol 4 (S256) ◽  
pp. 9-13
Author(s):  
Yoshifusa Ita ◽  
Takashi Onaka ◽  
Daisuke Kato ◽  
Keyword(s):  
Infrared Camera ◽  
Large Magellanic Cloud ◽  
Emission Feature ◽  
Magellanic Cloud ◽  
Circumstellar Dust ◽  
Red Giants ◽  
Broad Emission ◽  
Magnitude Diagram ◽  
Red Giant ◽  
New Feature

AbstractWe observed an area of 10 deg2 of the Large Magellanic Cloud using the Infrared Camera on board AKARI. The observations were carried out using five imaging filters (3, 7, 11, 15, and 24 μm) and a dispersion prism (2 − 5 μm, λ/Δλ ~ 20) equipped in the IRC. The 11 and 15 μm data, which are unique to AKARI IRC, allow us to construct color-magnitude diagrams that are useful to identify stars with circumstellar dust. We found a new sequence in the color-magnitude diagram, which is attributed to red giants with luminosity fainter than that of the tip of the first red giant branch. We suggest that this sequence is likely to be related to the broad emission feature of aluminium oxide at 11.5 μm.

scholarly journals Unidentified emission features in the R Coronae Borealis star V854 Centauri

2018 ◽  
Vol 610 ◽  
pp. L6 ◽  
Author(s):  
L. C. Oostrum ◽  
B. B. Ochsendorf ◽  
L. Kaper ◽  
A. G. G. M. Tielens
Keyword(s):  
Near Infrared ◽  
Physical Nature ◽  
The Other ◽  
Large Telescope ◽  
Circumstellar Material ◽  
Spatially Resolved ◽  
Broad Emission ◽  
Very Large Telescope ◽  
New Feature ◽  
Molecular Nature

During its 2012 decline, the R Coronae Borealis star (RCB) V854 Cen was spectroscopically monitored with X-shooter on the ESO Very Large Telescope. The obscured optical and near-infrared spectrum exhibits many narrow and several broad emission features, as previously observed. The envelope is spatially resolved along the slit and allows for a detailed study of the circumstellar material. In this Letter, we report on the properties of a number of unidentified visual emission features (UFs), including the detection of a new feature at 8692 Å. These UFs have been observed in the Red Rectangle (RR), but their chemical and physical nature is still a mystery. The previously known UFs behave similarly in the RR and in V854 Cen, but are not detected in six other observed RCBs. Some hydrogen might be required for the formation of their carrier(s). The λ8692 UF is present in all RCBs. Its carrier is likely of a carbonaceous molecular nature, presumably different from that of the other UFs.

scholarly journals Metal Abundances and Ionization in QSO Broad Emission-Line Regions

1997 ◽  
Vol 159 ◽  
pp. 96-103 ◽  
Author(s):  
F. Hamann ◽  
J.C. Shields ◽  
R. D. Cohen ◽  
V.T. Junkkarinen ◽  
E.M. Burbidge
Keyword(s):  
Big Bang ◽  
Emission Feature ◽  
Host Galaxies ◽  
Baldwin Effect ◽  
Unusual Behavior ◽  
X Ray ◽  
Continuum Source ◽  
Broad Emission ◽  
Solar Abundances ◽  
Metal Abundances

AbstractWe describe two ongoing studies of QSO broad emissionline regions (BELRs). The first employs the N V λ1240/He II λ1640 and N V/C IV λ1549 line ratios as diagnostics of QSO metallicities. Hamann & Ferland and Ferland et al. showed that many observed N V ratios require enhanced N abundances and Z > Z⊙. Here we present new measurements of large line ratios at redshifts z > 4, which indicate super-solar abundances within ~1 Gyr of the Big Bang (for q0 ≈ 0.5). We also note that the N V line is relatively stronger in more luminous QSOs, in contrast to the well-known Baldwin effect in Lyα, C IV, and O VI λ1034. This unusual behavior in N V could be due to a luminosity-metallicity correlation among QSOs that is coupled to a mass-metallicity relation in their host galaxies.Our second study involves Ne VIII λ774 as a probe of highly ionized gas. We show that a broad emission feature near 774 Å is common in QSOs. Photoionization models indicate that Ne VIII is the most likely identification for this feature. The models also indicate that the Ne VIII emitting gas covers > 40% of the continuum source, has a total hydrogen column density of NH > 1022 cm−2 (for solar abundances) and an ionization parameter of U > 5 (for a nominal QSO continuum shape). This gas would be an X-ray “warm73x201D; absorber — with O VII–O VIII bound-free edges — if it lies along our line-of-sight to the X-ray continuum source.

