Search

Changing look active galactic nuclei (CLAGNs) are rare cases of AGNs, where the continuum flux increases/decreases and the broad emission lines appear/disappear within short time-scales. These extreme changes challenge our understanding of accretion disc dynamics. We present a sample of four new CLAGNs at 0.026 < z < 0.107, which were found by cross-matching the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey with AGNs from the SDSS spectroscopic data base. Our results show that the selection criteria of $\gt \mathopen |0.5\mathclose |$ mag change in SDSS-g band is ineffective at lower redshifts. This is, in part, due to the fact that the g band is probing a different part of the AGNs spectral energy distribution at these redshifts. The bigger issue is that the galaxy continuum dominates the spectrum and thus overwhelms any variation of the AGNs continuum that might contribute to photometric variations. This suggests the need to use different methods for future low-redshift CLAGNs searches.

Monthly notices of the Royal Astronomical Society 492(2), 2606 - 2621 (2020). doi:10.1093/mnras/stz3439, We present 1–10 GHz radio continuum flux density, spectral index, polarization, and rotation measure (RM) images of the youngest known Galactic supernova remnant (SNR) G1.9+0.3, using observations from the Australia Telescope Compact Array. We have conducted an expansion study spanning eight epochs between 1984 and 2017, yielding results consistent with previous expansion studies of G1.9+0.3. We find a mean radio continuum expansion rate of (0.78 ± 0.09) per cent yr$^{−1}$ (or ∼8900 km s$^{−1}$ at an assumed distance of 8.5 kpc), although the expansion rate varies across the SNR perimetre. In the case of the most recent epoch between 2016 and 2017, we observe faster-than-expected expansion of the northern region. We find a global spectral index for G1.9+0.3 of −0.81 ± 0.02 (76 MHz–10 GHz). Towards the northern region, however, the radio spectrum is observed to steepen significantly (∼−1). Towards the two so-called (east and west) ‘ears’ of G1.9+0.3, we find very different RM values of 400–600 and 100–200 rad m$^2$, respectively. The fractional polarization of the radio continuum emission reaches (19 ± 2) per cent, consistent with other, slightly older, SNRs such as Cas A., Published by Oxford Univ. Press, Oxford

We present high angular resolution 1.1mm continuum and spectroscopic ALMA observations of the well-known massive proto-cluster Mon R 2 IRS 3.The continuum image at 1.1mm shows two components, IRS 3 A and IRS 3 B, that are separated by $\sim$0.65$"$. We estimate that IRS 3 A is responsible of $\sim$80 % of the continuum flux, being the most massive component. We explore the chemistry of IRS 3 A based on the spectroscopic observations. In particular, we have detected intense lines of S-bearing species such as SO, SO$_2$, H$_2$CS and OCS, and of the Complex Organic Molecules (COMs) methyl formate (CH$_3$OCHO) and dimethyl ether (CH$_3$OCH$_3$). The integrated intensity maps of most species show a compact clump centered on IRS 3 A, except the emission of the COMs that is more intense towards the near-IR nebula located to the south of IRS 3 A, and HC$_3$N whose emission peak is located $\sim$0.5$"$ NE from IRS 3 A. The kinematical study suggests that the molecular emission is mainly coming from a rotating ring and/or an unresolved disk. Additional components are traced by the ro-vibrational HCN $\nu_2$=1 3$\rightarrow$2 line which is probing the inner disk/jet region, and the weak lines of CH$_3$OCHO, more likely arising from the walls of the cavity excavated by the molecular outflow. Based on SO$_2$ we derive a gas kinetic temperature of T$_k$$\sim$ 170 K towards the IRS 3 A. The most abundant S-bearing species is SO$_2$ with an abundance of $\sim$ 1.3$\times$10$^{-7}$, and $\chi$(SO/SO$_2$) $\sim$ 0.29. Assuming the solar abundance, SO$_2$ accounts for $\sim$1 % of the sulphur budget., Comment: 12 pages, 8 figures, accepted for publication in MNRAS

Using the IRAM NOrthern Extended Millimeter Array (NOEMA), we conducted a program to measure redshifts for 13 bright galaxies detected in the Herschel Astrophysical Large Area Survey (H-ATLAS) with $S_{500{\mu}\rm m}\ge$80 mJy. We report reliable spectroscopic redshifts for 12 individual sources, which are derived from scans of the 3 and 2 mm bands, covering up to 31 GHz in each band, and are based on the detection of at least two emission lines. The spectroscopic redshifts are in the range $2.08 10^{13}\,L_\odot$ galaxies. We also present a reanalysis of the spectral energy distributions including the continuum flux densities measured at 3 and 2 mm to derive the overall properties of the sources. Future prospects based on these efficient measurements of redshifts of high-z galaxies using NOEMA are outlined, including a comprehensive survey of all the brightest Herschel galaxies., Comment: 18 pages, 21 figures

