Evidence for the Galactic X-ray Bulge II

A mosaic of 5 \ros~PSPC pointed observations in the Galactic plane ($l\sim25^{\circ}$) reveals X-ray shadows in the $0.5-2.0$ keV band cast by distant molecular clouds. The observed on-cloud and off-cloud X-ray fluxes indicate that $\sim15$% and $\sim37$% of the diffuse X-ray background in this direction in the \tq~keV and 1.5 keV bands, respectively, originates behind the molecular gas which is located at $\sim$3 kpc from the Sun. The implication of the derived background X-ray flux beyond the absorbing molecular cloud is consistent with, and lends further support to recent observations of a Galactic X-ray bulge.Comment: 19 pages, 5 figures, 2 table

Optimal Time-Convex Hull under the Lp Metrics

We consider the problem of computing the time-convex hull of a point set under the general $L_p$ metric in the presence of a straight-line highway in the plane. The traveling speed along the highway is assumed to be faster than that off the highway, and the shortest time-path between a distant pair may involve traveling along the highway. The time-convex hull ${TCH}(P)$ of a point set $P$ is the smallest set containing both $P$ and \emph{all} shortest time-paths between any two points in ${TCH}(P)$. In this paper we give an algorithm that computes the time-convex hull under the $L_p$ metric in optimal $O(n\log n)$ time for a given set of $n$ points and a real number $p$ with $1\le p \le \infty$

Forever Young: High Chromospheric Activity in M subdwarfs

We present spectroscopic observations of two halo M subdwarfs which have H alpha emission lines. We show that in both cases close companions are the most likely cause of the chromospheric activity in these old, metal-poor stars. We argue that Gl 781 A's unseen companion is most likely a cool helium white dwarf. Gl 455 is a near-equal-mass M subdwarf (sdM) system. Gl 781 A is rapidly rotating with v sin i = 30 km/s. The properties of the chromospheres and X-ray coronae of these systems are compared to M dwarfs with emission (dMe). The X-ray hardness ratios and optical chromospheric lines emission ratios are consistent with those seen in dMe stars. Comparison to active near-solar metallicity stars indicates that despite their low metallicity ([m/H] = -1/2), the sdMe stars are roughly as active in both X-rays and chromospheric emission. Measured by L_X/L_bol, the activity level of Gl 781 A is no more than a factor of 2.5 subluminous with respect to near-solar metallicity stars.Comment: 16 pages including 1 figure, AASTeX, to appear in May 1998 A.

Doppler images of II Pegasi for 2004-2010

Aims. We study the spot activity of II Peg during the years 2004-2010 to determine long- and short-term changes in the magnetic activity. In a previous study, we detected a persistent active longitude, as well as major changes in the spot configuration occurring on a timescale of shorter than a year. The main objective of this study is to determine whether the same phenomena persist in the star during these six years of spectroscopic monitoring. Methods. The observations were collected with the high-resolution SOFIN spectrograph at the Nordic Optical Telescope. The temperature maps were calculated using a Doppler imaging code based on Tikhonov regularization. Results. We present 12 new temperature maps that show spots distributed mainly over high and intermediate latitudes. In each image, 1-3 main active regions can be identified. The activity level of the star is clearly lower than during our previous study for the years 1994-2002. In contrast to the previous observations, we detect no clear drift of the active regions with respect to the rotation of the star. Conclusions. Having shown a systematic longitudinal drift of the spot-generating mechanism during 1994-2002, the star has clearly switched to a low-activity state for 2004-2010, during which the spot locations appear more random over phase space. It could be that the star is near to a minimum of its activity cycle.Comment: Accepted for publication in Astron. and Astrophys., 8 pages, 5 figure

The effect of the dual Src/Abl kinase inhibitor AZD0530 on Philadelphia positive leukaemia cell lines

