Normal Type Ia Research Articles

Abundance stratification in Type Ia supernovae - III. The normal SN 2003du

The element abundance distributions in the ejecta of Type Ia supernova (SN) is studied by modelling a time series of optical spectra of SN 2003du until ~1 year after the explosion. Since SN 2003du is a very normal Type Ia SN both photometrically and spectroscopically, the abundance distribution derived for it can be considered as representative of normal Type Ia SNe. We find that the innermost layers are dominated by stable Fe-group elements, with a total mass of ~ 0.2 Msun, which are synthesized through electron capture. Above the core of stable elements there are thick 56Ni-rich layers. The total mass of 56Ni is 0.65 Msun. The Si- and S-rich layers are located above the 56Ni-rich layers. The dominant element in the outermost layers (M_r > 1.1 Msun, v > 13000 km/s) is O, with a small amount of Si. Little unburned C remains, with an upper limit of 0.016 Msun. The element distributions in the ejecta are moderately mixed, but not fully mixed as seen in three-dimensional deflagration models.

Systematic struggle to eradicate developmental displacement of the hip in newborns in the regions of Kula and Vrbas

Successful treatment of developmental displacement of the hip (DDH) depends on early diagnosis. Clinical screening of all newborns is a useful tool and should be encouraged in everyday practice, because DDH has a high prevalence and significant morbidity. Clinical exam is an important part of early diagnosis, but insufficient. Ultrasound exam is more sensitive in early diagnosis of DDH. Systematic struggle against DDH by means of early detection and treatment begins in neonatology units, and continues in primary healthcare centres. Methodology consists of personal history, clinical exam, ultrasonography and radiography. After these procedures, treatment is advised if necessary. Basically, DDH treatment is atraumatic involving abduction pillow, Von Rosen abduction device, Pavlik harnesses. During 2007 and 2008, screening examination was performed in 769 boys (51.47%) and 725 girls (58.52%), born at the Medical Center "Veljko Vlahovic" in Vrbas. A total of 1,494 neonates or 2,988 hips were examined. Ultrasonographically, a normal type Ia was found in 406 hips (13.60%), intermediate type Ib in 2,014 hips (67.40%), immature type IIa+ in 374 hips (12.50%), unstable type IIg in 39 hips (1.30%), decentering IId in 52 hips (1.70%), and eccentric types III and IV in 35 hips (1.20%). Of 2988 examined hips, normal finding was detected in 2794 (93.50%) and pathological finding (DDH) was found in 194 (6.50%). Ultrasonographical findings were determined according to Graph classification. The frequency of DDH in the regions of Vrbas and Kula above 5% (6.50%) presents a social and medical problem in children of these locations. Eradication, early detection and treatment involve systematic examinations (clinical, sonographical and radiographical) in the first year of life. Treatment has to be initiated in a neonatal unit by atraumatic means. The team work including a gynaecologist, neonatologist and paediatric orthopaedic surgeon is crucial.

THE FAST DECLINING TYPE Ia SUPERNOVA 2003gs, AND EVIDENCE FOR A SIGNIFICANT DISPERSION IN NEAR-INFRARED ABSOLUTE MAGNITUDES OF FAST DECLINERS AT MAXIMUM LIGHT

We obtained optical photometry of SN 2003gs on 49 nights, from 2 to 494 days after T(Bmax). We also obtained near-IR photometry on 21 nights. SN 2003gs was the first fast declining Type Ia SN that has been well observed since SN 1999by. While it was subluminous in optical bands compared to more slowly declining Type Ia SNe, it was not subluminous at maximum light in the near-IR bands. There appears to be a bimodal distribution in the near-IR absolute magnitudes of Type Ia SNe at maximum light. Those that peak in the near-IR after T(Bmax) are subluminous in the all bands. Those that peak in the near-IR prior to T(Bmax), such as SN 2003gs, have effectively the same near-IR absolute magnitudes at maximum light regardless of the decline rate Δm15(B). Near-IR spectral evidence suggests that opacities in the outer layers of SN 2003gs are reduced much earlier than for normal Type Ia SNe. That may allow γ rays that power the luminosity to escape more rapidly and accelerate the decline rate. This conclusion is consistent with the photometric behavior of SN 2003gs in the IR, which indicates a faster than normal decline from approximately normal peak brightness.

