SPIRITS Catalog of Infrared Variables: Identification of Extremely Luminous Long Period Variables

Karambelkar, Viraj; Adams, S. M.; Whitelock, P. A.; Kasliwal, M. M.; Jencson, J.; Boyer, Martha L.; Goldman, S. R.; Masci, Frank J.; Cody, Ann Marie; Bally, John; Bond, Howard E.; Gehrz, R. D.; Parthasarathy, M.; Lau, Ryan M.

doi:10.3847/1538-4357/ab1a41

Cited by 28 publications

(26 citation statements)

References 91 publications

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“…Nine stars with periods over 1000 days in the MCs were previously reported by Wood et al (1992) and Whitelock et al (2003) based on NIR observations. Recently, Menzies et al (2019) presented a compilation of Miras with periods over 1000 days in the Milky Way (17), SMC (3), and LMC (18), while Karambelkar et al (2019) published a list of 417 luminous IR variables, of which 86 have periods over 1000 days, located in seven galaxies (the majority in M 83 (49 objects), and M 81 (11 objects)). The compilation by Menzies et al (2019) was based on Wood et al (1992) and Whitelock et al (2003), OGLE data in the SMC and LMC (Soszyński et al 2011(Soszyński et al , 2009a, and GS18 (which is partly based on a preliminary analysis of VMC data).…”

Section: Lpvs With Periods Over 1000 Daysmentioning

confidence: 99%

The VMC Survey

Groenewegen

Nanni

Cioni

et al. 2020

A&A

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Context. Variability is a key property of stars on the asymptotic giant branch (AGB). Their pulsation period is related to the luminosity and mass-loss rate of the star. Long-period variables (LPVs) and Mira variables are the most prominent of all types of variability of evolved stars. The reddest, most obscured AGB stars are too faint in the optical and have eluded large variability surveys. Aims. We obtained a sample of LPVs by analysing K-band light curves (LCs) of a large number of sources in the direction of the Magellanic Clouds with the colours expected for red AGB stars ((J − K) > 3 mag or equivalent in other colour combinations). Methods. Selection criteria were derived based on colour-colour and colour-magnitude diagrams from the combination of the VISTA Magellanic Cloud (VMC) survey, Spitzer IRAC and AllWISE data. After eliminating LPVs with known periods shorter than 450 days, a sample of 1299 candidate obscured AGB stars was selected. K-band LCs were constructed by combining the epoch photometry available in the VMC survey with literature data, were analysed for variability, and fitted with a single period sine curve to derive mean magnitudes, amplitudes, and periods. A subset of 254 stars are either new variables, known variables where the period we find is better determined than the literature value, or variables with periods longer than 1000 days. The spectral energy distributions (SEDs) of these stars were fitted to a large number of templates. For this purpose the SEDs and Spitzer IRS spectra of some non-AGB stars (Be stars, HII regions and young stellar objects – YSOs) were also fitted to have templates of the most likely contaminants in the sample. Results. A sample of 217 likely LPVs is found. Thirty-four stars have periods longer than 1000 days, although some of them have alternative shorter periods. The longest period of a known Mira in the Magellanic Clouds from Optical Gravitational Lensing Experiment data (with P = 1810 d) is derived to have a period of 2075 d based on its infrared LC. Two stars are found to have longer periods, but both have lower luminosities and smaller pulsation amplitudes than expected for Miras. Mass-loss rates and luminosities are estimated from the template fitting. Period-luminosity relations are presented for carbon (C-) and oxygen (O-) rich Miras that appear to be extensions of relations derived in the literature for shorter periods. The fit for the C stars is particularly well defined (with 182 objects) and reads Mbol = (−2.27 ± 0.20) ⋅ log P + (1.45 ± 0.54) mag with an rms of 0.41 mag. Thirty-four stars show pulsation properties typical of Miras while the SEDs indicate that they are not. Overall, the results of the LC fitting are presented for over 200 stars that are associated with YSOs.

