Direct Imaging and Spectroscopy of a Candidate Companion Below/Near

arXiv:1310.4825v2 [astro-ph.SR] 11 Nov 2013 02) hyhv ue oin( jovian super have they 2012a), ouainetnigt lnt eetdb radial- by detected planets to extending population and like a objects bcde ratio 8799 mass HR companion-to-star low 1) groups: 2010; al. et compan- Kratter binary accretion 2011). 2009; low-mass Bromley Boss core very and (by Kenyon as (e.g. planets or ions instability) as disk them or forming advanced for even challenge models significantly objects these Thus, osaetpclyfuda ie( 2008, wide compan- These at 2013). 2011; found al. al. al. typically et et et are Marois Ireland Rameau ions 2008; 2013; al. al. 2010; et 2004; et 2008, Kalas Carson al. 2012a; proper- Lafrenière al. et al. 2010; et et Currie al. the Chauvin tran- et Lagrange and study around 2010; (e.g. radial-velocity companions by and sits undetectable planet-mass stars confirm, self-luminous nearby of identify, ties to way ing ain.BsdsFmlatb(M b Fomalhaut Besides rations. Universität, München, Germany Japan Canada ON, Toronto, Canada St., QC, George St. 50 Toronto, [email protected] of sity hsfr hs opnoscnb iie notwo into divided be can companions these far, Thus ntels eae high-contrast decade, last the In rpittpstuigL using 2018 typeset 13, Preprint June version Draft hyeCurrie Thayne 6 5 4 3 2 1 bevtoso on tr aepoie a provided have stars young of observations nttt o srnm,Uiest fHwi,Pkln,H Pukalani, Hawaii, of University Astronomy, for Institute Kobe, Ludwig-Maximilians Hyogo, München, of Universitäts-Sternwarte University Observatory, Nishi-Harima Montré MD Univer- Montreal, Université Baltimore, de Physique, Dèpartment Institute, de Science Astrophysics, Telescope Space and Astronomy of Department IETIAIGADSETOCP FACNIAECMAINBE COMPANION CANDIDATE A OF SPECTROSCOPY AND IMAGING DIRECT hp niaieo on,lwsraegaiypae-ascompan planet-mass gravity 6–15 surface be low to young, mass of indicative shape unn lnt ieH 79bd n o-as etru-unn b deuterium-burning low-mass, and planet-ma bcde headings: of 8799 Subject dis class HR the like a blurring planets slightly or th latter burning stars to the binary instability, respect like fragmentation/disk with formed disk mass objects and mass separation lowest projected companions 42b’s ROXs planet-mass Given separating nominally limit deuterium-burning olsbtla bet(M8–L0; object substellar cool 2,abnr 0mme fte13Myr-old 1–3 the of member M0 binary a 42B, o-aslt /al dwarfs. L M/early late low-mass opno,psil n ihdtce ria oin h otrec most The motion. orbital at detected background companion id with a candidate source with one point inconsistent a possibly is with astrometry companion, – consistent 42Bb 42Bb’s angle ROXs ROXs position – a companion (2005). faint at a primaries reveals the set from data Each years. 7 over sabcgon bet Os42Bb’s ROXs object. background a is epeetna-nrrdhg-otatiaigpooer and photometry imaging high-contrast near-infrared present We ETRU-UNN II NTEYUGBNR TRSSE,RO SYSTEM, STAR BINARY YOUNG THE IN LIMIT DEUTERIUM-BURNING 1. 1 eata Daemgen Sebastian , β A INTRODUCTION T i opiigteeteaof extrema the comprising b Pic E tl mltajv 5/2/11 v. emulateapj style X M lntr ytm,sas niiul Os42B ROXs individual: stars: systems, planetary J ihrblwtedueimbriglmtadtu lntms rstra or mass planet thus and limit burning deuterium the below either , M ∼ r < ≈ ∼ 0 ′′ . 