V900 Mon and Thommes’ Nebula: A New FUor in Monoceros

Bo Reipurth1, Colin Aspin1, and G.H. Herbig2

1: Institute for Astronomy, University of Hawaii at Manoa, 640 N. Aohoku Place, Hilo, HI

96720, USA

reipurth/caa@ifa.hawaii.edu

2: Institute for Astronomy, University of Hawaii at Manoa, 2680 Woodlawn Drive,

Honolulu, HI 96822, USA

herbig@ifa.hawaii.edu

ABSTRACT

Detailed observations of a recently recognized eruptive variable, V900 Mon,

are presented. The star is located in the small cloud L1656, a little-studied

region of modest star formation activity in Monoceros, and is presently at a

magnitude of r∼16, surrounded by a bright compact reflection nebula, where

only a 20th magnitude star was seen on the red first-epoch POSS plate. Optical

spectra show a red absorption-line spectrum not later than mid-K, and the Hα

line and the Na I D12 doublet display prominent P Cygni profiles with massive

absorption troughs indicating a cool outflowing wind. Near-infrared spectra show

deep CO bandhead absorption and pronounced molecular bands of water vapor

indicative of a much cooler object. This spectral appearance is very similar

to that of FU Orionis, except that V900 Mon has a much higher reddening of

AV ∼13 magnitudes. The energy distribution of V900 Mon, compiled from non-

simultaneous observations and thus dependent on possible luminosity changes,

shows that V900 Mon is a Class I protostar with a massive cool envelope. At a

distance of about 1100 pc, V900 Mon has a luminosity of 106 L⊙ in the range

0.55 µm to 160 µm. These data identify V900 Mon as a new member of the rare

class of FU Orionis variables.

Subject headings: stars: formation — stars: low-mass — stars: protostars —

stars: pre-main sequence — stars: individual (V900 Mon)

– 2 –

1. INTRODUCTION

It has long been known that at least some young stars undergo major eruptive events

during early stellar evolution (Herbig 1966, 1977). These events, dubbed FUors by Ambart-

sumian (1971), may represent instabilities in disks (Hartmann & Kenyon 1996) or result from

rapidly rotating young stars near the edge of stability (e.g., Herbig, Petrov, & Duemmler

2003), and the events may be self-triggered (Bell & Lin 1994, Zhu et al. 2009, Vorobyov &

Basu 2010) or caused by the close passage of a companion star (Bonnell & Bastien 1992,

Reipurth & Aspin 2004) or a planet (Lodato & Clarke 2004). About a dozen FUors have

been seen to erupt since the original eruption of FU Orionis in 1936 (Wachmann 1954), and

another dozen objects have been identified which share the peculiar spectral characteristics

of FUors, but for which an eruption has been missed; these objects are known as FUor-like

objects, in analogy to novae and nova-like objects. For a list of FUors and FUor-like objects

and a general overview of their properties, see Reipurth & Aspin (2010).

Because of their potential to reveal extreme and little-understood processes in early stel-

lar evolution and because major developments in observing techniques and instrumentation

have taken place since the earliest known eruptions, it is of great interest when new FUors

are discovered. The most recent new FUor eruption, HBC 722, has generated a flood of

studies (e.g., Semkov et al. 2010, Miller et al. 2011, Kospal et al. 2011, Green et al. 2011,

Lee et al. 2011, Aspin et al. 2012), which taken together represent a major step forward in

our understanding of these rare events.

We here report on a new erupting star, located at α=06:57:22.22, δ=–08:23:17.6 (J2000)

and first noted by the amateur astronomer Jim Thommes (San Diego, California)1, which

our detailed observations demonstrate is a bona fide FUor eruption in a little-known star

forming cloud in Monoceros. It has been designated as V900 Mon (Thommes et al. 2011).

2. OBSERVATIONS

Low-dispersion optical spectroscopic observations were acquired on October 14, 2010

UT with GMOS-N, the Gemini-North facility optical imager and spectrograph (Davies et

al. 1997; Hook et al. 2004). We used the B600 grating with a central wavelength 7500A.

A 0.′′75 wide long-slit was used resulting in a resolving power, R, of ∼1200 (0.45 A pixel−1),

giving a full-width half maximum (FWHM) of unresolved lines of ∼130 km s−1. The total

on-source exposure time was 300 s. All spectra were reduced using the Gemini GMOS iraf

1For further details on the work of Jim Thommes, see http://jthommes.com/Astro/index.htm

– 3 –

package (v1.10). Images were also taken with GMOS-N on the same date using g’, r’, i’, z’

filters, yielding stellar images with FWHM of 0.5”. Exposures totaled 90 sec per filter.

