Optical photometry of GM Cep: evidence for UXor type of variability

Semkov, E.; Peneva, S.

doi:10.1007/s10509-011-0900-x

Cited by 14 publications

(24 citation statements)

References 21 publications

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“…min. field, 8.5 e − rms RON) As references, we used the comparison sequence of fifteen stars in the field around GM Cep published in Semkov & Peneva (2012).…”

Section: Observationsmentioning

confidence: 99%

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The Unusual Photometric Variability of the PMS Star GM Cep

Semkov

Ibryamov

Peneva

et al. 2015

Publ. Astron. Soc. Aust.

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Results from UBV RI photometric observations of the pre-main sequence star GM Cep obtained in the period 2011 April-2014 August are reported in the paper. Presented data are a continuation of our photometric monitoring of the star started in 2008. GM Cep is located in the field of the young open cluster Trumpler 37 and over the past years it has been an object of intense photometric and spectral studies. The star shows a strong photometric variability interpreted as a possible outburst from EXor type in previous studies. Our photometric data for a period of over six years show a large amplitude variability ( V ∼ 2.3 mag) and several deep minimums in brightness are observed. The analysis of the collected multicolour photometric data show the typical of UX Ori variables a colour reversal during the minimums in brightness. The observed decreases in brightness have a different shape, and evidences of periodicity are not detected. At the same time, high amplitude rapid variations in brightness typical for the classical T Tauri stars also present on the light curve of GM Cep. The spectrum of GM Cep shows the typical of classical T Tauri stars wide Hα emission line and absorption lines of some metals. We calculate the outer radius of the Hα emitting region as 10.4±0.5 R and the accretion rate as 1.8×10−7 M yr −1 .

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“…min. field, 8.5 e − rms RON) As references, we used the comparison sequence of fifteen stars in the field around GM Cep published in Semkov & Peneva (2012).…”

Section: Observationsmentioning

confidence: 99%

“…The unusual photometric variability of the PMS star GM Cep 3 (Semkov & Peneva 2012). In addition, we present in Table 2 data from observations in U filter for the whole period of our photometric monitoring (2008 -2014).…”

Section: Observationsmentioning

confidence: 99%

The Unusual Photometric Variability of the PMS Star GM Cep

Semkov

Ibryamov

Peneva

et al. 2015

Publ. Astron. Soc. Aust.

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“…As demonstrated herein, time-variable extinction is clearly an important part of the PTF 10nvg interpretation, and may also play a significant role in the observed photometric behavior of many of the so-called outburst light curves highlighted to date in the literature. For example, GM Cep was discussed by SiciliaAguilar et al (2008) as an EX Lup-type object, but later assessed by Xiao et al (2010), Semkov & Peneva (2012), and Chen et al (2012) as having extinction-dominated rather than accretiondominated time-series behavior. Both phenomena are perhaps simultaneously relevant, as we argue here for PTF 10nvg.…”

Section: Introductionmentioning

confidence: 99%

HIGHLY VARIABLE EXTINCTION AND ACCRETION IN THE JET-DRIVING CLASS I-TYPE YOUNG STAR PTF 10nvg (V2492 Cyg, IRAS 20496+4354)

Hillenbrand

Miller

Covey

et al. 2013

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We report extensive new photometry and spectroscopy of the highly variable young stellar object PTF 10nvg (also known as IRAS 20496+4354 and V2492 Cyg), including optical and near-infrared time-series data as well as mid-infrared and millimeter data. Following the previously reported 2010 rise to R PTF 13 m . 5 and subsequent fade, during 2011 and 2012 the source underwent additional episodes of brightening, followed by several magnitude dimming events including prolonged faint states at R PTF 20 m . The observed high-amplitude variations are largely consistent with extinction changes (ΔA V up to 30 mag) having a ∼220 day quasi-periodic signal. However, photometry measured when the source was near maximum brightness in mid-2010 as well as in late-2012 does not phase well to this period. Spectral evolution includes not only changes in the spectral slope but also correlated variation in the prominence of TiO/VO/CO bands and atomic line emission, as well as anti-correlated variation in forbidden line emission which, along with H 2 , dominates optical and infrared spectra at faint epochs. Notably, nightto-night variations in several forbidden doublet strengths and ratios are observed. High-dispersion spectra were obtained in a variety of photometric states and reveal time-variable line profiles. Neutral and singly ionized atomic species are likely formed in an accretion flow and/or impact while the origin of zero-velocity atomic Li i λ6707 in emission is unknown. Forbidden lines, including several rare species, exhibit blueshifted emission profiles and likely arise from an outflow/jet. Several of these lines are also seen spatially offset from the continuum source position, presumably in a shocked region of an extended jet. Blueshifted absorption components of the Na i D doublet, K i λλ7665, 7669 doublet, and the O i 7774 triplet, as well as blueshifted absorption components seen against the broad Hα and Ca ii triplet emission lines, similarly are formed in the outflow. CARMA maps resolve on larger scales a spatially extended outflow in millimeter-wavelength CO. We attribute the recently observed photometric and spectroscopic behavior to rotating circumstellar disk material located at separation a ≈ 0.7(M * /M ) 1/3 AU from the continuum source, causing the semi-periodic dimming. Occultation of the central star as well as the bright inner disk and the accretion/outflow zones renders shocked gas in the inner part of the jet amenable to observation at the faint epochs. We discuss PTF 10nvg as a source exhibiting both accretion-driven (perhaps analogous to V1647 Ori) and extinction-driven (perhaps analogous to UX Ori or GM Cep) high-amplitude variability phenomena.

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“…Figure 1b). Since last reported (Chen et al 2012;Semkov & Peneva 2012;Semkov et al 2015), the star continued to show abrupt brightness changes. There are three main kinds of variations.…”

Section: Optical Polarimetrymentioning

confidence: 89%

Diagnosing the Clumpy Protoplanetary Disk of the UXor Type Young Star GM Cephei

Huang

Chen

Mugrauer

et al. 2019

ApJ

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UX Orionis stars (UXors) are Herbig Ae/Be or T Tauri stars exhibiting sporadic occultation of stellar light by circumstellar dust. GM Cephei is such a UXor in the young (∼ 4 Myr) open cluster Trumpler 37, showing prominent infrared excess, emission-line spectra, and flare activity. Our photometric monitoring (2008-2018) detects (1) an ∼3.43 day period, likely arising from rotational modulation by surface starspots, (2) sporadic brightening on time scales of days due to accretion, (3) irregular minor flux drops due to circumstellar dust extinction, and (4) major flux drops, each lasting for a couple of months with a recurrence time, though not exactly periodic, of about two years. The star experiences normal reddening by large grains, i.e., redder when dimmer, but exhibits an unusual "blueing" phenomenon in that the star turns blue near brightness minima. The maximum extinction during relatively short (lasting ≤ 50 days) events, is proportional to the duration, a consequence of varying clump Huang et al.sizes. For longer events, the extinction is independent of duration, suggestive of a transverse string distribution of clumps. Polarization monitoring indicates an optical polarization varying ∼ 3%-8%, with the level anticorrelated with the slow brightness change. Temporal variation of the unpolarized and polarized light sets constraints on the size and orbital distance of the circumstellar clumps in the interplay with the young star and scattering envelope. These transiting clumps are edge-on manifestations of the ring-or spiral-like structures found recently in young stars with imaging in infrared of scattered light, or in submillimeter of thermalized dust emission.

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Optical photometry of GM Cep: evidence for UXor type of variability

Cited by 14 publications

References 21 publications

The Unusual Photometric Variability of the PMS Star GM Cep

The Unusual Photometric Variability of the PMS Star GM Cep

HIGHLY VARIABLE EXTINCTION AND ACCRETION IN THE JET-DRIVING CLASS I-TYPE YOUNG STAR PTF 10nvg (V2492 Cyg, IRAS 20496+4354)

Diagnosing the Clumpy Protoplanetary Disk of the UXor Type Young Star GM Cephei

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