Stars and brown dwarfs in the σ Orionis cluster - III. OSIRIS/GTC low-resolution spectroscopy of variable sources

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Table 2

Known data of sources in σ Orionis.

Name	Phot.	X-ray	Spectral	EW(Hα)	EW(Li i)	V_r
	variability	variability	type	[Å]	[mÅ]	[km s^-1]

Mayrit 783254	...	Flare (Ca09)	K0 (Wo96)	+0.521 (Wo96)	+0.417 (Wo96)	...
Mayrit 528005 AB	Mid-term (Ca10b)	...	K7.0 (ZO02)^a	–4.3 ± 0.3 (Ca06)^a	+470 ± 20 (Ca06)^a	+30.7 ± 0.4 (GH08)
Mayrit 609206	Mid-term (Fe60)^b	...	K7.0e (ZO02)	–25.11 ± 0.72 (Sa08)^b	+431 ± 11 (Sa08)	+30.00 ± 0.49 (Sa08)
Mayrit 957055	...	Long-term (Ca10a)	...	...	...	...
Mayrit 180277	Mid-term (CH10)	Flare (Ca10a)	K8.5: (Sa08)	–1.46 ± 0.17 (Sa08)	+576 ± 6 (Sa08)	+30.12 ± 0.17 (Sa08)
Mayrit 156353	...	Flare (Fr06)^c	M1.0: (Sa08)	–3.59 ± 0.29 (Sa08)	+620 ± 23 (Sa08)	+31.63 ± 0.33 (Sa08)
Mayrit 662301	...	Flare (Fr06)	...	Variable (Wi89)^d	...	...
Mayrit 1298302	...	Flare (LC08)	...	Emission? (Ca06)^e	Absorption? (Ca06)^e	...
Mayrit 872139	Pulsation? (Ca04)^f	...	...	...	+660 ± 90 (Ke05)	+24.84 ± 0.53 (Ma08)
Mayrit 1196092	Short-term (Ca04)^g	...	...	Broad (Ke05)	+390: (Ke05)	+31.45 ± 0.47 (Ma08)

Notes.

^(a)

For Mayrit 528005 AB, Zapatero Osorio et al. (2002) had previously measured EW(Hα) = –3.1 ± 0.5 Å and EW(Li i) = +480 ± 70 mÅ, while Wolk (1996) had estimated a K3 spectral type.

^(b)

For Mayrit 609206, Cody & Hillenbrand (2010, 2011) also found aperiodic photometric variability in the optical and near-infrared, while Zapatero Osorio et al. (2002) and Caballero (2006) had previously measured EW(Hα) = −53.5 ± 9.0 and –32 ± 3 Å, respectively.

^(c)

For Mayrit 156353, Caballero et al. (2009, 2010a) also found X-ray flaring activity.

^(d)

Wiramihardja et al. (1989) tabulated different estimated Hα emission intensities of Mayrit 662301 at three epochs: medium, very weak, and absent or doubtful.

^(e)

The AF2+WYFFOS/4.2 m William Herschel Telescope spectrum of Mayrit 1298302 in Caballero (2006) was very noisy.

^(f)

For Mayrit 872139, Cody & Hillenbrand (2010) did not re-detect variability in their data; any signal would be below 0.004 mag at periods shorter than 8 h and ~0.01 mag for longer timescales of up to two weeks.

^(g)

For Mayrit 1196092, Cody & Hillenbrand (2010) determined a period P = 0.76 ± 0.01 d with A_I = 0.027 ± 0.010 mag.

References. Reference acronyms in parenthesis – Fe60: Fedorovich (1960); ZO02: Zapatero Osorio et al. (2002); Wi89: Wiramihardja et al. (1989); Wo96: Wolk (1996); Ca04: Caballero et al. (2004); Ke05: Kenyon et al. (2005); Ca06: Caballero (2006); Fr06: Franciosini et al. (2006); GH08: González Hernández et al. (2008); LC08: López-Santiago & Caballero (2008); Ma08: Maxted et al. (2008); Sa08: Sacco et al. (2008); Ca09: Caballero et al. (2009); Ca10a: Caballero et al. (2010a); CH10: Cody & Hillenbrand (2010); Ca10b: Caballero et al. (2010b).

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