2 fruhyeulbihns,tog rlmnr nlssindicates analysis preliminary though brightness, equal roughly of 5 4–15 25-300 hrtnRatzka Thorsten M T eff 1 J onDebes John , ietimag- direct K M uree al. et Currie bn L/IFN pcrsoysosRX 2bt ea be to 42Bb ROXs shows spectroscopy VLT/SINFONI -band ≈ AU J rf eso ue1,2018 13, June version Draft H masses. ) 1800–2600 sepa- ) and ABSTRACT al, K I - ρ 2 s ai Lafreniere David , picu trfrigrgo,fo aacollected data from region, star-forming Ophiuchus adpooer ssmlrt ut/luyyoung, dusty/cloudy to similar is photometry band 5 eg Correia Serge , K ,ntabcgon wr tr ihaspectral a with star, dwarf background a not ), 2,abnr tradlkl ebro the of member likely and star M binary a 42B, 18NScod.Lnroclto measurements ( binary and occulation close L1888 a Lunar be the 2008; to between it al. showed et located clouds. Wilking 2011) L1989N/S 1999; al. et Rieke Erickson and (Luhman region n ebro h 1–3 the 1992) Appenzeller of and member (Bouvier and star emitting x-ray bly companions. rare planet-mass of imaged list young the separation, to add wide may that region, star-forming uchus osraieseta yerneo 5M E aae 2013 Mamajek impl (E. 42B K5–M1 ROXs of for range comm.). used type pvt. was spectral conservative calibrator a which in Uncertainties n h alo ouainetnigu obondwarf brown to up extending ( population a 2) masses compris- of and 06214B) tail GSC accretion the (e.g. ing core companions by ratio mass formed high plausibly and velocity rsoyo addt 6–15 candidate a of troscopy dwarfs. fide brown populations, bona mass lowest between these the distinction of and the planets extremes blurring the ages or well-defined clarifying probe with better Companions uncer- could (e.g. 2013). their ratios) al. to masses/mass compan- et uncertain due Some Carson thus, nature (and, 2012). ambiguous ages more al. tain et a Janson have 2011; ions al. et (Currie fRX 2’ icvr rwfo aysources many from draw discovery 42B’s ROXs ( of w-hrso h ytmbihns Rtk ta.2005). al. contributes et (Ratzka component brightness system (M0) the brighter of two-thirds the where 1995) http://www.pas.rochester.edu/$\sim$emamajek/spt/M0V 7 Os4Bwsoiial dnie sa 0 possi- M0, an as identified originally was 42B ROXs nti etr erpr ietiaigadspec- and imaging direct report we Letter, this In 0 pcrsoi tnad sda h time the at used standards spectroscopic M0V 2. M AI YTMPOETE N DATA AND PROPERTIES SYSTEM BASIC & nerlfil pcrsoyo ROXs of spectroscopy field integral 6 os eetmt Os42Bb’s ROXs estimate We ions. 3 sojcsfre yprotostellar by formed objects ss located trbtcnitn ihabound a with consistent but star rmre,i a ersn the represent may it primaries, e 13-15 ociItoh Yoichi , icinbtennon-deuterium between tinction nie ale yRtk tal. et Ratzka by earlier entified ondwarfs. rown n aastrvasasecond a reveals set data ent rmohrsbtla objects. substellar other from M ∼ J y ρ Myr 1.16 n omdb te means other by formed and ) ′′ 4 a Jayawardhana Ray , M ( O/ERTHE LOW/NEAR r r picu star-forming Ophiuchus proj J ∼ opno oROXs to companion S42B XS 0 ≈ digthe ddling ′′ . 5 Smne al. et (Simon 05) 150 AU it ) ρ .txt Ophi- 1 , ). 7 y , 2

