Dorota M. Szczygiel

The structure of the broad-line region in active galactic nuclei. I. Reconstructed velocity-delay maps

We present velocity-resolved reverberation results for five active galactic nuclei. We recovered velocity-delay maps using the maximum entropy method for four objects: Mrk 335, Mrk 1501, 3C?120, and PG?2130+099. For the fifth, Mrk 6, we were only able to measure mean time delays in different velocity bins of the H? emission line. The four velocity-delay maps show unique dynamical signatures for each object. For 3C?120, the Balmer lines show kinematic signatures consistent with both an inclined disk and infalling gas, but the He II??4686 emission line is suggestive only of inflow. The Balmer lines in Mrk 335, Mrk 1501, and PG?2130+099 show signs of infalling gas, but the He II emission in Mrk 335 is consistent with an inclined disk. We also see tentative evidence of combined virial motion and infalling gas from the velocity-binned analysis of Mrk 6. The maps for 3C?120 and Mrk 335 are two of the most clearly defined velocity-delay maps to date. These maps constitute a large increase in the number of objects for which we have resolved velocity-delay maps and provide evidence supporting the reliability of reverberation-based black hole mass measurements.

SN 2010jl IN UGC 5189: YET ANOTHER LUMINOUS TYPE IIn SUPERNOVA IN A METAL-POOR GALAXY

We present All-Sky Automated Survey data starting 25 days before the discovery of the recent type IIn SN 2010jl, and we compare its light curve to other luminous IIn SNe, showing that it is a luminous (MI ≈ −20.5) event. Its host galaxy, UGC 5189, has a low gas-phase oxygen abundance (12 + log(O/H) = 8.2 ± 0.1), which reinforces the emerging trend that over-luminous core-collapse supernovae are found in the low-metallicity tail of the galaxy distribution, similar to the known trend for the hosts of long GRBs. We compile oxygen abundances from the literature and from our own observations of UGC 5189, and we present an unpublished spectrum of the luminous type Ic SN 2010gx that we use to estimate its host metallicity. We discuss these in the context of host metallicity trends for different classes of core-collapse objects. The earliest generations of stars are known to be enhanced in [O/Fe] relative to the Solar mixture; it is therefore likely that the stellar progenitors of these overluminous supernovae are even more iron-poor than they are oxygen-poor. A number of mechanisms and massive star progenitor systems have been proposed to explain the most luminous core-collapse supernovae. Any successful theory that tries to explain these very luminous events will need to include the emerging trend that points towards low-metallicity for the massive progenitor stars. This trend for very luminous supernovae to strongly prefer low-metallicity galaxies should be taken into account when considering various aspects of the evolution of the metal-poor early universe, such as enrichment and reionization. Subject headings:

A REVERBERATION LAG FOR THE HIGH-IONIZATION COMPONENT OF THE BROAD-LINE REGION IN THE NARROW-LINE SEYFERT 1 Mrk 335

We present the first results from a detailed analysis of photometric and spectrophotometric data on the narrow-line Seyfert 1 (NLS1) galaxy Mrk 335, collected over a 120 day span in the fall of 2010. From these data we measure the lag in the He II {lambda}4686 broad emission line relative to the optical continuum to be 2.7 {+-} 0.6 days and the lag in the H{beta}{lambda}4861 broad emission line to be 13.9 {+-} 0.9 days. Combined with the line width, the He II lag yields a black hole mass M{sub BH} = (2.6 {+-} 0.8) Multiplication-Sign 10{sup 7} M{sub Sun }. This measurement is consistent with measurements made using the H{beta}{lambda}4861 line, suggesting that the He II emission originates in the same structure as H{beta}, but at a much smaller radius. This constitutes the first robust lag measurement for a high-ionization line in an NLS1 galaxy and supports a scenario in which the He II emission originates from gas in virial motion rather than outflow.

DUST TO DUST: THREE YEARS IN THE EVOLUTION OF THE UNUSUAL SN 2008S

We obtained late-time optical and near-IR imaging of SN 2008S with the Large Binocular Telescope, near-IR data with the Hubble Space Telescope, and mid-IR data with the Spitzer Space Telescope. We find that (1) it is again invisible at optical (UBVR) wavelengths to magnitude limits of approximately 25 mag, (2) while detected in the near-IR (H) at approximately 24.8 mag, it is fading rapidly, and (3) it is still brighter than the progenitor at 3.6 and 4.5 {mu}m in the mid-IR with a slow, steady decline. The IR detections in 2010 December are consistent with dust emission at a blackbody temperature of T {approx_equal} 640 K and a total luminosity of L {approx_equal} 200,000 L{sub Sun }, much higher than the L {approx_equal} 40,000 L{sub Sun} luminosity of the obscured progenitor star. The local environment also shows no evidence for stars significantly more massive than 10 M{sub Sun }, consistent with the progenitor being an 8-10 M{sub Sun} super asymptotic giant branch star.

SDWFS-MT-1: A Self-Obscured Luminous Supernova at z~0.2

We report the discovery of a 6 month long mid-infrared transient, SDWFS-MT-1 (aka SN 2007va), in the Spitzer Deep, Wide-Field Survey of the NOAO Deep Wide-Field Survey Bootes field. The transient, located in a z = 0.19 low-luminosity (M_([4.5]) ≃ −18.6 mag, L/L_⋆ ≃ 0.01) metal-poor (12 + log(O/H) ≃ 7.8) irregular galaxy, peaked at a mid-infrared absolute magnitude of M_([4.5]) ≃ −24.2 in the 4.5μm Spitzer/IRAC band and emitted a total energy of at least 10^(51) erg. The optical emission was likely fainter than the mid-infrared, although our constraints on the optical emission are poor because the transient peaked when the source was “behind” the Sun. The Spitzer data are consistent with emission by a modified blackbody with a temperature of ~1350 K. We rule out a number of scenarios for the origin of the transient such as a Galactic star, active galactic nucleus activity, γ - ray burst, tidal disruption of a star by a black hole, and gravitational lensing. The most plausible scenario is a supernova (SN) exploding inside a massive, optically thick circumstellar medium, composed of multiple shells of previously ejected material. If the proposed scenario is correct, then a significant fraction (~10%) of the most luminous SN may be self-enshrouded by dust not only before but also after the SN occurs. The spectral energy distribution of the progenitor of such an SN would be a slightly cooler version of η Carinae peaking at 20–30 μm.