Background Imatinib mesylate, a selective inhibitor of Abl tyrosine kinase, is efficacious in treating chronic myeloid leukaemia (CML) and Ph+ acute lymphoblastic leukaemia (ALL). However, most advanced-phase CML and Ph+ ALL patients relapse on Imatinib therapy. Several mechanisms of refractoriness have been reported, including the activation of the Src-family kinases (SFK). Here, we investigated the biological effect of the new specific dual Src/Abl kinase inhibitor AZD0530 on Ph+ leukaemic cells. Methods Cell lines used included BV173 (CML in myeloid blast crisis), SEM t(4;11), Ba/F3 (IL-3 dependent murine pro B), p185Bcr-Abl infected Ba/F3 cells, p185Bcr-Abl mutant infected Ba/F3 cells, SupB15 (Ph+ ALL) and Imatinib resistant SupB15 (RTSupB15) (Ph+ ALL) cells. Cells were exposed to AZD0530 and Imatinib. Cell proliferation, apoptosis, survival and signalling pathways were assessed by dye exclusion, flow cytometry and Western blotting respectively. Results AZD0530 specifically inhibited the growth of, and induced apoptosis in CML and Ph+ ALL cells in a dose dependent manner, but showed only marginal effects on Ph- ALL cells. Resistance to Imatinib due to the mutation Y253F in p185Bcr-Abl was overcome by AZD0530. Combination of AZD0530 and Imatinib showed an additive inhibitory effect on the proliferation of CML BV173 cells but not on Ph+ ALL SupB15 cells. An ongoing transphosphorylation was demonstrated between SFKs and Bcr-Abl. AZD0530 significantly down-regulated the activation of survival signalling pathways in Ph+ cells, resistant or sensitive to Imatinib, with the exception of the RTSupB15. Conclusion Our results indicate that AZD0530 targets both Src and Bcr-Abl kinase activity and reduces the leukaemic maintenance by Bcr-Abl

Evidence for an X-ray Emitting Galactic Bulge: Shadows Cast by Distant Molecular Gas

A mosaic of 7 ROSAT PSPC pointed observations in the direction of (l,b ~ 10,0 deg) reveals deep X-ray shadows in the 0.5-2.0 keV band cast by dense molecular gas. The comparison between the observed on-cloud and off-cloud X-ray fluxes indicates that ~43% of the diffuse X-ray background in this direction in both the 3/4 keV and 1.5 keV bands originates behind the molecular gas, which is located at 2-4 kpc from the Sun. Given the short mean free path of X-rays in the 3/4 keV band in the Galactic plane (~1 kpc assuming an average space density of 1 cm^-3), this large percentage of the observed flux which originates beyond the molecular gas most likely indicates a strong enhancement in the distribution of X-ray emitting gas in the Galactic center region, possibly associated with a Galactic X-ray bulge.Comment: 16 pages LaTex, 2 figures. Accepted for the publication in Astrophysical Journal, Letter

Continuous heating of a giant X-ray flare on Algol

Giant flares can release large amounts of energy within a few days: X-ray emission alone can be up to ten percent of the star's bolometric luminosity. These flares exceed the luminosities of the largest solar flares by many orders of magnitude, which suggests that the underlying physical mechanisms supplying the energy are different from those on the Sun. Magnetic coupling between the components in a binary system or between a young star and an accretion disk has been proposed as a prerequisite for giant flares. Here we report X-ray observations of a giant flare on Algol B, a giant star in an eclipsing binary system. We observed a total X-ray eclipse of the flare, which demonstrates that the plasma was confined to Algol B, and reached a maximum height of 0.6 stellar radii above its surface. The flare occurred around the south pole of Algol B, and energy must have been released continously throughout its life. We conclude that a specific extrastellar environment is not required for the presence of a flare, and that the processes at work are therefore similar to those on the Sun.Comment: Nature, Sept. 2 199

The impact of COVID-19 on cancer care and oncology clinical research: an experts' perspective