We present the discovery of an optical accretion disk wind in the X-ray transient Swift J1858.6-0814. Our 90-spectrum data set, taken with the 10.4 m Gran Telescopio Canarias telescope over eight different epochs and across five months, reveals the presence of conspicuous P-Cyg profiles in He i at 5876 A and Hα. These features are detected throughout the entire campaign, albeit their intensity and main observational properties are observed to vary on timescales as short as 5 minutes. In particular, we observe significant variations in the wind velocity, between a few hundreds and ∼2400 km s; -1. In agreement with previous reports, our observations are characterized by the presence of frequent flares, although the relation between the continuum flux variability and the presence/absence of wind features is not evident. The reported high activity of the system at radio waves indicates that the optical wind of Swift J1858.6-0814 is contemporaneous with the radio jet, as is the case for the handful of X-ray binary transients that have shown so far optical P-Cyg profiles. Finally, we compare our results with those of other sources showing optical accretion disk winds, with emphasis on V404 Cyg and V4641 Sgr, since they also display strong and variable optical wind features as well as similar flaring behavior., Facultad de Ciencias Astronómicas y Geofísicas, Instituto Argentino de Radioastronomía

A new ground based device for the measurement of the Balmer continuum flux in solar flares was recently developed and installed at the Ondřejov Observatory. We observed an X1 solar flare on 2014 June 11 during its pre-flare and impulsive phases using a wide band spectrometer with a cadence of 1 s. The Ensemble Empirical Mode Decomposition (EEMD) of the registered signal was performed. We found damped oscillations with a period of 609 s and damping time of 1478 s. Shorter periods of about 30–120 s were found during the pre-flare and impulsive phases, but they might be of non-flare origin

A primary goal of the SCUBA-2 Web survey is to perform tomography of the early inter-galactic medium by studying systems containing some of the brightest quasi-stellar objects (QSOs; 2.510^14 L_odot) QSOs with previous submillimetre continuum detections were followed up with CO(3-2) observations using the NOEMA interferometer. All but two of the QSOs are detected in CO(3-2); for one non-detection, our observations show a tentative 2sigma line at the expected position and redshift, and for the other non-detection we find only continuum flux density an order of magnitude brighter than the other sources. In three of the fields, a companion potentially suitable for tomography is detected in CO line emission within 25 arcsec of the QSO. We derive gas masses, dynamical masses and far-infrared luminosities, and show that the QSOs in our sample have similar properties as compared to less luminous QSOs and SMGs in the literature, despite the fact that their black-hole masses (which are proportional to L_AGN) are 1-2 orders of magnitude larger. We discuss two interpretations of these observations: this is due to selection effects, such as preferential face-on viewing angles and picking out objects in the tail ends of the scatter in host-galaxy mass and black-hole mass relationships; or the black hole masses have been overestimated because the accretion rates are super-Eddington., Comment: 16 pages, 7 figures. Latest version published in MNRAS

We report the result of our search for the 380 GHz H2O line emissions from the quadruply lensed QSO MG J0104+0534 at z = 2.639 with the Atacama Large Millimeter/submillimeter Array (ALMA). Our observation shows a tentative detection of the 380 GHz line from the lensed QSO, and line spectrum shows a broad spectral distribution that has a velocity width of ~290 km/s and a peak flux of ~0.8 mJy. The integrated-intensity map of the H2O line show lensed emissions at the A1 and A2 component of the QSO, with the A2 component slightly resolved. The integrated line flux ratio between the A1 and A2 component shows unexpected difference with the continuum flux ratio. Based on our gravitational lens modeling assuming our tentative detection is real, this flux ratio anomaly would suggest that the 380 GHz line emissions come from two or three spatially displaced locations in the QSO, with the dominant one located at the position of the continuum emission from the QSO and the other one(s) displaced from the continuum by ~1.5 kpc on the source plane.

