scholarly journals ASCA Observations of LINERs

1997 ◽  
Vol 159 ◽  
pp. 54-55
Author(s):  
Y. Terashima ◽  
H. Kunieda ◽  
N. Iyomoto ◽  
K. Makishima ◽  
P. J. Serlemitsos
Keyword(s):  
Emission Line ◽  
Seyfert Galaxies ◽  
Point Sources ◽  
Photon Statistics ◽  
Short Time Scale ◽  
Spectral Slope ◽  
Iron Line ◽  
X Ray ◽  
Intrinsic Absorption ◽  
Short Time

ASCA observations have revealed the presence of low-luminosity AGN in ~10 LINERs as a hard point sources at the nucleus. The X-ray continuum shapes (photon indices Γ ≈ 1.8) are very similar to those of Seyfert galaxies (Makishima et al. 1997, Serlemitsos et al. 1996). An iron emission line is observed from heavily absorbed low-luminosity AGNs (Makishima et al. 1997), while M81 is the only object among those with small intrinsic absorption from which an iron line detected (Ishisaki et al. 1996) on account of limited photon statistics for other objects.We summed up the ASCA spectra of 5 LINERs which host low-luminosity AGN of low intrinsic absorption to search for an iron emission line. We used 7 observations of 5 objects (NGC 1097, NGC 3310, NGC 3998, NGC 4450, and NGC 4594) to make a composite spectrum. All the objects have very similar X-ray characteristics (spectral slope, intrinsic absorption, no short time-scale variability; Iyomoto et al. 1996, Serlemitsos et al. 1996).

scholarly journals Discovering novae in early-type galaxies with MUSE: A chance find in NGC 1404, and 12 more candidates from an archival search

2020 ◽  
Vol 494 (1) ◽  
pp. L1-L5
Author(s):  
Russell J Smith
Keyword(s):  
Elliptical Galaxy ◽  
Point Sources ◽  
Short Time Scale ◽  
Early Type ◽  
X Ray ◽  
Type Ia ◽  
Hα Emission ◽  
Integral Field Spectrograph ◽  
Short Time ◽  
Nova Outburst

ABSTRACT I report the discovery of a transient broad-Hα point source in the outskirts of the giant elliptical galaxy NGC 1404, discovered in archival observations taken with the Multi-Unit Spectroscopic Explorer (MUSE) integral field spectrograph. The Hα line width of 1950 km s−1 full width at half-maximum, and luminosity of (4.1 ± 0.1) × 1036 erg s−1, are consistent with a nova outburst, and the source is not visible in MUSE data obtained 9 months later. A transient soft X-ray source was detected at the same position (within <1 arcsec), 14 yr before the Hα transient. If the X-ray and Hα emission are from the same object, the source may be a short-time-scale recurrent nova with a massive white dwarf accretor, and hence a possible Type-Ia supernova progenitor. Selecting broad-Hα point sources in MUSE archival observations for a set of nearby early-type galaxies, I discovered 12 more nova candidates with similar properties to the NGC 1404 source, including five in NGC 1380 and four in NGC 4365. Multi-epoch data are available for four of these twelve sources; all four are confirmed to be transient on ∼1 yr time-scales, supporting their identification as novae.

scholarly journals Recent Spectroscopy of X-Ray Sources and Systems Related to Cataclysmic Variables: I

1983 ◽  
Vol 72 ◽  
pp. 21-24
Author(s):  
A.P. Cowley ◽  
D. Crampton ◽  
J.B. Hutchings
Keyword(s):  
Emission Line ◽  
Time Scale ◽  
Cataclysmic Variables ◽  
Short Time Scale ◽  
X Ray ◽  
Spectroscopic Observations ◽  
Low Mass ◽  
Short Time

ABSTRACTWe present results of recent spectroscopic observations of A) some LMC X-ray sources, B) the X-ray burster 1735-44, and C) the peculiar emission-line binary BE UMa. From the short time scale variations and inferred low mass components each shows some similarities to more classical CV's.

ON THE X-RAY PROPERTIES OF H2O MASER HOST GALAXIES

2009 ◽  
Vol 18 (09) ◽  
pp. 1367-1379 ◽  
Author(s):  
QIAN GUO ◽  
JIANG-SHUI ZHANG ◽  
JUN-HUI FAN
Keyword(s):  
Emission Line ◽  
Thermal Emission ◽  
Accretion Rate ◽  
Line Emission ◽  
Special Kind ◽  
Seyfert Galaxies ◽  
Emission Model ◽  
Host Galaxies ◽  
Iron Line ◽  
X Ray

All galaxies beyond the Magellanic clouds with detected H 2 O maser emission so far are investigated and their X-ray observations are collected in detail to probe the X-ray properties of this special kind of galaxies. The soft excess and the strong iron emission line are commonly presented in their X-ray spectrum. Similar to the spectra of normal Seyfert 2 galaxies, the X-ray soft components are usually explained well by two alternative models or their combination: the absorbed power law model and the thermal emission model. The hard X-ray continua are usually flat, which should be caused by the increase of the reflection component, with the increase of the absorbing material density. Modeling their X-ray spectra shows that high absorbing column density is prevalent in our H 2 O megamaser host AGNs. Further, we investigate a possible relation between the iron line emission and the nuclear X-ray emission. It shows no significant correlation between the equivalent width (EW) of the neutral Fe Kα emission line (~ 6.4 keV) and the intrinsic nuclear X-ray luminosity. However, one trend appears clearly — the EW of the iron line decreases with the increase of the observed X-ray luminosity for our H 2 O maser galaxies. We also estimate the accretion rate of H 2 O maser host AGNs and the results show that maser galaxies may have a higher accretion rate than nonmaser Seyfert galaxies. In addition, possible relations between the EW of the iron line with the accretion rate and the central black hole mass are investigated and no significant trend of correlation can be found between them.