Sensitive optical to (sub)millimeter data reveal no clear tion routine to a B9 telluric standard star observed dur- evidence for circumstellar gas or dust (e.g. Cieza et al. ing the same night at similar airmass and with the same 2007; Andrews and Williams 2007). instrumental setup. Its extracted spectrum was divided We initially identified a candidate 3rd member of the by a blackbody curve according to its effective tempera- ROXs 42B system located at a projected separation of ture and its Brackett-γ absorption feature at λ ≈ 2.16 µm ≈ 1′′. 16 as a part of a general search for planet/brown replaced by a straight line along the continuum 11. Fi- dwarf companions in archival Keck, Subaru, and VLT nally, we divided the extracted spectra of ROXS 42B and data (Currie et al. 2012b, 2013a). As we later found, ROXs 42Bb by the corrected telluric standard. Ratzka et al. (2005) identified the same 3rd member as a Figure 1 displays each final image from our photomet- point source from speckle imaging data obtained in 2001. ric data and the collapsed cube from the VLT/SINFONI Although they did not estimate the object’s mass, their spectroscopy, revealing a candidate companion, ROXs K-band flux ratio (0.002 ± 0.001) implied a mass below 42Bb, at r = 1′′. 15–1′′. 17 (labeled or denoted with an the deuterium-burning limit given the age and distance arrow, 3 o’clock position in each panel) at a signal-to- of ρ Oph and standard hot-star planet evolution mod- noise ratio greater than 5. Assuming a distance of 135 els (e.g. Baraffe et al. 2003; Spiegel and Burrows 2012), pc (Mamajek 2008), this angular separation corresponds spurring us to rereduce additional archival data to con- to a projected physical separation of ≈ 150 AU. Further- firm or reject its status as a bound companion and more, the H-band 2011 data set reveal a second candi- determine from multiwavelength photometry and spec- date at r ∼ 0′′. 5 (≈ 65 AU), which has roughly the same troscopy whether its SED is consistent with those for brightness as ROXs 42Bb. The data quality in the other other young directly-imaged planetary-mass compan- epochs is not sufficient to recover this object. We do not ions (e.g. Lafrenière et al. 2008, 2010; Currie et al. 2011; resolve the two primary stars in any data set. Barman et al. 2011). 3. Our combined data set (Table 1) includes Keck/NIRC2 ANALYSIS and Subaru/CIAO near IR imaging and VLT/SINFONI 3.1. Astrometry integral field spectroscopy (IFS) and astrometry from We use gaussian fitting (the IDL Astrolib subroutine Ratzka et al. (2005). The Keck/NIRC2 and Sub- gcntrd.pro) to determine the position of ROXs 42Bb in aru/CIAO data we consider were taken in three epochs each photometric data set, assuming a FWHM equal to between 2005 and 2011 in the H, K or Ks broadband that estimated for the star, and the DAOFIND centroid- filters. The first Keck epoch data and CIAO data were ing routine for the SINFONI IFS data. For NIRC2 as- obtained with (extremely) modest AO corrections, while trometric calibration, we adopt the pixel scale and north the 2011 Keck and VLT images were nearly diffraction position angle offset (9.952 mas pixel−1, P A = -0.252o) limited. All data were obtained in classical imaging, not for narrow camera data from Yelda et al. (2010). For angular differential imaging (Marois et al. 2006), and CIAO data, we adopt a pixel scale of 21.33 mas pixel−1 in various dither/nod patterns to remove the sky back- (Itoh et al. 2005) and a north position angle offset of ground. The field of view was ≈ 10, 20, and 3 arc-seconds 1.14o. on a side for the NIRC2, CIAO, and SINFONI data, re- Figure 2 (left panel) compares ROXs 42Bb’s astrome- spectively. The SINFONI spectral resolution was R ≈ try derived from CIAO and NIRC2 data to the motion 1500. The primary in each data set was unsaturated. expected for a background object assuming a parallax of Basic image processing steps for the photometric data 7.4 mas. We adopt the UCAC4 (Zacharias et al. 2012) followed those taken for IR data that were likewise ob- catalog’s proper motion for ROXs 42B: µα cos(δ), µδ tained in a dither pattern (e.g. Currie et al. 2011). After = -5.9 ± 1.6 mas yr−1, -14.1 ± 1.8 mas yr−1. The mo- sky subtraction, identifying and removing hot/cold/bad tion vector predicted for a background star is inconsistent pixels, correcting each image for distortion (for NIRC2 with ROXs 42Bb’s measured astrometry. The predicted data only) and copying each to larger blank image, we change in position between 2005 and 2011 is ∼ ∆(α, δ) registered the images to a common center following stan- ≈ [40 mas, 100mas] while our astrometry is nearly con- dard methods used before for centroiding unsaturated sistent with no motion at all: the Keck data alone reject PSF cores. Finally, we subtracted off a 2D radial profile a background star hypothesis at more than the 5-σ level. of the primary to remove the halo light from each image, The 2012 SINFONI data are undersampled such that de- median-combined them, and rotated the combined image riving astrometry with a precision on par with NIRC2 to the north-up position8. 9 and CIAO data is challenging. Nevertheless, our derived Using the EsoRex pipeline, we reduced the SINFONI position from these data using the fits header informa- IFS data, performing sky subtraction, combining the tion (r ∼ 1′′. 15 ± 0′′. 03, P A ∼ 270o ± 2o) is consistent data into a spectroscopic cube, correcting for differential with the 2011 Keck astrometry. atmospheric refraction and curvature in the spectra. We A free-floating substellar object at the location of extracted the spectra using a 3-pixel radius annulus using 10 ROXs 42Bb with a similar space motion would be a QFitsView . We applied the same reduction and extrac- rare occurrence. Even assuming twice as many young stellar objects as listed in Wilking et al. (2008) in ≈ 8 The companion is well outside most of the halo light in each photometric data set and just slightly contaminated in the IFS 29 square degree area covering ρ Oph and 10 times as data. Compared to, say, HR 8799 bcde and κ And b, it is at mod- many substellar objects as stellar members instead of an est contrasts. Thus, we did not need to perform sophisticated im- equal amount (Marsh et al. 2010) or fives times fewer age processing techniques (e.g. Lafrenière et al. 2007; Currie et al. 2012a) 11 9 We mitigated contamination of the companion’s spectrum by http://www.eso.org/sci/software/cpl/esorex.html the primary’s diffraction spike and halo by defining sky regions 10 www.mpe.mpg.de/õtt/QFitsView/ along the diffraction spike on both sides of the companion. 3