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Section: Lpvs With Periods Over 1000 Daysmentioning

confidence: 99%

The VMC Survey

Groenewegen

Nanni

Cioni

et al. 2020

A&A

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“…In this paper, we present mid-IR light curves of six extragalactic dust-forming WC candidates identified from Spitzer /IRAC 3.6 and 4.5 µm imaging observations in the SPitzer InfraRed Intensive Transients Survey (SPIR-ITS; Kasliwal et al 2017;Karambelkar et al 2019). One of these candidates includes the recently discovered WC+O colliding-wind binary candidate in M33, N604-WRXc (Garofali et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Revealing Efficient Dust Formation at Low Metallicity in Extragalactic Carbon-rich Wolf-Rayet Binaries

Lau¹,

Hankins

Kasliwal

et al. 2021

ApJ

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We present Spitzer /IRAC observations of dust formation from six extragalactic carbon-rich Wolf-Rayet (WC) binary candidates in low-metallicity (Z 0.65 Z ) environments using multi-epoch midinfrared (IR) imaging data from the SPitzer InfraRed Intensive Transients Survey (SPIRITS). Optical follow-up spectroscopy of SPIRITS 16ln, 19q, 16df, 18hb, and 14apu reveals emission features from C iv λ5801-12 and/or the C iii-iv λ4650/He ii λ4686 blend that are consistent with early-type WC stars. We identify SPIRITS 16ln as the variable mid-IR counterpart of the recently discovered colliding-wind WC4+O binary candidate, N604-WRXc, located in the sub-solar metallicity NGC 604 H ii region in M33. We interpret the mid-IR variability from SPIRITS 16ln as a dust-formation episode in an eccentric colliding-wind WC binary. SPIRITS 19q, 16df, 14apu, and 18hb exhibit absolute [3.6] magnitudes exceeding one of most IR-luminous dust-forming WC systems known, WR 104 (M [3.6] −12.3). An analysis of dust formation in the mid-IR outburst from SPIRITS 19q reveals a high dust production rate ofṀ d 2×10 −6 M yr −1 , which may therefore exceed that of the most efficient dust-forming WC systems known. We demonstrate that efficient dust-formation is feasible from early-type WC binaries in the theoretical framework of colliding-wind binary dust formation if the systems host an O-type companion with a high mass-loss rate (Ṁ 1.6 × 10 −6 M yr −1 ). This efficient dust-formation from early-type WC binaries highlights their potential role as significant sources of dust in low-metallicity environments.

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“…Due to sensitivity and the time sampling of our observations, our variability search is biased towards discovering large-amplitude LPVs (Boyer et al 2015b). Infrared-bright populations such as thermally pulsing (TP)-AGB stars are variable on time-scales of 60 to 1000 d (Vassiliadis & Wood 1993), with amplitudes up to 2 mag at 3.6 μm (Le Bertre 1992Bertre , 1993McQuinn et al 2007;Vijh et al 2009;Polsdofer et al 2015;Goldman et al 2019;Karambelkar et al 2019). In contrast Cepheid variables or RR Lyrae stars, which have shorter periods (typically between 1 and 80 d), are not expected to be recovered as their light curves are not favourably sampled by our survey.…”

Section: Variability Searchmentioning

confidence: 98%

“…Previous Spitzer variability studies of Local Group galaxies have obtained between two and eight epochs of imaging, and were able to identify a large population of dust-producing AGB star candidates with 3.6 μm amplitudes up to 2.0 mag (Le Bertre 1992;McQuinn et al 2007;Vijh et al 2009;Riebel et al 2010;Boyer et al 2015b;Polsdofer et al 2015;Goldman et al 2019;Karambelkar et al 2019). In this paper, we investigate for the first time in the midinfrared (IR) the variable stellar population of the compact elliptical galaxy M32 with Spitzer.…”

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confidence: 98%

Infrared variable stars in the compact elliptical galaxy M32

Jones

Nally

Sharp

et al. 2021

Monthly Notices of the Royal Astronomical Society

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Variable stars in the compact elliptical galaxy M32 are identified, using three epochs of photometry from the Spitzer Space Telescope at 3.6 and 4.5 μm, separated by 32 to 381 days. We present a high-fidelity catalogue of sources detected in multiple epochs at both 3.6 and 4.5 μm, which we analysed for stellar variability using a joint probability error-weighted flux difference. Of these, 83 stars are identified as candidate large-amplitude, long-period variables, with 28 considered high-confidence variables. The majority of the variable stars are classified as asymptotic giant branch star candidates using colour-magnitude diagrams. We find no evidence supporting a younger, infrared-bright stellar population in our M32 field.

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SPIRITS Catalog of Infrared Variables: Identification of Extremely Luminous Long Period Variables

Cited by 28 publications

References 91 publications

The VMC Survey

The VMC Survey

Revealing Efficient Dust Formation at Low Metallicity in Extragalactic Carbon-rich Wolf-Rayet Binaries

Infrared variable stars in the compact elliptical galaxy M32

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