The cyanide radical CN is abundant in protoplanetary disks, with line fluxes often comparable to those of $^{13}$CO. It is known to be sensitive to UV irradiation of the upper disk atmosphere, with models predicting ring-shaped emission. We seek to characterize the CN emission from 94 Class II disks in the Lupus star forming region, compare it to observations in other regions, and interpret our observations with a grid of models. The CN emission morphology is discussed for two primordial disks, Sz 71 and Sz 98, and modeled in more detail. ALMA observed CN N=3-2 in Lupus disks down to sensitivities better than previous surveys. Models constructed with the physico-chemical code DALI are used to study the integrated fluxes of the disks and resolved emission of CN in disks without (dust) substructures. We find that CN N=3-2 is bright, and detected in 38% of sources, but its disk-integrated flux is not strongly correlated to either $^{13}$CO or continuum flux. Compared to pre-ALMA single-dish surveys, no significant difference in the CN flux distributions in Lupus and Taurus-Auriga is found, although $\rho$ Ophiuchus disks may be fainter on average. We find ring-shaped CN emission with peak radii of ~50 AU in two resolved disks. We conclude that a large fraction of sources is faint in CN; only exponential gas surface density cutoffs at $R_{c} \leq 15$ AU can reconcile observations with models. This is the first observational evidence of such a compact gas disk population in Lupus. Absolute intensities and the emission morphology of CN are reproduced by DALI models without the need for any continuum substructure; they are unrelated to the CO snowline location. These observations and the successful modeling of these rings provide a new probe of the structure and conditions in disks, and particularly their incident UV radiation field, if disk size is determined by the data., Comment: 22 pages, 14 figures, A&A accepted

Spectangular is a GUI based software package written in C++ designed for spectral disentangling on the wavelength scale. The code disentangles spectra of SB1 and SB2 systems and can now also be used also for spectra showing variability. In this work, effects of variability caused by telluric lines, line profile, and continuum flux are being investigated. Also shown is the disentangling on spectra from an artificial eclipsing binary. It is now possible to optimize on the flux ratios of each spectrum, making the disentangling a technique for extracting photometric information from spectroscopic observations usually provided by additional photometry. Furthermore, we make some comments about changes to the code since it was first published., accepted to A&A

During the 2014 HST/Swift and ground-based multi-wavelength monitoring campaign of NGC 5548 (AGN STORM), the UV-optical broad emission lines exhibited anomalous, decorrelated behaviour relative to the far-UV continuum flux variability. Here, we use key diagnostic emission lines (Ly-alpha and He II) for this campaign to infer a proxy for the all important, variable driving EUV continuum incident upon BLR clouds. The inferred driving continuum provides a crucial step towards the recovery of the broad emission line response functions in this AGN. In particular, the ionising continuum seen by the BLR was weaker and softer during the anomalous period than during the first third of the campaign, and apparently less variable than exhibited by the far-UV continuum. We also report the first evidence for anomalous behaviour in the longer wavelength (relative to 1157A) continuum bands. This is corroborative evidence that a significant contribution to the variable UV-optical continuum emission arises from a diffuse continuum emanating from the same gas that emits the broad emission lines., Comment: 17 pages, 8 figures, accepted for publication in MNRAS 2019 April 25

The purpose of the current work is the formulation of macroscopic constitutive relations, and in particular continuum flux densities, for polar continua from the underlying mass point dynamics. To this end, generic microscopic continuum field and balance relations are derived from phase space transport relations for expectation values of point fields related to additive mass point quantities. Given these, microscopic energy, linear momentum and angular momentum, balance relations are obtained in the context of the split of system forces into non-conservative and conservative parts. In addition, divergence–flux relations are formulated for the conservative part of microscopic supply-rate densities. For the case of angular momentum, two such relations are obtained. One of these is force-based, and the other is torque-based. With the help of physical and material theoretic restrictions (e.g. material frame-indifference), reduced forms of the conservative flux densities are obtained. In the last part of the work, formulation of macroscopic constitutive relations from their microscopic counterparts is investigated in the context of different spatial averaging approaches. In particular, these include (weighted) volume-averaging based on a localization function, surface averaging of normal flux densities based on Cauchy flux theory and volume averaging with respect to centre of mass.

We report on the detection of a pulsating Fe Ka line in the High Mass X-ray Binary (HMXB) GX 301-2, from a 40-ks Chandra observation near periastron. The pulsations in the Fe Ka emission appeared only in the first 7 ks of the observation, with a period and phase profile similar to those of the continuum. The presence of pulsed fluorescent lines is an unusual property in HMXBs. After 7 ks, the continuum flux increased by a factor of three, the Fe Ka flux increased only by about 10\%, and the pulsating signal in the line disappeared. Finally, in the second half of the observation, both the continuum and the line flux dropped by a similar factor of 2. We suggest that the pulsating component of the Fe Ka line is coming from a transient non-isotropic distribution of dense gas around the neutron star, for example an accretion stream induced by periastron passage, or from the illuminated surface of the donor star., 8 pages, 5 figures, MNRAS accepted

