# Imaging search for the unseen companion to ε Ind A - Improving the detection limits with 4 μm observations

M. Janson, Daniel Apai, M. Zechmeister, W. Brandner, M. Kürster, M. Kasper, S. Reffert, M. Endl, D. Lafrenière, K. Geißler, S. Hippler, Th Henning

Research output: Contribution to journalArticle

13 Citations (Scopus)

### Abstract

ε Ind A is one of the nearest Sun-like stars, located only 3.6 pc away. It is known to host a binary brown dwarf companion, ε Ind Ba/Bb, at a large projected separation of 6.7 arcmin, but radial velocity measurements imply that an additional, yet unseen, component is present in the system, much closer to ε Ind A. Previously, direct imaging has excluded the presence of any stellar or high-mass brown dwarf companion at small separations, indicating that the unseen companion may be a low-mass brown dwarf or high-mass planet. We present the results of a deep high-contrast imaging search for the companion, using active angular differential imaging at 4 μm, a particularly powerful technique for planet searches around nearby and relatively old stars. We also develop an additional point spread function reference subtraction scheme based on locally optimized combination of images to further enhance the detection limits. No companion is seen in the images, although we are sensitive to significantly lower masses than previously achieved. Combining the imaging data with the known radial velocity trend, we constrain the properties of the companion to within approximately 5-20 Mjup, 10-20 au and i > 20°, unless it is an exotic stellar remnant. The results also imply that the system is probably older than the frequently assumed age of ∼1 Gyr.

Original language English (US) 377-384 8 Monthly Notices of the Royal Astronomical Society 399 1 https://doi.org/10.1111/j.1365-2966.2009.15285.x Published - Oct 2009 Yes

### Fingerprint

planets
planet
stars
velocity measurement
subtraction
sun
trends
detection
trend

### Keywords

• Planetary systems
• Stars: low-mass, brown dwarfs

### ASJC Scopus subject areas

• Space and Planetary Science
• Astronomy and Astrophysics

### Cite this

Imaging search for the unseen companion to ε Ind A - Improving the detection limits with 4 μm observations. / Janson, M.; Apai, Daniel; Zechmeister, M.; Brandner, W.; Kürster, M.; Kasper, M.; Reffert, S.; Endl, M.; Lafrenière, D.; Geißler, K.; Hippler, S.; Henning, Th.

In: Monthly Notices of the Royal Astronomical Society, Vol. 399, No. 1, 10.2009, p. 377-384.

Research output: Contribution to journalArticle

Janson, M, Apai, D, Zechmeister, M, Brandner, W, Kürster, M, Kasper, M, Reffert, S, Endl, M, Lafrenière, D, Geißler, K, Hippler, S & Henning, T 2009, 'Imaging search for the unseen companion to ε Ind A - Improving the detection limits with 4 μm observations', Monthly Notices of the Royal Astronomical Society, vol. 399, no. 1, pp. 377-384. https://doi.org/10.1111/j.1365-2966.2009.15285.x
Janson, M. ; Apai, Daniel ; Zechmeister, M. ; Brandner, W. ; Kürster, M. ; Kasper, M. ; Reffert, S. ; Endl, M. ; Lafrenière, D. ; Geißler, K. ; Hippler, S. ; Henning, Th. / Imaging search for the unseen companion to ε Ind A - Improving the detection limits with 4 μm observations. In: Monthly Notices of the Royal Astronomical Society. 2009 ; Vol. 399, No. 1. pp. 377-384.
@article{09bcd031c43f4e9f92932fc993ca1b8e,
title = "Imaging search for the unseen companion to ε Ind A - Improving the detection limits with 4 μm observations",
abstract = "ε Ind A is one of the nearest Sun-like stars, located only 3.6 pc away. It is known to host a binary brown dwarf companion, ε Ind Ba/Bb, at a large projected separation of 6.7 arcmin, but radial velocity measurements imply that an additional, yet unseen, component is present in the system, much closer to ε Ind A. Previously, direct imaging has excluded the presence of any stellar or high-mass brown dwarf companion at small separations, indicating that the unseen companion may be a low-mass brown dwarf or high-mass planet. We present the results of a deep high-contrast imaging search for the companion, using active angular differential imaging at 4 μm, a particularly powerful technique for planet searches around nearby and relatively old stars. We also develop an additional point spread function reference subtraction scheme based on locally optimized combination of images to further enhance the detection limits. No companion is seen in the images, although we are sensitive to significantly lower masses than previously achieved. Combining the imaging data with the known radial velocity trend, we constrain the properties of the companion to within approximately 5-20 Mjup, 10-20 au and i > 20°, unless it is an exotic stellar remnant. The results also imply that the system is probably older than the frequently assumed age of ∼1 Gyr.",
keywords = "Planetary systems, Stars: low-mass, brown dwarfs",
author = "M. Janson and Daniel Apai and M. Zechmeister and W. Brandner and M. K{\"u}rster and M. Kasper and S. Reffert and M. Endl and D. Lafreni{\`e}re and K. Gei{\ss}ler and S. Hippler and Th Henning",
year = "2009",
month = "10",
doi = "10.1111/j.1365-2966.2009.15285.x",
language = "English (US)",
volume = "399",
pages = "377--384",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "1",

