Astrophysics and Astronomy



Astrophysics and Astronomy group:

http://www.kavlifoundation.org/sites/default/files/image/astrophysics/microlensing-900.jpgWhenever the light of a background source star passes through the gravitational field of a massive and collinear foreground object, the light is bent toward the center of gravity which causes two (or more) distorted images are formed. Their distance is too small to be separately resolved. Instead of detecting separate images, we receive the combined light of the images which is magnified with respect to the source star itself. This phenomenon is called a ‘graitational microlensing’ event. In the astronomy and astrophysics group of physics department in Isfahan University of Technology, we study different aspects of observing microlensing events.

 

Gravitational microlensing is not only an event, it’s a method for:

1. detecting and characterizing perturbations on the surface of distant stars, located at the Galactic bulge distance. These perturbations can be magnetic field, stellar spots, ellipticity, etc. Gravitational microlensing is a unique method for investigating such small perturbations at very large distances. 

Some related papers:

  1. Sajadian, S., “Detecting stellar spots through polarimetric observations of microlensing events in caustic-crossing”, MNRAS, 2015, 452, 2587 (http://adsabs.harvard.edu/abs/2015MNRAS.452.2587S)
  2. Sajadian, S., “Stellar Rotation Effects in Polarimetric Microlensing”, ApJ, 2016, 825, 152 (http://adsabs.harvard.edu/abs/2016ApJ...825..152S)

2. studying the stellar atmospheres, detecting and characterizing proto-planetary disks, extra solar planets, etc. Photometry, astrometry and polarimetry observations will be useful for these investigations.

Some related papers:

  1. Sajadian, S.,  Rahvar, S.,  “Polarimetric microlensing of circumstellar discs”, MNRAS, 2015, 454, 4429, (http://adsabs.harvard.edu/abs/2015MNRAS.454.4429S)

  2. Sajadian, S., Hundertmark, M., “Polarimetry microlensing of close-in planetary system”, ApJ, 2017, 838, 157 (http://adsabs.harvard.edu/abs/2017ApJ...838..157S)

  3. Sajadian, S.,  Rahvar, S., “illuminating hot Jupiters in caustic crossing”, MNRAS, 2010, 407, 373 (http://adsabs.harvard.edu/abs/2010MNRAS.407..373S)

3. evaluating the theoretical models for Galactic stellar objects. Survey observations toward the Galactic disk or Galactic bulge help to study these models, through comparison of observational outputs with the results of the simulations according to the observational strategies. The numerical calculations are mostly done with Monte-Carlo simulations. 

 

    

Some related papers:

  1. Moniez, M.,  Sajadian, S.,  et al., “Understanding the EROS2 observations towards the spiral arms within a classical Galactic model framework”, A & A, 2017, 604, 124  (http://adsabs.harvard.edu/abs/2017A%26A...604A.124M)

  2. Sajadian, S.,  “Binary microlensin events with Gaia”, AJ, 2015, 149, 147  (http://adsabs.harvard.edu/abs/2015AJ....149..147S)

 

In this group, we also re-reduce the observational data from on-going microlensing events taken with Danish 1.54 m telescope which is located at La Silla observatory in Chile. These observations are done with MiNDSTEp group.

Some related papers:

  • Udalski, A.,  Ryu, Y., -H.,  Sajadian, S.,  “OGLE-2017-BLG-1434Lb: Eighth q < 1 * 10^-4 Mass-Ratio Microlens Planet Confirms Turnover in Planet Mass-Ratio Function”, Submitted (https://arxiv.org/abs/1802.10196)

 

 

 

Related faculty: