Universidad de Alicante
Web page of the Alicante clusters
Over the past twenty years, the Stellar Astrophysics Group at the University of Alicante has found a number of new open clusters. Following the astronomical tradition, we have named them after the institution were we work. These clusters (with one exception) had never been identified before. This means that they are not easy to find.
The Alicante clusters come in two main groups. Many of them are small stellar groupings found in the neighbourhood of other clusters or inside OB associations. Most of them were found during an exploration of the Outer Galaxy (Negueruela & Marco 2003). They are generally quite small, but surprisingly contain very massive stars (especially, Alicante 1, 2, 3 & 11).
The second main group (Alicante 7 to 10) are clusters of red supergiants in the region of Scutum. This is an area of very high obscuration, owing to the presence of thick dust clouds in the Scutum-Crux Arm. Associated to one of those clouds is the star-forming cluster Alicante 6. Beyond these clouds lies one of the largest areas of recent star formation in the Milky Way. Because of high distance and obscuration, clusters in this area can only be identified by the presence of very bright red supergiants.
To access information on a given cluster, use one of the buttons below.
Alicante 1
Primary Reference
“Stellar tracers of the Cygnus Arm. II. A young open cluster in Camelopardalis OB3” Negueruela & Marco (2008), A&A 492, 441
- Strömgren photometry
- Spectra
Main features
- Young open cluster in the Cam OB3 association
- Age not measured, but < 3 Ma
- Peculiar IMF with some very massive stars in small cluster
- Contains the very massive eclipsing binary MY Cam (Lorenzo et al. 2015, A&A 572, A110)
Alicante 2
Primary Reference
Not published as such, but described in “A WN4 companion to BD +62°2296 in Cas OB5“, Negueruela (2004), A&A 408, 689
- Spectra of three brightest members only
- Listed as Negueruela 1 in Wilton Dias‘ open cluster database
Main features
- Young open cluster in the Cas OB5 association
- Age unconstrained, but likely between 5 and 10 Ma.
- Peculiar IMF with some very massive stars in a very small cluster
- Contains BD +62°2296, which consists of a very luminous blue supergiant and a Wolf-Rayet star.
The cluster is very well seen in Gaia DR2 data, but the astrometric solution for the WR is poor. The average parallax is ~0.28 milliarcsec.
Alicante 3
Primary Reference
Found in 2001, but never published.
Listed in SIMBAD as Stock 17, after Pandey (1986) BASI 14, 20, but the nominal position of Stock 17 lies about 14′ away and likely refers to the group formed by LS I +61º 43, 45 & 46.
- Unpublished spectra of four B-type members.
Main features
- Small group of blue stars around the blue supergiant BD + 61º 2509, in the Cas OB5 association
- Age unconstrained, but likely between 5 and 10 Ma.
Retrieved as an open cluster in the search of Gaia DR2 data by Cantat-Gaudin et al. (2018). The median parallax is 0.31 milli-arcseconds.
Alicante 4
Primary Reference
Found in 2001, but never published.
Idenpendently identified by Wilton Dias and published as part of his open cluster database, where it is listed as Dias 1.
- No further work was pursued.
Main features
- Small group of blue stars around the early giant LS I +63º 94, in the Cas OB7 association
Retrieved as an open cluster in the search of Gaia DR2 data by Cantat-Gaudin et al. (2018). Marginally separate from the nearby (10′ apart) King 16 in the proper motion plane, seems to have a distinctly larger parallax, although DR3 data will be needed to assess if it is unconnected. The median parallax is 0.37 milli-arcseconds.
Alicante 5
Primary Reference
Characterised and described in “The open cluster Pismis 11 and the very luminous blue supergiant HD 80077: I. Physical parameters of the cluster”, Marco & Negueruela (2009), A&A 493, 79.
- Johnson photometry
- Spectra of a few members
Main features
- Small group of blue stars found to the North of Pismis 11
- WISE images show it to be a star-forming cluster.
- There are bright mid-IR sources associated with the B-rype stars seen in the optical, and a large cloud of warm dust.
- The contrast between the optical and the mid-IR is obvious in the two images. Top is a DSS 3-colour composite. Bottom is a Spitzer composite. The central concentration is well seen in both, but the dark areas in the optical image can be seen as bright dust clouds in the mid-IR.
Quite well defined in the proper motion plane in Gaia DR 2 data, though affected by significant differential reddening. Mean parallax around 0.35.
Alicante 6
Primary Reference
“An obscured cluster associated with the H II region RCW173“, Marco & Negueruela (2011), A&A 534, A114.
- Johnson photometry
- 2MASS photometry
- Spectra of many OB stars in the area.
Coordinates
RA: 18 36 20
Dec: -06 38 50
l: 25.30, b: +0.31
d ~ 3 kpc
SIMBAD: Cl Alicante 6
But note that the position in SIMBAD is significantly offset, very likely due to a confusion induced by Baut et al. (2016), who somehow seem to imply that the cluster that they had “discovered” was not the same one that we had reported five years earlier.
Main features
- Relatively large star-forming region.
- Associated with the infrared bubble N37.
- Likely ionised by the O7 II star A805, which is South of the main shell.
- The young population is extended over a large area, and may be separated in two main clumps, one to the North and one to the South of the area that we studied.
Gaia DR 2 data do not separate well the cluster from the field, but strongly suggest the presence of two main clumps (one inside N37 and the other one around the O7 V star C81) with the same proper motions and reddening. The typical parallax is 0.38 milli-arcseconds, and the unreddened older B-type stars that we investigated seem to be at exactly the same distance.