The absolute magnitude of RRC variables from statistical parallax

We present the first definitive measurement of the absolute magnitude of RR Lyrae c-type variable stars (RRc) determined purely from statistical parallax. We use a sample of 242 RRc variables selected from the All Sky Automated Survey for which high-quality light curves, photometry, and proper motions are available. We obtain high-resolution echelle spectra for these objects to determine radial velocities and abundances as part of the Carnegie RR Lyrae Survey. We find that M V, RRc = 0.59 ? 0.10 at a mean metallicity of [Fe/H] = ?1.59. This is to be compared with previous estimates for RRab stars (M V, RRab = 0.76 ? 0.12) and the only direct measurement of an RRc absolute magnitude (RZ Cephei, M V, RRc = 0.27 ? 0.17). We find the bulk velocity of the halo relative to the Sun to be (W ?, W ?, Wz ) = (12.0, ?209.9, 3.0) km s?1 in the radial, rotational, and vertical directions with dispersions . For the disk, we find (W ?, W ?, Wz ) = (13.0, ?42.0, ?27.3) km s?1 relative to the Sun with dispersions . Finally, as a byproduct of our statistical framework, we are able to demonstrate that UCAC2 proper-motion errors are significantly overestimated as verified by UCAC4.

Discovery of Variability of the Progenitor of SN 2011dh in M 51 Using the Large Binocular Telescope

We show that the candidate progenitor of the core-collapse SN?2011dh in M?51 (8?Mpc away) was fading by 0.039 ? 0.006?mag?yr?1 during the 3?years prior to the supernova, and that this level of variability is moderately unusual for other similar stars in M?51. While there are uncertainties about whether the true progenitor was a blue companion to this candidate, the result illustrates that there are no technical challenges to obtaining fairly high precision light curves of supernova-progenitor systems using ground-based observations of nearby (<10?Mpc)?galaxies with wide-field cameras on 8?m class telescopes. While other sources of variability may dominate, it is even possible to reach into the range of evolution rates required by the quasi-static evolution of the stellar envelope. For M?81, where we have many more epochs and a slightly longer time baseline, our formal 3? sensitivity to slow changes is presently 3?mmag?yr?1 for an MV ?8?mag star. In short, there is no observational barrier to determining whether the variability properties of stars in their last phases of evolution (post-carbon ignition) are different from earlier phases.

Variability of Luminous Stars in the Large Magellanic Cloud Using 10 Years of ASAS Data

Motivated by the detection of a recent outburst of the massive luminous blue variable LMC-R71, which reached an absolute magnitude MV = ?9.3 mag, we undertook a systematic study of the optical variability of 1268 massive stars in the Large Magellanic Cloud, using a recent catalog by Bonanos et?al. as the input. The ASAS All Star Catalog provided well-sampled light curves of these bright stars spanning 10 years. Combining the two catalogs resulted in 599 matches, on which we performed a variability search. We identified 117 variable stars, 38 of which were not known before, despite their brightness and large amplitude of variation. We found 13 periodic stars that we classify as eclipsing binary (EB) stars, 8 of which are newly discovered bright massive EBs composed of OB-type stars. The remaining 104 variables are either semi- or non-periodic, the majority (85) being red supergiants (RSGs). Most (26) of the newly discovered variables in this category are also RSGs with only three B and four O stars.

PRE-DISCOVERY AND FOLLOW-UP OBSERVATIONS OF THE NEARBY SN 2009nr: IMPLICATIONS FOR PROMPT TYPE Ia SUPERNOVAE*

We present photometric and spectroscopic observations of the Type Ia supernova SN 2009nr in UGC 8255 (z = 0.0122). Following the discovery announcement at what turned out to be 10?days after peak, we detected it at V 15.7?mag in data collected by the All-Sky Automated Survey (ASAS) North telescope 2 weeks prior to the peak, and then followed it up with telescopes ranging in aperture from 10 cm to 6.5 m. Using early photometric data available only from ASAS, we find that the supernova is similar to the overluminous Type Ia SN 1991T, with a peak at MV ?19.6?mag, and a slow decline rate of ?m 15(B) 0.95?mag. The early post-maximum spectra closely resemble those of SN 1991T, while the late-time spectra are more similar to those of normal Type Ia supernovae (SNe Ia). Interestingly, SN 2009nr has a projected distance of 13.0?kpc (~4.3 disk scale lengths) from the nucleus of the small star-forming host galaxy UGC 8255. This indicates that the progenitor of SN 2009nr is not associated with a young stellar population, calling into question the conventional association of luminous SNe Ia with the prompt component directly correlated with current star formation. The pre-discovery observation of SN 2009nr using ASAS demonstrates the science utility of high-cadence all sky surveys conducted using small telescopes for the discovery of nearby (d 50?Mpc) supernovae.

SN 2010U: A LUMINOUS NOVA IN NGC 4214*

The luminosity, light curve, post-maximum spectrum, and lack of a progenitor on deep pre-outburst images suggest that SN 2010U was a luminous, fast nova. Its outburst magnitude is consistent with that for a fast nova using the maximum magnitude-rate of decline relationship for classical novae.