Mid-IR spectra of the M-type Mira variable R Tri observed with the Spitzer IRS

2020 ◽  
Vol 493 (1) ◽  
pp. 807-814
Author(s):  
Dana K Baylis-Aguirre ◽  
M J Creech-Eakman ◽  
Tina Güth
Keyword(s):  
Ir Spectra ◽  
Emission Feature ◽  
Absorption Feature ◽  
Cool Temperature ◽  
Circumstellar Envelopes ◽  
Mira Variables ◽  
Mira Variable ◽  
Molecular Lines ◽  
Infrared Spectrometer ◽  
Vibrational Bands

ABSTRACT We present analysis of mid-infrared (IR) spectra of the oxygen-rich Mira variable R Tri. The data were taken with the Spitzer Infrared Spectrometer (IRS) as part of a study tracking how Mira variables’ regular pulsations affect circumstellar envelopes. We detected strong emission lines at 13.87, 16.18, and 17.6 $\hbox{$\mu $m}$, and one strong absorption feature at 14.98 $\hbox{$\mu $m}$. The emission features at 13.87 and 16.18 $\hbox{$\mu $m}$ are excited vibrational bands of CO2, while the absorption feature is the fundamental ν2 band. The 17.6 $\hbox{$\mu $m}$ emission feature has a completely different character than the molecular lines and we report its identification as Fe i fluorescence. We used a two-slab model with the radiative transfer code radex to model the CO2 Q-branch bandheads. Our results indicate a slab of gas with T∼600 K located at ∼3–4 R*. The cool temperature discrepancy with the radius provides observational evidence for the previously theoretical ‘refrigeration zone’.

scholarly journals SN 2017gci: a nearby Type I Superluminous Supernova with a bumpy tail

2021 ◽  
Author(s):  
A Fiore ◽  
T-W Chen ◽  
A Jerkstrand ◽  
S Benetti ◽  
R Ciolfi ◽  
...  
Keyword(s):  
Initial Period ◽  
Absolute Magnitude ◽  
Emission Feature ◽  
Light Curves ◽  
Type I ◽  
Power Sources ◽  
Circumstellar Material ◽  
Maximum Light ◽  
Broad Emission ◽  
Photometric Observations

Abstract We present and discuss the optical spectro-photometric observations of the nearby (z = 0.087) Type I superluminous supernova (SLSN I) SN 2017gci, whose peak K-corrected absolute magnitude reaches Mg = −21.5 mag. Its photometric and spectroscopic evolution includes features of both slow- and of fast-evolving SLSN I, thus favoring a continuum distribution between the two SLSN-I subclasses. In particular, similarly to other SLSNe I, the multi-band light curves of SN 2017gci show two re-brightenings at about 103 and 142 days after the maximum light. Interestingly, this broadly agrees with a broad emission feature emerging around 6520 Å after ∼51 days from the maximum light, which is followed by a sharp knee in the light curve. If we interpret this feature as Hα, this could support the fact that the bumps are the signature of late interactions of the ejecta with a (hydrogen-rich) circumstellar material. Then we fitted magnetar- and CSM-interaction- powered synthetic light curves onto the bolometric one of SN 2017gci. In the magnetar case, the fit suggests a polar magnetic field Bp ≃ 6 × 1014 G, an initial period of the magnetar Pinitial ≃ 2.8 ms, an ejecta mass Mejecta ≃ 9 M⊙ and an ejecta opacity κ ≃ 0.08 cm2 g−1. A CSM-interaction scenario would imply a CSM mass ≃ 5 M⊙ and an ejecta mass ≃ 12 M⊙. Finally, the nebular spectrum of phase +187 days was modeled, deriving a mass of ∼10 M⊙ for the ejecta. Our models suggest that either a magnetar or CSM interaction might be the power sources for SN 2017gci and that its progenitor was a massive (40 M⊙) star.

