arXiv subjects

Massimo Della Valle

Publications and source records attributed to Massimo Della Valle.

94 records · Page 6Linked to original sources

arXiv2002

Rebirth of Novae as Distance Indicators Due to Efficient Large Telescopes

Nova outbursts are the result of strong thermonuclear runaways on the surface of a white dwarf accreting Hydrogen-rich material from a small mass companion. These giant explosions cause the star to increase its brightness by hundreds of thousands of times then making these objects powerful standard candles useful to measure the extragalactic distances.We have used the Very Large Telescope, located in the Chilean Atacama desert, to search for novae in NGC 1316--an early type galaxy in the Fornax cluster. We discovered 4 novae with 3h of observing time. The use of 8-10m class telescopes coupled with new detectors, can dramatically improve the efficiency of nova searches in extragalactic systems.

astro-ph↗

arXiv1998

Globular Cluster Calibration of the Peak Brightness of the Type Ia Supernova 1992A and the Value of Ho

We have determined the absolute magnitude at maximum light of SN 1992A by using the turn-over magnitude of the Globular Cluster Luminosity Function of its parent galaxy, NGC 1380. A recalibration of the peak of the turn-over magnitude of the Milky Way clusters using the latest HIPPARCOS results has been made with an assessment of the complete random and systematic error budget. The following results emerge: a distance to NGC 1380 of 18.6 +/- 1.4 Mpc, corresponding to (m-M)=31.35 +/- 0.16, and an absolute magnitude of SN 1992A at maximum of M_B(max)= -18.79 +/- 0.16. Taken at face value, SN 1992A seems to be more than half a magnitude fainter than the other SNeI-a for which accurate distances exist. We discuss the implications of this result and present possible explanations. We also discuss the Phillips'(1993) relationship between rate of decline and the absolute magnitude at maximum, on the basis of 9 SNeI-a, whose individual distances have been obtained with Cepheids and the Globular Cluster Luminosity Function. The new calibration of this relationship, applied to the most distant SNe of the Calan-Tololo survey, yields Ho=62 +/- 6 km/s/Mpc.

astro-ph↗

arXiv1997

A possible orbital period for the dwarf nova V1101 Aql

We have performed a Discrete Fourier Transform on 136 CCD B, V and R frames of the Z Cam-type dwarf nova V1101 Aql. Our analysis indicates as possible orbital period P_orb =3.46 hours, though we cannot exclude the alias at 4.00 hours. We estimate the distance to the system to be about 300 pc. We possibly discovered a bright bow-shaped nebulosity around the object.

astro-ph↗

arXiv1997

Halo and Bulge/Disk globular clusters in the S0 galaxy NGC 1380

We investigated the globular cluster system of the S0 galaxy NGC 1380 in the Fornax cluster with deep BVR photometry. We identified two, presumably old, populations of globular clusters. The blue globular clusters seem to be counterparts to the halo globular clusters in our Milky Way. They have comparable colors and magnitudes, are spherically distributed around the elliptical galaxy but have a very flat surface density profile. The red population follows the stellar light in ellipticity and position angle, has a similar magnitude distribution to the blue clusters, and a surface density profile comparable to that of globular clusters in other Fornax ellipticals. From their colors the red clusters appear slightly more metal rich then the metal rich globular clusters in the Milky way. We associate this red population with the bulge and disk of NGC 1380. While these two populations are compatible with a merger formation, we unfortunately see no other hint in favor nor against a past merger event in this galaxy. This would be the first identification of halo and bulge globular clusters in an early--type galaxy by their colors and spatial distribution, and could hint to the presence of halo and bulge globular clusters in all galaxies.

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