Near-infrared JHK’L’ images were obtained on Jan 2, 2010 UT with Gemini-North and

NIRI. Total on-source exposure times were J=30s, H=32s, K’=7.5s, and L’=90s. The JHK’

photometry was calibrated using FS14, and the L’ photometry using HD40335. The seeing

was 0.7”, and photometry was extracted using Starlink Gaia and a 2.4” radius aperture with

a sky annulus with 3.6-4.8” radius.

Mid-infrared photometry was obtained on Jan 15, 2010 UT using Michelle on the

Gemini-North telescope. At 11.2 µm and 18.5 µm the exposure times were 98 sec and

147 sec, respectively, chopped onto the array. Additionally we extracted photometry from

the Spitzer archive using standard procedures described in Megeath et al. (2004) and Guter-

muth et al. (2004).

NIR spectroscopic observations were acquired using the Gemini-North integral-field unit

(IFU) spectrograph, NIFS (McGregor et al. 2003) on Jan 2, 2010 UT. Observations using

the J, H, and K gratings were taken with total exposure times of 120 s per waveband and

resulted in spectra with R∼5000. Sky observations, taken using an ’ABBA’ offset sequence,

were also acquired. Similar observations of the A0 V star HIP 28056 were taken to allow

the removal of telluric features from the target spectra. The data were reduced using the

Gemini NIFS iraf package (v1.10). The final spectra of the target are the sum of the IFU

pixels lying within an 0.′′5 radius software aperture centered on the targets.

High-dispersion optical spectra were obtained of V900 Mon on Nov 14, 2010 UT using

HIRES (Vogt et al. 1994) at the 10m Keck I telescope. The instrument was configured

with the red cross-disperser and collimator in beam. The C1 decker (0.87”×7.0′′), which

has a projected slit width of 3 pixels, was used, providing a spectral resolution of ∼45,000

(∼6.7 km s−1). Near complete spectral coverage from ∼3600–8000 A was achieved. A 3-chip

mosaic of MIT-LL CCDs with 15 µm pixels were used, binned 2×1. Internal quartz lamps

were used for flat fielding, and ThAr lamp spectra were obtained for wavelength calibration.

The integration time was 1800 s; due to significant extinction, the blue part of the spectrum

was under-exposed. The cross-dispersed spectra were reduced and extracted using standard

tools available in IRAF.

Adaptive optics observations of V900 Mon were performed on Dec 4, 2010 UT at the

10m Keck II telescope using the laser-guided AO system with the IR camera NIRC2 with its

narrow field-of-view camera, providing images of 10.2”×10.2′′. Observations were obtained

in the K- and L-bands, with 1000 images each of 0.18 sec.

Medium-resolution infrared spectra were obtained on April 17, 2011 UT at the 3.0m

– 4 –

NASA Infrared Telescope Facility (IRTF) using SpeX (Rayner et al. 2003). The resolving

power was R∼2000 across the 0.8–2.4 µm range. Total on-source time was 2880 seconds made

up of 45 sec integrations using 2 coadds, 4 cycles and 8 repeats. HR 1807 and HR 2654 were

used as telluric calibrators.

We have used the Wide-Field Grism Spectrograph 2 (WFGS2: Uehara et al. 2004)

installed at the Cassegrain focus of the UH 2.2 m telescope on the night of December 31,

2010 UT. The WFGS2 observations used a 300 line mm−1 grism blazed at 6500 A providing

a dispersion of 3.8 A pixel−1 and a resolving power of 820. The narrowband Hα filter has a

500 A passband centered near 6515 A. The detector for WFGS2 is a Tektronix 2048×2048

CCD with 24 µm pixels. The field of view is ∼11.5′×11.5′. Depending upon seeing conditions,

the limiting measurable equivalent width, W(Hα), is approximately 2 A.

3. RESULTS

3.1. Discovery, Distance, and Surroundings

Figure 1 shows the region around V900 Mon on the first-epoch (epoch 1953.1) red

Palomar Sky Survey and as seen on the discovery image (RGB+Hα, epoch 2009) by Jim

Thommes. Only a barely detectable, slightly extended source is visible in the early image,

whereas a bright nebulosity has emerged in the 2009 image. The 2MASS catalogue lists a

bright near-infrared source (2MASS 06572222-0823176) within less than an arcsecond from

the very faint object visible on the red POSS1 plate. We conclude that the partly embedded

star has undergone a major increase in brightness between 1953 and 2009.

Although located in Monoceros, V900 Mon is not directly associated with the prominent

Mon R2 star forming region, but is located further to the south-east at Galactic coordinates

l=221.07, b=–2.51; this places it towards the small L1656 cloud, which is part of a long

filamentary cloud complex, studied in CO by Maddalena et al. (1986) and Wilson et al.

(2005) and in 13CO by Kim et al. (2004). They suggested that the filament forms a a bridge

between the Mon R2 complex and the CMa OB1 clouds. The stars of the Mon R2 complex

were studied by Herbst & Racine (1976), who determined a distance of 830±50 pc. Lombardi

et al. (2011) suggested a distance of 905±37 pc based on infrared star counts. The distance

to the CMa OB1 complex has been estimated in several studies, and the resulting values

cluster around 1000–1150 pc (see Gregorio-Hetem 2008); Kaltcheva & Hilditch (2000) have

done uvbyβ photometry of OB stars in the region and find a distance of 990±50 pc, while

Lombardi et al. (2011) find a distance of 1150±64 pc. In summary, we adopt a distance of

1100 pc for V900 Mon.

– 5 –

Several compact regions of star formation are located north of V900 Mon. A small nebu-

lous clustering of stars, RNO 78 (Cohen 1980), is found about 4 arcmin north of V900 Mon,

and has been studied by Bica et al. (2003, their object #93), who adopt a distance of

1100 pc.

About 12 arcmin NNW of V900 Mon is the more extensive Lynds Bright Nebula (LBN)

1022, which is a small, largely unstudied, HII region catalogued as [KC97c]G220.9–02.5 by

Kuchar & Clark (1997).

We have searched the L1656 cloud around V900 Mon for Hα emission line stars, and

found three to the north-west, in the general vicinity of RNO 78, the little nebulous group

of stars associated with the source IRAS 06548–0815 (J2000-coordinates):

L1656-Hα1 6:57:05.6 –08:22:02

L1656-Hα2 6:57:14.5 –08:19:55

L1656-Hα3 6:57:14.9 –08:19:17

3.2. Imaging and Photometry

Figure 2a shows an r’-band image of V900 Mon taken at the Gemini-North telescope.

A bright, compact reflection nebula ∼25” long opens up to the SW, and fainter filaments

extend almost an arcminute from the source. The innermost contours are not circular,

suggesting that in the optical we do not directly see the star, but mainly a very compact

reflection nebula. Figure 2b shows a similar J-band image, and here the innermost contours

are circular with a FWHM of 0.8”, compared to 0.7” for nearby stars, suggesting that in the

near-infrared the star itself may be visible.

Table 1 lists g’r’i’z’ photometry in a 1” aperture (with seeing of 0.5”). In a 5” aperture,

the brightness increases significantly: g’=16.20, r’=14.55, i’=13.35, and z’=12.50. This

shows that, at least in the optical, photometry is strongly dependent on aperture.

JHK’L’ photometry obtained on Jan 2, 2010 is listed in Table 2, revealing a bright

near-infrared source. Additional narrowband images in H2 and [FeII] show no evidence for

shocked outflow near the star. Also, we have obtained laser-guided adaptive optics K-band

imaging with NIRC2 on the Keck-II telescope, and find no evidence for any companion at

distances larger than ∼0.1”.

V900 Mon was detected in the all-sky surveys of 2MASS, MSX, WISE, and AKARI,

and the resulting photometry is listed in Table 1 and discussed in Section 4.

– 6 –

3.3. Optical Spectroscopy

The GMOS optical low-resolution spectrum of V900 Mon reveals a red continuum dom-

inated by absorption lines, with no emission present. The only strong lines are Hα and the

far-red Ca II triplet. The clear absence of any TiO bands indicates that the spectrum is

earlier than mid- to late-K. Little other information can be gleaned from the spectrum.

A high-resolution spectrum of V900 Mon, as described in Section 2, has provided further

insights into the nature of the star. Figure 3 shows three prominent lines from this spectrum.

The Na I D1,2 doublet at λλ 5890/5896 display the prominent blueshifted wings that char-

acterize the massive cool winds found in FUors. The spectrum near the Na I D1,2 doublet is

weak in our exposure due to the considerable reddening of the star, so we have binned the

data in this wavelength range by a factor of 5. The λ5890 line has wings reaching a velocity

of ∼140 km/sec, whereas the λ5896 wing is measured to ∼125 km/sec. Absorption features

are seen in the blue wings of both the D1 and D2 lines at vhel = +8, –40, and –80 km s−1;

the deepest point in both lines is at +25 km s−1 and is probably interstellar. Due to the

high noise in this part of the spectrum, these values are lower limits to the width of these

absorption troughs. Within the noise level, no evidence for emission is seen.

The Hα emission line shows a classical P Cygni profile, with a sharp, narrow emission

peak (vhel=+48 km s−1) and a massive blueshifted trough with a width of 400 km/sec.

Structure is seen at the bottom of the trough, with minima at –150 and –9 km s−1 (vhel).

Further to the red, two of the Ca II triplet lines at λλ 8498 and 8662 A are prominent; the

line at λ8542 fell between orders in the spectrum. Figure 3 also shows the λ8662 line. It

displays a prominent P Cygni profile, but because of overlap with the broad Paschen line

P13 at λ8665, it is not possible to measure the extent of the blueshifted trough. The deep

minimum is at (vhel) +12 km s−1 and the shallower minimum is at –34 km s−1, and the

emission peak is at +42 km s−1.

Despite the somewhat underexposed spectrum, Li I λ6707 is clearly detected (EW

0.027 A), confirming the youth of the star. Also the blend centered on λ6497 and domi-

nated by Ba II is evident, a feature that is prominent in FUors and other very low gravity

stars.

3.4. Infrared Spectroscopy

The infrared low-resolution spectrum from 1.2 to 2.4 µm (Fig. 4a) shows prominent

CO bandhead absorption as well as major depressions in the continuum due to water vapor,

clearly indicating a very late-type spectrum, in marked contrast to the optical spectrum.

– 7 –

The appearance is strikingly similar to that of FU Ori itself, except that V900 Mon is much

more reddened. Given the similarity of the two objects, we have dereddened the spectrum of

V900 Mon until the overall slope matches that of FU Ori (Fig. 4a). The best fit is achieved

for an AV of 13 magnitudes. Given that FU Ori has only small reddening, this is therefore

a good estimate of the extinction toward V900 Mon.

4. DISCUSSION

4.1. Photometric history

We have obtained optical and near-infrared photometry of V900 Mon. In order to under-

stand any possible evolution in the light curve of the star, we have compiled all photometry

known to us in Table 1. V900 Mon is too faint (>20 mag) on the red 1953 POSS plate to

yield a meaningful magnitude, but two red plates from 1971 and 1975 show clearly an 18th

magnitude object, suggesting that brightening had commenced by then. The near-infrared

data from DENIS and 2MASS, both from 1998, reveal a bright K-band source, which had

further brightened to K=7.3 when we observed it in early 2010. It is noteworthy that the

DENIS K-magnitude is 0.3 magnitude brighter than the 2MASS K-magnitude obtained 8

months later, so, if real, the overall brightness increase does not seem to be strictly mono-

tonic. Our optical photometry in late 2010 reveal an object with r=16.2, suggesting an

optical brightening between 1953 and 2010 of 4 magnitudes or more in this time interval. In

the decade between 1996/7 and 2006, V900 Mon brightened ∼1.5 mag at 8µm as detected

by MSX and Spitzer. These limited data points do not allow a clear description of the rise

of V900 Mon, but are more consistent with a slow rise-time akin to that of V1515 Cyg than

the sudden rise of FU Ori (Herbig 1977).

4.2. Energy distribution and luminosity

In addition to the optical and near-infrared photometry discussed above, we have used

the WISE and AKARI mid- and far-infrared photometry, obtained in 2010 and 2006, re-

spectively, to plot the observed energy distribution (open circles) of V900 Mon in Figure 4b.

We note that the photometric data points employed are non-simultaneous, obtained between

2006 and 2010, so it is possibly affected by variability. Adopting the AV ∼13 mag extinc-

tion derived from the near-infrared spectrum, we have de-reddened the energy distribution

(crosses) in Figure 4b. The result shows a remarkable similarity to FU Ori itself (black dots),

with the principal exception that V900 Mon has a larger mid-infrared excess. The flat energy

– 8 –

distribution suggests a large range in temperatures of the circumstellar material.

