40 research outputs found
Life after eruption, II : the eclipsing old nova V728 Scorpii
The old nova V728 Sco has been recently recovered via photometric and spectroscopic observations, 150 yr after the nova eruption. The spectral properties pointed to a high-inclination system with a comparatively low mass-transfer rate. In this paper, we show that the object is an eclipsing system with an orbital period of 3.32 h. It has enhanced long-term variability that can be interpreted as `stunted' dwarf-nova-type outbursts. Using the ingress and egress times of the eclipsed components we calculate the radius of the central object. The latter turns out to be significantly larger than a white dwarf and we identify it with a hot inner disc. The implications for models on the behaviour of post-novae are discussed
Transient characterization using the Virtual Observatory
Transients can be defined as astrophysical phenomena whose duration is significantly shorter than the typical timescale of the stellar and galactic evolution. Supernovae, novae, gamma-ray burst,..., are some examples of transient events.
Fast, multiwavelength follow-up observations are often required to properly understand the true nature of the transient. Looking for information in astronomical archives can be a complementary approach but, sometimes, these searches are not conducted in an optimal way
We propose here to use the opportunities the Virtual Observatory offers in terms of discovery, access and analysis of astronomical data to improve this approach, and to build an automated workflow to validate and characterise candidate Cataclysmic Variables (CVs) identified among the Gaia Science AlertsThis research has made use of the Spanish Virtual Observatory (https://svo.cab.inta-csic.es) project funded by MCIN/AEI/10.13039/501100011033/ through grant PID2020-112949GB-I00
Transient Heavy Element Absorption Systems in Novae: Episodic Mass Ejection from the Secondary Star
A high-resolution spectroscopic survey of postoutburst novae reveals
short-lived heavy element absorption systems in a majority of novae near
maximum light, having expansion velocities of 400-1000 km/s and velocity
dispersions between 35-350 km/s. A majority of systems are accelerated
outwardly, and they all progressively weaken and disappear over timescales of
weeks. A few of the systems having narrow, deeper absorption reveal a rich
spectrum of singly ionized Sc, Ti, V, Cr, Fe, Sr, Y, Zr, and Ba lines. Analysis
of the richest such system, in Nova LMC 2005, shows the excitation temperature
to be 104 K and elements lighter than Fe to have abundance enhancements over
solar values by up to an order of magnitude. The gas causing the absorption
systems must be circumbinary and its origin is most likely mass ejection from
the secondary star. The absorbing gas pre-exists the outburst and may represent
episodic mass transfer events from the secondary star that initiate the nova
outburst(s). If SNe Ia originate in single degenerate binaries, such absorption
systems could be detectable before maximum lightComment: 19 pages, 6 figures, accepted for publication in the Astrophysical
Journa
Optical microvariability in type 2 quasars
The AGN unified scenario suggests that the type 2 quasars are the obscured counterparts of type 1 quasars where the difference is caused only by the orientation of the object. Optical microvari ability is supposed to arise from the regions which are closer to the supermassive black hole at the center of the AGN. The search for microvariability is an important test for the AGN unified scenario. We present first results from the microvariability campaign carried out at San Pedro Martit observatory. We have targeted three brightest (V mag < 17) type 2 quasars from SDSS. Using analysis of variance (ANOVA), we have detected significant microvariability events in two out of three type 2 quasars we have observe
Photometric type Ia supernova surveys in narrow band filters
We study the characteristics of a narrow band type Ia supernova survey
through simulations based on the upcoming Javalambre Physics of the
accelerating universe Astrophysical Survey (J-PAS). This unique survey has the
capabilities of obtaining distances, redshifts, and the SN type from a single
experiment thereby circumventing the challenges faced by the resource-intensive
spectroscopic follow-up observations. We analyse the flux measurements
signal-to-noise ratio and bias, the supernova typing performance, the ability
to recover light curve parameters given by the SALT2 model, the photometric
redshift precision from type Ia supernova light curves and the effects of
systematic errors on the data. We show that such a survey is not only feasible
but may yield large type Ia supernova samples (up to 250 supernovae at
per month of search) with low core collapse contamination ( per
cent), good precision on the SALT2 parameters (average ,
and ) and on the distance modulus (average
, assuming an intrinsic scatter
), with identified systematic uncertainties
. Moreover, the
filters are narrow enough to detect most spectral features and obtain excellent
photometric redshift precision of , apart from 2 per
cent of outliers. We also present a few strategies for optimising the survey's
outcome. Together with the detailed host galaxy information, narrow band
surveys can be very valuable for the study of supernova rates, spectral feature
relations, intrinsic colour variations and correlations between supernova and
host galaxy properties, all of which are important information for supernova
cosmological applications.Comment: 20 pages, 12 tables and 26 figures. Version accepted by MNRAS, with
results slightly different from previous on
San Pedro Martir observations of microvariability in obscured quasars
Fast brightness variations are a unique tool to probe the innermost regions
of active galactic nuclei (AGN). These variations are called microvariability
or intra-night variability, and this phenomenon has been monitored in samples
of blazars and unobscured AGNs. Detecting optical microvariations in targets
hidden by the obscuring torus is a challenging task because the region
responsible for the variations is hidden from our sight. However, there have
been reports of fast variations in obscured Seyfert galaxies in X-rays, which
rises the question whether microvariations can also be detected in obscured
AGNs in the optical regime. Because the expected variations are very small and
can easily be lost within the noise, the analysis requires a statistical
approach. We report the use of a one-way analysis of variance, ANOVA, with
which we searched for microvariability. ANOVA was successfully employed in
previous studies of unobscured AGNs. As a result, we found microvariable events
during three observing blocks: in two we observed the same object (Mrk 477),
and in another, J0759+5050. The results on Mrk 477 confirm previous findings.