We report on the latest results from Hubble Space Telescope (HST) far ultraviolet spectroscopy with the Cosmic Object Spectrograph (COS), of the short orbital period recurrent novae (RNe) T Pyxidis, IM Norma (the first ever FUV spectrum of this RN) and CI Aquilae, the only known recurrent novae with main sequence donors and orbital periods less than a day. The last two HST COS spectra we obtained in October, 2016 and June, 2016, reveal that the accretion rate of T Pyx has declined by 20% below its quiescent continuum flux level recorded by the IUE following the 1966 outburst, an indication that the system might not have yet reached its (new) quiescent state. Recent HST COS Spectroscopy of the cooling of the white dwarf in the prototypical dwarf nova U Geminorum is also discussed with a focus on the chemical abundances in the white dwarf photosphere.

The analysis of a series of seven observations of the nearby ($z=0.0809$) QSO, PG 1211+143, taken with the Reflection Grating Spectrometer (RGS) on-board XMM-Newton in 2014, are presented. The high resolution soft X-ray spectrum, with a total exposure exceeding 600 ks, shows a series of blue-shifted absorption lines, from the He and H-like transitions of N, O and Ne, as well as from L-shell Fe. The strongest absorption lines are all systematically blue-shifted by $-0.06c$, originating in two absorption zones, from low and high ionization gas. Both zones are variable on timescales of days, with the variations in absorber opacity effectively explained by either column density changes or by the absorber ionization responding directly to the continuum flux. We find that the soft X-ray absorbers probably exist in a two-phase wind, at a radial distance of $10^{17}-10^{18}$ cm from the black hole, with the lower ionization gas as denser clumps embedded within a higher ionization outflow. The overall mass outflow rate of the soft X-ray wind may be as high as $2{\rm M}_{\odot}$ yr$^{-1}$, close to the Eddington rate for PG 1211+143 and similar to that previously deduced from the Fe K absorption., 20 pages, 10 figures, accepted for publication in the Astrophysical Journal

We present SMA and NOEMA observations of the host galaxy of FRB 121102 in the CO 3-2 and 1-0 transitions, respectively. We do not detect emission from either transition. We set $3\sigma$ upper limits to the CO luminosity $L_{CO} < 2.5 \times 10^7\,{\rm K\,km\,s}^{-1} {\, \rm pc^{-2}}$ for CO 3-2 and $L_{CO} < 2.3 \times 10^9\, {\rm K\,km\,s}^{-1} {\, \rm pc^{-2}}$ for CO 1-0. For Milky-Way-like star formation properties, we set a $3\sigma$ upper limit on the $H_2$ mass of $2.5 \times 10^8 \rm\ M_{\odot}$, slightly less than the predictions for the $H_2$ mass based on the star formation rate. The true constraint on the $H_2$ mass may be significantly higher, however, because of the reduction in CO luminosity that is common forlow-metallicity dwarf galaxies like the FRB host galaxy. These results demonstrate the challenge of identifying the nature of FRB progenitors through study of the host galaxy molecular gas. We also place a limit of 42 $\mu$Jy ($3\sigma$) on the continuum flux density of the persistent radio source at 97 GHz, consistent with a power-law extrapolation of the low frequency spectrum, which may arise from an AGN or other nonthermal source., Comment: Accepted for publication in AJ

We present high-resolution (0.17\arcsec $\times$ 0.14\arcsec) Atacama Large Millimeter/submillimeter Array (ALMA) observations of the CO\,(6-5) line, and 435\um\ dust continuum emission within a $\sim$9\arcsec $\times$ 9\arcsec\ area centered on the nucleus of the galaxy NGC\,5135. NGC\,5135 is a well-studied luminous infrared galaxy that also harbors a Compton-thick active galactic nucleus (AGN). At the achieved resolution of 48 $\times$ 40\,pc, the CO\,(6-5) and dust emissions are resolved into gas "clumps" along the symmetrical dust lanes associated with the inner stellar bar. The clumps have radii between $\sim$45-180\,pc and CO\,(6-5) line widths of $\sim$60-88\,\kms. The CO\,(6-5) to dust continuum flux ratios vary among the clumps and show an increasing trend with the \FeII/Br-$\gamma$ ratios, which we interpret as evidence for supernova-driven shocked gas providing a significant contribution to the \co65\ emission. The central AGN is undetected in continuum, nor in CO\,(6-5) if its line velocity width is no less than $\sim$\,40\,\kms. We estimate that the AGN contributes at most 1\% of the integrated CO\,(6-5) flux of 512 $\pm$ 24$\,$Jy\kms\ within the ALMA field of view, which in turn accounts for $\sim$32\% of the CO\,(6-5) flux of the whole galaxy., Comment: 21 pages, 12 figures, Accepted for publication in ApJ