scholarly journals IPS Observations of Short-Time Scale Interplanetary Activity

1996 ◽  
Vol 154 ◽  
pp. 225-228
Author(s):  
Pradeep Gothoskar ◽  
A. Pramesh Rao
Keyword(s):  
Time Scale ◽  
Solar Maximum ◽  
Component Model ◽  
Scintillation Index ◽  
Short Time Scale ◽  
High Time Resolution ◽  
The Sun ◽  
X Ray ◽  
Average Mass ◽  
Short Time

AbstractWe have carried out a program of continuous Interplanetary Scintillation (IPS) monitoring of the interplanetary activity using Ooty Radio Telescope (ORT). From May 1990 to March 1991, during the 22nd solar maximum, a few radio sources were monitored to provide long stretches of IPS data with a high-time resolution of few minutes. These observations covered 0.3 to 0.8 AU region (12° to 70° elongations) around the sun at several heliographic latitudes. During the observation, we detected 33 short-time scale IPS events which had significant variation in the scintillation index and solar wind velocity. These were considered to be due to travelling interplanetary disturbances.A multi-component model of plasma density enhancement was developed to estimate the geometry and physical properties of these IPS events. Detailed analysis of 20 of these events suggests, 1. fast IPS events were interplanetary signatures of Coronal Mass Ejections (CMEs), 2. the average mass and energy of these events was ~ 1016 gm and 1033 erg respectively, 3. 80% of IPS events were associated with X-ray flares on the sun and 50% were associated with geomagnetic activity at earth. Detailed study of the multi-component model suggests IPS observations at smaller elongations (hence at higher radio frequencies) are more suited to detect fast-moving interplanetary disturbances such as produced by CMEs.

scholarly journals X-Ray Properties of LINERs and Low Luminosity Seyfert Galaxies Observed with ASCA

1998 ◽  
Vol 188 ◽  
pp. 444-445
Author(s):  
Y. Terashima ◽  
H. Kunieda ◽  
P.J. Serlemitsos ◽  
A. Ptak
Keyword(s):  
Seyfert Galaxies ◽  
Iron Line ◽  
X Ray

We present ASCA spectra of low luminosity AGNs with X-ray luminosities of 1040-41 ergs s−1. Their X-ray continua are very similar to Seyfert galaxies. Although iron K emissin centered at 6.4 keV or 6.7 keV is detected from a few objects, iron K emission is weak on average. Possible reasons for variety of iron line properties are discussed.

Search for short time-scale periodicity in the X-ray flux of 4U1700 – 37

Nature ◽  
1979 ◽  
Vol 279 (5713) ◽  
pp. 508-509
Author(s):  
G. BRANDUARDI ◽  
A. K. DUPREE ◽  
P. W. SANFORD ◽  
G. S. G. POLLARD
Keyword(s):  
Time Scale ◽  
Short Time Scale ◽  
X Ray ◽  
Short Time

scholarly journals X-Ray Properties of Galactic Nuclei

1980 ◽  
Vol 5 ◽  
pp. 623-630
Author(s):  
Daniel W. Weedman
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Seyfert Galaxy ◽  
Seyfert Galaxies ◽  
Strong Emission ◽  
X Ray ◽  
Ngc 4151 ◽  
Survey Results ◽  
Emission Line Galaxies

Preparing this review was my just punishment for stating only two years ago - in another review (Weedman 1977) - that Seyfert galaxies are not strong X-ray sources. I said that because, as recently as three years ago, NGC 4151 was the only Seyfert galaxy known as an X-ray source. Now we have 36 Seyfert 1 galaxies, along with 12 other galaxies with strong emission-line nuclei, that are X-ray sources. And this is all without even having HEAO-2 data at our disposal yet. The study of active galactic nuclei with X-ray astronomy is progressing so rapidly that a reviewer feels almost hopeless. The best I can do is summarize what is known as of the summer of 1979 and give a simple overview of how X-ray and other properties relate.Some excellent reviews of the X-ray properties of Seyfert and other emission-line galaxies already exist. I especially recommend that by Andrew Wilson (1979). He provides very complete references as of a year ago, but X-ray astronomy is progressing so rapidly that he then had only somewhat more than half the active nuclei now in Tables 1 and 2. It was the group working with the Ariel V SSI that made the initial comprehensive X-ray studies of Seyfert galaxies (Ward et al. 1977, Elvis et al. 1978). The UHURU results for Seyfert galaxies followed soon after and are summarized by Tananbaum et al. (1978); the HEAO-A-2 survey results are now in press (Marshall et al. 1979) I have tried to incorporate these and other recent results in Tables 1 and 2.

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