The eclipsing binary XZ Andromedae (Lawrence E. Hazel)

The eclipsing binary XZ Andromedae

XZ Andromedae (also known as XZ And) is a binary star in the constellation Andromeda. Its maximum apparent visual magnitude is 9.91, but drops down to 12.45 every 1.357 days. Its variability matches the behaviour of Algol variable stars. The primary star of the system has a mass of 3.2 times the sun (2.4 R sun) and has a spectral type A4IV-V, (9500K) meaning that it has intermediate characteristics between a main sequence star and a subgiant one. The secondary is less massive (1.3 M☉) but larger than the primary,(2.6 Rsun) so it's an evolved subgiant star and its spectral type is G5IV (5500K) The secondary component will likely evolve into a white dwarf before the primary leaves the main sequence.

Photometric periods of Algol variables usually match the orbital period of the system. However, in XZ Andromedae, slight period variations have been observed that can be reproduced with three different cycles of 137.5, 36.8 and 11.2 years, respectively. Each of them could be the effect of another faint body orbiting the binary system, but one of the two shorter cycles could also be an effect of magnetic interaction between stars. Its distance from earth is about 1770 LY.

I present here a composite light curve of the eclipse from 238 CCD magnitude estimates from three nights in October and November 2018. Phase values were derived from the time of each magnitude estimate and plotted on the above graph. XZ And is an easily observed eclipsing binary, located about one degree west of Almach (Gamma And). The eclipses are deep and the brightness changes quickly around mid eclipse.

Cloudy Nights

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Distribution of astrophotographers

This table shows the number of distinct astrophotographers who have been assigned and IOTD/TP award compared to the total number of images awarded.
	Distinct awarded users	Total awarded images
Image of the day
Top picks
Top pick nominations

Distribution of subject types

This table shows the distribution of awards per subject type, compared to the popularity of images of that subject type.
	Image of the day	Top pick	Top pick nominations	Total submitted
Deep sky
Solar system
Extremely wide field
Star trails
Northern lights
Noctilucent clouds
Landscape

Distribution of data sources

This table shows the distribution of awards per data source, compared to the popularity of images acquired from that data source.
	Image of the day	Top pick	Top pick nominations	Total submitted
Backyard
Traveller
Own remote observatory
Amateur hosting facility
Public amaeteur data
Professional, scientific grade data
Mix of multiple sources
Other
Unknown

The “AstroBin Image of the Day and Top Picks”, or IOTD/TP, is a long-running system to promote beautiful, interesting, peculiar, or otherwise amazing astrophotographs, with a focus on technical excellence. Learn more.

Submitted The date and time when you submitted this image for IOTD/TP consideration.	...
Views by Submitters (available since September 19th, 2023) Every image is assigned to 50% of available Submitters. In the event that at least 80% of them don't view the image before its time in the IOTD/TP process expires, it's assigned to the other 50% of Submitters and the process begins anew.
Promotions by Submitters When 3 distinct Submitters promote the image, it moves on to the next stage of the process: evaluation for Top Pick status. This requirement, in addition to anonymization of images and distribution to only a subset of them, prevents biases and ensures that the best images are selected.
Promotions by Reviewers When 3 distinct Reviewers promote the image, it moves on to the next stage of the process: evaluation for IOTD status.
Early dismissal Staff members have a lot of images to inspect on a daily basis, and they can dismiss images if they believe they don't meet the requirements for IOTD/TP selection. If an image is dismissed 5 times, it's removed from the process. This streamlines the process and ensures that any bias present in promotions could be overruled by other staff members.

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