COLLISIONS OF WHITE DWARFS AS A NEW PROGENITOR CHANNEL FOR TYPE Ia SUPERNOVAE

We present the results of a systematic numerical study of an alternative progenitor scenario to produce type Ia supernova explosions, which is not restricted to the ignition of a CO white dwarf near the Chandrasekhar mass. In this scenario, a shock-triggered thermonuclear explosion ensues from the collision of two white dwarfs. Consistent modeling of the gas dynamics together with nuclear reactions using both a smoothed particle and a grid-based hydrodynamics code are performed to study the viability of this alternative progenitor channel. We find that shock-triggered ignition and the synthesis of Ni are in fact a natural outcome for moderately massive white dwarf pairs colliding close to head-on. We use a multi-dimensional radiative transfer code to calculate the emergent broadband light curves and spectral time-series of these events. The synthetic spectra and lightcurves compare well with those of normal type Ia supernovae over a similar B-band decline rate and are broadly consistent with the Phillips relation, although a mild dependence on viewing angle is observed due to the asymmetry of the ejected debris. While event rates within galactic centers and globular clusters are found to be much too low to explain the bulk of the type Ia supernovae population, they may be frequent enough to make as much as a one percent contribution to the overall rate. Although these rate estimates are still subject to substantial uncertainties, they do suggest that dense stellar systems should provide upcoming supernova surveys with hundreds of such collision-induced thermonuclear explosions per year.

A CATALOG OF NEAR-INFRARED SPECTRA FROM TYPE Ia SUPERNOVAE

We present forty-one near infrared (NIR, 0.7-2.5 microns) spectra from normal Type Ia supernovae (SNe Ia) obtained at epochs ranging from fourteen days before to seventy-five days with respect to the maximum light date in the V-band. All data were obtained at the IRTF using the SpeX instrument. We identify many spectral features, measure the Doppler velocities, and discuss the chemical distribution of explosion products in SNe Ia. We describe procedures for smoothing data, fitting continua, and measuring absorption features to insure consistency for measurement and analysis. This sample provides the first opportunity to examine and compare a large number of SNe Ia in this wavelength region. NIR data are a rich source of information about explosion products whose signatures are blended or obscured in other spectral regions and NIR observations probe a greater radial depth than optical wavelengths. We analyze similarities and differences in the spectra and we show that the progressive development of spectral features for normal SNe Ia in the NIR is consistent with time. Measured Doppler velocities indicate that burning products in SNe Ia are distributed in distinct layers with no large scale mixing. Carbon is not detected in these data, in agreement with previous results with NIR data establishing very low limits on carbon abundance in SNe Ia. Carbon burning products, O and Mg, are plentiful in the outer layers suggesting that the entire progenitor is burned in the explosion. The data provide a resource for investigations of cross-correlations with other data libraries that may further constrain SN Ia physics and improve the effectiveness of SNe Ia as cosmological distance indicators.

The normal Type Ia SN 2003hv out to very late phases

An extensive dataset for SN 2003hv that covers the flux evolution from maximum light to day +786 is presented. The data are combined with published nebular-phase infrared spectra, and the observations are compared to model light curves and synthetic nebular spectra. SN 2003hv is a normal Type Ia supernova (SN Ia) with photometric and spectroscopic properties consistent with its rarely observed B-band decline-rate parameter, Delta m_15 = 1.61 +- 0.02. The blueshift of the most isolated [Fe II] lines in the nebular-phase optical spectrum appears consistent with those observed in the infrared at similar epochs. At late times there is a prevalent color evolution from the optical toward the near-infrared bands. We present the latest-ever detection of a SN Ia in the near-infrared in Hubble Space Telescope images. The study of the ultraviolet/optical/infrared (UVOIR) light curve reveals that a substantial fraction of the flux is "missing" at late times. Between 300-700 days past maximum brightness, the UVOIR light curve declines linearly following the decay of radioactive Co56, assuming full and instantaneous positron trapping. At 700 days we detect a possible slowdown of the decline in optical bands, mainly in the V band. The data are incompatible with a dramatic infrared catastrophe. However, the idea that an infrared catastrophe occurred in the densest regions before 350 days can explain the missing flux from the UVOIR wavelengths and the flat-topped profiles in the near-infrared. We argue that such a scenario is possible if the ejecta are clumpy. The observations suggest that positrons are most likely trapped in the ejecta.