However, since Mrk 477 is quite a peculiar target with hidden broad-line
regions, we cannot rule out the possibility that we have serendipitously chosen
a target prone to variations.Comment: Research note, 5 pages, 2 figures, accepted for publication in
Astronomy and Astrophysic
Lyman break and ultraviolet-selected galaxies at z ~ 1 - II. PACS 100μm/160μm FIR detections
In this work, we report the Photodetector Array Camera and Spectrometer (PACS) 100 μm/160 μm detections of a sample of 42 GALEX-selected and far-infrared (FIR)-detected Lyman break galaxies (LBGs) at z ~ 1 located in the Cosmic Evolution Survey (COSMOS) field and analyse their ultraviolet (UV) to FIR properties. The detection of these LBGs in the FIR indicates that they have a dust content high enough so that its emission can be directly detected. According to a spectral energy distribution (SED) fitting with stellar population templates to their UV-to-near-IR observed photometry, PACS-detected LBGs tend to be bigger (Reff ~ 4.1 kpc), more massive [log (M*/M⊙) ~ 10.7], dustier [Es(B - V) ~ 0.40], redder in the UV continuum (β ~ -0.60) and UV-brighter [log (LUV/L⊙) ~ 10.1] than PACSundetected LBGs. PACS-detected LBGs at z ~ 1 are mostly disc-like galaxies and are located over the green valley and red sequence of the colour-magnitude diagram of galaxies at their redshift. By using their UV and IR emission, we find that PACS-detected LBGs tend to be less dusty and have slightly higher total star formation rates (SFRs) than other PACS-detected UV-selected galaxies within the same redshift range. As a consequence of the selection effect due to the depth of the FIR observations employed, all our PACS-detected LBGs have total IR luminosities, LIR, higher than 1011 L⊙ and thus are luminous IR galaxies. However, none of the PACS-detected LBGs are in the ultra-luminous IR galaxy (ULIRG) regime, LIR =1012 L⊙, where the FIR observations are complete. The finding of ULIRGs-LBGs at higher redshifts (z ~ 3) suggests an evolution of the FIR emission of LBGs with cosmic time. In an IRX-β diagram, PACS-detected LBGs at z~1 tend to be located around the relation for local starburst similarly to other UV-selected PACS-detected galaxies at the same redshift. Consequently, the dust-correction factors obtained with theirUVcontinuum slope allowus to determine their total SFR, unlike at higher redshifts. However, the dust attenuation derived from UV to NIR SED fitting overestimates the total SFR for most of our PACS-detected LBGs in an age-dependent way: the overestimation factor is higher in younger galaxies. This is likely due to the typical degeneracy between dust attenuation and age in the SED fitting with synthetic templates and highlights the importance of the FIR measurements in the analysis of star-forming galaxies at intermediate redshifts.Generalitat Valenciana PROMETEO-2008/132NASA Office of Space Science NNX09AF08GEuropean Southern Observatory LP175.A-0839Junta de AndalucÃa TIC-114, P08-TIC-03531Ministerio de EconomÃa y Competitividad AYA2011- 29517-C03-01, AYA2010-22111-C03-02, AYA2010-1516