Using optical g’r’i’z’ photometry, near-infrared 2MASS JHK photometry, WISE mid-

infrared photometry, and AKARI mid- and far-infrared photometry, we have measured the

luminosity of V900 Mon as 106 L⊙ at the assumed distance of 1100 pc. This high luminosity

is consistent with the luminosity range found for other FUors; in the same wavelength range

as above, FU Ori has a luminosity of 164 L⊙ at an assumed distance of 450 pc.

4.3. Nature of the source

The data presented in the preceding section reveals an object that shows

• a major brightening sometime in the last half century, possibly still ongoing;

• P Cygni profiles with massive blueshifted troughs at prominent optical lines;

• a spectrum that is increasingly late with increasing wavelength;

• deep infrared CO bandhead absorption;

• a reflection nebula, and lithium in the spectrum.

These are all characteristics which – taken together – uniquely identify V900 Mon as a

new member of the rare FU Orionis class. V900 Mon is remarkably similar to the prototype

object FU Orionis, except that it is much more embedded, and in this respect is more similar

to the FUor V733 Cep (Reipurth et al. 2007). The Spitzer photometry places V900 Mon

among the Class I sources, bordering the Class II sources, see Allen et al (2004).

5. CONCLUSIONS

We have studied a young stellar object associated with the brightening of a compact

reflection nebula, and have reached the following conclusions:

1. The star, now designated as V900 Mon, brightened sometime between 1953 and

the present. A comparison between 2MASS photometry from 1998 and new near-infrared

photometry from 2010 show that the brightening is continuing, suggesting the possibility

that it may not yet have reached a maximum.

2. Assembling photometry from the optical through the far-infrared obtained within

the last 5 years shows an energy distribution with a significant mid- and far-infrared excess,

suggesting the presence of a large cool envelope. V900 Mon is partly embedded in the L1656

– 9 –

cloud, and the Spitzer colors suggest that it is a Class I protostar.

3. A distance of 1100 pc has been adopted, appropriate for a location in eastern Mono-

ceros close to the border of Canis Major. Integrating under the available energy distribution

yields a luminosity of 106 L⊙.

4. In the optical, V900 Mon shows an absorption-line spectrum, including the presence

of lithium, with pronounced blue wings at the Hα, Na I D1,2 doublet, and Ca II triplet lines.

In the near-infrared, CO bandheads are prominently in absorption, and large-scale variations

in the continuum indicate the presence of strong molecular absorption of water.

5. Adaptive optics observations with the Keck-II telescope have not revealed any com-

panions to V900 Mon at separations larger than ∼0.1 arcsec, corresponding to ∼100 AU at

the adopted distance.

6. Overall, V900 Mon shows a remarkable similarity to FU Orionis, except that the

eruption appears to have occurred at an earlier evolutionary stage, when the star is still

partly embedded.

We thank Jim Thommes for providing his image in Figure 1b, Sakib Rasool for alert-

ing us to the website of Jim Thommes, Elza Elek for obtaining the WFGS2 data, Eric

Volquardsen for obtaining the SpeX spectra, and Agnes Kospal for a very helpful referee

report. BR thanks ESO in Garching for hospitality while most of this paper was written.

This work is based on observations made with the Gemini Observatory, which is operated

by the Association of Universities for Research in Astronomy, Inc., and with the W.M. Keck

Observatory, IRTF, the Palomar Schmidt Telescope, 2MASS, MSX, WISE, the Spitzer Space

Telescope, and AKARI. This research has made use of the SIMBAD database, operated at

CDS, Strasbourg, France, and of NASA’s Astrophysics Data System Bibliographic Services.

This work was supported by the NASA Astrobiology Institute under Cooperative Agreement

No. NNA04CC08A. GHH’s contribution to this investigation was partly supported by NSF

grant AST-07-02941

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This preprint was prepared with the AAS LATEX macros v5.2.

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Fig. 1.— (Left:) POSS-I red image showing a 10′ × 10′ field. A very faint star is visible

at the position of V900 Mon. The image was taken on January 17, 1953. (Right:) The

discovery image (RGB+Hα) obtained by Jim Thommes on November 21, 2009. The small

nebula to the upper right is RNO 78.

– 13 –

25 24 23 22 21 6:57:20

22:4

050

-8:2

3:00

1020

3040

5024

:00

R.A (J2000)

DE

C. (

J200

0)

25 24 23 22 21 6:57:20

22:4

050

-8:2

3:00

1020

3040

5024

:00

R.A (J2000)

DE

C. (

J200

0)

Fig. 2.— (Top:) An r′-band image of V900 Mon obtained with GMOS on the Gemini 8m

telescope on Oct 14, 2010 in 0.5” seeing. The contours increase by steps of a factor 2.