IMPROVED DISTANCES TO TYPE Ia SUPERNOVAE WITH TWO SPECTROSCOPIC SUBCLASSES

We study the observables of 158 relatively normal Type Ia supernovae (SNe Ia) by dividing them into two groups in terms of the expansion velocity inferred from the absorption minimum of the Si II ?6355 line in their spectra near B-band maximum brightness. One group (Normal) consists of normal SNe Ia populating a narrow strip in the Si II velocity distribution, with an average expansion velocity v = 10, 600 ? 400 km?s?1 near B maximum; the other group (HV) consists of objects with higher velocities, v 11, 800 km s?1. Compared with the Normal group, the HV one shows a narrower distribution in both the peak luminosity and the luminosity decline rate ?m 15. In particular, their B?V colors at maximum brightness are found to be on average redder by ~ 0.1 mag, suggesting that they either are associated with dusty environments or have intrinsically red B?V colors. The HV SNe Ia are also found to prefer a lower extinction ratio RV 1.6 (versus ~ 2.4 for the Normal ones). Applying such an absorption-correction dichotomy to SNe Ia of these two groups remarkably reduces the dispersion in their peak luminosity from 0.178 mag to only 0.125 mag.

THE GOLDEN STANDARD TYPE Ia SUPERNOVA 2005cf: OBSERVATIONS FROM THE ULTRAVIOLET TO THE NEAR-INFRARED WAVEBANDS

We present extensive photometry at ultraviolet (UV), optical, and near-infrared (NIR) wavelengths, as well as dense sampling of optical spectra, for the normal type Ia supernova (SN Ia) 2005cf. From the well-sampled light curves, we find that SN 2005cf reached a B-band maximum at 13.63+/-0.02 mag, with an observed luminosity decline rate dm_15(B) = 1.05+/-0.03 mag. The correlations between the decline rate and various color indexes, recalibrated on the basis of an expanded SN Ia sample, yielded E(B-V)_host=0.09+/-0.03 mag for SN2005cf. The UV photometry was obtained with the HST and the Swift Ultraviolet/Optical Telescope, and the results match each other to within 0.1-0.2 mag. The UV light curves show similar evolution to the broadband U, with an exception in the 2000-2500 Angstrom spectral range (corresponding to the F220W/uvm2 filters), where the light curve appears broader and much fainter than that on either side (likely owing to the intrinsic spectral evolution). Combining the UV data with the ground-based optical and NIR data, we establish the generic UV-optical-NIR bolometric light curve for SN 2005cf and derive the bolometric corrections in the absence of UV and/or NIR data. The overall spectral evolution of SN 2005cf is similar to that of a normal SN Ia, but with variety in the strength and profile of the main feature lines. The spectra at early times displayed strong, detached high-velocity (HV) features in the Ca II H&K doublet and NIR triplet. Similar HV features may exist in the SiII 6355 absorption line which evolved rapidly from a flat-bottomed feature in the earliest phase to a triangular shape one week before maximum, and may be common in other normal SNe Ia. The possible origin of the HV absorption features is briefly discussed (abridged).

Tycho Brahe’s 1572 supernova as a standard type Ia as revealed by its light-echo spectrum

Type Ia supernovae are thermonuclear explosions of white dwarf stars in close binary systems. They play an important role as cosmological distance indicators and have led to the discovery of the accelerated expansion of the Universe. Among the most important unsolved questions about supernovae are how the explosion actually proceeds and whether accretion occurs from a companion or by the merging of two white dwarfs. Tycho Brahe's supernova of 1572 (SN 1572) is thought to be one of the best candidates for a type Ia supernova in the Milky Way. The proximity of the SN 1572 remnant has allowed detailed studies, such as the possible identification of the binary companion, and provides a unique opportunity to test theories of the explosion mechanism and the nature of the progenitor. The determination of the hitherto unknown spectroscopic type of this supernova is crucial in relating these results to the diverse population of type Ia supernovae. Here we report an optical spectrum of Tycho's supernova near maximum brightness, obtained from a scattered-light echo more than four centuries after the direct light from the explosion swept past the Earth. We find that SN 1572 belongs to the majority class of normal type Ia supernovae.

Photometric and spectroscopic study of a highly reddened type Ia supernova SN 2003hx in NGC 2076

We present $UBVRI$ CCD photometry and optical spectra of the type Ia supernova SN 2003hx which appeared in the galaxy NGC 2076, obtained till $\sim$ 146 days after the epoch of $B$ band maximum. The supernova reached at maximum brightness in $B$ band on JD 245 2893 $\pm$ 1.0 with an apparent magnitude of 14.92 $\pm$ 0.01 mag which was estimated by making template fits to the light curves. SN 2003hx is an example of a highly reddened supernova with $E(B-V)$ = 0.56 $\pm$ 0.23. We estimate $R_v$ = 1.97 $\pm$ 0.54 which indicates the small size of dust particles as compared to their galactic counterparts. The luminosity decline rate is $\Delta m_{15}(B)$ = 1.17 $\pm$ 0.12 mag and the absolute $B$ band magnitude obtained from the luminosity versus decline rate relation (Phillips et al. 1999) is $M^B_{max}$ = -19.20 $\pm$ 0.18 mag. The peak bolometric luminosity indicates that $\sim$ 0.66 $M_\odot$ mass of $^{56}$ Ni was ejected by the supernova. The spectral evolution indicates the supernova to be a normal type Ia event.

A search for the progenitors of two TypeIa Supernovae in NGC 1316

Recent evidence of a young progenitor population for many Type-Ia SNe (SNe-Ia) raises the possibility that evolved intermediate-mass progenitor stars may be detected in pre-explosion images. NGC 1316, a radio galaxy in the Fornax cluster, is a prolific producer of SNe-Ia, with four detected since 1980. We analyze Hubble Space Telescope (HST) pre-explosion images of the sites of two of the SNe-Ia that exploded in this galaxy, SN2006dd (a normal Type-Ia) and SN2006mr (likely a subluminous, 1991bg-like, SN-Ia). Astrometric positions are obtained from optical and near-IR ground-based images of the events. We find no candidate point sources at either location, and set upper limits on the flux in B, V, and I from any such progenitors. We also estimate the amount of extinction that could be present, based on analysis of the surface-brightness inhomogeneities in the HST images themselves. At the distance of NGC 1316, the limits correspond to absolute magnitudes of about -5.5, -5.4, and -6.0 mag in M_B, M_V, and M_I, respectively. Comparison to stellar evolution models argues against the presence at the SN sites, 3 years prior to the explosion, of normal stars with initial masses > 6 M_sun at the tip of their asymptotic-giant branch (AGB) evolution, young post-AGB stars that had initial masses > 4 M_sun, and post-red-giant stars of initial masses > 9 M_sun.

Young and Massive Binary Progenitors of Type Ia Supernovae and Their Circumstellar Matter

We present new evolutionary models for Type Ia supernova (SN Ia) progenitors, introducing the mass-stripping effect on a main-sequence (MS) or slightly evolved companion star by winds from a mass-accreting white dwarf (WD). The mass stripping attenuates the rate of mass transfer from the companion to the WD. As a result, a very massive MS companion can avoid forming a common envelope and thus can increase the WD mass up until the SN Ia explosion. Including the mass-stripping effect, we follow binary evolutions of various WD + MS systems and obtain the parameter region in the initial donor mass-orbital period plane in which SNe Ia occur. The newly obtained SN Ia region extends to donor masses of 6-7 M☉, although its extension depends on the efficiency of the mass-stripping effect. The stripped matter would mainly be distributed on the orbital plane and would form very massive circumstellar matter (CSM) around the SN Ia progenitor. This can explain the massive CSM around the Type Ia/IIn(IIa) supernovae SN 2002ic and SN 2005gj, as well as the tenuous CSM around the normal Type Ia supernova SN 2006X. Our new model suggests the presence of very young (108 yr) populations of SNe Ia, which is consistent with recent observational indications of young-population SNe Ia.