Disk reverberation mapping of a handful of nearby AGN suggest accretion disk sizes which are a factor few too large for their luminosities, apparently at odds with the standard model. Here, we investigate the likely contribution to the measured delay signature of diffuse continuum emission arising from broad line region gas. We start by constructing spherically symmetric pressure-law BLR models (i.e., $P(r)\propto r^{-s}$) that approximately reproduce the observed emission line fluxes of the strong UV--optical emission-lines in the best-studied source, NGC~5548. We then determine the contribution of the diffuse continuum to the measured continuum flux and inter-band delays, accounting for the observed variability behaviour of the ionizing nuclear continuum. Those pressure-law models that approximately reproduce the observed emission-line luminosities unavoidably produce substantial diffuse continuum emission. This causes a significant contamination of the disk reverberation signature (i.e., wavelength-dependent continuum delays). Qualitatively, the diffuse continuum delay signatures produced by our models resemble that observed for NGC~5548, including the deviation of the lag spectrum above that of a simple power-law in wavelength, short-ward of the Balmer and Paschen jumps. Furthermore, for reasonable estimates of the BLR covering fraction, the delay induced by diffuse continuum emission causes elevated inter-band delays over the entire UV--optical regime; for these pressure-law models, there are no `disk-dominated' wavelength intervals. Thus, the diffuse continuum contribution must be taken into account in order to correctly infer AGN accretion disk sizes based on inter-band continuum delays., Comment: 26 pages; accepted for publication in MNRAS. Edited to correct minor typographical errors

We have conducted an interferometric line survey in the 0.8 mm band toward the young high-mass protostar candidate NGC 2264 CMM3 with ALMA. CMM3 is resolved into the two continuum peaks, CMM3A and CMM3B, at an angular separation of 0.9". Thus, CMM3 is found to be a binary system candidate. We have detected molecular outflows associated with CMM3A and CMM3B each, indicating active star formation. In addition to the two peaks, six faint continuum peaks are detected around CMM3A and CMM3B, most of which are thought to be evolved low-mass protostars. CMM3A is found to be rich in molecular line emission including complex organic molecules such as HCOOCH3 and CH3OCH3. The emission of complex organic molecules is distributed within a compact region around the continuum peak of CMM3A. Hence, CMM3A apparently harbors a hot core. On the other hand, CMM3B is deficient in molecular line emission, although its continuum flux is almost comparable to that of CMM3A. Possible origins of the striking difference between CMM3A and CMM3B are discussed., Accepted for publication in ApJ, 7 figures, 2 tables

Here we present an analysis of spectro-polarimetric observations of type 1.5 AGN Mrk 6, performed with 6m telescope SAO RAN in 12 epochs (2010 -- 2013). Additionally, the inter-stellar mater (ISM) polarization has been observed and its contribution to the AGN spectral polarization is taken into account. We measured Stokes parameters and determined the polarization parameters in 12 spectra with and without correction for the ISM polarization. We estimated the time lag between the unpolarized and polarized continuum flux variation of about ~2 days, that indicates a compact scattering region which contributes to the polarized continuum variability. The polarization in H{\alpha} is complex, showing three prominent components in the BLR, one redshifted around +3000 km/s that corresponds to the red shoulder in H{\alpha}, and two blue-shifted around -2000 km/s and -6000 km/s. We found that the ISM polarization has a very significant influence on the measured AGN polarization parameters. After correcting the observations for the ISM polarization we were able to detect the Keplerian motion in the BLR. We give a new method for the black hole mass estimation using spectro-polarimetric observation in the line profile, finding the black hole mass in Mrk 6 of $M_{BH} \sim 1.53 \cdot 10^8 M_{\odot}$, that is in a good agreement with reverberation estimates., Comment: Version submitted to MNRAS, after minor revision