(Bottom:) A J-band image obtained with NIRI on the Gemini 8m telescope on Jan. 2, 2010

in 0.7” seeing showing the innermost region of the reflection nebula around V900 Mon.

– 14 –

Fig. 3.— High-resolution spectra of the Na I D1,2 doublet (top), of Hα (middle) and one of

the infrared Ca II lines (bottom) in V900 Mon, obtained with Hires at the Keck I telescope

on Nov. 14, 2010, see the text for details.

– 15 –

Fig. 4.— Top: A low-dispersion near-infrared NIFS spectrum of V900 Mon, showing the

strong CO bandhead absorption and the deep, wide water absorption features, compared to

a SpeX spectrum of FU Ori. Bottom: Energy distribution of V900 Mon, with and without

an extinction of AV =13 mag, compared to FU Orionis.

–16

–

Table 1. Photometry of V900 Mon at Various Epochs and Wavelengths

Filter λ 1971.0 1975.7 ∼1996/7 3Apr1998 1Dec1998 25Nov2006 ∼2006/7 2Jan2010 15Jan2010 2Apr2010 14Oct2010

R′a 0.6 18.96 18.41 . . . . . . . . .

. . . . . . . . . . .

g′b 0.475 . . . . . . . . . . 18.36

. . . . . . . . . . 0.05

r′b 0.622 . . . . . . . . . . 16.24

. . . . . . . . . . 0.05

i′b 0.763 . . . 14.39 . . . . . . 14.73

. . . .03 . . . . . . 0.05

z′b 0.905 . . . . . . . . . . 13.45

. . . . . . . . . . 0.05

Jc 1.25 . . . 11.49 11.50 . . 9.80 . . .

. . . .19 .04 . . .05 . . .

Hc 1.65 . . . . 9.99 . . 8.44 . . .

. . . . .03 . . .05 . . .

K′c 2.2 . . . 8.68 9.00 . . 7.33 . . .

. . . .06 .02 . . .07 . . .

L′c 3.8 . . . . . . . 6.44 . . .

. . . . . . . .09 . . .

I1d 3.6 . . . . . 6.90 . . . . .

. . . . . .01 . . . . .

I2d 4.5 . . . . . 6.16 . . . . .

. . . . . .01 . . . . .

I3d 5.8 . . . . . 5.42 . . . . .

. . . . . .01 . . . . .

I4d 8.0 . . 5.95 . . 4.50 . . . . .

. . .06 . . .01 . . . . .

N′e 11.5 . . . . . . . . 5.12 . .

. . . . . . . . .15 . .

Qe 18.5 . . . . . . . . 1.06 . .

. . . . . . . . . .15 . .

–17

–

Table 1—Continued

Filter λ 1971.0 1975.7 ∼1996/7 3Apr1998 1Dec1998 25Nov2006 ∼2006/7 2Jan2010 15Jan2010 2Apr2010 14Oct2010

W1f 3.4 . . . . . . . . . 6.75 .

. . . . . . . . . .03 .

W2f 4.6 . . . . . . . . . 5.62 .

. . . . . . . . . .03 .

W3f 12 . . . . . . . . . 2.81 .

. . . . . . . . . .02 .

W4f 22 . . . . . . . . . 0.79 .

. . . . . . . . . .01 .

A1g 9 . . . . . . 1.54 . . . .

. . . . . . .05 . . . .

A2g 18 . . . . . . 2.64 . . . .

. . . . . . .06 . . . .

A3g 65 . . . . . . 10.07 . . . .

. . . . . . .63 . . . .

A4g 90 . . . . . . 10.93 . . . .

. . . . . . 1.38 . . . .

A5g 140 . . . . . . 18.52 . . . .

. . . . . . 13.72 . . . .

A6g 160 . . . . . . 14.88 . . . .

. . . . . . 2.98 . . . .

aDSS

bGMOS photometry in a 1” aperture

cDENIS 3Apr1998/2MASS 1Dec1998/NIRI 2Jan2010

dSpitzer IRAC; the 1996/7 value is from MSX at 8.3 µm

eMichelle

fWISE – data obtained April 1/2, 2010

gAKARI – data obtained between Feb 2006 and Aug 2007. AKARI photometry is given in Janskys.