}

TY - JOUR

T1 - Imaging search for the unseen companion to ε Ind A - Improving the detection limits with 4 μm observations

AU - Janson, M.

AU - Apai, Daniel

AU - Zechmeister, M.

AU - Brandner, W.

AU - Kürster, M.

AU - Kasper, M.

AU - Reffert, S.

AU - Endl, M.

AU - Lafrenière, D.

AU - Geißler, K.

AU - Hippler, S.

AU - Henning, Th

PY - 2009/10

Y1 - 2009/10

N2 - ε Ind A is one of the nearest Sun-like stars, located only 3.6 pc away. It is known to host a binary brown dwarf companion, ε Ind Ba/Bb, at a large projected separation of 6.7 arcmin, but radial velocity measurements imply that an additional, yet unseen, component is present in the system, much closer to ε Ind A. Previously, direct imaging has excluded the presence of any stellar or high-mass brown dwarf companion at small separations, indicating that the unseen companion may be a low-mass brown dwarf or high-mass planet. We present the results of a deep high-contrast imaging search for the companion, using active angular differential imaging at 4 μm, a particularly powerful technique for planet searches around nearby and relatively old stars. We also develop an additional point spread function reference subtraction scheme based on locally optimized combination of images to further enhance the detection limits. No companion is seen in the images, although we are sensitive to significantly lower masses than previously achieved. Combining the imaging data with the known radial velocity trend, we constrain the properties of the companion to within approximately 5-20 Mjup, 10-20 au and i > 20°, unless it is an exotic stellar remnant. The results also imply that the system is probably older than the frequently assumed age of ∼1 Gyr.

AB - ε Ind A is one of the nearest Sun-like stars, located only 3.6 pc away. It is known to host a binary brown dwarf companion, ε Ind Ba/Bb, at a large projected separation of 6.7 arcmin, but radial velocity measurements imply that an additional, yet unseen, component is present in the system, much closer to ε Ind A. Previously, direct imaging has excluded the presence of any stellar or high-mass brown dwarf companion at small separations, indicating that the unseen companion may be a low-mass brown dwarf or high-mass planet. We present the results of a deep high-contrast imaging search for the companion, using active angular differential imaging at 4 μm, a particularly powerful technique for planet searches around nearby and relatively old stars. We also develop an additional point spread function reference subtraction scheme based on locally optimized combination of images to further enhance the detection limits. No companion is seen in the images, although we are sensitive to significantly lower masses than previously achieved. Combining the imaging data with the known radial velocity trend, we constrain the properties of the companion to within approximately 5-20 Mjup, 10-20 au and i > 20°, unless it is an exotic stellar remnant. The results also imply that the system is probably older than the frequently assumed age of ∼1 Gyr.

KW - Planetary systems

KW - Stars: low-mass, brown dwarfs

UR - http://www.scopus.com/inward/record.url?scp=70349696174&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=70349696174&partnerID=8YFLogxK

U2 - 10.1111/j.1365-2966.2009.15285.x

DO - 10.1111/j.1365-2966.2009.15285.x

M3 - Article

AN - SCOPUS:70349696174

VL - 399

SP - 377

EP - 384

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 1

ER -