(Muzic et al. 2012) and that all objects have proper mo- Furthermore, ROXs 42Bb’s spectrum strongly resem- tions indistinguishable from ROXs 42B, the probability bles that for substellar, possibly planet-mass companions ′′ ′′ of contamination on the 10 x10 Keck/NIRC2 field is ≈ CT Cha B and AB Pic B, which have spectral types M8γ −3 5×10 . and L0γ, respectively (Figure 3, top-right panel). Com- Although astrometry obtained with the same instru- pared to GSC0847 B, which has a similar spectral type ment setup (the 2005 and 2011 NIRC2 data) is for- (M9.5γ) but slightly higher inferred mass (15–35 MJ ), mally consistent with no motion considering errors, the the ROXs 42Bb deviates at λ ∼ 2–2.1 µm. The spectrum astrometric drift from epoch to epoch is also consis- deviates from the field, higher surface gravity (log(g) = tent with orbital motion. Between the two Keck/NIRC2 5–5.5) L0 dwarf 2M0345. epochs (∆t ∼ 6 years), ROXs 42Bb changes position by The flatness of the K-band spectrum (the H2(K) in- ≈ 0′′. 0197, yielding an apparent space motion of ≈ 3.2 dex) at 2.17–2.24 µm may be a gravity/age diagnostic 12 mas/year. For a planet at 150 AU on a circular orbit with (Luhman et al. 2004, e.g. ) . ROXs 42Bb’s H2(K) in- a primary mass of ≈ 1 M⊙, the mean positional change dex (∼ 0.95), as defined in Canty et al. (2013), is smaller can be up to 3.8 mas/year for a face-on orbit. While than all but one Bonnefoy et al. library objects, clearly the relative positional changes for ROXs 42Bb suggests distinguishable from that for objects more massive than its orbit may not be viewed face-on, the object could be M ∼ 15 MJ (bottom panel). Thus, ROXs 42Bb’s K- near periastron, admitting a larger apparent motion. band spectral shape provides additional evidence that 3.2. Photometry and Spectroscopy the companion is young and has a low mass/surface gravity. From properties of the best-fitting comparison spec- ROXs 42B is unsaturated in each image, has precise tra, we estimate the following most-likely atmospheric 2MASS photometry (J = 9.906 ± 0.02, H = 9.017 ± properties for ROXs 42Bb: a spectral type of M8γ–L0γ, 0.02, Ks = 8.671 ± 0.02), and is not known to be vari- a surface gravity of log(g) = 3.5–4.5, and a temperature able. Therefore, we flux-calibrated ROXs 42Bb from the of Teff ≈ 1800–2600 K. primary fluxes and our contrast measurements (Table 1). We adopt the Keck photometry to yield mH = 15.88 3.3. Limits on the Age and Mass of ROXs 42Bb ± m ± 0.05 and Ks = 15.00 0.15. Circumstantial evidence suggests that ROXs 42B’s age Following Currie et al. (2011, 2013b), we compare the may be between that of most ρ Oph cloud members and near IR photometry of ROXs 42Bb to the sample of L/T the distributed population. ROXs 42B appears to lie dwarfs compiled by Leggett et al. (2010) and directly- very close to or along a filamentary structure defining M ≤ M imaged planet-mass companions (defined as 15 J ; members of the “ROXs 43A group”, a sub-clump of co- see values listed in Currie et al. 2013b). Prior to these eval very young stars (Makarov 2007) located just outside A ∼ analyses, we derive the extinction of V 1.9 from com- L1989N/S. Assuming that the brighter primary compo- V K paring the primary’s and -band photometry (c.f. nent of ROXs 42Bb is an M0 star and contributes 67% Cieza et al. 2007) to predicted values for pre-main se- of the total system luminosity (c.f. Ratzka et al. 2005), quence M0 stars (Pecaut et al. 2013), adopting the ex- adopting a distance of 135 pc, using the bolometric cor- R tinction law from Cardelli et al. (1989) with V = 3.1. rection13 and effective temperature scale appropriate for Then we deredden the companion and derive absolute H ± young stars from Pecaut et al. (2013), we estimate an age and K-band magnitudes: MH = 9.87 0.05, MKs = ≈ Myr ± of 2.5–3 from the Baraffe et al. (1998) isochrones. 9.13 0.15. If instead ROXs 42Bb is an M1 (K5) star, its estimated The right panel of Figure 2 compares ROXs 42Bb to age is 2 (6) Myr. Performing this analysis for all the H these populations. The companion’s -band luminosity GKM group members located within 3 arc-minutes of is most consistent with late M to early L dwarfs. How- ROXs 42B yields a median age of ≈ 2–4 Myr. ever, like planet-mass companions displayed here, it has ROXs 42B could be older if it is an interloping mem- H K a redder - s color than the field sequence, a feature ber Upper Scorpius association (5 or 11 ± 2 Myr explainable by dustier atmospheres usually associated Preibisch et al. 2002; Pecaut et al. 2012) which is located with low mass/surface gravity objects (c.f. Burrows et al. in close proximity to ρ Oph and has a nearly identical 2006; Currie et al. 2013a). ROXs 42Bb shares a very sim- mean proper motion. On the other hand, ROXs 42B’s ilar color-magnitude diagram position to GSC 