Patrick Schöfer – 2015-10-22

High-resolution Spectroscopy of CARMENCITA objects

Overview Motivation

Aims of the analysis and data sample

Prelude I: Data reduction

Prelude II: Target identification

Analysis and results: Radial velocity

Spectral type

Activity

Summary

Motivation What is CARMENCITA?

• CARMENES Cool dwarf

Information and daTa Archive

• CARMENES input catalog

[http://hades.fis.ucm.es/

carmencita/db.php]

What is CARMENES? • Calar Alto high-Resolution search for M dwarfs with

Exoearths with Near-infrared and optical Échelle

Spectrographs

• German-Spanish collaboration

[http://carmenes.caha.es/]

Motivation Radial velocity method:

planet and star moving around center of mass

different Doppler shifts visible in spectrum

Motivation radial velocity semi-amplitude K:

Earth around Sun: K = 0.09 m s-1

below current detection limit

planet with MP = 2 M⊕ in liquid water zone of

M5 dwarf (T = 3050 K, M⋆ = 0.2 M⊙): K = 1 m s-1

RV method requires high-precision radial velocity

measurements

Motivation Limitations set by the telescope:

only stars with declination δ > -23° observable

J magnitude < 11.5 mag (lower for earlier types)

Limitations set by the method:

no close binary stars (additional RV variation)

no active stars (artificial RV variations caused by

starspots, broad lines due to fast rotation)

Aims of the Analysis and Data Sample

measure radial velocities to find expectation values

and large variations (binaries)

find active stars using the Hα line as activity indicator

Aims of the Analysis and Data Sample

1700 spectra

521 stars (480 CARMENCITA objects)

3 spectrographs (CAFE, FEROS, HRS)

85 stars observed with two spectrographs

Telescope Res. Power

R

λ Range

[Å] # Spectra

CAFE 2.2 m Calar Alto 62,000 3960:9500 903

FEROS 2.2 m ESO, La Silla 48,000 3600:9200 640

HRS 9.2 m HET, Texas 60,000 4200:11000 157

Prelude I: Data Reduction

2D échelle spectrum

1D merged spectrum

elimination of

instrumental effects

Prelude I: Data Reduction 256 CAFE spectra in raw format

REDUCE (Piskunov & Valenti, 2002)

basic image processing

order tracing in flatfield

need to increase contrast

FOX (Zechmeister et al., 2014)

wavelength calibration

manual identification of first lines

normalization using continuum of

reference star (no continuum in

M dwarf spectra)

Prelude II: Target Identification

comparison of CAFE FITS

headers with hand-written

logs

wrong coordinates for 58

spectra

coordinates between

observed target and next

target written after

telescope started moving!

Prelude II: Target Identification

no major problems with FEROS spectra

wrong coordinate system given in HRS FITS headers, different naming convention, but no major problems

Prelude II: Target Identification

Other problems found:

typographical errors (usually easy to find and fix)

only Jhhmms instead of full CARMENCITA identifier

Jhhmms+DDd (ambigous in some cases)

confusion with a nearby star (noticed during analysis)

Analysis and Results: Radial Velocity radial velocity Vr given by Doppler shift

cross-correlation of 3-5 wavelength ranges between

6200 Å and 8600 Å with a synthetic PHOENIX spectrum

Gaussian fit to most significant peak in cross-

correlation function

average of Vr corresponding to valid Gaussian fits

barycentric correction

weighted average if a star was observed more than

once

Analysis and Results: Radial Velocity

good agreement

overall

significant outliers

are active stars

Radial velocities of 79 single stars observed with two spectrographs

Analysis and Results: Radial Velocity

significant outliers

are spectroscopic

binaries

RMSD = 0.69 km s-1

(without binaries)

Comparison of results for non-CARMENCITA objects with literature

Analysis and Results: Radial Velocity

Lam14: same spectra,

same method, but

erroneous barycentric

correction

New14: no trend

PMSU: accuracy

~10 km s-1

others: outliers are

active stars

Comparison of results for CARMENCITA objects with literature

Lam14: Lamert (2014); New14: Newton et al. (2014);

PMSU: Palomar/Michigan State University Survey

Analysis and Results: Radial Velocity 11 stars with significant RV variation over time SB1 candidates

probably more in the sample, because 258 stars were observed only once

33 stars with more than one significant peak in the cross-correlation function SB2 candidates

10 new SB1, 23 new SB2 candidates

Analysis and Results: Radial Velocity

Summary:

matching results from different spectrographs

accuracy ~ 1 km s-1

results for CARMENCITA objects more accurate than

previous work

44 spectroscopic binary candidates among

CARMENCITA objects, 33 of them new

Analysis and Results: Spectral Type

spectral indices converted to spectral type using calibration

data from THE HAMMER (Covey et al., 2007) and linear

interpolation

average of several spectral indices sensitive for M dwarfs

(e.g., Ca I, TiO, VO)

first estimate using 3 indices

different sets of indices for early, medium and late M

dwarfs

Analysis and Results: Spectral Type

later type stars

more interesting

more late (and

faint) targets

observed with HRS

only 14 stars later

than M5.0

Spectral type distribution of CARMENCITA objects in the sample

Analysis and Results: Spectral Type

FEROS: trend

toward earlier types

normalization

issue?