In this paper, we analyze the 1.3 mm continuum ALMA data that cover the majority of the infrared dark cloud (IRDC) G28.37+0.07. With a spatial resolution of 05 (2500 au at 5 kpc), the continuum image reveals five groups of dense cores. Each core group has a projected physical scale of about 1 pc, with core masses spanning a dynamic range of about 100. We use the dendrogram method (astrodendro) and a newly developed graph method (astrograph) to identify individual cores. The core masses are estimated through the millimeter continuum flux, assuming constant temperature and using an NH3-based gas temperature. We construct core mass functions (CMFs) based on the two methods and fit a power-law relation dN/d log M ∝ M −α to the CMFs for M > 0.79 M ⊙. In the constant-temperature scenario, astrograph gives α = 0.80 ± 0.10, while astrodendro gives α = 0.71 ± 0.11, both significantly shallower than the Salpeter-type initial mass function with α = 1.35. In the scenario where the NH3 gas temperature is applied to cores, astrograph gives α = 1.37 ± 0.06, while astrodendro gives α = 0.87 ± 0.07. Regional CMF slope variation is seen between the core groups. We also compare CMFs in three different environments, including IRDC G28.37+0.07, IRDC clumps, and G286.21+0.17, using the identical dendrogram method. Results show that IRDCs have smaller α than the cluster-forming cloud G286.21+0.17.

We analyze the spectral variability for two narrow line Seyfert 1 galaxies, PG 1700+518 and NGC 4051 using the spectral decomposition method. We focus on their optical Fe ii variability to investigate the origin of Fe ii in AGNs. For PG 1700+518, we find that the Fe ii size is about 200 light-days, which is consistent with the Hβ size derived from the empirical R–L relation. For NGC 4051, the [O iii] 5007 A flux is strongly correlated with continuum flux, suggesting that we should recalibrate the spectral flux on a scale defined by [O iii] flux. The corrected light curves of Fe ii, Hβ, He ii, fλ(5100 A) are given here. A detailed analysis will be given in the near future.

We present 5.5- and 9.0-GHz observations of five gamma-ray burst host galaxies at z < 0.5, taken using the Australia Telescope Compact Array. We determine tight constraints on the radio continuum flux of four sources (GRB hosts 060218, 060614, 020819 and 990712) and detect a fifth source, the host of GRB 031203, with a flux density Fν(5.50 GHz) = 216 ± 50 μJy. We discuss the star formation rates of all five sources. Our radio-derived star formation rates (and upper limits) are largely consistent with those derived from optical observations, suggesting either that there is little dust-obscured star formation in these sources, or that their starbursts are too young to have established representative radio continuum emission.

We present ALMA observations of the dwarf starburst galaxy Henize 2-10 in combination with previous SMA CO observations to probe the molecular environments of natal super star clusters. These observations include the HCO$^+$(1-0), HCN(1-0), HNC(1-0), and CCH(1-0) molecular lines, as well as 88 GHz continuum with a spatial resolution of $1''.7\times 1''.6$. After correcting for the contribution from free-free emission to the 88 GHz continuum flux density ($\sim$ 60% of the 88 GHz emission), we derive a total gas mass for He~2-10 of $M_{gas} = 4-6\times10^8$ M$_{\odot}$, roughly 5-20% of the dynamical mass. Based on a principle component analysis, HCO$^+$ is found to be the best "general" tracer of molecular emission. The line widths and luminosities of the CO emission suggests that the molecular clouds could either be as small as $\sim 8$ pc, or alternately have enhanced line widths. The CO emission and 88 GHz continuum are anti-correlated, suggesting that either the dust and molecular gas are not cospatial, which could reflect the 88 GHz continuum is dominated by free-free emission. The CO and CCH emission are also relatively anti-correlated, which is consistent with the CCH being photo-enhanced, and/or the CO being dissociated in the regions near the natal super star clusters. The molecular line ratios of regions containing the natal star clusters are different from the line ratios observed for regions elsewhere in the galaxy. In particular, the regions with thermal radio emission all have CO(2-1)/HCO$^+(1-0) < 16$, and the HCO$^+$/CO ratio appears to be correlated with the evolutionary stage of the clusters., 15 pages, 2 tables, 13 figures, accepted for publication in ApJ

We characterize the physical properties of T Chamaeleontis, a transitional T Tauri star showing UX Ori-type variability, and of its associated disc, and probe possible effects of disc clearing processes. Different spectral diagnostics are examined, based on a rich collection of optical high- and low-resolution spectra. We determine radial and projected rotational velocities, and measure equivalent widths of the Li I (6708 A) line and of the most prominent emission lines (e.g. Ha, Hb and [OI] 6300A); we analyse shape changes of photospheric lines via bisector-method, while variability in Ha and Hb is inspected through line-profile correlation matrices. The strength of the Ha and Hb emission is highly variable and well correlated with that of the [OI] lines, as well as with Av variations of over three magnitudes. Variations up to nearly 10 km/s in the radial velocity of the star are measured on analogous time-scale, but with no apparent periodicity. SED modelling confirms the existence of a gap in the disc. Variable circumstellar extinction is pointed out as responsible for the conspicuous variations observed in the stellar continuum flux and for concomitant changes in the emission features by contrast effect. Clumpy structures, incorporating large dust grains and orbiting the star within a few tenths of AU, obscure episodically the star and, eventually, part of the inner circumstellar zone, while the bulk of the hydrogen lines emitting zone and outer low-density wind region traced by the [OI] remain unaffected. Coherently with this scenario, the detected radial velocity changes are also explainable in terms of clumpy materials transiting and partially obscuring the star., 38 pages, 32 figures. To appear in the Astronomy and Astrophysics main journal