scholarly journals AstroSat observations of the first Galactic ULX pulsar Swift J0243.6+6124

2020 ◽  
Vol 500 (1) ◽  
pp. 565-575
Author(s):  
Aru Beri ◽  
Sachindra Naik ◽  
Kulinder Pal Singh ◽  
Gaurava K Jaisawal ◽  
Sudip Bhattacharyya ◽  
...  
Keyword(s):  
Power Law ◽  
Broad Band ◽  
Line Emission ◽  
High Energy ◽  
Emission Feature ◽  
Iron Line ◽  
Strong Function ◽  
X Ray ◽  
Broad Emission ◽  
The Continuum

ABSTRACT Swift J0243.6+6124, the first Galactic ultraluminous X-ray pulsar, was observed during its 2017–2018 outburst with AstroSat at both sub- and super-Eddington levels of accretion with X-ray luminosities of LX ∼ 7 × 1037 and 6 × 1038 erg s−1, respectively. Our broad-band timing and spectral observations show that X-ray pulsations at ${\sim}9.85~\rm {s}$ have been detected up to 150 keV when the source was accreting at the super-Eddington level. The pulse profiles are a strong function of both energy and source luminosity, showing a double-peaked profile with pulse fraction increasing from ∼$10{{{\ \rm per\ cent}}}$ at $1.65~\rm {keV}$ to 40–80 ${{\ \rm per\ cent}}$ at $70~\rm {keV}$. The continuum X-ray spectra are well modelled with a high-energy cut-off power law (Γ ∼ 0.6–0.7) and one or two blackbody components with temperatures of ∼0.35 and $1.2~\rm {keV}$, depending on the accretion level. No iron line emission is observed at sub-Eddington level, while a broad emission feature at around 6.9 keV is observed at the super-Eddington level, along with a blackbody radius ($121\!-\!142~\rm {km}$) that indicates the presence of optically thick outflows.

scholarly journals Aromatic, aliphatic, and the unidentified 21 micron emission features in proto-planetary nebulae

2008 ◽  
Vol 4 (S251) ◽  
pp. 213-214 ◽  
Author(s):  
Bruce J. Hrivnak ◽  
Kevin Volk ◽  
T. R. Geballe ◽  
Sun Kwok
Keyword(s):  
Planetary Nebulae ◽  
Emission Feature ◽  
Agb Stars ◽  
New Feature ◽  
Simple Molecules

AbstractAromatic features at 3.3, 6.2, 7.7, 8.6, 11.3 μm are observed in proto-planetary nebulae (PPNe) as well as in PNe and H ii regions. Aliphatic features at 3.4 and 6.9 μm are also observed; however, these features are often stronger in PPNe than in PNe. These observations suggest an evolution in the features from simple molecules (C2H2) in AGB stars to aliphatics in PPNe to aromatics in PNe. In the same carbon-rich PPNe, a strong, broad, unidentified 21 μm emission feature has been found. We will present recent observations of the aromatic, aliphatic, and 21 μm emission features, along with C2H2 (13.7 μm) and a new feature at 15.8 μm, and discuss correlations among them and other properties of these PPNe.

scholarly journals The 8-22μm Excess in Carbon Stars From IRAS LRS Spectra

1989 ◽  
Vol 106 ◽  
pp. 402-402
Author(s):  
S. J. Little ◽  
I. R. Little-Marenin
Keyword(s):  
Dust Emission ◽  
Unknown Origin ◽  
Carbon Star ◽  
Variable Stars ◽  
Emission Feature ◽  
Absorption Feature ◽  
Carbon Stars ◽  
Mira Variables ◽  
Period Variable ◽  
Ir Emission

