Stellar Kinematics Application

Determining ages for brown dwarfs is one of the trickiest aspects in our research, yet a very important one as they allow us to estimate masses. One way many researchers estimate ages is by attempting to match the motions of the object to that of stellar moving groups with known ages. A match in XYZ-UVW space can suggest membership which would imply the brown dwarf is coeval with that group. One can calculate XYZ positions and UVW velocities in Python or your favorite programming language. BDNYC is now hosting a stellar kinematics web application that can do this for you.

Continue reading

BDNYC at AAS 225

BDNYC (and friends) are out in force for the 225th meeting of the American Astronomical Society!

Please come see our posters and talks (mostly on Monday). To whet your appetite, or if you missed them, here are some samplers:

Munazza Alam (Monday, 138.40)
High-Resolution Spectral Analysis of Red & Blue L Dwarfs
AAS225_Munazza_posterSara Camnasio (Monday, 138.39)
Multi-resolution Analysis of Red and Blue L Dwarfs
AAS225_Sara_posterKelle Cruz and Stephanie Douglas (Monday, 138.37)
When good fits go wrong: Untangling Physical Parameters of Warm Brown Dwarfs

AAS225_Stephanie_posterStephanie Douglas (Monday 138.19)
Rotation and Activity in Praesepe and the Hyades

AAS225_Steph_poster2Jackie Faherty (Talk, Monday 130.05)
Clouds in the Coldest Brown Dwarfs

Joe Filippazzo (Monday, 138.34)
Fundamental Parameters for an Age Calibrated Sequence of the Lowest Mass Stars to the Highest Mass Planets
Joe Filippazzo - AAS225

Paige Giorla (Monday, 138.44)
T Dwarf Model Fits for Spectral Standards at Low Spectral Resolution
AAS225_Paige_posterKay Hiranaka (Talk, Monday 130.04D)
Constraining the Properties of the Dust Haze in the Atmospheres of Young Brown Dwarfs

Erini Lambrides (Thursday, 432.02)
Can 3000 IR spectra unveil the connection between AGN and the interstellar medium of their host galaxies?

Emily Rice (Tuesday, 243.02)
STARtorialist: Astronomy Outreach via Fashion, Sci-Fi, & Pop Culture
AAS225_STARtorialistAdric Riedel (Monday, 138.38)
The Young and the Red: What we can learn from Young Brown Dwarfs

Using WriteLaTeX for Collaborative Papers

Update: WriteLaTeX is now Overleaf

We all love Google Docs. It's a functional and convenient way to share and collaboratively edit documents across platforms, time zones, and even continents. We in the BDNYC group use it extensively.

But what if you want to write a scientific paper? Google Docs, as awesome as it is, is not much more than a word processor. We want the internal hyperlinks for sections, figures, tables, and citations, elegant mathematical formulae, well-formatted tables, more control over where and how our components are arranged - in a word, LaTeX. Yes, LaTeX has its own host of problems, but it's very good at what it does.

There are a number of collaborative editing projects out there - Authorea springs to mind. But one of the simpler options out there is actually pretty good: WriteLaTeX.
Continue reading

Using astroquery

If you're like me, you've spent a lot of time downloading a table from VizieR, and then trying to insert it into whatever database or table you are currently using. It's annoying, particularly because VizieR either won't output information in a machine-readable format or won't put an empty line into a massive list of results when there's no match in the catalog.
Astroquery is better. It's a python package affiliated with astropy that can grab data from all your favorite catalog servers (Vizier, SIMBAD, IRSA, NED, etc) directly, and use it; combine that with Astropy's ability (or Python's capacity) to print out tables to files, and it's a lot easier to write a script to do it all for you.

Astroquery is in the Python Package Index, so you can install and update it with
pip install astroquery

You also need the 'requests' module to do the web-interfacing (and Astropy v3); it's available on the Python Package Index and comes preloaded in Anaconda. Using it is simple (this part is almost entirely taken from their pages on using VizieR and IRSA):
Continue reading

Converting Between Decimal Degrees and Hours, Minutes, Seconds

Here's a quick Python snippet I wrote to convert right ascension in decimal degrees to hours, minutes, seconds and declination to (+/-)degrees, minutes, seconds.

def deg2HMS(ra='', dec='', round=False):
  RA, DEC, rs, ds = '', '', '', ''
  if dec:
    if str(dec)[0] == '-':
      ds, dec = '-', abs(dec)
    deg = int(dec)
    decM = abs(int((dec-deg)*60))
    if round:
      decS = int((abs((dec-deg)*60)-decM)*60)
      decS = (abs((dec-deg)*60)-decM)*60
    DEC = '{0}{1} {2} {3}'.format(ds, deg, decM, decS)
  if ra:
    if str(ra)[0] == '-':
      rs, ra = '-', abs(ra)
    raH = int(ra/15)
    raM = int(((ra/15)-raH)*60)
    if round:
      raS = int(((((ra/15)-raH)*60)-raM)*60)
      raS = ((((ra/15)-raH)*60)-raM)*60
    RA = '{0}{1} {2} {3}'.format(rs, raH, raM, raS)
  if ra and dec:
    return (RA, DEC)
    return RA or DEC

For example:
In [1]: f.deg2HMS(ra=66.918277)
Out[1]: '4 27 40.386'

Or even:
In [2]: f.deg2HMS(dec=24.622590)
Out[2]: '+24 37 21.324'

Or if you want to round the seconds, just do:
In [3]: f.deg2HMS(dec=24.622590,round=True)
Out[3]: '+24 37 21'

And to convert hours, minutes and seconds into decimal degrees, we have:

def HMS2deg(ra='', dec=''):
  RA, DEC, rs, ds = '', '', 1, 1
  if dec:
    D, M, S = [float(i) for i in dec.split()]
    if str(D)[0] == '-':
      ds, D = -1, abs(D)
    deg = D + (M/60) + (S/3600)
    DEC = '{0}'.format(deg*ds)
  if ra:
    H, M, S = [float(i) for i in ra.split()]
    if str(H)[0] == '-':
      rs, H = -1, abs(H)
    deg = (H*15) + (M/4) + (S/240)
    RA = '{0}'.format(deg*rs)
  if ra and dec:
    return (RA, DEC)
    return RA or DEC

So we can get back our decimal degrees with:

In [4]: f.HMS2deg(ra='4 27 40.386', dec='+24 37 21.324')
Out[4]: (66.918, 24.622)