We have imaged the central ~1kpc of the circumnuclear starburst disk in the galaxy NGC253 in the HCN(1-0), HCO+(1-0), and CO(1-0) transitions at 60pc resolution using the Owens Valley Radio Observatory Millimeter-Wavelength Array (OVRO). We have also obtained Atacama Pathfinder Experiment (APEX) observations of the HCN(4-3) and the HCO+(4-3) lines of the starburst disk. We find that the emission from the HCN(1-0) and HCO+(1-0) transitions, both indicators of dense molecular gas, trace regions which are non-distinguishable within the uncertainties of our observations. Even though the continuum flux varies by more than a factor 10 across the starburst disk, the HCN/HCO+ ratio is constant throughout the disk, and we derive an average ratio of 1.1+/-0.2. From an excitation analysis we find that all lines from both molecules are subthermally excited and that they are optically thick. This subthermal excitation implies that the observed HCN/HCO+ line ratio is sensitive to the underlying chemistry. The constant line ratio thus implies that there are no strong abundance gradients across the starburst disk of NGC253. This finding may also explain the variations in L'(HCN)/L'(HCO+) between different star forming galaxies both nearby and at high redshifts., Comment: 9 pages, 12 figures, ApJ in press (volume 666 September)

The X-ray spectrum of GRS 1915+105 is known to have a ``broad iron spectral feature'' in the spectral hard state. Similar spectral features are often observed in Active Galactic Nuclei (AGNs) and other black-hole binaries (BHBs), and several models have been proposed for explaining it. In order to distinguish spectral models, time variation provides an important key. In AGNs, variation amplitude has been found to drop significantly at the iron K-energy band at timescales of ~10 ks. If spectral variations of black-holes are normalized by their masses, the spectral variations of BHBs at timescales of sub-seconds should exhibit similar characteristics to those of AGNs. In this paper, we investigated spectral variations of GRS 1915+105 at timescales down to ~10 ms. This was made possible for the first time with the Suzaku XIS Parallel-sum clocking (P-sum) mode, which has the CCD energy-resolution as well as a time-resolution of 7.8 ms. Consequently, we found that the variation amplitude of GRS 1915+105 does not drop at the iron K-energy band at any timescales from 0.06 s to 63000 s, and that the entire X-ray flux and the iron feature are independently variable at timescales of hours. These are naturally understood in the framework of the ``partial covering'' model, in which variation timescales of the continuum flux and partial absorbers are independent. The difference of energy dependence of the variation amplitude between AGN and BHB is presumably due to different mechanisms of the outflow winds, i.e., the partial absorbers are due to UV-line driven winds (AGN) or thermally-driven winds (BHB)., Comment: 32 pages, 16 figures, Accepted for publication in PASJ

Context. Our consortium performed an extensive multi-wavelength campaign of the nearby Seyfert 1 galaxy NGC 5548 in 2013-14. The source appeared unusually heavily absorbed in the soft X-rays, and signatures of outflowing absorption were also present in the UV. He-like triplets of neon, oxygen and nitrogen, and radiative recombination continuum (RRC) features were found to dominate the soft X-ray spectrum due to the low continuum flux. Aims. Here we focus on characterising these narrow emission features using data obtained from the XMM-Newton RGS (770 ks stacked spectrum). Methods. We use SPEX for our initial analysis of these features. Self-consistent photoionisation models from Cloudy are then compared with the data to characterise the physical conditions of the emitting region. Results. Outflow velocity discrepancies within the O VII triplet lines can be explained if the X-ray narrow-line region (NLR) in NGC 5548 is absorbed by at least one of the six warm absorber components found by previous analyses. The RRCs allow us to directly calculate a temperature of the emitting gas of a few eV ($\sim10^{4}$ K), favouring photoionised conditions. We fit the data with a Cloudy model of log $\xi = 1.45 \pm 0.05$ erg cm s$^{-1}$, log $N_H = 22.9 \pm 0.4$ cm$^{-2}$ and log v$_{turb} = 2.25 \pm 0.5$ km s$^{-1}$ for the emitting gas; this is the first time the X-ray NLR gas in this source has been modelled so comprehensively. This allows us to estimate the distance from the central source to the illuminated face of the emitting clouds as $13.9 \pm 0.6$ pc, consistent with previous work., Comment: Accepted by A&A, 15 pages, 6 figures