The Outermost Ejecta of Type Ia Supernovae

The properties of the highest velocity ejecta of normal Type Ia supernovae (SNe Ia) are studied via models of very early optical spectra of six SNe. At epochs earlier than 1 week before maximum, SNe with a rapidly evolving Si II λ6355 line velocity (HVG) have a larger photospheric velocity than SNe with a slowly evolving Si II λ6355 line velocity (LVG). Since the two groups have comparable luminosities, the temperature at the photosphere is higher in LVG SNe. This explains the different overall spectral appearance of HVG and LVG SNe. However, the variation of the Ca II and Si II absorptions at the highest velocities (v≳ 20,000 km s−1) suggests that additional factors, such as asphericity or different abundances in the progenitor white dwarf, affect the outermost layers. The C II λ6578 line is marginally detected in three LVG SNe, suggesting that LVGs undergo less intense burning. The carbon mass fraction is small, only less than 0.01 near the photosphere, so that he mass of unburned C is only ≲0.01 M☉. Radioactive 56Ni and stable Fe are detected in both LVG and HVG SNe. Different Fe-group abundances in the outer layers may be one of the reasons for spectral diversity among SNe Ia at the earliest times. The diversity among SNe Ia at the earliest phases could also indicate an intrinsic dispersion in the LC width-luminosity relation.

Anterior dynamic ultrasound and graf's examination in neonatal hip instability

Discrepancy between neonatal hip morphology and stability has been reported in the literature. Comparative ultrasound studies on this issue are limited. To compare neonatal hip instability, as assessed by dynamic ultrasound and clinical examination, with acetabular morphology, as assessed by Graf's method. 536 newborn infants with clinical signs of hip instability, ambiguous findings at clinical hip examination, or positive risk factors for DDH were investigated with two ultrasound methods, the Graf method and anterior dynamic ultrasound, at an average age of 12 days. The hips were allocated to three groups according to the Graf result: A, normal (type Ia and b); B, borderline or immature (type IIa); and C, pathologic (type IIc and worse). Graf examination was compared with two diagnostic tests for instability, namely clinical examination by senior pediatric orthopedists and anterior dynamic ultrasound. According to Graf's method, 77% of the hips were normal, 20% borderline/immature, and 3% pathologic. On clinical hip examination, 82% were stable, 14% unstable, and 4% dislocatable. The dynamic ultrasound outcome was 88% stable hips, 10% unstable, and 2% dislocatable. Of the hips considered unstable or dislocatable on dynamic ultrasound, 21% had normal (type I) and 66% immature acetabular morphology according to the Graf method. Of the hips that were stable on dynamic ultrasound, only one (0.1%) was dysplastic according to the Graf method. Graf's examination showed the smallest number of normal hips, but also the fewest pathologic hips, with many indeterminate results that needed follow-up. Acetabular morphology correlated better to stability as assessed by dynamic ultrasound than to the clinical examination results, with fair to moderate agreement. Graf's examination resulted in a large number of indeterminate results that needed follow-up, but when used as the sole criterion for deciding treatment did not lead to a higher treatment rate than when the decision was based on clinical hip examination.

The Evolution of the Peculiar Type Ia Supernova SN 2005hk over 400 Days

UBVRI photometryandmedium-resolution opticalspectroscopyof thepeculiarTypeIasupernova SN2005hkare presentedandanalyzed,coveringthepremaximum phase toaround400daysafter explosion.Thesupernova isfound tobeunderluminouscomparedto‘‘normal’’TypeIasupernovae.Thephotometricandspectroscopicevolutionof SN 2005hk is remarkably similar to the peculiar Type Ia event SN 2002cx. The expansion velocity of the supernova ejecta is found to be lower than normal Type Ia events. The spectra obtained k200 days since explosion do not show the presence of forbidden [Fe ii], [Fe iii], and [Co iii] lines, but are dominated by narrow, permitted Fe ii, NIR Ca ii, and Na i lines with P Cygni profiles. The thermonuclear explosion model with Chandrasekhar mass ejecta and a kinetic energy smaller (EK ¼ 0:3 ;10 51 ergs) than that of canonical Type Ia supernovae is found to well explain the observed bolometric light curve. The mass of 56 Ni synthesized in this explosion is 0.18 M� . The early spectra are successfully modeled with this less energetic model, with some modifications of the abundance distribution. The late spectrum is explained as a combination of a photospheric component and a nebular component. Subject headingg supernovae: general — supernovae: individual (SN 2005hk)

Atypical Thermonuclear Supernovae from Tidally Crushed White Dwarfs

Suggestive evidence has accumulated that intermediate-mass black holes (IMBHs) exist in some globular clusters. As stars diffuse in the cluster, some will inevitable wander sufficiently close to the hole that they suffer tidal disruption. An attractive feature of the IMBH hypothesis is its potential to disrupt not only solar-type stars but also compact white dwarf stars. Attention is given to the fate of white dwarfs that approach the hole close enough to be disrupted and compressed to such an extent that explosive nuclear burning may be triggered. Precise modeling of the dynamics of the encounter, coupled with a nuclear network, allow for a realistic determination of the explosive energy release, and it is argued that ignition is a natural outcome for white dwarfs of all varieties passing well within the tidal radius. Although event rates are estimated to be significantly less than the rate of normal Type Ia supernovae, such encounters may be frequent enough in globular clusters harboring an IMBH to warrant a search for this new class of supernova.

Hydroxychloroquine Diminishes Lymphoproliferation in the Fas Deficient MRL/lpr−/− Murine Model of Autoimmune Lymphoproliferative Syndrome (ALPS).

Hydroxychloroquine (HCQ) is an anti-malarial drug in clinical use for decades that is finding further use as a steroid sparing agent in the treatment of immune disorders such as chronic GVHD, lupus and rheumatoid arthritis. HCQ is a lysosomotropic agent with more recent evidence showing immunomodulatory anti-TNF activity. It is currently being explored as a cytotoxic antineoplastic/antimicrobial agent. Hence, studies were conducted to determine the efficacy of HCQ to control the lymphoproliferation associated with ALPS. ALPS is an inherited disorder of apoptosis leading to lymphoproliferation and autoimmunity. The majority of ALPS patients are classified as Type Ia (>70%), having germline mutations in Fas. Other ALPS patients are classified as Type Ib, II, IV or III, if they have mutations in FasL, casapases, NRAS, or no identified mutations, respectively. They often present with childhood onset autoimmune cytopenias with lymphadenopathy, splenomegaly, increased circulating double negative T cells (DNT; TCRa/b+CD3+CD4−CD8−), defective apoptosis in vitro, and have an increased risk of lymphoma. Similarly, MRL/lpr−/− mice homozygous for Fas mutations develop an ALPS-like disease with massive lymphadenopathy, splenomegaly, hypergammaglobulinemia, autoimmune glomerulonephritis, and expansion of DNT cells secondary to defective lymphocyte apoptosis leading to lymphomagenesis. Currently, there are no proven therapies for the lymphoproliferation underlying ALPS itself. PBMCs from normal controls and ALPS Type Ia patients were cultured in vitro with 0–120 ug/mL HCQ in the presence or absence of 50 uM of the pan-caspase inhibitor Z-VAD-FMK, the caspase 9 inhibitor Z-LEHD-FMK, or the caspase 8 inhibitor Z-IETD-FMK. A dose response was observed with a high degree of cell death noted at 120 ug/mL after 48 hours, with an LD50 of 40 ug/mL. HCQ induced cell death was through a caspase-independent mechanism based on no inhibition of cell death by Z-VAD-FMK, Z-LEHD-FMK, or Z-IETD-FMK. Further preclinical studies were conducted in the MRL/lpr−/− murine model of ALPS. Forty five, 8-week old female MRL/lpr−/− mice were treated with 30 or 60 mg/kg of HCQ by gavage in sterile PBS or PBS alone three days per week for up to 14 weeks. Reductions of the spleen weight (p = 0.045, 437±85 vs 240±27) and cellularity (p = 0.08, 217±32 vs 148±18) were observed in high dose HCQ treated mice compared to controls at 7 weeks. Reductions in cellularity were also noted in the lymph nodes (p = 0.032, 118±33 vs 38±6). There was a trend towards decreasing DNT percentages in the spleen (21±5 vs 14±2), LN (70±4 vs 67±2) and blood (57±6 vs 51±5). Additionally, the CBC showed only marginal reductions in the WBC count (4.2±0.5 vs 3.5±0.3), hematocrit (49±0.3 vs 46±1.0), polymorphonuclear cells (33±3.7 vs 29±3.5) and monocytes (23±3.2 vs 17±2.5). Future studies are planned to more clearly determine the effect of HCQ on autoimmune kidney disease. Based on our in vitro and in vivo data, HCQ is effective at reducing lymphoproliferative activity in Fas deficient MRL/lpr−/− mice. It is being further explored in early phase clinical trials as a lympholytic agent to shrink lymph nodes and abrogate hypersplenism in ALPS patients. HCQ may also prove beneficial for long term use, especially in children, as a steroid sparing agent for treating refractory autoimmune cytopenias in ALPS.