06214B position within a filamentary structure, closer proximity and USco CTIO 108B (Ireland et al. 2011; Bejar et al. ≈ to both the ROXs 43A group and the main ρ Oph cloud 2008), two substellar objects with masses of 6–16 complexes, and extinction (A ∼ 1.9) higher than all M M V J and 10–15 J , respectively located in the nearby, but ≈ 5% of all Upper Sco members (none of which are slightly older Upper Scorpius association. If ROXs 42B located close to ROXs 42B) (c.f. Carpenter et al. 2009) ρ is a member of Oph or at least is similarly aged, it makes it an unlikely interloper. is likely lower mass than GCS 06214B and USco CTIO We use the Spiegel and Burrows (2012) at- 108B. mosphere/evolution models and AMES/DUSTY K Our SINFONI -band spectrum of ROXs 42Bb (Fig- (Allard et al. 2001) atmosphere models coupled with ure 3, top panels), when compared to spectra for M and L the Baraffe et al. (2003) evolution models to estimate dwarfs from the Bonnefoy et al. (2013) SINFONI library, the masses of companions with photometry matching provides even stronger evidence that the companion is that of ROXs 42Bb (Figure 4, right panel). Assuming most similar to young objects below/near the deuterium- burning limit. Its spectral shape precludes it from being 12 See also Allers et al. (2007) for gravity-sensitive features at J a stellar companion earlier than ≈ M5–M6 or a fore- and H band ground mid L dwarf but appears consistent with at least 13 Here, we convert from a dereddened V -band magnitude of ≈ some objects near the M/L dwarf transition. 12.27 (c.f. Cieza et al. 2007; Cardelli et al. 1989). 4 an age of ROXs 42B equal to that of the mean age for ions around stars of different masses to the efficiency of embedded regions of ρ Oph (1–2 Myr) the predicted different planet formation mechanisms, concluding that mass for ROXs 42Bb ranges between M ∼ 6 MJ and 9 disk instability is unlikely to explain these objects. Al- MJ . Assuming instead that its age is more similar to though core accretion is inefficient at wide separations that of the lower extinction, distributed population (τ ∼ and challenged in being able to form 5–10 MJ compan- 3 Myr Erickson et al. 2011), the mass of the companion ions, it nevertheless probably gave rise to planets like HR is 11 MJ . If ROXs 42B is an Upper Sco member, ROXs 8799 bcde and β Pic b. 42Bb’s estimated mass is ≈ 13-15 MJ . As depicted in Figure 4, ROXs 42Bb may somewhat Considering these analyses, we conservatively estimate blur the division between bona fide planets and those of a mass range for ROXs 42Bb of 6–15 MJ : planet mass the lowest mass brown dwarfs (i.e. ’planet-mass brown +2 (9−3 MJ ) if it is a bona fide member of the ρ Oph com- dwarfs’). Other means may be required to shed light plex or at/near the deuterium-burning limit nominally on the formation of wide-separation, super jovian-mass separating planets from brown dwarfs if it is an interlop- companions (e.g. Konopacky et al. 2013). The system ing member of Upper Scorpius. may be especially difficult to interpret if the second companion is likewise bound and substellar. Our prelimi- 4. DISCUSSION nary analysis of additional data suggests that this “ROXs We present evidence that ROXs 42B is likely orbited by 42C” is brighter than ROXs 42Bb at J band and fainter at L′, implying significantly bluer colors indicative of a a substellar, possibly planetary-mass companion at rproj ≈ 150 AU. ROXs 42Bb may be valuable in clarifying background object. However, new astrometry is required (or complicating) our understanding of the formation of to demonstrate that it is not bound to the primaries. wide-separation planets and brown dwarfs. To illustrate, We leave these issues, a more detailed investigation in Figure 4 (right panel) we compare ROXs 42Bb’s mass of the host star properties, and further analysis of the ratio to those for the sample of radial-velocity detected atmosphere of ROXs 42Bb to future studies. planets, brown dwarf companions, and directly-imaged planets around HR 8799 and β Pic as in Currie et al. (2011). We thank Eric Mamajek, Christian Marois, Markus As argued by Currie et al. (2011), a gap exists between Janson, Rachael Friesen, Peter Plavchan, and the HR 8799 bcde and β Pic b on one side and brown dwarf anonymous referee for helpful manuscript com- companions on the other, where the former (imaged plan- ments/suggestions and the Subaru and ESO Time ets) may be the high mass ratio, wide separation extrema Allocation Committees for generous allotments of of a population contiguous with RV-detected planets, observing time. This research made use of the Keck Jupiter, and Saturn. Similarly, Janson et al. (2012) com- Observatory Archive (KOA). TC and SD are supported pared limits on the frequency of wide-separation compan- by McLean Postdoctoral Fellowships.