Spectral types of 79 CARMENCITA stars observed with two spectrographs

Analysis and Results: Spectral Type

FEROS and

FEROS+X:

trend toward earlier

types

CAFE and HRS:

no trend

only 4 stars with

difference > 1 subtype

Differences between calculated spectral types and literature

Analysis and Results: Spectral Type

Summary:

bad results for non-CARMENCITA stars because only

spectral indices sensitive for M dwarfs were used

trend toward earlier spectral types for FEROS spectra

typical differences to literature values ≤ 1 subtype

Analysis and Results: Activity pseudo-equivalent width of the Hα line:

negative pEW: visual check whether Hα is in emission

magnetic activity strength:

spectral type used to estimate Teff for χ(Teff)

Analysis and Results: Activity

some significant outliers

significant differences for 42 of 362 stars observed more than once (including stars observed with one spectrograph)

possibly true variation; no correlation of variation with pEW(Hα) or SpT

pEW(Hα) of 79 CARMENCITA stars observed with two spectrographs

Analysis and Results: Activity

higher values from

Lep13, lower values

from AF15

outliers possibly caused

by true variation

no correlation of

differences with

pEW(Hα) or SpT

Comparison of results for CARMENCITA objects with literature

AF15: Alonso-Floriano et al. (2015); Lep13: Lépine et al. (2013);

MR14: Martínez-Rodríguez (2014);

PMSU: Palomar/Michigan State University Survey

Analysis and Results: Activity

[West et al. (2008)]

Fraction of active stars per spectral type

138 active CARMENCITA stars (29% of our sample)

increasing fraction for later spectral types

small sample of M5 or later stars

late M dwarfs are active for a longer period of time (Hawley et al., 1996)

and therefore more likely still active when observed

Analysis and Results: Activity

activity strength

increases with spectral

type for M0.0-M4.5

(except M2.5)

few data points for SpT

earlier than M2.0 and

later than M4.5

Magnetic activity strength of individual stars and median (circles) per spectral type

Analysis and Results: Activity

[Reiners et al. (2012)]

increasing activity related to faster rotation

Analysis and Results: Activity

Summary:

variations of Hα emission for 42 stars, possibly true variability

29% of CARMENCITA stars identified as active

fraction of active stars and median activity strength

increase with the spectral type

Summary

reduction of 256 CAFE spectra and analysis of 1700

CAFE, FEROS and HRS spectra of

480 CARMENCITA objects and 41 other stars

radial velocity measurements with ~1 km s-1 accuracy

33 new spectroscopic binary candidates

spectral types with 1 subtype accuracy

magnetic activity strength of 138 CARMENCITA stars

References Alonso-Floriano, F. J., Morales, J. C., Caballero, J. A et al. 2015, A&A, 577, A128

Covey, K. R., Ivezic, Ž., Schlegel, D. et al. 2007, AJ, 134, 2398–2417

Hawley, S. L., Gizis, J. E. & Reid, I. N. 1996, AJ, 112, 2799

Lamert, A. 2014, MSc thesis, Georg-August-Universität Göttingen, Germany

Lépine, S., Hilton, E. J., Mann, A. W. et al. 2013, AJ, 145, 102

Martínez-Rodríguez, H. 2014, MSc thesis, Universidad Complutense de Madrid, Spain

Newton, E. R., Charbonneau, D., Irwin, J. et al. 2014, AJ, 147, 20

Piskunov, N. E. & Valenti, J. A. 2002, A&A, 385, 1095–1106

Quirrenbach, A., Amado, P. J., Caballero, J. A. et al. 2014, Proc. SPIE, 9147

Reid, I. N., Hawley, S. L. & Gizis, J. E. 1995, AJ, 110, 1838

Reiners, A., Joshi, N. & Goldman, B. 2012, AJ, 143, 93

West, A. A., Hawley, S. L., Bochanski, J. J. et al. 2008, AJ, 135, 785–795

Zechmeister, M., Anglada-Escudé, G. & Reiners, A. 2014, A&A, 561, A59