Constraints on Circumstellar Material around the Type Ia Supernova 2007af

Patat et al. recently inferred the existence of circumstellar material around a normal Type Ia supernova (SN Ia) for the first time, finding time-variable Na I D absorption lines in the spectrum of SN 2006X. We present high-resolution spectroscopy of the bright SN Ia 2007af at three epochs and search for variability in any of the Na D absorption components. Over the time range from 4 days before to 24 days after maximum light, we find that the host-galaxy Na D lines appear to be of interstellar rather than circumstellar origin and do not vary down to the level of 18 mÅ (column density of 2 × 1011 cm-2). We limit any circumstellar absorption lines to be weaker than ~10 mÅ (6 × 1010 cm-2). For the case of material distributed in spherically symmetric shells of radius ~1016 cm surrounding the progenitor system, we place an upper limit on the shell mass of ~(3 × 10-8)/X M☉, where X is the Na ionization fraction. We also show that SN 2007af is a photometrically and spectroscopically normal SN Ia. Assuming that the variable Na D lines in SN 2006X came from circumstellar matter, we therefore conclude that either there is a preferred geometry for the detection of variable absorption components in SNe Ia, or SN 2007af and SN 2006X had different types of progenitor systems.

Detection of Circumstellar Material in a Normal Type Ia Supernova

Type Ia supernovae are important cosmological distance indicators. Each of these bright supernovae supposedly results from the thermonuclear explosion of a white dwarf star that, after accreting material from a companion star, exceeds some mass limit, but the true nature of the progenitor star system remains controversial. Here we report the spectroscopic detection of circumstellar material in a normal type Ia supernova explosion. The expansion velocities, densities, and dimensions of the circumstellar envelope indicate that this material was ejected from the progenitor system. In particular, the relatively low expansion velocities suggest that the white dwarf was accreting material from a companion star that was in the red-giant phase at the time of the explosion.

The Peculiar SN 2005hk: Do Some Type Ia Supernovae Explode as Deflagrations?1,1Based in part on observations taken at the Cerro Tololo Inter‐American Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., (AURA) under cooperative agreement with the National Science Foundation. 2,2Based in part on observations obtained with the Apache Point Observatory

ABSTRACTWe present extensive u′g′r′i′BVRIYJHKs photometry and optical spectroscopy of the Type Ia supernova (SN) 2005hk. These data reveal that SN 2005hk was nearly identical in its observed properties to SN 2002cx, which has been called “the most peculiar known Type Ia supernova.” Both supernovae exhibited high‐ionization SN 1991T–like premaximum spectra, yet low peak luminosities like that of SN 1991bg. The spectra reveal that SN 2005hk, like SN 2002cx, exhibited expansion velocities that were roughly half those of typical Type Ia supernovae. The R and I light curves of both supernovae were also peculiar in not displaying the secondary maximum observed for normal Type Ia supernovae. Our YJH photometry of SN 2005hk reveals the same peculiarity in the near‐infrared. By combining our optical and near‐infrared photometry of SN 2005hk with published ultraviolet light curves obtained with the Swift satellite, we are able to construct a bolometric light curve from ∼15 days before to ∼60 days after B maximum. The shape and unusually low peak luminosity of this light curve, plus the low expansion velocities and absence of a secondary maximum at red and near‐infrared wavelengths, are all in reasonable agreement with model calculations of a three‐dimensional deflagration that produces ∼0.2 M⊙ of 56Ni.