REFERENCES Allard, F., et al., 2001, ApJ, 556, 357 Kratter, K., et al., 2010, ApJ, 710, 1375 Allers, K., et al., 2007, ApJ, 657, 511 Lafrenière, D., et al., 2007, ApJ, 660, 770 Andrews, S. M., Williams, J. P., 2007, ApJ, 671, 1800 Lafrenière, D., et al., 2008, ApJ, 689, 153L Baraffe, I., et al., 1998, A&A, 337, 403 Lafrenière, D., et al., 2010, ApJ, 719, 497 Baraffe, I., et al., 2003, A&A, 402, 701 Lagrange, A.-M., et al., 2010, Science, 329, 57 Barman, T., et al., 2011, ApJ, 735, L39 Leggett, S., et al., 2010, ApJ, 710, 1627 Bejar, V., et al., 2008, ApJ, 673, L185 Luhman, K., Rieke, G., 1999, ApJ, 525, 440 Bonnefoy, M., et al., 2013, A&A in press Luhman, K., Peterson, D., Megeath, S. T., 2004, ApJ, 617, 565 Boss, A., 2011, ApJ, 731, 74 Makarov, V., 2007, ApJ, 670, 1225 Bouvier, J., Appenzeller, I., 1992, A&AS, 92, 481 Mamajek, E., 2008, AN, 329, 10 Burrows, A., et al., 2006, ApJ, 640, 1063 Marois, C., et al., 2006, ApJ, 641, 556 Canty, J., et al., 2013, MNRAS, 435, 2650 Marois, C., et al., 2008, Science, 322, 1348 Cardelli, J., et al., 1989, ApJ, 345, 245 Marois, C., et al., 2010, Nature, 468, 1080 Carpenter, J., et al., 2009, ApJ, 705, 1646 Marsh, K., et al., 2010, ApJ, 719, 550 Carson, J., et al., 2013, ApJ, 763, L32 Muzic, K., et al., 2012, ApJ, 744, 134 Chauvin, G., et al., 2004, A&A, 425, 29L Pecaut, M. J., et al., 2012, ApJ, 746, 154 Cieza, L., et al., 2007, ApJ, 667, 308 Pecaut, M. J., & Mamajek, E. E. 2013, ApJS, 208, 9 Currie, T., Burrows, A., et al., 2011, ApJ, 729, 128 Preibisch, T., et al., 2002, A&A, 124, 404 Currie, T., et al., 2012a, ApJ, 760, L32 Ratzka, T., Kohler, R., Leinert, C., 2005, A&A, 437, 611 Currie, T., et al., 2012b, ApJ, 755, L34 Rameau, J., et al., 2013, ApJLin press, arXiv:1310.7483 Currie, T., et al., 2013a, ApJ, 777, L6 Simon, M., et al., 1995, ApJ, 443, 625 Currie, T., et al., 2013b, ApJ, 776, 15 Spiegel, D., Burrows, A., 2012, ApJ, 745, 174 Eisenhauer, F., et al., 2003, SPIE, 4841, 1548 Wilking, B., Gagne, M., Allen, L., 2008, in the Handbook of Star Erickson, K., et al., 2011, AJ, 142, 140 Forming Regions, Volume II, Astronomical Society of the Ireland, M., et al., 2011, ApJ, 726, 113 Pacific, ed. Bo Reipurth Itoh, Y., et al., 2005, ApJ, 620, 984 Yelda, S., et al., 2010, ApJ, 725, 331 Janson, M., et al., 2012, ApJ, 745, 4 Zacharias, N., et al., 2012, Vizier Online Catalog, 1322, 0 Kalas, P., et al., 2008, Science, 322, 1345 Kenyon, S. J., Bromley, B., 2009, ApJ, 690, L140 Konopacky, Q., et al., 2013, Science, 339, 1398 5