We have measured the excess IR emission from carbon mira and SR variable stars from IRAS LRS spectra. The 8-22μm excess is defined as the ratio of flux above a 2500K energy distribution fit to the LRS spectrum at about 8μm. The carbon star LRS spectra show both emission and absorption features, which are incorporated into our 8-22pm excess. The most prominent feature in carbon stars is the 11.2μm SiC dust emission feature extending from 10μm to 13.8 μm. We observe another emission feature of unknown origin which peaks between 8.4-8.7μm. The SiC emission feature is occasionally blended on the red side by an absorption feature (attributed to gaseous HCN + C2H2) which extends from about 12-16μm. Many of the spectra appear to turn down at the 8μm end due (?) to an HCN + C2H2 absorption feature located at 7.1μm. Carbon stars do not generally show as large an excess as the M mira variables do. The figure below shows our measured excesses for both carbon miras and carbon semi-regular variables. There appears to be little correlation of excess with period, however the mira variables show about twice the range of variation of excess that the semi-regular variables do. We find little correlation between our measured 8-22μm excess and the excesses of Jura (Ap. J., 303, 327, 1986) based on the ratio of 12μm flux to 2μm flux. Our data do support hi s conclusion that longer period variable stars show larger average excesses, but this is only true for mira variables in our analysis.

scholarly journals A Search for Wolf-Rayet Stars in Giant Extragalactic Bursts of Star Formation

1986 ◽  
Vol 116 ◽  
pp. 499-501
Author(s):  
Alison W. Campbell ◽  
Linda J. Smith
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Equivalent Width ◽  
Hii Regions ◽  
Emission Feature ◽  
Star Forming ◽  
Star Forming Regions ◽  
Broad Emission ◽  
Nearby Galaxies ◽  
Emission Line Galaxies

It is well known that some giant extragalactic star-forming regions contain WR stars. D'Odorico, Massey, Rosa and coworkers found many examples in nearby galaxies of giant HII regions whose spectra show that they contain WN, and occasionally, WC stars. The dwarf emission-line galaxies He 2–10 (Allen et al. 1976) and Tol 3 (Kunth & Sargent 1981) have a strong broad emission feature near HeII 4686Å; in the latter object ∼150 WN stars are required to explain the observed equivalent width.

Polarimetric Observations of Red Variables: A Study of Gas and Particle Interactions

1979 ◽  
Vol 46 ◽  
pp. 386-408 ◽  
Author(s):  
G. V. Coyne ◽  
I. S. McLean
Keyword(s):  
Wavelength Dependence ◽  
Stellar Atmosphere ◽  
Molecular Absorption ◽  
Absorption Bands ◽  
Absorption And Emission ◽  
Mira Variables ◽  
Stellar Photosphere ◽  
Regular Variable ◽  
Red Supergiants ◽  
Balmer Lines

AbstractIn recent years the wavelength, dependence of the polarization in a number of Mira variables, semi-regular variables and red supergiants has been measured with resolutions between 0.3 and 300 A over the range 3300 to 11000 A. Variations are seen across molecular absorption bands, especially TiO bands, and across atomic absorption and emission lines, especially the Balmer lines. In most cases one can ignore or it is possible to eliminate the effects due to interstellar polarization, so that one can study the polarization mechanisms operating in the stellar atmosphere and environment. The stars Omicron Ceti. (Mira), V CVn (semi-regular variable) and Mu Cephei (M2 la), in addition to other stars similar to them, will be discussed in some detail.Models to explain the observed polarization consider that the continuum flux is polarized either by electron, molecular and/or grain scattering or by temperature variations and/or geometrical asymmetries over the stellar photosphere. This polarized radiation is affected by atomic and molecular absorption and emission processes at various geometric depths in the stellar atmosphere and envelope. High resolution spectropolarimetry promises, therefore, to be a power-rul tool for studying stratification effects in these stars.

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