Alicante 7
Primary Reference
“A massive association around the obscured open cluster RSGC3“, Negueruela et al. (2011), A&A 528, A59.
- 2MASS photometry
- Spectra of red supergiants
Main features
- Cluster candidate in the neighbourhood of the starburst cluster RSGC3.
- Part of a very extended complex close to the spot where the end of the Galactic Bar touches the Scutum-Crux arm.
- This region is subject to very high extinction and only the red supergiants are visible in the optical range, as very faint objects. In the infrared (as in the image), they are extremely bright.
Gaia DR 2 data are not good enough to identify the cluster. However, unpublished spectra of several candidates clearly indicate that this is a real cluster of red supergiants. This is further confirmed by the work of Origlia et al. (2019), who observed 7 RSG members.
Alicante 8
Primary Reference
“Another cluster of red supergiants close to RSGC1“, Negueruela et al. (2010), A&A 513, A74.
- 2MASS photometry
- Spectra of red supergiants
Main features
- Cluster candidate in the neighbourhood of the starburst cluster RSGC1.
- This region is subject to very high extinction and no star is visible in the optical range. In the infrared (as in the image), the RSGs are extremely bright.
This is a very good cluster candidate based on stellar density and photometry, but it should be confirmed with accurate radial velocities.
Alicante 9
Primary Reference
“A massive association around the obscured open cluster RSGC3“, Negueruela et al. (2011), A&A 528, A59.
- 2MASS photometry
- Spectra of red supergiants
Coordinates
RA: 18 44 43
Dec: -03:14:40
l: 29.28, b: +00.01
d ~ 6 kpc
SIMBAD: Not in SIMBAD
Main features
- A second cluster candidate in the neighbourhood of the starburst cluster RSGC3, just North of Alicante 7.
- This region is subject to very high extinction and only the red supergiants are visible in the optical range, as very faint objects. In the infrared (as in the image), they are extremely bright.
There are only three RSGs identified in this area. They share properties and radial velocities. With such a small number, it is difficult to know if this is an open cluster or just an overdensity in the surrounding association. The expected accompanying blue population cannot be separated from the field. We will probably need IR Gaia to know.
Alicante 10
Primary Reference
“A third cluster of red supergiants in the vicinity of the massive cluster RSGC3″, González-Fernández & Negueruela (2012), A&A 539, A100.
- 2MASS photometry
- Spectra of red supergiants
Coordinates
RA: 18 45 15
Dec: -03 41 30
l: 28.94, b: -00.31
d ~ 6 kpc
SIMBAD: Cl Alicante 10
Position in SIMBAD somewhat offset from main concentration of RSGs.
Main features
- A third cluster candidate in the neighbourhood of the starburst cluster RSGC3, this one to the South.
- This region is subject to very high and variable extinction. No stars are visible in the optical range, even the red supergiants. In the infrared (as in the image), they are extremely bright.
Given the high number of RSGs with similar radial velocities, this candidate can be considered almost certainly a cluster. Together with RSGC3 and Alicante 7, it defines a huge association that contains no less than 50 RSGs (see also Origlia et al. 2019).
Alicante 11
Primary Reference
“Open clusters in Auriga OB2“, Marco & Negueruela (2016), MNRAS 459, 880.
- Strömgren photometry
- Spectra of brightest members
Identified and observed in 2003, the results weren’t published until 2016. In the mean time, it was marked as a cluster candidate by Froebrich et al. (2007), under code name FSR 777.
Main features
- A loose cluster in the neighbourhood of the star-forming cluster Stock 8.
- It contains the eclipsing system IU Aur, which is believed to be a complex multiple system with an O-type primary.
Gaia DR2 data confirm that the properties of this population are indistinguishable from those of Stock 8, which is over 20 arcmin away. The parallax for this area, 0.45 milli-arcseconds indicates a rather lower distance than estimated from photometry and spectroscopy, around 2 kpc.
Alicante 12
Primary Reference
“Open clusters in Auriga OB2“, Marco & Negueruela (2016), MNRAS 459, 880.
- Strömgren photometry
- Spectra of brightest members
Identified and observed in 2003, the results weren’t published until 2016. In the mean time, it was marked as a cluster candidate by Kronberger et al. (2006), under the name Kronberger 1.
Main features
- A small concentrated cluster in the neighbourhood of the star-forming cluster Stock 8.
- A little to the East of Alicante 11.
Gaia DR2 data confirm that the properties of this population are indistinguishable from those of Stock 8, which is over 20 arcmin away. The parallax for this area, 0.45 milli-arcseconds indicates a rather lower distance than estimated from photometry and spectroscopy, around 2 kpc.
Alicante 13
Primary Reference
“Cluster membership for the long period Cepheid calibrator SV Vul“, Negueruela et al. (2020) MNRAS 494, 3028.
- Gaia and 2MASS photometry
- Spectra of brightest members
Coordinates
RA: 19 52 11
Dec: +27 46 45
l: 64.01, b: +0.19
d ~ 2.5 kpc
SIMBAD: Not yet in SIMBAD
Main features
- A dispersed cluster in a high-density field, it is difficult to see, except for some superigants (the four bright stars in the image are cluster supergiants).
- Contains the 45 d Cepheid SV Vul (bright star to the right of the field).
In spite of its low contrast, Alicante 13 pops up in the recent automated search for clusters in Gaia DR2 data carried out by Castro-Ginard et al. (2020), where it is given as UBC 130. Although it can hardly be seen, it has a few dozen B-type stars and therefore a mass approaching 1000 solar masses.
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