The coronavirus disease-19 (COVID-19) pandemic promises to have lasting impacts on cancer clinical trials that could lead to faster patient access to new treatments. In this article, an international panel of oncology experts discusses the lasting impacts of the pandemic on oncology clinical trials and proposes solutions for clinical trial stakeholders, with the support of recent data on worldwide clinical trials collected by IQVIA. These lasting impacts and proposed solutions encompass three topic areas. Firstly, acceleration and implementation of new operational approaches to oncology trials with patient-centric, fully decentralized virtual approaches that include remote assessments via telemedicine and remote devices. Geographical differences in the uptake of remote technology, including telemedicine, are discussed in the article, focusing on the impact of the local adoption of new operational approaches. Secondly, innovative clinical trials. The pandemic has highlighted the need for new trial designs that accelerate research and limit risks and burden for patients while driving optimization of clinical trial objectives and endpoints, while testing is being minimized. Areas of considerations for clinical trial stakeholders are discussed in detail. In addition, the COVID-19 pandemic has exposed the underrepresentation of minority groups in clinical trials; the approach for oncology clinical trials to improve generalizability of efficacy and outcomes data is discussed. Thirdly, a new problem-focused collaborative framework between oncology trial stakeholders, including decision makers, to leverage and further accelerate the innovative approaches in clinical research developed during the COVID-19 pandemic. This could shorten timelines for patient access to new treatments by addressing the cultural and technological barriers to adopting new operational approaches and innovative clinical trials. The role of the different stakeholders is described, with the aim of making COVID-19 a catalyst for positive change in oncology clinical research and eventually in cancer care

The Coronae of AR Lac

We observed the coronally active eclipsing binary, AR Lac, with the High Energy Transmission Grating on Chandra for a total of 97 ks, spaced over five orbits, at quadratures and conjunctions. Contemporaneous and simultaneous EUV spectra and photometry were also obtained with the Extreme Ultraviolet Explorer. Significant variability in both X-ray and EUV fluxes were observed, dominated by at least one X-ray flare and one EUV flare. We saw no evidence of primary or secondary eclipses. X-ray flux modulation was largest at high temperature, indicative of flare heating of coronal plasma. Line widths interpreted in terms of Doppler broadening suggest that both binary stellar components are active. From line fluxes obtained from total integrated spectra, we have modeled the emission measure and abundance distributions. A strong maximum was found in the differential emission measure, characterized by peaks at log T = 6.9 and 7.4, together with a weak but significant cooler maximum near log T=6.2, and a moderately strong hot tail from log T= 7.6-8.2. Coronal abundances have a broad distribution and show no simple correlation with first ionization potential. While the resulting model spectrum generally agrees very well with the observed spectrum, there are some significant discrepancies, especially among the many Fe L-lines. Both the emission measure and abundance distributions are qualitatively similar to prior determinations from other X-ray and ultraviolet spectra, indicating some long-term stability in the overall coronal structure.Comment: 31 pages, 8 figures, 3 tables; Accepted for publication in the Astrophysical Journal (tentatively October 1, 2003

From the Heart of The Ghoul: C and N Abundances in the Corona of Algol B

Chandra Low Energy Transmission Grating Spectrograph observations of Algol have been used to determine the abundances of C and N in the secondary star for the first time. The analysis was performed relative to similar observations of an adopted "standard" star HR 1099. It is demonstrated that HR 1099 and Algol are coronal twins in many respects and that their X-ray spectra are very similar in nearly all details, except for the observed strengths of C and N lines. The H-like transitions of C and N in the coronae of Algol and HR 1099 demonstrate that the surface abundances of Algol B have been strongly modified by CN-processing, as shown earlier by Schmitt & Ness (2002). It is found that N is enhanced in Algol B by a factor of 3 compared to HR 1099. No C lines are detected in the Algol spectrum, indicating a C depletion relative to HR 1099 by a factor of 10 or more. These C and N abundances indicate that Algol B must have lost at least half of its initial mass, and are consistent with predictions of evolutionary models that include non-conservative mass transfer and angular momentum loss through magnetic activity. Little or no dredge-up of material subjected to CN-processing has occurred on the subgiant component of HR 1099. It is concluded that Fe is very likely depleted in the coronae of both Algol and HR 1099 relative to their photospheres by 0.5 dex, and C, N and O by 0.3 dex. Instead, Ne is enhanced by up to 0.5 dex.Comment: 17 pages, 4 figures, ApJ accepte