We calculate many different nova light curves for a variety of white dwarf masses and chemical compositions, with the assumption that free-free emission from optically thin ejecta dominates the continuum flux. We show that all these light curves are homologous and a universal law can be derived by introducing a ``time scaling factor.'' The template light curve for the universal law has a slope of the flux, F \propto t^{-1.75}, in the middle part (from ~2 to ~6 mag below the optical maximum), but it declines more steeply, F \propto t^{-3.5}, in the later part (from ~6 to ~10 mag). This break on the light curve is due to a quick decrease in the wind mass-loss rate. The nova evolutions are approximately scaled by the time of break. Once the time of break is observationally determined, we can derive the various timescales of novae such as the period of a UV burst phase, the duration of optically thick wind phase, and the turnoff date of hydrogen shell-burning. We have applied our template light curve model to the three well-observed novae, V1500 Cyg, V1668 Cyg, and V1974 Cyg. Our theoretical light curves show excellent agreement with the optical y and infrared J, H, K light curves. The WD mass is estimated, from the light curve fitting, to be 1.15 M_\sun for V1500 Cyg, 0.95 ~M_\sun for V1668 Cyg, and 0.95-1.05 M_\sun for V1974 Cyg., Comment: To appear in ApJS, vol.167, 23 pages including 24 figures

Using 7.5-year spectroscopic monitoring data of a sample of 17 Palomar-Green QSOs (PG QSOs) (z=0.061-0.371), we obtain the optical spectral slope for each object at all epochs by a power-law fit to the spectra in continuum bands. All of these 17 PG QSOs exhibit obvious spectral slope variability. Most of the 17 objects show anti-correlation between the spectral slope and the rest-frame 5100$A$ continuum flux while five of them exist strong anti-correlation (correlation coefficient R larger than 0.5). For the ensemble of these 17 PG QSOs, a strong anti-correlation between the average spectral slope and the average rest-frame 5100$A$ luminosity is found while no correlation is found between the spectral slope and the Eddington ratio. A median anti-correlation between spectral slope changes and continuum flux variations is also found which indicates a hardening of the spectrum during bright phases. Accretion disk (jet) instability models with other mechanisms associated with changes in the accretion processes are promising.

We present upper-limits on the masses of the putative central intermediate-mass black holes in two nearby Galactic globular clusters: 47Tuc (NGC104), the second brightest Galactic globular cluster, and NGC6397, a core-collapse globular cluster and, with a distance of 2.7 kpc, quite possibly the nearest globular cluster, using a technique suggested by T. Maccarone. These mass estimates have been derived from 3sigma upper limits on the radio continuum flux at 1.4 GHz, assuming that the putative central black hole accretes the surrounding matter at a rate between 0.1% and 1% of the Bondi accretion rate. For 47Tuc, we find a 3sigma upper limit of 2060 - 670 solar masses, depending on the actual accretion rate of the black hole and the distance to 47Tuc. For NGC6397, which is closer to us, we derive a 3sigma upper limit of 1290 - 390 solar masses. While estimating mass upper-limits based on radio continuum observations requires making assumptions about the gas density and the accretion rate of the black hole, their derivation does not require complex and time consuming dynamical modeling. Thus, this method offers an independent way of estimating black hole masses in nearby globular clusters. If, generally, central black holes in stellar systems accrete matter faster than 0.1% of the Bondi accretion rate, then these results indicate the absence of black holes in these globular clusters with masses as predicted by the extrapolated M-sigma relation.

INTEGRAL and RXTE performed three simultaneous observations of the nearby radio galaxy Cen A in 2003 March, 2004 January, and 2004 February with the goals of investigating the geometry and emission processes via the spectral/temporal variability of the X-ray/low energy gamma ray flux, and intercalibration of the INTEGRAL instruments with respect to those on RXTE. When combined with earlier archival RXTE results, we find the power law continuum flux and the line-of-sight column depth varied independently, and the iron line flux was essentially unchanging. Taking X-ray spectral measurements from satellite missions since 1970 into account, we discover a variability in the column depth between 1.0x10^23 cm^-2 and 1.5x10^23 cm^-2, and suggest that variations in the edge of a warped accretion disk viewed nearly edge-on might be the cause., Comment: 48 pages, 14 figures, 10 tables, accepted for publication by The Astrophysical Journal