TABLE 1 Observing Log and Companion Measurements

′′ UT Date Program ID Telescope/Camera Filter tint (s) Nimages ∆(mag) r ( ) PA (deg.)

Publisheda 2001-07-01 - NTT/SHARP-I K - - 6.74 ± 0.54 1.137 ± 0.014 268.0 ± 0.3 Archival b 2005-04-16 U55N2 Keck/NIRC2 K 7.5 6 6.30 ± 0.15 1.157 ± 0.010 268.88 ± 0.60 2008-07-19 S08A-074 Subaru/CIAO Ks 9.9 5 6.10 ± 0.20 1.160 ± 0.010 269.67 ± 1.00 2011-06-22 H242N2 Keck/NIRC2 H 10 8 6.86 ± 0.05 1.169 ± 0.005 269.65 ± 0.25 2012-08-11 089.C-0411(A) VLT/SINFONI K IFS 20 3 6.2 ± 0.2 1.15 ± 0.03 270 ± 2

Note. — a) - Presented in Ratzka et al. (2005). b) Data we present for the first time.

Fig. 1.— Images of ROXs 42B from 2011 H-band NIRC2 data (top-left), 2012 VLT/SINFONI Ks band IFS data (top-right, collapsed cube shown), 2005 K-band Keck/NIRC2 data (bottom-left), and 2008 Subaru/CIAO data (bottom-right). The 2011 NIRC2 and 2012 SINFONI data are not smoothed; the older data sets are convolved with a gaussian kernal equal to the image full-width half-maximum of the primary star. All images are rotated ’north-up’. 6

8 M Dwarfs L Dwarfs T Dwarfs Planet-Mass Companions 10 ROXs 42Bb

H 12 M

16 -0.5 0.0 0.5 1.0 1.5 H-Ks

Fig. 2.— (Left) ROXs 42Bb’s astrometry (black squares) from 2001 to 2011 and between just the two Keck/NIRC2 epochs (overplotted green squares) is inconsistent with a background star’s motion (red squares). (Right) ROXs 42Bb’s H/H-Ks position is consistent with cloudy/dusty, L type low surface gravity/mass substellar objects .

Fig. 3.— ROXs 42Bb spectrum (green) compared to other mid M to mid L dwarfs (blue): the target labels list the spectral type, Teff , log(g), and mass (in units of jovian masses). (left) The shape of the continuum is best matched by an objects near the M/L dwarf boundary that (right) are young, have low surface gravities, and masses below/at the deuterium-burning limit (e.g. AB Pic B, CT Cha B). (bottom) ROXs 42Bb’s H2(K) index compared to other objects in the Bonnefoy et al. (2013) library. 7

1.0000

0.1000 * /M

p 0.0100 M

0.0010

0.0001 1 10 100 1000

rp (AU)

Fig. 4.— Mass estimates for ROXs 42Bb assuming the Baraffe et al. (2003); Spiegel and Burrows (2012) luminosity evolution models (left) and its relationship to planets/brown dwarfs (right) assuming that ROXs 42B’s primary star mass is 1 M⊙ (Mprim ≈ 0.65 + 0.35 M⊙)). Given the plausible age for ROXs 42Bb, its most likely mass is 6–15 MJ : 6–11 MJ if it is a member of ρ Oph (solid horizontal error bars) and and 13–15 MJ if it is an Upper Sco (dashed horizontal error bars) member. ROXs 42Bb could be similar to low-mass brown dwarf companions or may fill in the gap between brown dwarfs on one side and radial-velocity and bona fide imaged planets on the other.